Supercritical Fluids Research Papersin AIChE 2000 Annual Meeting

http://www.aiche.org/conferences/techprogram/

[16d] - Synthesis and Crystallization of Mixed Oxide Nanoparticles in Near-Critical Water

Linda J. Holm (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-7615Fax: 404-894-2866 Email: gt5517a@prism.gatech.edu

Amyn S. Teja Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-3098Email: amyn.teja@che.gatech.edu

Abstract: The synthesis of mixed metal oxide nanoparticles with well-defined morphology and composition is of scientific and technological interest because such particles have potential applications in high-density information storage devices and in targeted drug delivery. We have studied the synthesis and crystallization of spinel iron oxides by the following reaction:

2Fe(NO3)3 + M(NO3)2 + 8NaOH → MFe2O4 + 8NaNO3 + 4H2O

where M2+ can be a number of divalent cations such as Mn, Co, Fe, Cd or Mg. The reaction was carried out in near-critical water, which provided the opportunity to manipulate solvating power through temperature and pressure changes, and by the addition of cosolvents.

In addition, the formation of particles was studied in a flow apparatus, which allowed us to decouple the particle formation and growth processes. Although nanoparticles of single metal oxides have been successfully produced, the production of mixed oxide particles has proved to be a formidable challenge. This is because the kinetics of the intermediate hydrolysis and dehydration reactions at elevated temperature and pressure do not necessarily lead to a thermodynamically favored mixed oxide product. We have found that the solubility of the (intermediate) hydroxides influences the composition of the product and have therefore examined several methods for the estimation of ionic species in the near-critical water environment. An understanding of the role played by solubility of the various metal species has also allowed us to tailor processing conditions to obtain a final product of the desired morphology and composition.

[40] - SCF for Pollution PreventionChair:Esin GulariWayne State UniversityDepartment of Chemical EngineeringDetroit, MI 48202Telephone Number: 313-577-3767Fax Number: 313-577-3810Email: egulari@che.eng.wayne.edu

Vice Chair:Bill TumasLos Alamos National LaboratoryCST-18, Chemical & Environmental R&DLos Alamos, NM 87545Telephone Number: 505-667-3803Fax Number: 505-667-9905Email: tumas@lanl.gov

[40a] - Deposition of Conformal Gold Films from Supercritical Carbon Dioxide

David P. Long (speaker) University of Massachusetts 142 Goessmann Lab Amherst, MA 01002 Phone: (413) 577-1090Fax: (413) 545-1647 Email: dlong@chemistry.umass.edu

James Watkins University of Massachusetts Department of ChemicalEngineering Amherst, MA 01003 Phone: 413-545-2569Fax: 413-545-1647 Email: watkins@ecs.umass.edu

Abstract: Chemical fluid deposition (CFD) is a novel method for low temperature metallization of inorganic and polymer substrates that involves the chemical reduction of organometallic compounds dissolved in supercritical carbon dioxide. To date we have demonstrated the deposition of high-purity films of Pt, Pd, Ni, Rh and their alloys. Here we will discuss the environmentally benign deposition of pure, highly reflective gold films via hydrogen reduction of dimethyl(acetylacetonate)gold(III), [(acac)Au(CH3)2], in supercritical carbon dioxide at 60 - 80 oC. The films were analyzed by x-ray photoelectron spectroscopy (XPS), wide-angle x-ray diffraction, and field-emission scanning electron microscopy (FE-SEM). XPS confirms that the films are pure with no ligand derived carbon or oxygen contamination. Cross-sectional FE-SEM reveals the films range from 100 - 500 nm in thickness and are highly conformal to the surface topography of the substrate. Deposition of 100 to 120 nm gold films on patterned silicon is completely conformal to the etched vias with complete trench filling being achieved in the smallest features (100 nm wide) with aspect ratios of 10. Analysis of the CO2 effluent stream derived from these batch depositions by1H NMR spectroscopy reveals that ethane and 2,4-pentanedione are the only major ligand products. The deposition process is highly selective for metal substrates over non-growth surfaces such as polymers or the native oxide layer of glass or silicon. Efficient deposition of conformal gold films can, however, be induced on these surfaces by first depositing thin seed layers of metals from the nickel group.

[40b] - Supercritical CO2 for Product Recovery from Ionic Liquids

Lynnette A. Blanchard University of Notre Dame Dept. of Chemical Engineering Notre Dame, IN 46556 Phone: (219) 631-5848Fax: (219) 631-8366 Email: lblancha@nd.edu

Joan F. Brennecke (speaker) University of Notre Dame 182 Fitzpatrick Hall Notre Dame, IN 46556 Phone: 219-631-5847Fax: 219-631-8366 Email: jfb@nd.edu

Eric J. Beckman University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-9631

Abstract: Ionic liquids are organic salts that are liquids at temperatures around ambient. They are typically made up of an imidazolium or pyridinium cation with any of a variety of anions (e.g., Cl-, PF6-, BF4-, NO3-). Their most attractive feature is that they have extremely low vapor pressures even though they are liquids. As a result, they have received tremendous attention as possible solvents to replace common volatile organic solvents, especially for use in reactions. In fact, numerous researchers have shown that ionic liquids can be used as solvents for a wide variety of industrially important reactions, producing yields and selectivities as good or greater than in common solvents. However, the development of environmentally benign methods to remove low volatility or thermally labile reaction products from the ionic liquids remains a challenge. To address this problem, we have previously suggested the use of supercritical CO2to extract solutes from ionic liquids (Blanchard et al., Nature, 399, 1999, 28-29). In particular, we have shown that supercritical CO2 can be used to extract naphthalene from 1-butyl-3-methyl imidazolium hexafluorophosphate [bmim][PF6]. Here, we report on investigations of the generality of this technique for extraction from different ionic liquids and for different solutes. First, we present the phase behavior of CO2 with 1- n-octyl-3-methylimidazolium hexafluorophosphate [C8mim][PF6], 1- n-octyl-3-methylimidazolium tetrafluoroborate [C8mim][BF4], 1- n-butyl-3-methyl-imidazolium nitrate [bmim][NO3], 1-ethyl-3-methylimidazolium ethylsulfate [emim][EtSO4], and N-butylpyridinium tetrafluoroborate [Nbupy][BF4]. We find that all of the ionic liquids are immiscible with CO2, although significant amounts of CO2 dissolve in them. There is some influence on the degree of CO2 dissolution of both the molar volume of the ionic liquid and the nature of the anion. These results suggest that CO2 is a viable environmentally benign solvent to extract solutes from all of the different ionic liquids tested. Second, we have measured the solubility of a variety of solid and liquid solutes in [bmim][PF6]. The solutes include alkyl and benzyl compounds containing various functional groups (e.g., alcohols, ketones, amines). In addition, we have investigated the extraction of these compounds from [bmim][PF6] with supercritical CO2 at 40℃ and 2000 psi. These results are important in identifying opportunities for reaction/separation systems where volatile organic solvents might be replaced by combined ionic liquid/supercritical CO2 systems to prevent atmospheric pollution.

[40c] - Surfactant/Supercritical Fluid Systems for Metal Surface Cleaning

Tameka S. Spence (speaker) North Carolina A&T State University 1601 E. Market St. Greensboro, NC 27411 Phone: 336-334-7564Email: ts989546@ncat.edu

Keith B. Saunders North Carolina A&T State University1601 E Market St Greensboro, NC 27411 Phone: 336-334-7564

Kenneth L. Roberts North Carolina A&T State University 1601 East Market Street Greensboro, NC 27411 Phone: 336-334-7564Fax: 336-334-7904 Email: kroberts@ncat.edu

Gary L. White North Carolina A&T State University1601 E Market St Greensboro, NC 27411 Phone: 336-334-7564

Abstract: Methods for the cleaning of metal surfaces, surfactant/supercritical fluid and supercritical fluid cleaning, are discussed in this work. This process could conceivably replace solvent-based methods, which utilize EPA-regulated chlorofluorocarbons (CFC뭩) and halogenated hydrocarbon solvents for the degreasing and cleaning precision metal parts. This method involves the use of a supercritical fluid or a reverse micellular solution in a supercritical light hydrocarbon or carbon dioxide to clean industrial wastes from coupons of metal for machining operations. A reverse micellar solution, which contains water dissolved into a non-polar solvent with the aid of a surfactant, is capable of dissolving both water-soluble and oil-soluble contaminants. Once the contaminants have been dissolved into solution, they can be separated from the supercritical fluid and later recycled back to the process.

The removal of a model grease contaminant at fixed conditions was examined for the Aerosol OT (AOT)/ethane/water and supercritical carbon dioxide systems in this work at 37 oC and pressures from 2000 to 3500 psig. The AOT/ethane system was observed to exhibit significantly higher removal efficiencies than the CO2 system. Overall the removal of the grease contaminant was observed to increase with pressure for both systems. The effects of additional polar, ionic and oily model contaminants on removal efficiency were also determined for the Aerosol OT/ethane and carbon dioxide systems.

The effects of the contaminant type and composition on cleaning effectiveness for the AOT/ethane and carbon dioxide systems were observed to noticeably influence grease removal efficiency. In many cases the removal efficiency in the contaminant-containing AOT/ethane systems followed trends predicted in earlier work from this group which determined the water solubility in the AOT/ethane system. The removal efficiency appears to increase with water dissolution for the AOT/ethane system.

[40d] - Removal of Polymer Coatings with Supercritical Fluids

Laurie L. Williams (speaker) Colorado State University PO Box 362 Los Alamos, NM 87544 Phone: 505 667-3706Fax: 505 667-6561 Email: williams@lanl.gov

James B. Rubin Los Alamos National Laboratory PO Box 1663 Los Alamos, NM 87545 Phone: 505 667-3294

Harry W. Edwards Colorado State University Department of Mechanical Engineering Fort Collins, CO 80523 Phone: 970 491-5317

Abstract: Numerous environmental regulations, and the wide range of concerns pertaining to environmental release paths, is leading industries to seek non-hazardous, low-discharge coatings removal technologies. Supercritical fluids are used as solvent in many commercial applications, including the extraction of caffeine from coffee and essential oil and spices from plants for use in perfumes and foods. Supercritical fluids, especially carbon dioxide, as an alternative coatings removal technology has tremendous potential as they offer many advantages over conventional organic solvents and are non-harmful to most substrate surfaces. The advantages to utilizing supercritical CO2 include low human toxicity, general chemical inertness, noncombustibility, natural occurrence, low cost, ready availability, and environmental acceptability (no ozone depletion). By definition, a fluid (liquid or gas) that has been brought to conditions above its critical temperature and pressure is known as a supercritical fluid. This paper will describe the general properties of supercritical fluids, with particular emphasis on their application of as alternative solvents. To exploit the use of supercritical fluids in the removal of coatings and in extraction technologies, it is important to understand their properties and how supercritical fluids interact with materials. This paper will discuss the interactions between a supercritical fluid, carbon dioxide in particular, and polymers and then focus attention on the specific interactions which are brought to bear when a polymeric coating is to be removed or involved in an extraction operation. A semi quantitative model will be presented which incorporates the physical properties of carbon dioxide with polymer characteristics; functional groups, solubility parameters, acid-base intra- and interactions, and surface tension, to predict the polymer/supercritical fluid interaction. In addition, the use of cosolvents will be discussed which enhance the likelihood of desired interactions.

[40e] - Catalytic Oxidation of Organic Substrates with Transition Metal Complexes in Organic Solvents Expanded by Dense Carbon Dioxide

Ming Wei (speaker) University of Kansas Department of Chemical andPetroleum Engineering, Learned Hall 4006 Lawrence, KS 66044 Phone: (785) 864 2921Fax: (785) 864 4967 Email: mwei@cpe.engr.ukans.edu

Ghezai T. Musie University of Kansas Chemistry Departments Lawrence, KS 66045 Phone: (785) 864 2921Fax: (785) 864 4967 Email: gmuise@eagle.cc.ukans.edu

Bala Subramaniam University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785-864-2903Fax: 785-864-4967 Email: bsubramaniam@ukans.edu

Daryle H. Busch University of Kansas Chemistry Department Lawrence, KS 66045 Phone: (785)864-5172Fax: 864-5747 Email: dbusch@caco3.chem.ukans.edu

Abstract: Several homogeneous catalytic oxidations have been reported in environmentally benign supercritical CO2 (scCO2). However, the scCO2-based oxidation process has drawbacks including low reaction rates, high process pressure (in the order of hundreds of bars) and only a limited number of transition metal catalysts that exhibit adequate solubility in unmodified scCO2 for performing the reaction in a homogeneous phase. We present a new process in which the solvent is substantially (but not totally) replaced by scCO2 and dense CO2. We call this CO2-expanded solvent medium. The organic solvent may be volumetrically expanded several-fold by scCO2 while maintaining the solubility of the substrate, solvent and catalyst. The homogenous catalytic oxidation of olefins by iron complexes in various CO2-expanded organic solvents will be presented. Our experimental data show that CO2-expanded solvents are unique reaction media for catalytic oxidation. The benefits of this novel process relative to scCO2-based and conventional processes will be demonstrated.

[40f] - Phase-Separable Catalysis Approaches Using Dense Phase Carbon Dioxide

Bill Tumas (speaker) Los Alamos National Laboratory CST-18, Chemical & Environmental R&DLos Alamos, NM 87545 Phone: 505-667-3803Fax: 505-667-9905 Email: tumas@lanl.gov

Abstract: Biphasic or phase-separable catalysis combines the selectivity and catalyst/ligand design advantages of homogeneous catalysis with the product recovery and catalyst recycle advantages of heterogeneous catalysis. We will report on several concepts that use dense phase liquid or supercritical carbon dioxide as a reaction medium for phase-separable catalysis. Reactants and products are dissolved in a liquid phase and transition metal catalysts are immobilized in another phase, either liquid (primarily water or a room temperature ionic liquid), polymeric or inorganic support. The use of dense phase carbon dioxide allows for unprecedented control of phase behavior, solubility (of catalysts, ligands and polymeric supports), and mass transfer through simple changes in reaction conditions (i.e. pressure, temperature). We have found that these systems can lead to enhanced separations, reactivity and, in some cases, selectivity relative to conventional organic solvents. For example, we have found the reaction rates for biphasic hydrogenation using using water soluble rhodium-phosphine are significantly higher in CO2/water emulsions than in simple two-phase CO2/water or toluene/water mixtures. These emulsions, which are formed by a number of CO2-philic surfactants, can be broken to enable separation by simple changes in pressure or temperature. We have also been investigating ionic liquids as an alternative liquid phase for immobilizing homogeneous transition metal catalysts. We will also report on fluorinated copolymers that are soluble or swellable in carbon dioxide and are modified with ligands that bind transition metal catalysts.

[40g] - CO2-Facilitated Impregnation of Aqueous Latexes

Matthew Z. Yates (speaker) Los Alamos National Laboratory Mail Stop J514 Los Alamos, NM 87545 Phone: 505-667-2658Fax: 505-667-9905

Email: myates@lanl.gov

Eva R. Birnbaum Los Alamos National Laboratory Mail Stop E518 Los Alamos, NM 87545 Phone: 505-667-7538

T. Mark McCleskey Los Alamos National Laboratory Mail Stop J514 Los Alamos, NM 87545 Phone: 505-667-5636

Abstract: A new procedure is described for impregnating aqueous latex particles with additives in which carbon dioxide is used to facilitate mass transport into the particle phase. The process is demonstrated with the impregnation of colloidal polystyrene particles with azobenzene dyes. Monodisperse polystyrene particles with surface-grafted poly(N-vinyl pyrrolidone) were synthesized through dispersion polymerization. Aqueous polystyrene latexes were then dyed with the aid of liquid carbon dioxide to swell and plasticize the particles. Swelling by carbon dioxide causes the polymer to become more fluid and thus increases the rate of diffusion inside the particle. The transfer of dye into the polymer particles is greatly enhanced when the CO2/water interfacial area is increased through emulsification. Dyed polystyrene particles with monodisperse diameters have been produced at room temperature without volatile organic solvents. Even though the particles are highly plasticized during the dyeing process, no agglomeration or coalescence of the particles was observed. Colored microparticles with monodisperse diameters are used in a wide variety of applications including xerography and cell labeling in biological studies. A discussion will be made on the possibility of extending this technique to impregnate latex particles with other compounds such as drugs or reagents for controlled release.

[40h] - Critical Review of Kinetic Data for the Oxidation of Methanol in Supercritical Water

Frederic Vogel (speaker) MIT 1 Amherst Street Cambridge, MA 02139 Phone: (617) 253-0070Email: frederic.vogel@psi.ch

Joanna L. DiNaro MIT 77 Massachusetts Ave. Cambridge, MA 02139 Phone: (617) 253-0070

Philip A. Marrone Arthur D. Little, Inc. 15W-211 Acorn Park Cambridge, MA 02140 Phone: (617) 498-5316Fax: (617) 498-7221 Email: marrone.philip@adlittle.com

Steven F. Rice Sandia National Laboratories P.O. Box 969 Livermore, CA 94551 Phone: (510) 294-1004Email: sfrice@sandia.gov

William A. Peters MIT 1 Amherst Street Cambridge, MA 02139 Phone: (617) 253-3400Email: peters@mit.edu

Jefferson Tester MIT 1 Amherst Street Room E40-455 Cambridge, MA 02139-4307 Phone: 617-253-3401Fax: 617-253-8013 Email: tester@mit.edu

Abstract: Supercritical water oxidation (SCWO) can mineralize or decontaminate a wide range of industrial and military hazardous organic wastes including dilute aqueous streams from chemicals manufacture. To enable or improve reactor design and simulation there is need to quantify the kinetics of waste reactions in SCW with and without the presence of exogenous oxidants. Experimental and modeling studies have examined pure compounds and complex mixtures including simulants for hazardous wastes.

Methanol SCWO kinetics have been extensively studied at MIT, Sandia National Laboratories (SNL) and elsewhere. This paper reports on collaborative MIT-SNL research to reconcile discrepancies in earlier methanol SCWO kinetics results. Prior research

is briefly reviewed and pitfalls in bench scale experimental techniques that may give rise to disparities in kinetics results are discussed, e.g., effects of physical transport, reactor surfaces and materials of construction, type of oxidant, and temperature measurement. The strengths and limitations of various engineering kinetics models in describing rates and extents of SCWO ofmethanol over significant ranges of reactor temperature, residence time, and initial (inlet) oxidant/methanol ratio will be illustrated. These models include single first-order Arrhenius kinetics, distributed activation energy kinetics, and a modified single-reaction model that corrects for inlet stoichiometry. The talk will conclude with practical recommendations for obtaining consistent SCWO kinetics information using different experimental methods.

[40i] - Sodium-Carbonate Microparticle Assisted Supercritical-Water Oxidation of Waste containing Heteroatoms

Poongunran Muthukumaran (speaker) Auburn University 230 Ross Hall Auburn, AL 36832 Phone: 334-844-2001Fax: 334-844-2063 Email: muthupo@eng.auburn.edu

Ram Gupta Auburn University Chemical Engineering Department 230 Ross Hall Auburn, AL 36849-5127 Phone: 334-844-2013Fax: 334-844-2063 Email: gupta@eng.auburn.edu

Abstract: Supercritical water oxidation (SCWO) is emerging as a promising technology for the destruction of organic wastes. However, corrosion is a severe problem for wastes containing heterogeneous atoms like Cl, N, S due to the formation of corresponding HCl , HNO3 and H2SO4 acids. Recently, it was proposed that the addition of Na2CO3 significantly reduces the corrosion. This work examines the effect of Na2CO3 on the oxidation kinetics of wastes containing hetero-atoms in supercritical water. The kinetics data in absence of Na2CO3 is verified to conform to the literature data. In the presence of Na2CO3, oxidation is highly enhanced due to a decrease in the activation energy from 11.5 to 2.4 kcal/mol for 2-chlorophenol and from 10.4 to 7.5 kcal/mol for phenol. Also, Na2CO3 plays a key role in reducing the corrosion on reactor walls by first neutralizing the acid and then providing large surface area to adsorb the precipitated corrosive compounds. Because Na2CO3 is insoluble in supercritical water, it precipitates as fine particles with a large surface area. A new reactor design is proposed to obtain fine Na2CO3 particles based on supercritical anti-solvent method; these fine particles provide surface area that is several orders of magnitude larger than that of the reactor wall.

[46] - Technology for a Sustainable Environment Chair:Barbara KarnUS EPANCERQA401 M St. 8722RWashington, DC 20460-1300Telephone Number: 202-564-6824Fax Number: 202-565-2446Email: Karn.Barbara@epamail.epa.gov Vice Chair:Vasilios ManousiouthakisUniversity of California, Los Angeles405 Hilgard AveDepartment of Chemical EngineeringLos Angeles, CA 90095Telephone Number: 310-825-9385Fax Number: 310-206-4107Email: vasilios@ucla.edu

[46d] - Carbon Dioxide-Soluble Binder and Template Materials for Metal Casting Operations

Esin Gulari (speaker) Wayne State University Department of Chemical Engineering Detroit, MI 48202 Phone: 313-577-3767Fax: 313-577-3810 Email: egulari@che.eng.wayne.edu

Abstract: Removable templates and binders are frequently employed in the casting of metal and ceramic parts. The template and binder materials, which are used to define the shape of the finished part, must be removed during the casting process. Conventional templates and binders are typically composed of polymers. These materials are removed by dissolution in solvents or by gas phase combustion or decomposition. Unfortunately, the removal of material by these methods can generate unwanted and toxic emissions, waste, and worker exposure to hazardous compounds. In principle, extraction of binders and templates by supercritical carbon dioxide can offer an environmentally friendly alternative method for template and binder removal. However, most conventional polymers have very low solubilities in supercritical carbon dioxide. Here we present laboratory studies on a

new class of carbon dioxide-soluble template and binder materials composed of polyethylene glycols compounded and thermally blended with organic cosolutes such as diphenyl carbonate. The solubility of these materials in carbon dioxide is examined as a function of PEG/DPC composition ratio, and as a function of PEG molecular weight. Analysis of the thermally blended materials by differential scanning calorimetry (DSC) is also employed to examine the melting characteristics of the solid. An interesting result is that compositions exhibiting high solubility in carbon dioxide are near the compositions exhibiting melting point minima in the DSC scans. A thermodynamic interpretation of this result is presented, using simple theoretical models.

[46e] - Catalysis with Near-Critical Reaction Media: Environmentally Benign Alternatives to Conventional Processing

Bala Subramaniam (speaker) University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785-864-2903Fax: 785-864-4967 Email: bsubramaniam@ukans.edu

Abstract: The density and transport properties of near-critical fluids can be continuously pressure-tuned in the near-critical (nc) region to obtain unique fluid properties (e.g., gas-like transport properties, liquid-like solvent power and heat capacities), which offer several advantages such as these: 1. the in situ extraction of heavy hydrocarbons (i.e., coke precursors) from the catalyst surface and their transport out of the pores before they are transformed to consolidated coke, thereby extending catalyst lifetime; 2. complete miscibility of reactants such as oxygen and hydrogen in the reaction mixture and enhanced pore-transport of these reactants to the catalyst surface, thereby promoting desired reaction pathways; 3. enhanced desorption of primary products preventing secondary reactions that adversely affect product selectivity; and 4. control of temperature rise in exothermic oxidation and hydrogenation reactions, thereby preventing "reactor runaway" conditions. Experimental and theoretical investigations will be presented to demonstrate pressure-tuning effects on catalyst activity and product selectivity during continuous processing of a variety of reactions such as these: hydrogenations on supported catalysts; 1-butene/isobutane alkylation on solid acid catalysts; and homogeneous catalytic oxidations in CO2-expanded media. It will be shown that in addition to the foregoing advantages over conventiional processing, operation with near-critical media also offers the possibility of environmentally benign processing. Prospects and challenges for scaleup and commercialization of these processes will also be discussed.

[57d] - Separations in or with Supercritical Fluids

Erdogan Kiran (speaker) Virginia Polytechnic Institute & StateUniversity 133 Randolph Hall Blacksburg, VA 24061 Phone: 540-231-4213Fax: 540-231-5022 Email: ekiran@vt.edu

Abstract: Supercritical fluid based processes are going to play a major role in chemical engineering practice in the new millenium. There is already intense research in separations, reactions, and materials processing in or with supercritical fluids that tries to take advantage of the special properties of these fluids.

Supercritical fluids are neither gas nor liquid but can be compressed gradually from low to high density. As a result a wide range of properties from gas-like to liquid -like become accesible by these fluids by simple manipulation of pressure and/or temperature. As such, these are tunable fluids that can be customized for a given application. They are ideal for selective and or sequential separations by pressure or density tuning. For example, depending upon the fluid density, the fluid may be tuned to behave as a specific solvent for a specific substance at one pressure, but as a non-solvent at another pressure. Historically, the pressure-tunable characteristics were first put to industrial practice in the selective extractions in the food industry as in decaffeination of coffee and tea. In the analytical field, these concepts were adopted in supercritical fluid chromatography.

The applications have expanded dramatically in the past decade to include a wide range of separations that are encountered in various industries such as the pharmaceuticals, polymers, inorganic materials, and in chemical recycling operations.

This presentation is aimed at providing an overview of current trends, but will focus more on the non-traditional aspects that are encountered in many of these processes. Pressure-tuning or profiling is one-such aspect that is normally not introduced as a separation methodology in the traditional chemical engineering curriculum. Coupling of high-pressure phase equilibria in separations, or taking advantage of the compositional tuning of the separation medium with binary fluids at high pressures are examples of additional aspects that are encountered in supercritical fluid-based processes, but are not in our traditional educational process. Pressure-induced phase separation(PIPS) is another non-traditional concept that is central to processes using supercritical fluids.

Examples will be chosen from research conducted not only in our group, but also work carried out at other laboratories around the world to highlight the non-traditional aspects, and to emphasize the important role supercritical fluids are already playing and will continue to play in the coming years in chemical engineering operations. Future chemical engineers will likely become as comfortable with "pressure" in their thinking and teaching as we have been with "temperature" in the past.

[77] - Thermodynamics and Transport Properties in Supercritical Fluid [77a] - Spectroscopic Measurement of the Solubility of Organic Solids in Supercritical Fluids

Truc T. Ngo (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-6766Fax: 404-894-2866 Email: truc.ngo@che.gatech.edu

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu

Abstract: Many chemical processes use supercritical fluids, especially supercritical carbon dioxide (scCO2), as a replacement for conventional solvents or as a transport medium for impregnating polymers with organic compounds. Therefore, it is important to know the solubility of solid organic compounds in scCO2 over a wide range of density. The most common method for measuring the solubility of organic solids in scCO2 is by a transpiration apparatus. This flow technique is useful at higher concentrations, (>10^-3 mole fraction) but is insensitive and may give irreproducible results at very low concentrations (<10^-5 mole fraction). We show how different spectroscopic techniques, including Infrared, Ultraviolet/Visible, and Fluorescence, can be used to measure the solubility of anthracene in scCO2 at concentrations as low as 10^-6 or 10^-7 (in mole fraction). In Infrared, the C-H stretching vibrations at 3065 cm-1 and 881 cm-1 are used for data analysis; whereas in UV/Vis, the absorption peaks at wavelengths of 365nm - 369nm, and in Fluorescence, the emission peaks at 367nm - 425nm are used. As a result, different spectroscopic techniques are recommended for different concentration regions. The solubility experiments were carried out in situ, in a high-pressure optical path cell, at 40oC, and with pressure range of 75 bars to 250 bars. The results show that the data collected from these spectroscopic measurements are consistent, reproducible, and compare well to literature data by other techniques.

[77b] - Surface Interaction of Supercritical Fluids with Microporous Materials

Raashina Humayun (speaker) Ohio State University 140 W. 19th Ave. Columbus, OH 43210 Phone: 614 298 8541Fax: 614 292 3769 Email: humayun.1@osu.edu

David L. Tomasko Ohio State University 140, W. 19th. Ave., Koffolt Lab Columbus, OH 43210 Phone: 614-292-4249Fax: 614-292-3769 Email: tomasko@che.eng.ohio-state.edu Abstract: Adsorptive processes using supercritical fluid solvents are fundamental to various applications including extractions, adsorptive/chromatographic separations, and catalysis. However, adsorption in the near critical region on engineering materials is poorly understood and exhibits unique behavior. It is now being recognized that the adsorption of the supercritical solvent plays an important role in the solute adsorption. A basic knowledge of the surface-fluid interactions is required to control and optimize operating conditions for economical use of these environmentally benign solvents in heterogeneous processes. In this paper we will present the results of a fundamental investigation of adsorption of and from supercritical fluids. We will describe in detail the adsorption of the pure supercritical solvent - carbon dioxide on two microporous adsorbents, activated carbon and NaY zeolite. We will also discuss the adsorption of solutes from supercritical solutions specifically two isomers of dimethylnaphthalene. The role of the interaction of the supercritical solvent with the surface on the subsequent adsorption of solutes will be analyzed.

A gravimetric apparatus developed in our laboratory is used to accurately measure pure solvent adsorption isotherms from sub atmospheric to supercritical pressures. Breakthrough curves for the the adsorption of solutes from supercritical solution are measured in a frontal analysis flow through apparatus. Excess adsorption-desorption isotherms of carbon dioxide on two microporous adsorbents - granular activated carbon and Na-Y zeolite at subcritical and supercritical temperatures measured continuously from sub-atmospheric pressure to 200 bar. The pure solvent isotherms measured go through a broad maxima near the critical point after which the excess adsorption drops sharply as the fluid density increases. At subcritical temperatures a discontinuity is observed near the saturation pressure where pore condensation occurs. Near the critical point the isotherms crossover such that the amount of excess adsorption increases with increasing temperature. When analyzed as a function of solvent density the crossover disappears revealing an abnormal maximum in total adsorption near the critical point similar to the enhanced local density or "charisma" observed in binary solute-supercritical systems. The solute adsorption data combined with the that of the pure solvent is used for thermodynamic analysis of the high pressure adsorption process and the development of fundamental models including 2-D Equation of State and local density based models. The accurate representation of supercritical solvent adsorption will aid in a more fundamental understanding of processes which involve the adsorption/desorpion of solutes during heterogeneous supercritical fluid processes.

[77c] - Heat Transfer in an Endothermic Jet Fuel at Near-Critical and Supercritical Conditions

Kenneth M. Benjamin (speaker) University of Michigan 2300 Hayward St., 3074 H.H. Dow

Ann Arbor, MI 48109-2136 Phone: (734)764-7121Fax: (734)763-0459 Email: benjamkm@engin.umich.edu

Theodore W. Randolph University of Colorado One Engineering Drive Boulder, CO 80309-0424 Phone: (303)492-4776Fax: (303)492-4341 Email: theodore.randolph@colorado.edu Abstract: High-speed aircraft, which exceed the speed of sound, encounter large frictional heat loads. For such aircraft, the fuel is the most efficient coolant. It has been proposed to replace conventional fuels with a substance that can undergo an endothermic reaction prior to its combustion. Such an endothermic reaction would provide an effective heat sink to absorb some of the large frictional heat load, thereby preventing thermal degradation of the fuel/coolant. One such proposed replacement fuel is methylcyclohexane. Operating conditions for a methylcyclohexane-based heat exchange system would span the liquid and supercritical regions. Hot-wire anemometry was used to measure natural convection heat transfer coefficients in near-critical and supercritical methylcyclohexane. The existing natural convection heat transfer correlation was modified to use integrated-averaged thermophysical properties. At reduced pressures and densities greater than 1.2 and 1.7, respectively, correlation predictions agreed well with experimental results and indicated liquid-like heat transfer. For reduced pressures and densities less than 1.0, correlation predictions and experimental results suggest gas-like heat transfer. Experimental measurements at reduced pressures less than 1.2 and reduced densities greater than 1.3 showed more liquid-like heat transfer behavior, and the anomalous behavior at the pseudo-critical point was dampened out. Correlation predictions based on temperature integrated-averaged properties were poor in this region. When the integrated-averaged properties were based on distance, rather than temperature, the correlation agreement here was improved dramatically. At reduced pressures and densities less than 1.1 and 1.3, respectively, the experimental heat transfer coefficients were a factor of three greater than correlation values.

[77d] - Solubility of Polydimethylsiloxanes in Supercritical Carbon Dioxide.

Ireneo D. Kikic University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763433Fax: +39 040 569823 Email: ireneok@dicamp.univ.trieste.it

Paolo Alessi (speaker) University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763437Fax: +39 040 569823 Email: paoloa@dicamp.univ.trieste.it

Angelo Cortesi University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763755Fax: +39 040 569823 Email: angeloc@dicamp.univ.trieste.it

Febe Vecchione University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763436Fax: +39 040 569823 Email: vecchione@dicamp.univ.trieste.it

E. Puppis University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763764Fax: +39 040 569823 Email:

Abstract: The use of surface modifiers in the pharmaceutical processing is widely applied for the stabilization of small particles in suspension. The production of submicron-sized particles of biologically active compounds in supercritical conditions in the steps of the process includes the presence of the surface modifiers. Some of the processes proposed for the production of fine

particles need the solubility of the surfactants in the supercritical fluids. In this work the solubility of various polydimethylsiloxanes at different molecular weight in supercritical carbon dioxide at different temperatures and pressures are reported and discussed.

[77e] - Novel Single-Phase Fluorous-Organic Systems for Environmentally Benign Processing

Kevin N. West (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-6766Fax: Email: kevin.west@che.gatech.edu

Jason P. Hallett Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6766Fax: (404)894-9085 Email: jason.hallett@che.gatech.edu

David Bush Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6885Fax: Email: Christy W. Culp Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6766Fax: (404)894-9085 Email: christy.culp@che.gatech.edu

Charles L. Liotta Georgia Institute of Technology Ga Tech Office of the President, Carnegie Building Atlanta, GA 30332-0325 Phone: 404-894-8884Fax: Email: charles.liotta@carnegie.gatech.edu

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu Abstract: Environmental and economic driving forces have recently promoted interest in fluorous biphasic chemistry. The benefit comes from the immiscibility of perfluorinated solvents with organic and aqueous phases, making separation as simple as decantation. The main focus of research so far has been in developing immobilized catalysts that reside only in the fluorous phase and act only at the fluorous-organic interface. Although these types of systems are promising, they may be greatly limited by mass transfer.

An appreciable amount of gaseous carbon dioxide will dissolve in both the fluorous phase and in organic solvents and can act as a cosolvent for both phases. We demonstrate that under modest CO2 pressure the organic and fluorous phases become miscible. Thus, the reaction systems that have previously been carried out under biphasic conditions may now be run homogeneously with the application of CO2 pressure. Depressurizing causes the phases to split and the facile separation is retained. The ease of separation and the immobilized catalyst will reduce capital and energy costs. In some cases the organic phase could be neat reactant, thus reducing the use of volatile solvents. Additionally, other types of immobilized catalysts have been investigated and this phenomenon has been examined as an extractive separation media.

[77f] - Thermodynamic Properties and Solvent Strength of Carbon Dioxide-Expanded Fluorinated Solvents

Yeh Wei Kho (speaker) University of Kentucky 160 Anderson Hall Lexington, KY 40506-0046 Phone: (606)257-2300 x 244Fax: (606)323-1929 Email: ywkho0@sac.uky.edu

Barbara L. Knutson University of Kentucky 157 Anderson Hall Lexington, KY 40506-0046 Phone: (606)257-5715

Fax: (606)323-1929 Email: bknutson@engr.uky.edu Abstract: Liquids expanded with a compressed gas or supercritical fluid have recently been investigated for the precipitation and purification of pharmaceuticals, the generation of ultrafine particles, and as reaction media for chemical synthesis. These processes take advantage of the ability to alter the solvent strength, density, and mass transfer characteristics with the dissolution of the compressed fluid. Compressed or supercritical CO2 has been favored as the expansion fluid because it is nontoxic, nonflammable and environmentally benign. The significant interest in extending CO2-based technologies to hydrophilic systems has resulted in the design of CO2-amphiphiles based on CO2-philic functionalities, which are functionalities that are highly soluble in CO2. Hydrofluoroethers (HFEs), for example, are a class of solvents characterized by CO2-philic properties such as low viscosity, low cohesive energy density and low surface tension. As recently demonstrated in our laboratory, HFE may be an appropriate substitute for CO2 in some applications, offering the benefit of reduced operating pressures.

This study investigates the fundamental behavior and synergy between fluorinated solvents and CO2 in a compressed, expanded liquid environment. The fluorinated solvents investigated include hydrofluoroethers, a highly-fluorinated hydrocarbon, and perfluorohexane. The expansion behavior of binary mixtures of fluorinated solvents and CO2, determined with bubble point pressures of the CO2-expanded liquids, is reported and compared to traditional CO2-expanded organic solvents systems at 25oC. In addition, the reduction of densities of the liquid mixtures and the decrease in the viscosity of the liquids as a function of CO2 addition are reported. The measurements of the physical properties of the expanded liquid mixtures are further interpreted with solvatochromic studies which characterize the solvent strength of these binary mixtures.

[77g] - Solvatochromic Properties of Near- and Supercritical Ethanol and Nearcritical Acetic Acid

Jie Lu (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-2876Fax: (404)894-9085 Email: jie.lu@che.gatech.edu

Charles L. Liotta Georgia Institute of Technology Ga Tech Office of the President, Carnegie Building Atlanta, GA 30332-0325 Phone: 404-894-8884Fax: Email: charles.liotta@carnegie.gatech.edu

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu

Abstract: Near- and supercritical ethanol and acetic acid have widely tunable properties (such as density, dielectric constant, and acidity/basicity) with variations in temperature and pressure. They are novel media for both reactions and separations as a replacement for environmentally undesirable organic solvents. The adjustable solvent strength may not only enhance the reaction rate and selectivity, but also facilitate downstream separations and solvent reuse. However, for the development of such applications more knowledge of the properties of ethanol and acetic acid at extreme conditions is needed.

With a rapid, in-situ spectroscopic technique, we investigated the polarity/polarizability, hydrongen-bonding donor and acceptor abilities in terms of the Kamlet-Taft solvatochromism scales pi*, alpha and beta in saturated nearcritical C2H5OH and CH3COOH, and in supercritical C2H5OH as a function of pressure, respectively. These solvent parameters form a basis for exploring the feasibility of processes in the novel media.

[77h] - Modeling of Association Effects in Mixtures of Fatty Oil Derivatives at High Pressure

Esteban A. Brignole PLAPIQUI Camino La Carrindanga Km7 - CC 717 Bahia Blanca, 8000 Argentina Phone: 00-54291-861700Fax: 00-54291-861600 Email: prbrigno@criba.edu.ar

Susana B. Bottini (speaker) PLAPIQUI Camino la Carrindanga Km 7 - CC 717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: prbottin@criba.edu.ar

Olga Ferreira PLAPIQUI

Camino la Carrindanga Km 7 - CC 717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: oferreira@plapiqui.edu.ar

Tiziana Fornari PLAPIQUI Camino la Carrindanga Km 7 - CC 717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: tfornari@criba.edu.ar

Abstract: Supercritical processes are of interest in the fatty oil industry for a variety of applications: extraction and refining, removal of pollutants, recovery of specialties, hydrogenation of oils and derivatives, etc. Typical process mixtures include heavy compounds and gases at near-critical conditions. At high pressures these asymmetric systems present a complex multi-phase behavior, difficult to model. This complexity increases if some of the mixture components present association. Recently (1) the group contribution equation of state GC-EOS (2) has been successfully used to model the phase behavior of mixtures of supercritical fluids with fatty oils and derivatives.In the present work an extended version of this model, the group contribution associating equation of state GCA-EOS (3) is used to represent high pressure phase equilibria in mixtures of supercritical gases (carbon dioxide, propane, ethane, dimethyl ether) with fatty oil derivatives, such as mono- and di-glycerides, fatty acids, alcohols and water. Self- and cross-association between the associating groups present in the mixtures (alcohol OH, water H2O and acid COOH) are considered.Satisfactory correlation and prediction of equilibrium data are obtained. The capacity of the model to follow the behavior of the solutions towards the limit at infinite dilution of the associating component, is of particular importance.

References(1) Bottini S.B., T. Fornari and E.A. Brignole, Fluid Phase Equilibria 158-160, 211-218, 1999(2) Skjold-Jorgensen S., Fluid Phase Equilibria 16, 317-351, 1984(3) Gros H.P., S.B. Bottini and E.A. Brignole, Fluid Phase Equilibria 116, 535-544, 1996

[84b] - Dielectric Spectroscopy of Carbon Dioxide and Methanol Mixtures

Sung Bong Lee SR Kaihatsu Higashi Ohdori 1-1-13 Mizusawa, Iwate-ken 023-0828 Japan Phone: 81-22-51-1646

Sachio Suzuki Tohoku University Aoba-ku, Aza Aramaki Aoba-07 Sendai, Miyagi-ken 980-8579 Japan Phone: 81-22-217-7282Fax: 81-22-217-7282 Email: sacchi@scf.che.tohoku.ac.jp

Richard L. Smith (speaker) Tohoku University Aoba-ku, Aza Aramaki Aoba-07 Sendai, 980-8579 Japan Phone: 81-22-217-7247Fax: 81-22-217-7293 Email: smith@scf.che.tohoku.ac.jp

Hiroshi Inomata Tohoku University Japan Phone: Email: inomata@scf.che.tohoku.ac.jp

Kunio Arai Tohoku University Aoba07, Aramaki-Aza, Aoba-ku Sendai, 980-8579 Japan Phone: +81-22-217-7245Fax: +81-22-217-7246 Email: karai@arai.che.tohoku.ac.jp

Abstract: In this work, we show a technique that we developed for measuring the dielectric spectroscopy of fluids and fluid mixtures at elevated pressures. A new coaxial probe was developed for use under high pressure conditions. Measurements of the complex permittivity and relaxation of supercritical carbon dioxide and methanol mixtures were performed over the range of 50 MHz to 20 GHz at temperatures ranging from 313 K to 323 K and at pressures up to 18 MPa. At 323 K and 11 MPa, as the CO2 concentration increased, the relaxation time of methanol shifted from its pure value of 28 ps to a maximum at 31 ps at a methanol mole fraction of 0.73. The Kirkwood g-factor was calculated from the relative permittivity data. However, the Kirkwood g-factor could not not explain the maximum in relaxation time because the g-factor did not change significantly over the range where the maximum in tau was observed. According to the spectra and analysis, CO2 was initially attracted to methanol hexamers where it was added to the methanol. The attraction increased the size of the aggregates, which lead to an initial increase in the relaxation time. Further CO2 addition resulted in reduced methanol-methanol aggregate attraction, which resulted in the relaxation time decreasing. It is found that the behavior can be described by analysis of the free volume. A simple correlation of the relaxation time with free volume and temperature is proposed that uses only pure component properties.

[103a] - Organically-stabilized nanocrystal synthesis in supercritical water

Kirk J. Ziegler (speaker) University of Texas, Austin 26th and Speedway, MC C0400 Austin, TX 78731 Phone: 512-471-6484Fax: 512-475-7824 Email: kziegler@che.utexas.edu

R. Christopher Doty University of Texas, Austin Department of Chemical EngineeringAustin, TX 78712 Phone: 512-471-2828Email: doty@che.utexas.edu

Keith P. Johnston University of Texas, Austin 26th & Speedway Austin, TX 78712 Phone: 512 471 4617Fax: 512 475 1062 Email: kpj@ce.utexas.edu

Brian A. Korgel University of Texas Department of Chemical EngineeringAustin, TX 78712-1062 Phone: 512-471-5633Fax: 512-471-7060 Email: korgel@che.utexas.edu

Abstract: The tunability of the solvation properties of supercritical fluids with density, through temperature and pressure changes, has led to its increased use in materials chemistry. For example, by heating water to the critical point (Tc = 374캜, Pc = 221 bar), the dielectric constant is dramatically reduced (e ~ 5) thereby decreasing the solubility of salts and increasing the solubility of organic molecules.

Recent efforts have been made to control particle formation in SCW to create useful materials, such as ceramics, coatings, and catalysts. A variety of particulate chemistries can now be produced using SCW as a reactive medium; however, particle size control in the nanometer range (i.e. < 10 nm diameters) has not been shown.

In this study, we demonstrate that the use of a stabilizing ligand (alkanethiol) during the synthesis of metal and metal oxide crystals provides nanostructure size control. Moreover, due to the unique environment provided by SCW, the capping ligands control the nanostructure morphology and chemistry. In the absence of these capping ligands, particles are produced with broad size distributions. To the best of our knowledge, this study is the first example of organically passivated nanocrystal formation in SCW.

[110] - Self-Assembly in Supercritical FluidsChair: Anders WistromUniversity of California, RiversideDepartment of Chemical and Environmental EngineeringBourns HallRiverside, CA 92521Telephone Number: 909-787-5487Fax Number: 909-787-3188Email: wistrom@engr.ucr.edu

Vice Chair: llja SiepmannUniversity of MinnesotaDepartment of Chemistry207 Pleasant St., S.E.Minneapolis, MN 55455-0431

Telephone Number: 612-624-1844Fax Number: 612-626-7541Email: siepmann@chem.umn.edu

[110a] - Self-Assembled Monolayer Films from Liquid and Supercritical Carbon Dioxide

G. Kane Jennings Vanderbilt University Department of Chemical Engineering Box 1604, Station B Nashville, TN 37235 Phone: 615-322-2707Fax: 615-343-7951 Email: jenningk@vuse.vanderbilt.edu

Randy D. Weinstein (speaker) Villanova University Department of Chemical Engineering Villanova, PA 19085 Phone: 610-519-4954Fax: 610-519-7354 Email: randy.weinstein@villanova.edu

Dong Yan Vanderbilt University Box 1604 Station B Nashville, TN 37235 Phone: 615-322-1467Fax: 615-343-7951 Email: dong.yan@vanderbilt.edu

Abstract: This paper reports the formation and characterization of n-alkanethiolate self-assembled monolayers (SAMs) onto gold substrates from environmentally benign liquid and supercritical carbon dioxide (scCO2). SAMs are molecular films that form spontaneously onto metal substrates from organic solvents such as ethanol, hexane, and chloroform. These solvents can create waste disposal problems and enhanced volatile organic compound emissions. Furthermore, it is difficult to remove dilute concentrations of n-alkanethiolates from these solvents. Carbon dioxide has advantages over organic solvents for the preparation of SAMs in that it is environmentally benign, inexpensive, and easy to recycle and separate from liquid and solid compounds with changes in pressure. In addition, scCO2 has a significantly higher diffusivity and lower viscosity than traditional organic solvents. These properties enhance the rate of the SAM formation, and SAMs are formed faster in scCO2 than in traditional solvents such as ethanol. As evidenced by infrared spectroscopy, SAMs prepared from scCO2 at 1500 psi, 35 C are completely formed in as little as 5 min and exhibit structures that are highly crystalline with few gauche defects. The level of crystallinity and packing density of these SAMs are equivalent to or greater than those for SAMs formed in common organic solvents. The structure of the SAM is affected by the pressure and thus the density of the scCO2. The surfaces of these SAMs exhibit wetting properties that are similar to those for SAMs formed in organic solvents. The use of scCO2 as solvent is also compatible with polar adsorbates such as -OH and -CO2H terminated thiols to enable the preparation of high-energy surfaces that are wet by water.

[110b] - Association of Formic Acid in Carbon Dioxide

Yoonkook Park (speaker) Auburn University 230 Ross Hall, Dept. of Chem. Eng. Auburn, AL 36849 Phone: 334-844-2071Fax: 334-844-2063 Email: parkyon@eng.auburn.edu

Ram Gupta Auburn University Chemical Engineering Department 230 Ross Hall Auburn, AL 36849-5127 Phone: 334-844-2013Fax: 334-844-2063 Email: gupta@eng.auburn.edu

Christine W. Curtis Auburn University 230 Ross Hall Auburn, AL 36849 Phone: 334-844-5969

Christopher Roberts Auburn University Department of Chemical Engineering Auburn, AL 36849 Phone: 334-844-2036Fax: 334-844-2063 Email: croberts@eng.auburn.edu

Abstract:

The association of formic acid in carbon dioxide at 298 - 318 K and 75 - 100 bar has been studied using Fourier transform infrared (FTIR) spectroscopy. The equilibrium constant, Kc, between monomer and dimer of the formic acid was obtained by based on the C=O stretching band for formic acid. The concentration of formic acid studied was ranged from 1.0 ´ 10-3 to 7.4 ´ 10-3 mol dm-3. In general, the results show that an increase in density causes an increase in the concentration of the formic acid monomer, which results in a decrease in Kc. The modified lattice-fluid hydrogen bond model (MLFHB) has been used to interpret the effects of density on the Kc. Furthermore, the association of formic acid in carbon dioxide was also studied in the presence of a hydrogen bond accepting polymer. The effect of polymer and the supercritical carbon dioxide conditions on the equilibrium behavior of the formic acid will be discussed in terms of the role of hydrogen bonding, density, and various functional groups.

[110c] - Monte Carlo Simulations of Supercritical Fluid Extraction Systems

Jeffrey J. Potoff (speaker) University of Minnesota 207 Pleasant ST SE Minneapolis, MN 55455-0431 Phone: 612-626-2085Email: potoff@chem.umn.edu

John M. Stubbs University of Minnesota 207 Pleasant St. SE Minneapolis, MN 55455 Phone: 612 626 2085Fax: 612 626 7541 Email: stubbs@chem.umn.edu

llja Siepmann University of Minnesota Department of Chemistry 207 Pleasant St., S.E. Minneapolis, MN 55455-0431 Phone: 612-624-1844Fax: 612-626-7541 Email: siepmann@chem.umn.edu

Abstract: Configurational-bias Monte Carlo simulations in the grand canonical and Gibbs ensembles were employed to calculate temperature-composition and pressure-composition diagrams and to investigate the microscopic structures of the supercritical fluid phase. Simulations were carried out for the binary mixture of (supercritical) carbon dioxide and methanol and for the ternary mixtures of (supercritical) carbon dioxide, benzoic acid or phenanthrene, and entrainer (benzene or acetone).Analysis of radial distribution functions, their number integrals, and of cluster size distributions allows us to shed light on the different assemblies found in these supercritical phases. Part of the computer resources were provided by the Minnesota Supercomputing Institute (MSI).

[110d] - Self-Assembly of Reverse Micelles in Supercritical CO2 by Molecular Dynamics Simulation

Hank D. Cochran (speaker) Oak Ridge National Laboratory Chemical Technology Division Oak Ridge, TN 37831-6224 Phone: 865-574-6821Fax: 865-241-4829 Email: hdc@ornl.gov

Sumeet Salaniwal University of Tennessee 419 Dougherty Engineering Building Knoxville, TN 37996-2200 Phone: 865-974-2421

Shengting Cui University of Tennessee 419 Dougherty Engineering Building Knoxville, TN 37996-2200 Phone: 865-241-4896Email: scui@utk.edu

Peter Cummings University of Tennessee, Knoxville Chemical Engineering Department Knoxville, TN 37996-2200 Phone: 423-974-0227Fax: 423-974-7076 Email: ptc@utk.edu IntroductionSupercritical CO2 offers potential as a benign substitute for hazardous industrial solvents, but many substances have very low solubility. Surfactants may be used to disperse insoluble liquids in supercritical CO2, but few commercial surfactants are suitable. Understanding is needed to guide the development of new surfactants for use in CO2. Molecular simulation can aid in providing the necessary understanding.

ApproachWe have studied reverse micelles with aqueous cores in CO2 by molecular dynamics simulation using a model that we developed for the dichain surfactant (C7H15)(C7F15)CHSO4-Na+. It was assembled from existing models for the sulfate head group, sodium ion, alkane tail, and perfluoroalkane tail. We simulated 33 surfactant, 1,175 water, and 12,800 CO2 molecules at T=298K and CO2 density = 0.848 g/cm3, the subcritical statepoint of small angle neutron scattering experiments [1].

ResultsThe system rapidly self-assembled into aggregates with water in the core and surfactants at the interface. Numerous rapid changes in the number of aggregates by +- 1 represent collisions of the surfactant tails, which did not result in coalescence. When collisions resulted in contact between aqueous cores coalescence almost always occurred. The surfactant tails, therefore, provided steric stabilization of the aggregates. The rate of self-assembly was determined to be consistent with the theory of Smoluchowski for diffusion-limited coalescence. The strong coulombic forces and high diffusivity of molecules and aggregates explain why the self-assembly was rapid in CO2 compared to the rate in organic liquids. The aggregates formed had the appearance of reverse micelles and their structural characteristics were consistent with experimental results [2-5].

References1. Eastoe, J., et al. (1996). Droplet structure in a water-in-CO2 microemulsion. Langmuir, 12, 1423-1424.2. Salaniwal, S., et al. (1999). Self-Assembly of Reverse Micelles with Aqueous Cores in Supercritical Carbon Dioxide via Molecular Simulation. Langmuir, 15, 5188-5192.3. Salaniwal, S., et al. (2000a). Self-assembly in a dichain surfactant/water/carbon dioxide system via molecular simulation. I. Structural properties of surfactant aggregates. Langmuir, submitted.4. Salaniwal, S., et al. (2000b). Self-assembly in a dichain surfactant/water/carbon dioxide system via molecular simulation. II. Aggregation dynamics. Langmuir, submitted.5. Salaniwal, S., et al. (2000c). Molecular Dynamics Simulation of Reverse Micelles in Supercritical Carbon Dioxide. Ind. & Eng. Chem. Res., submitted. [110e] - Effect of Interfacial Properties on the Formation of Emulsions in Supercritical Carbon Dioxide

Ed A. Sander University of Texas, Austin 1237 Beverly Garden Dr. Metairie, LA 70002 Phone: (504) 835 7019Email: e.sander@mail.utexas.edu

Petros A. Psathas (speaker) University of Texas, Austin Dept. of Chemical Engineering, University of Texas at Austin Austin, TX 78712 Phone: 512 471 9602Fax: 512 475 7824 Email: psathp@che.utexas.edu

Keith P. Johnston University of Texas, Austin 26th & Speedway Austin, TX 78712 Phone: 512 471 4617Fax: 512 475 1062 Email: kpj@ce.utexas.edu

Abstract: Emulsions composed of water and CO2 may be utilized for cleaning of metals, semiconductors, and fabrics, solvent-free coatings, solubilization of biomolecules and enhanced oil recovery. Physical characteristics of CO2 such as low viscosity and low dielectric constant as well as limited solubility of surfactants, make the formation of stable and unflocculated emulsions challenging. The primary objective of this study is the development of novel polydimethylisiloxane (PDMS) and perfluoropolyether (PFPE) based surfactants suitable for the formation of stable water-in-CO2 (W/C) and CO2-in-water (C/W) microemulsions and emulsions. The emulsion formation and stability are assessed as a function of formulation variables including salinity, temperature, CO2 density and aqueous phase pH. Interfacial properties such as interfacial tension and adsorbed amount, are used as a reference point to understand emulsion stability and curvature (C/W or W/C) as a function of surfactant molecular structure and chemical affinity. The experiments were conducted in a variable-volume view cell in-line with an optical microscope for characterization of the droplet size and flocculation mechanisms. Emulsions formed with equal amounts of CO2 and water, in some cases were stable for more than 24h with limited or no flocculation.

[110f] - Dissolution, Micellization, Precipitation of Block Copolymers in Supercritical Carbondioxide

Kit-yan Chan Pennsylvania State University 133 Fenske Laboratory University Park, PA 16802 Phone: 814-865-2574Email: kxc267@psu.edu

R. Nagarajan (speaker) Pennsylvania State University 161 Fenske Laboratory University Park, PA 16802 Phone: 814-863-1973Fax: 814-865-7846 Email: rxn@psu.edu

Abstract: A thermodynamic treatment of block copolymer molecules in supercritical CO2 is formulated. The solvent characteristic of the supercritical CO2 is controlled by the pressure and temperature. At certain conditions of temperature and pressure, the solvent is a good solvent for both blocks of the diblock copolymer. Under these conditions, one observes molecular dissolution of the block copolymer in the solvent. As the conditions of T and p are modified, the solvent becomes a poorer solvent for one of the blocks while remaining a good solvent for the other block. Under these conditions the block copolymer molecules can self-assemble to generate micellar structures. As the conditions of T and p are further modified, the solvent can become a poor solvent for both blocks leading to the precipitation of the block copolymer from the solution. The thermodynamic analysis of these phenomena are developed for a diblock copolymer in supercritical CO2. Emphasis is placed on calculating the microstructure of the block copolymer micelles such as their core and corona dimensions and the extent of solvent presence in these two domains.

[110g] - Temperature Dependence of CO2 Viscosity-Enhancing Associations of Fluoroacrylate-Styrene Copolymers

Jianhang Xu (speaker) University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412 624 9630

Robert Enick University of Pittsburgh Department of Chemical And Petroleum Engineering 1259 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-9649Fax: 412-624-9639 Email: enick@engrng.pitt.edu

Eric J. Beckman University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-9631

Abstract: Fluoroacrylate-styrene copolymers (70% fluoroacrylate:30%styrene) are known to significantly increase the viscosity of liquid CO2 at 298 K, as determined with falling cylinder viscometry. This is attributed to the pi-pi stacking of the phenyl groups and the resultant macromolecular formation in solution. In this study, we investigate the increase in viscosity at 298-373 K (the range of temperature associated with CO2 floods for enhanced oil recovery requiring thickened CO2) for liquid and supercritical CO2. Further, the viscosity of the solutions is evaluated as a function of concentration using falling cylinder viscometry (high shear rates of 1000s-1), capillary coil viscometry 100 s-1) and flow through porous media (10 s-1). Recent developments in less expensive, non-fluorous thickening agents will also be presented.

[116] - Thermodynamics and Processing with Supercritical FluidsChair: Jefferson TesterMIT1 Amherst StreetRoom E40-455Cambridge, MA 02139-4307Telephone Number: 617-253-3401Fax Number: 617-253-8013Email: tester@mit.edu

Vice Chair: Randy D. WeinsteinVillanova UniversityDepartment of Chemical EngineeringVillanova, PA 19085Telephone Number: 610-519-4954Fax Number: 610-519-7354Email: randy.weinstein@villanova.edu

[116a] - Influence of Supercritical Carbon Dioxide on Glass Transition Temperatures of Polymers: Experimental Determinations.

Ireneo D. Kikic (speaker) University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763433Fax: +39 040 569823 Email: ireneok@dicamp.univ.trieste.it

Paolo Alessi University of Trieste Piazzale Europa 1 Trieste, I 34127

Italy Phone: +39 040 6763437Fax: +39 040 569823 Email: paoloa@dicamp.univ.trieste.it

Angelo Cortesi University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763755Fax: +39 040 569823 Email: angeloc@dicamp.univ.trieste.it

Febe Vecchione University of Trieste Piazzale Europa 1 Trieste, I 34127 Italy Phone: +39 040 6763436Fax: +39 040 569823 Email: vecchione@dicamp.univ.trieste.it

Abstract: The phase transitions of polymers at ambient pressure can be easily determined by gas-liquid chromatographic method due to the change in retention properties of the solutes according to the physical state of the polymer used as a stationary phase.Similarly the glass transition temperatures of polymers at high pressure in presence of carbon dioxide in supercritical condition can be determined by detecting at constant pressure the retention volumes of the solutes at different temperatures.The discontinuity of the behaviour of retention volume vs temperature is connected to the variation of the state of the polymer allowing to evidence the transitions.The method has been tested on two polymers for which the glass transition temperatures are reported in the literature: PMMA and polycarbonate with the same molecular weight have been used. The advantages and the limits of the methodology are pointed out and discussed.

[116b] - Solubility of PFOA and PDMS in Supercritical Carbon Dioxide Using SAFT

Coray M. Colina (speaker) North Carolina State University Department of Chemical Engineering Raleigh, NC 27695 Phone: 919-513-2051Fax: 919-513-2470 Email: ccolina@eos.ncsu.edu

Keith E. Gubbins North Carolina State University 113 Riddick Labs, Dept. of Chemical Engg. Raleigh, NC 27695-7905 Phone: 919-513-2262Fax: 919-513-2470 Email: keg@ncsu.edu Abstract: Supercritical carbon dioxide possesses many properties that have allowed it to emerge as the most extensively studied supercritical fluid for polymerization reactions. Supercritical CO2 is a viable and promising alternative to traditional solvents used in polymer synthesis. There are several important issues, such as drying, solubility, and polymer plasticization, that are involved when supercritical CO2 is used as a polymerization solvent [1]. Accurate modeling of phase behavior of polymer-solvent mixtures is necessary in order to design such processes.The Statistical Associating Fluid Theory (SAFT) [2,3] equation of state (EOS) is a molecular based equation that is designed to account for effects of molecular association (H-bonding, charge transfer, etc.) and chain flexibility, in addition to the more usual effects due to repulsive and dispersion interactions. Huang and Radosz [4] tested 60 phase equilibria data sets for asymmetric (small + large) and associating systems. The ability of SAFT to calculate phase transitions and phase equilibria was demonstrated for supercritical fluid + polymer systems [5,6].In this paper our focus is to model the cloud-point behavior for a mixture of non-associating polymer and CO2. Wherever possible we take parameters for CO2 + polymers from the literature, thus minimizing the fitting of new parameters. The experimental VLE data for specific polymer-containg systems are often not available, especially due to the enormous range of polymer sizes and compositions. We apply SAFT in its original form [3,4] for non-associating systems (PFOA+CO2,PDMS +CO2)*; for these cases the association term is set equal to zero. In the physical part of the model, three parameters are used for each component: number of segments in a molecule (m), temperature-independent segment volume (v00) and temperature-independent dispersion energy (u0/k). Because the solubility data of the polymers have been measured at temperatures close to the critical temperature of CO2, the model used in this work must give a better representation of the critical point of CO2. We test the different CO2 parameters present in the literature [3,8] for a better prediction of the critical properties of CO2, and the SAFT parameters for the polymers are obtained with the approach used by Huang-Radosz [3]. Only the binary interaction parameter, k12, was obtained from a given set of cloud curve data. A volume fraction mixing rule was used for the dispersion term, since it is known to give a better representation of binary vapor-liquid equilibria near the critical region [4]. With this set of parameters, the results obtained for the phase equilibria are in good agreement with those obtained by Luna-Barcenas et al.[7] and Xiong and Kiran [9], with the advantage that we do not need to use experimental values for our calculations (only the kij parameter is adjusted from experimental data). * PFOA: poly(1,1-dihydroperfluorooctylacrylate); PDMS: poly(dimethylsiloxane)

References

[1] Kendall, J.L.; Canelas, D.A.; Young, J.L.; DeSimone, J.M. "Polymerizations in Supercritical Carbon Dioxide", Chem. Rev. 1999, 99, 543-563.[2] Chapman, W.G.; Gubbins, K.E.; Jackson, G.; Radosz, M. "New Reference Equation of State for Associating Liquids", Ind. Eng. Chem. Res. 1990, 29, 1709-1721.[3] Huang, S.H.; Radosz, M. "Equation of State for Small, Large, Polydisperse, and Associating Molecules", Ind. Eng. Chem. Res. 1990, 29, 2284-2294.[4] Huang, S.H.; Radosz, M. "Equation of State for Small, Large, Polydisperse, and Associating Molecules: Extension to Fluid Mixtures", Ind. Eng. Chem. Res. 1993, 32, 762.[5] Chen, C.-K.; Duran, M.A.; Radosz, M. "Supercritical Antisolvent Fractionation of Polyethylene Simulated with Multistage Algorithm and SAFT Equation of State: Staging Leads to High Selectivity Enhancements for Light Fractions". Ind. Eng. Chem. Res. 1994, 33, 306-310.[6] Folie, B.; Radosz, M. "Phase Equilibria in High-Pressure Polyethylene Technology". Ind. Eng. Chem. Res. 1995, 34, 1501-1516.[7] Luna-Barcenas, G.; Mawson, S.; Takishima, S.; DeSimone, J.M.; Sanchez, I.C.; Johnston, K.P. "Phase Behavior of Poly(1,1-dihydroperfluorooctylacrylate) in Supercritical Carbon Dioxide", Fluid Phase Equilib. 1998, 146, 325-337.[8] Takishima, S.; O'Neil, M.L.; Johnston, K.P. "Solubility of Block Copolymer Surfactants in Compressed CO2 Using a Lattice Fluid Hydrogen-Bonding Model", Ind. Eng. Chem. Res., 1997, 36, 2821-2833.[9] Xiong, Y.; Kiran, E. "Miscibility, Density, and Viscosity of Poly(dimethylsiloxane) in Supercritical Carbon Dioxide". Polymer. 1995, 36, 4817-4826.

[116c] - Partitioning of Reactant Species in Heterogeneous Polymerizations in Supercritical Carbon Dioxide

Karen A. Kennedy (speaker) North Carolina State University Box 7565 Raleigh, NC 27695 Phone: 919-513-1654Fax: 919-513-1655 Email: kakenne2@eos.ncsu.edu

Joseph M. DeSimone University of North Carolina, Chapel Hill CB#3290, Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

George Roberts North Carolina State University Department of Chemical Engineering Raleigh, NC 27695-7905 Phone: 919-515-7328Fax: 919-515-3465 Email: groberts@eos.ncsu.edu

Abstract: In recent years, supercritical carbon dioxide (SCCO2) has been investigated for its potential to replace both aqueous and organic media used in polymerization reactions. The use of supercritical carbon dioxide as a polymerization medium has several benefits. Supercritical carbon dioxide is environmentally benign, has tunable properties, and can reduce the amount of wastewater generated in polymerizations. Heterogeneous chain-growth polymerizations in SCCO2 are of particular interest. Many monomers are readily soluble in SCCO2, whereas most polymers are insoluble in SCCO2. The polymer may be removed from the reaction medium by simply depressurizing the system. Additionally, the reaction may be controlled by adjusting the temperature or pressure - taking advantage of the tunable properties of SCCO2.

Among the research of heterogeneous polymerizations in SCCO2, there has been very little characterization of the effect of equilibrium between species in the polymer and SCCO2 phases. Relatively few studies have been conducted to measure polymer swelling and sorption at reaction conditions and model this behavior. Finally, the effect of partitioning on the polymerization kinetics and polymer properties has not been explored.

Results are presented for partition coefficients of vinylidene fluoride (VF2), relating the equilibrium of the solute between the polymer and SCCO2 phases. The partition coefficient was defined as the ratio of the concentration of solute in the polymer phase to that in the fluid phase. The concentration of the solute in the SCCO2 phase was measured using a gas chromatograph after the system reached equilibrium. Measurements were taken over a range of temperatures, pressures, and monomer concentrations, similar to those used for polymerization of vinylidene fluoride in SCCO2. In general, the partition coefficient decreased as the CO2 pressure was increased.

[116d] - The Solubility of Waxes in Supercritical Carbon Dioxide - Data, Correlation and Prediction

Takeshi Furuya (speaker) National Institute for Resources and Environment 16-3 Onogawa Tsukuba, Ibaraki 305-8569 Japan Phone: 011-(81)-298-61-8429Fax: 011-(81)-298-61-8409 Email: takeshi.furuya@nire.go.jp

Amyn S. Teja Georgia Institute of Technology 778 Atlantic Drive

Atlanta, GA 30332-0100 Phone: 404-894-3098Email: amyn.teja@che.gatech.edu Abstract: The deposition of solids (waxes) in natural gases is of interest in the development of new gas reserves. Failure to account for the presence of solids can lead to significant increases in operating costs, lost production, or failure of piping systems. Overdesign of facilities to account for solids can lead to higher capital and operating costs, and may prevent the development of otherwise economic natural gas resources. The solubility of typical waxes in carbon dioxide, methane and ethane at natural gas processing conditions has been the subject of several studies in our laboratory. New data on systems containing tetracosane, pentacosane, hexacosane, heptacosane and nonacosane are reported in this work.

Several models were examined for their ability to correlate and extrapolate the solubility data. Our results demonstrate that equation of state models are able to successfully correlate the data. However, they offer no insights as to the validity of the data and, moreover, cannot be used to extrapolate the information. In contrast, a new model based on the theory of dilute solutions correlates the data equally well. In addition, parameters in the new model are independent of temperature and therefore the model allows extrapolation of the solubility data to other conditions. The model also allows the validity of the data to be checked using measurements on the lower molecular weight alkanes.

[116e] - Adsorption Modeling for Mixtures Based on the Simplified Local Density (SLD) Approach

Carl T. Lira (speaker) Michigan State University 2527 Engineering Building East Lansing, MI 48824-1226 Phone: (517)355-9731Fax: (517)432-1105 Email: lira@egr.msu.edu

Xiao-ning Yang Michigan State University 2527 Engineering Building East Lansing, MI 48824 Phone: 1-517-432-5489Fax: 1-517-432-1105 Email: yangxia@egr.msu.edu

Aaron D. Soule Michigan State University Engineering Building 2527 East Lansing, MI 48824 Phone: 1-517-432-5489

Abstract: Abstract: The simplified local density (SLD) theory for adsorption together with the ESD equation of state was used to model and predict the adsorption behavior of binary mixtures onto activated carbon. Firstly, the adsorption characteristics of model mixtures with different molecular structure parameters were presented by using the SLD approach. The effect of adsorbate and adsorbent structures on the adsorption has been investigated. It was shown that this theoretical approach is able to describe the different adsorption behaviors. Secondly, the adsorption equilibria of several practical binary mixtures onto activated carbon, including the supercritical systems, have been correlated and predicted. The calculated results are compared with the experimental data.

[116f] - Distributed Activation Energy Kinetics Model for Supercritical Water Oxidation of Complex Organic Wastes

Frederic Vogel (speaker) MIT 1 Amherst Street Cambridge, MA 02139 Phone: (617) 253-0070Email: frederic.vogel@psi.ch

Kenneth A. Smith MIT 77 Massachusetts Ave. Cambridge, MA 02139 Phone: (617) 253-3400Email: kas@mit.edu

Jefferson Tester MIT 1 Amherst Street Room E40-455 Cambridge, MA 02139-4307 Phone: 617-253-3401Fax: 617-253-8013 Email: tester@mit.edu

William A. Peters MIT 1 Amherst Street Cambridge, MA 02139 Phone: (617) 253-3400

Email: peters@mit.edu Abstract: SCWO is of interest for remediation of complex organic mixtures with components of diverse chemical reactivity. Consequently, for engineering calculations there is need for SCWO kinetics models that capture the essentials of this reactivity multiplicity without assigning one or more reactions to each compound in the mixture.

This paper describes SCWO kinetic diversity by an infinite set of independent parallel first order reactions. The kinetics of this reaction set are represented mathematically by a continuous distribution of activation energies (DAEM). Others have applied this concept to the kinetics of annealing metal defects and to coal pyrolysis. For SCWO, a utilitarian 3-parameter DAEM model can be implemented by best fitting its predictions to experimental data on waste conversion as affected by temperature and residence time.

This paper shows that this model provides satisfying correlations for the SCWO kinetics of three complex organic waste mixtures: JP-5 (aviation jet fuel), a commercially vended hydraulic fluid, and an orange military dye marker. We also show that compared to a single reaction model, the DAEM provides a more realistic description of heat release rates during SCWO of pharmaceutical sewage sludge in a tubular, approximately adiabatic pilot plant reactor. Advantages and limitations of the DAEM vs. a single reaction model in predicting thermal balances and destruction kinetics for SCWO of various organic wastes are discussed.

[116g] - Vapor-Liquid-Solid Phase Transitions in Aqueous Na2SO4 and Na2CO3 Near the First Critical Endpoint: Experimental Data and Phase Boundaries

Ilmutdin M. Abdulagatov (speaker) National Institute for Standards & Technology 325 Broadway Boulder, CO 80303-3328 Phone: (303)497 4027Fax: (303)497 5224 Email: ilmutdin@boulder.nist.gov

Vladimir M. Valyashko N.S. Kurnakov Institute of Genaral and Inorganic Chemistry of the Russian Academy of Sciences Leninskii Ave.31 Moscow, 117907 Russia Phone: 90117 (095)935 47 45

Johanna M. H. Levelt-Sengers National Institute for Standards & Technology 100 Bureau Drive, Stop 8380 Gaithersburg, MD 20889 Phone: 301-975-2463Fax: 301-869-4020 Email: anneke@mailserver3.nist.gov

Abstract: Heat capacities at constant volume and composition will be presented for aqueous sodium sulfate tree compositions, 1 mass %, 5 mass %, and 10 mass %, respectively, and along 19 isochores, from 250 to 1073 in the temperature range from 350 to 670 K. In the range from 630 to 670 K , some of the isochores display two features in the heat capacity as a function of temperature: one peak or step when solid salt first precipitates; and , on further heating, a lambda-shaped peak when the vapor or liquid phase disappears. The interpretation of these features in terms of the solid-liquid-vapor phase diagram, and their consistency with earlier PVTx, phase boundary and three-phase data from literature will be discuss. We will present new data on the density of liquid solutions saturated with respect to the vapor. We supplement the existing three-phase data with new liquid compositions or densities. We will present also new fluid density data near the critical endpoint. For aqueous Na2SO4, we find T_cep=648.2+/-0.2 K, and for aqueous Na2CO3, T_cep=649.0+/0.2 K The present heat capacity data, as well as recent data for aqueous sodium carbonate, have sufficient resolution to distinguish, for the first time, the temperature of the critical endpoints in aqueous sodium sulfate and aqueous sodium carbonate from the critical temperature of pure water, (Tc=647.1+/-0.1) K.

[116h] - Technologies Developed For and Research Pertinent to Scale Control in Supercritical Water Oxidation (SCWO) Reactors

Marc Hodes (speaker) Bell Laboratories 700 Mountain Avenue, Rm 1E-304 Murray Hill, NJ 07974 Phone: 908 582 7847Fax: 908 582 6228 Email: hodes@lucent.com

Kenneth A. Smith MIT 77 Massachusetts Ave. Cambridge, MA 02139 Phone: (617) 253-3400Email: kas@mit.edu

Philip A. Marrone Arthur D. Little, Inc. 15W-211 Acorn Park

Cambridge, MA 02140 Phone: (617) 498-5316Fax: (617) 498-7221 Email: marrone.philip@adlittle.com

Jefferson Tester MIT 1 Amherst Street Room E40-455 Cambridge, MA 02139-4307 Phone: 617-253-3401Fax: 617-253-8013 Email: tester@mit.edu Abstract: Supercritical water oxidation (SCWO) is an effective technology for remediation of organic wastes; however, widespread commercialization of SCWO continues to be hindered by the severe corrosion and scale buildup/fouling associated with the process. Corrosion of SCWO reactor materials caused by acidic solutions that result from the oxidation of organic compounds containing heteroatoms such as S, Cl or P is often minimized by injecting neutralizing bases into the reactor. The salts formed upon neutralization (sulfates, chlorides, phosphates, etc.) have low solubility in SCW and, consequently, precipitate as solid phases. (Additional salts may be present in the waste stream as well.) Because the salts formed tend to be ``sticky,'' they often form agglomerates and coat internal surfaces thereby leading to plugging of transport lines and inhibition of heat transfer. After a reactor or transport line becomes plugged, it must be flushed with solution or water at a temperature sufficiently low todissolve the scale causing the plug. Often, this results in substantial and costly downtime in the SCWO process. In extreme cases, mechanical means can be necessary to remove scale. Shaw et al. (Shaw-91) and Tester et al. (Tester-93) reviewed general principles and research relevant to SCWO. Presented here is an in depth review of fundamental research pertinent to the control of scale buildup in SCWO followed by a review of the many technologies which have been developed to control scale. Fundamental concepts and studies reviewed include those on phase behavior, nucleation, and salt deposition rates at SCWO conditions. Scale control technologies reviewed include salt collection in a low temperature brine at the bottom of a continuos reactor; transpiration of (pure) water through reactor walls; ``Assisted Hydrothermal Oxidation'' using in-situ, insoluble bases to control scale; cross flow microfiltration; cycling of SCWO reactors with feed/flush steams; circulation of metal brushes through a tubular reactor; and the addition of salts to the reactor to cause salts that would ordinarily precipitate to remain in solution by changing phase behavior.

[117] - Materials Processing with Supercritical Fluids IChair: Simon MawsonUnion Carbide CorporationTechnical CenterSouth Charleston, WV 25303-0361Telephone Number: 304-747-7507Fax Number: 304-747-3928Email: mawsons@ucarb.com

Vice Chair: James WatkinsUniversity of MassachusettsDepartment of Chemical EngineeringAmherst, MA 01003Telephone Number: 413-545-2569Fax Number: 413-545-1647Email: watkins@ecs.umass.edu

[117a] - Synthesis of Conductive Elastomeric Foams Using Supercritical Carbon Dioxide

Can Erkey (speaker) University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: 860-486-4601Fax: 860-486-2959 Email: cerkey@engr.uconn.edu

R. A. Weiss University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: (860)486-4698Fax: (860) 486-2959 Email: rweiss@mail.ims.uconn.edu

Suresh L. Shenoy University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: (860)486-5490Fax: (860)486-2959 Email: surete66@yahoo.com

Daniel Cohen University of Connecticut Department of Chemical Engineering

Storrs, CT 06269 Phone: (860)486-5490Fax: (860)486-2959 Email: dcohen@mail.ims.uconn.edu

Ipek Kaya University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: (860)486-5490Fax: (860)486-2959 Email: ipekk@hotmail.com

Abstract: Polypyrrole (PPy) is often combined or blended with conventional processable thermoplastic polymers such as polystyrene, polymethylmethacrylate, polyvinyl chloride, polyurethane etc. thus improving the processability and the mechanical properties of PPy while exploiting the intrinsic conductivity of PPy for various applications. Such conductive thermoplastic heterogeneous blends have generally been prepared by impregnating the host thermoplastic polymer with the oxidant such as ferric chloride, ferric perchlorate, ferric nitrate etc., followed by the in situ solution or vapor phase chemical oxidative polymerization of pyrrole in the polymer host. We have been concentrating our efforts on the development of an environmentally friendly synthesis by replacing the traditionally employed organic solvents such as methanol with supercritical carbon dioxide (SCCO2). The concentration of the oxidant in the fluid (SCCO2) phase is an important factor in the impregnation process. However the solubility of the traditionally employed oxidant, FeCl3 in SCCO2, is extremely low thereby hindering the impregnation of the oxidant into the foam. An oxidant like the ferric salt of trifluoromethane sulfonate (ferric triflate) is expected to have better solubility in SCCO2 than FeCl3. It has also been demonstrated that ferric triflate is an effective oxidant for the polymerization of pyrrole. However initial results suggested that the solubility of the ferric triflate in SCCO2 did not improve significantly inspite the presence of the CO2-philic fluorine groups. This together with the inability of SCCO2 to swell PU foam resulted in poor penetration of the oxidant into the foam. As a result a small amount of organic solvent also known as entrainer (cosolvent) was added to the SCCO2.

The addition of ethanol dramatically improves the solubility of the ferric triflate in SCCO2. The solubility of pure ferric triflate in SCCO2 increases from ~ 0.02 wt % to about 2.3 wt % at 35°C and 2500 psi on the addition of only 1.32 % ethanol by volume.Furthermore;(1) Addition of small amounts of ethanol, in fact as little as 0.2 vol % in SCCO2 during the impregnation process results in an increase of the electrical conductivity of the composite foam by almost 4 orders of magnitude. Using a higher entrainer concentration is detrimental to the conductivity of the resulting foams. The conductivity of the composite foam prepared using 1.32 vol % of ethanol is about four orders of magnitude lower than the maximum obtained value. However the PPy wt % in the PU/PPy composite foam follows the expected trend. The PPy concentration in the composite foam increases by an order of magnitude (from 0.3 wt % to 3.3 wt %) on addition of as little as 0.2 vol % ethanol in the SCCO2. Further increase in the entrainer concentration results in only a slow increase in the wt % of Ppy in the composite foam.(2) For a fixed ethanol concentration of 1.32 vol % the conductivity increases dramatically for time of impregnation of upto 5 hrs. Further exposure to the oxidant solution decreases the conductivity slowly at first and then dramatically. For times of impregnation upto 15 hrs, the wt % of PPy in the composite foam increases in more or less linear fashion. In contrast to the trends seen for lower impregnation times, the concentration of PPy in the composite foam for longer impregnation more or less stays constant.

Small differences in the overall distribution of the PPy particles in the foams corresponding to the conditions of preparation can translate into huge differences in the measured conductivity. The composite foam impregnated for 5 hrs clearly shows a significant surface coating of PPy. On the other hand, for longer times of impregnation the surface PPy layer appears to be significantly reduced. This is possibly due to the penetration of polypyrrole into the foam resulting in a distribution of PPy over a wider area of the composite foam. For lower times of impregnation, the PPy is concentrated in a thin layer thereby improving the probability of the formation of a continuous conduction pathway. The data demonstrates a one to one correspondence between the S/Fe ratio and the experimentally measured surface conductivities. Composite foams with high S/Fe ratios exhibit higher levels of conductivity. In principle the S peak may arise from the dopant ions in the form of Fe(CF3SO3)-4 or the residual redox byproduct, Fe(CF3SO3)2 that has not been completely removed by the extraction process. Hence the comparison of the S/Fe ratios is more appropriate. Lower S/Fe ratios on the surface of the foams may be due to presence of the redox byproducts only, while higher S/Fe ratios can be presumed to occur due to the presence of dopant ions and residual redox byproducts. However interpretation of this data (S/Fe) can lead to erroneous conclusions without understanding the mechanism of conduction and the role played by the dopant ions, namely, (CF3SO3)-1 and Fe(CF3SO3)-4. Another possible reason for the reduction in the conductivity of the PPy maybe the reduction of the conjugation length caused by structural changes (appearance of carbonyl peaks in FTIR) occurring in the PPy. Such effects have been observed previously during the polymerization of pyrrole using strong oxidizing agents such as Fe(ClO4)3, Fe(NO3)3, FeCl3 etc. It has been demonstrated that there exists an optimum pyrrole/oxidant ratio to obtain PPy exhibiting high levels of conductivity. For lower values of the ratio (corresponding to higher oxidant concentration), there is a decrease in the intrinsic conductivity of PPy due to the destruction of the P electron system resulting in a reduction of the effective conjugation length of PPy and hence poor conductivity. The resulting PPy spectra show a carbonyl stretching band at 1740 cm-1 and an N-H wagging vibration at 1556 cm-1. For samples prepared using an impregnation time of 24 hrs, both bands (C=O and N-H) are stronger than the corresponding peaks for impregnation times of 5 hrs. The presence of stronger N-H peak is hardly surprising given higher concentration of PPy in the foam. We believe the presence of the carbonyl groups can result in a reduction in the conductivity of the foams.

[117b] - Spin Coating and Photolithography Using Liquid and Supercritical Carbon Dioxide

Erik N. Hoggan (speaker) North Carolina State University 1017 Main Campus Dr. Suite 3500 Raleigh, NC 27606 Phone: 919.513.1654Fax: 919.513.1655 Email: enhoggan@eos.ncsu.edu

Devin Flowers

University of North Carolina, Chapel Hill Venable and Kenan Laboratories CB #3290 Chapel Hill, NC 27599 Phone: 919.962.1346

Joseph M. DeSimone University of North Carolina, Chapel Hill CB#3290, Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

Ruben Carbonell North Carolina State University 1017 Main Campus Drive Centennial Campus, Partner's Building I Raleigh, NC 27695-7006 Phone: 919-515-5118Fax: 919-515-5831 Email: ruben@ncsu.edu

Abstract: MotivationThe conventional manufacturing of integrated circuits utilizes two solvent intensive steps, spin coating of a photoresist layer and the development of the image after exposure. The complexity of modern semiconductor devices necessitates large numbers of material layers, thus requiring these solvent intensive steps to be repeated 30 times or more in the processing of a single wafer. This creates vast amounts of solvent waste. The health and environmental hazards posed by these solvents has led to increased research on alternative processing solvents. One promising alternative is carbon dioxide. In addition to its well known environmental and cost advantages, CO2 has a very low viscosity and surface tension, thus improving the transport of resists from very small crevices. This may be extremely valuable as feature sizes continue to shrink below 0.18 mm.Despite the promise of CO2, it has not become widely used due to several challenges. First, conventional photoresists are not appreciably soluble in CO2, thus any attempt at solvent replacement must also include the discovery of new resist materials. Recently, several groups have conducted work in this area, demonstrating the feasibility of using CO2 solely for image development. Second, in order to use CO2 as a solvent for spin coating, a high-pressure coating chamber with a uniformly rotating chuck must be constructed. Third, to spin coat from CO2, the polymeric resists must be soluble in liquid CO2 at vapor pressure, placing further restrictions on the choice of resist materials. To date, the authors know of no research that has successfully addressed these latter two challenges.

ExperimentalA series of random copolymers of 1H,1H-perfluorooctyl methacrylate (FOMA) and t-butyl methacrylate (TBM) were synthesized as negative resists for deep-UV lithography. Solutions of PFOMA-r-TBM and a CO2 soluble photoacid generator were spun into films on 125 mm Si wafers using liquid CO2 as the only solvent . Upon irradiation, the photoacid generator produces an acid which catalyzes the release of isobutylene from TBM, leaving an insoluble methacrylic acid (MAA).In an effort to maximize film quality, films were spun under a variety of conditions. The effect of rotational speed, solution concentration, and evaporation rate were investigated. Prior to spinning, solution viscosities were determined using a high pressure falling cylinder viscometer. Films were spun on 125 mm Si wafers. Film thickness and uniformity were measured with a profilometer.Recent experiments have focused on evaporative spinning controlled via either small induced pressure differentials (5 ? 20 psi) or the addition of inert gases (He, N2) into the spinning chamber. The introduction of controlled evaporation into the process yielded significantly better films than were achieved in initial studies. For 1 mm films cast using controlled evaporation during the spinning, polymer thickness varied 6% from the center to the edge of a 5" wafer. Work on image development is ongoing.

[117c] - Reactive Deposition of Metal Thin Films via Reduction from Supercritical Carbon Dioxide Solution

James Watkins University of Massachusetts Department of Chemical Engineering Amherst, MA 01003 Phone: 413-545-2569Fax: 413-545-1647 Email: watkins@ecs.umass.edu

Jason M. Blackburn (speaker) University of Massachusetts 142 Goessmann Laboratory Amherst, TN 01002 Phone: (413) 545-9685Fax: (413) 545-1647 Email: jblackbu@ecs.umass.edu

David P. Long University of Massachusetts 142 Goessmann Lab Amherst, MA 01002 Phone: (413) 577-1090Fax: (413) 545-1647 Email: dlong@chemistry.umass.edu

Abstract: The demand for high performance devices has led to the need to deposit metal onto substrates with decreasing feature size (<150 nm) and increasing aspect ratios. Various metal deposition techniques are presently used including electrolytic plating and chemical vapor deposition (CVD). However, both processes have drawbacks and limitations, which include the generation of hazardous wastewater streams in electrolytic plating and the requirement of precursor volatility in CVD. The precursor volatility constraints in CVD often lead to mass transfer limitations that preclude the uniform, void free filling of high aspect ratio features. Chemical fluid deposition (CFD) is the chemical reduction of an organometallic precursor dissolved in supercritical carbon dioxide. We previously validated the process for the deposition of high purity platinum, palladium, rhodium, nickel, and gold in batch processes. Here, uniform, void free filling of high aspect ratio features via a continuous CFD process is demonstrated by the deposition of nickel and platinum onto silicon substrates containing features as small as 100 nm with 10:1 height to width ratios. The growth rate of the films with respect to key process variables is also reported.

[117d] - Metal Oxide Surface Modification in Supercritical Carbon Dioxide

James R. Combes (speaker) Xerox Research Centre of Canada 2660 Speakman Drive Mississauga, Ontario L5K 2L1 Canada Phone: (905)823-7091Fax: (905)822-7022 Email: Jimmy.Combes@crt.xerox.com

Carl P. Tripp Surface Science and Technology Orono, Maine 04469 Phone: (207)581-2235Fax: (207)581-2255 Email: ctripp@maine.maine.edu Abstract: Infrared spectroscopy was used to probe the interaction of CO2 and the reaction of hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS) under supercritical fluid (SCF) solution conditions with a fumed silica. CO2 is shown to be an effective and environmentally friendly solvent and to behave quite differently from traditional non-aqueous solvents (i.e., carbon tetrachloride, toluene and cyclohexane) with respect to interactions with the adsorbed layer of water on the surface. A dry silica easily extracts and adsorbs the residual water present in these non-aqueous solvents whereas, in contrast, a dry silica remains dry when placed in contact with the SCF CO2. Moreover, the CO2 extracts the adsorbed water from wet silica. The SCF solvent extracts more surface water into the fluid phase with increasing density and repeated extraction cycles with SCF CO2 results in the removal of all water from the surface. The interaction of SCF CO2 with the hydroxyl groups was studied using deuterated silica. Using a dry or wet deuterated silica, the physisorption of CO2 with the isolated SiOD groups is shown to be weak in nature and of the same magnitude as that measured in CCl4. The SiOD band at 2762 cm-1 is completely shifted to 2710 cm-1 at relatively low pressures of CO2 (5 bar) and remains shifted with increasing amounts of CO2 up to the highest pressures studied (200 bar). CO2 is demonstrated to be a versatile and effective solvent medium for chemical surface modifications and surface treatments in general.

[117f] - Steric Stabilization of Nanocrystals in Supercritical Fluids

Parag S. Shah (speaker) University of Texas, Austin Department of Chemical Engineering Austin, TX 78712 Phone: 512-471-9602Email: pshah@che.utexas.edu

Justin D. Holmes University College Cork Department of Chemistry Cork, 00000 Ireland Phone: +353 21 903608Email: j.holmes@bureau.ucc.ie

R. Christopher Doty University of Texas, Austin Department of Chemical Engineering Austin, TX 78712 Phone: 512-471-2828Email: doty@che.utexas.edu

Keith P. Johnston University of Texas, Austin 26th & Speedway Austin, TX 78712 Phone: 512 471 4617Fax: 512 475 1062 Email: kpj@ce.utexas.edu

Brian A. Korgel University of Texas Department of Chemical Engineering Austin, TX 78712-1062 Phone: 512-471-5633

Fax: 512-471-7060 Email: korgel@che.utexas.edu

Abstract: Nanocrystals, 20-100 A in diameter, exhibit unique size-dependent optical, catalytic, magnetic, and electronic properties compared to their bulk counterparts. These properties could enhance a variety of technologies-such as coatings, environmental, chemical processing, medical, electronics, and sensing applications. The use of supercritical fluids for nanocrystal synthesis is of great interest due to the environmental and processing advantages over conventional solvents. By taking advantage of the unique solvation characteristics of supercritical fluids, specifically the ability to alter density through changes in pressure and temperature, it is possible to improve many aspects of nanocrystal processing-such as separations, synthesis and self-assembly.

We have explored the use of a supercritical solvent to disperse hydrocarbon-coated nanocrystals and to isolate monodisperse particle samples by altering the solvent quality through changes in the pressure and temperature. Using a supercritical fluid allows reversible and tunable particle aggregation by controlling solvent density, making it a possible vehicle for size selective precipitation. Nanocrystals coated with fluorinated ligands were synthesized in both supercritical CO2 and ambient solvents using an arrested growth method. The ligands provide a low cohesive energy coating with strong dipole interactions, allowing the nanocrystals to disperse readily in carbon dioxide and polar solvents such as acetone. We present the first example of nanocrystals sterically stabilized in pure CO2. Compared to hydrocarbon stabilized nanocrystals, nanocrystals coated with the fluorinated ligands exhibit a reduced electron mean free path most likely due to the increased electronegativity of the fluorinated ligands. We will discuss our current understanding of the design aspect of ligands with respect to supercritical fluid compatibility.

[117g] - Monitoring SAS Process by UV-vis Spectroscopy

Nicola Elvassore University of Padova via Marzolo, 9 Padova, 35100 Italy Phone: 39 049 8275472Fax: 39 049 8275461 Email: nelvas@polochi.cheg.unipd.it

Mara Buzzi University of Padova via Marzolo, 9 Padova, 35100 Italy Phone: 39 049 8275472Email: buzzi01@iol.it

Alberto Bertucco (speaker) University of Padova via Marzolo, 9 Padova, 35131 Italy Phone: 39 049 8275457Fax: 39 049 8275461 Email: bebo@polochi.cheg.unipd.it

Vito Di Noto University of Padova via Marzolo, 1 Padova, 35131 Italy Phone: 39 049 8275229Email: dinoto@ux1.unipd.it

Abstract: The interest towards supercritical anti-solvent precipitation (SAS) processes is growing in many fields, especially for pharmaceutical applications. In order to understand the complex phenomena involved in SAS, it is essential to know the behavior of solvent-solute mixtures as a function of anti-solvent pressure. In this work, such a problem has been addressed by means of UV-vis spectroscopy. The solvent expansion and solute precipitation were carried out in a pressure cell equipped with sapphire windows and UV-vis spectra provided in situ measurement of absorbance of substances present in the liquid phase. Two types of inorganic compounds were used as markers to monitor the solvent volumetric expansion. One of these was used for polar solvents and the second for no-polar environmental. This method was applied to a number of solvents at different temperatures in the range of 25?C and 40?C and pressure up to 70 bar. The results obtained well compare with literature data available. Same experiments were performed in the presence of a solute in order to evaluate the change of solubility with pressure. Lisozyme and PLA were studied as protein and bio-polymer model molecules. The kinetic of precipitation was also investigated by measuring as function of time the light scattering of micro-particles at a wavelength 600 nm. Nucleation, agglomeration and flocculation phenomena were discussed on base of spectra analysis. The proposed technique appears to be very promising for the theoretical understanding of SAS and for promoting the development of SAS application at the industrial stage.

[117h] - Application of RESS Model to the Subsonic and Supersonic Regions

Markus Weber (speaker) Clemson University Dept of Chemical Engineering Clemson, SC 29634-0909 Phone: 865-656-0106

Fax: 864-656-0784 Email: mweber@ces.clemson.edu

Jack R. Edwards North Carolina State University Campus Box 7910 Raleigh, North Carolina 27695-7910 Phone: (919) 515 5264Fax: (919) 515 7968 Email: jredwards@eos.ncsu.edu

Kevin Boulware Clemson University Dept of Chemical Engineering Clemson, SC 29634-0909 Phone: 864-656-3056Fax: 864-656-0784

Mark C. Thies Clemson University Dept of Chemical Engineering Clemson, SC 29634-0909 Phone: 864-656-3056Fax: 865-656-0784 Email: mcths@clemson.edu Abstract: Although the Rapid Expansion of Supercritical Solutions (RESS) was initially envisioned as a new technology for manufacturing particles smaller than 100 nm (Krukonis, 1984), researchers typically obtain micron-sized particles (e.g., Blasig, 2000). Aerosol dynamic simulations of the subsonic part of the expansion (Weber et al., 2000) and the recent measurements of Ginosar et al. (2000) suggest that the main part of the particle growth occurs in the highly turbulent flow field of the freely expanding supersonic jet. Previous modeling work on particle formation and growth in the supersonic and transonic region has neglected the influence of coagulation (Ksibi, 1995) or has been based on the assumption of unrealistically high equilibrium concentrations at stagnation conditions (Shaub et al., 1995).

More recently, computer models for the simulation of the RESS process have been presented by Carbonell and co-workers (Chernyak et al., 2000). We have adapted this method by extending our current one-dimensional model and by combining it with profiles calculated in a two-dimensional grid. For the system phenanthrene/CO2, we carried out complete simulations of particle formation and growth for pre-expansion pressures 140 bar < Po < 260 bar and temperatures 343 K < To < 403 K. The thermodynamic relationships for this mixture were calculated using the Carnahan-Starling-van der Waals and Peng-Robinson equations of state, and results were compared. In order to solve the aerosol dynamic equation, we chose the sectional method, which can represent more complex (e.g., bimodal) particle size distributions. The differences in the simulation results for different equations of state can be explained by the differences in predicted solubility. In addition, our results provide a consistent interpretation of experimental results obtained both in our laboratory and elsewhere for the production of polymeric (Blasig, 2000) and organic (Ginosar, 2000) particles.

[118] - Materials Processing with Supercritical Fluids IIChair: Christopher RobertsAuburn UniversityDepartment of Chemical EngineeringAuburn, AL 36849Telephone Number: 334-844-2036Fax Number: 334-844-2063Email: croberts@eng.auburn.edu

Vice Chair: Robert EnickUniversity of PittsburghDepartment of Chemical And Petroleum Engineering1259 Benedum HallPittsburgh, PA 15261Telephone Number: 412-624-9649Fax Number: 412-624-9639Email: enick@engrng.pitt.edu

[118a] - Liquid Carbon Dioxide as a Medium for Polymeric Coatings

Brian J. Novick (speaker) North Carolina State University Partners I, Suite 3500, 1017 Main Campus Drive Raleigh, NC 27606 Phone: (919) 513-1654Fax: (919) 513-1655 Email: bjnovick@eos.ncsu.edu

Ruben Carbonell North Carolina State University 1017 Main Campus Drive Centennial Campus, Partner's Building I Raleigh, NC 27695-7006

Phone: 919-515-5118Fax: 919-515-5831 Email: ruben@ncsu.edu

Joseph M. DeSimone University of North Carolina, Chapel Hill CB#3290, Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

Abstract: The coating of polymeric materials by free meniscus, spin, pre-metered, and self-metered coating processes requires large quantities of organic or aqueous solvents. One environmentally responsible alternative is to use liquefied carbon dioxide as the carrier solvent. Compressed carbon dioxide may offer many advantages over conventional solvents. Some of these benefits include tunability of physical properties, increased transport of material, and better penetration into porous material.

A second generation high-pressure apparatus has been created that uses simultaneous drainage and evaporation to deposit films from compressed gases. The lubrication of magnetic hard disks is one process in which the standard solvent can be replaced by carbon dioxide. Current lubricants consist of liquid carbon dioxide soluble perfluoropolyethers and are currently applied by dip coating from fluorinated solvents. The apparatus is capable of coating disks relevant to the hard disk industry as well as other substrates with diameters as large as 5 inches. Withdrawal velocities can be as high as 50 mm/s and evaporation rates as large as 1.2 mg/cm2-s.

Polymeric films of the soluble hard disk lubricant, Fomblin Zdol, have been deposited thinner than 40 angstroms onto 4-inch diameter type <100> silicon wafer substrates. Film thickness increases linearly with an increase in polymer concentration and nonlinearly with an increase in withdrawal velocity or evaporation driving force. A small change in coater temperature due to evaporation can cause a large change in evaporation rate and the physical properties of the CO2/polymer solution. Furthermore, it was found that pressurization modifies the silicon wafer native oxide.

Experiments are being performed to study the uniformity of polymer films deposited onto 4 inch diameter silicon wafer substrates. Theoretical modeling of the evaporation and deposition process as well as the use of this method for other polymeric materials is being investigated. Future work will include adaptation of the high-pressure dip coater for colloidal materials and other free meniscus configurations.

[118b] - Implantation of Various Solids into Polymer Matrices Using Liquid and Supercritical Carbon Dioxide

Randy D. Weinstein (speaker) Villanova University Department of Chemical Engineering Villanova, PA 19085 Phone: 610-519-4954Fax: 610-519-7354 Email: randy.weinstein@villanova.edu

Christopher M. Ott Villanova University 800 Lancaster Ave. Department of Chemical Engineering Villanova, PA 19085 Phone: 610-519-4950

Abstract: Traditional methods of introducing pharmaceuticals into the human body include eye drops, ointments, intravenous solutions, inhalation of aerosols, and edible pills and liquids. These introduction methods often cause the drug concentration in the bloodstream to rise quickly, peak, and then decline. More recently, novel drug delivery methods have begun to be developed and brought into practice that can control the release of drugs to maintain a fixed concentration in the bloodstream for a predetermined duration. By maintaining a constant therapeutic drug concentration in the body, controlled drug releases can increase patient comfort, reduce care requirements, and preserve compounds that are quickly destroyed by the body. One new method for controlled drug release employs the entrapment of drugs in polymeric matrices. These matrices can be small vesicles and injected into the bloodstream, they may be larger and implanted in desired bodily compartments, or they may be used for controlled transdermal release. These biocompatible polymer matrices can control the release of desired drug via diffusion through the polymer and/or the polymer may degrade in the body allowing for the entrapped drug to be released. Proper design, synthesis, and drug loading of these polymer matrices are essential to obtain desired drug delivery.

This investigation explored a variety of polymers and solids for implantation. Carbon dioxide saturated with the desired solid was passed through polymer beds and break through curves were created as a function of temperature, pressure/density, and solvent flow rate. The effects of function groups on the solids as well as the polymer molecular weight and composition on the polymer loading were found. Optimal conditions for the creation of drug delivery devices were identified. The uniformity of implantation was explored. Mass transfer models were developed in attempts to accurately model and predict drug loading on polymers.

[118c] - Processing Polymeric Species in Supercritical Fluids

Frederick S. Mandel (speaker) FERRO Corporation 7500 East Pleasant Valley Road Independence, OH 44131 Phone: 216 750 6650Fax: 216 750 6915 Email: mandel@ferro.com

J. Don Wang FERRO Corporation 7500 East Pleasant Valley Road Independence, OH 44131 Phone: 216 750 7614Fax: 216 750 6915 Email: D.wang@ferro.com Abstract: Supercritical fluid carbon dioxide is used as the solvent of choice in an process, to produce specialty materials containing polymeric substances which include powder coatings, new polymers, pigments, polymer additives, and a series of temperature sensitive bio-materials. The process to be described is automated and consists primarily of a Supercritical Fluid aided mixing operation and an atomization unit operation. The process was verified, on several scales of laboratory equipment, pilot plants and commercial scale all utilizing unique reactor design equipped with proprietary components such as the agitator, mechanical seals, heating/cooling jacket, wall surface, flush valve, cyclone atomization chamber and its control logic. The products often demonstrated superior dispersion properties and performed equally or better than elevated temperature produced materials. In some cases, the materials so produced possess unique properties, e.g., porosity, particle size distribution, loading, and uniformity that allow them to be used in new, innovative applications. Polymers amenable to Supercritical Fluid that will be discussed include thermosets, thermoplastics and bio-polymers. Particle architecture for specialty material usage varies widely between applications. Successful novel pre-percolated and percolated examples are given

[118d] - In-Situ Spectroscopic Characterization of Modifiers in the Supercritical Carbon Dioxide and Polymer Phases

Yiqing Wang (speaker) Ohio State University 140 West 19th Ave. Columbus, OH 43210 Phone: 614-292-9085Fax: 614-292-3769 Email: wang.384@osu.edu Chihae Yang

Otterbein College 150 W. Main St. Westerville, OH 43081 Phone: 614-823-1666Email: cyang@otterbein.edu

Hongbo Li The Ohio State University Rm 125, 140 West 19th Ave. Columbus, OH 43210 Phone: (614) 292-9085Fax: (614) 292 3769 Email: lih@er6.eng.ohio-state.edu

David L. Tomasko Ohio State University 140, W. 19th. Ave., Koffolt Lab Columbus, OH 43210 Phone: 614-292-4249Fax: 614-292-3769 Email: tomasko@che.eng.ohio-state.edu Abstract: The feasibility of using polymeric materials in personal care products, synthetic fibers or biomedical devices heavily rely on the surface properties of these materials. We are exploring the modification of polymer surface properties by impregnating surface active modifiers into polymer substrates using supercritical carbon dioxide (SC-CO2) as a benign solvent. The process is similar to a supercritical dying process, which is based on the facts that SC-CO2 can reversibly swell glassy and rubbery polymers and it allows diffusion of the modifier into the polymer followed by entrapment once the pressure is released. Differently from the dying process, the surface modification targets at maximizing the loading of modifiers on surface by optimizing the operational conditions such as pressure, temperature and contact time.

The understanding of the kinetics and equilibrium partitioning of modifiers in the process, as well as the distribution of the modifiers in polymer substrates are crucial for this technique. Fluorescence and UV-Vis absorption spectroscopy have been intensively used to reveal the inhomogeneous of supercritical fluids. We will use both of them as the main analytical methods to investigate the molecular interactions between SC-CO2 /modifier/polymer and the process kinetics. We modified polypropylene surfaces with PET/POET (polyethylene terephtalate/polyoxyethylene terephtalate), a polymeric surfactant that is used in both detergent and textile industries to enhance surface wettability and impart oily soil release to polyester fabrics. PET/POET is also a fluorophore that has been well characterized in aqueous based applications. The steady state absorption and emission spectra of PET/POET in SC-CO2 and polymer phases will be collected to reveal the structure and conformation of PET/POET and the effect of the solvent density.

[118e] - Microcellular Foams of Polymer Blends in Supercritical Carbon Dioxide: Batch versus Continuous Processing

Srinivas Siripurapu (speaker) North Carolina State University 113 Riddick Labs Box 7905 Raleigh, NC 27695 Phone: 919 - 515 1654

Fax: 919 - 515 1655 Email: ssiripu@unity.ncsu.edu

Joseph R. Royer North Carolina State University 1017 Main Campus Drive, Suite 3500 Raleigh, NC 27616 Phone: 919-513-1654Fax: 919-513-1655 Email: jrroyer@eos.ncsu.edu

Joseph M. DeSimone University of North Carolina, Chapel Hill CB#3290, Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

Richard J. Spontak North Carolina State University 113 Riddick Labs Box 7905 Raleigh, NC 27606 Phone: 919 - 515 4200Email: Rich_Spontak@ncsu.edu

Saad A. Khan North Carolina State University 113 Riddick Raleigh, NC 27695-7905 Phone: 1-919-515-4519Fax: 919-515-3465 Email: khan@eos.ncsu.edu

Abstract: Considerable interest has recently been evoked in the generation of microcellular polymeric foams (MPFs) in supercritical carbon dioxide (scCO2) because its environmentally benign nature as a blowing agent is a welcome respite to the hazardous fluorocarbon blowing agents used conventionally in the foaming industry. A typical microcellular foaming process involves dissolution of scCO2 (typically less than 8 wt%) in a polymer matrix. A sudden pressure quench induces thermodynamic instability between the polymer and scCO2 and promotes the rapid nucleation of numerous scCO2 bubbles, which grow to become discrete microvoids (cells) remaining within the MPF. Generally speaking, MPFs possess a cell size less than 10 mm and a cell density greater than 109 cells/cm3. The microcellular foaming technology competes strongly with both conventional foams and solid plastics. Primary advantages of MPFs include lower densities resulting in lower product weights, higher strength/weight ratios and improved thermal insulation characteristics.

Most studies reported on microcellular plastics produced in this fashion involve batch foaming. More recently, a continuous extrusion process has been proposed to avoid the lengthy time periods required to saturate the polymer with the blowing agent. These two foaming processes have substantially different tunable operating parameters, in which case a comparative study is necessary to identify and possibly combine the advantages of both processes. We have constructed experimental systems for batch and continuous extrusion processes in scCO2 with superior process control relative to many comparable systems that are currently employed for microcellular foam generation. Foaming experiments have been conducted using polystyrene (PS) and poly(methyl methacrylate) (PMMA) homopolymers as model materials. The morphologies and mechanical properties of microcellular foams prepared by both processes have been analyzed in terms of cell size distribution, foam density and impact strength. The above studies have also been extended to suggest a process strategy for generation of MPFs of poly(vinylidene fluoride) (PVDF), a semicrystalline polymer. We show that by using judiciously selected blends in which phase homogeneity is retained, improved MPF morphologies can be obtained as compared to the semicrystalline polymer alone. PVDF-PMMA blends over a broad concentration range are highly amenable to microcellular foaming, showing vast improvements over neat PVDF. These results are quantitatively compared for foams produced at different operating conditions in batch and continuous mode.

[118f] - Rheology of Molten PMMA with Dissolved Carbon Dioxide

Joseph M. Smolinski Wayne State University 5050 Anthony Wayne Drive Detroit, MI 48202 Phone: 313-577-5772Fax: 313-577-3810 Email: jsmol@che.eng.wayne.edu

Charles W. Manke (speaker) Wayne State University 5050 Anthony Wayne Drive Detroit, MI 48202 Phone: 313-577-3849Fax: 313-577-3810 Email: cmanke@che.eng.wayne.edu

Esin Gulari Wayne State University Department of Chemical Engineering Detroit, MI 48202

Phone: 313-577-3767Fax: 313-577-3810 Email: egulari@che.eng.wayne.edu

Abstract: The viscosity of molten polymethylmethacrylate (PMMA) with dissolved carbon dioxide has been measured as a function of shear rate, employing a newly designed high-pressure capillary rheometer. Viscosity data are reported for temperatures ranging from 130-175 C, shear rates from 10 to 5000 1/s, and up to 10 wt% dissolved carbon dioxide. As in earlier studies with the polystyrene-carbon dioxide system, the viscosity curves for PMMA with various amounts of dissolved carbon dioxide are consolidated into a master viscosity curve using viscoelastic scaling factors to represent the effects of dissolved carbon dioxide content. An alternative interpretation of the viscosity data in terms of the effect of dissolved carbon dioxide on the glass transition temperature is also presented. In addition to the PMMA viscosity measurements, details of the new capillary rheometer design will be discussed. The new rheometer can operate at backpressures up to about 20 Mpa, which significantly extends the maximum carbon dioxide solubilites that can be achieved in the experiments.

[118g] - Extrusion of Polystyrene Microcellular Foam with Supercritical CO2

Xiangmin Han (speaker) Ohio State University 140, W. 19th Ave., Koffolt Lab Columbus, OH 43210 Phone: 614-688-3400Fax: 614-292-3769 Email: han.87@osu.edu

Kurt W. Koelling Ohio State University 140 w19th ave Columbus, OH 43210 Phone: (614)292-2256Fax: (614)292-3769 Email: koelling.1@osu.edu

David L. Tomasko Ohio State University 140, W. 19th. Ave., Koffolt Lab Columbus, OH 43210 Phone: 614-292-4249Fax: 614-292-3769 Email: tomasko@che.eng.ohio-state.edu

L. James Lee Ohio State University 121 Koffolt Lab, 140 W. 19th Ave. Columbus, OH 43210 Phone: (614) 292-2408Fax: (614) 292-3769 Email: lee.31@osu.edu Abstract: Microcellular foams are usually characterized by cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 m m. Because they exhibit relatively high mechanical, thermal and electrical performance as saving raw material, there are many potential innovative applications. These include food packaging, building insulation, and others. Supercritical CO2 is an environmentally friendly foaming agent which has both liquid-like solubility and gas-like diffusivity. For any foaming process, a thermodynamic instability, either a sudden pressure drop or a temperature increase, is required to induce nucleation from the well-mixed, one phase CO2/polymer solution. Then cell growth is often controlled by the temperature or the diffusivity of the gas in the polymer.

Compared with the batch process, continuous extrusion microcellular foaming has several advantages, for instance, short residence time, and high productivity. However, the extrusion foaming process is very complex as well. The design of mixing elements is critical to the formation of the one-phase CO2/polymer solution and the design of the die determines how large a pressure drop can be created. The physical properties of the solution, such as the non-Newtonian viscosity, glass transition temperature, surface tension, CO2 solubility and diffusivity, greatly depend on the processing conditions such as the barrel and die temperatures, and the screw rotation speed.

Our goal is to obtain low bulk density and uniform micron-size cells. Fundamental research is also proposed to simulate the flow behavior, the nucleation and the cell growth by investigating the relation between the physical properties and the processing conditions.

Experiments have been performed on a two-stage single screw extruder (HAAKE 250P) with a very small die which has a diameter of 0.5mm and a length of 10mm. A syringe pump was applied to compress CO2 and then inject it into the extruder barrel. The flow rate of CO2 was controlled by a needle valve and the weight ratio of CO2 to PS was calculated according to flow rates of both the gas and the polymer melt. After efficient mixing by the screw and one static mixer, the resulting one-phase solution flows through the die, where microcells nucleate due to the quick and large pressure decrease. Cell growth was controlled by reducing the extrudate temperature.

At present, foams with a diameter smaller than 15 m m and cell density greater than 5´ 108 cells/cm3 has been manufactured by the process above. With a decrease in the die temperature, both the cell size and the cell density increase. With an increase of the screw rotation speed, the cell size decreases and the cell density increases. Therefore, it is desirable to foam microcellular cells at a low die temperature and a high screw rotation speed.

The mixing of CO2 in PS was monitored on-line by connecting a view cell between the static mixer and the die, which also

allowed determination of CO2 solubility. A series of experimental results at high temperatures and high pressures were obtained. Based on these results and the Sanchez-Lacombe equation of state, the solubility of CO2 in polystyrene was calculated from 20 to 260° C under pressures from 0.69 to 20 MPa. The relation between CO2 content, temperature and saturation pressure creates a surface on which nucleation occurs as conditions in the die change. This surface helps guide experimentation.

By applying the FLUENT computational code and assuming there is no phase separation, the contraction flow in the extrusion die was simulated and the pressure and temperature distributions were obtained. The CO2 saturation content was then calculated according to the local pressure along the center line of the die. The position that the solution becomes supersaturated can be treated as the point where the microcell nucleation begins. It was observed that with increasing CO2 content in the melt, the microcells begin to nucleate sooner. Both the magnitude and the rate of the pressure drop decrease with increasing CO2 content.

[118h] - Novel High Pressure Magnetically-Levitated Sphere Rheometry: Polymer Melt Rheology Plasticized by Liquid and Supercritical Carbon Dioxide

Joseph R. Royer (speaker) North Carolina State University 1017 Main Campus Drive, Suite 3500 Raleigh, NC 27616 Phone: 919-513-1654Fax: 919-513-1655 Email: jrroyer@eos.ncsu.edu

Mireille Adam University of North Carolina, Chapel Hill CB#3290 Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-8904Fax: 919-962-5467 Email: adam@net.chem.unc.edu

Joseph M. DeSimone University of North Carolina, Chapel Hill CB#3290, Venable and Kenan Laboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

Saad A. Khan North Carolina State University 113 Riddick Raleigh, NC 27695-7905 Phone: 1-919-515-4519Fax: 919-515-3465 Email: khan@eos.ncsu.edu Abstract: In polymer processing such as extrusion, synthesis and pumping, the use of polymers with high viscosities can become energy intensive. Methods of lowering the fluid properties of a polymer are often employed to reduce energy cost, improve product specifications, or simply to modify the process of interest. One of the most utilized techniques for modifying a polymer's physical properties is plasticization. Unfortunately, plasticizers used in industry today usually are difficult to remove from the product and permanently alter their properties. This is undesirable in many applications and finding methods to selectively manipulate the concentration of a plasticizer in a polymer matrix, and to remove it entirely from the final product is essential. Supercritical carbon dioxide (scCO2) has been shown to be highly soluble in many polymer melts, an effective plasticizer, and can be easily removed.

This project focuses on the development a novel rheological device to measure the physical properties of polymer melts with dissolved carbon dioxide as well as polymer solutions in carbon dioxide. This system allows measurement of the viscosity of a polymer melt as a function of pressure, temperature, concentration, and shear rate, under constant pressure and constant concentration conditions. The device operates by measuring the difference in the magnetic intensity required to maintain the position of a levitated sphere while the fluid is at rest, and under a known flow field. In this presentation, the final device design and calibration will be discussed. Experimental results with poly(dimethyl-siloxane) in the presence of CO2 and at various pressures and temperatures will shown. The change in viscosity will be related to previous results on swelling of PDMS in CO2. Free volume models used to quantify the plasticization induced by dissolved CO2 will be examined in greater detail to determine the limits of their applicability.

[118i] - Characterization and Manipulation of Organic Particles Produced through Rapid Expansion of Supercritical CO2

Daniel M. Ginosar (speaker) Idaho Nat'l Engr. & Environmental Lab. P.O. Box 1625 Idaho Falls, ID 83415-2208 Phone: 208-526-9049

Fax: 208-526-8541 Email: dmg@inel.gov Kyle Coates Idaho Nat'l Engr. & Environmental Lab. PO Box 1625 Idaho Falls, ID 83415-2208

Phone: 208 526-6994

Ryan D. McMurtrey Idaho Nat'l Engr. & Environmental Lab. PO Box 1625 Idaho Falls, ID 83415-2208 Phone: 208 526-5156

Fax: 208 526-8541 Email: mcmurd@inel.gov W. David Swank Idaho Nat'l Engr. & Environmental Lab. P.O. Box 1625 Idaho Falls, ID 83415-2211 Phone: 208 526-1698

Fax: Email: T A Hyde Idaho National Engineering and Environmental Laboratory PO Box 1625 Idaho Falls, Idaho 83415-2218 Phone: 208 526-0986

Fax: 208 526-0690 Email: Hydeta@inel.gov H W Rollins Idaho National Engineering and Environmental Laboratory PO Box 1625 Idaho Falls, Idaho 83415-2208 Phone: 208 526-4066

Fax: Email:

Abstract: Rapid expansion of supercritical solutions (RESS) is a promising technology for the production of highly uniform fine particles and for microencapsulation. This technology has been explored for the production of both polar and non-polar solutes. However, the technology still needs further development due to difficulties associated with variations in particle size, nozzle plugging and scale-up issues.

The Idaho National Engineering and Environmental Laboratory (INEEL) has initiated an effort to understand the RESS phenomenon in a moderate scale system. The INEEL experimental system has continuous flow capabilities of 150 ml/min of liquefied gas with solute concentration control and measurement. Concentration of organic solute in the critical fluid prior to expansion is controlled and continuously monitored through on-line UV-vis spectrometry.

Various techniques for particle measurement are employed for online and offline particle size characterization. The system is equipped with an aerodynamic particle sizer integrated with a scanning mobility particle sizer, providing online particle measurement capabilities for aerodynamic diameters from 5 nm to 20 μm. A cascade impactor and diffusion battery are employed for confirmation of online measurements and collection of samples suitable for SEM imaging.

Current work is aimed at control of produced particle size and distribution. Stagnation temperature and pressure measurements in the flowfield and Schlieren imaging have been completed and will be discussed. Experimental apparatus, equipment considerations, and analytical techniques will be described. The relationship between particle size, distribution, and dissolved solute concentration, temperature, and orifice size will be discussed.

[119] - Supercritical Fluids for Foods and PharmaceuticalChair: Can ErkeyUniversity of ConnecticutDepartment of Chemical EngineeringStorrs, CT 06269Telephone Number: 860-486-4601Fax Number: 860-486-2959Email: cerkey@engr.uconn.edu

Vice Chair: Said SaimBoehringer Ingelheim175 Briar Ridge RdRidgefield, CT 06877Telephone Number: 203-798-4324Fax Number: 203-778-7666Email: ssaim@rdg.boehringer-ingelheim.com

[119a] - Thermodynamic Modeling of Near Critical Hydrogenation Processes

Esteban A. Brignole PLAPIQUI Camino La Carrindanga Km7 - CC 717 Bahia Blanca, 8000

Argentina Phone: 00-54291-861700Fax: 00-54291-861600 Email: prbrigno@criba.edu.ar

Selva Pereda PLAPIQUI Camino la Carrindaga Km 7- CC 717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: spereda@criba.edu.ar

Susana B. Bottini (speaker) PLAPIQUI Camino la Carrindanga Km 7 - CC 717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: prbottin@criba.edu.ar

Abstract: Catalytic hydrogenation processes are common in the food and pharmaceutical industry. When the substance to be hydrogenated is a liquid- as in the case of fatty oils, esters and alcohols- the reaction rate and selectivity are limited by the low solubility of hydrogen in the liquid substrate and the high mass transfer resistance in this phase.By the addition of an adequate supercritical cosolvent, the reactive mixture can be brought to a homogeneous supercritical phase, with great improvements in the reaction rate and the quality of the product (1). Potential cosolvents are carbon dioxide, ethane or propane.The selection of the cosolvent and the operating temperature and pressure requires a thermodynamic model suitable for the description of high pressure phase equilibria in mixtures asymmetric in molecular size.In previous work (2) it has been shown that the group contribution equation of state GC-EOS (3) can be extended to high molecular weight compounds if the size related parameter, i.e. the hard sphere diameter, is determined from data on infinite dilution activity coefficients of alkanes in the heavy component. In this way, good correlation and prediction of high-pressure phase equilibria is achieved.In the present work an extended version of the GC-EOS model ? the group contribution associating equation of state GCA-EOS (4) - is used to represent high pressure phase equilibria in ternary mixtures of hydrogen with supercritical gases (carbon dioxide, propane, ethane) and fatty oils, esters or alcohols. The definition of an associating hydroxyl OH group allows association effects in mixtures with alcohols to be taken into account. For each ternary system (hydrogen + cosolvent + substrate) the phase boundaries are predicted and the regions of one (supercritical), two (vapor-liquid and liquid-liquid) and three (liquid-liquid-vapor) coexisting phases are determined. Based on these phase diagrams, the temperatures and pressures for the operation of a homogeneous one-phase hydrogenation process can be explored.

References(1) Harrod M., Macher M-B., van den Hark S. And Moller P., Proc. CISF 99, Garda, Italy, pgs. 319-324, 1999(2) Bottini S.B., T. Fornari and E.A. Brignole, Fluid Phase Equilibria 158-160, 211-218, 1999(3) Skjold-Jorgensen S., Fluid Phase Equilibria 16, 317-351, 1984(4) Gros H.P., S.B. Bottini and E.A. Brignole, Fluid Phase Equilibria 116, 535-544, 1996

[119b] - Minimization of Drug Retention and Enhancement of Consistency in Drug Delivery by Supercritical Fluid Extraction of Mold Lubricant from Inhalation Capsules

Said Saim (speaker) Boehringer Ingelheim 175 Briar Ridge Rd Ridgefield, CT 06877 Phone: 203-798-4324Fax: 203-778-7666 Email: ssaim@rdg.boehringer-ingelheim.com

Stephen T. Horhota Boehringer Ingelheim 175 Briar Ridge rd Ridgefield, CT 06877 Phone: 203-798-5258Email: shorhota@rdg.boehringer-ingelheim.com

Abstract: The quantity and consistency of drug delivery from dry powder inhalation devices that incorporate a pre-measured dose in a capsule of gelatin or other compatible material can be affected by mold release lubricants used in the manufacturing of capsule shells. This presentation describes a novel method employing supercritical CO2 for selective extraction of lubricant from the internal surface of assembled capsule shells, as provided by the manufacturer. The method takes advantage of the tunable compressibility of near-critical CO2 to overcome the slow diffusion of lubricant from the capsule internal surface to the capsule CO2 phase and from the capsule CO2 phase to the bulk CO2 phase. Capsules were successfully extracted at laboratory scale (112 capsules) and pilot scale (100,000 capsules). The effect of extraction with supercritical CO2 on physical properties of capsules as well as key performance parameters such as drug respirable mass and retention in capsules following simulated inhalation tests using an Anderson cascade impactor are reported. A mass transfer model is used to explain the large difference in effectiveness between this method and conventional SFE.

[119c] - Adsorption of Benzaldehyde and Benzyl Alcohol onto Resin from Supercritical Carbon Dioxide

Carl T. Lira (speaker) Michigan State University 2527 Engineering Building East Lansing, MI 48824-1226 Phone: (517)355-9731Fax: (517)432-1105 Email: lira@egr.msu.edu

Xiao-ning Yang Michigan State University 2527 Engineering Building East Lansing, MI 48824 Phone: 1-517-432-5489Fax: 1-517-432-1105 Email: yangxia@egr.msu.edu Abstract: The supercritical carbon dioxide adsorption/desorption of solutes from solid is a technology with a range applications such as the recovery of valuable solutes or the regeneration of adsorbent. The supercritical fluid adsorption rates and equilibrium conditions have important roles in process designs. This study reports the equilibrium adsorption of benzaldehyde and benzyl alcohol from supercritical carbon dioxide onto a styrene-divinyl benzene resin, which can be used in the recovery of bitter almond oil from natural feedstocks, have been reported. The adsorption data were measured at pressures between 80 to 150 bar, and pressure temperatures from 308.2 to 328.2 K. The influence of fluid density and temperature is investigated and the adsorption for the two solutes and their mixtures is interpreted. A thermodynamic adsorption model is developed to correlate this adsorption data.

[119d] - Solubilities of Cholesterol and its Derivatives in Supercritical Carbon Dioxide

Zhen Huang National University of Singapore Dept. of chemical and environmental engineering Singapore, Singapore 119260 Singapore Phone: 65 8744347Fax: 65 7791936 Email: engp8908@nus.edu.sg

Z. Huang, Y.C. ChiewDepartment of Chemical & Environmental EngineeringNational University of Singapore10 Kent Ridge CrescentSingaporeAbstractSupercritical fluid carbon dioxide offers several advantages compared with organic liquid solvents for separations and reaction processes of thermally labile biomolecules. A major limitation is that the polar biomolecules are only slightly soluble in CO2. Usually a properly selected modifier is introduced into the SCF-CO2 to enhance its solvating power and broaden its application. Determination of quantitive solubility or phase equilibrium data is an important consideration because it provides the physical properties of biomaterials of interests necessary to investigate the feasibility of the design and development of new chemical processes that uses supercritical fluids as solvents. In this work, we report equilibrium solubilities of cholesterol and its derivatives: cholesteryl acetate, cholesteryl benzoate and cholesteryl butyrate in supercritical CO2 using a dynamic method. Measurements were performed in the pressure range from 80 to 240 bar and temperatures from 35 to 55 °C. We also consider methanol as a co-solvent to examine its effect on the solubilities of cholesterol and its derivatives. Molecular thermodynamic equation of state that explicitly accounts for molecular association was used to model the system. It is found that the experimental data are well described by the model.

[119e] - Gas Antisolvent Recrystallization: Experiments and Modeling

Gerhard Muhrer ETH Zurich Sonneggstrasse 3 Zurich, CH-8092 Switzerland Phone: ++4116327996Fax: ++4116321141 Email: muhrer@ivuk.mavt.ethz.ch

Werner Doerfler ETH Zurich Sonneggstrasse 3 Zurich, CH-8092 Switzerland Phone: ++4116322493Fax: ++4116321141 Email: doerfler@ivuk.mavt.ethz.ch

Marco Mazzotti (speaker) ETH Zurich Institut fuer Verfahrenstechnik Zurich, CH-8092 Switzerland Phone: ++41-1-6322456

Fax: ++41-1-6321141 Email: mazzotti@ivuk.mavt.ethz.ch

Abstract: The Gas AntiSolvent (GAS) recrystallization process is considered a rather promising technology for the production of micron or submicron particles for pharmaceutical and specialty chemicals applications. In this process, carbon dioxide is used as antisolvent for the solute, which is initially solubilized in a conventional solvent (completely miscible with CO2. Upon CO2 addition, the solvent power of the initial solution is reduced, and solute precipitation is triggered. Several promising applications of high-pressure antisolvent particle formation techniques have been reported. Most of them are of the proof of concept type and only a very few parametric anlyses and theoretical studies have been reported so far. In this work we thoroughly study the effects of different operating parameters on product quality experimentally and develop the first model able to describe and explain GAS recrystallization results. In the case of the precipitation from ethanol of a pharmaceutical compound, experiments show that particle size distribution is unimodal and rather narrow for very fast or very slow CO2 addition rates, but bimodal for intermediate ones. At all temperature investigated the average particle size decreases over almost two orders of magnitude with increasing CO2 addition rate. Low temperatures reduce both average particle size and agglomeration extent.These findings can be analyzed by using a model of GAS recrystallization. In this, volume expansion upon CO2 addition and population balances are decoupled. The former is described assuming thermodynamic equilibrium and neglecting mass transfer resistance. On the other hand, particle formation depends on crystal growth (integration controlled model) and on primary and secondary nucleation. Model results show the same qualitative behavior as the experiments and demonstrate that bimodal particle size distributions are due to the occurrence of more than one burst of nucleation. This may happen as an effect of the interaction among nucleation, growth and supersaturation build-up rate, which is controlled through CO2 addition rate. These experimental and theoretical findings indicate strategies for GAS optimization and motivate further work.

[119f] - Effect of Polymers on Protein Loading and Release of Micro-Particles Produced by Supercritical Anti-Solvent Processes

Nicola Elvassore (speaker) University of Padova via Marzolo, 9 Padova, 35100 Italy Phone: 39 049 8275472Fax: 39 049 8275461 Email: nelvas@polochi.cheg.unipd.it

Alberto Bertucco University of Padova via Marzolo, 9 Padova, 35131 Italy Phone: 39 049 8275457Fax: 39 049 8275461 Email: bebo@polochi.cheg.unipd.it

Paolo Caliceti University of Padova via Marzolo, 5 Padova, 35131 Italy Phone: 39 049 8275695Email: caliceti@dsfarm.unipd.it

Abstract: Supercritical anti-solvent (SAS) techniques are suitable for producing protein loaded polymeric micro-particles. SAS embodies a series of techniques for the microencapsulation of bio-degradable pharmaceuticals at low temperature and with reduced amounts of organic solvents. Recent studies have shown that labile compounds such as proteins can be processed without losing their biological activity. Entrapment of protein within polymers coats or matrices is specially used to obtain controlled-release dosage forms.In this work a continuos SAS method has been used to charge microspheres of different polymeric blends with proteins; in particular insulin has been dispersed in micro sphere of poly-lactide-acid (PLA) and poly-ethylene-glycol (PEG) mixtures.A study for the production of the micro-particles was carried out in order to point out the effects of the concentration of PLA and PEG blends on the particle dimension and their diameter distribution range. PEGs of different molecular weight were used.The controlled release of the charged particles was detected by both in vitro and in vivo profile. The results obtained show that the proteins still retain their biological activity and the yield of the SAS process protein loading is affected by the polymer blend concentration. The controlled release may be adjusted by tuning the hydrophilic polymer (PEG) content in the polymeric micro-particle matrix. [119g] - Kinetics and Rate of Enzymatic Hydrolysis of Cellulose in Supercritical Carbon Dioxide

Yeon Woo Ryu and Chul Kim (speaker) Ajou University won-chon dong Suwon, 442-749 Rep. of Korea Phone: +82-331-219-2384Fax: +82-331-214-8918 Email: ckim@madang.ajou.ac.kr

Abstract

Experiments were carried out on the application of supercritical fluid in the hydrolysis of cellulose by an enzyme, cellulase. The stability of cellulase was sustained at the pressure of up to 160 atm for 90 min at 50℃ in supercritical carbon dioxide. In the hydrolysis of cellulose the glucose yield was 100% at supercritical condition. Kinetic constants of hydrolysis at supercritical condition were increased as compared to those at atmospheric condition. The hydrolysis reaction was found competitively inhibited by glucose at supercritical condition. Supercritical fluids serve as a particularly interesting class of solvents which may be used for enzyme-catalyzed reaction. Biochemical reactions in supercritical fluids were demonstrated first in 1985 by Randolph et al. In their pioneering work where the enzyme, alkaline phosphatase was found maintain its activity. Although the exposure of many enzymes to supercritical fluids caused the decreases in their activities (Marty et al., 1990), some enzymes were not deactivated (Taniguchi et al., 1987). Motivated by these observations along with favorable properties of supercritical fluids for the extensive studies on the enzymatic reactions at supercritical conditions have been carried out(Hammond et al., 1985; Nakamura et al., 1985; Chi et al., 1988; Rafi et al., 1986; Randolph et al., 1988; Lee et al., 1993).In this study the hydrolysis of cellulose by cellulase was performed in supercritical carbon dioxide and the kinetic constants in the rate expression was evaluated.

[120] - Benign Synthesis in Supercritical FluidsChair: Martin A. AbrahamUniversity of ToledoChemical and Enviornmental Engineering DepartmentMail Stop 305, 2801 West Bancroft StreetToledo, OH 43606-3390Telephone Number: 419-530-8092Fax Number: 419-530-8086Email: mabraham@eng.utoledo.edu

Vice Chair: L. Antonio EstevezUniversity of Puerto RicoDepartment of Chemical EngineeringP.O. Box 9046Mayaguez, 00681-9046Telephone Number: 787-832-4040 ext. 2573Fax Number: 787-265-3818Email: l_estevez@rumac.uprm.edu; estevez@caribe.net

[120a] - Improved Combustion Efficiency and NOx Control Using Thermally and Catalytically Cracked Supercritical Fuel (TCCSF)

Nsima T. Obot (speaker) Argonne National Laboratory ET-Energy Technology Division Argonne, IL 60439 Phone: 630-252-7638Fax: 630-252-5568 Email: obot@anl.gov

G.A. Mansoori University of Illinois, Chicago 810 S. Clinton Street Chicago, IL 60607-7000 Phone: 312-996-5592Fax: 312-996-0808 Email: mansoori@uic.edu Abstract: The objective of this presentation is to discuss the basis for developing thermally and catalytically cracked supercritical fuel systems and technology to improve combustion efficiency and to reduce emissions. The process involves up-front reforming of the fuel at supercritical conditions. This fundamental and applied research focuses on diesel engines and industrial combustion processes such as boilers, especially those burning low-grade liquid fuels. This study is a joint project by the University of Illinois at Chicago (UIC) and the Argonne National Laboratory (ANL). Eclipse Combustion, Inc. (ECI) is the consultant in this project. A fluid is termed supercritical when the temperature and pressure are higher than the corresponding critical values. Above the critical temperature, there is no phase transition in that the fluid cannot undergo a transition to a liquid phase, regardless of the applied pressure. A supercritical fluid (SF) is characterized by physical and thermal properties that are between those of the pure liquid and gas. These drastic changes in thermophysical properties make a supercritical fuel appreciably preferred over that of a liquid fuel with the same density. It is expected that the combustion phenomena resulting from that of a supercritical fuel to be quite different from that of a liquid fuel.Thermally and catalytically cracked fuel processing is used world-wide to produce high octane number gasoline. The distinction between this process and that proposed here is the use of supercritical conditions. The TCCSF process is expected to provide excellent combustion characteristics which, in turn, will result in improved combustion efficiency and reduced emissions.The present study does not duplicate information available in the literature. Combustion-related studies have been limited to droplet vaporization at supercritical conditions. There is very limited information on the properties of supercritical hydrocarbon fuels, and none on the combustion characteristics and the potential to reduce emissions, especially for industrial-type liquid fuels.The proposed technology is critical and applicable for mechanical power generation machines /internal combustion engines (stationary and aircraft gas turbines, gasoline and diesel engines), industrial processes, home and industrial heat generation as well as water heating. Another cross-cutting feature of this research project relates to the reactor/heat exchanger technology. This will be the cornerstone of improvements in numerous applications such as cooling technology for high-speed aircraft where the jet fuel is the primary coolant, production of chemicals from feedstock for petrochemical industry, natural gas purification at the well-head through thermal swing adsorption, and fuel processing for many practical applications including fuel cell-powered transportation systems. Also, the technology will provide the capability to affect chemical reactions and heat transfer for

situations that are difficult or not possible with conventional technology. Finally, the catalyst development is also critical in several program areas - advanced materials (new or improved catalysts for applications in engine emissions reduction and natural gas technology) and biomass resource development.There are several innovative aspects of this study. One is the use of very compact catalytic reactor/heat exchanger units for the fuel processing, thus enabling simulation of the use of exhaust gas or a heated fluid stream for practical situations. The second relates to the evaluation and preparation of catalysts that may eventually lead to the development of coke resistant catalysts. Next, the detailed study on coke formation and its mitigation in very compact, near micro channels is of practical significance for applications other than diesels and industrial boiler liquid fuels.There are many potential benefits for this project. First, the TCCSF technology will afford the much needed fuel flexibility because virtually all hydrocarbon liquid fuels can be cracked at supercritical conditions. In this regard, it is worth mentioning that supercritical alcohols have been used to remove organic sulfur from coal, thus providing solid product suitable for use in coal-fired boilers. Second, the inherently low hydrocarbon content in the exhaust for lean burn diesels requires the addition of fuel to the exhaust for selective catalytic reduction. Because some of the products of the TCCSF process (e. g., ethylene) provide better reducing action than diesel, these can be used to enhance the limited hydrocarbon in the exhaust, thus resulting in substantial savings in fuel. Finally, the TCCSF technology is of importance to several industrial processes including aircraft and stationary gas turbines and diesels and industrial combustion.

[120b] - Synthesis, Blending, and Doping of Electrically Conducting Poly(3-undecylbithiophene) in Supercritical Carbon Dioxide

Kimberly F. Webb (speaker) Georgia Institute of Tecnology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-4209Fax: 404-864-2866 Email: gt0401b@prism.gatech.edu

Amyn S. Teja Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-3098Email: amyn.teja@che.gatech.edu

Abstract: Electrically conducting polymers are of interest in a variety of practical applications including light emitting diodes, biological sensing devices, and antistatics. In particular, poly(3-undecylbithiophene) has been shown to have electrical conductivity that makes it especially suitable for rechargeable batteries and electrochromic displays. The polymerization of 3-undecylbithiophene in supercritical carbon dioxide was studied in this work. Our work shows that a regioregular, highly conjugated, polymer can be formed that exhibits significant electrical conductivity. However, the polymer is difficult to process because it is formed into a black powder, which is unstable, brittle and hard. Therefore, the polymerization was also performed in situ in porous, crosslinked polystyrene. The resulting blend is stable and retains its conductivity for significant lengths of time. The temperature, pressure, and mixing conditions were adjusted to maximize the conductivity. In addition, the blends were doped with iodine under supercritical carbon dioxide conditions to increase their electrical conductivity.

The poly(3-undecylbithiophene) formed in supercritical carbon dioxide was comparable in its properties to the polymer formed using nitrobenzene as the solvent. Also, supercritical carbon dioxide appears to be a promising solvent for in situ polymerization of poly(3-undecylbithiophene) and for the formation of its blends. Doping the blends with iodine under supercritical carbon dioxide conditions yielded increased uptake of iodine and an increased diffusion rate compared with conventional doping. The electrical conductivity was also increased by several orders of magnitude.

[120c] - Reaction Engineering and Modeling of Continuous VF2 Polymerization in scCO2

George Roberts North Carolina State University Department of ChemicalEngineering Raleigh, NC 27695-7905 Phone: 919-515-7328Fax: 919-515-3465 Email: groberts@eos.ncsu.edu

Joseph M. DeSimone University of North Carolina,Chapel Hill CB#3290, Venable and KenanLaboratories Chapel Hill, NC 27599-3290 Phone: 919-962-2166Fax: 919-962-5467 Email: desimone@unc.edu

Paul A. Charpentier (speaker) North Carolina State University 1017 Main Campus Drive, Suite3500 Raleigh, NC 27606 Phone: 919 513-2832Fax: 919 513-1655 Email: pacharpe@eos.ncsu.ed

Abstract: The polymer industry is one of the largest segments in the world economy and one of the most energy intensive and waste generating. Supercritical carbon dioxide (scCO2) has emerged as a viable green　 solvent for polymerization due to its unique and "tunable" properties, such as liquid-like density and gas-like diffusivity. In addition to replacing VOCs and waste streams, significant energy savings can be realized by using this solvent for both lowering the energy to dry polymers and for lowering processing costs. In order to harness these advantageous properties of CO2 for making polymers industrially, new technologies and processes are required for effective process substitution. This has led our group to carry out process, kinetic, and physical/chemical research to demonstrate the feasibility of this approach. Our current research has centered on the modeling of vinylidene fluoride (VF2) polymerization as a representative system for chain-growth polymerization. Polymerizations were carried out in a novel continuous apparatus in scCO2 where high MW polymer was produced. A detailed kinetic analysis has been undertaken in which experimental rate and MWD data is compared to that predicted from a developed kinetic model. Thedeveloped model was able to account for the unique properties induced by this novel polymerization medium and how it can be potentially exploited to make commodity as well as specialty polymers.

[120d] - Production of Hydrophobic Polysaccharides in Supercritical Carbon Dioxide

Raymond Oliver (speaker) Imperial Chemical Industries PO Box 90, Room R314, WiltonMiddlesbrough, Cleveland TS90 8JE UK Phone: + 44 (0)1642 436578Fax: + 44 (0)1642 436206 Email: ray_oliver@ici.com

Diego Fernandez Imperial Chemical Industries R337, Wilton Centre, PO Box 90 Wilton, Middlesbrough, TS90 8JE UK Phone: +44(0)1642 436511Fax: +44(0)1642 436206 Email: diego_fernandez@ici.com

Derek Graham Imperial Chemical Industries R307 Wilton Centre, PO Box 90Wilton, Middlesbrough, TS90 8JE UK Phone: 44 1642 436574Fax: 44 1642 436206 Email: derek_graham@ici.com

Padma Narayan National Starch and Chemical Co. 10 Finderne Ave Bridgewater, NJ 08807 Phone: 908-685-5703Fax: 908-685-5552 Email: padma.narayan@nstarch.com

Peter Saxton Imperial Chemical Industries R307 Wilton Centre, PO Box 90Wilton, Middlesbrough, TS90 8JE UK Phone: +44 (0) 1642 436413Fax: +44 (0) 1642 436206 Email: peter_saxton@ici.com

Abstract: Starches and other polysaccharides have traditionally been chemically modified in aqueous media for various applications. These modified materials can be tailored to have more hydrophilic or hydrophobic properties, depending upon the chemical moieties added to the polysaccharide backbone. Starches of this nature have been used in a variety of products ranging from food stabilizers, paper sizing agents, adhesives, and coatings. In aqueous systems, the achieved degrees of substitution (DS) on the starch backbone usually have been less than one hydroxyl group per anhydroglucose unit (out of a maximum of three hydroxyl groups). A fully substituted starch would have a DS of 3.0.

In this study, we explored the possibility of fabricating hydrophobically modified starches with DS values approaching 3.0. Since these are difficult to produce in aqueous systems, supercritical carbon dioxide (SCCO2) was chosen as the reaction medium. The advantages of using SCCO2 would be the elimination of harsh solvents, easier solvent recovery, and the potential enhancement of reaction rates and mass transfer.

Acetic anhydride was chosen as the modifier for performing acetylation reactions with starches. Sodium acetate was chosen as a catalyst for esterification of the starch hydroxyls with acetic acid groups. The phase behavior of the modifier in SCCO2 was performed in a variable volume view cell to determine the effect of solubility on the reaction efficiency. After this was characterized, reaction conditions were optimized for temperature, pressure, concentration of modifier, and types of starches.

We have successfully demonstrated the use of supercritical carbon dioxide (SCCO2) as a reaction medium for the production of novel hydrophobic starches. Acetic anhydride was found to dissolve in SCCO2 at pressures as low as 2500 psi at 125 C. Starches with a DS up to 2.9 were made in SCCO2; the morphology of the final product was strongly dependent upon the DS. Results indicated that SCCO2 was promising for starch and acid anhydride esterifications. The effects of anhydride

solubility and polysaccharide crystallinity were important in determining the reaction mechanism within the granules. Further means to improve these reactions in SCCO2 would be to study other modifiers, catalysts, and model the reaction kinetics.

[120e] - Hydrogenation at Supercritical single-phase conditions

Magnus H?r? (speaker) Chalmers University of Technology c/o SIK, PO Box 5401 Goteborg, SE-40229 Sweden Phone: +46-31-33 55 668Fax: +46 -31- 83 37 82 Email: magnus.harrod@fsc.chalmers.se

Sander van den Hark Chalmers University of Technology c/o SIK, PO Box 5401 Goteborg, SE-40229 Sweden Phone: +46-31-33 51 348Fax: +46 -31- 83 37 82 Email: svh@fsc.chalmers.se

Maj-Britt Macher Chalmers University of Technology c/o SIK, PO Box 5401 Goteborg, SE-40229 Sweden Phone: +46-31-33 51 305Fax: +46-31-83 37 82 Email: mbm@fsc.chalmers.se

Poul M?ler P. M?ler Consultancy Inc. Augustenborggade 21B Aarhus, DK-8000 Denmark Phone: +45-86 11 63 11Fax: +45-86 11 63 14 Email: PoulMoeller@mail1.stofanet.dk

Abstract: Many common hydrogenation reactions involve gaseous hydrogen, a liquid substrate (or substrate solution), and a solid catalyst. In such systems the hydrogen concentration at the catalyst surface is crucial for rate and selectivity of the reaction. Hydrogen, however, is poorly soluble in liquids, there is a considerable transport resistance between the gas phase and the bulk liquid. Furthermore, there is also a transport resistance between the bulk liquid and the catalyst. Both factors limit the hydrogen concentration at the catalyst surface and consequently the reaction rate. This can also lead to unwanted side reactions like isomerization. For instance, in the food industry, the partial hardening of edible oils suffers from the formation of unwanted trans-fatty acids due to hydrogen deficiency.

Supercritical fluids combine in a very favourable way gas and liquid properties - they have a low viscosity, low surface tension and high diffusivity. By addition of a suitable solvent a single-phase system with hydrogen, substrate and the solvent can be created. In this way transport resistance between gas and liquid is eliminated. Even the resistance at the catalyst surface is reduced.

In our studies we have investigated the hydrogenation of palm and rapeseed oil for food use and the hydrogenation of fatty acid methyl esters to fatty alcohols. Propane has been used to create the single-phase conditions. Extremely high reaction rates were achieved. This means that the plants can be much smaller. In some cases the catalyst life can be extended. This means reduced consumption of catalyst. The product quality was also improved. These results are so promising that a pilot-plant is under construction.

The same technique will in the future be applied to a wide range of products.

[120f] - Synthesis of Controlled Release Drug Products in Supercritical Medium

Ozge Guney Texas A&M University Zachary Engineering Bldg. College Station, TX 77843-3122 Phone: (979) 845-0354Fax: (979) 845 6446 Email: o0g2534@unix.tamu.edu

Abstract: Controlled delivery products have received considerable attention in the last years. These substances prolong the drug's therapeutic effect, keeping the drug concentration between the therapeutic limit and the toxicity limit, without increasing the dosage, which is the case for the traditional pharmaceutical systems. The drug and the carrier have to come in contact with each other in a solvent environment in preparation of controlled release drugs. The solvent acts as a swelling agent for the carrier and dissolves the drug for impregnation of the carrier. In classical synthesis organic solvents are used. The final product, though, must be free of the organic solvent. Removal of the solvent is also necessary to provide constant property for the final product that does not change with natural evaporation of the solvent. One of the major cost items in the synthesis of controlled release drugs is the removal of this solvent to acceptable limits. The purpose of this study is to eliminate the

production step involving the organic solvent from the overall process. In order to achieve this goal, the drug is introduced into the polymer matrix using supercritical carbon dioxide (scCO2) as the carrier solvent and the swelling agent.

Specifically, this study focuses on the impregnation of a biodegradable polymer matrix with 5-fluorouracil and b -estradiol, drugs which are used for chemotherapy and estrogen hormone therapy, respectively. The fundamental issues governing this process, namely swelling of the polymer matrix, solubility of the drug components in scCO2 and the adsorption/partition coefficients in the presence of scCO2 are studied. Experiments are performed to determine the swelling of the biodegradable polymer matrices used in controlled release drugs with scCO2 at different temperatures and pressures. Data on the solubilities of these drugs in scCO2 at 308-328 K temperature and 101-201 bar pressure with or without a cosolvent (£ 15% by weight) will be reported. The adsorption equilibrium constants/partition coefficients for these drug components on poly-lactide-co-glycolide at the same conditions will be presented. We will also present a model to predict the drug loading breakthroughs. These drugs will be evaluated in simulated biological systems for drug release rates.

[120g] - Biocatalysis in Supercritical Carbon Dioxide with Crude Enzyme Preparations

Christoph A. Bauer (speaker) Technical University-Graz Inffeldgasse 25 Graz, A-8010 Austria Phone: ++43 316 873 7471Fax: ++43 316 873 7472 Email: bauer@tvtut.tu-graz.ac.at

Thomas Gamse Technical University-Graz Inffeldgasse 25 Graz, A-8010 Austria Phone: ++43 316 873 7477Fax: ++43 316 873 7472 Email: gamse@tvtut.tu-graz.ac.at

Rolf Marr Technical University-Graz Inffeldgasse 25 Graz, A-8010 Austria Phone: ++43 316 873 7471Fax: ++43 316 873 7472 Email: marr@tvtut.tu-graz.ac.at

Abstract: In recent years the application of biocatalysts in nonaqueous systems has greatly increased. Fat and steroid modifications and synthesis of flavour compounds for foodstuff industry by lipase-catalyzed esterification and transesterification have been investigated using organic solvents as reaction media. These solvents have, however, major disadvantages concerning product /solvent-separation and toxicity, which can be avoided by using supercritical carbon dioxide as enzyme reaction medium. The cheapest and most widely used enzyme for hydrolysis and esterification in biotechnology is isolated from porcine pancreas. In studies at our department it has been proved that crude preparations of lipase from porcine pancreas (PPL) have excellent characteristics for the use in supercritical carbon dioxide. A biocatalytic process for the production of short chain flavour esters, which are used in the fragrance industry and can be sold as natural flavours, has been established in laboratory scale. On the one hand the crude PPL turned out to be stable against high pressures as well as high temperatures (up to 75℃). On the other hand the specific activity of the crude preparations was increased several-fold after treatment with supercritical carbondioxide (more than 600 % residual activity toward various substrates) without change of the protein content. Supercritical carbon dioxide exhibits very good solubility for many impurities of crude enzyme preparations like fatty acids while the protein itself is insoluble. So supercritical carbon dioxide can serve not only as reaction medium but also as a purifier for low-cost crude preparations at the same time. This effect might be another benefit of the use of supercritical carbon dioxide in biocatalysis, which is still restricted to research on laboratory scale.

[120h] - Production of Cyclodextrins and the Kinetic Mechanism in Supercritical Carbon Dioxide

Eun Yong Ko, Yeon Woo Ryu and Chul KimAjou University won-chon dong Suwon, 442-749 Rep. of Korea Phone: +82-331-219-2384Fax: +82-331-214-8918 Email: ckim@madang.ajou.ac.kr

Abstract: The hydrolysis of starch by an enzyme, cyclodextrin glucauotransferace(CGTase) in supercritical carbon dioxide medium was conducted to explore a possible enhancement of the reaction. The inherent gas-like low viscosities and high diffusivities of supercritical fluids increase the rates of mass transfer of substrate to enzyme. The optimum temperature of the enzyme(CGTase) reaction was 50?60? and the optimum pH was 5.5?6.0. The enzyme(CGTase) activity in supercritical carbon dioxide medium was maintained at the temperature range of 50?60?. Over 80% of the enzyme activity was maintained at these temperature and pH condition and at the pressure range of 80?160 atm. However over 90% of the activity loss was found at temperature higher than 80? at supercritical condition. Amount of cyclodextrin produced from starch by enzyme(CGTase) reaction in supercritical carbon dioxide was 37.3 g/L, and yield was 0.75 g/g. The total productivity of cyclodextrin in supercritical carbon dioxide was about 1.4 times of that at atmospheric pressure. Also investigated was the elucidation of the kinetic mechanism and the rate expression. Simple Michaelis-Menten equation with product inhibition was found applicable in this reaction system carried out in supercritical fluid as well. Kinetic constants of CGTase reaction system

on potato starch in supercritical carbon dioxide were evaluated, and CGTase reaction was found competitively inhibited by a major product, ?-cyclodextrin. The prediction by the rate expression was in good agreement with the experimental observation.

[121] - Molecular Simulations of Supercritical Fluids

Chair: Perla BalbuenaUniversity of South CarolinaDepartment of Chemical EngineeringColumbia, SC 29208Telephone Number: 803-777-8022Fax Number: 803-777-8265Email: balbuena@engr.sc.edu

Vice Chair:Karl JohnsonUniversity of PittsburghDepartment of Chemical Engineering1249 Benedum HallPittsburgh, PA 15261Telephone Number: 412-624-5644Fax Number: 412-624-9639Email: karlj@pitt.edu

[121a] - Potential Model and Vapor-Liquid Phase Equilibria of Perfluoroethers

Hung-Chih Li (speaker) University of Tennessee 1611 Laurel Ave. Apt. 1418 Knoxville, TN 37916 Phone: (865) 5461490Fax: (865)5461490 Email: hcli@verdi.engr.utk.edu

Shengting Cui University of Tennessee 419 Dougherty Engineering BuildingKnoxville, TN 37996-2200 Phone: 865-241-4896Email: scui@utk.edu

Peter Cummings University of Tennessee, Knoxville Chemical Engineering Department Knoxville, TN 37996-2200 Phone: 423-974-0227Fax: 423-974-7076 Email: ptc@utk.edu

Hank D. Cochran Oak Ridge National Laboratory Chemical Technology Division Oak Ridge, TN 37831-6224 Phone: 865-574-6821Fax: 865-241-4829 Email: hdc@ornl.gov

AbstractWe propose a united atom potential model for perfluoroethers obtained by ab-initio calculation and fitting vdW parameters to the existing phase equilibrium data. In the parameter fitting, we used configuration biased Monte Carlo simulations on several linear perfluoroethers with different ratio of oxygen in the back- bone.

IntroductionPerfluoroethers (PFEs) have attracted a lot of interest because of their applications in lubrication, pharmaceutical industry, and even cosmetic industry. One of the applications of PFEs is to serve as the CO2-philic part of surfactants that form microemulsions with aqueous cores in supercritical carbon dioxide. With so many different applications, it will be of great interest to be able to model PFEs with molecular simulation techniques. Of course, it is very important for molecular simulations to have an appropriate potential model, but no such model for PFEs has been proposed so far. Although there have been some simulations (Asako 1999) on PFEs, potential models developed for other systems were adopted for those simulations. Successful united-atom (UA) models with transferable parameters have been developed for perfluoroalkanes (Cui etc. 1998). Based on that experience and those results, it is our goal to develop a potential model for PFEs.

MethodIn this work, we used Gaussian 98 to generate the torsional energy profile and the atomic charges of PFEs and then collapsed the atomic point charges into UA point charges. The so-obtained torsional potential terms and UA charges as well as the molecular structure data are used in the potential model developed for PFEs. With the parameters of torsional, bond-bending, and electrostatic potentials fixed, configuration biased Gibbs ensemble Monte Carlo simulations are then carried out on several different linear PFEs. And the simulation results are compared to the existing experimental data to obtain the

vdW parameters.

ReferenceAsako Koike (1999). Molecular dynamics study of tribological behavior of confined branched and linear perfluoropolyethers. J. Phys. Chem. B 103, 4578-4589.S. T. Cui, J. I. Siepmann, H. D. Cochran, and P. T. Cummings (1998). Intermolecular potentials and vapor-liquid phase equilibria of perfluorinated alkanes. Fluid Phase Equilibria, 146, 51-61.

AcknowledgmentThis work was supported by the Division of Chemical Sciences of the U. S. Department of Energy. ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725.

[121b] - Molecular Dynamics Study of Supercritical Water With a Flexible Potential Model

Hiroshi Inomata (speaker) Tohoku University Japan Email: inomata@scf.che.tohoku.ac.jp

Chee Chin Liew Tohoku National Industrial Research Institute 4-2-1 Nigatake, Miyagino-ku Sendai, 983-8551 Japan Phone: +81-22-237-5211Email: liew@tniri.go.jp

Abstract: MD simulations were conducted to discuss the solution structure of supercritical water/aqueous solution especially hydrogen bonding by examining the three-dimensional spatial distribution functions. The potential model used was a 4-site flexible water model, referred to as cm4P-mTR, which was proposed for SCW by Liew et al. The simulation results revealed that the preferable configuration of water pairs is linear hydrogen bonding and the bifurcated hydrogen bonding configuration could be observed especially near the critical point.

[121c] - A New Methanol Potential Model and MD simulation Near The Critical Point

Hiroshi Inomata Tohoku University Japan Email: inomata@scf.che.tohoku.ac.jp

Chee Chin Liew Tohoku National Industrial ResearchInstitute 4-2-1 Nigatake, Miyagino-ku Sendai, 983-8551 Japan Phone: +81-22-237-5211Email: liew@tniri.go.jp

Tetsuo Honma (speaker) Tohoku University 07 Aoba, Aramaki Sendai, 980-8579 Japan Phone: +81-22-217-7282Email: testu@scf.che.tohoku.ac.jp

Shunsuke Kuzuhara Tohoku University 07 Aoba, Aramaki Sendai, 980-8579 Japan Phone: +81-22-217-7282shunsuke@scf.che.tohoku.ac.jp

Abstract: A new flexible potential model was proposed for methanol similarily to that for water by Liew et al. The model, three-site model, composes methanol from hydrogen, oxygen and methyl group, where inter-site potential is expressed as the sum of Lennard-Jones potential and Coulombic potential. The intra-site modes were considered with the modified Toukan-Rahman potential propsed by Liew et al. The parameters were determined by using the saturated liquid density at 25C and IR spectrum data. MD simulation with the determined parameters was performed to give saturation curve of methanol with a constrained density gradient technique. In the simulations, LJ wall and gravity were introduced for the z-axes to have a goodvapor-liquid separation at the interface near the critical point. The calcurated critical point is in good agreement with experimental data. Similar attempts were made for water.

[121d] - Monte Carlo Simulation of Mixtures Containing Supercritical Carbon Dioxide, Dinitrogen and Propane

llja Siepmann University of Minnesota Department of Chemistry

207 Pleasant St., S.E. Minneapolis, MN 55455-0431 Phone: 612-624-1844Fax: 612-626-7541 Email: siepmann@chem.umn.edu

Jeffrey J. Potoff (speaker) University of Minnesota 207 Pleasant ST SE Minneapolis, MN 55455-0431 Phone: 612-626-2085Email: potoff@chem.umn.edu

Abstract: Carbon dioxide is one of the most often used solvents for supercritical fluid extraction. Although intermolecular force fields for n-alkanes[1,2], carbon dioxide[3] and dinitrogen exist that reproduce accurately saturated liquid and vapor densities as well as vapor pressures, recent simulations for binary mixtures of supercritical carbon dioxide/n-alkane mixtures were only in qualitative agreement with experiment when Lorentz-Bethelot combining rules were used[4]. One solution was to implement a set of combing rules described by Kong for the unlike pair interactions[5]. While producing very favorable results for supercritical carbon dioxide/n-alkane mixtures, the use of Kong combing rules for unlike molecule interactions in mixtures of supercritical carbon dioxide/methanol resulted in greater deviations from experiment than when Lorentz-Berthelot combing rules were used. While the lack of polarizability has been suggested as a source of error in the previous calculations, these results also suggest that the correct balance of van der Waals and electrostatic forces is not achieved in the models used previously.

In this work, it is shown how binary mixture calculations can be used to fine tune the TraPPE (transferable potentials for phase equilibria) molecular force fields for polar molecules where multiple sets of parameters can lead to an adequate reproduction of the pure component phase diagrams. As an example, grand canonical histogram-reweighting[6] and Gibbs ensemble Monte Carlo[7] simulations were used to calculate the phase diagrams for the binary mixtures supercritical carbon dioxide/propane, dinitrogen/propane and carbon dioxide/dinitrogen, as well as the ternary mixture carbon dioxide/dinitrogen/propane. The TraPPE force field employs a Lennard-Jones potential for the the repulsive and dispersive interactions while point charges are used for the electrostatic interactions. Lorentz-Berthelot combining rules are used for both like and unlike-pair interactions. Potential parameters for the fixed charge carbon dioxide and dinitrogen force fields were tuned such that the simulation results for the pure component and binary mixture phase diagrams for carbon dioxide/propane and dinitrogen/propane were in good agreement with experiment. Furthermore, adiabatic nuclear and electronic sampling Monte Carlo (ANES-MC) simulations[8] in the grand canonical ensemble were used to study the phase behavior of a fluctuating-charge carbon dioxide model and of a mixture of carbon dioxide and propane. Part of the computer resources were provided by the Minnesota Supercomputing Institute (MSI).

REFERENCES[1] Errington, J. R., and Panagiotopoulos, A. Z., 1999, J. Phys. Chem. B, 103, 6314.[2] Chen, B., and Siepmann, J. I., 1999, J. Phys. Chem. B, 103, 5370.[3] Harris, J. G., and Yung, K.H., 1995, J. Phys. Chem., 99, 12021.[4] Potoff, J. J; Errington, J. R., and Panagiotopoulos, A. Z, 1999, Molec. Phys., 97, 1073.[5] Kong, C. L., 1973, J. Chem. Phys., 59, 2464.[6] Potoff, J. J., and Panagiotopoulos, A. Z., 1998, J. Chem. Phys., 109, 10914.[7] Panagiotopoulos, A. Z., 1987, Molec. Phys., 61, 813. [8] Chen, B.; Potoff, J. J., and Siepmann, J. I., 2000, J. Phys. Chem. B, 104,2378.

[121e] - Temperature/Density Effects on H+/Cl- Association in Hydrothermal Solutions. Conductivity Measurements andMolecular Simulation

Ariel A. Chialvo (speaker) Oak Ridge National Laboratory Bethel Valley Rd Oak Ridge, TN 37831-6110 Phone: (865) 574-1252Fax: (865) 574-4961 Email: 2ac@ornl.gov

Patience C. Ho Oak Ridge National Laboratory Bethel Valley Rd Oak Ridge, TN 37831-6110 Phone: (865) 574-4971

John M. Simonson Oak Ridge National Laboratory Bethel Valley Rd Oak Ridge, TN 37831-6110 Phone: (865) 574-4962

Peter Cummings University of Tennessee, Knoxville Chemical Engineering Department Knoxville, TN 37996-2200 Phone: 423-974-0227Fax: 423-974-7076 Email: ptc@utk.edu

Abstract: Knowledge of the properties of supercritical aqueous mixtures is essential to the understanding of the dissolution, transport, and precipitation of salts in many natural environments and industrial processes. The characterization of these hydrothermal systems

requires the analysis of the equilibrium constants for the solubility and ionization processes [1]. In particular, the thermodynamicdescription of many natural and industrial processes including volcanic vapors, hydrothermal vents, steam power generation and supercritical water oxidation, relies on the availability of accurate data for the thermodynamic behavior of HCl aqueous solutions. The dissociation of HCl in aqueous solutions has been studied extensively by calorimetric techniques [2], electrical conductance [3-5], and solubility measurements [6,7]. Yet, the thermodynamic properties of aqueous HCl solutions, especially those at high temperatures and low densities, are still the matter of some debate [8], in that the dissociation constants determined from solubility data appear to be at odds with those from conductivity measurements. These discrepancies highlight the intrinsic challenges behind the accurate measurements of electric conductivity in low-density, dilute, and extremely corrosive aqueous systems, the likely existence of additional species not taken into consideration in the treatment of solubility data, and consequently, the need for improved experimental methods and more sophisticated modeling techniques. Among a few others, molecular-based approaches to ion solvation show great potential in the quest for a fundamental understanding of ion solvation, by guiding the interpretation of experimental data, assisting in the assessment of their consistency, and connecting the microscopic and macroscopic properties of interest in a rigorous, unambiguous fashion [9]. As part of our ongoing molecular-based investigation of high-temperature ion solvation, in this work we focus on the study of the H+/Cl- ion-pair association over a wide range of state conditions. We report here the molecular-based determination of the ion-pair association constant via potential of mean-force calculations and their interpretation based on microstructural details of the aqueous system at infinite dilution [10]. These results are compared with new association constants measured with a flow-through cell, to make a direct comparison between the simulation results and the experimental data [11]. This comparison allows us to test the reliability of the intermolecular potentials involved, before we proceed with the molecular-based studies at conditions inaccessible (e.g., at lower density and higher temperature) by current experimental methods.

REFERENCES:[1] R. E. Mesmer, D. A. Palmer, and J. M. Simonson, in Activity Coefficients in Electrolyte Solutions, 2nd Edition ed., edited by K. S. Pitzer (CRC Press, Boca Raton, 1991), pp. 491-529.[2] J. M. Simonson, H. F. Holmes, R. H. Busey, R. E. Mesmer, D. G. Archer, and R. H. Wood, Journal of Physical Chemistry 94, 7675-7681 (1990).[3] E. U. Franck, Zietschr. Phys. Chemie N.F. 8, 192-206 (1956).[4] D. Pearson, C. S. Copeland, and S. W. Benson, Journal of the American Chemical Society 85, 1047-1049 (1963).[5] J. D. Frantz and W. L. Marshall, American Journal of Science 284, 651-667 (1984).[6] J. D. Frantz and R. K. Popp, Geochimica et Cosmochimica Acta 43, 1223-1239 (1979).[7] J. R. Ruaya and T. M. Seward, Geochimica et Cosmochimica Acta 51, 121-130 (1987).[8] B. R. Tagirov, A. V. Zotov, and N. N. Akinfiev, Geochimica et Cosmochimica Acta 61, 4267-4280 (1997).[9] A. A. Chialvo and P. T. Cummings, in Advances in Chemical Physics, Vol. 109, edited by S. A. Rice (Wiley & Sons, New York, 1999), pp. 115-205.[10] A. A. Chialvo, P. T. Cummings, and J. M. Simonson, Journal of Chemical Physics Submitted for publication (2000).[11] P. C. Ho, D. A. Palmer, M. S. Gruszkiewicz, and R. H. Wood, Journal of Physical Chemistry Submitted for publication (2000).

[121f] - Histogram Reweighting and Finite Size Scaling Study of Classical and Quantum Fluids

Wei Shi (speaker) University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412 621-9997Fax: 412 624 9639 Email: weishi@pitt.edu

Karl Johnson University of Pittsburgh Department of Chemical Engineering1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-5644Fax: 412-624-9639 Email: karlj@pitt.edu

Abstract: We use the histogram reweighting technique combined with finite size scaling to calculate the phase diagrams and critical points for essentially infinite systems. We present calculations for the long-range corrected, the truncated, and the truncated-shifted Lennard-Jones (LJ) fluids. The phase behavior as a function of potential cutoff is examined. Critical parameters are obtained from mixed-field finite-size scaling analysis. Multiple histogram reweighting is used to compute the phase envelop at temperatures well below criticality. We find that there is a systematic difference between the coexistence chemical potentials for the long-range corrected fluids with potential cutoffs of 2.5 and 5.0 times the molecular diameter. There is also a slight but significant difference in the critical temperatures of the two fluids. Our calculations show that the truncated LJ fluid with a cutoff of 5 molecular diameters is a reasonable approximation to the long-range corrected fluid, although not quantitatively correct. We have checked the accuracy of the coexistence chemical potentials obtained from Hill's method against those from Gibbs-Duhem integration and find good agreement between the two methods. We present an extension of the multiple histogram reweighting technique to path integral fluids. For classical fluids the global microcanonical degeneracy is constant. This is the basis for the multiple histogram reweighting technique with the energy used as the degeneracy index. For path integral fluids, the Hamiltonian depends on temperature and hence cannot be used as the degeneracy index. We derive a reference method that allows us to use the rescaled intramolecular energy as one of the indices. We show that this method can be effectively used to compute the properties of quantum fluids in the NVT ensemble.

[121g] - Simulation of Isenthalps and Joule-Thomsom Inversion Curves of Pure Fluids and Mixtures

Fernando Escobedo (speaker) Cornell University School of Chemical Engineering Ithaca, NY 14853-5201 Phone: 607-255-8656Fax: 607-255-9166

Email: escobedo@cheme.cornell.edu

Zhong Chen Cornell University School of Chemical Engineering,Cornell University Ithaca, NY 14853-5201 Phone: 607 255 9166Fax: 607 255 9166 Email: zc19@cornell.edu

Abstract: This work examines the molecular simulation of expansion and compression processes of fluids under common non-isothermal conditions which involve constraints on enthalpy or entropy. It is shown that accurate isoenthalps and isentropes can be traced if simulated configurational properties are complemented by experimentally-based correlations for the ideal-gas contributions to the heat capacity. The problem of simulating inversion curves is also examined and found to be particularly challenging as conventional extrapolation schemes have limited applicability. In contrast to other studies, our calculations show that the Johnson et al. equation of state does provide an accurate description of the inversion curve for the Lennard-Jones fluid. We also simulate isoenthalps and the inversion curve for other model fluids, including a gas condensate mixture.

[121h] - Hydrolysis Reactions in Supercritical Water: A Computer Simulation Study

Robin E. Westacott (speaker) University of Texas, Austin 24th & Speedway Austin, TX 78712 Phone: 512-471-4892Fax: 512-471-1624 Email: r.westacott@mail.utexas.edu

Peter J. Rossky University of Texas, Austin 24th & Speedway Austin, TX 78712 Phone: 512-471-3555Fax: 512-471-1624 Email: rossky@mail.utexas.edu

Keith P. Johnston University of Texas, Austin 26th & Speedway Austin, TX 78712 Phone: 512 471 4617Fax: 512 475 1062 Email: kpj@ce.utexas.edu

Abstract: Hydrolysis reactions are an important class of laboratory reaction that are, at the same time, ubiquitous in such industrial processes as the production of alcohols and ethers, and the destruction of waste organic materials. In ambient water, the first stage of these SN1 reactions corresponds to the formation of ions from a covalent molecular reactant, followed by subsequent reaction of the organic ion to form products. The ionic intermediates are stabilised under these conditions by the strong hydration afforded by the dense solvent water. At the other extreme, in the gas phase, no such solvent stabilisation is available, and radicals are the stable dissociated intermediates formed. In supercritical water, the solvent density, and the corresponding solvating capacity, can be tuned by changing the pressure at constant temperature above the critical temperature. In this paper, we will present the results of molecular dynamics simulations which explore how electrostriction, i.e. the effects of density augmentation around a solute, influence the stabilisation of ionic products in the dissociation of t-butyl chloride in supercritical water at low solvent density. As the solvent density is decreased, the adiabatic reaction free energy surface approaches the shape observed for the gas phase. However, these results differ dramatically from those obtained using a simple Born model approach, which would precit covalent products at much higher solvent densities.

[121i] - How Can Critical Slowing Down Affect Solute Dynamics?

Grant Goodyear (speaker) University of Houston 4800 Calhoun Houston, TX 77204 Phone: (713) 743-2758Email: goodyear@uh.edu

Susan C. Tucker University of California, Davis Dept. of Chemistry, 1 Shields Ave. Davis, CA 95616 Phone: 530-752-2203Email: sctucker@ucdavis.edu

Michael W. Maddox University of California, Davis 1 Shields Ave. Davis, CA 95616 Email: mwmaddox@engr.ucdavis.edu

Abstract: In the vicinity of its critical point, a supercritical fluid exhibits critical slowing down -- slowly fluctuating density inhomogeneities extending over a long range. Yet experimental probes of supercritical fluid dynamics (via a probe chromophore) invariably measure dynamics governed by short-ranged interactions extending, at most, over a few solvation shells. We explore the coupling between these two length scales by simulating the vibrational relaxation of a homonuclear diatomic in a supercritical Lennard-Jones fluid, where we find that critical slowing down leads to inhomogeneous broadening in the relaxation lifetimes. We further explore the mechanism of this coupling by examining the neat fluid, finding an explicit link between the long-range structure and local structural reorganization times.

[143] - Poster Session: Advances in ExtractionChair:Vincent Van BruntUniversity of South CarolinaDepartment of Chemical EngineeringColumbia, SC 29208Telephone Number: 803-777-3115Fax Number: 803-777-8265Email: vanbrunt@engr.sc.edu

Vice Chair:Costas TsourisOak Ridge National LaboratoryChemical Technology DivisionP.O. Box 2008Oak Ridge, TN 37831Telephone Number: 865-241-3246Fax Number: 865-241-4829Email: tsourisc@ornl.gov

[143d] - Solubility of Polar Dyes in Modified Supercritical Fluids

Peter D. Harting (speaker) Institute of Nonclassical Chemistry Permoserstr. 15 Leipzig, D-04318 Germany Phone: ++49 341 235 2574Fax: ++49 341 235 2701 Email: harting@sonne.tachemie.uni-leipzig.de

Uta Lewin-Kretzschmar University of Leipzig Permoserstr. 15 Leipzig, D 04303 Germany Phone: (0341) 9736207Fax: Email: lewin@sonne.tachemie.uni-leipzig.de

Abstract: From the ecological point of view, dyeing from supercritical carbon dioxide is one of the best dyeing procedures. Because of no pollution like waste air or water is produced and the amount of energy used in this technique is lower than in conventional dyeing process [1]. However, hydrophilic and high polar dyes like the conventional wool dyes are not soluble in supercritical carbon dioxide [2,3]. The presented work deals with increasing of the solubility of different polar dyes by modification of supercritical carbon dioxide as well as of supercritical ethane with various ionic and non-ionic surfactants and solvents.

The solubilities were determined by the static-analytical method using an autoclave system in the temperature range of 50 to 100℃ and a pressure range of 100 to 450 bar and analyzed by HPLC with UV/VIS detection. The results are represented and discussed in detail.

In some special cases, like in bis(2-ethylhexyl) sodium sulphosuccinate (AOT)/ ethanol modified carbon dioxide, an significant increasing of the solubility more than 50 times was observed, which can be explained with the forming of microemulsion under these conditions [4].

Furthermore, the experimental data were tried to describe correlatively by using different methods, which make it possible to calculate solubility data under non-investigated state conditions and to assess surfactants, which have not been studied.

[1] D. Knittel, H.J. Buschmann, K. Poulakis, W. Saus, E. Bach, H. Lentz, H. Stahl, E. Schollmeyer: Textilveredlung 26 (1991) 192[2] M. J. Drews, C. Jordan: Proc. AATCC Int. Conference and Exhibition, Charlotte, USA, Oct 11-14 1994, p. 261[3] M. Gie?ann: Unkonventionelle Verfahren zum F?ben von Polyester-Wolle, Diss., RWTH Aachen, 1998[4] B. H. Hutton, J. M. Perera, F. Gieser, G. W. Stevens: Investigation of AOT reverse microemulsions in supercritical carbon dioxide, Colloids and Surfaces A: Physicochem. Eng. Aspects 146 (1999) 227-241

[143e] - A Comprehensive Thermodynamic Analysis of a CO2-Based Heavy Metal Extraction Process

Kevin B. Stallone (speaker) University of Massachusetts, Lowell 40 Roosevelt Avenue

North Attleboro, MA 02760 Phone: (508)695-9123Email: kstallone_40@yahoo.com

Jefferson Tester MIT 1 Amherst Street Room E40-455 Cambridge, MA 02139-4307 Phone: 617-253-3401Fax: 617-253-8013 Email: tester@mit.edu

Francis J. Bonner University of Massachusetts-Lowell 1 University Avenue Lowell, MA 01854 Phone: (978)934-3154Fax: (508) 934-3047 Email: bonnerf@ix.netcom.com

Abstract: The large consumption of zinc slab by the United States, due to the need for the metal in such applications as galvanizing steel, alloys, and materials for the automotive, construction, electrical, and machinery sectors of the economy, has resulted in a surge of interest to develop zinc recovery operations. Hydrometallurgical processes that have been employed in the past to remove zinc metal involves a four step process scheme: (1) Separation of ore from waste rock by crushing and flotation, (2) High temperature oxidation of zinc sulfide to calcine, (3) Leaching of calcine to form concentrated liquors containing very high metal loadings (5000-10000 ppm), and (4) Purification and recovery of the valuable zinc metal product [1]. Scientists and engineers have concentrated their efforts on the purification and recovery step as this represents the most difficult and challenging step because of the stringent design criteria that has been established. Design criteria that the zinc recovery/purification process must satisfy includes the separation process must result in a highly pure metal product (99% pure), must be capable of achieving high recoveries of the metal of interest, minimize the amount of heavy metal contaminants discharged into precious water resources, be viable on an economic scale, and minimize threat to human health and the environment.

Solvent extraction is a well established separation and purification process in the hydrometallurgical and inorganic chemical industries because of the ability to transfer metal ions from an aqueous to an organic phase. While it has been demonstrated both on a commercial and development scale that solvent extraction can remove quantitative amounts of heavy metal from an aqueous to an organic phase, this technique has been targeted by the EPA because it presents a serious environmental, health, and safety impact. Prompted by the need to develop cost effective sustainable technologies which could recover quantitative amounts of zinc from leaching solutions, researchers have examined the use of carbon dioxide as an environmentally benign extraction media.

Supercritical carbon dioxide coupled with chelating agents have shown promise in applications such as environmental cleanup, extraction operations, and production of electronic/ceramic materials. Interest in these green process fluids has grown due to the material's pressure dependent dissolving power, its increased gas-like mobility beyond the critical region, and facile recovery of the solvent. Despite the advantages of supercritical fluids, use of the sustainable technology has met strict resistance because of the high cost of commercial scale supercritical fluid processes. Limited preliminary research conducted by Laintz et. al.[2] has demonstrated that nearcritical carbon dioxide saturated with b-Diketones at system conditions of 1500 psi and 25℃ is a suitable replacement extraction media to supercritical CO2 at conditions of 2800 psi and 42℃ because we can obtain similar liquid-like densities using these materials, while operating at about half the operating pressure of supercritical fluid extractionsystems. Similarly, Beckman and co-workers [3] have shown that nearcritical carbon dioxide coupled with highly CO2-soluble chelating agents at system conditions of 2000 psi and 25℃ can be employed for the removal of heavy metals from solid and liquid matrices. While these experimental accounts have demonstrated the use of nearcritical carbon dioxide for quantitative recovery of the ionic species, these past studies have provided only a limited thermodynamic analysis of CO2 based extraction systems. In order to properly evaluate the extraction performance of CO2/chelating agents, however, the extraction efficiency of these separation systems must be examined over a wider range of temperatures and pressures. While the formation of metal chelates and partitioning of metal complexes into supercritical CO2 has been examined in gross detail, the thermodynamics of nearcritical carbon dioxide/complex mixtures has not been mapped out completely.

Unlike previous efforts, the intent of our research program is entirely different in that we conduct a comprehensive thermodynamic analysis of nearcritical carbon dioxide/fluorinated chelating agent extraction systems. That is, in our experimental investigation the extraction performance of these CO2 based separation systems are mapped out over a larger pressure and temperature range of P=1000-1500 psi and T=10-25℃. Zinc is chosen as the model metal because of its importance to the hydrometallurgical industry and also due to its coordination chemistry. A perfluoroether alkylamine chelating agent was selectedbased on its high solubility in the CO2 phase (@860 psi 25℃ solubility in CO2=15 wt%) and ability to form stable metal complexes with zinc metal (Kf=1013). Experimental extraction efficiencies ranged from 40 to 99% and increased with increasing the molar ratio of chelating agent to metal and CO2 density. All in all, this thorough evaluation of the thermodynamics of a nearcritical carbon dioxide extraction process will not only result in the optimal design of extraction processes but also improve understanding of mechanisms responsible for separation and aid in the development of models for the simulation of commercial scale CO2 based extraction systems at different system temperatures and pressures and for use in the design of laboratory experiments.

[1] Rousseau, R.W., Handbook of Separation Process Technology; John Wiley& Sons, Inc.:New York, 1987.[2] Laintz, K.E.; Hale, C.D.; Stark, P.; Rouquette, C.L.;Wilkinson, J. A Comparison of Liquid and Supercritical Carbon Dioxide as an Extraction Solvent for Plating Bath Treatment. Anal. Chem. 1998, 70(2), 400-404.[3] Yazdi, A.V.; Beckman, E.J. Design, Synthesis, and Evaluation of Novel, Highly CO2-Soluble Chelating Agents for Removal of Metals. Ind. Eng. Chem. Res. 1996, 35, 3644-3652.

[143h] - Removal of Paraffin-Based Wax from Wax-Coated Old using Supercritical Carbon Dioxide

Gerardo A. Montero (speaker)

North Carolina State University 2401 Research Drive Raleigh, NC 27695 Phone: (919)515-7537 or 515-6958Fax: (919)515-6532 Email: gmontero@tx.NCSU.EDU

Richard D Venditti North Carolina StateUniversity Campus Box 8005,Room 1204, Biltmore Hall Raleigh, NC 27695-8005Phone: (919) 515-6185Fax: (919) 515-6302

Thad C Stauffer North Carolina State University Campus Box 8005, Biltmore Hall Raleigh, NC 27695-8005 Phone: (919) 515-8591Fax: (919) 515-6302

Abstract: The removal of paraffin-base waxes from old corrugated containers (OCC) with supercritical carbon dioxide (SC-CO2) has been investigated in this work. Paraffin wax is the solid material of the paraffinic distillate obtained as a by-product of petroleum refining. Wax contamination is a significant operational problem in mills recycling OCC. The presence of paraffin waxes (straight-chain hydrocarbons "n-alkanes", etc.) in fiber reduces the coefficient of friction, the wettability, interfiber bonding, and also impairs the printability and gluability of the final products. Presently, due to the difficulties in recycling wax-coated corrugated containers, this small amount is separated from uncoated OCC and sent to landfill.

Laboratory-scale experiments have shown it possible to quantitatively de-wax air -dry, unpulped wax containing OCC using SC-CO2 extractions. These preliminary results obtained for the SC-CO2 extraction of both saturated and curtain-coated containers are evaluated and compared using the conventional method of extraction with an organic solvent in a Soxhlet system. The results showed that more than 99% removal of saturated can be achieved by using pure carbon dioxide under operating supercritical conditions. Also, extraction efficiency decreases at lower pressures (<300 atm), due to the decreased value of SC-CO2 density. Finally, supercritical fluid extraction is a viable alternative technology for removal of paraffin waxes from old corrugated containers.

[143k] - Reducing Problems of Cyclic Trimer Deposits in Supercritical CO2 Dyeing Equipment

Gerardo A. Montero (speaker) North Carolina State University 2401 Research Drive Raleigh, NC 27695 Phone: (919)515-7537 or 515-6958Fax: (919)515-6532 Email: gmontero@tx.NCSU.EDU

Abstract: The present paper describes the alternative procedure or method for the minimization or elimination of oligomeric polyester (PET) residues in supercritical CO2 (SC-CO2) dyeing machines. When polyester fibers are processed, small amounts of relatively low molecular weight (oligomeric) aqueous insoluble esters are extracted from the substrate. The extracted fine-particle cyclic trimer (oligomers) build-up on the interior surface of stainless steel machinery, presenting significant problems in terms of preventative maintenance and reduced processing efficiency. Furthermore, the presence of aqueous insoluble oligomers on the surface of the PET product being processed can significantly reduce its quality.

A new dyeing methodology using SC-CO2 has been demonstrated successfully at the pilot plant level, and the process is currently being scaled up to production scale. However, accumulation of fine-particle trimer (and other oligomers) deposits in the supercritical dyeing machinery is significant and is reducing the maximum circulation of dye-bath. Based on current process dyeing conditions, there is a severe amount of cyclic trimer extracted from the PET. In fact, after only short periods of operating time at elevated dyeing temperatures, a coating of trimer may be seen on the inside walls of all parts of the process equipment. In severe cases, trimer deposits plugged inlet-outlet flow transfer pipes. The most serious problems are encountered when polyester yarn is dyed under high pressure. The cyclic trimer issue is a very significantly problem in conventional aqueous dyeing of polyester.

Degradation or removal of the trimer is difficult owing to its high aqueous insolubility, and adherence to surfaces. Hence, elimination of oligomers following PET processing via efficient and environmentally responsible routes is highly desirable. To date, no such process exists, despite several industries having a demonstrated need for this technology, include textile dyeing and finishing operations, and fiber and film extrusion operations. Presently, oligomer is removed from equipment via high temperature aqueous hydrolysis involving strong alkali and surfactants. The oligomer degradation process produces toxic effluent, is time and energy inefficient, and may damage equipment, particularly high-pressure seals, for instance.

Trimer formation in the dye-bath is influenced by several factors. Unfortunately, dyeing at high temperatures (above 120 oC) provides optimum conditions for the extraction of trimer from the polyester yarn. Generally the higher the dyeing temperature, the faster the rate of extraction. Also, dyeing cycle time controls the rate of extraction. As the dye cycle is longer, trimer deposits increase. In summary, the following factors affect trimer extraction in the dye-bath: high dyeing temperatures, low liquor ratios, and high liquor flows.

Currently, there is no information available with respect to the control or removal of trimer with supercritical fluids. Supercritical fluids (e.g. carbon dioxide "CO2") have unique properties beyond their critical point. For example, they exhibit densities and solvating powers similar to liquid solvents, yet have extremely rapid diffusion characteristics and viscosity closer to those of a

gas. Supercritical CO2 is one of the most environmentally acceptable solvents "driving force" in use today and textile processes using this solvent have many advantages when compared to conventional aqueous processes. In an effluent-free dyeing process, SC-CO2, which more resembles a gas more than it does a liquid, serves as the medium for the dyeing of polyester fibers with pure disperse dyes. Positive environmental effect range from drastically reduced water consumption to eliminating hazardous industrial effluent. Furthermore, economic benefits include increased productivity and energy savings.

Removal of trimer build-up in the current supercritical fluid dyeing machine has been done with the conventional procedure used to strip the kiers in aqueous dyeing. The solution of water and quaternary salts has been successful in removing trimer from the stainless steel vessels and piping. However, thecrystalline trimer is not completely dissolved and produces slurry. The trimer slurry appears crystalline in nature and there are concerns that it will damage close tolerance components such as pumps, valves, and seals on dyeing machines.

[150] - Advances in Supercritical Fluid ExtractionChair:Ruben CarbonellNorth Carolina State University1017 Main Campus DriveCentennial Campus, Partner's Building IRaleigh, NC 27695-7006Telephone Number: 919-515-5118Fax Number: 919-515-5831Email: ruben@ncsu.edu Vice Chair:George RobertsNorth Carolina State UniversityRaleigh, NC 27695Telephone Number: 919-515-7328Email: groberts@eos.ncsu.edu

[150a] - Supercritical Fluid Extraction of Proteins with Reverse Micelles

Leo J. Vandenbroeke Eindhoven University of Technology PO Box 513 Eindhoven, 5600 MB The Netherlands Phone: +31-40-2473675Fax: +31-40-2446104 Email: L.J.P.van.den.broeke@tue.nl

Abstract:

Introduction The isolation of proteins from complex media, e.g. fermentation broth and dilute solutions, like whey and blood, is in general very difficult. Multi-step separation processes are in many cases necessary to isolate the desired products. An efficient and scaleable bioseparation process is fluid - fluid extraction with reverse micelles. The ability to extract a wide range of polar solutes, including proteins, from dilute complex aqueous solutions with reverse micelles in an organic solvent has been studied extensively [1]. Besides losses of the organic solvent, the disadvantage of this method is that high amounts of salts are produced in the different neutralization steps involved. One way to circumvent these problems is by using supercritical fluids instead of organic solvents. In this project, the aim is to develop a one-step separation process for the extraction of a specificcompound from complex media. Clearly, this will result in a large reduction in separation costs. Focus will be on the selective extraction of proteins. Carbon dioxide in the supercritical fluid state can be a suited alternative for the use of toxic organic solvents. Over the past decade, considerable research has been dedicated to the development of surfactants capable of forming reverse micelles in carbon dioxide. Different surfactants have been designed where the hydrophilic head groups form a core and the CO2 - philic tails project into the CO2 - continuous phase [2].

Results Novel fluorinated surfactants have been developed, in our laboratory, capable of solubilizing a large amount of water in carbon dioxide. These surfactants were used to extract the proteins Bovine Serum Albumine and Lactoferrin from an aqueous phase with high efficiency [3]. The extraction of single component systems, i.e. one type of protein in an aqueous phase, as well as the extraction of mixtures of proteins were studied. A process design will be presented in which reverse micelles in supercritical carbon dioxide are used to extract proteins from aqueous solutions. The process basically consists of two stages: an extraction and a regeneration step. In the latter step the desired protein is recovered from the reverse micelles. This recovery can be achieved by adjusting the pressure and/or temperature. Selectivity towards a given protein can be tuned by manipulation of the pressure during the extraction step. In supercritical fluids the curvature of reverse micelles can be varied for specific purposes by means of the pressure. In this way extraction of a specific protein by size-selectivity is realized. For the recovery of the proteins from the reverse micelles a squeezing out effect has been observed for large proteins like Bovine Serum Albumin and LactoferrinL. This effect is crucial for the design of an efficient separation process for valuable biochemicals, like proteins and antibodies. Preliminary conclusions are drawn on the capability of extracting polar solutes by reverse micelles in carbon dioxide. The way the selectivity of the extraction step is influenced by temperature and pressure is examined by the use of dendrimers as a model system for proteins. The use of dendritic molecules as model components in an extraction process shows that this type of molecules can be a versatile tool to gain more insight into the uptake behaviour of solutes by reverse micelles [4].

References [1] M. Dekker, R. Hilhorst and C. Laane (1989) Analyt. Biochem., 178, 217. [2] E.L.V. Goetheer, M.A.G. Vorstman and J.T.F. Keurentjes (1999) Chem. Eng. Sci., 54, 1589. [3] E.L.V. Goetheer, L.J.P. van den Broeke and J.T.F. Keurentjes (2000) Proceedings 5th Int. Symp. Supercritical Fluids

(ISSF2000), Atlanta GA, USA. CD-rom of Abstracts. [4] E.L.V. Goetheer, M.W.P.L. Baars, M.A.G. Vorstman, E.W. Meijer and J.T.F. Keurentjes (1999) Proceedings 6th Meeting Supercritical Fluids, Nottingham, UK. Book of Abstracts, p. 507.

[150b] - Production of Mesophase Pitch by Supercritical Extraction:

Mark S. Zhuang (speaker) Clemson University Dept of Chemical Engineering Clemson, SC 29634-0909 Phone: 864 656 5904Fax: 864 656 0784 Email: szhuang@clemson.edu

R. Twain Pigott Clemson University Dept of ChemicalEngineering Clemson, SC 29634-0909 Phone: 864-656-3055Fax: 864-656-0784

Mark C. Thies Clemson University Dept of Chemical Engineering Clemson, SC 29634-0909 Phone: 864-656-3056Fax: 865-656-0784 Email: mcths@clemson.edu

Abstract: Near critical and supercritical extraction is being investigated by our group for the production of mesophase pitch, a discotic liquid crystalline material that is an excellent precursor for high-performance carbon products, such as high thermal conductivity carbon fibers. In our process, an inexpensive isotropic petroleum pitch is extracted with toluene in a region of liquid-liquid equilibrium at elevated temperatures and pressures (e.g., 600K and 100 bar). At the appropriate operating conditions, the denser liquid phase contains the desired mesophase material.

An economic analysis of a continuous process for producing mesophase pitch via supercritical extraction was performed using Aspen Plus. The feedstock for the process was an inexpensive, heat-soaked isotropic pitch that is readily available as a by-product of petroleum refining. Toluene was used as the extractive solvent, and the liquid-liquid separator operated at 593K, 94 bar, and a solvent-to-pitch ratio of 3.5:1, conditions that were used to produce mesophase pitch in our laboratory. Significant modifications to the Peng-Robinson equation had to be made, using experimental data obtained in our laboratory, in order to obtain reasonable results in Aspen. In addition, SAFT had to be used to describe the liquid-liquid separation. Results indicate that mesophase pitch can be produced with this process for less than $4/kg. This is less than half of the current selling price for Mitsubishi's AR mesophase, which is produced by the catalytic polymerization of naphthalene.

Although SAFT is the best equation of state currently available for modeling mixtures of petroleum pitch and supercritical solvents, its predictions of the product yield in our process are fair at best. Our efforts to obtain a set of pure component SAFT parameters that are more applicable to the polynuclear aromatic oligomers that comprise pitches will also be discussed.

[150c] - Polyimide Formation in a Supercritical Medium

M. P. Srinivasan (speaker) National University of Singapore 4 Engineering Drive 4 Singapore, 117576 Singapore Phone: (65) 874 2171Fax: (65) 779 1936 Email: chesmp@nus.edu.sg

Abstract: Polyimides are thermally and mechanically robust polymers that are infusible and insoluble in their final states on account of their extended rigid planar aromatic and heteroaromatic structures. They find extensive application in high temperature situations, and in the electronics industry and are typically obtained by a two-step synthesis; a soluble polyimide precursor is obtained in the form of an acid, ester or salt and is converted to polyimide by thermal or chemical treatment. Thermal imidisation is carried out at temperatures in the range 250o-350oC while chemical imidisation is performed with mixtures of aliphatic carboxylic acid anhydrides (dehydrating agent) and tertiary amines (that catalyse the cyclodehydration) in an aromatic solvent such as benzene. As part of an effort to improve the processing method and properties, we employed carbon dioxide at supercritical conditions as the reaction and transport medium and as the extraction solvent for performing chemical imidisation of spin-coated films of polyamic acid precursor. The advantageous solvating and transport properties of matter in the supercritical state and the solubility of the reactants in the supercritical medium is exploited in this application. The thermal properties of the resulting films are similar to conventionally imidised films. The imidisation reaction is completed more rapidly than in benzene and requires much smaller quantities of reagents. Further, excess and spent chemicals can be completely removed from the matrix. The film morphology depended on the conditions of imidisation, viz. temperature and pressure; employment of a higher carbon dioxide density ensured that imidisation proceeded to completion more rapidly. However, longer times were needed to complete the imidisation if carbon dioxide was at subcritical temperatures. Apart from enabling formation of polyimide at a more controllable, efficient and environmentally benign manner, chemical imidisation in a supercritical medium is very advantageous for fabricating functional composite structures containing thermally sensitive or soluble guest species. This has been demonstrated by the formation of a composite polyimide film with a conducting surface (of poly dodecylthiophene), and by assembling a Langmuir-Blodgett film of containing polyimide and an organic semiconductor (copper butoxy phthalocyanine). Conventional imidisation of these films yielded final structures devoid of functional properties.

[150d] - Development of Operational Strategies and Optimization

Marcela Mota Santos UNICAMP CP 6066 Campinas, Sao Paulo 13083-970 Brazil Phone: 55 11 7883909Fax: 55 11 7883965 Email: marcela@lopca.feq.unicamp.br

Edinara Adelaide Boss UNICAMP 6066 Campinas, Sao Paulo 13083-970 Brazil Phone: 55 19 7883909Fax: 55 19 7883965 Email: boss@lopca.feq.unicamp.br

Rubens Maciel Filho (speaker) UNICAMP 6066 Campinas, Sao Paulo 13083-970 Brazil Phone: 55 19 7883909Fax: 55 19 7883965 Email: maciel@feq.unicamp.br

Abstract: Since the third decade of the century XX, the conventional oilseed processing uses hexane as solvent. The search of solvents to oil extraction has been intensified to minimize the environment damage and operational risks, as the hexane is toxic and highly flammable. The carbon dioxide supercritical has been seen as a potential solvent for the substitution of hexane because it is not toxic, not flammable, its supercritical conditions are relatively mild (31℃ and 73.8 bar) and it is available at low cost. This work uses a model where the extractor is represented by a set of differential partial equations in respect to time and extract axial distance. The equations are solved by the method of lines, using finite differences to discretize the axial variable and the time variable integration being carried out by the LSODE algorithm. The dynamic model allows for extensive simulation to be done, so that it is possible to observe that the design as well as operational variables have more significant impact on the system behaviors. This model was submitted to a parametric sensitivity analysis made by means of a complete factorial design in two levels. Using this procedure it was also possible to identify the interactions among the variables studied. Besides, the parametric sensitivity analysis afforded the extraction process optimization. This kind of information is useful to the operational strategy definition as well the control structure.

[150e] - Supercritical Fluid Desorption from Modified Clays

Gerson L. V. Coelho (speaker) UFRRJ Av. das Am?icas, 22500 Rio de Janeiro, 22785-210Brazil Phone: 55-21-4282487Fax: 55-21-4282487 Email: coelho@ufrrj.br

Abstract: The supercritical regeneration with carbon dioxide of modified and unmodified clays was experimentally studied after its use to adsorb ethyl acetate from aqueous solutions.Two quaternary amine modifiers (HDTMA+ and TMA+) were used. The desorption of ethyl acetate adsorbed over the clays was performed with CO2 at temperatures ranging from 301 K to 333 K and pressures ranging from 69.0 bar to 413.8 bar.The regeneration capacity was almost coincidental and high pressure was more favorable to regeneration.The effect of pressure and temperature was characterized under different conditions (gas, liquid andsupercritical) and the supercritical was shown to be the best. A cross-over effect was observed. The experimental data was fitted to a simple model, being the best results corresponding to desorption with CO2 in its supercritical region.

[150f] - Measurements of Binary Diffusion Coefficients of Some Vitamins and Derivatives in Supercritical Carbon Dioxide by a Tracer Response Technique with Capillary Column Coated with Polyethylene Glycol

Toshitaka Funazukuri (speaker) Chuo University Department of Applied Chemistry 1-13-27 Kasuga, Bunkyo-ku BUnkyo-ku, Tokyo 112-8551 Japan Phone: +81-3-3817-1914Fax: +81-3-3817-1895 Email: funazo@apchem.chem.chuo-u.ac.jp

Abstract: Binary diffusion coefficients D12 of some vitamins and their derivatives such as alpha-tocopherol, beta-carotene, Vitamin K3 and linoleic acid methyl ester in CO2 were measured by a tracer response technique with a capillary column coated with polyethylene glycol at 308 and 313 K in the pressure range from 9 to 30 MPa. The determination of the D12 value and the partition coefficient k from the response curve was made by the curve fitting method instead of the moment method. The

accuracy in the determined values was evaluated in terms of the peak distortion, fitting error and peak area (detector linearity). The measured D12 values were represented with the Schmidt number correlation. The D12 values measured using the Taylor dispersion method (by injecting the solute dissolved in an organic solvent) were also compared with those with the coated capillary column. The difference in the D12 values for both methods were inappreciable.

[280] - Separations in the Food & Pharmaceutical Industry

Chair:Surya MallapragadaIowa State UniversityDepartment of Chemical EngineeringAmes, IA 50011-2230Telephone Number: 515-294-7407Fax Number: 515-294-2689Email: suryakm@iastate.edu

Vice Chair:Padma NarayanNational Starch and Chemical Co.10 Finderne AveBridgewater, NJ 08807Telephone Number: 908-685-5703Fax Number: 908-685-5552Email: padma.narayan@nstarch.com

[279aj] - Using High-Pressure Carbon Dioxide For The Isoelectric recipitation Of Food Proteins.

G. W. Hofland (speaker) Delft University of Technology Leeghwaterstraat 44 Delft, 2628 CA The Netherlands Phone: +31 15 278 3839/6678Fax: +31 15 278 6975 Email: g.w.hofland@wbmt.tudelft.nl

G. J. Witkamp Delft University ofTechnology Leeghwaterstraat 44 Delft, 2628 CA The Netherlands Phone: +31 15 2786678Fax: +31 15 2786975 Email:

L. A.M. Van der Wielen Delft University of Technology Julianalaan 67 Delft, 2628 BC The Netherlands Phone: +31 15 278 2361

Abstract: High-pressure carbon dioxide has extensively been investigated for its solvent roperties in (enzymatic) reactions, extraction and anti-solvent crystallization rocesses. It can also be applied for its ability to acidify aqueous solutions, as a nvironmentally benign replacement of mineral acids like sulfuric acid. For that eason, carbon dioxide was applied for the isoelectric precipitation of food roteins, particularly soy protein and casein, which have isoelectric points at pH 4.5-5. Experiments showed that the precipitation yield appeared to be as good as in conventional processing. After release of the pressure a close to neutral whey is obtained. Such a reversible acidification is advantageous because of the absence of precipitant in the product and because of the reduction of the amount of salts that accumulate throughout the processing and that eventually have to be disposed. Additionally, applying carbon dioxide as a volatile electrolyte appeared also to have advantages for the control of the precipitation process. The pH of the solution can be easily controlled by pressure and exhibits no local overshoot at the inlet. This advantage was exploited for the production of a more defined particulate product as well as for fractionation of protein fractions. Experiments were done both in batch and continuously to establish the influences of pressure and temperature as well as the dynamics of the process on the product quality.

[285] - Drying Technology & Supercritical Fluid in Food and Pharmaceutical Processing Chair:Mike SowaMerck & Co., Inc.Chemical Engineering Research & Development

P.O. Box 2000Rahway, NJ 07065Telephone Number: 732-594-1928Email: mike_sowa@merck.com

Vice Chair:Johannes G. KhinastRutgers UniversityDepartment of Chemical and Bioengineering Engineering98 Brett RoadPiscataway, NJ 08854-8058Telephone Number: 732-445-2970Fax Number: 732-445-2581Email: khinast@sol.rutgers.edu

[285g] - PHOTOPOLYMERIZATION AND COMPRESSED ANTISOLVENT PROCESSING OF CROSSLINKED DEGRADABLE MICROPARTICLES FOR DRUG DELIVERY

Jennifer L. Owens (speaker) University of Colorado Engineering Center, ECCH 111 Boulder, CO 80309 Phone: (303) 492-1681Fax: (303) 491-4341 Email: jennieo@colorado.edu

Kristi S. Anseth University of Colorado, Boulder Chemical Engineering Dept. Engineering Center ECCH111 Boulder, CO 80309-0424 Phone: 303-492-7471Fax: 303-492-4341 Email: anseth@stripe.colorado.edu

Theodore W. Randolph University of Colorado One Engineering Drive Boulder, CO 80309-0424 Phone: (303)492-4776Fax: (303)492-4341 Email: theodore.randolph@colorado.edu

Abstract: Polymer microparticles have been realized as advantageous in many controlled release devices with applications ranging from pharmaceutical to agricultural purposes. Many of these applications require degradable particles with low residual solvent levels, high additive encapsulation efficiencies, processes with low operating temperatures, control of particle size and morphology, and efficient bulk production capability.

Recently, we developed the ability to photopolymerize multifunctional monomers during the precipitation with a compressed antisolvent to form degradable crosslinked networks. Advantages of this photopolymerization technique include morphological control through polymerization rate, process conditions, and initiation location. Processing time remains short while processing temperatures remain low. Low operating temperatures are important since many potential encapsulation additives will degrade at even moderate temperatures. In this novel process, an organic solvent dissolves monomer and photoinitiators to form a homogeneous solution. Photopolymerization occurs when these homogeneous solutions are exposed to initiating light while being simultaneously sprayed into a compressed antisolvent (supercritical CO2). This polymerization results in microparticles with a wide range of diameters, adjustable by changing the process conditions.

Solutions of acrylated degradable poly ethylene glycol (PEG) or polyanhydride macromers dissolved in methylene chloride with photoinitiator were injected into the high-pressure chamber at flow rates between 0.1 and 1 ml/min. The optically accessible chamber was maintained at a pressure of 85 bar and 35 C with deoxygenated CO2. A high powered light source provided the necessary photons to initiate photopolymerization. The chamber conditions coupled with the antisolvent properties facilitated the extraction of the solvent from the solution leaving mostly monomer and initiator. At the same time, these monomer/initiator particles received photons from the source, initiating the polymerization.

Fine polymer powders consisting of particles ranging in size from 5 to 15 microns have been consistently produced. Scanning electron microscopy is used to characterize the particle size. Modeling of this process allows us to predict the size of the particles with changing process conditions. Fourier transform infrared (FTIR) spectroscopy of these particles confirmed the formation of crosslinked polymer microparticles. The noticeable carbon-carbon double bond peak at 1635 wavenumbers present in the dimethacrylated sebacic anhydride oligomer compared with the absence of this peak in the polymer microparticles signifies the reaction of the carbon-carbon double bond to form a crosslinked network.

Hydrophobic Ion Pairing (HIP) was used in conjunction with this process to encapsulate drug within the polymer microparticles. HIP enables the formation of homogeneous solutions of drug, monomer, and initiator in an organic solvent and photopolymerize drug encapsulated microparticles using this process. Since most drugs are hydrophilic, the exchange of polar counterions with ionic molecules (HIP) on the drug is necessary to ensure the drug will dissolve in the solvents used to dissolve the macromer and initiator. Drug/polymer homogeneity was measured using a fluorescence microscope and drug release characterized using absorbance and/or fluorescence spectroscopy.

[285i] - Selective Extraction of Phosphatidyl Choline from a Phospholipid Concentrate Using Supercritical CO2 and Ethanol

Leyla Teberikler (speaker) Texas A&M University Chemical Engineering College Station, TX 77843 Phone: 979 845 0354Email: l0t2184@chennov.tamu.edu

Sefa S. Koseoglu Texas A&M University Food Protein Research and Development CenterCollege Station, TX 77843 Phone: (979) 845-2749

Aydin Akgerman Texas A&M University Chemical Engineering Department College Station, TX 77843 Phone: (979)845-3375

Abstract: Extraction of phospholipids from deoiled soybean lecithin and oil from a phospholipid concentrate (30% oil, 70% phospholipids), using supercritical fluid (SCF) mixtures of carbon dioxide and ethanol was studied. Deoiled lecithin was used as a model mixture in order to explore the optimum conditions to obtain high purity, pharmaceutical grade phosphatidyl choline(PC) from the phospholipid concentrate (obtained as the membrane retentate of the oil refining process recently developed by Food Protein Research and Devepolment Center in Texas A&M University) after removal of the oil. During the extraction of phospholipids from the deoiled lecithin, temperature was varied between 60 and 80 oC at pressures of 17.2 and 20.7 MPa with ethanol weight fractions of 0.1 and 0.125. Constant rate of extraction of the individual phospholipids was observed for 150minutes during which the extractions were carried out. Pressure and ethanol fraction had a positive effect, whereas temperature had a negative effect on the selective extraction of PC. Under all the conditions studied, the extracts were mainly composed of PC while the extarction of the other phospholipids was very low. Extraction at 20.7 MPa and 60 oC with 10% Ethanol/90% CO2 supercritical fluid mixture resulted in 95% selectivity to PC. Presence of 10% ethanol also made it possible to remove the oil from the phospholipid concentrate at 17.2 MPa and 60 oC, while no significant oil extraction was observed when using neatcarbon dioxide at the same conditions.

[285j] - Biomolecules Supercritical Extraction. Process Simulation and Optimization

Susana Espinosa PLAPIQUI Camino la Carrindanga Km 7 - CC717 Bahia Blanca, 8000 Argentina Phone: 0054-291-4861700Fax: 0054-291-4861600 Email: espinosa@plapiqui.edu.ar

Maria S. Diaz PLAPIQUI Camino La Carrindanga Km 7 Bahia Blanca, Buenos Aires8000 Argentina Phone: 54 291 4861700Fax: 54 291 4861600 Email: sdiaz@plapiqui.edu.ar

Esteban A. Brignole (speaker) PLAPIQUI Camino La Carrindanga Km7 - CC717 Bahia Blanca, 8000 Argentina Phone: 00-54291-861700Fax: 00-54291-861600 Email: prbrigno@criba.edu.ar

Abstract: Experimental separation of biomolecules from natural source, such as fish oil derivatives with supercritical carbon dioxide has been reported in the literature. However, most authors point out that there is a need for process simulation and optimization in these processes. Fish oil derivatives in the form of w 3 fatty acids are increasingly in demand as pharmaceutical products, food additives and health supplements. Among the components of interest are concentrates of EPA (eicosapentaenoic acid and DHA (docosahexaenoic acid).

We have developed a rigorous simulator for supercritical fluid processes integrated to an SQP (Successive Quadratic Programming) algorithm (Biegler and Cuthrell, 1985) and supported by a Group Contribution Equation of State (Skjold-Jorgensen S., 1984), for the determination of optimal process schemes and operating conditions in a variety of supercritical fluid processes. Recent work includes the synthesis and optimization of extraction and dehydration of oxychemicals from aqueous solutions (Gros et al., 1998), removal of pollutants from fatty oils (Espinosa et al., 2000), deterpenation of citrus peel oils (Espinosa et al., 2000) and separation of fatty acid alkyl esters (Diaz et al., 2000).

In this work, we have rigorously modeled pure esters and fish oil fatty acid esters mixtures with a group contribution equation of state. By application of the supercritical fluid process simulator optimizer, optimal schemes and operating conditions for both

the minimization of solvent recycle and maximization of products recovery and purity have been determined for the fractionation of fish oils alkyl esters using high pressure CO2 as entrainer.

Furthermore, the addition of different entrainers or mixtures of supercritical fluids (carbon dioxide + propane) and its effect on process economics has been studied. Simulation results show good agreement with reported experimental data.

[285k] - The Effect of Compressed Solvents on the Biocompatibility and Product Selectivity of Thermophilic Bacteria

Jason A. Berberich (speaker) University of Kentucky 177 Anderson Hall Lexington, KY 50526 Phone: 859-257-2300 x244Fax: 859-323-1929 Email: jasonb@pop.uky.edu

Barbara L. Knutson University of Kentucky 157 Anderson Hall Lexington, KY 40506-0046 Phone: (606)257-5715Fax: (606)323-1929 Email: bknutson@engr.uky.edu

Herbert Strobel University of Kentucky 212 W.P. Garrigus Building Lexington, KY 40546-0215 Phone: (606) 257-7554Fax: (606) 257-5318 Email: strobel@pop.uky.edu

Sue Nokes University of Kentucky 128 AG. ENGR. BLDG Lexington, KY 40546-0276 Phone: (859) 257-3000Fax: (859) 257-5671 Email: snokes@bae.uky.edu

Sefa Tarhan University of Kentucky 128 AG. ENGR. BLDG Lexington, Ky 40546-0276 Phone: (859) 257-3000

Abstract: Organic solvents are increasingly employed in biosynthetic processes for the in-situ removal of metabolic products and as a reaction media for enzymes and whole cells. The advantages of in-situ extraction include the possibility to diminish substrate and product inhibition, to affect product selectivity, to enhance product recovery, and to increase product yield. The unique ability to tune solvent properties with temperature and pressure makes supercritical fluids interesting both as extracting solvents and as media for biocatalytic reactions. The manipulation of enzyme activity and selectivity with changes in solvent properties has already been demonstrated in supercritical fluids. However, there are few reports of successful whole cell metabolism in the presence of supercritical fluids. This investigation examines the effect of compressed and supercritical fluids on product formation and selectivity. Metabolic activity and product selectivity is reported as a function of compressed solvent for the biphasic fermentation of resting cells of the thermophilic, anaerobic bacterium Clostridium thermocellum. The presence of compressed solvents leads to an increase in the ratio of ethanol to acetate produced by the organism. Furthermore, lactate formation was decreased in the presence of compressed and liquid hydrocarbon solvents. The reduction of lactate formation is associated with a simultaneous reduction in the rate of cellobiose uptake by the microorganism. The decreased cellobiose uptake may be due to the interaction of solvent molecules with the membrane of the microorganism. This supports the claim that incompatible solvents affect the membrane and transport systems of the microorganism. This ability to tune solvent biocompatibility and product selectivity with compressed solvent properties has important implications to the in-situ biphasic extraction of fermentation products as well as to the understanding of the role of solvents on bacterial inactivation.

[339f] - Exploiting Supercritical Fluids in Homogeneous and Heterogeneous Reactions: Potential and Challenges

Bala Subramaniam (speaker) University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785-864-2903Fax: 785-864-4967 Email: bsubramaniam@ukans.edu

Abstract: The potential applications of supercritical reaction media have greatly expanded in recent years to include industrially significant reactions such as selective catalytic oxidations (fine and agricultural chemicals), fixed-bed hydrogenations (pharmaceuticals, chemical intermediates), polymerizations, hydroformylations (petrochemical), and solid-acid catalyzed alkylations (petroleum refining). The pressure-tunable density and transport properties of supercritical media have been exploited in chemical reaction systems in numerous ways such as these: eliminating O2 or H2 solubility limitations in the liquid phase in multiphase reaction systems; enhanced desorption and transport of heavy molecules (such as coke precursors) in mesoporous catalysts, alleviating

pore-diffusion limitations and improving catalyst effectiveness; in situ removal of primary products stabilizing primary product selectivity; enhanced heat capacity ameliorating the problem of parametric sensitivity in exothermic fixed-bed reactors; and facileseparation of reactants and products. Supercritical reaction systems are thus excellent examples of the "multifunctional reactor" concept.

This talk will highlight recent advances in exploiting supercritical media in chemical and catalytic reaction systems, including processes at the plant development stage. Examples of environmentally-benign catalytic processing, such as those in which conventional solvents are replaced by supercritical carbon dioxide, will be highlighted. It will be shown that traditional approaches for multiphase reactor selection and modeling can be applied to systematically analyze and develop supercritical reaction systems. Future horizons and challenges in this promising field will be discussed.

[340] - Reactions in Supercritical FluidsChair:Bala SubramaniamUniversity of Kansas4006 Learned HallLawrence, KS 66045Telephone Number: 785-864-2903Fax Number: 785-864-4967Email: bsubramaniam@ukans.edu

Vice Chair:Keith HutchensonE.I. duPont de Nemours & CoExperimental StationP.O. Box 80304Wilmington, DE 19880-0304Telephone Number: 302-695-1389Fax Number: 302-695-3501Email: keith.w.hutchenson@usa.dupont.com

[340a] - Measurements of Hydroxyl Radical Reactivity in upercritical Water Using Pulse Radiolysis

Joan F. Brennecke University of Notre Dame 182 Fitzpatrick Hall Notre Dame, IN 46556 Phone: 219-631-5847Fax: 219-631-8366 Email: jfb@nd.edu

Junbo Feng (speaker) University of Notre Dame 100 University Vlg, Apt J2 Notre Dame, IN 46556 Phone: 219-243-2885Fax: 219-631-8366 Email: jfeng@bach.helios.nd.edu

Sudhir N. V. K. Aki University of Notre Dame Department of Chemical Engineering South Bend, IN 46556 Phone: 219-631-5507Fax: 219-631-8366 Email: asudhir@nd.edu

John E. Chateauneuf Western Michigan University Department of Chemistry Kalamazoo, MI 49008 Phone: 616-387-2879Email: John.Chateauneuf@wmich.edu

Abstract: Supercritical water oxidation (SCWO) has been known as an efficient and nvironmental benign technology for the complete destruction of hazardous rganic waste.

The most detailed approach of modeling SCWO has described SCWO process in erms of elementary free radical reactions which are known to be dominant under typical reaction conditions of 550-650℃. In this presentation, we wish to present our efforts of experimentally verifying that SCW will support free radical reactions and understanding the effects of SCW on diffusion controlled free radical reactions.

Hydroxyl radical (OH·) has been identified as the primary oxidizing species in SCWO. Unfortunately, under actual SCWO conditions, multiple reactions occur simultaneously and concentration of OH· is sufficiently low that reactions of OH· can't be studied individually. We report for the first time on the production of high concentrations of hydroxyl radical in water under subcritical and supercritical conditions using pulse radiolysis. In addition, we report the bimolecular rate constants for the reaction of hydroxyl radical with nitrobenzene at temperatures from ambient to 450 ℃ and pressures to 300 bar. The reaction kinetics is monitored by detection of the product, the nitrohydroxycyclohexadienyl radical, which absorbs in the ultraviolet region.

The pressure and temperature effects on the bimolecular rate constant in the supercritical region are investigated. Since this reaction is known to be diffusion controlled in ambient aqueous solutions, we compare the results in subcritical and supercritical water with those estimated from the Stokes-Einstein based Dedye equation.

[340b] - Density Effects on the Reaction of Alcohols in Supercritical Water: Results from a New Apparatus

Jeffrey A. Manion (speaker) National Institute for Standards &Technology 100 Bureau Dr. Mail Stop 8381 Gaithersburg, MD 20899 Phone: 301-975-3188Fax: 301-975-3672 Email: jeffrey.manion@nist.gov

Vladimir Anikeev National Institute for Standards &Technology 100 Bureau Drive Mail Stop 8381 Gaithersburg, MD 20899 Phone: 301-975-4870

Abstract: The chemical reactions of organic compounds in supercritical water (SCW) are not well characterized, in part due to experimental difficulties. An innovative apparatus for the study of chemical kinetics in SCW will be described. The 125 ml continuously stirred static reactor allows processes to be studied under well-defined pressure, temperature and fluid density conditions. It features the direct injection of the substrate into a pre-existing SCW environment, which prevents sub-critical hot water chemistry from interfering with the results. Micro-scale samples are withdrawn on-line using an automated high-pressure valve and loop system. Sequential analyses allow the time progression of a reaction to be easily followed in a single experiment. Results on the reaction of alcohols and related compounds near 670 K and fluid densities of 0.2 to 0.6 g/ml will be presented. The density of the fluid is shown to have a large effect on the rate of reaction, suggesting that significant mechanistic changes occur over a relatively narrow band of fluid density. The implication is that this presents both significant opportunities and requirements for process control.

[340c] - Catalytic Oxidation in Supercritical Water

Jianli Yu (speaker) University of Michigan 3074 HHDow, 2300 Hayward St. Ann Arbor, MI 48109 Phone: 734-763-7806Fax: 734-763-0459 Email: jlyu@umich.edu

Phillip E. Savage University of Michigan Department of Chemical Engineering 3074 H. H. Dow Bld Ann Arbor, MI 48109-2136 Phone: 734-764-3386Fax: 734-763-0459 Email: psavage@umich.edu

Abstract: Catalytic oxidation in supercritical water is an emerging waste treatment technology. There is a need for reaction engineering information for this technology so that its technical and economic feasibility can be assessed. We have completed a comprehensive investigation into the kinetics and mechanisms of the catalytic oxidation of phenol, acetic acid, and phenol/acetic acid mixtures in supercritical water. CuO/Al2O3 and bulk MnO2 and TiO2 were used as catalysts. We have determined phenomenological and mechansim-based (Langmuir-Hinshelwood, Mars-van Krevelen) rate laws for the oxidation of each compound individually. We then used these rate laws to predict the conversions expected from oxidation of a phenol/acetic acid mixture in supercritical water. All three catalysts are active for oxidation in supercritical water, but they have different stabilities during long-term use and different effects on the selectivities to CO2 and to undesired byproducts. All three catalysts maintained their activities throughout a 100+ hour run. Both fresh and used catalysts were examined by X-ray diffraction, X-ray photoelectron spectroscopy, and BET surface area analysis to identify changes in composition and/or morphology that occurredduring oxidation in supercritical water.

[340d] - Catalytic Properties of Calcium Carbonate in SCF Waste Destruction and Transesterification

Galen Suppes (speaker) University of Kansas Department of Chemical andPetroleum Engineering 4006 Learned Hall Lawrence, KS 66045-2223 Phone: 785-864-3864Fax: 785-864-4967 Email: gsuppes@ukans.edu

Shaibal Roy University of Kansas 4006 Learned Lawrence, KS 66045

Phone: 785-864-4965Fax: 785-864-4967 Email: sroy@engr.ukans.edu

Jason Ruckman University of Kansas 4006 Learned Lawrence, KS 66045 Phone: 785-864-4965Fax: 785-864-4967 Email: jruckan@ukans.edu

Abstract: In one of its most prevalent natural forms, calcium carbonate in known as limestone. It is an abundant, inexpensive, and environmentally benign resource that is rarely used as a catalyst. Exploratory studies have shown limestone to be effective for both liquid and supercritical water oxidation as well as transesterification of triglycerides. This paper summarizes useful applications of these catalysts and likely mechanisms.

[340e] - Rhodium Catalyzed Homogeneous Hydroformylation of Higher Olefins in Supercritical Carbon Dioxide

Can Erkey University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: 860-486-4601Fax: 860-486-2959 Email: cerkey@engr.uconn.edu

Timothy D. Davis (speaker) University of Connecticut Department of Chemical Engineering Storrs, CT 06269 Phone: (860)486-5490Fax: (860) 486-2959 Email: tdd95001@uconnvm.uconn.edu

Abstract: Over 6 million tons of aldehydes per year are produced by homogeneous catalytic hydroformylation and used as feedstock for production of a wide variety of chemicals such as alcohols, diols, carboxylic acids, acroleins and acetals. This reaction involves the addition of carbon monoxide and hydrogen across a C-C double bond. The catalysts employed are of the form HxMy(CO)zLn; the two transition metals utilized are rhodium and cobalt and the most commonly utilized ligands are phosphines (PR3 where R = C6H5 or n-C4H9). Production of C4 aldehydes from hydroformylation of propene is dominated by rhodium based catalysts whereas higher aldehydes are produced mainly by cobalt catalysts. In hydroformylation of higher olefins, one of the major issues in switching to 1000 times more active Rh based catalysts is the difficulty of the separation of products and catalyst. Supercritical carbon dioxide (scCO2) can possibly be utilized as the solvent for hydroformylation of higher olefins where the catalyst can be separated from the reaction mixture and recycled by temperature/pressure tuning.

Since the solubilities of conventional catalysts are prohibitively low, a fluorinated analog of the catalyst, HRh(CO)(PPh3)3 was synthesized for hydroformylation of olefins in supercritical carbon dioxide (scCO2). The catalyst, HRh(CO)[P(3,5-(CF3)2C6H3)3]3, was found to be an extremely active catalyst in scCO2 for hydroformylation of 1-octene with maximum TOFs around 15,000 hr-1 at a relatively mild temperature of 65 oC. The very high activity results from the low basicity of the ligand. The kinetics of hydroformylation of 1-octene in scCO2 with the catalyst was investigated. The results were successfully interpreted using the generally accepted catalytic cycle in the literature based on a dissociative mechanism. The reaction is nearly first order with respect to H2 which suggests that oxidative addition of hydrogen to acyl intermediate is the rate determining step in scCO2 at the low phosphine concentrations employed. The commonly observed decrease in reaction rate with increasing phosphineconcentration with HRh(CO)(PPh3)3 in conventional solvents was not observed due to the low basicity of the ligand.

[340f] - Fixed-Bed Hydrogenation of Aromatics over Supported Transition-Metal Catalysts in Supercritical CO2-based Reaction Mixtures

Venu Arunajatesan (speaker) University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785 864 2921Fax: 785 864 4967 Email: venu@cpe.engr.ukans.edu

Bala Subramaniam University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785-864-2903Fax: 785-864-4967 Email: bsubramaniam@ukans.edu

Keith Hutchenson E.I. duPont de Nemours & Co Experimental Station P.O. Box 80304 Wilmington, DE 19880-0304 Phone: 302-695-1389

Fax: 302-695-3501 Email:keith.w.hutchenson@usa.dupont.com

Frank E. Herkes E.I. duPont de Nemours & Co Experimental Station Wilmington, DE 19880-0304 Phone: (302) 695-9084Fax: (302) 695-4353 Email:Frank.E.Herkes@usa.dupont.com

Abstract: Conversion and selectivity are presented for the hydrogenation of toluene over Al2O3-supported Rh and Ru catalysts in a continuous fixed-bed reactor at supercritical conditions using scCO2 as the solvent. The reaction was investigated in the temperature range of 60℃ to 120℃ with a hydrogen to toluene ratio of 1 to 3 while, the solvent concentration was chosen such that the reactants and products are in a homogeneous phase during reaction. The products from reaction are methylcyclohexane, methylcyclohexene and possibly methylcyclohexadiene with the preferred products being the partially hydrogenated toluene. The critical phase behavior of both the feed and the product mixtures was experimentally verified to ensure single-phase operation in the range of pressure and temperatures investigated. The single-phase nature of the supercritical fluids alleviates any external mass transfer resistances while maintaining gas-like diffusivities and liquid-like heat capacities. The effects of 'pressure-tuning' on the product selectivity and the temperature profile in the bed will be presented. The deleterious effects of impurities such as organic peroxides present in the feed at ppm-levels will be emphasized. The possible role of CO and/or formates formed from reverse WGS reaction and CO2 insertion respectively on the catalytic activity will be discussed. Complementary information on catalyst characteristics including surface area, pore-volume, and metal dispersion will be presented. Based on the foregoing results, rational process optimization strategies for safe and efficient operation of the exothermic hydrogenation reactions in supercritical reaction mixtures will be discussed.

[340g] - Sustainable Solid-Acid Isoparaffin Alkylation Using Supercritical FluidsDaniel M. Ginosar (speaker) Idaho Nat'l Engr. &Environmental Lab. P.O. Box 1625 Idaho Falls, ID 83415-2208 Phone: 208-526-9049Fax: 208-526-8541 Email: dmg@inel.gov

David N. Thompson Idaho Nat'l Engr. &Environmental Lab. PO Box 1626 Idaho Falls, ID 83415-2203 Phone: 208 526-3977

Kyle Coates Idaho Nat'l Engr. &Environmental Lab. PO Box 1625 Idaho Falls, ID 83415-2208 Phone: 208 526-6994

Abstract: Isoparaffin alkylation to couple high vapor pressure isoparaffins and olefins to yield a low vapor pressure, high octane gasoline blend stock is an essential requirement for producing environmentally sound ultra-clean fuels. Current industrial alkylation processes carry out the reaction in concentrated liquid hydrofluoric (HF) or sulfuric acid (H2SO4), both of which pose serious safety and environmental concerns due to the transport and storage of concentrated liquid acids and to disposal of acid-oil sludges. Over 1 million barrels a day of gasoline blend stock (13% of the gasoline pool) worth $10 billion are produced annually in the United States, giving significant economic impetus to the development of safer and more environmentally-friendly alkylation methods. While solid-acid catalysts have been studied as replacements for mineral acids, they deactivate rapidly due to the buildup of coke from sustained olefin additions at the catalyst surface and must be oxidatively regenerated. To minimize the deactivation, process conditions that result in low product concentrations and thus high separation costs are required. Increasing the catalyst life between oxidative regenerations would be a significant step toward shifting the economics in favor of solid-acid alkylation.

The Idaho National Engineering and Environmental Laboratory has been actively involved in the exploration of supercritical fluids for alkylation over solid-acid catalysts since 1994. To date, over a dozen different catalysts and eleven different supercritical fluids have been explored for the enhancement of the butene/ butane reaction. Current results demonstrate that a solid-acid alkylation catalyst can maintain 100% of its initial activity for at least one week of operation using supercritical fluids. At an olefin weight hour space velocity (OWHSV) of 0.2 hr-1 and an isoparaffin to olefin ratio of 20:1, sustainable butene conversions greater than 95% and alkylate yields greater than 1.8 gram alkylate per gram butene fed were observed. In the product streams, trimethylpentanes represented the majority of the alkylate product. The effect of solvent choice, process conditions and reactor design will be discussed.

[340h] - Supercritical Catalysis for the Alkylation and Dimerization of Butenes

William J. Thomson (speaker) Washington State University spokane street Pullman, WA 99164-2710 Phone: (509) 335-8580

Fax: (509) 335-4806 Email: thomson@che.wsu.edu

Anand S. Chellappa Washington State University spokane st. Pullman, WA 99164-2710 Phone: (509) 335-4332

Abstract: The alkylation of butenes with isobutane as well as the dimerization of butenes has been studied, using unpromoted and promoted sulfated zirconia catalysts under supercritical conditions. Conversion and selectivity data were obtained as a function of time at temperatures between 60 C and 155 C and with isobutane/butene (I/O) ratios between eight and zero. With 2-butene as the olefin source, C8 alkylate selectivities ranged from 1% at 80C, to 20% at 145 C. With 1-butene as the source, trimethylpentane selectivities were as high as 14% during the early stages of a run at 80C. At the higher temperatures, selectivities to C8 olefins were high, increasing from 57% to 93% as I/O was lowered from 8 to 0. The C8 olefins consist primarily of dimethyl hexenes (> 90%) and, when water was added to the feed charge at I/O = 8, the dimethyl hexenes selectivity was 99%. The results of catalyst regeneration experiments are also presented and will be discussed along with the mechanistic implications of these results.

[354] - Reactions in Benign SolventsChair:Phillip E. SavageUniversity of MichiganDepartment of Chemical Engineering3074 H. H. Dow BldAnn Arbor, MI 48109-2136Telephone Number: 734-764-3386Fax Number: 734-763-0459Email: psavage@umich.edu

Vice Chair:Joan F. BrenneckeUniversity of Notre Dame182 Fitzpatrick HallNotre Dame, IN 46556Telephone Number: 219-631-5847Fax Number: 219-631-8366Email: jfb@nd.edu

[354c] - Acid Catalysis in High-Temperature Water: Kinetics and Mechanisms of Cyclohexanol Dehydration

Presented at: [354] - Reactions in Benign Solvents

Naoko Akiya (speaker) University of Michigan 2300 Hayward, 3074 H. H. Dow Ann Arbor, MI 48109-2136 Phone: (734) 615-3390Fax: (734) 763-0459 Email: nakiya@engin.umich.edu

Phillip E. Savage University of Michigan Department of ChemicalEngineering 3074 H. H. Dow Bld Ann Arbor, MI 48109-2136 Phone: 734-764-3386Fax: 734-763-0459 Email: psavage@umich.edu

Abstract: Water near its critical point (374 C, 218 atm) is an environmentally benign medium for chemical synthesis. The dissociation constant of near-critical water is several orders of magnitude higher than that of ambient liquid water. This natural abundance of H3O+ ions in water can be exploited to facilitate acid-catalyzed reactions in the absence of harsh mineral acids. We studied the reaction kinetics of cyclohexanol dehydration in water. Cyclohexanol chemistry is a model system for chemical synthesis in high-temperature water, since cyclohexanol undergoes a variety of transformations depending on the reaction conditions. Experiments were carried out at 250, 275, 300, 350, and 380 C in batch microreactors immersed in a temperature-controlled fluidized sandbath. At 380 C, a single supercritical fluid phase was present in the reactor at reaction conditions, and the water density was changed from 0.08 to 0.68 g/cc by adjusting the water loading. At subcritical temperatures (250-350 C), a sufficient amount of water was added to the reactor to maintain a single liquid phase (0.81-0.35 g/cc) at reaction conditions. Reaction times ranged from 15 to 180 minutes. Under these conditions, cyclohexanol readily undergoes dehydration. The main product is cyclohexene. At temperatures above 300 C, 1-methyl cyclopentene and 3-methyl cyclopentene are also observed. The experimental data indicate that the reaction rate depends on water density. Cyclohexanol conversion increases with increasing water density. When methyl cyclopentenes are formed, their yields increase with increasing water density while thecyclohexene yield decreases. A reaction network comprising two parallel reversible reactions of cyclohexanol, one forming cyclohexene and other forming methyl cyclopentenes, successfully modeled the constant-density data. This model, however, was unable to reproduce the water density dependence of conversion and yields that was observed, suggesting that a model that explicitly treats the participation of H3O+ ions might be necessary to account for all the data. To gain mechanistic

understanding of cyclohexanol dehydration in water, we fit the experimental data to mechanism-based kinetics models constructed from different combinations of plausible mechanisms, including E2 and E1 mechanisms for alcohol dehydration and different routes to dicyclohexyl ether chemistry. We discriminated between the rival mechanisms based on the goodness of fit.

[354d] - Solvent Effects on Chemical Reactions in Nearcritical Water

Jie Lu (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-2876 Fax: (404)894-9085 Email: jie.lu@che.gatech.edu

James S. Brown Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404) 894-6766Fax: (404) 894-3690 Email: james.brown@che.gatech.edu

David Bush Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6885

Charles L. Liotta Georgia Institute of Technology Ga Tech Office of the President,Carnegie Building Atlanta, GA 30332-0325 Phone: 404-894-8884charles.liotta@carnegie.gatech.edu

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu

Abstract: Water is the most widely available and environmentally benign medium to replace hazardous organic solvents. Nearcritical water (NCW) can dissolve both organics and ionics due to the significantly decreased dielectric constant at higher temperatures. Also NCW has an elevated ionization constant and may act as an acid or base catalyst in chemical reactions. A more complete fundamental understanding of the properties and behavior of NCW would enhance our ability to correlate, predict and design processes for potential applications.

In the work, the temperature-dependent thermodynamics and kinetics of some model reactions were investigated in NCW and compared to those in some conventional solvents. The Kamlet-Taft linear solvation energy relationship (LSER) was applied to correlate the experimental data based on the pi* (dipolarity/polarizability), alpha (hydrogen-bonding donor) and beta (hydrogen-bonding acceptor) parameters for NCW measured in our laboratory. These Kamlet-Taft solvatochromism parameters provide us a powerful tool to describe and predict chemical reactions and phase behavior in this novel medium.

[354e] - Investigation of Catalytic Surface Mechanism during Hydroformylation in scCO2

Andrew R. Tadd (speaker) University of Toledo 3048 Nitschke Hall Toledo, OH 43606 Phone: 419-530-8107Fax: 419-530-8080 Email: atadd@eng.utoledo.edu

Greg A. Snyder University of Toledo 3048 Nitschke Hall Toledo, OH 43606 Phone: 419-530-8107Fax: 419-530-8080 Email: gsnyder@eng.utoledo.edu

Martin A. Abraham University of Toledo Chemical and EnviornmentalEngineering Department Mail Stop 305, 2801 West Bancroft Street Toledo, OH 43606-3390 Phone: 419-530-8092

Fax: 419-530-8086 Email: mabraham@eng.utoledo.edu

Abstract: Factors influencing the heterogeneous hydroformylation of propylene in scCO2 have previously been studied using a Rh on SiO2 catalyst in a batch reactor at 100 C. Sensitivity to reaction conditions, catalyst preparation, and catalyst support was evaluated. As an extension of this work, the hydroformylation reaction was studied using diffuse reflectance infrared spectroscopy and mass spectrometry. The effect of reactant feed composition, reaction pressure, catalyst preparation, and catalyst support on the adsorbed species and the hydroformylation reaction was studied. The catalyst was studied under both flow and batch operation.

[354f] - CO2-Alcohol Systems for Novel in situ Acid Generation

Christy W. Culp (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6766Fax: (404)894-9085 Email: christy.culp@che.gatech.edu

Kevin N. West Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: 404-894-6766kevin.west@che.gatech.edu

Jonathan P. McCarney Georgia Institute of Technology School of Chemistry and Biochemistry Atlanta, GA 30332-0400 Phone: (404)894-4074Email: gt7153d@prism.gatech.edu

Kristen N. Griffith Griffith Boggs Atlanta, GA 30332-0400 Phone: 404-894-4074gt7267c@prism.gatech.edu

Charles L. Liotta Georgia Institute of Technology Ga Tech Office of the President,Carnegie Building Atlanta, GA 30332-0325 Phone: 404-894-8884charles.liotta@carnegie.gatech.edu

David Bush Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6885

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu

Abstract: The mutual solubility of carbon dioxide and alcohols over a wide range of temperature and pressure provides a useful and tunable medium for reactions and separations. For many years, researchers have used alcohols as cosolvents in supercritical CO2, and recently CO2-swollen alcohols have been used for anti-solvent crystallization and as mobile phases for chromatography. However, little consideration has been given to chemical interaction between the alcohols and CO2. We have confirmed that such an interaction does exist and can create an acidic environment.

By isolating reaction products we have demonstrated that alcohol-CO2 complexes react similarly to carboxylic acids with diazodiphenylmethane, a compound typically used to evaluate acid strengths. We have also characterized the relative acidities of several alcohol-CO2 mixtures over a range of composition. Our evidence indicates that the behavior of CO2-alcohol systems is comparable to that of CO2-water systems, where carbonic acid is formed. This phenomenon should not only be considered when utilizing these solvent systems, but it may also provide opportunities for environmentally benign in situ acid catalysis.

[354g] - 1-Butene/Isobutane Alkylation over unsupported and SiO2-supported Nafion in Liquid and Supercritical Reaction Phases

Carmo Pereira

E.I. duPont de Nemours & Co 1007 Market St. N65278 Wilmington, DE 19898 Phone: 302-774-2337Fax: 302-774-2457 Email: Carmo.J.Pereira@USA.dupont.com

Bala Subramaniam University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785-864-2903Fax: 785-864-4967 Email: bsubramaniam@ukans.edu

Christopher J. Lyon (speaker) University of Kansas 4006 Learned Hall Lawrence, KS 66045 Phone: 785.864.2921Fax: 785.864.4967 Email: pinniped@ukans.edu

Abstract: Virtually steady isobutane/1-butene alkylation activity has been demonstrated on Nafion perfluorinated ion-exchange resin and on silica-supported Nafion, both in the liquid phase (368 K, 400 psi) and in a supercritical reaction mixture (368 K, 2000 psi). (Isobutane/1-butene= 10, butene space velocity= 0.05 h-1). Carrying out the reaction in the near-critical region at 368 K (facilitated by carbon dioxide) offers the advantage of improved C8 paraffin selectivity. By "pressure tuning" the reaction mixture properties in the near-critical region, the alkylate yield can be optimized. This optimization involves a trade-off between product solubility and intraparticle diffusion, thereby maximizing the rate of pore cleaning. High-pressure in-situ FT-IR reaction studies provide complementary information about the nature of the acid sites and adsorbed species under reaction conditions.

[354h] - Activity of Perfluoropolyether-Modified NAD(H) in Fluorous Solvents and Carbon Dioxide

Janice L. Panza (speaker) University of Pittsburgh 573 East End Avenue Pittsburgh, PA 15221 Phone: 412-731-7023Fax: 412-383-9710 Email: panzajl@msx.upmc.edu

Alan J. Russell University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-9631

Eric J. Beckman University of Pittsburgh 1249 Benedum Hall Pittsburgh, PA 15261 Phone: 412-624-9631

Abstract: Fluorous solvents as reaction media are of growing interest in that they are considered environmentally benign mainly since they are easy to separate from both aqueous and organic solvents due to their immiscibility in both. An emerging field exploiting the benefits of fluorous solvents is fluorous biphasic systems (FBS). FBS consist of a fluorous phase containing a dissolved catalyst and a second phase, either organic or non-organic having limited or no solubility in the fluorous phase. The catalyst is only soluble in the fluorous phase with the product preferring the non-fluorous phase. FBS lead to easy product separation and recovery and recycle of catalyst.

Most exploration using FBS has been in the expansion of fluorous-soluble catalysts, by attaching fluorinated tails to traditional catalysts thereby rendering them soluble in fluorous solvents. FBS have been shown to have utility in many types of reactions that require catalysts; however, there is an exciting area that has not been investigated using FBS, and that is biocatalysis.

Enzyme-catalyzed reactions appear to be the ideal for use in FBS, especially enzyme-catalyzed oxidation/reduction reactions that require the cofactor nicatinamide adenine dinucleotide (NAD). NAD accepts a hydride ion from the substrate reducing it to NADH with the concurrent oxidation of the substrate to product. The major problem with using enzymes in oxidation/reduction reactionsis the high cost of both the enzyme and the cofactor, specifically the cofactor since it is needed in stoichiometric amounts. In order to make these reactions more economically feasible, reuse of NAD must be possible. This is where FBS become useful. We have developed a NAD derivative with an attached fluorinated tail, called F-NAD(H), that is soluble in fluorous solvents. The F-NAD(H) is ideal for use in FBS since it can participate in a reaction, yet be retained in the fluorous phase for regeneration and recycling.

The design and synthesis of F-NAD(H) been previously discussed. Interestingly, the F-NAD(H) designed to be soluble in fluorous solvents has also demonstrated solubility in CO2. In this presentation, we will demonstrate that F-NAD(H) retains its activity in a fluorous solvent. In addition, we will investigate the activity of F-NAD(H) in CO2. Finally, we will discuss the viability of developing biocatalysis in "green" solvents such as fluorous solvents and CO2.

[354i] - Catalysis with Environmentally Benign Solvents at Elevated Temperature and Pressure

Kristen N. Griffith Griffith Boggs Atlanta, GA 30332-0400 Phone: 404-894-4074Email: gt7267c@prism.gatech.edu

James S. Brown (speaker) Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404) 894-6766Fax: (404) 894-3690 Email: james.brown@che.gatech.edu

Jason P. Hallett Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404)894-6766Fax: (404)894-9085 Email: jason.hallett@che.gatech.edu

Roger Glaser Georgia Institute of Technology 778 Atlantic Drive Atlanta, GA 30332-0100 Phone: (404) 894 - 6766

Charles L. Liotta Georgia Institute of Technology Ga Tech Office of the President,Carnegie Building Atlanta, GA 30332-0325 Phone: 404-894-8884Email: charles.liotta@carnegie.gatech.edu

Charles A. Eckert Georgia Institute of Tecnology 778 Atlantic Dr. Atlanta, GA 30332-0100 Phone: 404-894-7070Fax: 404-894-9085 Email: cae@che.gatech.edu

Abstract: Traditional Friedel-Crafts acylation reactions generally require stoichiometric quantities of strong mineral acids such as sulfuric, polyphosphonic, anhydrous hydrofluoric, or nonregenerable Lewis acids such as AlCl3. These catalysts function by forming strong, exothermic complexes with the carbonyl oxygen of the acylating agent. The thermodynamically stable metal-carbonyl complex remains intact even after reaction has taken place. To break the complex and recover the products, these acids require neutralization to salts and disposal, and disposal costs can be considerable. This results in the landfilling of severalpounds of waste salt byproduct for every pound of product produced.

Along with the disposal of large quantities of metal salts, these traditional acylations are generally run in organic solvents that can dissolve the organic reactants, the aluminum chloride catalyst, and the resulting acyl chloride-aluminum chloride complex. Phenolic compounds cannot be acylated in non-polar solvents so the acylation of these compounds is performed in chlorinated or nitrated organic solvents such as chlorobenzene, o-dichlorobenzene, tetrachloroethane, nitrobenzene, and nitroethane.

In order to avoid these hazardous organic solvents and huge quantities of unwanted waste, we performed some of these same reactions in more environmentally benign solvents such as aqueous and neat acetic acid at elevated temperature (250-300C) without producing any salt byproduct. To demonstrate this new environmentally friendly technology, phenol and resorcinol were acetylated to the corresponding esters and ketones in high yield with neat acetic acid without any added acid catalyst. Avoiding these acid catalysts eliminates the high cost and environmental impact of acid neutralization and disposal.