1-s2.0-s092058611400234x-main

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ARTICLE IN PRESSG ModelCATTOD-8953; No. of Pages 10Catalysis Today xxx (2014) xxxxxx

Contents lists available at ScienceDirect

Catalysis Today

j our na l ho me page: www.elsev ier .com/ locate /ca t tod

PVA co nthin a pe

T.F. Ceiaa roa

a REQUIMTE/CQ Nova db Departament UniverPortugal

a r t i c l

Article history:Received 5 AuReceived in reAccepted 14 FAvailable onlin

Keywords:BioreneryHyacinth avoAcetalizationPolymeric catalytic membrane reactorPVA membranePervaporation

stingric mae and

alyst the pisted es solts al

watThe catalytic membranes were characterized by measurement of thickness, water contact angles and

swelling degree as well as by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy(AFM) and scanning electron microscopy (SEM).

2014 Elsevier B.V. All rights reserved.

1. Introdu

The usebeen growisynthesis anout hazard approved oduced avoby the Foodfragrances, and cosmetphenylaceta

Glycerolby transestrently, as tsustainablehas been ilarger thanuses for gly

Corresponfax: +351 21 2

E-mail add

http://dx.doi.o0920-5861/ this article in press as: T.F. Ceia, et al., PVA composite catalytic membranes for hyacinth avour synthesis in a pervaporatione reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.02.052

ction

of aromatic chemicals as avouring compounds hasng since the chemical developments that allowed theird commercial production. To be able to be used with-to public health these fragrances must be included infcial lists of naturally occurring or synthetically pro-uring substances (e.g.: the FEMA-GRAS list regulated

and Drug Administration) [1]. Among the approvedhyacinth avour, a high value product used in foodic industry, is generally synthetized by acetalization ofldehyde with glycerol (Scheme 1) under acid catalysis.

is a by-product of the biodiesel manufacturing processerication of vegetable oils or animal fats [2]. Cur-he global research is focused on the development of

and renewable resources, the production of biodieselncreasing signicantly leading to glycerol amounts

the market can absorb. In order to develop newcerol different catalytic processes, including oxidation,

ding author. Tel.: +351 21 2948385;948350/+351 21 2948550.ress: [email protected] (J. Vital).

reforming, hydrogenolysis, etherication, esterication and acetal-ization reactions, have been reported in the transformation ofglycerol [36]. In the particular case of the reaction in study, themajor environmental and economic gains of the phenylacetalde-hyde acetalization reaction are the glycerol effective reuse in thebioreneries and the conversion of glycerol to a value added chem-ical [3].

In general acetals are prepared through a reversible reactionbetween an alcohol and an aldehyde with water as a by-product.The thermodynamic limitations in conventional reaction systemsresult in low conversions for these reactions [7,8]. In order todisplace equilibrium and improve reaction conversion, reactiveazeotropic distillation has been proposed for removal the waterformed in the acetalization reaction [1]. However this techniquerequires large amounts of toxic solvents, oversized equipment andconsequently leads to high energetic costs.

The use of catalytically active membranes and in particularlythe use of polymeric catalytic membrane reactors (PCMRs), canoffer specic advantages by combining in a single unit operationchemical reaction and separation [911]. Moreover, the continuousremoval of water from the reaction mixture by means of perva-poration coupling shifts the reaction to the product side and thusincreases the yield [1215]. Other benecial aspects associated toPCMRs include the low energy consumption and the possibility of

rg/10.1016/j.cattod.2014.02.0522014 Elsevier B.V. All rights reserved.mposite catalytic membranes for hyacirvaporation membrane reactor

, A.G. Silvaa, C.S. Ribeiroa, J.V. Pintob, M.H. CasimiFB, Departamento de Qumica, Faculdade de Cincias e Tecnologia, FCT, Universidade

o de Cincia dos Materiais and CENIMAT/I3N, Faculdade de Cincias e Tecnologia, FCT,

e i n f o

gust 2013vised form 12 February 2014ebruary 2014e xxx

ur

a b s t r a c t

Composite catalytic membranes consiUSY zeolite dispersed into the polymeby acetalization of phenylacetaldehyd

In order to study the effects of catbalance in the catalytic behaviour of conditions and in a pervaparation asslinking strongly affects the membranthe increase of catalyst loading. Resuaccomplished with good selectivity to avour synthesis

, A.M. Ramosa, J. Vitala,

e Lisboa, 2829-516 Caparica, Portugalsidade Nova de Lisboa, 2829-516 Caparica,

of poly(vinyl alcohol) cross-linked with glutaraldehyde and H-trix were prepared and used in the hyacinth avour synthesis

glycerol.loading, polymer cross-linking and hydrophilic/hydrophobicrepared membranes, catalytic runs were performed in batchcatalytic membrane reactor. It was found that polymer cross-rption and transport properties which seem to improve withso evidence that permeation in membrane reactor was weller.

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ARTICLE IN PRESSG ModelCATTOD-8953; No. of Pages 102 T.F. Ceia et al. / Catalysis Today xxx (2014) xxxxxx

Scheme 1. Acetalization of phenylacetaldehyde with glycerol. (1) 2-Benzyl-4-hydroxy methyl-1,3-dioxan. (2) 2-Benzyl-5-hydroxy-1,3-dioxane.

carrying out the reaction without the use of solvents and thus ren-der the process environmentally and technically more attractive.

Although high conversions can be achieved in the acetaliza-tion of glycerol and phenylacetaldehyde when very pure reactantsare used, the use of cheap low grade glycerol with relatively highwater content, is desirable. However, under these conditions equi-librium conversion decreases signicantly becoming mandatorythe removal of water simultaneously with the chemical reaction.In the present work, catalytic composite membranes consist-ing in poly(vinyl alcohol) (PVA) cross-linked with glutaraldehyde(Scheme 2) and zeolite HUSY dispersed into the polymeric matrix,were prepaCatalytic ruation assistloading, poance in theevaluated, alytic memdistillation.

2. Experim

2.1. Prepara

PVA (Aldduring 2 h. loadings anH-USY zeolisuspended and then m(GA) (Aldric

Scheme 2. PV

The solutions were poured in a Petri dish and allowed to concen-trate and cross-link at 40 C for 135 min after what phase inversionwas obtained by adding methanol to the Petri dish. Finally themembranes were removed from the Petri dish and allowed to dryovernight a

PVA acedride (>99%during 24 hfor 4 h. Thecedure prevYuGvAcw mloaded withand w% acethe PVA aquing to v/4%assuming thOH groupstreated witof the total

2.2. Membr

The cataof thicknes

rier copymbra

micreas

bsorps of, glychen mm th

spe in a es s

surcopy

Scani S-2

talyt

synt andhe palyticeactter d4 mLraneAldrntern

expred and used in the acetalization of phenylacetaldehyde.ns were performed in batch conditions and in pervapor-ed catalytic membrane reactor. The effects of catalystlymer cross-linking and hydrophilic/hydrophobic bal-

catalytic behaviour of the prepared membranes wereas well as the application of a pervaporation cat-brane reactor as an alternative method to azeotropic

ental

tion of catalytic composite membranes

rich, 99% hydrolyzed) was dissolved in water at 80 C,In order to obtain membranes with different catalystd different cross-linkings, the appropriated amounts ofte (Zeolyst, CBV 720, average particle size: 0.8 m) werein 20 mL of aqueous 8 wt% PVA solution, sonicated for 1 hixed with the appropriated amount of glutaraldehydeh, aqueous solution, 50 wt%).

by Foumicros

Mementswere mvent asample(waterture. Tout fro

FTIRpellets(40 tim

Themicrosmode.Hitach

2.3. Ca

Theditionsusing t

Catbatch rdiamewith 1membSigma-as GC i

The this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

A cross-linked with glutaraldehyde and partially acetylated.

110 C, 120lyst, and thetaken at reg

Catalyticpervaporatposed of twdescribed iin such a wglass in thechamber.anes for hyacinth avour synthesis in a pervaporation2.052

t room temperature.tylation was carried out by reaction with acetic anhy-, Riedel-de Han) at 110 C and atmospheric pressure, followed by acetone extraction and drying at 80 C

partly acetylated PVA was then subjected to the pro-iously described for membrane preparation. The codeeans a PVA matrix v% cross-linked with glutaraldehyde,

u% of H-USY zeolite (weight of H-USY/weight of PVA)tylated. The v% cross-linking means that was added toeous solution an amount of glutaraldehyde correspond-

of the total number of moles of the PVA OH groups,at each mole of glutaraldehyde acetalizes 4 mol of PVA

. The w% acetylation means that the parent PVA wash an amount of acetic anhydride corresponding to w%

number of moles of the PVA OH groups.

anes characterization

lytic membranes were characterized by measurements, water contact angle and swelling degree as well astransform infrared spectroscopy (FTIR), atomic force

(AFM) and scanning electron microscopy (SEM).nes thickness was measured using a Braive Instru-ometer (0.001 mm accuracy) and water contact anglesured using a CAM 100 series 110057 goniometer. Sol-tion experiments were carried out by immersing dry

the obtained membranes in the appropriate reagenterol or phenylacetaldehyde) for 24 h at room tempera-embranes were removed, the excess of reagent wiped

e its surface and weighted.ctra were obtained in transmission mode by using KBrPerkin-Elmer FT-IR Spectrum 1000 spectrophotometercanning; 4 cm1 of resolution).face morphology was investigated by atomic force

(AFM) using an Asylum MFP-3D Microscope in ACning electron microscopy (SEM) was performed on a400 equipment.

ic experiments

hesis of hyacinth avour was performed in batch con- in a pervaporation assisted catalytic membrane reactorrepared composite catalytic membranes.

tests in batch conditions were carried out in a jacketedor at 100 C using the catalytic membranes cut in 0.6 cmisks. In a typical experiment the reactor was loaded

of glycerol (99%, Sigma-Aldrich), a known amount ofs mass (0.50.8 g), 12 mL of phenylacetaldehyde (>95%,ich) and 1 mL of undecane (analytical standard, Fluka)al standard for gas chromatography (GC).eriments with free H-USY were performed at 100 C,C and 140 C with the reactor loaded with 0.1 g of cata-

same amounts of the other components. Samples wereular time periods and analyzed by GC.

runs in membrane reactor operating under sweep gasion conditions were performed using a reactor com-o metal slabs, each having an inlet and an outlet, as

n a previous work [20]. The membrane was assembleday that the catalytic layer side (i.e. the side facing the

Petri dish, during preparation) was facing the reactants

Please cite mbranes for hyacinth avour synthesis in a pervaporationmembran 014.02.052

ARTICLE IN PRESSG ModelCATTOD-8953; No. of Pages 10T.F. Ceia et al. / Catalysis Today xxx (2014) xxxxxx 3

The reactor was heated at 70 C and the reaction mixture (45 mLof glycerol, 19.5 mL of phenylacetaldehyde and 12.7 mL of unde-cane) was pumped at 12.4 mL/min. Dry nitrogen gas (ow rateof 170 mL/min), was used to sweep the downstream side of themembrane meated wat1 mL of n-prof the perm

3. Results

3.1. Charac

The expePVA compducible. Al(batch and thickness a0.25 0.02

3.1.1. SolveThe mem

(Qr) was cal

Q (%) = m m

where m ismass.

Membrain glycerol hydrophilicwater molethe PVA ma

Swellingthe increasof the matever, swelliincreases frexplanationers, restrictlimits.

The cathydrophilicnot observeincreases.

The incrincrease inwith the resmembrane contact angThe effects oin glycerol o

In agreethe increasthe increasswelling intact angle oincreases.

3.1.2. FTIR sThe chan

FTIR spectrmembranesthe major ping broad bband aroun

TIR spehyd

1417t 115. Thd toinyl

incnal cydroi-ac

matiitionsemianceony

takeed, thss-lied inddedups ultan

is oban increasingly incomplete cross-linking reaction when thet of added cross-linker increases.cerning acetylation results, it was found an increase of theH ratio with the increase of the amount of added acetic anhy-Fig. 2B), which suggests the increase of PVA acetylation.

Membrane morphologymbranes morphology was examined by SEM and AFM. Theages representative for the morphology of the PVA com-

catalytic membranes surface are depicted in Fig. 3. It canrly identied (Fig. 3B) an asymmetric membrane with twot layers: a selective layer made of a dense PVA layer, and aic one composed of catalyst discrete particles dispersed onttom of the membranes cross section.

analysis (Fig. 4) reveals a possible correlation between thee roughness (Ra) and membranes hydrophobicity. A possi-rpretation is that the increase of membranes hydrophilicity

cross-linking and acetylation degrees) can lead to highercontent in the polymeric matrix, which leads to membranesed plasticity thus reducing its surface roughness. In fact, this article in press as: T.F. Ceia, et al., PVA composite catalytic mee reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2

into 70 mL of acetic anhydride. In order to quantify per-er, samples from this solution were prepared by addingopanol and 0.1 mL of n-nonane (GC standard) to 0.1 mLeated solution and analyzed by GC.

and discussion

terization of the catalytic membranes

rimental methodology developed allowed to obtainedosite catalytic membranes morphologically repro-l the membranes used in the both catalytic testsmembrane reactor) had similar appearance presentingnd weight values (average and standard deviation) ofmm and 1.67 0.05 g, respectively.

nt absorption and water contact anglebranes swelling (taken as solvent absorption) degreeculated using the expression:

m0

0 100 (1)

the mass of the swollen sample and m0 is the initial

nes swelling reaches much higher values in water thanor phenylacetaldehyde (Table 1) not only due to the

character of PVA but also due to the small size of thecules, which can easily diffuse into the free volumes oftrix.

with glycerol or phenyl acetaldehyde increases withe of the catalyst loading, probably due to the increaserix free volume and due to voids formation. How-ng with water only increases when the catalyst loadingom 5% to 10%, decreasing for higher loadings. A possible

is the possibility of the catalyst particles act as spac-ing the movement of the polymer chains beyond certain

alyst loading appears to have no effect on theity of the membranes since signicant changes ared in the water contact angle when the catalyst load

ease of polymer cross-linking appears to lead to an the hydrophobicity of the membranes, in agreementults reported by other authors [16], not only because theswelling in water decreases but also because the waterle increases when the polymer cross-linking increases.f the polymer cross-linking on the membranes swellingr phenylacetaldehyde are not conclusive.ment with observations previously reported [17]e in membrane acetylation appears also to lead toe of membrane hydrophobicity since the membrane

water decreases and simultaneously the water con-f the membranes increases when membrane acetylation

pectroscopyges in the PVA chemical structure were evaluated by

oscopy. Fig. 1 shows the FTIR spectra obtained for PVA with different cross-linking degrees. All spectra exhibiteaks related to the typical PVA pattern (a OH stretch-and around 35503200 cm1, a CH stretch vibrationd 30002840 cm1 and a CH2 deformation band at

4000

Tran

smita

nce

(a.u.)

Fig. 1. Fglutarald

1461peak aand GAassigne(poly(vor fromfunctiowith hor hemconfor

Addtion a absorbor carbgroup,expectinal croobservof GA aOH gro

Simratio itcating amoun

ConC=O/Odride (

3.1.3. Me

SEM imposite be cleadistinccatalytthe bo

AFMaveragble inte(lowerwater increas500100015002000250030003500Wavenumbe r (c m-1)

G4

G6

G8

G10

ectra of membranes Y10G04, Y10G06, Y10G08 and Y10G10. Effect ofe addition.

cm1 [18]), together with the acetal bridge COC01085 cm1 resulting from the reaction between PVAe presence of a small band at 17501735 cm1 can be

the C=O stretching from the acetate remaining from PVA alcohol) is obtained by hydrolysis of poly(vinyl acetate))omplete cross-linking reaction with GA since as a bi-ross-linker, one of the GA aldehyde groups may reactxyl groups of a PVA polymer chain by forming a acetaletal, while the other one might not react due to someon limitations [18].ally, to conrm the effectiveness of cross-linking reac-qualitative analysis was performed by comparing the

ratios between the bands assigned to acetal (COC)l (C=O) groups and the characteristic band of the OHn at the maximum absorbance wavenumber (Fig. 2A). Ase absorbance ratio COC/OH increases when the nom-nking increases. These results are in agreement with thecrease of membrane hydrophobicity with the amount

(Table 1) suggesting a decrease of the amount of PVAand, therefore, an increase of cross-linking.eously with the increase of the COC/OH absorbanceserved an increase of the C=O/OH absorbance ratio indi-

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Fig. 2. Absorbbonyl groups cross-linkings(C=O/OH).

there have of good poltaneously, roughness vto be due to

3.2. Catalyt

3.2.1. BatchIn order

cross-linkinmance of th

Fig. 3. SEM micrographs of Y10G02: (A) surface of the selective layer side; (B) crosssection.

of phenylacetaldehyde and glycerol were performed in batchconditions.

As an example, Fig. 5 shows the conversion proles obtainedwith the membranes prepared with different cross-linking degrees,for a same catalyst loading (Y10G04, Y10G06, Y10G08 and Y10G10).

A common feature to all concentration proles is an initialion period, which seems to increase when cross-linkinges. S

justias a clymeetweg.

6 shoctionc) asre glnditision

Table 1Membrane ch

Membrane

Y05G02 Y10G02 Y15G02 Y20G02 Y10G04 Y10G06 Y10G08 Y10G10 Y10G02Ac10Y10G02Ac20Y10G02Ac30

Thickness, waance ratio between the bands assigned to acetal (COC) or car-

inductincreascan bebrane the polated bbondin

Fig.the reagraphi87% pution coconver this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

(C=O) and OH groups: (A) PVA membranes with different polymer (COC/OH); (B) PVA membranes with different acetylation degrees

been reports of other authors on the effects of tracesymer solvents, leading to atter surfaces [19]. Simul-higher amounts of H-USY zeolite lead also to loweralues. Using the same interpretation, this effect is likely

the zeolites hydrophilic character.

ic tests

experiments to evaluate the effect of the catalyst loading, polymerg and the PVA acetylation on the catalytic perfor-e composite membranes, catalytic runs of acetalization

The ttiport acrossphenylacetquite well t

3.3. Membr

3.3.1. BasicFor mod

homogeneolished was used in pre[2327]:

- Isotherma- Pseudo-st

membran

aracterization.

Thickness (mm) Swelling (%)

Water Glycerol

0.237 255 23 0.238 280 45 0.238 229 55 0.262 211 83 0.246 268 15 0.263 218 15 0.247 43 0.254 215 31

0.284 278 115 0.250 232 91 0.249 228 104

ter contact angle and swelling in water, glycerol and phenylacetaldehyde.uch behaviour suggests an autocatalytic effect whiched by the improved transport properties of the mem-onsequence of the interaction of acetal molecules withr chains. In fact the acetal molecules can be interca-en the PVA chains, decreasing the interchain hydrogen

ws the conversion proles obtained with free H-USY for carried out at 100 C and using 99% pure glycerol (main

well as for the reaction carried out at 70 C and usingycerol (insertion). It is quite clear that in the last reac-ons, when the lower grade glycerol is used, equilibrium

remains below 90%.ng of a diffusion-kinetic model assuming ckian trans-

the membrane and dependence of the diffusivity ofaldehyde on the concentration of the formed acetal tshe kinetic data (solid lines) supporting that hypothesis.

ane modelling

assumptionselling purposes the membranes were assumed as dense,us and symmetrical. The kinetic-diffusion model estab-based on the following assumptions similar to thosevious works [17,2022] and works of other authors

l and isobaric reaction conditions.eady state conditions for diffusion and reaction in thee.

Contact angle ()

Phenylacetaldehyde

11 55.94anes for hyacinth avour synthesis in a pervaporation2.052

23 54.0529 66.6931 55.9625 18 52.0015 56.0918 57.2520 56.3616 59.8620 61.60

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- Unidirect- Fickian tr- Linear sor

and the m

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

Frac

tiona

l con

vers

ion

Fig. 5. Acetalicomposite meing cross-linki this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

Fig. 4. 3D AFM images of PVA membranes with different: (A) catalyst loading (H-USY ze

ional diffusion.ansport across the membrane.ption equilibrium isotherm between the liquid phaseembrane.

20 40 60 80 100Time (h)

Y10G04

Y10G06

Y10G08

Y10G10

zation of phenylacetaldehyde and glycerol catalyzed by PVA/H-USYmbranes. Conversion proles obtained for membranes with increas-ng degrees.

- Zero tranto the me

- Diffusivitphenylacethe mode

- Diffusivitthe acetaaccording

De = De0e

(

where De0 iare factors tenhancing induction p

3.3.2. Rate In order

were perfoent kinetic tested, namHinshelwooadsorption uct desorprate limitinanes for hyacinth avour synthesis in a pervaporation2.052

olite); (B) crosslinking degree; (C) acetylation degree.

sport resistance for both reactants from the bulk phasembrane surface.y of glycerol is assumed to be high compared to that oftaldehyde and set to a value high enough to becomel insensitive to the parameter.y of phenylacetaldehyde is assumed to depend onl concentration in the homogeneous liquid phase, ClC ,

to the equation:

ClC

ClC

+

)(2)

s the phenylacetaldehyde initial diffusivity; , and hat inuence diffusivity behaviour: is the diffusivity-factor, is related with the extension of reactioneriod and limits the diffusivity expansion.

equation to nd a rate law catalytic tests with free H-USYrmed in ve replicated experiments. Seven differ-models assuming 2nd order reversible reaction wereely the pseudo-homogeneous model (PH), Langmuir-d assuming that the rate limiting step is the reactant(LH-RA), the surface reaction (LH-SR) or the prod-

tion (LH-PD) and Eley-Rideal also assuming that theg step is the reactant adsorption (ER-RA), the surface

Please citemembran


Fig. 6. Acetalization of phenylacetaldehyde and glycerol catalyzed by free H-USYat 100 C and using 99% pure glycerol. Fitting of the LH-SR kinetic model to experi-mental data. The insertion corresponds to the same reaction carried out at 70 C andusing 87% pure glycerol.

reaction (Efound as thKittrell [28Eqs. (4)(10

r A = k C2A0

{

k = 2.5222 Ke = 83259KA = 7.59 KB = 0.1013KC = 0.0321KD = 0.006where X is of phenylacconcentratiresults of th

Fig. 6 shows the tting of the LH-SR kinetic model to dataobtained with the free H-USY.

3.3.3. Mole balances to the membraneThe mole balance of component A over a differential element of

depth dz in pseudo-steady state conditions may be written as:

d2CAdz2

+ membDe

rA = 0 (11)

being De the phenylacetaldehyde diffusivity, memb the membranedensity and rA the reaction rate relative to phenylacetaldehyde.

3.3.4. Mole balances to the reactorFor batch reactor the mole balance equations may be written as:

dClAdt

= WV

RobsA (12)

dClBdt

= WV

RobsA (13)

dClCdt

= WV

RobsA (14)

dCl W

V

ClA, Cnylac

eige voln rel

L

0

L is t

Den con

mem

sorpA C

sorpA C

sorp

Table 2Variance analy

Kinetic mod

PH

LH-RA

LH-SR

LH-PD

ER-RA

ER-SR

ER-PD

Pure error andvalue of time, were obtainedR-SR) or the product desorption (ER-PD). LH-SR wase best model by using variance analysis according to], being the rate law in the range 373403 K given by):

(1 X)(

B X)

X2/Ke[1 + KA CA0 (1 X) KBCA0

(B X

)+ KCCA0X + KDCA0X

]2}

(4)

e851.767/T (5)

0 e4716.07

T (6)

107 e+4872.56/T (7)

e628.84/T (8)

e177.76/T (9)

9 e139.07/T (10)

fractional conversion, CA0 is the initial concentrationetaldehyde and B = CB0/CA0 is the ratio of the initial

D

dt=

whereof pheis the wV is threactio

RobsA =

where

3.3.5. The

on the

CSA = K

CSB = K this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

ons of glycerol (B) and phenylacetaldehyde (A). Thee variance analysis are shown in Table 2.

where Ki

brane, calcu

sis for kinetic model selection.

el Sum of squares Degrees of freedom

Pure error 0.18058 56 Residuals 0.42151 68 Lack-of-t 0.24093 12 Residuals 0.36156 65 Lack-of-t 0.18098 9 Residuals 0.30020 65 Lack-of-t 0.11962 9 Residuals 0.34229 65 Lack-of-t 0.16171 9 Residuals 0.36156 65 Lack-of-t 0.18098 9 Residuals 0.33895 65 Lack-of-t 0.15837 9 Residuals 0.34229 65 Lack-of-t 0.15649 9

residuals were taken as the differences between the experimental conversion values and for ve replicated experiments. The lack-of-t sum of squares is the difference between

for = 0.0004.anes for hyacinth avour synthesis in a pervaporation2.052

RobsA (15)

lB, C

lC , and C

lD are the concentrations in the liquid phase

etaldehyde, glycerol, acetal and water, respectively; Wht of zeolite in the membrane used in the reaction andume of the reaction mixture. RobsA is the observed rateative to phenylacetaldehyde dened as:

rAdz

L(16)

he membrane half thickness.

ition of boundary conditionscentrations of phenylacetaldehyde (A) and glycerol (B)brane surfaces (z = L) are obtained from:lA (17)

lB (18)

is the sorption coefcients of component i in the mem-lated from the swelling data (Table 1).

Variance Variance ratio Critical F-value

0.003220.00620 6.226 3.7020.020080.00556 6.236 4.1380.020110.00462 4.122 4.1380.013290.00527 5.572 4.1380.017970.00556 6.236 4.1380.020110.00521 5.457 4.1380.017600.00527 5.241 4.1380.01739

its average or the value calculated by the model, respectively, for each the sum of squares of residuals and pure error. The critical F-values

Please citemembran


Fig. 7. Effect of H-USY loading on model parameters.

On the other hand in the membrane centre (z = 0) the reactantconcentrations achieve a minimum value:

dCAdz

= 0

dCBdz

= 0

3.3.6. ModeThe mod

obtained wiparameters

3.3.7. ModeA MATL

cally the di(17)(20) aneter estimathe sum of

optimization algorithm. The integration of the reactor mole bal-ance Eqs. (1

h CP calctiontegrae in

tensinda

m (BcentrBTM

Modece foreneoeters

In fave la

Fig. 8. Membrand the highes(19)

(20)

l parametersel was tted to the data points of concentration prolesth the membranes described in Table 1, by changing the

De0, , and .

lling calculationsABTM program was developed for solving numeri-fferential Eqs. (5)(15) with the boundary conditionsd for estimating the unknown parameters. The param-

tion algorithm consisted of a standard minimisation of squared errors employing the LevenbergMarquardt

the higThe

integraond inrst timally inthe bouproblebrane MATLA

3.3.8. Sin

homogparambrane.selecti this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

ane phenylacetaldehyde concentration proles calculated assuming symmetrical homot (Y20G02) zeolite loading, at the initial reaction time (t0) and the nal reaction time (tf )2)(15) was performed using the Euler method due toU requirements.ulation of the observed reaction rate RobsA requires the

of the membrane material balance Eq. (11). This sec-tion over the spatial coordinate z is embedded in thetegration of Eqs. (12)(15) resulting in a computation-ve algorithm. The numerical solution of Eq. (11) withry conditions (17)(20) is classied as a boundary valueVP) because the conditions are formulated at the mem-e (z = 0) and (z = L). For solving this problem the bvp4croutine was used.

l calculation results modelling purposes the membranes were assumed asus and symmetrical, the values found for the different

must be regarded as mean values for the whole mem-ct one should expect that the catalytic layer and theyer have very different transport properties.anes for hyacinth avour synthesis in a pervaporation2.052

geneous membranes, for the membranes with the lowest (Y05G02).

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Fig. 9. Effect of polymer cross-linking on the model parameters.

3.3.8.1. Effect of zeolite loading. The calculated initial diffusivitydecreases when the zeolite loading increases (Fig. 7) suggest-ing that the zeolite particles act as barriers to the transport ofthe reactanity enhanciincreases, schains moving, decreathe inductia spacer is of acetal mity of that schains. Theing of tho

of zeolite loading. However, for higher loadings, the increase ofmembrane rigidity and the consequent decrease of the ability ofdiffusivity enhancement leads also to a decrease of the induction

. 8 sh

fort (Y2e n

cataraneeme

. Effeed fots across the membranes. Simultaneously the diffusiv-ng factor () also decreases when the zeolite loadinguggesting that the H-USY particles limit the polymerements. Parameter shows a maximum at 10% load-sing for higher loadings. A possible interpretation foron period (to which is related) is the following: ifintercalated between the polymer chains the bindingolecules to the PVA OH groups in the close proxim-pacer becomes ineffective on separating the polymer

length of the induction period corresponds to the ll-se ineffective zones which increase with the increase

periodFig.

culatedhighesand thlowestmembimprov

3.3.8.2observ this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

Fig. 10. Effect of polymer acetylation on the modows the phenylacetaldehyde concentration proles cal- the membranes with the lowest (Y05G02) and the0G02) zeolite loading, at the initial reaction time (t0)al reaction time (tf). It becomes evident that for thelyst loading there is a signicant enhancement of the

transport properties while for the highest loading thatnt is not so signicant.

ct of polymer cross-linking. Similarly to what wasr the effects of zeolite loading initial diffusivity alsoanes for hyacinth avour synthesis in a pervaporation2.052

el parameters.

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3.4. Catalyt

In ordertest was caPVA memb

(Y20G02), working as described in Section 2.3. Fig. 11 shows theproles of phenylacetaldehyde conversion and permeated water.The observed initial induction period is likely to be due to theacetal interaction with the polymer matrix as mentioned above.

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Perm

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d w

ater

(mol)

Time (h)

rsion and permeated water proles obtained in the pervaporationrane reactor equipped with membrane Y20G02.

hen cross-linking increases (Fig. 9) being the expla-identical to that given above: the cross-linker acts as aering the transport of the reactants. However parame-

behave differently, increasing with cross-linking until at 8% cross-linking and then decreasing for higherg degrees. A possible explanation is that for lower cross-rees the cross-linker acts as a spacer facilitating then of acetal molecules between the polymer chains.

concerns parameter , that intercalation separateser chains enhancing the reactants diffusivity. Thisnt increases with cross-linking. The explanation for thef parameter is similar to that given above: the bind-al molecules in the close vicinity of the cross-linkereffective for the separation of polymer chains. Wheng increases the number of ineffectiveness zones alsoor 10% cross-linking the membrane rigidity explains the

parameters e .

ct of polymer acetylation. When the polymer acety-ases the calculated initial diffusivity decreases (Fig. 10).nexpected result because it would be expectable thate in interchain hydrogen bridging due to the blockingroups by acetyl groups, would lead to the improvementbranes transport properties. A possible explanation is

The amof acetPhenylsolutio

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(20 this article in press as: T.F. Ceia, et al., PVA composite catalytic membre reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2014.0

e of hydrogen binding between the glycerol molecules OH groups. As glycerol itself can also act as a spacer

polymer chains apart from each other, the decrease in of PVA OH groups leads to the decrease in the number oflecules bonded to the polymer chains. Consequently theains would become closer to each other explaining the

initial diffusivity. Although the glycerol swelling resultsat erratic, a decrease in the swelling degree seems tohen the acetylation degree increases (Table 1), givingrt to the above hypothesis.er decreases when acetylation increases because theOH groups available for hydrogen bonding decreasesre decreases the intercalation of acetal molecules.

ic membrane reactor experiments

to check if pervaporation takes place, a preliminaryrried out in a membrane reactor assembled with arane loaded with 20% H-USY and with 2% cross-linking

[7] M.R. Cape198 (200

[8] S.P. Chop[9] I. Vankele

[10] M.G. Buo2634.

[11] B. Van de(Eds.), CoKindlingt

[12] D.J. Benewith/with

[13] G. Bengts[14] M.T. Sanz

with perv123 (200

[15] I. Agirre, MSci. 371 (

[16] V.S. Prapt[17] J.E. Casta

(2005) 29[18] H.S. Mans

539548[19] A. Hernn

Scanningand heteranes for hyacinth avour synthesis in a pervaporation2.052

t of permeated water was calculated from the amountd formed in the permeated solution (acetic anhydride).aldehyde or glycerol esters were not detected in thisowing the good selectivity of the membrane to water.etailed study in membrane reactor in which low gradesed, is being carried out and will be reported in a future

ions

mbranes loaded with H-USY were successfully cross- glutaraldehyde and have shown good catalytic activitylization reaction of phenylacetaldehyde with glycerol.ication of zeolite loading, polymer cross-linking or

etylation allow the tuning of the membranes transport

on-kinetic model assuming a dependence of phenylac- diffusivity on acetal concentration ts quite well the.lts from the experiment carried out in a catalytic mem-or operating under sweep gas pervaporation conditionse good selectivity of the membrane to water and showplementation of the reaction and separation in a singleble.

gements

rk has been supported by national funds throughara a Cincia e a Tecnologia, Ministrio da Educac oFCT-MEC) under PEst-C/EQB/LA0006/2011 and PTDC/14579/2009 projects, and grant SFRH/BPD/26961/2006.

ent, A. Corma, A. Velty, Appl. Catal., A 263 (2004) 155161.esaria, G. Martinez Vicente, M. Di Serio, R. Tesser, Catal. Today 19513.

X. Chen, Y. Shen, Chem. Rev. 108 (2008) 52535277.t, A.Z. Abdullah, A.R. Mohamed, Renewable Sustainable Energy Rev.) 9871000.a, I.M. Fonseca, A.M. Ramos, J. Vital, J.E. Castanheiro, Appl. Catal., B 916422.a, I.M. Fonseca, A.M. Ramos, J. Vital, J.E. Castanheiro, Appl. Catal., B 9899.letti, L. Balzano, G. de la Puente, M. Laborde, U. Sedran, Appl. Catal., A

0) L1L4.ade, M.M. Sharma, React. Funct. Polym. 34 (1997) 3745.com, Chem. Rev. 102 (2002) 37793810.nomenna, S.H. Choi, E. Drioli, Asia-Pac. J. Chem. Eng. 5 (2010)

r Bruggen, Pervaporation membrane reactors, in: E. Drioli, L. Giornomprehensive Membrane Science and Engineering, 3, Elsevier B.V.,on, 2010, pp. 135163.dict, S.J. Parulekar, S.P. Tsai, Esterication of lactic acid and ethanolout pervaporation, Ind. Eng. Chem. Res. 42 (2003) 22822291.on, M. Oehring, D. Fritsch, Chem. Eng. Process. 43 (2004) 11591170., J. Gmehling, Esterication of acetic acid with isopropanol coupledaporation: Part I: kinetics and pervaporation studies, Chem. Eng. J.

6) 18..B. Guemez, H.M. van Veen, A. Motelica, J.F. Vente, P.L. Arias, J. Membr.

2011) 179188.owidodo, J. Mol. Struct. 739 (2005) 207212.nheiro, I.M. Fonseca, A.M. Ramos, R. Oliveira, J. Vital, Catal. Today 1046304.ur, C.M. Sadahira, A.N. Souza, A.A.P. Mansur, Mater. Sci. Eng. 28 (2008).dez, P. Prdanos, L. Palacio, R. Recio, A. Marcos-Fernndez, A. Lozano,

probe microscopy techniques in the investigation of homogeneousogeneous dense membranes: the case for gas separtion membranes,

Please cite mbrmembran 014.0


in: C. Gell, M. Ferrando, F. Lpez (Eds.), Monitoring and Visualizing Membrane-Based Processes, Wiley-VCH, Weinheim, 2009, p. 91.

[20] J. Vital, A.M. Ramos, I.F. Silva, J.E. Castanheiro, Catal. Today 67 (2001)217.

[21] J.E. Castanheiro, A.M. Ramos, I.M. Fonseca, J. Vital, Appl. Catal., A 311 (2006)1723.

[22] L. Guerreiro, P.M. Pereira, I.M. Fonseca, R.M. Martin-Aranda, A.M. Ramos, J.M.L.Dias, R. Oliveira, J. Vital, Catal. Today 156 (2010) 191197.

[23] S. Wu, J.-E. Gallot, M. Bousmina, C. Bouchard, S. Kaliaguine, Catal. Today 56(2000) 113.

[24] A. Yawalkar, V. Pangarkar, G. Baron, J. Membr. Sci. 182 (2001) 129137.[25] J.M. Sousa, P. Cruz, A. Mendes, Catal. Today 67 (2001) 281.[26] J.M. Sousa, P. Cruz, A. Mendes, J. Membr. Sci. 181 (2001) 241.[27] E. Nagy, Ind. Eng. Chem. Res. 46 (2007) 22952306.[28] J.R. Kittrell, Adv. Chem. Eng. 8 (1970) 97. this article in press as: T.F. Ceia, et al., PVA composite catalytic mee reactor, Catal. Today (2014), http://dx.doi.org/10.1016/j.cattod.2anes for hyacinth avour synthesis in a pervaporation2.052

PVA composite catalytic membranes for hyacinth flavour synthesis in a pervaporation membrane reactor1 Introduction2 Experimental2.1 Preparation of catalytic composite membranes2.2 Membranes characterization2.3 Catalytic experiments

3 Results and discussion3.1 Characterization of the catalytic membranes3.1.1 Solvent absorption and water contact angle3.1.2 FTIR spectroscopy3.1.3 Membrane morphology

3.2 Catalytic tests3.2.1 Batch experiments

3.3 Membrane modelling3.3.1 Basic assumptions3.3.2 Rate equation3.3.3 Mole balances to the membrane3.3.4 Mole balances to the reactor3.3.5 Definition of boundary conditions3.3.6 Model parameters3.3.7 Modelling calculations3.3.8 Model calculation results3.3.8.1 Effect of zeolite loading3.3.8.2 Effect of polymer cross-linking3.3.8.3 Effect of polymer acetylation

3.4 Catalytic membrane reactor experiments

4 ConclusionsAcknowledgementsReferences

1-s2.0-s092058611400234x-main

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