nano catalysis as a prospectus of green chemistry
TRANSCRIPT
NANOCATALYSIS AND PROSPECTUS OF GREEN CHEMISTRY
Prepared and represented by:Ankit groverMsc.(h .s)chem.2nd year
Higher activity,
Higher selectivity,
Efficient recovery
Cost-effectiveness.
Durability
Overview
Refernces
Introduction Nanoparticles Catalysis
Gold nanocatalysis: oxidation reactions
Magnetically separable nanocatalysts
Applications of Nanocatalysts Hydrogen storage for fuel cell applications
Intoduction
Factor Prefix Symbolo 10-1 deci d o 10-2 centi co 10-3 milli mo 10-6 micro µo 10-9 nano n o 10-12 pico po 10-15 femto f
Actually the nanoparticles are particles with sized between 100 and 1 nanometers
What Is The Meaning Of Nanoparticles?
GOLD NANOPARTICLES
5
Catalysis
• Catalyst - a substance that initiates or accelerates a chemical reaction without itself being affected
A + B C + DActivation energy
catalyst
oil refining petrochem polymersfine chemicals pharma environmental
Traditional catalyst markets
Annual catalyst market $12 - 15 Billion
25 °C0% yield100% yield!!
What is the meaning of nano for catalysis?
Cubic (7.2 nm)(More active)
Spherical(4.8)(Less active)
Nanosize imparts special properties to the material by its structural and electronic changes.Bcz in case of nanoparticles activity is the function of electronic and structural function.
Activity of a catalyst Surface area of catalyst∝For conventional catalyst’s .There is direct relation between activity and area of the catalyst
Big picture: Sustainable Development
Waste prevention
Atom economy
Less hazardous chemistry
DesigningOf safer chemicals
Safer solventsAnd auxillries
Energy efficiency
Reduce the use Of chemical derivatives
catalysis
Design fordegradation
Real time Analysis forPollution prevention
Safer chemistry
Green chemistry is a philosophy that puts forward sustainable concepts, which are designed to reduce or eliminate chemicals and chemical processes that have negative environmental impacts and it based on 12 principle’s.
RenewableFeedstock
Waste prevention
Atom economy
Less hazardous chemistry
DesigningOf safer chemicals
Safer solventsAnd auxillries
Energy efficiency
Reduce the use Of chemical derivatives
catalysis
Design fordegradation
Real time Analysis forPollution prevention
Safer chemistry
Green chemistry is a philosophy that puts forward sustainable concepts, which are designed to reduce or eliminate chemicals and chemical processes that have negative environmental impacts and it based on 12 principle’s.
RenewableFeedstock
catalysis
Designing and developing ideal catalysts paves the way to green chemistry.
Green and sustainable catalyst should posses:
higher activity,
higher selectivity,
cost-effectiveness.
efficient recovery from reaction medium
durability or recyclability, and
Gold nanocatalysis: oxidation reactions
The pt/pd catalysts that are currently used in cars for CO oxidationWork only at temperatures above 200C, so most of COPollution occurs in the initial minutes after starting theEngine.
Au catalyst could solve this problem because of the complexity involved in Au/metal oxide catalysts.
History:
The bare Au6
Adsorbs molecular oxygen In the superoxo form
SubsequentCo-adsorption of CO may initially yield an au6co3
Species
Rearranges to produce the very stable CO3
-
Adsorbate
Elimination ofCO2 yields the Au6O- form
Adsorption of a second CO yields theAu6CO2
Mechanism:
Efficient recovery of the catalyst from the reaction medium after the completion of reaction is the key factor that determines its usage for practical applications
Magnetically separable nanocatalysts :
Anchoring colloidal particles or homogeneous catalysts on magnetic supports (nanoparticles) is an ideal solution to this problem.
Nanoparticles catalyst
Hetrogeneous catalyst’s
Homogeneous catalyst’s
Anchoring of homogeneous catalystschiral Ru-based complex was anchored successfully on Fe3O4 nanoparticles
Ru(II) complex [Ru(BINAP-PO3H2)(DPEN)Cl2]
Phosphonic acid group attached to the BINAP ligand acts as a linker and binds to the surface of Fe3O4 nanocrystal surface.
Anchoring of homogeneous catalystschiral Ru-based complex was anchored successfully on Fe3O4 nanoparticles
This catalyst was successfully used for the hydrogenation of a range of aromatic ketonesto the corresponding secondary alcohols with high enantioselectivity.
catalyst was tested up to 14 cycles without loss of activity, and high enantiomeric excess (ee) values.Ru(II) complex [Ru(BINAP-PO3H2)(DPEN)Cl2]
Phosphonic acid group attached to the BINAP ligand acts as a linker and binds to the surface of Fe3O4 nanocrystal surface.
Nanocatalysts for Clean Energy Applications
H2 +O2 H2O+Energy
Totally green reaction and hydrogen has3 times more chalorific value than L.P.GExcept the problem of storage H2 is seems As good energy source.
(=-150 kJ/mol).
H2 can be preapred by 2 methods:
1)By hydrolysis of H2O
(G=237 kJ/mol).
2) from coal and natural gasby the steam reforming reactionleads to large CO2 emission as shown in picture.
Water splitting in the presence of a semiconducting photocatalyst(e.g., TiO2, TaON, and LaTiO2N). The nanotubular architecture allows for more efficient absorptionof incident photons as well as decreased bulk recombination.
It has been established that the presence of a cocatalyst greatly enhances the efficiency of the overall process. Noble metal- or transition metal-oxide nanoparticles are often used as cocatalysts to facilitate water reduction. These nanoparticles are dispersed on active photocatalysts by applying in situ photodeposition methods to produce activesites and reduce the activation energy for gas evolution
HRTEM image of Rh-GaN:ZnO catalyst:
Rh-GaN:ZnO photo-catalyst surface
Rh nanoparticles
Cr2O3 cocatalyst
HRTEM image of Rh-GaN:ZnO catalyst:
Rh core facilitates the transfer of photo-generated electrons from the bulk(GaN:ZnO) to the surface (Cr2O3). The Cr2O3 layer is permeable to protons and the evolved H2 molecules, but not to oxygen.Therefore, the backward reaction over the noble metal is prevented by the Cr2O3 shell
Applications of Nanocatalysts:Hydrogen storage
Being the lightest element Storing H2 at high pressures or at very low temperaturesis not economically viable. Chemical H2 storage involves storing H2 in the form ofchemical bonds. A number of materials with a high gravimetric .H2 content are explored as H2 storage materials.
Boron hydrides with a high gravimetric content of H2 havebeen widely studied as H2 storage materials; however, their regenerationprocess is energy intensive.Most of these materialsare stable at room temperature and do not react at a sufficientrate to warrant their application
Conclusions and Outlook:
Rational design for environmentally benign catalysts is possible.
nanocatalysts are widely applicable.For hydrogen storageFor fuel cell applicationsFor industrial manufacturing procesessIn pharma. industries
Academic application areas are limitless
References:
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[3] a) G. Ertl, D. Prigge, R. Schloegl, M. Weiss, J. Catal. 1983, 79, 359– 377;b) G. Ertl, Angew. Chem. 2008, 120, 3578– 3590; Angew. Chem. Int. Ed.2008, 47, 3524 –3535.
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