By -: Lovnish Thakur (IBT- 1st Sem)Enrollment No.-: ASU2014010100099Course -: Chemistry for biologist (102)

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Catalysis is the increase in the rate of achemical reaction due to the participationof an additional substance called acatalyst .With a catalyst, reactions occur faster and with less energy

Catalysts are substances which, when added to areaction, increase the rate of reaction by providing analternate reaction pathway with a lower activationenergy (Ea).

They do this by promoting proper orientation between reacting particles.

In biochemistry, catalysts are known as enzymes.

Catalyst Cycle

www.catalysis-ed.org.uk

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Catalyst Parameters

Homogeneous CatalysisThe catalyst and reactants are in the same phase, usually

liquid.

Heterogeneous catalysisCatalyst and reactants are in different phases.

Enzymatic CatalysisCatalyst is an enzyme (macromolecules made of amino

acids).

When the reactants and the catalyst are in the same phase (i.e., liquid or gas), the process is said to be homogeneous catalysis.For e.g -:

AdvantagesGood contact with reactants .

Disadvantageswww.ncert.nic.in/NCERTS/l/lech105.pdf

Catalysis needs to be separated after reactionCatalyst recovery may be difficult because the temperature for the distillation can destroy the catalyst

www.ncert.nic.in/NCERTS/l/lech105.pdf

The catalytic process in which the reactants and the catalyst are in different phases is known as heterogeneous catalysis.For e.g -:

AdvantagesThere is little difficulty in separating and recycling the catalyst.

DisadvantagesThere is a lower effective concentration of catalyst since the reaction occursonly on the exposed active surface.( www.knockhardy.org.uk)

Adsorption Theory of HeterogeneousCatalysis

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Numerous reactions that occur in the bodies of animals and plants to maintain the life process are catalysed by enzymes. The enzymes are, thus, termed as biochemical catalysts and the phenomenon is known as biochemical catalysis.

Enzymes are complex nitrogenous organic compounds which are produced by living plants and animals. They are actually protein molecules of high molecular mass

(i) Most highly efficient: One molecule of an enzyme may transformone million molecules of the reactant per minute.(ii) Highly specific nature: Each enzyme is specific for a given reaction.For example, the enzyme urease catalyses the hydrolysis of urea only.(iii) Highly active under optimum temperature(iv) Highly active under optimum pH

Mechanism of enzyme catalysis

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Catalysis reaction by sucrase

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Some example of enzyme catalysis reaction

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APPLICATION OF CATALYSIS

Catalysis impacts the environment by increasing the efficiency of industrial processes, but catalysis also plays a direct role in the environment

Green Chemistry is Catalysis

Pollution control(air and waste streams; stationary and mobile) Clean oxidation/halogenation processes

using O2,H2O2(C2H4O, C3H6O) Avoiding toxic

chemicals in industry( HF,COCl2 etc.)

Fuel cells( H2 generation)

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Catalytic Converters

One common applicationfor catalysts is forcatalytic converters.

Catalytic converters arefound in automobiles.

Their role is to reduce toemissions of harmfulgases (CO, VOC’s, NOx)that are the result of thecombustion of fuel invehicle engines.

ysis-ed.org.uk

Ozone gas depletion

There is catalytic role of chlorine free radicals inthe breakdown of ozone. These radicals are formed by the actionof ultraviolet radiation on chlorofluorocarbons (CFCs).

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www.okiu.ac.jp

Hydrogen Industry(coal, hydrogenations etc).Natural gas processing .Petroleum refining . www.ecopolychem.com

Petrochemicals(monomers, bulk chemicals).Fine Chemical(pharma, agrochem, fragrance, textile, coating, surfactants, laundry etc).Environmental Catalysis(autoexhaust).

Fine chemicalsMany fine chemicals

are prepared via catalysis; methods include those of heavy industry as well as morespecialized processes

that would be prohibitively expensive on a large scale.

www.essentialchemicalindustry.org

www.ncert.nic.in/NCERTS/l/lech105.pdf

shape-selective catalysisblogs.mcgill.ca blogs.mcgill.ca

The reaction that depends upon the pore structure of the catalyst & the size of the reactant & product molecules is called shape-selective catalysis.

Zeolites is used as catalysts in petrochemical industries for cracking of hydrocarbons and isomerisation.

An important zeolite catalyst used in the petroleum industry is ZSM-5.

It converts alcohols directly into gasoline (petrol) by dehydrating them to give a mixture of hydrocarbons.blogs.mcgill.ca

blogs.mcgill.ca

Energy processing Petroleum refining makes intensive use of catalysis for

alkylation , catalytic cracking (breaking long-chain hydrocarbons into smaller pieces) , naphtha reforming

and steam reforming (conversion of hydrocarbons into synthesis gas). Fuel cells depend on catalysts for both the anodic and

cathodic reactions. Catalytic heaters generate flameless heat from a supply

fuel

One of the most obvious applications of catalysis is the hydrogenation (reaction with hydrogen gas) offats using nickel catalyst to produce margarine .Many other foodstuffs are prepared via bio catalysis

References www.etrailer.com blogs.rsc.org www.catalysis-ed.org.uk commons.wikimedia.org www.ncert.nic.in/NCERT/1/lech105.pdf www.knockhardy.org.uk Blog.mcgill.org.uk Ysis-ed.org.uk www.ecopolychem.com

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