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NANOMATERIAL AND CATALYSIS

Submitted toDr.A.Kasi.VishwanathReaderCenter for Nanoscience & Technology

Submitted ByRosalin BeuraM.Tech(NST) 1st yr

NST-611Introduction to Nanotechnology

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OutlineINTRODUCTION CATALYSTSNEED FOR NANOCATALYSTSPREPARATION METHODSCURRENT TECHNOLOGYAPPLICATIONSREFERENCES

Nanorust cleans arsenic from drinking water.(Image courtesy of Rice University

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CatalysisCatalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself.

What is catalyst ? A catalyst is a substance other than reactants ,products added to a reaction system to alter the speed of a chemical reaction approaching a chemical equilibrium. A catalyst changes the activation energy, Ea, of a reaction by providing an alternate pathway for the reaction. k = A exp (- E

a / R T) Where, k= rate of reaction A= constant related to collision rates Ea=Activation energy R=Rydberg constant T=temperature

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A catalyst may participate inmultiple chemical transformations

Increase reaction rate= positive catalysts slow reaction rate= inhibitorsSubstances that increase the activity of catalysts= promoters Substances that deactivate catalysts activity= catalytic poisons.

http://www.rsc.org/images/distillates

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Generic potential energy diagram showing the effect of a catalyst in a hypothetical exothermic chemical reaction X + Y to give Z. The presence of the catalyst opens a different reaction pathway (shown in red) with a lower activation energy. The final result and the overall thermodynamics are the same.

How does a catalyst works?

Changes the activation energy----by offering an alternative pathway----which requires less K.E. in molecular collision

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Types of Catalysts

HeterogeneousActs in the different medium from that of the reactant

HomogeneousActs in the same medium as that of the reactant

Mostly solids that act on substrates in a liquid or gaseous reaction mixture

Typically homogeneous catalysts are dissolved in a solvent with the substrates

Eg. Haber process H2+3N2 2NH3

Eg.influence of H+on the esterification of esters, methyl acetate from acetic acid and methanol

Fe

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Other catalystsElectrocatalystsGenerally in electrochemistry= fuel cell engineering

Eg.- Platinum nanoparticles supported on slightly larger carbon particles. When in contact with one of the electrodes in a fuel cell, this Pt the rate of oxygen reduction to water, either to hydroxide or hydrogen peroxide.

OrganocatalysisSmall organic molecules without metals exhibits catalytic properties, apparent from the fact that many enzymes lack transition metals

The discipline organocatalysis is divided in the application of covalent (e.g., proline) and non-covalent (e.g., thiourea organocatalysis) organocatalysts referring to the preferred catalyst-substrate binding and interaction, respectively.

Autocatalysts- catalysis in which the catalyst is one of the products of the reaction

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Some catalysts

Fuel catalyst

Reactor with IC-47catalyst

Catalytic Convertor

Ceramic catalyst used in industry

Bio catalyst

Diesel engine–based construction equipment, a large potential application for the nanocatalyst technology.

Alps Bio Cluster Catalyst event on "Biotherapy and Diagnostics"

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Basic Principles of chemistry

For any chemical reaction to occur, two reactive species must come in contact with each other.

Why nanocatalysts is so promising ??

The total surface area of solid has an important effect on the reaction rate. The smaller the catalyst particle size, the larger the surface area for a given mass of particles.

http://nanocat.kaust.edu.sa/PublishingImages/KCC

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Key concept to understanding nanocrystal catalysis involves the ratio of surface area and volume.

2 in

ches

2 inches

Volume=8 cubic inchesSurface area=24 sq. inchesSurface :Volume =24:8=3

Volume=1cubic inchSurface area=6 sq. inchesSurface :Volume =6:1=6

1 inch

1 inch

Surface to volume ratio increases with reducing the size

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NanocatalystsA Nanocatalyst is a substance or material with catalytic properties that has at least one nanoscale dimension, either externally or in terms of internal structures.

Generally, catalysts that are able to function at atomic scale are Nanocatalysts.

Nano-materials are more effective than conventional catalysts for two reasons. Extremely small size (typically 10-80 nanometers) yields a tremendous surface area-to-volume ratio. Materials fabricated on the nanoscale achieve properties not found within their macroscopic counterparts.

Both of these reasons account for the versatility and effectiveness of nanocatalysts.

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Growing interest• The chart below represents the number of the

publish reports on nanostructured metal catalyst

http://www.bepress.com/cgi/viewcontent.cgi?article=2132&context=ijcre

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Specific metal catalyst Interest in specific elements in the preparation of Nanoparticles in the period 2000-2007

http://www.bepress.com/cgi/viewcontent.cgi?article=2132&context=ijcre

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Early milestones in nanocatalysis1. Refinery industry started the use of precious metal

platinum(Pt) as a reforming catalyst half century ago to increase octane no of gasoline .

Bimetallic catalyst was made to increase the performance and life of the catalyst.

Way to improve performance and reduce catalyst cost Engineer smaller sized catalyst particles Dispersion of catalyst metal in a desired way.

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2. Nanostructure catalysts:Zeolites Zeolites were developed in 1960 Zeolites are special bcoz of their coustamizable cage

like structure .By changing the sizes of the hole in the cage different molecules can be allowed to keep out of the zeolite to only produce desired reaction thus preventing formation of unwanted byproducts.

Zeolites are mainly used in refining application

http://www.google.co.in/search?q=zeolite

Zeolites

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Nanocatalysts

http://nanocat.kaust.edu.sa/Documents/nano-catalyst-

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SYNTHESIS TECHNIQUES

Micellar Chemical Vapor Deposition

Hydrothermal processing

High-energy ball milling Microemulsion

Sol-gel Plasma

Out of all the above methods, Advantages of Sol-gel &hydrothermal synthesis are :• Produce materials at low temperatures• Produce commercially viable quantities relatively cheap• Synthesize single, binary or more material systems• Produce extremely homogeneous composites• Precisely control the physical, chemical and mechanicalproperties of the final products

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Current technologyThe control of catalyst nanoparticles size ,composition, dispersion , crystal structure exposure and stability is the key to producing pure ,efficient and strong catalysts and from marketing perspective ,it is crucible to be able to control these features at low or competive cost.

Ultimately to meet both the scientific requirements the catalyst must be highly selective ,highly active and unerringly stable and the market imperative the production must be cost effective .

arabianoilandgas.com

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atoms size =no of precious particles less cost .

1. Controlling Size:Nanoparticle catalystsConventional catalyst contains small nanoparticles ,along with the mixture of much larger particles.Eg.20nm particles contains 384,000 atoms of precious metal 3 nm particle contains 1,300 atoms i.e. 300 times fewer Exposed surface=active part & inner part value is lost.

Controlling size –desired result can be generate thus eliminating the waste.Current method for preparing the nanosize distribution are Dendrimer control method Surfactant use method

2. Composition controlSingle metals are used successfully for many catalysts. Use of multiple metal increase the strength of the catalyst

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3. Controlling StructureConventional chemical catalysts were made of active nanoparticles with combination of different crystal structures.nanotechnology controlling the catalysts structure allows the exposure of the desired crystal structure ,and thus resulting desired reaction.Eg. Molecular sieve materials as MCM-41

http://www.google.co.in/imgres?q=molecular+seive+material+MCM-41

MCM-41

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4. Achoring nanoparticles and Nanostructure CatalysisThe ability to make smaller nanoparticles is a big challenge, since nanoparticles tend to agglomerate into larger particles.This can be prevented by using chemical or polymer templets to stabilize the particles.This Anchoring method increase the life time of the catalyst.

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Application

Carbon nanotubes

Water purification

Bio diesel production

Fuel cell application

In drug delivery

Photocatalytic activity

In solid rocket propellants

TiO2 in energy application

Thin film solar cell

Waste water treatment

In environment protection

Nano catalyst

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Waste water treatmentFor special industrial wastewaters contaminated with traces of halogenated organic compounds (HOCs) – concn which are nevertheless large enough to make a discharge into municipal sewage works impossible.The idea to detoxify the water by a selective destruction of the HOCs by hydrodehalogenation (HDH) reactions on palladium-containing nano-catalysts. RX + H2 RH + HX

Extremely active palladium catalysts were generated on the basis of ferromagnetic carrier colloids. The ferromagnetism of the carriers enables a separation of the catalysts from the treated water by means of magneto-separation.

Pd-Catalyst

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Biodiesel productionThe general method for the preparation of biodiesel is trans esterification reaction of oil and alcohol with homogeneous catalyst. The catalyst is well used to convert the oil with higher acid value into biodiesel. It is porous with particle sizes of 30–100 nm. The high specific surface area and large pore size are favorable for contact between catalyst and substrates,which effectively improved efficiency of trans esterification. Production of biodiesel from Chinese tallow seed oil has positive impact on the utilization of agricultural and forestry products.

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In environment protectionSulfate radical-based advanced oxidation technologies (SRAOTs) are attracting considerable attention due to the high oxidizing ability of SRs to degrade organic pollutants in aqueous environments.

Typically, a mature landfill leachate contains high levels of non-biodegradable organics and ammonia nitrogen. Simultaneous removal of the both persistent pollutants is a challenge. Scientific study to apply a sulfate radical (SO(4)(·-))-based advanced oxidation process to treat a mature leachate, with an emphasisof concurrent removal of refractory organics and ammonia

http://www.sciencedirect.com/science/article

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PhotocatalysisPhotocatalysis is the acceleration of a photoreaction in the presence of a catalyst. Here photocatalytic activity (PCA) depends on the ability of the catalyst to create electron–hole pairs, which generate free radicals (e.g. hydroxyl radicals: •OH) able to undergo secondary reactions.For this we need a semiconductor.The parameters of the photocatalysts that control the efficiency of the reaction are morphology,specific surface area,particle size, crystal phase,surface defects etc.From the available semiconductor TiO2 is so far the most useful.It exists in two forms anatase(3.23) & rutile(3.02) .This energy gap combine with The valence band positionto generate highly energetic holesgiving rise to easy oxidation reaction.

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In nanocrystalline substance the alteration of the band gap to larger value facilitates the oxidation /reduction reaction which cannot be proceeded in bulk semiconductor.The change in the surface atoms results in the increase in the surface energy.Reduction of particle size increase in the energy of formation of electron –hole pair and shifts the conduction and valence band towards more negative & more positive potential respectively.Increase in band gap favours the water splitting & oxidation of organic compounds that have slightly higher potential than the potential of valence bond in the bulk.

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R&D INVESTMENT AND IMPLEMENTATION STRATEGIES In 2009 WTEC (World Technology Evaluation Center )catalysis report (Davis et al.2009) noted that “the overall level of investment in catalysis research in Europe appears to be higher than that in US”.The report noted that “Europeans and Asians countries have done excellent job combining academic research with national labrotary activities. ”The ability to monitor catalysts with the appropiate resolutio in their working state is critical to understanding & thus control of nanoscale cataysts .Nanostructured catalysis has the potential to profoundlly affect our quality of life & should be reflected through investment in research & development in this area.The two challenging factors in the area for nanotechnology for catalysis are Predictive design &fabrication of bulk catalystparticles with nanongineered porosity over multiple length scale.

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ConclusionThe field of nanocatalysis (the use of nanoparticles to catalyze reactions) has undergone an explosive growth during the past decade, both in homogeneous and heterogeneous catalysis.Nanoparticles have a large surface-to-volume ratio compared to bulk materials, they are attractive to use as catalysts. Catalysts daily accelerate and boost thousands of different chemical reactions, and thereby form the basis for the multibillion dollar chemical industry worldwide and indispensable environmental protective technologies.

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References1. Applications of nano-catalyst in new era Shalini Chaturvedi a, Pragnesh N. Dave a,*, N.K. Shah b, Journal of Saudi Chemical Society (2012) 16, 307–3252. NOVEL NANO-CATALYSTS FOR WASTEWATER TREATMENT, Global NEST Journal, Vol 10, No 1, pp 47-53, 20083. Global NEST Journal, Vol 10, No 1, pp 47-53, 2008, Int. J. Electrochem. Sci., 6 (2011) 4572 - 4580 4 .Nanocrystals: Solution-Based Synthesis and Applications as Nanocatalysts Nano Res (2009) 2: 30 465 Local Ordering Changes in Pt−Co Nanocatalyst Induced by Fuel CellWorking Conditions Giorgia Greco, Agnieszka Witkowska6.Nanoparticles and Nanostructure Catalysis:Technologies and Markets-Bing Zhou,Ray Balee,Rebecca Groenendaal

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THANK YOU