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Durairajan et al. Experimental investigation and control the toxic emissions in IC engines by nano materials, Discovery Sci., 2012, 1(1), 3-9, www.discovery.org.in www.discovery.org.in/ds.htm © 2012 discovery publication. All rights reserved

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Durairajan A1,*, Kavitha T2, Rajendran A2

1. Department of Mechanical Engineering, K.S.R. College of Engineering, Tiruchengode-637215, Namakkal (DT), Tamil Nadu, India, E-mail: [email protected]

2. Department of Physics, Nehru Memorial College, Puthanampatti, Trichy, Tamil Nadu, India, E-mail: [email protected] 3. Department of Physics, Nehru Memorial College, Puthanampatti, Trichy, Tamil Nadu, India, E-mail: [email protected]

*Corresponding author: Durairajan A, Department of Mechanical Engineering, K.S.R. College of Engineering, Tiruchengode-637215, Namakkal (DT), Tamil Nadu, India, E-mail: [email protected], Tel: (+91) 8015655878.

Received 17 April; accepted 19 May; published online 25 June; printed 29 June 2012

ABSTRACT Automobile plays an important role in contribution to the pollution. Air pollution is predominately emitted through the exhaust of motor vehicles and the combustion of fossil fuels. Pollution control is playing a vital role to control the future generation and toxic emissions like CO, NOX and HC. The objective of the work is to reduce the emissions from the automobiles through design and manufacturing of nano catalytic converter by replacing the existing expensive metals such as Platinum. Nano Materials like nano Rhodium and nano Palladium were obtained by using chemical vapour deposition (CVD) technique. The obtained nano powder was deposited in the honey comb structure. By using the nano catalytic converter the pollution is reduced.

Key words: Nano catalytic converter; Nano palladium; Nano rhodium; Nano materials; Automobile pollution; CVD.

Abbreviations: CVD - Chemical vapour deposition; NM - Nano Meter; HC - Hydrocarbon; NOx - Nitrogen-di-oxide; CO - Carbon- monoxide; SI - Spark ignition; CI - Compression ignition.

1. INTRODUCTION Nanotechnology is a science of controlling individual atoms and molecules. One of the serious problems facing the world is the drastic increase in environmental pollution by internal combustion engines. All transport vehicles; both SI (Spark ignition) and CI (Compression ignition) are equally responsible for emitting different kind of pollutants (Rajadurai and Tagomori, 2000). Two stroke SI engines have certain advantages such as compactness, lightweight, simple construction and low cost and low nitric oxide emissions; they suffer from problems of high specific fuel consumption, high hydrocarbon and high carbon monoxide emissions. Some of the primary kinds having direct hazardous effects such as carbon mono oxide, hydrocarbons, nitrogen oxides, etc. other, the secondary pollutants, which undergo a series of reactions in the atmosphere and become hazardous to health (Joseph et al., 2001). The emissions exhausted into the surroundings pollute the atmosphere and cause global warming, acid rain, smog, odors, and respiratory and other health hazards. A pollutant is a phenomenon

which changes the balance of the environment and nature under normal condition. Carbon-di-oxide is not considered as pollutant, as nature recycles. If carbon-di-oxide exceeds 5000ppm, then it becomes a health hazard. Using nano catalytic converter, pollution is controlled by means of catalytic reaction (Ketteler et al., 2002).

2. MATERIALS AND METHODS 2.1. Synthesis In general, synthesis of nanoparticles refers to a combination of two or more entities that together form something new; alternately, it refers to the creating of something by artificial means (Table 1 and Table 2).

1. Laser ablation 2. Arc discharge 3. Plasma enhanced CVD 4. Chemical vapor deposition (CVD)

Here we used CVD method (Fig.1 and Fig.2) to synthesis the Nano palladium & Nano rhodium

1. Easy method 2. Gas phase deposition 3. Large scale possible

RESEARCH Discovery Science, Volume 1, Number 1, July 2012

Science

Experimental investigation and control the toxic emissions in IC engines by nano materials

Chemical Vapour Deposition (CVD): The execution of chemical reactions to form a more complex molecule from chemical precursors.

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4. Relatively cheap Here the oven is maintained at 7200c, palladium is kept above the quartz boat as a sample. The C2H2 and N2 is passed through the quartz tube.

2.2. Automobile Pollution It is defined as the introduction of chemicals, particulate matter, or biological materials to the atmosphere that cause harm or discomfort to the living organisms. Due to the advancement in science and technology there is a drastic improvement in automobile production which results in more amount of harmful gas is let into the atmosphere. These gases react with the atmosphere and pollute it.

2.3. Catalytic converter A “catalytic converter” is a device used to reduce the toxicity of emissions from an internal combustion engine. A catalytic converter converts the harmful toxic combustion products and its byproducts into less-toxic substances (Fig.3). Catalysis is the process in which the rate of a chemical reaction is increased by means of a chemical substance known as a catalyst. Unlike other reagents a catalyst is not consumed during the chemical reaction (Apostolescu et al., 2006). Thus, the catalyst may participate in multiple chemical transformations, although in practice catalysts are secondary processes. There are millions of cars on the road that are potential sources of air pollution. In a major effort to reduce

vehicle emissions, car makers have developed an interesting device called a catalytic converter, which treats the exhaust before it leaves the car and removes a lot of the pollution (Hizbullah et al., 2004). It is the most effective after treatment

process for reducing engine emission. Catalytic converter is generally called as

three way catalytic converter because it promotes in reduction of HC, CO and NOx.

It consists of steel container of honeycomb structure inside which contains porous ceramic structure through which the gas flows.

It consists of small embedded partials of catalytic materials that promote oxidation reaction in exhaust gas.

Catalytic converter uses alumina as base material because it can withstand high temperature.

2.4. Catalytic Materials Many types of material often used as catalyst in the recent years. Proton acids are probably the

Table 1 Physical method for preparation of nanoparticles Method Advantages Limitations

Evaporation condensation method High purity powder The limitation of mass production

Plasma heating method High melting point and low vapour pressure materials (W, Al2O3, SiO2, C) Very expensive equipment

CO2 laser method Low vapor pressure materials Difficult for the application of Metal nano powder

Mechanical alloy method Nano powder of metal alloy Agglomeration & introduction of impurity

Pulsed wire evaporation wire Metal wire source Low energy consumption & Friendly environment

Table 2 Chemical method for preparation of nanoparticles Method Advantages Limitations

Chemical Vapor Deposition (CVD)

Mass production facility Impurity contamination & the danger of chemical materials Liquid phase reduction method Hydro-thermal synthesis Sol-gel method

Table 3 Nanoparticles-Categories and Applications

Nanostructure Example Material or Application

Nanotubes Carbon, (fullerenes)

Nanowires Metals, semiconductors, oxides

Nanocrystals, quantum dots

Insulators, semiconductors, metals

Figure 1 Schematic representation of CVD

Figure 3 Over view of catalytic converter

Figure 2 Chemical vapor deposition set up

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most widely used catalysts, especially for the many reactions involving water, including hydrolyses and its reverse. Multifunctional solids often are catalytically active, e.g. zeolites, alumina, certain forms of graphitic carbon etc.

Transition metals such as platinum, palladium, rhodium, iron, silver are often used to catalyses redox Reactions (Table 3 and Table 4), (Jacob Klimstra and Nederlandse Gasunie, 1989).

2.5. General principles of catalysis Catalysts generally react with one or more reactants to form intermediate substances that subsequently give the final reaction product, in the process regenerating the catalyst. The following is a typical reaction, where C represents the catalyst, X and Y are reactants, and Z is the product of the reaction of X and Y:

X + C → XC (1) Y + XC → XYC (2) XYC → CZ (3) CZ → C + Z (4)

Although the catalyst is consumed by reaction 1, it is subsequently produced by reaction 4, thus the overall reaction is listed below:

X + Y → Z As a catalyst is regenerated in a reaction, often only small amounts are needed to increase the rate of the reaction. In practice, however, catalysts are sometimes consumed in secondary processes.

2.6. Catalysis and reaction Catalyst is used serves for two purposes,

1. Enhances the reaction rate 2. Direct the reactants to specified product

General potential energy diagram showing the effect of a catalyst in the chemical reaction of X + Y to give Z. Due to presence of the catalyst reaction occurs in different pathway which results in lower activation energy. The final result and the overall thermodynamics are the same. Potential energy diagram is shown in Fig.4. Rate of reaction(R) is inversely proportional to exponential of the activation energy. Let k be the reaction rate constant, Ca,

Cb be the concentration at point of time of reactant molecules and x, y be the reaction order. Thus rate of reaction is represented as

Rate of reaction R =kCaxCby Catalysts work by providing an (alternative)

mechanism involving a different transition state and lower activation energy. The effect is due to the molecular collisions have the energy needed to reach the transition state. Catalysts do not change the favorableness of a reaction: they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are both affected.

2.7. Mechanism of catalytic reaction Mechanism of catalyst was carried by chemisorptions which is the type of adsorption where the molecules adhere to the surface of catalyst through the formation of chemical bond. Strength of the adsorption in the order of, O2>C2H2>CO>H2>CO>N2. Variation of chemisorptions among metals is represented as follows, Au>Cu>Pd>Pt>Rh>Co>Ni>Ag>Mn>Fe> Mo>W>Nb>Ta>Ti Based on this it is clearly represented that Au can readily react with metal and can act as efficient catalyst for most of the reaction (Fig.5). At the same time Ti has low chemisorptions thus it cannot be used as catalyst.

Table 4 Pollutants and its characteristics Pollutant Characteristics

Nitrogen oxides It is an reddish-brown toxic gas emitted from high temperature combustion Carbon monoxide Colourless, odorless, non-irritating but very poisonous gas.

Particulate matter These are tiny particles of solid or liquid suspended in a gas which cause health hazards such as heart disease, altered lung function

Sulfur oxides Generally SO2 reacts with atmosphere to form H2SO4, and thus acid rain

Figure 4 Diagram of Potential Energy

Figure 5 Model of catalytic reaction

Chemisorption: Chemisorption is a sub-class of adsorption, driven by a chemical reaction occurring at the exposed surface. A new chemical species is generated at the adsorbant surface (e.g. corrosion, metallic oxidation).

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2.8. Steps for Dispersion of Particles on to the Catalytic Converter

1. Capillary Impregnation - It is the process by which adsorption of nano particles on to the surface of catalyst converter when the particles are dispersed in the liquid medium. The adsorption of particles on to catalytic converter takes place unto saturation limit. Further drying and calcinations at high temperature results in fixing of particles on to catalytic converter.

2. Drying - Drying process take place at 110oc for the matter of one hour in the closed furnace.

3. Calcinations - Calcinations process take place at 550oc for the matter of five hour in the closed furnace. Thus results in fixing of particles on to the catalytic converter.

2.9. Types of Catalyst Generally catalyst can be classified into two types Homogeneous catalyst Heterogeneous catalyst Electro catalyst

Homogeneous Catalyst - Homogeneous catalysts are those in which reactant and product are of same phase. One example of homogeneous catalysis involves the influence of H+ on the etherification of esters, e.g. methyl acetate from acetic acid and methanol.

Heterogeneous Catalyst - Heterogeneous catalysts are those in which reactants and product are of different phase. For example, in the Haber process, finely divided iron serves as a catalyst for the synthesis of ammonia from nitrogen and

hydrogen. Electro Catalyst - In the context of

electrochemistry, specifically in fuel cell engineering, various metal-containing catalysts are used to enhance the rates of the half reactions that comprise the fuel cell. One common type of fuel cell electro catalyst is based upon nanoparticles of platinum that are supported on slightly larger carbon particles when this platinum electro catalyst is in contact with one of the electrodes in a fuel cell.

2.10. Types of Catalytic Converter The types of converter are listed below Monolithic Converter Two way converter Three way converter Dual bed converter

Three-Way Catalytic Converter - Three-way catalytic converter is widely used in the automobile industries. The three-way catalytic converter is scheduled to perform three simultaneous tasks, a) nano palladium: reduction catalyst, b) nano rhodium: oxidation catalyst, and c) the control system (Fig.6 and Fig.7).

2.10.1. The Reduction Catalyst The reduction catalyst is the first stage of the catalytic converter. It uses Nano palladium to help reduce the nitrogen oxide emissions. When such molecules come in contact with the

Figure 6 Three way catalytic converter

Figure 7 Construction of 3 way converter

PROPERTIES OF CATALYST Surface area and pore size - High surface area results in maximum dispersion of catalytic compound. Smaller pores

size result in increase in catalytic activity. Particle size distribution - Thus more number of particles dispersed result in increase in catalytic activity. Thus huge

number of particle distribution obviously increases the catalytic action. Wash coat thickness - Optical microscope study is often used to obtain wash coat thickness directly. The space

between wash coat and monolith gives the wash coat thickness measurement. Thus wash coat formed must be as small as possible.

Adhesion - Common method for the measure of the adhesion between wash coat monotyth is passing jet of air that simulates velocity used to measure adhesion between substrate and catalyst. There must be sufficient adhesion between molecules for higher catalytic activity.

Calcination: Calcination (calcining) is a thermal treatment process in presence of air applied to ores and other solid materials to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials.

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catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2.

2.10.2. The Oxidization Catalyst The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a nano rhodium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas.

2.10.3. The Control System The third stage is a control system that monitors the exhaust stream, and uses this information to control the fuel injection system. There is a heated oxygen sensor (also called a Lambda Sensor) mounted upstream of the catalytic converter (Fig.8), meaning it is closer to the engine than the converter (Stanley L.Genslak, 1972). This sensor tells the EEC-V PCM how much oxygen is in the exhaust. The EEC-V can increase or decrease the amount of oxygen in the exhaust by adjusting the air-to-fuel ratio. This control scheme allows the EEC-V to ensure that the engine is running at close to the stoichiometric point, while also making sure that there is enough oxygen in the exhaust to allow the oxidization catalyst to burn the unburned hydrocarbons and carbon monoxide (Kureti et al., 2003). The rear most Lambda sensors are not used to adjust the engine mixture but simply to identify the performance of the Catalytic Converters. In ideal conditions they should show a constant output indicating that the Cats are working as intended. Ripple which mirrors the output of the pre-CAT sensors indicates Cats that are starting to fail.

2.11. How three way Catalytic Converters Reduce Pollution? Most modern cars are equipped with three-way catalytic converters. "Three-way" refers to the three regulated emissions it helps to reduce - carbon monoxide, un-burnt hydrocarbons and

nitrogen oxide molecules. The converter uses two different types of catalysts, a reduction catalyst and an oxidization catalyst (Steve Seldlitz, 1974). Both types consist of a ceramic structure coated with a metal catalyst, we used nano palladium and nano rhodium. The idea is to create a structure that exposes the maximum surface area of the catalyst to the exhaust stream, while also minimizing the amount of catalyst required. There are three main types of structures used in catalytic converters - ceramic honeycomb, metal plate and ceramic beads Reduction of nitrogen oxides to nitrogen and oxygen

2NOx → xO2 + N2 Oxidation of carbon monoxide to carbon dioxide

2CO + O2 → 2CO2 Oxidation of un-burnt hydrocarbons (HC) to carbon dioxide and water

CxH2x + 2xO2 → xCO2 + 2xH2O

2.12. Applications of Catalytic Converter Petrol engine emission control Diesel engine emission control Food processing industries Chemical manufacturing industries Gas turbines

3. RESULTS AND DISCUSSIONS 3.1. NOx Reduction The variations of NOx value with brake power value and at different conditions are shown in Fig.9. The NOx value keeps on decreasing on introduction of catalytic converter and finally reaches the minimum value on using nano catalytic converter. Thus at no load condition there is about 33.33% decrease in NOx value and at peak load condition there is about 54.3 % decrease in NOx value. This is due to the fact that NOx undergoes catalytic reaction with catalytic particles such as Nano palladium, Nano rhodium, results in the production nitrogen and oxygen as the end product. Thus there is steady decrease in NOx value with the introduction of the Nano catalytic converter.

3.2. HC Reduction

Figure 8 Lambda sensor

Figure 9 Variation of Nox reduction with brake power

Stoichiometric point: The stoichiometric point is a term commonly used to describe a particular fuel/air ratio in a combustion engine.

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The variations of HC value with brake power value and at different conditions are shown in Fig.10. The HC value keeps on decreasing on introduction of catalytic converter and finally reaches the minimum value on using Nano

catalytic converter. Thus at no load condition there is about 72.1% decrease in HC value and at peak load condition there is about 68.8 % decrease in HC value. This is due to the fact that HC undergoes catalytic reaction with catalytic particles such as nano palladium, nano rhodium results in the production water and oxygen as the end product. Thus there is steady decrease in HC value with the introduction of the nano catalytic converter.

3.3. CO Reduction The variations of CO value with brake power value and at different conditions are shown in the Fig.11. The CO value keeps on decreasing on introduction of catalytic converter and finally reaches the minimum value on Nano catalytic converter. At no load condition there is about 60% decrease in CO value and at peak load condition there is about 40 % decrease in CO value. This is due to the fact that CO undergoes catalytic reaction with catalytic particles such as nano palladium, nano rhodium results in the production carbon di oxide and oxygen as the end product. Thus there is steady decrease in CO value with the introduction of the nano catalytic converter.

4. CONCLUSION Nano palladium and nano rhodium particles (90-100 nm) were synthesized and characterized by using chemical vapor deposition method. The nano catalytic converter efficiently decreases the emission of NOx, HC and CO components.

SUMMARY OF RESEARCH 1. A detailed work has been done on synthesis and characterization of nano palladium and nano rhodium by using chemical

vapor deposition. 2. The particles are found to be in dispersed state with the particle size ranging from 90-100 nm. 3. The engine exhaust test has been carried out. 4. By using the nano catalytic converter 33.33% decrease in NOx value at no load condition and about 54.3 % decrease in

NOx value at peak load condition. 5. Also HC value is decreasing 72.1% at no load condition and 68.8% at peak load condition. 6. At no load condition 60% decrease in CO value and at peak load condition 40% decrease in CO value. 7. Using nano catalytic converter, the pollution level was reduced successfully. FUTURE ISSUES 1. What other chemical vapor deposition based nanoparticles employing in pollution control? 2. Which method of preparation is efficient to make nano palladium and nano rhodium particles are more potent in pollution

control? 3. Is nano catalytic converter applicable to control pollution according to cost factor?

DISCLOSURE STATEMENT There is no conflict of interest and financial support for the proposed research work.

ACKNOWLEDGMENTS We thank the principal, professors and lecturers those who are all given enormous support to our research work. We extend a special thanks to our friends and technicians in the department of physics.

Figure 10 Variation of HC reduction with brake power

Figure 11 Variation of CO reduction with brake power

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3. Jacob Klimstra and Nederlandse Gasunie NV. Carburetors for Gaseous Fuels-On Air-to-Fuel Ratio, Homogeneity and Flow Restriction, SAE paper, No.892141, 1989

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5. Ketteler G, Ranke W, Schl R. Potassium-Promoted Iron Oxide Model Catalyst Films for the Dehydrogenation of ethyl benzene: An Example for Complex Model Systems. J. Catal., 2002, 212(1), 104–111

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