ABSTRACT

Nowadays, controlling emissions are not simply a case of engine design and engine management. Exhaust gas after-treatment systems play an important role, as current and future automobile emission regulations become more stringent. The most effective after treatment for reducing engine emission is the catalytic converter found on most automobiles.Catalytic converters typically consist of a ceramic or metal honeycombed monolith substrate that carries precious metal catalysts. The coated substrate is wrapped in an in tumescent mat that expands when heated, securing and insulating the substrate which is packaged in a stainless steel shell and fitted into the engine exhaust system.As exhaust gases pass over the catalysts, they promote chemical reactions that convert pollutants into harmless gases and water. Hydrocarbons (HC) combine with oxygen (O2) to become carbon dioxide (CO2); oxides of nitrogen (NO, NO2) react with carbon monoxide (CO) to produce nitrogen (N2) and carbon dioxide (CO2); and with hydrogen (H2) to produce nitrogen (N2) and water vapour (H2O).There are several types of problems associated with precious metal based catalytic converter. These factors encourage for the possible application of non noble metal based material. So we decided to use copper as a catalyst, which may by proper implementation be able to show the desired activity and can also offer better durability characteristics due to its poison resistant nature.

INTRODUCTION

To meet the green vehicle concept and make our vehicle better environment friendly we used an innovative concept in the catalytic converter. Our vehicle emission standard is as per BSIII. Bharat stage emission standards are emission standards instituted by Government of India to regulate the output of air pollutants from internal combustion engine equipment, including motor vehicles. The standards and the timeline for implementation are set by the Central Pollution Control Board under the Ministry of Environment & Forests.The catalytic oxidation of carbon monoxide is an important reaction both commercially and scientifically. Copper-manganese oxides in the form of hopcalite have formed a cheap and accessible carbon monoxide abatement catalyst for the last 80 years.

Exhaust gases

Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends diesel fuel, fuel oil, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume. t is a major component of motor vehicle emissions (and from stationary internal combustion engines), which can also include:

• Crankcase blow-by• Evaporation of unused gasoline

Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities.

Catalytic converters

In chemistry, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected. Catalysts participate in the reactions, but are neither reactants nor products of the reaction. A catalytic converter reduces temperature at which CO & HC convert into CO2 and H2O. Generally catalytic converters uses platinum group of noble metals.

Literature SurveyIn this chapter, many issues relating to the oxidation of carbon monoxide over metal oxide catalysts, which have arisen in literature over the past century, are discussed. Special attention has been given to the potential applications of these catalysts, preparation of active species and promotion of catalysis in these systems. Thelimitations of using metal oxide based catalytic systems are also recognised and explored with the aim of introducing and giving an understanding of the experimental results contained in later chapters.

Exhaust Gases

Carbon MonoxideCO is a colourless, odourless, tasteless but extremely poisonous gas. It is slightly soluble in water and bums with a characteristic blue flame to produce carbon dioxide. It is a useful reducing agent, removing oxygen from many compounds and is used extensively in the reduction of metals, e.g. in a blast furnace to remove iron from its ore.

Carbon monoxide is formed by the combustion of carbon in oxygen at high temperatures but can also be formed from the decomposition of carbon dioxide at excessive temperatures (>2000°C). It is often present in the exhaust fumes of internal combustion engines but can also be generated in coal stoves, furnaces and gas heaters that do not get enough air. Known as the “silent killer”, carbon monoxide is a very poisonous gas. It is especially dangerous to humans because it is not easily detected by our senses. Breathing air that contains even small amounts of CO; as little as 0.1% carbon monoxide by volume, can prove fatal. [2] A concentration of only 1% is enough to cause death in only a few minutes. When CO is inhaled it binds irreversibly to the protein haemoglobin in red blood cells, disabling the oxygen transfer mechanism in the body. This deactivation mechanism occurs readily as CO is attracted to the haemoglobin about 210 times as strongly as is oxygen. As a result, it takes the place of oxygen in the blood causing oxygen starvation throughout the body. Early signs of CO poisoning can often be mistaken for flu due to the similarity of their symptoms; headache, breath shortness, dizziness, disorientation, nausea and fainting. At high levels, vomiting, coma and eventually brain damage and death will occur. [3-5] The depletion of dangerous levels of CO from the air around us is obviously even more important in confined spaces.

Oxidation of carbon monoxide

CO + l/202 co2

The oxidation of carbon monoxide in an oxygen rich atmosphere occurs readily at high T but will only occur at lower temperatures in the presence of certain materials. The reaction is thermodynamically irreversible at room temperature, with AG° for the reaction being equal to -256.9KJ/mole. The major contribution to AG° is the high negative value of AH° = -282.84 KJ/mole. The entropy for the reaction is -86.61 J/K/mol, so the negative value of AG° becomes smaller as temperature is increased.Even at very high temperatures, the equilibrium for the reaction always favours conversion to CO2 .

The poisonous nature of CO has stimulated a large amount of interest in the heterogeneous catalysis field, especially investigations in to contact agents which operate at ambient temperature. [9] Studies in recent years have yielded substantial information on activated adsorption, the concept of active sites, the nature of the active surface and the relationship between lattice instability and catalytic instability. The oxidation of CO has often been used as a catalytic test reaction due to fact that the chemisorption of carbon monoxide is facile and non-dissociative under normal catalytic conditions. The reaction has served to increase the understanding of the redox mechanism of catalytic oxidation, as well as helping to verify the electronic theory of chemisorption on catalysts.

Carbon monoxide oxidation catalysts

The role of a catalyst in a given reaction is to alter the rate of reaction at a given reaction temperature by lowering the activation energy barrier or by providing an alternative reaction route. Varieties of materials have been reported as active for the catalysis of carbon monoxide. Some of the most popular include:

1. Transition metal oxides - Zn, Mn, Cu, Ti, Fe, Ni, Co, Mo2. Precious metal oxides - Ag, Au, Pt, Pd3. Some oxides of the rare earth elements - Ce, Th

Background to carbon monoxide oxidation abatement

In recent years, there has been substantial interest in the oxidation reaction of CO to produce CO2 . Carbon monoxide is a pollutant of industrial and domestic origin with a well publicised history of serious health implications. Reports of long term exposure at even ppm levels have been identified as being very concerning and have prompted the development of methods to reduce exposure levels in many environments. Emissioncontrol using catalytic oxidation has many advantages over adsorption methods in terms of size of equipment, cost and operating simplicity.

Air cleaning in building and in cars

Due to the dangerous nature of CO it is often necessary to remove it from the air around us. In many situations, the polluted air may be rich in water vapour and only be available at room temperature. Any useful catalyst should therefore be water tolerant and operate under ambient conditions Much work carried out in the field has focussed on the removal of CO from vehicle emissions at quite high temperatures. Unfortunately, Hopcalite catalysts are moisture sensitive and deactivate on exposure to water. [10] Hence, it is most desirable to find moisture tolerant alternatives or to incorporate elements of moisture protection in hopcalite-containing systems.

The main emissions after treatment, of an engine are:· Nitrogen gas (N2) - Air is 78% nitrogen gas, and most of this passes right through the car engine.· Carbon dioxide (CO2) - This is one product of combustion. The carbon in the fuel bonds with the oxygen in the air.· Water vapour (H2O) - This is another product of combustion. The hydrogen in the fuel bonds with the oxygen in the air.These emissions are mostly nonthreatening, although carbon dioxide emissions are believed to contribute to global warming. Because the combustion process is never perfect, some smaller amounts of more harmful emissions are also produced in engines they are:

· Carbon monoxide (CO) is a poisonous gas that is colourless and odourless.· Hydrocarbons or volatile organic compounds (VOCs) are a major component of smog produced mostly from evaporated, unburned .fuel.· Nitrogen oxides (NO and NO2, together called NOx) are a contributor to smog and acid rain, which also causes irritation to human mucus membranes.

These pollutants are known to cause global warming, acid rain, smog and respiratory and other health hazards. Therefore, there are laws on emission standards, which limit the amount of each pollutant in the

exhaust gas emitted. Our design work is focused upon the reduction of such emissions by non-noble metal copper as a catalyst in catalytic converter.

PROBLEM STATEMENT

The conventional three-way catalytic converters use precious noble metals such as platinum, palladium and rhodium as catalyst.

Issues:1. Catalysts: Platinum (Pt), Palladium (Pd) or Rhodium (Rh)

a. All are very expensive, have very limited supply sources, and limited future availability.b. Price makes them attractive to steal.

2. Catalysts only work at fairly high Temperatures

Exhaust gas recirculation (EGR)

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. EGR works by re-circulating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust displaces the amount of combustible matter in the cylinder. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates. The exhaust gas, added to the fuel, oxygen, and combustion products, increases the specific heat capacity of the cylinder contents, which lowers the adiabatic flame temperature. In a typical automotive spark-ignited (SI) engine, 5 to 15 percentage of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the requirement of the mixture to sustain a contiguous flame front during the combustion event; excessive EGR in poorly set up applications can cause misfires and partial burns.

Positive Crankcase Ventilation (PCV)

During normal compression stroke, a small amount of gases in the combustion chamber escapes past the piston. Approximately 70% of these "blow by" gases are unburned fuel (HC) that can dilute and contaminate the engine oil, cause corrosion to critical parts, and contribute to sludge build up. At higher engine speeds, blow by gases increase crankcase pressure that can cause oil leakage from sealed engine surfaces.The purpose of the Positive Crankcase Ventilation (PCV) system is to remove these harmful gases from the crankcase before damage occurs and combine them with the engine's normal incoming air/fuel charge.

Catalytic converters

In chemistry, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected. Catalysts participate in the reactions, but are neither reactants nor products of the reaction. A

catalytic converter reduces temperature at which CO & HC convert into CO2 and H2O. Generally catalytic converters uses platinum group of noble metals.