In these reactions the pollutants are being converted to carbon dioxide, water and nitrogen which are naturally present in the air. These pollutions do react on their own, but catalysts make them go faster. Catalysts are present in catalytic converters. A lean burn engine uses an oxidation catalyst which removes CO and Hydrocarbons, converting them to carbon dioxide and water. This catalyst system does not remove nitrogen oxides. Catalytic converters can be fitted to ordinary cars; instead of an oxidation catalyst, a three-way catalyst system is needed, which catalyses oxides, CO, hydrocarbons, and nitrogen oxides. This catalyst only works if the air-petrol mixture is controlled so that it is exactly balanced. The reduction catalyst is made from platinum and rhobium and it reduces NOx emissions.
2NO(g) N2(g) + O2(g)
or
2NO2 N2(g) + 2O2(g)
The oxidation catalyst
2CO (g) + O2(g) 2CO2(g) .
Types of Catalysts
If the reactants and catalysts are in the same physical state, for example they are both in an aqueous solution, then the reaction is said to involve homogenous catalysis. In many cases, the catalyst and reactants are in a different physical state. This kind of reaction is said to have involved heterogenous catalysis.
How Catalysts Work
All chemical reactions require bond breaking, and bond making. Breaking the bonds requires energy known as the activation energy. The energy supplied must be higher than the activation energy, in order for the reaction to occur.
Catalysts speed up chemical reactions by providing an alternative pathway for breaking and remaking bonds.
Catalyst poisoning
Catalyst poisoning occurs when other gases are absorbed more readily onto the catalyst than the reactants. This prevents the reactants from doing so. Catalyst poisons in cars include lead and sulphur.
What problems don’t have solutions yet? And how scientists are trying to tackle these issues?
We draw the difference between local and global effects because all fuels have different pollution profiles and an individual, for example such as a mayor, may be only interested in curbing local pollutants. We feel that both are important but the minimisation of greenhouse gases is vital, and green, renewable fuels usually emit low local pollution levels anyway.
Summary
The gases given out when burning fuels in vehicles are very unsafe and dangerous for our environment. But these can be simply reduced by using the catalytic converters. Catalysts speed up chemical reactions by providing an alternative pathway for breaking and remaking bonds. But it still doesn’t reduce the pollution in large amount.
Bibliography
http://www.envocare.co.uk/motor_vehicle_pollution.htm
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