CATALYSTS AND CONVERTERS

A catalyst is anything that assists a chemical process to be improved (usually by reducing the time taken to effect the change) without itself being significantly altered.

In combustion conditions many additives serve such a purpose with platinum being one of the most important. It has the ability, to speed up the oxidation of hydrocarbon and carbon monoxide. Introducing it, or other elements such as tin, copper, chromium and many others, into the combustion chamber can cause a stabilizing (i.e. control of the erratic burning which occurs during very high-speed combustion processes (in diesel engines it is a true explosion). Water spray, into a inductor manifold, or emulsifying it with diesel fuel, serves also as a catalyst since its molecular structure is not altered (i.e. it remains as H2O but becomes evaporated to superheated steam) during the combustion of the fuel. A study, with measuring sensors of the cylinder pressures for various piston positions during the engine’s cycle of operations always reveals the influence of a catalyst by the elimination of erratic changes of cylinder pressure. A simple and much less costly, approach is to measure the output power from an engine or vehicle road wheels by means of a dynamometer, before and after the catalyst is used.

Catalytic Mufflers – not unlike the external shape of an exhaust system silencer – use a grid of fine wire or tubes (made from platinum) within the muffler such that the hot exhaust gases heat the grid. The Flow conditions cause the hydrocarbons and carbon monoxide to collie with the oxygen and hence, at such high temperatures combustion takes place. This normally takes place but is dramatically improved by the use of the platinum grid.

It is, however, found that, with leaded petrol, the oxides of the tetra ethyl lead seriously affect and eventually rain the platinum grid. Such catalytic converters should only be used with lead- free fuels. The purpose of all catalysts is to enable further reduction of unburned hydrocarbons to produce steam and carbon dioxide as well as convert the carbon monoxide to carbon dioxide. When this occurs on the engine combustion chamber, the resulting increase in heat energy causes an increase in engine power. The unfortunate consequence of the catalytic converter is that it wastes the gain in heat energy to the air ship stream crossing the muffler. Its prime purpose is to reduce unacceptable levels of exhaust emissions (hydrocarbons and carbon monoxide) to acceptable levels, to comply with particular regulations.