The important of controlling the sources of air pollution especially in the large cities like Tehran in which 60% of its air pollution contributes to the automobile internal combustion engines, is clear to every one.
The aim of this project is to present a strategy for selecting a catalysts suitable to environment, technical and economic possibilities, and the culture of the society. In this project, having studied the sources of air pollutions, the combustion in the engine motors and the important reactions occur on the surface of the catalyst convertors is mentioned.
Then, different catalyst convertors especially three–way ones, effective factors on their performance, the way of controlling them and subjects such as light–off are discussed.
Also, design and manufacturing of the catalyst convertor main components including substrate (ceramic or metallic quality), wash coat and the catalytic phase are the important parts of this research. Finally having referred to some outstanding manufacturing methods, the following results are described:
A) The closed–coupled catalyst system is the selected one, which is suitable to the country conditions environmentally and culturally.
B) Formulations are suggested in this research in which palladium is used to oxidize hydrocarbons and carbon monoxide, and rhodium to reduce nitrogen oxides mainly.
C) Comparing two kinds of catalysts, one with metallic substrate and the other with ceramic one, the metallic is considered more suitable for the country.
D) The mixture of cerium–zirconium mono phase as a source of oxygen storage (preservation), is suggested in catalyst formulation.