Oxidation catalyst
As the first generation catalyst, Pt and Pd oxidation catalysts are used abroad. However, such catalysts can only control the emissions of carbon monoxide and hydrocarbons, so they are called/two way zero catalysts. Since the 1980s, the United States federal government has raised the emission standard of NOX for vehicles, so that such catalysts cannot meet the standard and are gradually eliminated.
Three way catalyst
Phase I
As the emission standard of NOX has been improved, Pt and Rh catalysts have emerged as the times require. This catalyst can simultaneously purify carbon monoxide, hydrocarbons and oxides of nitrogen, so it is called three-way zero catalyst This is the research of/three-way 0 catalyst. However, this catalyst requires a large number of precious metals such as Pt and Rh; It is expensive and prone to lead poisoning. Therefore, it is not suitable for vehicles using leaded gasoline.
Phase II:
Pt and Rh are partially replaced by Pd to reduce the cost of catalyst. Prepare/three-way 0 catalyst with Pt, Rh, Pd as the main body. It can purify CO, HC and NO at the same time. Its advantages are high activity, good purification effect, long life, but high cost. It is widely used abroad;
The third stage:
All palladium catalyst. The utility model has the advantages of simultaneous purification of CO, HC and NOX, low cost, high temperature thermal stability and fast light off characteristics.
Only by accurately controlling the air-fuel ratio within a narrow window (generally 14.7 ± 0.25) near the theoretical air-fuel ratio can the three pollutants be purified simultaneously.
Post time: Nov-18-2022