The main pollutants in vehicle emissions are hydrocarbons, nitrogen oxides, carbon monoxide and particulate and so on. SCR is the known way with best denitration effect, while the core technology of it is SCR denitration catalyst. Earlier, the denitration catalyst is mainly based on automobile platinum, gold and other precious metal, and later began to use non-precious metal oxide as the main active ingredient. Selective catalytic reduction using ammonia or compound which can decompose into ammonia is the public known way for removing nitrogen oxides from the exhaust gases of lean burn internal combustion engine, which contains active ingredients like titanium dioxide, tungsten trioxide, vanadium pentoxide.

However, when SCR catalyst containing vanadium used for cleaning motor vehicle exhaust, it may lead to toxic vanadium compound going into the air because of the volatility of vanadium under high temperature, thus to cause environmental pollution and personal injury. So, the listed capacity of the car catalyst containing vanadium is low. Therefore, for a long time, researchers and vendors are ongoing committed to provide no vanadium SCR denitration catalyst.

 

Rare earth with the reputation of industrial "vitamins" and "gold" has become an extremely important strategic resource consistent with the metal tungsten. Research indicated that the incorporation of rare earth oxide catalyst can effectively replace the vanadium based catalyst, which exhibits excellent performance. Studies have indicated that some catalyst doping into cerium-zirconium mixed oxide, and also the sulfur, molybdenum, tungsten (in form of tungsten trioxide) compound; in which the ingredients are: 0.02~3% of cerium-zirconium mixed oxide, 5~15%, 0.5~3% of tungsten trioxide (or molybdenum trioxide). This kind of SCR catalyst uses a ceramic flow-through monolith honeycomb wall flow type filter or a ceramic matrix, is particularly suitable for lean burn internal combustion engine exhaust gases to remove nitrogen oxides with the properties of highly activity and anti-aging.