CO, HC, NOx, PM are the main toxic substances polluting the air in motor vehicle exhaust. Motor vehicle exhaust has a complex composition, containing carbon monoxide, unburned hydrocarbons, nitrogen oxides, lead, sulfur dioxide and other harmful substances. In the automobile exhaust catalyst, the specific poisonous by-products in the automobile exhaust can undergo a chemical reaction under the action of the catalyst to be converted into safe or small amounts of poisonous substances, such as oxygen, nitrogen, water vapor and carbon dioxide.
Alfa Chemistry Catalysts use complex science to create innovative catalysts and new products to drastically reduce vehicle emissions and achieve future clean technologies.
Including precious metals, non-precious metals and rare earth doped catalysts, etc., play a major catalytic role.
It is mainly composed of precious metals such as Pt, Rh and Pd, which has good catalytic effect, but the cost is relatively high.
Figure 1. TEM images of Pt grains of catalysts 
Including perovskite-type oxides, common metal (Cu, etc.) catalysts, the cost is lower, but the catalytic performance is not as good as noble metal catalysts.
Rare earth doped precious metal catalysts to reduce the amounts of precious metals and reduce costs, while maintaining a better catalytic effect.
It can provide an effective surface and suitable pore structure, make the catalyst obtain a certain mechanical strength, and improve the thermal stability of the catalyst. The honeycomb ceramic carrier is currently the most widely used.
Integral carrier: honeycomb ceramic carriers mainly include cocoonite, mullite, pyroxene, magnesium silicate, etc. Among them, cocoonite honeycomb ceramic carrier (main component: 2MgO.Al2O3.SiO2) has the best performance.
Figure 2. SEM images for cordierite monolith (a), washcoated monolith (b) and after Ni deposition (c) at different magnifications.
Granular carrier: The catalyst carrier mainly used in the early days was mainly composed of small alumina particles with a diameter of 3-4 mm. Its pressure drop is large, which affects the working efficiency of the engine, and it has been gradually replaced by the honeycomb ceramic carrier.
Integral carrier: metal alloy carrier mainly includes: Ni-Cr, Fe-Cr-Al, Fe-Mo-W, etc. The metal carrier has poor high temperature oxidation resistance and needs to be modified by doping with rare earth metals.
Attaching to the surface of the carrier can increase the specific surface area of the carrier, and γ-Al2O3 is generally used.
The coating is also called the "second carrier", and usually uses γ-Al2O3 with a larger surface area. It is unstable at high temperature and will undergo phase change to reduce the surface area. Rare earth oxides need to be added to improve thermal stability.
Additives such as some rare earth oxides, can strengthen the thermal stability of the catalyst, thereby improving its performance.
Mainly rare earth metal oxides such as CeO2, La2O3, etc., and solid solution of cerium and zirconium.