Automobile exhaust pollutants mainly include: carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, dust particles (some heavy metal compounds, lead compounds, black smoke and oil fog), odor, and automobile exhaust purification catalysts, the active group is divided into Pd, Pt, Rh; Car parts catalytic converter is generally Co, Mn, Ni, etc., the carrier is generally cordierite honeycomb, but also useful spherical Ai2O3, under the action of the catalyst, some low-priced nitrides and sulfides, convert more high-priced oxides, under the action of water, generate strong acids, such as sulfuric acid, nitric acid, so the acidity of the air increases.