Three-way catalytic converter, also known as "three-way catalytic converter", is an important component that filters harmful components in exhaust gas, and is an important external purification device installed in the automobile exhaust system. That is to filter the three harmful components of CO, SO2 and CxHy compounds in the exhaust gas. Because this catalyst can simultaneously convert the three main harmful substances in the exhaust gas into harmless substances, it is called a three-way catalyst.

The three-way catalytic converter is similar to a muffler, and its outer surface is made of double-layer stainless steel plates. Insulation material----asbestos fiber felt is installed in a double-layer sheet sandwich. The interior is filled with a purifying agent in the middle of the mesh partition. The scavenger consists of a carrier and a catalyst. The carrier is generally made of Al2O3 or SiO2, and its shape has spherical, polygonal and mesh separators. The catalyst adopts rare metal materials such as platinum, rhodium and palladium, and one of them is sprayed on the carrier to form a purifying agent. Usually the honeycomb structure density of the purifier is about 1200 mesh/square inch, which can convert most of the harmful substances in the exhaust gas into harmless substances.

The carrier in the three-way catalyst is usually a ceramic honeycomb carrier. The ceramic honeycomb carrier must first be coated with a silica coating to modify its surface. Since the surface of the ceramic honeycomb carrier coated with silica is very rough, this increases the actual area of ​​the wall by about 7000 times, which greatly increases the active surface and oxygen storage capacity of the three-way catalyst. The outer side of the active layer is coated with Zr Co-catalysts of elements such as , Ce and main catalysts containing precious metals such as rhodium Rh, palladium Pd, platinum Pt, etc.

Because the silica sol has good adhesion properties, the prepared catalyst has the following characteristics: high catalyst crystal retention rate, good catalyst stability, good catalyst coke selectivity, and strong vanadium resistance ability of the catalyst. The nano-silica particles prepared from silica sol have uniform distribution and large specific surface area. Pore ​​volume, pore size and distribution can meet the requirements of supported catalysts. Therefore, silica sol is one of the excellent raw materials for preparing catalyst supports.