Three-way (three-way) catalytic converter is a special catalytic device in the exhaust system of engine, which can oxidize hydrocarbon (HC) and carbon monoxide (CO) in the exhaust, it also recovers nitrogen oxide (NOx) from exhaust into harmless nitrogen and oxygen. The catalytic converter shall have a large surface area to ensure that the exhaust gas meets a long time with the active catalytic material (primarily platinum, rhodium, palladium, or rare earth active material) on the surface of the converter to meet the touch, generally, honeycomb ceramic or metal mesh carrier is used, and catalyst is coated on the surface. The oxidation reaction of hydrocarbons (HC) and carbon monoxide (CO-RRB- with trace amounts of oxygen in the exhaust gas is more likely to occur with the help of a catalyst, i.e. the temperature at which the reaction takes place and the concentration of the reactants are greatly reduced. So catalytic converters can oxidize more than 90 percent of hydrocarbons (HC) and carbon monoxide (CO) into harmless water vapor and oxygen. When the oxygen concentration in the exhaust is very low, NOx will react with HC and so on, reverting to harmless oxygen and nitrogen. This is reflected in the conditions in order to be able to achieve more than 90% of the conversion power.

  Catalytic power is affected by a number of factors, the main ones being the concentration of oxygen in the exhaust (that is, the air-fuel ratio of the mixture entering the cylinder) and the Catalytic converter temperature. In addition, elements such as lead and sulfur can have a negative effect on Catalytic converter because they may form new crystalline structures with the effect of the catalytic active material or deposit on the catalytic material, then damage the catalytic material surface activity, this is the so-called catalyst poisoning, is the more serious physical phenomenon that affects the life of the catalyst. Therefore, the use of Catalytic converter is conditional on the unleaded gasoline. Sulfur has a great effect on the lifetime of rare earth catalysts. Three-way catalytic converter is an important external purification equipment installed in automobile exhaust system, it can change harmful gases such as CO, HC and NOx from automobile exhaust into harmless carbon dioxide, water and nitrogen by oxidation and recovery effect. Because this kind of catalyst can be simultaneously in the exhaust gas of the work of the first harmful substances into harmless substances, it is called ternary.

  The working principle of the three-way catalyst is: when the high-temperature automobile exhaust passes through the purification equipment, the purifying agent in the three-way catalyst will enhance the activity of CO, HC and NOx, at high temperature, CO is oxidized to five-color, non-toxic carbon dioxide gas, and HC compounds are oxidized to water (H20) and carbon dioxide Nox reverts to nitrogen and oxygen. Three kinds of harmful gas into harmless gas, so that automobile exhaust can be purified.