Automobile tail gas cleaning catalyst and its preparation method

Abstract

The invention provides a catalyst used for purifying motor vehicle exhaust, and a preparation method thereof. The catalyst comprises a carrier with one coating or a plurality of coatings; and each coating contains alumina carrying silver and an oxygen storage material carrying platinum / palladium, wherein the silver is impregnated to be carried on the active alumina by a mixed solution of soluble silver salt and citric acid, and the platinum and the palladium are respectively impregnated to be carried on the oxygen storage material by the salt solutions thereof, so that the platinum and the palladium are not carried on the same oxygen storage material, the oxygen storage material is a mixture of cerium oxide and zirconia, the cerium oxide or ceria-zirconia solid solution, the Ag and Pt / Pd are separately carried on different oxide carriers. The preparation method comprises the following steps: (1) preparing the alumina carrying the silver, the oxygen storage material carrying the platinum and the oxygen storage material carrying the palladium; (2) preparing coating slurry; and (3) coating the coating slurry on the catalyst carrier. The catalyst provided by the invention for purifying the motor vehicle exhaust has low cost, good combustion activity and good resistance to aging.

Description

technical field [0001] The invention belongs to the technical field of environmental protection catalysts, in particular to a catalyst for purifying automobile exhaust and a preparation method thereof. Background technique [0002] With the development of the automobile industry, the output of automobiles has increased sharply, and the tail gas emitted by automobiles has become one of the main pollution sources of the atmosphere. CO, Hydrocarbons (HC), NO in automobile exhaust x Such ingredients are extremely harmful to human health and the public environment. In order to eliminate this severe pollution, countries around the world have enacted stricter emission regulations one after another. Therefore, minimizing vehicle exhaust emissions has become a major issue to be solved urgently in the field of global environmental protection. At present, the method of adding an exhaust catalytic converter to an electronically controlled fuel injection system with an oxygen sensor ha...

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Problems solved by technology

Among them, rhodium is used as a common reducing NO x The catalytically active component has the advantages of good light-off activity, good aging resistance, and strong anti-poisoning ability, but due to its resource shortage and high price, the cost of the entire catalyst is relatively high, and Pt or / and Pd without Rh Although the catalyst has the characteristics of strong anti-aging ability and good low-temperature ignition performance, it is not effective for NO x The ability to restore is poor

[0004] In order to reduce costs, people have carried out a lot of research work on the use of non-noble metal catalysts to replace noble metal catalysts. x Poor ability, poor anti-sulfur performance and other shortcomings, at present, the method of reducing or partially replacing precious metals is generally used to prepare catalysts

Due to its good catalytic activity, silver is regarded as an ideal element to partially replace noble metals, but in general, due to the poor selectivity of the active part of silver, the narrow range of active temperature, and the sensitivity to sulfur dioxide, in general, silver is used. As a catalytic active substance to purify automobile exhaust, its actual effect is greatly limited

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