Preparation method of composite copper-based SCR molecular sieve catalyst

Abstract

The invention discloses a preparation method of a composite copper-based SCR molecular sieve catalyst. The method comprises the following steps that S1, N,N,N-trimethyl-1-adamantyl ammonium hydroxideis mixed and stirred with water, aluminum sulfate is added for stirring, the pH value is adjusted through an alkali, silica sol is added for stirring, and an initial gel mixture is obtained; S2, the initial gel mixture is crystallized at the constant temperature, cooled, washed, dried and calcined to obtain a CHA-type molecular sieve; S3, the CHA-type molecular sieve is used as a carrier, manganese nitrate, cerium nitrate, palladium nitrate and copper acetate are impregnated stepwise, and then drying is carried out to obtain the composite copper-based SCR molecular sieve catalyst. According tothe provided preparation method of the composite copper-based SCR molecular sieve catalyst, an obtained product is environmentally friendly and has the effects of low-temperature adsorption and high-temperature and high-efficiency catalysis on NOx, the problem of excessive NOx emission in a cold start stage of a vehicle is effectively solved, and vehicle NOx emission control in all temperature stages is realized.

Description

technical field [0001] The invention relates to the technical field of catalysts, in particular to a method for preparing a composite copper-based SCR molecular sieve catalyst. Background technique [0002] With the progress of the times, my country's control of vehicle exhaust emissions has become more and more stringent. On July 1, 2017, the National V emission standard was fully implemented nationwide. Shortly after the implementation of the National V standard, the National VI standard was quickly put on the agenda. my country will gradually implement it on July 1, 2020 and July 1, 2023 There are two stages of "National VI a" and "National VI b" of the National VI emission standard. Compared with the National V, the emission standard is increased by more than 30%, the nitrogen oxides are reduced by 77%, and the particulate matter is reduced by 67%. The PN (particle number) limit requirements are introduced, and the emission durability and OBD related requirements are tig...

AI Technical Summary

Problems solved by technology

The catalyst is the whole NH 3 -The core and key of the SCR system, and the current SCR catalyst system has some problems, such as metal loss during catalyst preparation and use, causing other environmental pollution problems; or the catalyst has a narrow window of action and cannot meet the requirements of diesel fuel Exhaust emission treatment under different working conditions of vehicles

[0004] with V 2 o 5 -WO 3 / TiO 2 The representative vanadium-based catalyst has problems such as high light-off temperature (250°C), high temperature prone to vanadium loss, high biological toxicity, and poor NOx removal effect

The catalyst with SSZ-13 molecular sieve (belonging to CHA type molecular sieve) as the carrier to support copper element is considered to be the most promising SCR catalyst at present. Good catalytic effect, but poor adsorption effect on NOx below 200°C

For example, in the cold start stage of a car or in a low-speed driving state for a long time, the flue gas temperature is below 200°C, and it is difficult for the copper-based SCR catalyst to function at this time, which may easily lead to excessive NOx emissions

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