Modified cha type molecular sieve and its preparation method, application

Abstract

This application relates to modified CHA type molecular sieve and its preparation method and application, especially its application in diesel vehicle exhaust treatment, and belongs to the field of catalytic materials. The molar ratio of silica and alumina in the modified CHA molecular sieve is 24.5~36; the pore volume of the modified CHA molecular sieve is not less than 0.32cm 3 / g; the crystallinity of the modified CHA molecular sieve is reduced by no more than 5% compared to the H-CHA molecular sieve before modification. The initial CHA molecular sieve is subjected to ammonium ion exchange and first roasting to obtain the H-CHA molecular sieve before modification. CHA molecular sieve is then subjected to acid treatment and alkali treatment to obtain a modified CHA molecular sieve. The modified copper-containing CHA molecular sieve prepared by copper exchange with the modified CHA-type molecular sieve has high crystallinity, thereby increasing the service life of the modified copper-containing CHA-type molecular sieve as a catalyst in the selective reduction of ammonia; modified copper-containing CHA Type molecular sieve has a large pore volume and can accommodate more substances that can cause catalyst pore clogging and pore volume reduction, thus extending the catalyst life.

Description

technical field [0001] The application relates to a modified CHA molecular sieve and its preparation method and application, especially the application in the treatment of diesel vehicle tail gas, which belongs to the field of catalytic materials. Background technique [0002] Nitrogen oxides (NOx) are serious air pollutants, and diesel vehicle exhaust emissions are one of the main sources of NOx. In order to meet the escalating emission standards, the treatment of diesel vehicle exhaust has become increasingly important and urgent. Selective catalytic reduction of ammonia (NH 3 -SCR) is currently a widely used after-treatment strategy for diesel vehicle exhaust NOx. [0003] Copper-exchanged Cu-CHA molecular sieve is currently recognized as the most effective ammonia selective catalytic reduction (NH for short) for diesel vehicle exhaust treatment. 3 -SCR) catalyst. From the perspective of economy and convenience, diesel vehicle exhaust treatment NH 3 -The SCR process ...

AI Technical Summary

Problems solved by technology

The above various such as (NH 4 ) 2 SO 4 or NH 4 HSO 4 and CuSO 4 and other sulfur-containing compounds, along with NH 3 - The use of SCR catalyst gradually accumulates in the pores of Cu-CHA molecular sieve, reducing its pore volume, covering its acid sites, hindering the contact of reactants with active centers, and finally leading to catalyst deactivation

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