Copper-containing molecular sieve Cu-CHA, catalyst and use thereof

Abstract

The present application discloses a copper-containing molecular sieve Cu-CHA, a catalyst thereof and use thereof in the treatment of diesel vehicle exhaust gas, and belongs to the field of catalytic materials. The copper-containing molecular sieve Cu-CHA consists of zeolite having a CHA framework structure and containing silicon and aluminum elements as well as 1.65-3.05wt% of Cu; the Cu-CHA molecular sieve also comprises 0.5-1.5wt% of boron, and the Cu-CHA molecular sieve has an acid content of 0.25-0.98mmol/g. The Cu-CHA molecular sieve of the present application has an acid density as highas 0.25-0.98mol/g and a Cu content as low as 1.65-3.05wt%. As a catalyst for the selective catalytic reduction of ammonia, the Cu-CHA molecular sieve has excellent storage capacity for NH3 and good low-temperature activity, and the absence of CuOx species in the high-temperature section prevents the reduction of high-temperature activity due to non-selective oxidation of NH3. The Cu-CHA molecularsieve catalyst shows excellent catalytic activity in a wide temperature window, taking into account both low temperature and high temperature activities, and still shows good catalytic activity afterbeing subjected to hydrothermal aging treatment; and after being used in the treatment of diesel vehicle exhaust, the Cu-CHA molecular sieve catalyst has significant performance advantages.

Description

technical field [0001] The application relates to a copper-containing molecular sieve Cu-CHA and its preparation method, a catalyst containing copper-containing molecular sieve Cu-CHA and the application of the catalyst in the treatment of motor vehicle exhaust, especially the application in the treatment of diesel vehicle exhaust, which belongs to the category of catalytic material field. Background technique [0002] Diesel vehicle exhaust includes four main pollutants: carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM) and nitrogen oxides (NOx). Among them, NOx may cause smog, photochemical smog and ozone layer destruction. In 2017, the number of automobiles in my country reached 208 million, of which diesel vehicles accounted for only 9.4%, but the NOx emitted by diesel vehicles was about 70% of the total NOx emitted by automobiles. Selective catalytic reduction of ammonia (NH 3 -SCR) is currently recognized as the mainstream diesel vehicle exhaust NOx t...

AI Technical Summary

Problems solved by technology

[0006] Aiming at the problem of improving low-temperature activity, the strategy in the prior art is to increase the Cu loading of CHA molecular sieves, but this approach often leads to a decrease in the high-temperature activity of the catalyst

This is because, in the case of high loading, some Cu species will be converted into CuOx under high temperature conditions, and these CuOx are not catalytically active for the conversion of NOx, but can catalyze NH 3 The non-selective oxidation of the catalyst leads to a decrease in the activity of the catalyst at high temperature

In addition, under high loading conditions, Cu-CHA molecular sieve catalysts will cause irreversible deactivation of catalytic activity due to the transformation of Cu species during use.

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