Catalyst for selective catalytic reduction of ammonia to remove NOx and preparation method thereof

Abstract

The invention discloses a preparation method of a catalyst for NOx removal based on ammonia selective catalytic reduction. The preparation method includes the steps of (1), subjecting a molecular sieve and a salt solution containing one or multiple metal cations to cation exchange by an ion exchange method; (2), after the ion exchange, washing the molecular sieve by deionized water, drying the molecular sieve at the temperature of 50-200 DEG C, and calcining the same at the temperature of 200-600 DEG C so as to achieve stable binding of the cations exchanged into the molecular sieve; (3), dispersing the molecular sieve processed in the step (2) in water, adding in a certain proportion of hollow aluminum oxide pellet powder according to the mass ratio of the molecular sieve to the hollow aluminum oxide pellet powder 2:1-15:1, adding in binders and thickeners after full dispersing, and coating the solution to a cordierite monolith honeycomb carrier to form a catalyst coating tens of micrometers in thickness on walls of pores of the honeycomb carrier. With the molecular sieve loaded, the catalyst prepared by the method has the advantages of high high-temperature activity and hydrothermal stability.

Description

technical field [0001] The invention belongs to the technical field of tail gas denitrification catalysts, in particular, the invention relates to a molecular sieve-loaded catalyst used for ammonia selective catalytic reduction to remove NOx and a preparation method thereof. Background technique [0002] Diesel vehicle engine exhaust contains harmful gases such as hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM). The exhaust itself has a certain temperature and first passes through a direct oxidation catalyst (DOC). Finally, hydrocarbons and carbon monoxide are oxidized into harmless gases such as carbon dioxide and water, nitrogen oxides and particulate matter cannot be converted, and then enter the selective catalytic reduction denitrification catalyst (SCR catalyst), and urea is injected between the two catalysts Solution, urea is decomposed into ammonia and carbon dioxide, wherein ammonia reacts with nitrogen oxides under the ac...

AI Technical Summary

Problems solved by technology

The disadvantage of this catalyst is that the catalyst has a narrow operating temperature range and poor hydrothermal stability. In actual work, due to the presence of water in the exhaust gas of diesel engines, copper and iron are easily lost in the pores of the molecular sieve, and the catalytic activity decreases rapidly.

Images