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 selective catalytic reduction of ammonia to remove NOx, which includes: (1) cation exchange of molecular sieves with salt solutions of one or more metal cations through an ion exchange method; (2) cation exchange After the exchange, the molecular sieve is washed with deionized water, then dried at 50-200°C, and then calcined at 200-600°C, so that the cations exchanged into the molecular sieve are stably combined; (3) the step (3) 2) The treated molecular sieve is dispersed in water, and then mixed into a certain proportion of hollow alumina pellet powder. The mass ratio of the molecular sieve to the hollow alumina pellet powder is from 2:1 to 15:1. After being fully dispersed, Add a binder and thickener, and then coat it on the cordierite honeycomb carrier to form a catalyst coating with a thickness of tens of microns on the walls of the fine pores of the honeycomb carrier. The catalyst prepared by the method of the present invention is supported by molecular sieves and has 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.

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