Cobalt-doped storage reduction catalyst for purifying nitrogen oxides of lean-burn tail gas

Abstract

The invention relates to a cobalt-doped storage reduction catalyst for catalytic purification of nitrogen oxides of lean-burn tail gas. On the basis of conventional Pt / Ba / Al storage reduction catalysts, by a step-by-step impregnation method, the catalyst successively loads a storage component Ba, transitional metal Co and a noble metal component Pt of nitrogen oxides on alumina or pseudo-boehmite serving as an inorganic porous carrier, and is used to improve the storage reduction performance of the conventional Pt / Ba / Al systems by regulating the contact degree and contact ways of active species and the carrier. The Ba in the catalyst of the series exists mainly in the form of BaCO3, while Co is highly dispersed on the carrier mainly in the forms of Co3O4 and CoAl2O4. The addition of a small amount of the transitional metal Co greatly improves the NOx storage capacity of the catalyst under lean-burn conditions, particularly at intermediate / low temperate (200 to 350 DEG C), and the NOx storage capacity of Pt / Co / Ba / Al is about 1.5 times that of Pt / Ba / Al. Under the condition of simulating the atmosphere turbulence of diesel lean-burn and dense-burn, the cobalt-containing catalyst shows higher NOx removal rate than Pt / Ba / Al in a range between 200 and 400 DEG C.

Description

technical field The invention is applied in the technical field of environmental catalytic purification, and relates to a nitrogen oxide storage and reduction catalyst used in the exhaust gas post-treatment technology of lean-burn engines. technical background Lean-burn engines (diesel engines and lean-burn gasoline engines) have received extensive attention due to their high fuel efficiency and low greenhouse gas emissions. However, a large amount of nitrogen oxides (NO x ) not only destroys the ecological environment, but also causes prominent environmental problems such as photochemical smog and acid rain, and has serious harm to human health. Therefore, how to effectively remove NO from lean-burn engine exhaust x It has become a research hotspot in environmental catalysis. A large number of studies have shown that the selective catalytic reduction of ammonia (NH 3 -SCR), Hydrocarbon Selective Catalytic Reduction (HC-SCR) and NO x Storage reduction (NSR) is the most p...

AI Technical Summary

Problems solved by technology

NO usually adsorbed by Pt / Ba / Al at 300°C x A large amount of desorption occurs above 450°C, NO x The hysteresis effect of desorption temperature leads to the reduction of active sites for NSR catalyst adsorption at low temperature, thus affecting the subsequent NO x Storage, reduces NO at low temperature x purification efficiency

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