High-temperature hydrothermally stable silicon-modified SCR catalyst and preparation method thereof

Abstract

The invention provides a silicon-modified SCR catalyst with high hydrothermal stability. The SCR catalyst is a composite oxide obtained by modifying WO<3> / Ce<x>Zr<1-x>O<2> with silicon and has a chemical formula of WO<3> / SiO<2> / Ce<x>Zr<1-x>O<2>, wherein x is more than 0 and less than 1; the mass fraction of WO<3> in the catalyst is greater than 0 and less than or equal to 15%; and the mass fraction of SiO<2> in the catalyst is in a range of 2 to 8%. The preparation method comprises the following steps: adding cerium-zirconium composite oxide powder Ce<x>Zr<1-x>O<2> into deionized water; addingethyl orthosilicate (TEOS) under stirring at room temperature, carrying out stirring for 5-15 h at first, then performing standing for 6-15 h at room temperature, continuing stirring for 1-6 h, and then carrying out solid-liquid separation to obtain a precipitate; drying the obtained precipitate to obtain SiO<2> / Ce<x>Zr<1-x>O<2> powder; and then subjecting a tungsten source to equivalent-volume impregnation into the SiO<2> / Ce<x>Zr<1-x>O<2> powder. The catalyst obtained in the invention shows excellent resistance to hydrothermal aging in the selective catalytic reduction of nitrogen oxides byammonia, has excellent catalytic activity and is friendly to environment.

Description

technical field [0001] The invention belongs to NH 3 -SCR catalyst field, specifically related to a catalytic purification of diesel vehicle exhaust NO x Gas non-vanadium based WO 3 / CeZrO 2 Composite oxide NH 3 -SCR catalyst. Background technique [0002] With the promulgation of increasingly stringent nitrogen oxide emission regulations around the world, NO in lean-burn vehicle exhaust x Purification has become one of the environmental problems that need to be solved urgently. Nitrogen oxides can cause environmental problems such as acid rain, photochemical smog, greenhouse effect and ozone hole, and cause serious harm to human health and the ecological environment. 95% NO in the atmosphere x It comes from motor vehicle exhaust (49%) and flue gas (46%) emissions from thermal power plants. Ammonia Selective Catalytic Reduction of NO x (NH 3 -SCR) is currently the most promising diesel vehicle exhaust NO x Purification technology has been industrialized in develop...

AI Technical Summary

Problems solved by technology

[0003] V 2 o 5 -WO 3 (MO 3 ) / TiO 2 A series of catalysts (i.e. vanadium-based catalysts) have been successfully applied to stage IV (National IV) and V (National V) diesel vehicles to purify their exhaust NOx. With the more stringent sixth stage (i.e. National VI) emission standards The promulgation of this type of catalyst does not meet the National VI and higher standards for diesel vehicle exhaust NO x emission requirements

Mainly because there are still some unavoidable shortcomings of vanadium-based catalysts: the effective working window (300-400°C) of this type of catalyst cannot adapt to the temperature range of diesel vehicle exhaust (175-550°C); 3 The non-selective oxidation of NO x The purification rate drops rapidly, and a large amount of greenhouse gas N is produced 2 O, leading to the main product N 2 The selectivity of the vanadium-based catalyst is significantly reduced, and it also causes secondary pollution to the atmosphere; the thermal stability of the vanadium-based catalyst is poor, V 2 o 5 Has strong biological toxicity

However, WO 3 / CeZrO 2 After the catalyst is hydrothermally aged, Ce will be generated on the surface of the catalyst 2 (WO 4 ) 3 , leading to catalyst deactivation

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