Selective catalytic reduction catalyst based on copper-vanadium bimetallic modified molecular sieve and preparation method thereof

Abstract

The invention discloses a selective catalytic reduction catalyst based on a copper-vanadium bimetallic modified molecular sieve and a preparation method thereof. In the catalyst, a copper-vanadium bimetallic modified molecular sieve is taken as a main active component, CeO2 and ZrO2 are taken as auxiliary active ingredients, gamma-Al2O3 and SiO2 construct a coating auxiliary material, and 400-meshcordierite honeycomb ceramics is taken as a catalyst carrier. A preparation process comprises: determination of the using amounts of raw materials, preparation of the copper-vanadium bimetallic modified molecular sieve and preparation and coating of coating slurry. The advantages of high catalysis activity and high dispersity of a copper modified molecular sieve catalyst in a low-temperature SCR(Selective Catalytic Reduction) reaction and the advantage of high catalysis activity of V2O5 in a high-temperature SCR reaction can be brought into play at the same time; meanwhile, the using amountof the V2O5 is reduced, and the toxicity of the catalyst is lowered; the coating auxiliary material consisting of the gamma-Al2O3 and the SiO2 can improve the thermal stability and mechanical strengthof a catalytic coating, and the dispersion uniformity of the active components; through addition of the CeO2 serving as the auxiliary active component, the catalysis activity of the catalyst in the low-temperature SCR reaction is enhanced.

Description

technical field [0001] The invention belongs to the technical field of diesel engine tail gas purification, and in particular relates to a selective catalytic reduction catalyst based on copper-vanadium bimetallic modified molecular sieves and a preparation method thereof. Background technique [0002] Diesel engines for vehicles are widely used in the field of heavy-duty passengers and trucks due to their advantages such as high output power, high thermal efficiency, and durability, bringing great convenience to industrial and agricultural production and people's lives. However, due to the limitation of the combustion method, the NOx emission of the diesel engine is relatively large, which has caused serious harm to the atmospheric environment and human health. Especially with the rapid growth of the number of diesel vehicles in my country in recent years, the total NOx emissions of diesel vehicles and their contribution to the total atmospheric NOx emissions have also incr...

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Problems solved by technology

This type of catalyst has better catalytic performance for SCR reaction at a reaction temperature of 300-450 °C, and the above-mentioned catalytic activity temperature window is more suitable for national IV and national V diesel engines that mainly operate at high speeds and are not highly strengthened. High-temperature activity is poor, vanadium-based catalysts are not suitable for diesel vehicles running on urban roads (crowded roads, slow motor vehicles, relatively low exhaust temperature) and highly enhanced diesel engines (exhaust temperature > 450 ℃, relatively high); at the same time, V as the main active component in vanadium-based catalysts 2 o 5 It is a highly toxic substance, and it is loaded with a large dose of V in the SCR catalyst 2 o 5 It will inevitably endanger the environment and safety; in addition, WO must be added to the vanadium-based catalyst 3 or MoO 3 As a phase transition stabilizer, slowing down the TiO 2 The transition from anatase crystal phase to rutile crystal phase leads to complex catalyst preparation process and increased production cost

On the other hand, the United States, Japan and other developed countries have begun to use copper or iron element modified molecular sieve SCR catalysts on vehicle diesel engines. This type of catalyst has achieved certain improvements in the catalytic activity of low-temperature SCR reactions. (T50) drops to about 250°C, but it is still difficult to meet the demand for diesel vehicles running on urban roads in my country (T50 should be lower than 230°C), and the high-temperature SCR reaction catalytic activity of copper or iron-modified molecular sieve catalysts has not improved. , and cannot meet the needs of domestic high-strength diesel engines

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