Composite catalyst for NH3-SCR reaction and preparation method and application thereof

The invention provides a composite catalyst for an NH3-SCR reaction and a preparation method and the application of the composite catalyst for the NH3-SCR reaction. The composite catalyst takes a molecular sieve as a carrier, and is loaded on transition metal on the molecular sieve to be taken as an active component through ion exchange. The method disclosed by the invention comprises the following steps: firstly, mixing the molecular sieve with a salt solution of the transition metal to perform an ion exchange reaction, and then carrying out solid-liquid separation and calcination to obtain an AEI molecular sieve catalyst. The composite catalyst prepared by the invention is non-toxic and harmless on used raw materials and simple and easy in preparation method and has the characteristics of high catalytic activity, low N2O formation amount, wide operating temperature window, capability of adapting to high-altitude velocity reaction conditions and the like, and suitability for carryingout catalytic purificatio