Preparation method of composite oxide catalyst used for purifying diesel engine

The invention relates to a preparation method of a composite oxide catalyst used for purifying a diesel engine and belongs to the technical field of catalysis. The catalyst is prepared with cordierite honeycomb-like ceramic as a carrier, with [gamma]-Al2O3 as a coating and with Pt as an active component with addition of components such as Ce, Ba and the like. In the composite oxide catalyst, one or two coated catalysts can be employed, when one coated catalyst is employed, the coated catalyst is one of an oxidizing catalyst or a reducing catalyst and the catalyst can be used for coating an A zone and a B zone of the carrier at different coating amounts; and when two coated catalysts are employed, one is the oxidizing catalyst and the other is the reducing catalyst. The one or two catalysts coat the same carrier with different loading capacities in the A zone and the B zone of the carrier. The composite oxide catalyst can effectively reduce discharge of PM and NOx in tail gas of the diesel engine, can effectively increase the conversion rates of the PM and the NOx, and is better in economy.