Two-section type catalyst for diesel vehicle exhaust treatment and preparation method of catalyst

Abstract

The invention provides a two-section type catalyst for diesel vehicle exhaust treatment. The catalyst comprises a catalyst A at a gas inlet end and a catalyst B at a gas outlet end, wherein the catalyst A has the general formula: CeO2-X/molecular sieve, and X is selected from CuO, Fe2O3 or MnO2; the catalyst B has the general formula: M@CeO2/molecular sieve, and M is selected from Rh, Pt or Pd. Compared with the prior art, the two-section type catalyst for diesel vehicle exhaust treatment has a high elimination effect and selectivity for nitric oxides in a relative wide temperature range, can eliminate particulate matter in a certain degree and also has the function of eliminating escaping ammonia. The catalyst B at the gas outlet end also has the functions of a DOC catalyst. Experimental results indicate that the two-section type catalyst has the nitric oxide conversion activity higher than 80%, good stability and excellent N2 selectivity at the high temperature of 150-550 DEG C and at the high space velocity of 240,000 h<-1>, and can eliminate carbon particles in exhaust at about 450 DEG C.

Description

technical field [0001] The invention relates to the technical field of catalysts, in particular to a two-stage catalyst used for treating diesel vehicle exhaust and a preparation method thereof. Background technique [0002] Nitrogen oxides (NO x ) mainly refers to NO and NO 2 , of which NO accounts for 95%. Nitrogen oxides are one of the main air pollutants, and their direct contact with air and water can cause many hazards, such as acid rain, photochemical smog, stratospheric ozone depletion, global climate change, etc. Nitrogen oxides in the atmosphere mainly come from mobile sources (motor vehicles) and stationary sources (mainly thermal power plants, industrial combustion devices), among which, 95% of the world's nitrogen oxides come from motor vehicle emissions (49%) and power plant emissions (46%). With the growth of energy consumption and the rapid increase of the number of motor vehicles, more and more acidic substances such as nitrogen oxides are discharged int...

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Problems solved by technology

[0004] However, there are still some problems in using it for diesel vehicle exhaust treatment, such as: narrow temperature window, high temperature N 2 Poor selectivity, with N 2 O formation and NH 3 oxidation, and TiO 2 At high temperature, the crystal structure will change, which will reduce the catalytic activity. At the same time, vanadium is poisonous to the environment and can withstand low space velocity.

The SSZ-13 molecular sieve catalyst used in the prior art for automobile exhaust treatment is BASF's SSZ-13 molecular sieve catalyst. Although the temperature window is relatively wide and it is resistant to high space velocity, its low-temperature activity is not high and particulate matter cannot be eliminated; while the particulate matter emission in diesel vehicle exhaust It is very harmful to people when exposed to the air

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