Catalyst for diesel engine on basis of perovskite and modified hydrotalcite-derived oxide and preparation method thereof

Abstract

The invention discloses a catalyst for a diesel engine on the basis of perovskite and a modified hydrotalcite-derived oxide, wherein a substitutional perovskite composite oxide and noble metals are adopted as main active components, BaO is adopted as an absorbent, CeO2-ZrO2 is adopted as a cocatalyst, La-modified hydrotalcite-derived oxide and gamma-Al2O3 are adopted as coating additives, and cordierite honeycomb ceramic is adopted as a catalyst carrier. A preparation process comprises the following steps of: determination of the use amount of raw materials; preparation of the substitutional perovskite composite oxide and the modified hydrotalcite-derived oxide, and preparation and coating of coating slurry. The catalyst and the preparation process disclosed by the invention have the beneficial effects that by cyclic change of lean/rich condition, the catalyst can catalyze adsorbing-reducing purifying reaction of NOx in exhaust of the diesel engine by high efficiency; the substitutional perovskite composite oxide partially replaces the noble metals, so that the cost of raw materials is reduced; the modified hydrotalcite-derived oxide partially replaces Al2O3 coating additive, so that the NOx adsorbing capability of the LNT (Lean NOx Trap) catalyst is obviously improved.

Description

technical field [0001] The invention belongs to the purification technology of diesel engine tail gas pollutants, in particular to an adsorption-reduction catalyst used for purifying nitrogen oxides (Nitrogen Oxides, NOx) pollutants in diesel engine tail gas and a preparation method thereof. Background technique [0002] As the public pays more and more attention to environmental quality and human health, the call for strict control of motor vehicle exhaust pollutants has become increasingly strong. The Chinese government and related agencies have formulated increasingly stringent tail gas emission regulations to limit motor vehicle pollutants. Emissions, and these emission regulations have in fact promoted the development and progress of motor vehicle exhaust control technology. At present, domestic diesel vehicles that meet the National IV and National V emission regulations generally use Selective Catalytic Reduction (SCR) technology to reduce NOx emissions in diesel vehi...

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Problems solved by technology

Traditional LNT catalysts require precious metals as the main active components, which have high production costs and poor sulfur resistance, and have extremely high requirements on the sulfur content in fuels; BaO alkaline adsorbent is a good NOx adsorption material, and the saturated NOx adsorption capacity is very high , but because too much BaO in the traditional LNT catalyst will deteriorate the stability of the catalyst coating, its mass ratio is limited, resulting in a limited overall saturated adsorption capacity of the traditional LNT catalyst, and too frequent switching between lean-burn / rich-burn operating conditions of diesel engines. The power and economic performance of the diesel engine will be adversely affected; 2 o 3 Catalyst coatings prepared as additives have good mechanical strength and large specific surface area, but due to Al 2 o 3 Can not adsorb NOx, with Al 2 o 3 Coatings prepared as additives cannot assist in increasing the saturated NOx adsorption capacity of LNT catalysts; in addition, high loadings of Al 2 o 3 It is easy to react with BaO at high temperature to form BaAl with spinel structure 2 o 4 , resulting in NO X The loss of adsorption active sites further deteriorates the adsorption performance of LNT catalysts for NOx

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