Hydrotalcite-derived oxide-based nitrogen oxide trapping catalyst as well as preparation method and application thereof

Abstract

The invention discloses a hydrotalcite-derived oxide-based nitrogen oxide trapping catalyst, which takes CeO2-PtO2 / ZrO2 composite catalytic material nanoparticles as a core active component, and is supplemented with Mn-Fe modified hydrotalcite-derived composite oxide, gamma-Al2O3, La2O3 and a cordierite honeycomb ceramic carrier. The catalyst is coated in an LNT catalyst, and NOx discharged by a diesel engine is efficiently purified. The Ce-Pt / Zr composite catalytic material nanoparticles are extremely small in particle size, so that the overall catalytic activity of the catalyst is enhanced; ce in the main catalytic active component is doped with noble metal Pt, so that a synergistic interaction effect is generated between the two components, the heat resistance of the catalyst is improved, and the overall catalytic activity of the catalyst is enhanced; the preparation method of first adsorption and then precipitation based on the carbon black adsorption matrix significantly improves the dispersion effect of the metal oxide precursor, and is beneficial to preparation of composite oxide nanoparticles with smaller size and uniform particle size; the modified hydrotalcite derivative composite oxide is used for replacing an Al2O3 coating auxiliary material, so that the NOx adsorption capacity of the LNT catalyst is remarkably improved.

Description

technical field [0001] The invention belongs to the technology for purifying exhaust pollutants of vehicle internal combustion engines, in particular to a lean-burn NOx trap (LNT) catalyst for purifying nitrogen oxides (NOx) in diesel engine exhaust and a preparation method thereof. Background technique [0002] Diesel vehicles are the main force for heavy-duty passenger and cargo transportation at home and abroad, and have made outstanding contributions to the development of industry and agriculture and the progress of social life. certain damage. Driven by emission regulations, at present, relevant institutions and scholars have developed many technologies for controlling emissions from diesel vehicles. By applying these technologies, the pollutant emissions of diesel vehicles can meet the requirements of National IV and National V emission regulations. For the National VI emission regulations that have been implemented in stages, the NOx emission control of diesel vehicl...

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Problems solved by technology

[0004] At present, the traditional LNT catalyst configuration is mainly platinum (Pt) / barium oxide (BaO) / γ-alumina (γ-Al 2 o 3 ) / ceramic carrier system, in which noble metal Pt is used as the main catalytic active component, and its catalytic activity to NO oxidation reaction and adsorption NOx reduction reaction is very high, but Pt’s anti-sulfur, anti-coking, anti-thermal aging sintering performance is poor, And the high cost of raw materials makes LNT technology difficult to put into practical application

At the same time, as the adsorbent of traditional LNT catalyst, BaO has good NOx adsorption performance, but due to its poor coating performance, it must be combined with a large amount of γ-Al 2 o 3 A catalytic coating with qualified mechanical properties and adsorption properties can be formed on the surface of catalyst carrier pores by co-coating with other coating auxiliary materials.

Therefore, the coating auxiliary material is also indispensable in the traditional LNT catalyst, and its mass proportion in the catalytic coating is generally more than 70%, but the γ-Al 2 o 3 Commonly used coating auxiliary materials represented by general NO X The adsorption capacity is poor, and it contributes little to improving the NOx adsorption capacity of the LNT catalyst as a whole

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