钴改性水滑石基LNT催化剂制备及其NO_x吸附-还原和碳烟催化氧化性能

Preparation of Cobalt Doped Hydrotalcite-Based LNT Catalysts and Their Performances of NO_x Adsorption-Reduction and Soot Oxidation

采用共沉淀法和浸渍法制备了贵金属负载的Co改性水滑石基LNT(leanNO_x trap)催化剂,通过多种实验手段表征其理化特性,并研究其NO_x吸附-还原性能及碳烟催化氧化性能.结果表明,Co的引入并不会破坏前驱体水滑石晶体结构,500℃焙烧后原本的水滑石结构被破坏,并出现明显的CoAl_2O_4尖晶石相.Co含量的上升会导致催化剂表面的Co—O吸附位增加,同时催化剂表面吸附的亚硝酸盐物种会逐渐向硝酸盐物种转化.此外,随着Co含量的增加,NO_x脱附峰温度向低温区域移动,脱附峰面积先增加后降低.Pt/BaO/Co_(2.7)Mg_(0.3)AlO催化剂在NO_x吸附-还原反应中对NO_x的净化效率达到89.6%,同时针对碳烟的催化氧化反应又表现出良好的催化性能.

A series of cobalt-doped hydrotalcite-based lean NOx trap(LNT)catalysts with a well dispersed noblemetal were synthesized using the co-precipitation and impregnation methods.In addition to the physical-chemical properties,the performances of NOx adsorption-reduction and soot oxidation of the prepared catalysts were also investigated using multiple experimental methods.The research results indicate that the addition of cobalt did not affect the original structure of hydrotalcite-like precursors.After calcination at 500 ℃,however,the structure of hydrotalcite precursors was destroyed,and the Co Al2 O4 spinel structure appeared.The increasing Co content would increase the Co-O adsorption sites on the LNT catalyst surface;meanwhile,the nitrite species on the catalyst surface were gradually transformed into nitrate species.Moreover,with the increase in Co loading,the peak temperature of NOx desorption moved to the low temperature range,and the desorption capacity rose at first but then decreased.The Pt/BaO/Co2.7 Mg0.3 AlO catalyst achieved a NOx reduction efficiency of 89.6%,and exhibited an excellent performance in the reaction of soot oxidation.