改性介孔Al_2O_3负载的高分散铜基催化剂的结构与催化性能

采用浸渍法制备了LaCeZr或YCeZr改性的γ-Al2O3负载的系列Cu基催化剂,运用XRD、BET、EXAFS、XPS和H2-TPR等技术对催化剂的结构进行了详细表征,探讨了催化剂中Cu物种的存在形式及其还原性能,并与CO的氧化性能相关联。氮气吸附-脱附测试结果表明,催化剂具有很高的比表面积以及较均一的介孔结构。XRD结果表明,未改性的γ-Al2O3负载的Cu基催化剂经800℃高温焙烧后,Cu物种与载体作用强烈,形成了CuAl2O4尖晶石相,而EXAFS结果显示,助剂改性后的γ-Al2O3负载的Cu基催化剂上Cu物种主要以高分散的CuO形式存在,促进了催化剂对CO的低温氧化性能。H2-TPR结果表明,同一系列样品随焙烧温度提高,CuO的还原温度升高,晶格氧的活动度降低,导致活性的下降。LaCeZr改性的γ-Al2O3负载的铜基催化剂于650℃焙烧后显示出了较强的抗硫和抗水性能。

Structures and Catalytic Performance of Highly Dispersed Cu-Based Catalysts Supported on Modified Mesoporous Al2O3

The Cu-based catalysts supported on mesoporous γ-Al_2O_3 modified by LaCeZr or YCeZr were prepared by impregnation. The structures of the catalysts were carefully characterized by XRD, BET, XAFS, XPS and H_2-TPR techniques. The state of copper species and their reducibility were investigated and correlated with the CO oxidation performance of the catalysts. N_2 adsorption and desorption isotherms reveal that the catalysts possess high specific surface areas and uniform pore size distributions in mesoporous range. The XRD results indicate that after calcination at 800℃ the copper species supported on pure γ-Al_2O_3 without modification exist as CuAl_2O_4 spinel, while the EXAFS results show that the copper species supported on γ-Al_2O_3 modified by LaCeZr or YCeZr exist as highly dispersed CuO crystallites, which facilitates the CO oxidation. H_2-TPR results show that for the same series of the catalysts the reduction peaks of CuO species shift to higher temperatures with the calcination temperature increasing, implying the decrease of the mobility of lattice oxygen, and resulting in the decrease of oxidation activity. The copper catalyst supported on γ-Al_2O_3 modified by LaCeZr exhibits strong sulfur and water-resistance performance after calcination at 650℃.