CeO_2-TiO_2混合氧化物及Pd/CeO_2-TiO_2催化剂的氧化还原性能  

Redox Property of CeO_2-TiO_2 Mixed Oxide and Pd/CeO_2-TiO_2 Catalyst

作　　者：朱华青[1] 秦张峰[1] 王建国[1] 

机构地区：[1]中国科学院山西煤炭化学研究所煤转化国家重点实验室,山西太原030001

出　　处：《催化学报》2005年第5期377-382,共6页

基　　金：国家自然科学基金资助项目 (2 0 5 90 3 63 )

摘　　要：以溶胶 凝胶 超临界流体干燥法制备了CeO2 TiO2 混合氧化物(n(Ce) /n(Ti) =0 0 5～0 4 0 ) ,以其为载体,通过等体积浸渍法制备了Pd/CeO2 TiO2 催化剂.XRD分析结果表明,在低Ce/Ti比的CeO2 TiO2 混合氧化物中,CeO2 高度分散于TiO2上;Ce/Ti比高于0 10时,大晶粒锐钛矿相TiO2 和TiO2 CeO2 固溶体或其前驱体无定形相共存.采用H2 TPR对所合成材料的氧化还原性能进行了研究.H2 TPR谱中5 0 0℃附近的耗氢峰对应于CeO2 TiO2 中CeO2 的还原,还原过程中不存在表面晶格氧与体相晶格氧的差别.由于TiO2 与CeO2 的协同作用,混合氧化物中形成了丰富的结构缺陷,提高了CeO2 的氧化还原性能,其中Ce/Ti比为0 2 0时TiO2 与CeO2 的协同作用最显著.负载上Pd后,载体中CeO2 的还原温度(<15 0℃)大大降低,同时随着Ce/Ti比的增大,PdO与载体间的相互作用增强,导致PdO难于还原,相应的H2The CeO_2-TiO_2 mixed oxide and its corresponding supported catalyst Pd/CeO_2-TiO_2 with Ce/Ti molar ratio of 0 05～0 40 were prepared by sol-gel and supercritical fluid drying method. Their redox properties were investigated by means of H_2-TPR. For CeO_2-TiO_2 with low Ce/Ti ratio, ceria is finely dispersed on TiO_2. When Ce/Ti ratio is higher than 0 10, the anatase phase TiO_2 with large crystallite size and amorphous TiO_2-CeO_2 solid solution or its precursor coexist in the mixed oxide. Ceria in the mixed oxide is completely reduced at about 500 ℃, while only 40% of surface ceria in pure CeO_2 is reduced at 504 ℃ and the remnant bulk ceria need higher temperature (804 ℃) to get reduced. These may be ascribed to the synergistic effect between CeO_2 and TiO_2, which produces abundant structural defects and improves the redox property of CeO_2 in CeO_2-TiO_2. The CeO_2-TiO_2 mixed oxide with Ce/Ti ratio of 0 20 exhibits the most evident synergistic effect between CeO_2 and TiO_2. In Pd/CeO_2-TiO_2, the interaction between Pd and the support leads to a significant decrease in ceria reduction temperature (<150 ℃). The H_2 consumption peak of PdO in H_2-TPR profiles shifts to higher temperature with the increase in Ce/Ti ratio due to the enhancement of the interaction between PdO and CeO_2-TiO_2.

关 键 词：氧化铈 二氧化钛 混合氧化物 钯 程序升温还原 氧化还原性能 

分 类 号：O643.3[理学—物理化学]