摘要
用溶胶凝胶法合成了系列Ｒｈ／ＣｅＯ２／ＳｉＯ２，用浸渍法合成了Ｒｈ／ＣｅＯ２（Ⅰ），并用Ｈ２化学吸附，ＸＰＳ，ＴＰＲ等技术进行了表征．结果表明，在所用的实验条件下，铑完全还原，而ＣｅＯ２未还原．ＲｈＣｅＯ２间存在强相互作用．在常压ＣＯ加氢反应中，未加氧化物促进剂的Ｒｈ／ＳｉＯ２即能催化乙醛的生成，但产物中仅有极少量甲醇和乙醇．随着ＣｅＯ２含量的增加，催化剂的活性显著降低．ＣｅＯ２的加入降低了乙醛的选择性，而使乙醇的选择性升高，但没有显著改变Ｃ２含氧化合物的总量．在反应中阶跃加入探针分子的实验结果表明，产物烷烃不是由甲醇、乙醛和乙醇等含氧化合物转化生成的，乙醛和乙醇不是由甲醇转化生成的，乙醛也不是由乙醇脱氢生成的，但乙醇显然是由ＣｅＯ２催化乙醛加氢生成的．
A series of 2%Rh/CeO 2/SiO 2 and 2%Rh/CeO 2(Ⅰ) were prepared by sol gel method and impregnation method, respectively. XPS, TPR and H 2 chemisorption were used for characterization of the catalysts. XPS, TPR and H 2 chemisorption results showed that, under the experimental conditions, Rh was fully reduced but CeO 2 was not. There is a strong metal support interaction between Rh and CeO 2. In CO hydrogenation, 2%Rh/SiO 2, prepared by sol gel method, catalyzed the formation of MeCHO. But addition of even a very low concentration of CeO 2 decreased considerably the cataytic activity. On 2%Rh/SiO 2, the main O cotaining C 2 was MeCHO, but with the increase of CeO 2 content, the selectivity shifted to EtOH, while the total selectivity for O cotaining C 2 did not change appreciably. 2%Rh/CeO 2(Ⅰ), prepared by impregnation methed, showed higher selectivity for EtOH, which was attributed to the absence of SiO 2. The results with addition of MeOH, EtOH or MeCHO into the reactant gas stream showed that alkanes were not produced via the formation of O cotaining intermediate, O cotaining C 2 species were not formed through the conversion of MeOH, and MeCHO was not produced by the dehydrogenation of EtOH, but EtOH was formed through the hydrogenation of MeCHO. CeO 2 itself can catalyze the hydrogenation of MeCHO to EtOH, but the presence of Rh 0 was necessary to keep its activity.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
1999年第1期7-11,共5页
关键词
铑基
催化剂
氧化铈
一氧化碳
加氢
乙醇
rhodium based catalyst, cerium dioxide, carbon monoxide, hydrogenation, ethanol, probe molecule
