铈在乙苯脱氢氧化铁基催化剂中的助催化作用  

Roles of Ce in Potassium-Promoted Iron Oxide Based Catalysts for Dehydrogenation of Ethylbenzene to Styrene

作　　者：祝以湘 何淡云[1] 林仁存 蔡庆叠 

机构地区：[1]厦门大学化学系,361005

出　　处：《高等学校化学学报》1991年第4期523-527,共5页Chemical Journal of Chinese Universities

摘　　要：研究了铈在Fe_2O_3-K_2O-CeO_2乙苯脱氢催化剂中的助催化作用。铈源为硝酸铈时助催效果明显,但CeO_2则不佳。助催化效果还与催化剂中的钾量有关。铈明显增进高钾催化剂的活性,但对催化剂的选择性无明显影响。The roles of cerium in Fe-K-Ce mixed oxide catalysts were investigated. Cerium increases very obviously the activity of the catalysts with high content of potassium but only had a little influ ence on that of the catalysts with low content of potassium in the case of this work. No evident influence of cerium on the selectivity of these catalysts was observed. From XRD, XPS, EDAX. TEM and the activity tests of these catalysts, it was found that cerium nitrate is a better precursor of the cerium promoter than CeO2 because Ce promoter would be located on the surface of the catalysts as micro crystals when the nitrate is used to prepare the catalysts and it would tend to be covered by iron ox ide if the CeO2 is used. According to the viewpoints that K2Fe2O4 is the active phase of the potassium-promoted iron oxide catalysts and that both the direct catalytic dehydrogenation and the catalytic deby drogenation by oxygen-transfer pathway are included in the process of the dehydrogenation of ethyl benzene to styrene, it is suggested that although the K2Fe2O4 is a good active phase for the direct dehy drogenation, it is not a good one for the oxygen-transfer dehydrogenation because of the poor mobility of the lattice oxygen in the K2Fe2O4 and that the role of the Ce promoter is transforing oxygen from steam to the K2Fe2O4 and creating many active sites for the oxygen transfer dehydrogenation. There fore, the contribution of the oxygen-transfer dehydrogenation mechanism in the overall Eli dehydru genation and then the activity of the overall EB dehydrogenation arc increased. Our experimental re suits could be satisfactorily explained based upon these suggestions.

关 键 词：铈 乙苯 脱氢 氧化铁基 催化剂 

分 类 号：O643.38[理学—物理化学]