关键词: 乙苯脱氢, 铈助催剂, 氧化铁基催化剂, 苯乙烯

Abstract: 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 CeO₂because 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 CeO₂is used. According to the viewpoints that K₂Fe₂O₄is 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 K₂Fe₂O₄is 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 K₂Fe₂O₄and that the role of the Ce promoter is transforing oxygen from steam to the K₂Fe₂O₄and 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 EBdehydrogenation arc increased. Our experimental re suits could be satisfactorily explained based upon these suggestions.

Key words: Dehydrogenation of ethylbenzene, Cerium promoter, Iron oxide based catalyst, Styrcne