Cu-Ce(La)O_x变换催化剂的制备和性能考察

PREPARATION OF Cu-Ce(La)O_x CATALYSTS FOR WATER-GAS SHIFT REACTION AND THEIR CHARACTERISTICS

本文对采用共沉淀法制备的Cu-Ce(La)Ox高温变换催化剂进行了研究.首先研究了中和pH值、中和温度、焙烧温度和方式对催化剂性能的影响,其次研究了CuO、CeO2和LaOx含量对催化剂性能的影响.5%CuO-CeO2-La(10%)Ox高温变换催化剂的最佳制备工艺条件为pH=11,中和温度为54℃,400℃焙烧4h.催化剂的最佳配比组成为:CuO为20%、CeO270%、LaOx10%.XRD晶相分析表明,5%Cu-Ce-La(10%)OX催化剂中除了主相CeO2以外,还出现了Cu与La形成的钙钛矿型复合氧化物CuLaO2,且CuLaO2高度均匀地分散在主相CeOx中.还原态中除了CeO2、CuLaO2外,还出现了Cu单质,因此这类催化剂的活性中心不可能是简单的CuLaO2或Cu,从而使催化剂无论氧化态还是还原态都具有基本相同的活性,其活性位形态结构需要进一步研究.

Characteristics of Cu-Ce(La)O_x catalysts are studied,which are prepared by co-precipitation for water-gas shift reaction.It is learned that the neutralization pH,neultralization temperature,calcination and composition of CuO,CeO_2 and LaO_x all exert effect on the activities and crystallization of Cu-Ce(La)O_x catalysts.The optimum process conditions for preparation of 5%CuO-CeO_2-La(10%)O_x are:neutralization temperature 54 ℃,pH value 11,calcination temperature 400 ℃ for 4 h.The optimized composition is CuO∶CeO_2∶LaO_x=20∶70∶10 (atom ratio).XRD spectral analysis shows that in 5% CuO-CeO_2-La(10%)O_x, perovskite type oxides CuLaO_2 have been highly and evenly dispersed into the main phase CeO_2 (in the oxidation state),while in the reduction state there exist not only CeO_2 and CuLaO_2,but also Cu phase.It is very likely that other activity sites than CuLaO_2 or Cu can be found for the water-gas shift reaction,which makes the activity of catalysts either in the oxidation state or in the reduction state basically identical.The rather complex structure of activity sites requires further study.