尖晶石型铁酸盐催化剂的担体效应考察  

INVESTIGATION OF SUPPORT EFFECT OF ZnFe_2O_4 AND ZnCrFeO_4 CATALYSTS

作　　者：季伟捷[1] 李树本[1] 沈师孔[1] 王弘立[1] 陈晓曦[2] 肖国青[2] 

机构地区：[1]中国科学院兰州化学物理研究所 [2]中国科学院近代物理研究所

出　　处：《分子催化》1989年第1期10-19,共10页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金资助课题

摘　　要：用共沉淀法和浸渍法制备了ZnFe_2O_4、ZnCrFeO_4以及它们在γ-Al_2O_3,TiO_2,SiO_2小球上的担载催化剂.用TPR.XRD.ESR,MBS,脉冲反应等技术对这些催化剂进行了考察.结果表明,载体的引入在不同程度上改变了催化剂的氧化还原性能.在不同的载体上形成尖晶石结构的趋势不同.铁酸盐尖晶石相无论是非载的还是担载的对于多次交替的氧化还原处理不敏感.然而氧化铁相则较不稳定,而且在不同载体上稳定性相差较大.加Cr组份有助于担体上形成正尖晶石相.在某些较难形成铁酸盐尖晶石相的担载催化剂中,其相的组成较为复杂.脉冲反应的结果表明,担载的单一正尖晶石铁酸盐以及γ-Al_2O_3上的氧化铁对丁烯氧化脱氢均有一定的活性,对于既含较多量正尖晶石铁酸盐又含一定量氧化铁的催化剂,其较好的催化性能暗示在这两相之间可能存在某种协同效应.ZnFe2O4, ZnCrFeO4and their supported catalysts (on TiO2, SiO2and γ-Al2O3) are prepared by precipitation and impregnation respectively. The loading of supported components is all about 25%.Several techniques(TPR,XRD,ESR,MBSand pulse reaction)are used to characterize these catalysts. The results show that supports can change the oxidation-reduction properties of catalysts to a greater or lesser degree. It seems that unsupported ZnFe2O4catalyst is deeply reduced and more difficultly to be reoxidized as compared with the corresponding supported catalysts . The oxidation-reduction properties of the active phase of γ-Al2O3are quite good compared with that of active phase on SiO2, whereas TiO2only has a slight effect on this aspect.The spinel phase whether is on the support or not is not very sensitive to reduction-reoxidation treatment for several times. Because of the interaction between the support and supported component, the trend of forming the spinel structure on the supports is TiO2 > SiO2 > γ-A12O3. Supported ZnO component reacts mainly with y- Al2O3to produce ZnAl2O4instead of ZnFe2O4, so the amount of ZnFe2O4or ZnCrFeO4phase on γ-Al2O3is small. Similarly, the interaction between SiO2and supported iron oxide hinders the formation of ZnFe2O4phase on SiO2. On the contrary, the ZnO and iron oxide on TiO2react with each other completely to form almost pure spinel phase on the support .The iron oxide on different supports has a different stability .The iron oxide on SiO2is more stable than that on γ-Al2O3but it generally turns into some amount of ferromagnetic substance when treated. The addition of Cr component to the catalyst is favourable to forming the spinel structure on supports and improves the oxidation-reduction properties of catalysts. When Cr is added, only pure spinel phase exists on supports except γ-A12O3. Some supported catalysts on which the spinel structure cannot be formed easily have complex composition. Most of the active phase of these catalysts is iron oxide with various forms, including

关 键 词：尖晶石型 铁酸盐 担体效应 催化剂 

分 类 号：O643.36[理学—物理化学]