CuCl_2/γ-Al_2O_3催化剂的EPR研究  

AN EPR STUDY ON CuCl_2/γ-Al_2O_3 CATALYST

作　　者：蔡小海[1] 谢有畅[1] 吴世杰 唐有祺[1] 

机构地区：[1]北京大学物理化学研究所,100871

出　　处：《波谱学杂志》1992年第3期247-256,共10页Chinese Journal of Magnetic Resonance

摘　　要：通过测定Cu含量不同的新鲜CuCl_2/γ—Al_2o_3催化剂的EPR谱,以及对EPR谱的线型及强度的计算机处理和理论拟合等,研究了催化剂中CuCl_2在载体表面的分散方式,和Cu含量对Cu^(2+)配位形式的影响.EPR结果表明,催化剂表面的Cu^(2+)至少有两种不同配位状态.新鲜催化剂中所存在的两种不同谱线的比例决定了EPR谱的线型和强度,而两种谱线的比例又取决于催化剂中的Cu含量.在低Cu催化剂中Cu^(2+)相互离散,倾向于形成富氧配位,具有较高的EPR强度,只有在Cu含量较高时,Cu^(2+)才能形成富氯配位.鉴于低Cu催化剂不能与乙烯反应,而高Cu催化剂则可以使乙烯转化为二氯乙烷的事实,认为富氧配位的Cu^(2+)可能具有与乙烯反应的活性.The EPR spectra of CuCl2 and a series of CuCl2/γ-A12O3 samples have been compared, and fitted using the theory formula of EPR powder spectra. The results suggest that there are two distinct coordination sites for Cu2+ ions in the samples of fresh catalyst at least, which are both different from that of Cu2+ ions in CuCl2 or in CuCl2· 2H2O. The EPR parameters obtained by fitting show that one of them might be due to the site with plenty of coordinate O2- , and the other might be due to the site which is rich in coordination Cl-. Their propotions varies with the Cu contents in the samples. In the catalyst with low CM content, Cu2+ ions prefer to go into the cavities formed by O2-coordination-unsaturated on the surface of γ - A12O3 in monolayer, and to separate from each other while dispersing. The intensity data of EPR are in agreement with this fact also. But in the catalyst with higher Cu load, which has higher catalytic activity, including its specific activity, much more Cu2+ ions exist in Cu-Cl coordination manner. This fact implies that Cu2+ ions with more Cl neighbors in the catalyst might be correlative to catalytic activity of oxychlorination.

关 键 词：催化剂 EPR 配位 铜离子 

分 类 号：O643.36[理学—物理化学]