高活性甲醇氧化羰基化CuY催化剂的结构及催化活性中心

采用硝酸铜溶液和NaY分子筛溶液离子交换制备了CuY催化剂，通过加入氨水提高交换溶液的pH值以及高温焙烧活化，显著提高了甲醇氧化羰基化合成碳酸二甲酯的催化活性，与固相离子交换、沉积和浸渍法制备的催化剂相比，虽负载的铜量较低，但催化活性较高. 通过元素分析、XRD、H2-TPR、XPS和AES等对CuY催化剂微观结构的表征表明，在Cu(NO3)2离子交换溶液中加入氨水，促进了Cu2+离子交换的进行，提高了CuY催化剂的Cu交换量，并且交换的Cu2+主要落位于分子筛的超笼中. 在惰性气氛中焙烧活化CuY催化剂，Cu2+自还原为Cu+，氨促进了自还原过程的进行，显著提高了催化剂的活性. 焙烧活化温度越高，越有利于超笼中Cu2+→Cu+的自还原过程，使超笼中Cu+的含量增加， CuY催化活性增加. 进一步研究表明Y分子筛超笼中的Cu+是主要的催化活性中心.

Structure and Catalytic Active Center of High Catalytic Activity CuY Catalysts in Oxidative Carbonylation of Methanol

In the preparation of CuY catalysts by ion-exchange of NaY zeolite with aqueous solution of copper nitrate, ammonia was added to the ion-exchange solution to adjust the pH and the ion-exchanged CuY was activated by high temperature calcination.The prepared CuY catalysts exhibited high catalytic active in the oxidative carbonylation of methanol to dimethyl carbonate. Compared with Cu catalysts prepared by solid-state ion-exchange, precipitation and impregnation, CuY catalysts loaded less Cu but showed good catalytic performance. Based on the characterization of the microstructure of CuY catalysts by XRD, XPS, AES, H2-TPR and elementary analysis, it was shown that by adding ammonia into the ion-exchange solution，the ion-exchanged reaction was promoted, resulting in the increase of the ion-exchanged Cu2+ and the most of Cu2+ in the supercage of CuY catalyst. In the process of calcinating activation of CuY catalysts in inert atmosphere, Cu2+ was auto-reduced to Cu+ and ammonia promoted the auto-reduction, which was conducive to the improvement of catalytic activity. The high activating temperature facilitated the auto-reduction progress of Cu2+ to Cu+ located in the supercage of zeolite, Cu+ content in the supercage of zeolite increased more quickly and the catalytic activity of CuY catalysts increased in the meantime. It was concluded that Cu+ in the supercage of Y zeolite was the main catalytic active center.