La－Sm－Sn－O烧绿石型甲烷氧化偶联催化剂的研制

Development of La-Sm-Sn-O Pyrochlore Type Catalysts for Methane Oxidative Coupling

为了研制用于从天然气制取乙烯的，具有良好的催化活性、选择性和稳定性的催化剂，用溶胶－凝胶法合成了系列稀上－锡复合氧化物Ｌａ２－ｘＳｍｘＳｎ２Ｏ７（ｘ＝０．０，０．５，１．０，１．５，２．０）．用ｘＲＤ对其结构研究表明：Ｌａ２－ｘＳｉｎｘＳｎ２Ｏ７，系列稀土－锡复合氧化物均具有烧绿石型结构，属立方晶系，空间群为Ｆ３ｄｍ．同时发现其晶胞参数ａｐｙｒ随Ｓｍ掺入量增加而近乎线性减小．并在脉冲激反应器上，对其催化活性进行评价．结果表明：Ｓｍ２Ｓｎ２Ｏ７复合氧化物对甲烷氧化偶联反应具有良好的催化活性，在ＣＨ４／Ｏ２＝４，温度在８００℃～９００℃，Ｘ＝２．０时，Ｃ２选择性为３８．１％，产率为９．２％，其中Ｃ２＝的选择性为２７．９％，产率为６．４％．同时发现晶格缺陷的形成有利于催化剂催化活性的提高．

he La2-xSm.Sn2O7 powders were prepared by sol-Gel mechod (x= 0. 0, 0. 5, 1.0, 1. 5, 2. 0). The x-ray diffraction shows that La2-xSmxSn2O7 has pyrochlore-type structure and belongs to cubic. Its space group was F3dm. The unit cell parameter apyv reduces nearly linearly with the increase of Sin. The catalytical activity of La2-xSmxSn2O7was evaluated in a pulse microreactor. La2-xSmxSn2O7 exhibited quite good activity and selectivity (38. 1 % ) for C2. The best of the systems (Sm2Sn2O7) gives a C2 yield 9. 2% at 800-900℃,x= 2. 0. The value of CH4/O2 was 4. It was found that the forming of cubic defect is advantageous to the increase of the calalyst's calalytic activity.