ROLE OF Ga AND Pt-Ga IN THE CONVERSION OF PROPANE OVER Ga/HZSM-5 AND Pt-Ga/HZSM-5

为获得较高的Ｃ２选择性，在加水（水蒸气）条件下，研究了添加ＣａＯ对甲烷氧化偶联Ｌａ２Ｏ３催化剂的影响。发现ＣａＯ的添加提高了Ｌａ２Ｏ３催化剂的活性，同时水的添加明显地提高了催化剂的Ｃ２选择性。在加水条件下，Ｌａ２Ｏ３－ＣａＯ催化剂获得了较好的结果，其ＣＨ４转换率为２０％，Ｃ２选择性超过８０％。利用ＸＲＤ和ＸＰＳ技术对催化剂进行了表征，并对加水和不加水条件下的催化剂性能与结构变化的关系进行了讨论

ROLE OF Ga AND Pt-Ga IN THE CONVERSION OF PROPANE OVER Ga/HZSM-5 AND Pt-Ga/HZSM-5

The conversion of light alkanes to aromatics, chiefly benzene, toluene and xylene (BTX), could be accomplished by using zeolites of ZSM-5 type. Over HZSM-5, the propane conversion and the selectivity to aromatics are lower, but over ZSM-5 modified with Ga or Pt-Ga (bimetal), both the total conversion and the selectivity to aromatics are increased. It is found that the number of Br o.. sted acid sites decreases on the Ga/HZSM-5 catalyst pretreated with hydrogen. The addition of Pt promotes the reduction of Ga species on Pt-Ga/HZSM-5, and the reduced Ga species may neutralize a part of acid sites on Ga/HZSM-5, resulting in highly unsaturated sites. These sites may act as Lewis acidic sites which are able to abstract hydride ions from propane and intermediate oligomers, and then propane forms aromatics selectively.