Abstract:

Based on the current understanding of the nature of the propane aromatization catalyst,the catalytic activity of Ga modified HZSM-5 prepared by different impregnation methods is studied,including incipient wetness,vacuum assisted incipient wetness,and microwave assisted incipient wetness impregnations. With the help of various catalyst characterization techniques,the microscopic changes of the catalysts after modification were examined. The result showed that methods of impregnation had significant effects over dispersion of Ga species on the surface of the catalysts where vacuum assisted impregnation was proved to have the best results. At reaction temperature of 525℃,propane WHSV=1 h^-1,product sampled after 1.3 h of propane on stream time suggested a propane conversion of 93.8%,liquid aromatization yield of 57.2% and BTX yield of 48.6%. Vacuum assisted impregnation methods led to better Ga distribution thereby reduced B acid sites and increased L acid sites. This modification resulted in inhibited propane cracking,increased dehydrogenation and aromatization reactions,as well as a longer catalyst life.

Key words: molecular sieve, Ga, alkane, vacuum assisted incipient wetness impregnation, dehydrogenation, cracking, selectivity

摘要：

根据现有丙烷芳构化催化剂的特性，考察等体积浸渍、真空等体积浸渍、微波等体积浸渍3种不同浸渍方法对镓改性HZSM-5催化剂性能的影响，并结合多种技术表征，分析改性后催化剂内部性能变化情况。研究发现，浸渍方法对催化剂表面镓的分散度具有明显的影响，其中真空等体积浸渍具有更好的效果，使活性组分Ga分散更均匀，更有效地降低了分子筛的B酸位、增加了L酸位，进而抑制了丙烷的裂解，增强了催化剂的脱氢、芳构化能力，并且延长了催化剂的寿命。在反应温度为525℃，丙烷质量空速（WHSV）为1 h^-1的条件下，取样时间为丙烷通入后1.3 h，丙烷转化率达到93.8%，液相芳烃收率达到57.2%，BTX（苯、甲苯和二甲苯）收率达到48.6%。

关键词: 分子筛, 镓, 烷烃, 真空等体积浸渍, 脱氢, 裂解, 选择性