摘要
研究了在Ｚｎ、Ｐｔ、Ｚｎ－Ｐｔ（双金属）改性的ＺＳＭ－５分子筛上进行的丙烷芳构化反应，并考察了预还原和反应温度对催化丙烷芳构化的影响．结果表明，在ＨＺＳＭ－５上，低温时主要是发生酸性裂解反应；高温则发生氢转移反应生成芳烃．使用Ｚｎ、Ｐｔ、Ｚｎ－Ｐｔ改性的ＺＳＭ－５催化剂显著提高了丙烷转化率和芳烃选择性，这主要是由于丙烷直接脱氢及中间产物脱氢的活性增强所致．氢气的预还原改善了Ｐｔ－Ｚｎ双金属催化剂的脱氢中心，致使中间产物更易于脱氢环化生成芳烃．根据ＴＰＲ结果初步推断，Ｐｔ和Ｚｎ之间存在相互作用，很可能形成了“合金”
おromatization of propane on ZSM5 zeolites modified with Zn, Pt and PtZn were studied. Experimental results show that H2 pretreament and reaction temperature affect aromatization. Over ZSM5 the mode of activation of propane varies with reaction temperature. Thus, propane undergoes cracking into methane and ethene by Bacid site on catalysts at low temperature. In contrast, at high temperature it undergoes hydride abstraction by its reaction with the carbenium ion. The modification of HZSM5 catalysts with Zn, Pt and PtZn improves the conversion of propane and the selectivity to aromatics. The incorporation of modifying elements prompts the dehydrogenation of propane and the tranformation of the products into aromatics. H2 pretreatment of PtZn catalysts modifies the dehydrogenation sites which are more effecitve for the tranformation of intermediate products into aromatics. According to TPR and reaction results, after H2 reduction the PtZn catalysts may form an “alloy” which suppresses hydrogenation and hydrogenolysis reactions.
出处
《分子催化》
EI
CAS
CSCD
北大核心
1998年第3期214-220,共7页
Journal of Molecular Catalysis(China)
