镍改性 HZSM-5催化剂上甲醇芳构化反应性能的研究

摘要

The performance of modified HZSM-5 catalysts with different loadings of nickel on the aromatization of methanol was investigated in a continuous fixed bed microreactor using pure methanol as raw material.The catalysts were characterized by BET,XRD,Py-FTIR,and NH3-TPD techniques.Results show that the introduction of nickel species results in the formation of new Lewis acid sites.Furthermore,the total acid amount of the HZSM-5 catalyst increases gradually,especially the weak acid,with increasing amount of nickel.The total aromatic yield decreases first and then increases,fol-lowed by decrease again with the Ni loading. The introduction of nickel species may change the path from the hydrogen transfer aromatization to the dehydrogenation aromatization. In addition,aromatic hydrocarbons generated are mainly C7—C9 aromatics,while C6 and C10+ aromatics are relatively few.Meanwhile,by-products such as methane and COx increase gradually with the increase of nickel loading, which is probably in correlation with the enhancement of methylation of methanol caused by nickel species.%采用浸渍法制备 Ni改性的 HZSM-5催化剂，采用 BET，XRD，Py-FTIR，NH3-TPD等分析手段对催化剂进行表征。以纯甲醇为原料，在固定床微反装置上，考察不同 Ni负载量改性 HZSM-5催化剂对甲醇芳构化（MTA）反应性能的影响。实验结果表明：Ni的引入使催化剂产生了比较稳定的新 L酸位；随着 Ni负载量的增加，Ni？HZSM-5催化剂的总酸量增加，尤其是弱酸酸量；MTA反应的芳烃总收率随着 Ni负载量的增加呈现先减少后增加然后又减少的趋势；Ni的引入可能改变了 HZSM-5催化剂上 MTA反应的路径，由氢转移芳构化向脱氢芳构化转变；生成的芳烃主要以C7～C9芳烃为主，C6和 C10＋芳烃相对较少；副产物甲烷和 COx收率则随 Ni负载量的增加而增加，这可能与 Ni促进了甲醇的甲烷化反应有关。