铜基催化剂上苯合成气烷基化的研究

通过浸渍法制备了用于苯合成气烷基化反应的铜基催化剂，并使用XRD,XRF,NH₃-TPD,TEM进行表征，固定床反应器进行评价。对于Cu/Al₂O₃/ZSM-5催化剂，最佳的反应温度是350℃，Cu载量越高其活性越好，负载Cu后出现的新的中等强度的酸中心有利于烷基化的进行。CO在金属中心发生加氢非解离反应，二甲醚（DME）是反应的主要中间体。第二金属（Zn,Mn,V）加入后有利于提高甲基化的选择性，降低重芳的选择性。在Cu-Zn/Al₂O₃/ZSM-5催化剂中，部分Cu被Zn覆盖导致了低的Cu分散度和活性。Cu-Mn/Al₂O₃/ZSM-5催化剂的甲基化收率最高，在新鲜剂中可能生成了Cu-Mn复合氧化物，这阻止了反应过程中Cu粒子的烧结。虽然V的引入使Cu的负载量大大减小，但同时也能引起中等强度酸中心数量的增多。V能够阻止还原过程中Cu粒子的烧结，并能提高Cu的活性。

Alkylation Activity of Benzene with Syngas over Cu-based Catalysts

A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples were prepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in a fixed bed reactor. The optimized reaction temperature of Cu/Al2O3/ZSM-5 catalyst was 350℃, while higher contents of copper were conducive to alkylation of benzene with syngas. The new medium strength acid centers in the catalyst created by Cu were beneficial to alkylation. Hydrogenation reaction of CO was executed on the metal centers without dissociation, Dimethyl ether (DME) was the major intermediate over Cu-based catalysts. Higher selectivity of methylation and lower selectivity of heavy aromatics were confirmed after the second metal (Zn, Mn, or V) was added to the copper catalyst. Cu was partly covered by Zn in the Cu-Zn/Al2O3/ZSM-5 catalyst leading to low dispersion and low activity of copper. Cu-Mn/Al2O3/ZSM-5 catalyst possessed the best yield of methylation product. Cu-Mn composite oxides were probably formed in fresh catalyst, which blocked the sintering of Cu in the reaction process. The loading of Cu decreased dramatically after the introduction of V, while causing an increase of the amount of medium strength acid centers at the same time. V prevented the sintering of copper particles during the reducing process and had a promoting effect on the activity of Cu.