不同方法制备的Zn/HZSM-5催化剂上甲烷和丙烷的无氧芳构化研究

Study on the non-oxidative aromatization of methane-propane over Zn/HZSM-5 catalysts prepared by different methods

采用浸渍法、一般离子交换和络合离子交换制备Zn/HZSM-5催化剂,用于甲烷和丙烷混合气的无氧芳构化研究,其中络合离子交换法制备的催化剂活性最好.在反应温度823 K,空速600 h-1,甲烷/丙烷摩尔比为5∶1的条件下,丙烷转化率和芳烃选择性分别达99.93%和80.29%.Zn/HZSM-5上经CH4-C3H8芳构化反应后,表面存在至少两种类型的积碳,分别对应于CHx活性中间体,类石墨碳或石墨碳,前者可用高温H2消除,后者要在O2气氛下才能被消除.本文主要讨论3种不同制备方法对催化剂活性和产物分布的影响,以及催化剂失活再生以后的活性及选择性.利用NH3-TPD、TG、TPO/TPH(H2-TPSR)、UV-Raman等技术考察了不同制备方法对Zn/HZSM-5催化剂表面酸性和积碳的影响.

The influence of different preparation methods on the non-oxidative aromatization of Methane-Propane over Zn/HZSM-5 was investigated, such as the conversion of propane, selectivity of BTX, and the carbon species after reaction. Under 823 K and atmosphere pressure with space velocity 600 h^-1 and CH4/C3H8 （molar ratio）： 5 ： 1, the propane conversion and the aromatics selectivity were up to 99. 93% and 80.29% over the catalysts. There are at least two different carbon species on the surface of Zn/HZSM-5 catalysts after CH4-C3 H8 aromatization reactions, the CHx active intermediate can be removed in H2 atmosphere in high temperature while the graphite can only be eliminated in O2 atmosphere. The coke and the surface acid of the catalysts were characterized by UV-Raman, TPO/TPH（ H2-TPSR）, NH3-TPD and TG..