MnO2负载量对MnO2/HBeta分子筛催化二甲醚制六甲基苯反应性能的影响

Effect of MnO_2 loadings on the catalytic conversion of dimethyl ether to hexamethylbenzene over MnO_2/HBeta zeolites

在连续流动固定床反应器上考察了不同MnO_2负载量的MnO_2/HBeta分子筛催化二甲醚制六甲基苯的性能,结果表明:10%MnO_2改性HBeta有利于提高六甲基苯选择性。在常压、反应温度为280℃、空速为100h-1条件下,10%MnO_2/HBeta催化二甲醚反应,二甲醚转化率达76.36%,HMB选择性为25.1%。利用NH_3-TPD,Py-IR,BET及XRD等对催化剂的结构和性质进行表征,结果表明,随着MnO_2负载量的增加,MnO_2在催化剂中逐渐以晶体结构存在,且催化剂表面强酸中心逐渐增加,而催化剂B酸酸性呈现出先减弱后增强的趋势。10%MnO_2改性HBeta催化剂具有适宜的表面酸性,有利于HMB的生成。

The MnO2/HBeta catalysts with different MnO2 loadings were prepared by impregnation method, and characterized by NH3-TPD, Py-IR, BET and XRD. Catalytic conversion of dimethyl ether to hexamethylbenzene （HMB） over the prepared catalysts was investigated in a continuous flow fixed-bed reactor. The results showed that 10%MnO2/HBeta exhibited the best selectivity to HMB. Under the reaction conditions of atmosphere pressure, 280℃ and GHSV of 100h^-1, the conversion of dimethyl ether and the selectivity of HMB could reach 76.36% and 25.1%, respectively. With the increase of MnO2 loading, the MnO2 in the catalyst becomes gradually a crystal structure, and the strong acid sites on the surface of catalyst increases, but the Bronted acid numbers of the catalyst firstly increase then decrease. The MnOJHBeta catalyst with a MnO2 loading of 10% by mass has a suitable surface acidity, which is favorable for the formation of HMB.