甲醇制丙烯过程中水热处理对ZSM-5分子筛上积炭的影响

在固定床中对不同水热老化条件（不同水处理量，460-500 ℃）处理后的催化剂进行性能考评，实验条件如下：480 ℃，甲醇空速3 h-1，甲醇分压30 kPa，反应时间12 h、24 h、48 h。孔结构测试结果和甲苯扩散系数的测定结果显示不同的水热条件会产生两类介孔：温和的温度和水处理量会产生与催化剂外表面联通的向外开口的介孔，而苛刻条件（高温，高水处理量）会导致大孔或被限制在催化剂内部的介孔的产生。热重分析结果显示含向外开口介孔的催化剂抗积炭能力强，考评实验结果则表明这种催化剂的丙烯选择性更高。

Effect of Hydrothermal Treatment on Suppressing Coking of ZSM-5 Zeolite during Methanol-to-Propylene Reaction

Fresh ZSM-5 zeolite catalysts were pretreated at 460 ℃ and 500 ℃ with various cumulative amount of water feed (CAWF) in a fixed bed reactor. The catalytic process was carried out under the following conditions: a temperature of 480 ℃; a methanol WHSV of 3 h-1; a methanol partial pressure of 30 kPa; and a time on stream of 12 h, 24 h and 48 h, respectively. The BET parameters of catalysts and diffusion coefficients of toluene showed that there were two types of mesopores generated under different hydrothermal conditions. Mild temperature and moderate CAWF conditions led to external open mesopores which could be entered from the external surface of the zeolite, while a high temperature or a high CAWF condition resulted in the generation of macropores or internal isolated mesopores, which were occluded in the microporous matrix. The TGA results showed that catalyst with external open mesopores had good ability to resist coke accumulation and good performance on propylene selectivity, while the internal isolated mesopores did no contribute to the increased diffusivity of reactants and products.