甲醇制对二甲苯联产低碳烯烃改性ZSM-5催化剂在流化床中的反应性能

在流化床反应器中，对Zn、Si和P改性的ZSM-5催化剂的甲醇制对二甲苯联产低碳烯烃的反应性能进行了研究。采用X射线衍射（XRD）、BET比表面积、扫描电镜（SEM）、NH₃-程序升温脱附（NH₃-TPD）等手段进行表征分析。结果表明，Zn改性使得催化剂酸强度降低，中强酸酸量增加，对二甲苯和低碳烯烃选择性都随之提高；一定量的硅沉积改性在降低催化剂外表面酸量的同时缩小孔口，浸渍适量P能够调变分子筛的酸中心强度和酸量，这都能够提高对二甲苯选择性。在流化床反应器中甲醇制对二甲苯联产低碳烯烃反应结果表明，3Zn-3Si-3P/ZSM-5催化剂在温度425℃、常压、反应时间40min、空速1h^-1的条件下，对二甲苯在二甲苯中的选择性为76.0%，C₂~C₄低碳烯烃选择性为24.4%，特别是芳烃和C₂~C₄低碳烯烃的总选择性高达92.2%。

Performance of modified ZSM-5 zeolite in fluidized bed for co-production of low-carbon olefins and p-xylene from methanol

In a fluidized bed reactor, the reaction performance of Zn, Si and P-modified ZSM-5 catalysts for conversion of methanol to p-xylene and co-production of lower olefins was studied. XRD, BET, SEM, and NH₃-TPD etc. were used for the characterization analysis. The results showed that the modification by Zn decreased the acid strength of the catalyst, increased the amounts of medium and strong acids, and increased the selectivities of both p-xylene and lower olefins. The modification by deposition of silicon reduced the pore size as well as the amount of acid on the outer surface of the catalyst. Immersion of an appropriate amount of phosphorus can modulate the strength of the acid center of the zeolite and the amount of acid. The reaction results of converting methanol to p-xylene in the fluidized bed reactor to produce low-carbon olefins showed that at the temperature of 425 ℃, normal pressure, reaction time of 40min, and space velocity of 1h^-1, the 3Zn-3Si-3P/ZSM-5 catalyst gave the selectivities of p-xylene in xylene and C₂—C₄ lower olefins were 76% and 24.4%, respectively. In particular, the total selectivity of aromatics and C₂—C₄ lower olefins was as high as 92.2%.