金属锌改性HZSM-5催化的固定床反应器中甲醇芳构化工艺条件优化研究

Optimization of the conditions for the methanol to aromatics( MTA)process with a HZSM-5 zeolite catalyst modified by zinc in fixed bed

通过等体积浸渍法制备了Zn改性的HZSM-5催化剂,并在连续流动固定床反应器上研究了Zn-HZSM-5催化剂的甲醇芳构化性能。结合X射线衍射(XRD)、吡啶吸附傅立叶变换红外光谱(Py-IR)、N2吸附-脱附方法对金属锌改性HZSM-5催化剂进行了表征。考察了Zn负载量和操作条件对甲醇芳构化反应的影响,并针对甲醇芳构化反应过程中强放热导致催化剂床层温升过高而使催化剂结焦失活的现象,探讨了催化剂床层温度控制的影响因素。研究结果表明,锌改性HZSM-5的最佳负载量(质量分数)区间为2%~3%;2.5%Zn-HZSM-5催化的固定床反应器中甲醇芳构化的最优工艺条件为常压,400~430℃,甲醇质量空速小于2 h-1;降低甲醇水溶液中甲醇物质的量比、加大气相空速中氮气分压均能降低催化剂床层的温升。

HZSM-5 zeolite catalysts modified by zinc have been prepared by incipient wetness impregnation method,and the performance of the Zn-HZSM-5 catalyst in the methanol to aromatics( MTA) reaction was studied in a continuous flow fixed bed reactor. The catalyst crystal structure,surface acidity,and specific surface area were characterized,respectively,by XRD,FT-IR,and BET. The effects of zinc loadings and operating conditions on the MTA reaction were investigated,and temperature control of the catalyst bed,which is related to the coking rate of the catalyst resulting from this strongly exothermic reaction,was also studied. The results demonstrated that the optimal zinc loading weight ratio of Zn-HZSM-5 was 2%-3%( mass fraction). Optimal operating conditions for the2. 5% Zn-HZSM-5 catalyst were found to be atmospheric pressure,400-430 ℃,and methanol weight hourly space velocity less than 2 h- 1. The raising temperature of the catalyst bed can be reduced by decreasing the molar ratio of methanol in aqueous methanol and increasing the nitrogen partial pressure in the gas phase space velocity.