镁选择改性ZSM-5催化甲苯甲基化制对二甲苯  

Selective Toluene Methylation to p-Xylene Catalyzed by ZSM-5 Modified With Magnesium Compounds

作　　者：赵岩[1] 马新会 郑远馨 夏云生[1] 任冬梅[1] 郭新闻[2] ZHAO Yan;MA Xinhui;ZHENG Yuanxin;XIA Yunsheng;REN Dongmei;GUO Xinwen(College of Chemistry and Chemical Engineering,Bohai University,Jinzhou 121013,China;State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]渤海大学化学化工学院,辽宁锦州121013 [2]大连理工大学化工学院精细化工国家重点实验室,辽宁大连116024

出　　处：《石油学报（石油加工）》2021年第3期469-477,共9页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：国家自然科学基金项目(21676028);辽宁省科技厅研究项目(2019-ZD-0506)资助。

摘　　要：为提高甲苯甲基化产物中对二甲苯选择性,笔者提出了一种MgO选择性修饰ZSM-5分子筛纳米粒子外表面的新方法——分子占位选择修饰法,该方法以对二甲苯为占位分子,预先占满全部孔道,继而采用合适的温度选择性脱除对二甲苯,再用乙酸镁水溶液常压下等体积浸渍ZSM-5。采用X射线荧光光谱(XRF)、X射线衍射(XRD)、低温N 2物理吸附-脱附(BET)、氨气程序升温脱附(NH 3-TPD)、吡啶吸附红外光谱(Py-FT-IR)等分析方法对催化剂的组成、晶相结构、比表面积、孔体积、酸性等进行表征。分子占位选择修饰法可保持微孔道畅通和孔道内酸中心不受影响,从而保持催化剂的高活性。该方法从H-ZSM-5母体出发共经历6个连贯的步骤制得MgO-ZSM-5催化剂,其中,占位分子对二甲苯的选择和脱除温度的控制最为关键。结果表明,分子占位选择修饰法制备催化剂的对二甲苯选择性(s(PX))和甲苯转化率(x(T))分别可达92.6%和33.6%,与常压浸渍法(s(PX)=83.4%,x(T)=28.7%)和负压浸渍法(s(PX)=68.3%,x(T)=24.5%)相比,其具有更高的对二甲苯选择性和反应活性。In order to improve the selectivity of p-xylene product in toluene methylation and maintain high activity of catalyst,a new method to modify the external surface of ZSM-5 nano-particles with magnesium acetate was studied.X-ray fluorescence(XRF),X-ray diffraction(XRD),N 2 adsorption-desorption(BET),ammonia temperature programmed desorption(NH 3-TPD)and pyridine adsorption FT-IR spectroscopy(Py-FT-IR)were used to characterize the composition,structure phase,specific surface area,microporous volume and acidity of catalysts.In this method,micropores are previously occupied by p-xylene.Then p-xylene was selectively removed at appropriate temperature,and ZSM-5 particles were impregnated with magnesium acetate aqueous solution under atmosphere pressure by incipient-wetness impregnation method,which does not inhibit micropores and the acid centers inside the channels,resulting in higher p-xylene selectivity and catalytic activity.With H-ZSM-5 as matrix,the modified catalysts are obtained in six consecutive steps,where the most critical issues are the selection of placeholder molecules and the temperature for selective removal of the molecules.Results show that the p-xylene selectivity(s(PX))and toluene conversion(x(T))of the catalyst made by selective modification method are 92.6%and 33.6%,respectively,thus showing higher p-xylene-selectivity and better activity in comparison to the ones made by the atmospheric pressure impregnation method(s(PX)=83.4%,x(T)=28.7%)and negative pressure impregnation method(s(PX)=68.3%,x(T)=24.5%).

关 键 词：纳米粒子 ZSM-5 分子筛 MGO 选择性 甲苯甲基化 对二甲苯 

分 类 号：TQ241.1[化学工程—有机化工]