沉积法和外延生长法制备SiO_(2)/ZSM-5的催化甲苯甲基化性能  

Toluene Methylation Catalyzed by SiO_(2)/HZSM-5 Modified Through Deposition and Epitaxial Growth

作　　者：赵岩[1] 马新会 陈雨 夏云生[1] 任冬梅[1] 郭新闻[2] ZHAO Yan;MA Xinhui;CHEN Yu;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2期289-297,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：为提高甲苯甲基化催化剂的对二甲苯选择性,分别采用化学气相沉积(CVD)法、化学液相沉积(CLD)法放大制备了SiO_(2)表面沉积型SiO_(2)/ZSM-5催化剂,采用外延生长(EPG)法制备了核壳型SiO_(2)/ZSM-5催化剂。采用X射线荧光光谱(XRF)、X射线衍射(XRD)、低温N2物理吸附-脱附(BET)、扫描电镜(SEM)、氨气程序升温脱附(NH3-TPD)、热重(TG)等分析方法对催化剂的组成、晶相结构、比表面积、酸性和积炭等进行系统表征。结果表明:当SiO_(2)沉积质量分数为9.48%时,CVD法制备的SiO_(2)/ZSM-5催化剂上对二甲苯选择性最高达到85%,继续增加SiO_(2)沉积量,对二甲苯选择性逐渐降低;CLD法制备的SiO_(2)/ZSM-5催化剂上对二甲苯选择性最高达到91%;EPG法制备的核壳结构SiO_(2)/ZSM-5催化剂上的对二甲苯选择性最高接近98%。甲苯甲基化反应200 h后,CVD法、CLD法和EPG法制备的SiO_(2)/ZSM-5催化剂上的积炭量依次为3.24%、5.22%和6.29%。由此可见:在相同SiO_(2)含量(w(SiO_(2))约为6%或9%或12%)条件下,就提高对二甲苯选择性而言,EPG法制备的SiO_(2)/ZSM-5催化剂最优,CLD法稍好于CVD法;此外,SiO_(2)/ZSM-5催化剂的容炭能力由高到低的顺序依次为EPG法、CLD法、CVD法。In order to improve the selectivity of p-xylene in toluene methylation,surface modified SiO_(2)/HZSM-5 catalysts were prepared by chemical vapor deposition(CVD)and chemical liquid phase deposition(CLD),while core-shell SiO_(2)/HZSM-5 catalyst was prepared by epitaxial growth(EPG)method.X-ray fluorescence(XRF),X-ray diffraction(XRD),N2 adsorption-desorption(BET),scanning electron microscopy(SEM),ammonia temperature programmed desorption(NH3-TPD)and thermogravimetry(TG)were used to systematically characterize the composition,phase structure,specific surface area,acidity and carbon deposition of these catalysts.When the mass fraction of SiO_(2) deposition is 9.48%,the p-xylene selectivity of the SiO_(2)/HZSM-5 catalyst prepared by CVD method is up to 85%.After that,this selectivity is gradually decreasing along with the increase of SiO_(2) deposition content.Additionally,the p-xylene selectivity of the SiO_(2)/HZSM-5 catalyst prepared by CLD method is up to 91%,while the p-xylene selectivity of the core-shell structure SiO_(2)/HZSM-5 catalyst prepared by EPG is as high of 98%.When reaction time over 200 h,the carbon deposition of SiO_(2)/HZSM-5 catalysts prepared by CVD,CLD and EPG are 3.24%,5.22%and 6.29%respectively.It can be seen that under the same amount of SiO_(2)(w(SiO_(2))of 6%,9%and 12%),EPG method is optimal,and CLD method is slightly better than CVD method in terms of improving the p-xylene selectivity.In addition,the carbon capacity of the three catalysts is as following from high to low:core-shell structure catalyst prepared by EPG,surface deposition catalysts prepared by CVD and CLD.

关 键 词：纳米粒子 ZSM-5 分子筛 二氧化硅 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]