摘要
采用浸渍法制备了系列MgO修饰的HZSM-5分子筛催化剂,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、NH_(3)程序升温脱附(NH_(3)-TPD)、吡啶红外(Py-IR)等方法对修饰前后的HZSM-5分子筛催化剂进行表征,并在固定床反应器上对催化剂的性能进行评价.结果表明:MgO的修饰并未对HZSM-5分子筛的晶体结构有明显影响,但是部分MgO优先覆盖了分子筛表面的强酸位,从而降低了分子筛的酸强度,并改变了B酸/L酸比例;同时由于MgO堵塞部分孔道造成分子筛比表面积降低,进一步降低了分子筛表面酸性位的数量,影响甲苯甲醇烷基化反应性能和产物分布.MgO修饰后的HZSM-5分子筛,虽然使甲苯转化率降低,抑制了甲苯歧化反应、深度烷基化反应和缩聚反应的发生,但是有利于对二甲苯和乙基甲苯的生成,表现出一定的择形催化性能.
A series of MgO-modified HZSM-5 zeolite catalysts were prepared with an impregnation method.The HZSM-5 zeolite catalysts with and without modification were characterized using X-ray diffraction(XRD),scanning electron microscope(SEM),NH_(3) temperature-programmed desorption(NH_(3)-TPD)and pyridine infrared(Py-IR),and the performance of the catalysts was evaluated on a fixed bed reactor.The results showed that the modification with MgO had no significant effect on the crystal structure of the HZSM-5 zeolites,but some MgO preferentially covered the strong acid sites on the surface of the zeolites,thereby reducing the acid strength of the catalysts and changing the ratio of B acid/L acid.At the same time,the specific surface area was reduced due to the blockage of part of the pores by MgO,which further reduced the number of acid sites on the zeolite surface,and affected the performance and product distribution of alkylation reaction of toluene with methanol.However,the HZSM-5 zeolites modified with MgO reduced the conversion rate of toluene and inhibited the toluene disproportionation,deep alkylation and polycondensation reactions,while it was conducive to the formation of p-xylene and ethyl toluene,showing a certain shape-selective catalytic performance.
作者
余姮
董焕能
刘茜桐
胡新瑞
王叶霏
连奕新
YU Heng;DONG Huanneng;LIU Xitong;HU Xinrui;WANG Yefei;LIAN Yixin(National Engineering Laboratory for Green Chemical Productions of Alcohols-Ethers-Esters,College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361102,China)
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
2023年第1期78-84,共7页
Journal of Xiamen University：Natural Science
关键词
HZSM-5分子筛
表面修饰
烷基化
酸碱性
择形催化
HZSM-5 zeolite
surface modification
alkylation
acid-base property
shape-selective catalysis
