摘要
以硝酸镁、醋酸镁为前身物通过浸渍法制备了不同系列MgO/HZSM5催化剂用XRD、XPS方法研究了MgO在HZSM5上的分散状态用NH3TPD方法考察了催化剂的酸性用常压连续流动微型反应装置考察MgO/HZSM5在甲苯甲醇烷基化反应中的催化性能.发现前身物不同MgO在HZSM5上的分散状态也不同催化剂的活性和选择性与MgO分散状态密切相关.MgO负载量相同时在以硝酸镁为前身物制备的催化剂中MgO在HZSM5内外表面均有分散催化剂的对位选择性较高而活性较低;在以醋酸镁为前身物制备的催化剂中MgO较多分布在HZSM5外表面催化剂的活性较高但选择性较低.使用醋酸镁为前身物通过二次浸渍和高温水汽处理适当改变MgO在分子筛表面的分布并使孔道窄化可在活性降低较少的情况下显著提高催化剂对二甲苯选择性.
Two series of MgO /HZSM-5catalysts were prepared by impregnating HZSM-5with solution of Mg (NO 3 ) 2 and Mg (CH 3 COO) 2 .The structures of the samples were c haracterized by XRD and XPS,and the a cidi-ty was determined by NH 3 -TPD.The catalytic behavior of MgO /HZSM-5in the reaction of toluene methylation was investigated on a continuous flo w micro-apparatus under atmospheric pressure.It was found that the disp ersion of MgO was related to the precursor of MgO and had an important effect on the behavior of MgO /HZSM-5cata-lyst.MgO disperses both on the internal surface and on the external surfa ce of HZSM-5in the catalysts prepare d with Mg (NO 3 ) 2 as the precursor of MgO,therefore th e para-selectivity of the catalyst i s higher and the activity is lower.However MgO mainly deposits o n the external surface of HZSM-5in th e catalysts prepared with Mg (CH 3 COO) 2 ,and the activity of catalysts is hig her and the para-selectivity is lowe r.By secondary impregnation and hydrothermal treatment MgO /HZSM-5catalyst with relatively high activity and high para-selectivity wa s ob-tained.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2001年第11期966-971,共6页
Acta Physico-Chimica Sinica
基金
国家重点基础研究发展规划项目G2000077503
自然科学基金重点资助项目29733080~~
