摘要
多级孔沸石分子筛的结构性质及其催化性能是近年来分子筛研究的热点.本文采用蒸汽辅助晶化的方法制备了多级孔ZSM-5沸石分子筛,采用NH3程序升温脱附和原位吸附红外光谱等方法研究了其表面酸性质,用邻二甲苯异构化反应考察了其催化性能.结果表明,多级孔结构分子筛的结晶度和总酸量有所下降,但Lewis酸中心却有所增加.进一步研究发现,多级孔结构分子筛的外表面酸中心数量远高于常规分子筛,从而证实了多级孔结构可以将更多的酸中心暴露到外表面;而外表面酸中心数量的增多和扩散传质的改善是多级孔ZSM-5分子筛在邻二甲苯异构化反应中具有更高催化活性和对二甲苯产率的重要原因.
Surface acid sites of hierarchical mesoporous ZSM-5 zeolite synthesized by steam-assisted crystal- lization were characterized by NH3 temperature-programmed desorption and in-situ infrared spec- troscopy. Compared with the conventional ZSM-5 zeolite, the hierarchical ZSM-5 zeolite had a lower concentration of surface acid sites. However, the hierarchical structure had more Lewis acid sites and, more importantly, much more external active sites as confirmed by 2,6-di-tert-butylpyridine infrared spectroscopy. Such hierarchical structure exposed more acid sites on the external surface, which subsequently lead to higher catalytic activity in reactions involving bulky molecules, such as o-xylene isomerization.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第7期1429-1433,共5页
基金
supported by the National Basic Research Program of China(973 Program,2009CB623506)
the China Postdoctoral Science Foundation Project(2012M510101)
the Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure(SKL201208SIC)
the Shanghai Postdoctoral Scientific Program(12R21422000)~~