摘要
用(NH_4)_2SiF_6类质同晶取代法得到Si/Al比6～15的高结晶度的富硅丝光沸石。系统地描述了各种制备条件对丝光沸石抽铝补硅作用的影响,并对造成这些影响的结构因素进行了讨论。用多种实验手段对一系列富硅丝光沸石进行表征,发现它们的晶胞参数、T-O-T反对称伸缩振动频率、热稳定性和表面酸性随硅铝比增加而有规律的变化。考察了富硅丝光沸石对异丙苯裂解、正丙醇脱水、甲笨歧化和二甲苯异构化反应的催化性能,并与沸石的酸性特征进行了关联。
Highly crystalline mordenites with Si/Al ratio 6-15 have been obtained by isomorphous substitation of Si for Al with (NH4)2SiF6 solution. The influence of (NH4)2SiF6 concentration, SiF6=/Al(zeol) ratio, reaction temperature and time on the properties of the mor-denite products was studied systematically, and the probable reason for such influence was discussed with reference to the framework structure of mordenite.A series of mordenite products with different Si/Al ratios were characterized with XRD, IR, DTA and NH3-TPD methods. It is found that the unit cell parameters, T-O-T asymmetric stretch frequency, thermal stability and surface acidity of the samples vary regularly with the Si/Al ratio of the zeolites. The catalytic properties of the mordenites for cumene cracking, propanol dehydration, toluene disproportionation and o-xylene isomerization were investigated in a micro-reactor. The variation of the catalytic activity and selectivity of the samples in these reactions with Si/Al ratio was correlated with the surface acidity of the mordenites.
基金
国家自然科学基金
