菱钾沸石中铝在不等价四面体位上分布的~29Si MAS NMR谱研究  

Aluminium Partition on Crystallographically Unequivalent Tetrahedral Sites in Zeolite Offretite Studied by^(29)Si MAS NMR.

作　　者：陈铁红[1] 王凯旋[1] 罗挽兰 王敬中[1] 李赫咺[1] 丁大同[2] 胡澄[3] 

机构地区：[1]南开大学化学系,天津300071 [2]南开大学物理系,天津300071 [3]南京大学固体微结构实验室,南京210008

出　　处：《Chinese Journal of Chemical Physics》1996年第1期49-53,共5页化学物理学报（英文）

摘　　要：根据菱钾沸石^(29)Si MAS NMR实验讨论了骨架Si/Al比(R)和Al在两种不等价四面体位分配比率(r)二者之间必须满足的关系,对于合成原粉,Al择优占据T_B位;用(NH_4)_2SiF_6同晶取代脱铝,T_B位上的Al择优解脱.In zeolite off retite, there are two kinds of crystallographically unequivalent tetrahedral sites (12 TA and 6 TB sites per unit cell). the chemical shift difference due to site inequivalence(5. 3ppm) is almost the same as the effect of aluminium in the first coordination sphere of silicon(5. 5ppm), so it is a very good approximation to consider a complete overlap of the two sets of 29 Si MAS NMR signals corresponding to TA and TB sites. A relationship based on Si MAS NMR spectrum between framework Si/ Al ratio(R) and the aluminium partition ratio(r) is proposed. When the framework Si/Al ratio of the sample is obtained by chemical analysis, the aluminium partition in parent and (NH4)2 SiF6 treated zeolite offretite can be calculated by the relationship mentioned above. It is concluded that for parent samples, Al atoms prefer TB sites, while dealuminated with (NH4)2SiF6, Al on TB sites are more easily to be substituted by Si.

关 键 词：魔角旋转 菱钾沸石 分子筛 铝 硅 NMR 

分 类 号：O647.33[理学—物理化学] O641.133[理学—化学]