本文报道关于HZSM-5分子筛中L酸的形成及其存在形式的研究。直接法合成的HZSM-5分子筛经系列温度培烧脱羟,B酸中心向L酸中心转化,并且在600-700℃有一突变温域。系列温度焙烧过的HZSM-5分子筛样品经乙酰丙酮浸泡后进行^(27)Al NMR检测,...本文报道关于HZSM-5分子筛中L酸的形成及其存在形式的研究。直接法合成的HZSM-5分子筛经系列温度培烧脱羟,B酸中心向L酸中心转化,并且在600-700℃有一突变温域。系列温度焙烧过的HZSM-5分子筛样品经乙酰丙酮浸泡后进行^(27)Al NMR检测,发现非骨架铝的数量极少;^(29)Si MAS NMR及X射线衍射实验则说明分子筛骨架上的铝量没有明显变化。没有迹象表明HZSM_5分子筛脱羟形成L酸与脱铝是同步发生的。从而可以否定L酸与脱铝是同步发生的。从而可以否定L酸与非骨架铝的必然联系。论证了与L酸中心所关系的铝离子仍处在HZSM-5分子筛的骨架之上。^(27)Al MAS NMR观测表明随着L酸的生成,与之关系的这一部分骨架铝的配位状态发生了重大的变化。展开更多
The formation mechanism of mesoporous molecular sieve materials MCM-41 in differ-ent synthetic systerns has been studied systendcally In the Na2O-(CTMA)2O-SiO2-H2O system,it is found that liquid-crystal templating mec...The formation mechanism of mesoporous molecular sieve materials MCM-41 in differ-ent synthetic systerns has been studied systendcally In the Na2O-(CTMA)2O-SiO2-H2O system,it is found that liquid-crystal templating mechanism should be that silica first forms silicated mi-celle with surfactant cation, then silica/CTMA+ micelle polylnerizes with each other forming thehexagonal mesophase. The experimental results in the TMAOH-SiO2-CTMABr-H2O system sup-ports the mechanism proposed for a surfactant-silica system from the lamellar to the hexagonalmesophase. Therefore, it is found that the formation mechanisrns of MCM-41 molecular sieves arenot the same under different synthetic conditions and in different synthetic systems.展开更多
文摘本文报道关于HZSM-5分子筛中L酸的形成及其存在形式的研究。直接法合成的HZSM-5分子筛经系列温度培烧脱羟,B酸中心向L酸中心转化,并且在600-700℃有一突变温域。系列温度焙烧过的HZSM-5分子筛样品经乙酰丙酮浸泡后进行^(27)Al NMR检测,发现非骨架铝的数量极少;^(29)Si MAS NMR及X射线衍射实验则说明分子筛骨架上的铝量没有明显变化。没有迹象表明HZSM_5分子筛脱羟形成L酸与脱铝是同步发生的。从而可以否定L酸与脱铝是同步发生的。从而可以否定L酸与非骨架铝的必然联系。论证了与L酸中心所关系的铝离子仍处在HZSM-5分子筛的骨架之上。^(27)Al MAS NMR观测表明随着L酸的生成,与之关系的这一部分骨架铝的配位状态发生了重大的变化。
文摘The formation mechanism of mesoporous molecular sieve materials MCM-41 in differ-ent synthetic systerns has been studied systendcally In the Na2O-(CTMA)2O-SiO2-H2O system,it is found that liquid-crystal templating mechanism should be that silica first forms silicated mi-celle with surfactant cation, then silica/CTMA+ micelle polylnerizes with each other forming thehexagonal mesophase. The experimental results in the TMAOH-SiO2-CTMABr-H2O system sup-ports the mechanism proposed for a surfactant-silica system from the lamellar to the hexagonalmesophase. Therefore, it is found that the formation mechanisrns of MCM-41 molecular sieves arenot the same under different synthetic conditions and in different synthetic systems.
