论文部分内容阅读
分别以硅凝胶和正硅酸乙酯为硅源，通过改变晶化时间合成了系列ＳＡＰＯ５分子筛．用ＸＲＤ，ＭＡＳＮＭＲ和ＳＥＭ对分子筛的结构和形貌进行了表征．结果表明，以硅凝胶为硅源时，凝胶中的铝有３种面体配位状态．加热晶化很容易使凝胶转化为ＳＡＰＯ５分子筛，合成物的晶形更加规则．在４８ｈ内，延长晶化时间有助于硅进入分子筛骨架，使残余的Ａｌ２Ｏ３·Ｈ２Ｏ进一步反应，使骨架硅和铝的面体配位环境更加对称；超过４８ｈ后，硅开始游离出分子筛骨架，并使部分ＳＡＰＯ５转化为ＳＡＰＯ３４．以正硅酸乙酯为硅源时，硅和铝的反应活性均较低，凝胶中ＡｌＰＯ４及Ａｌ２Ｏ３·Ｈ２Ｏ的量均比四面体配位铝的量大．只有当晶化时间超过４８ｈ时，反应物中Ａｌ２Ｏ３·Ｈ２Ｏ才能完全转化．在此反应体系中，延长晶化时间有助于ＳＡＰＯ５的生成，使分子筛骨架硅的取代量更大，晶形更加规则，骨架铝的对称性更好．
Silica gel and tetraethyl orthosilicate were used as the silicon source respectively to synthesize a series of SAPO5 molecular sieves by changing the crystallization time. The structure and morphology of the molecular sieve were characterized by XRD, MAS NMR and SEM. The results show that the silica gel as a silicon source, the aluminum gel has three kinds of coordination state. Heating crystallization is easy to make the gel into SAPO 5 molecular sieve, the crystal form of the more regular. In 48h, prolonging the crystallization time helps the silicon to enter the framework of the molecular sieve and make the residual Al2O3 · H2O react further to make the framework coordination environment of the framework silicon and aluminum more symmetrical. After more than 48h, the silicon begins to free the molecular sieve framework, and So that some SAPO 5 into SAPO 34. When tetraethylorthosilicate is used as the silicon source, the reactivity of silicon and aluminum is low, and the amount of AlPO4 and Al2O3 · H2O in the gel is larger than the amount of tetrahedral coordinated aluminum. Only when the crystallization time more than 48h, the reaction of Al2O3 · H2O can be completely converted. In this reaction system, prolonging the crystallization time contributes to the formation of SAPO-5, resulting in a larger substitution amount of silicon in the molecular sieve framework, more regular crystal form and better symmetry of framework aluminum.