几种分子筛的转晶和混晶的控制及单一晶体的优化合成

 以六亚甲基亚胺作模板剂，在配料比一定的情况下，详细考察了反应温度和反应时间对MCM－22，ZSM－5，ZSM－35和丝光沸石分子筛成晶的影响．结果表明，MCM－22的最佳合成温度在低温区，ZSM－35易在提高反应温度或延长反应时间时形成，而作为中间相的ZSM－5和丝光沸石则在反应温度与反应时间合理匹配时才能以单一相生成．同时，探讨了晶种的加入对产物晶相的影响．在特定的温度和时间区间，能够合成出比例可控的ZSM－35＋MCM－22混晶，ZSM－5＋ZSM－35混晶和ZSM－35＋丝光沸石混晶，并从分子筛孔道和结构单元的特点出发，就转晶发生对温度和时间的依赖性作了解释．

Control of Crystal Transformation and Mixed Crystals of Some Zeolites and Optimum Conditions for Synthesis of Monocrystal Zeolites

The influence of reaction temperature and reaction time on the crystallization of zeolites MCM-22, ZSM-5, ZSM-35 and mordenite was studied under the moderate ratio of silicon to aluminum using hexamethyleneimide as a template. MCM-22 was found to be an easily formed phase in this synthetic system because it appeared in the early stage of the crystallization process at both higher temperature and lower temperature. Whereas MCM-22 zeolite partially transformed to ZSM-5 and ZSM-35 with prolonging the reaction time at higher temperature, and finally transformed to ZSM-35. With this rule, the co-crystalline zeolite of MCM-22 and ZSM-35 was easily produced. The similar results of ZSM-5 and ZSM-35 mixed crystals could be achieved by varying reaction time at appropriate temperature. Upon analyzing the crystallization area of zeolites MCM-22, ZSM-5, ZSM-35 and mordenite, it is reasonable that the crystal transformations between these zeolites are prone to happen in this synthetic system, because all the zeolites have the same 5-ring sub-units, which bring little resistance to the reconstruction of frameworks, and the stability changing of the channel systems propels the occurrence of alternation of the linking modes of 5-ring units, leading to the formation of other type zeolites.