ZSM-5、ZSM-57分子筛和丝光沸石间的转晶规律

考察了硅铝比、碱度、有机胺模板剂、晶化时间及温度等合成条件对ZSM-5、ZSM-57 分子筛和丝光沸石之间相互转晶的影响. 发现较高的碱度、较长的晶化时间有利于合成丝光沸石；较低的碱度、较高的诱导晶化温度、较长的晶化时间有利于合成低硅铝比的ZSM-57 分子筛；合成低硅铝比的ZSM-5分子筛则需要在能合成丝光沸石和ZSM-57 分子筛的碱度区间内精确调节碱度, 缩短晶化时间、降低诱导晶化温度、加入适当晶种, 有利于合成低硅铝比的ZSM-5 分子筛. 合成条件稍微改变, 会导致各种沸石之间发生转晶, 晶化产物出现两种或两种以上的晶型.

Crystal Transformation among ZSM-5, ZSM-57 and Mordenite

The crystal transformation among ZSM-5, ZSM-57, and mordenite was studied under different conditions, such as SiO_2/Al_2O_3 molar ratio, alkalinity, n-butylamine template, crystallization time, and temperature. The results showed that higher alkalinity and longer crystallization time were of benefit to mordenite; lower alkalinity and higher induction temperature of crystallization were in favor of ZSM-57 with low n(SiO_2)/n(Al_2O_3) ratio; alkalinity was required to be adjusted accurately to synthesize ZSM-5 with low n(SiO_2)/n(Al_2O_3) ratio, shortening of crystallization time, decrease in induction temperature of crystallization, and the addition of seed crystal were all in favor of ZSM-5 with low n(SiO_2)/n(Al_2O_3) ratio. A slight change in the above conditions would result in the transformation among the three crystals, and two or more crystal phases could be observed in the products.