不同双模板剂对ZSM-5分子筛催化剂形貌的影响

固定硅源、铝源和水用量,采用复合模板剂,其中一种模板剂为四丙基氢氧化铵,另一种模板剂为有机胺(乙二胺、1,6-己二胺、异丙胺或三乙胺),通过改变第二种模板剂用量和类型,制备系列ZSM-5分子筛催化剂。采用XRD和SEM进行表征,考察不同双模板剂对ZSM-5分子筛催化剂晶体结构和形貌的影响。结果表明,不同双模板剂合成的产物均为纯相ZSM-5分子筛,且具有较高的结晶度,晶粒外形保持不变,但晶粒尺寸有很大差异,顺序为:四丙基氢氧化铵+三乙胺四丙基氢氧化铵+异丙胺四丙基氢氧化铵+1,6-己二胺四丙基氢氧化铵+乙二胺,可见,只改变模板剂种类而不改变硅源、铝源和水的用量,即可合成相对结晶度高、外形相同但晶粒尺寸不同的ZSM-5分子筛催化剂。

Morphological effects of different double templates on ZSM-5 molecular sieve catalysts

A series of ZSM-5 molecular sieve catalysts were synthesized by fixing the dosage of silicon,aluminum and water,and using double templates,i.e.,tetrapropylammonium hydroxide(TPAOH) and organic amine (ethylenediamine,1,6-hexanediamine,isopropylamine or triethylamine),changing the sort and dosage of organic amines.The effects of different double templates on crystal structure and morphology (size and shape) of the as-synthesized ZSM-5 molecular sieve catalysts were studied by means of X-ray powder diffraction and scanning electron microscopy.The results showed that ZSM-5 molecular sieve catalysts synthesized by different double templates were pure-state ZSM-5 molecular sieves with high crystallinity,the same grain shape but much different grain size.The order of grain size vs.templates was as follows:TPAOH+triethylamine>TPAOH+isopropylamine>TPAOH+1,6-hexanediamine>TPAOH+ethylenediamine.It is concluded that ZSM-5 molecular sieve catalysts of high crystallinity,the same grain shape but different grain size could be synthesized by varying types of double templates while fixing the quantity of silicon,aluminum and water.