微乳液法制备无模板剂NaA分子筛

以十六烷基三甲基溴化铵(CTAB)为表面活性剂、正丁醇为助表面活性剂,采用微乳液法制备了无模板剂NaA分子筛,考察了微乳液组成、晶化温度与晶化时间对NaA分子筛形成的影响。实验结果表明,m(CTAB)∶m(正丁醇)=1∶2时为最佳微乳区;NaA分子筛的最佳合成条件:m(合成液)∶m(CTAB+正丁醇)=0.1000,晶化温度为90℃,晶化时间为4h。在合成液配方和晶化时间相同的条件下,与传统水热合成法制备的NaA分子筛相比,晶化温度降低,且NaA分子筛的平均粒径由1.5μm减小到270nm。提出了微乳液法制备NaA分子筛的反应机理:在反应初期,微乳液为NaA分子筛成核提供了一个微空间;当NaA分子筛成核完成后,通过表面活性剂的吸附作用影响NaA分子筛粒子的生长。

Synthesis of Template-Free NaA Molecular Sieve by Microemulsion

Template-free NaA molecular sieve was prepared by microemulsion method with cetyltrimethylammonium bromide(CTAB)as surfactant and n-butanol as cosurfactant.Effects of microemulsion composition,crystallization temperature and time on formation and growth of NaA molecular sieve crystals were investigated.When m(CTAB)∶m(n-butanol)is 1 ∶2,the preferred single phase microemulsion forms.The optimal synthesis conditions are as follows:m(synthesis solution)∶m(CTAB+n-butanol)0.1,crystallization temperature 90 ℃ and time 4 h.Comparing with hydrothermal process,crystallization temperature of microemulsion method reduces and average particle size of obtained NaA molecular sieve decreases from 1.5 μm to 270 nm.Reaction mechanism for preparation of molecular sieve was considered.The microemulsion provides micro-space for nucleation of molecular sieve in initial stage of crystallization,and then growth of molecular sieve crystals is promoted by adsorption of surfactants in microemulsion.