材料期刊网

考察了用四乙基溴化铵-氟化钠复合模板剂合成β沸石的结晶动力学. 结果表明:其晶化曲 线为典型的S形曲线; 成核活化能En=65.79 kJ/mol,生长活化能Ec=91.49 kJ /mol; 与单纯的四乙基溴化铵模板剂体系相比,本体系成核诱导期较短,生长速率较快; n (NaF)/n(SiO2)值增大时,晶化诱导期缩短,成核速率加 快,但氟化钠量过高时,成核速率反而降低,n(NaF)/n(SiO2)最佳值为0.10～0.17; 较高的OH-/SiO2比有利于缩短晶化诱导期.

The effects of various synthesis parameters, such as n(SiO2) /n(Al2O3), n(NaF)/n(SiO2), and n(OH-)/n(SiO2) as well as crystallization temperature, on the crystallization behavior of zeolite β synt hesis have been investigated. The results showed that the crystallization temper ature has obvious influence on the crystallization rate of zeolite β. The induc tion period of the crystallization could be shortened and the nucleation rate co uld be accelerated in TEABr(Et4NBr)-NaF composite template system. The kineti cs curves exhibit a typical S-shape characteristic. The apparent activation ene rgy for nucleation (En) and for crystallization (Ec), which were cal culated from the induction time and growing rate, are equal to 65.79±0.54 kJ/ mol and 91.49±0.62 kJ/mol respectively. The crystallization rate was accelera ted as the NaF amount increased. However, when the NaF content exceeded a certai n level, an adverse effect on zeolite product would appeared. The optimum n[ WT5”](NaF)/n(SiO2) was found to be within 0.10～0. 17. When n(NaF)/n(SiO2) became 0.25 corre sponding n(Na2O)/n(SiO2)=0.185, the ind uction period was prolonged. At the lower n(OH-)/n(SiO2)(≤0.7), the crystallization rate was very low. But at the higher n(OH-)/n(SiO2)(=1.2), the induct ion period was obviously shortened. So the appropriate alkalinity is in favor of the formation of transition complex and accelerates the nucleation.