晶化过程中无机盐及pH值调节对介孔分子筛水热稳定性的影响

以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,在碱性条件下合成了介孔分子筛MCM-41.借助XRD,SEM等检测手段考察了晶化过程中加入无机盐对介孔材料稳定性的影响.实验结果表明:加入NaF的样品其XRD衍射峰较强,表现出较好的结构有序性;在最初凝胶晶化24h后引入(NH4)2SO4,同样可获得有序的介孔结构;晶化过程中降低体系pH值能使硅酸盐的聚合度增大,孔壁厚度增加.由于所得产物具有完整的介孔结构,很好的结晶度及较大的孔壁厚度,因而在一定程度上提高了介孔分子筛的水热稳定性.

The Effect of Inorganic Salt and pH Adjustment on Hydrothermal Stability of Mesoporous Molecular Sieves in Crystallization

The mesoporous molecular sieves MCM-41 is synthesized with CTAB as template and TEOS as silica source in the basic conditions.The effects of inorganic salts and pH adjustment during the peroid of crystallization on the stability of mesoporous materials are investigated by XRD and SEM.It is found that the sample with NaF has more intensive XRD patterns and expresses better structural order.The ordered structure products can also be obtained with the addition of (NH4)2SO4 after the initial gel has been crystallized for 24 hours.The degree on polymerization of the silicate spieces and the pore wall thickness increase with decreasing pH value.Due to the perfect mesoporous structure of the product,better crystallized state and increased wall thickness the hydrothermal stability of mesoporous molecular sieves has been improved at some extent.