SAPO-34分子筛晶化过程的研究

Study on the crystalizaiton mechanism of SAPO-34 zeolite

采用XRD、SEM、ICP-AES和MAS NMR等手段系统地研究了SAPO-34分子筛在常规水热合成过程和干胶液相转化过程中的组成和骨架结构的变化.结果表明,常规水热合成法在制备SAPO-34分子筛过程中,硅溶胶缩聚和解聚速率快,活性硅物种数量较少,产品易出现杂晶;采用干胶液相转化法,固体硅源解聚速率较慢,活性硅物种数量逐步增加,SAPO-34分子筛成核和成长的速率得到了控制,抑制了杂晶相的生成,SAPO-34分子筛结晶度逐渐增加.

The structure and composition of SAPO-34 zeolite synthesized by conventional hydrothermal process and dry gel liquid phase crystallization process were investigated by XRD, SEM, ICP-AES and MAS NMR characterization methods. The results showed that SAPO-34 zeolite with impurity was obtained by conventional hydrothermal process. Impurity was appeared due to fewer active silicon species with high rate of silica source depolymerization and polycondensation. Pure SAPO-34 zeolite was synthesized by dry gel liquid-phase crystallization process. The rate of nucleation and growth was controlled by slower rate of silica source depolymerization. Samples of relative crystallinity increased gradually.