SAPO-5分子筛的可控合成及晶化过程探索

在非醋酸体系下分别通过动态和静态水热晶化方法合成了SAPO-5分子筛, 并考察了转速、 晶化时间及凝胶体系水硅比对SAPO-5分子筛晶相及形貌的影响, 采用X射线衍射(XRD)和扫描电子显微镜(SEM)技术研究了静态、 动态水热条件下SAPO-5分子筛的晶化过程. 结果表明, 静态水热条件下晶化6 h得到的SAPO-5分子筛为球状、 六边形柱状聚集晶体; 而在20 r/min转速下晶化2和6 h得到的SAPO-5分子筛分别为分散的凹面柱状晶体(凹面直径约6~8 μm)及均一分散的球状晶体(直径为16 μm); 在60 r/min转速下晶化3 h即可得到高度分散的六边形柱状晶体(六边形直径约5~8 μm); 提高转速至100和140 r/min时仅需晶化1 h即可得到六边形柱状晶体. 通过考察体系水硅比(H₂O/Si摩尔比)的影响, 确定最佳的水硅比为70, 此条件下所得晶相为纯相且分子筛的分散度最好. 综上可知, 相较于静态晶化, 动态晶化不仅从形貌上改善了晶体的分散度, 通过缩短晶化时间、 降低晶化转速也提高了SAPO-5分子筛的晶化效率. 本文采用较小的水硅比(H₂O/Si摩尔比为70)、 较低的模板剂用量在非醋酸体系下合成了SAPO-5分子筛, 为SAPO-5分子筛的合成提供了一条更简单、 经济的路线.

Controllable Synthesis of SAPO-5 Molecular Sieves and Exploration of the Crystallization Process †

SAPO-5 molecular sieves were synthesized in non-acetic acid systems through rotating and static crystallization routes, respectively. The effects of rotation speed, crystallization time and water-silicon ratio of the gel system on the crystallization process of SAPO-5 samples were explored. The crystallization process of SAPO-5 samples under static and rotating hydrothermal conditions were studied by XRD and SEM. The results show that SAPO-5 samples obtained under the static hydrothermal conditions for 6 h is spherical and hexagonal columnar aggregated crystals. While the SAPO-5 samples obtained at 20 r/min for 2 or 6 h are dispersed concave columnar crystals(about 6—8 μm in diameter) and uniformly dispersed spherical crystals(16 μm in diameter), respectively. And SAPO-5 samples obtained at 60 r/min by extending the crystallization time to 3 h is hexagonal columnar crystal(about 5—8 μm in diameter). Also, hexagonal columnar SAPO-5 samples can be obtained by crystallizing at a rotation speed of 100 and 140 r/min for only 1 h. In addition, this work by adjusting the water-silicon ratio, the optimal water-silicon ratio was determined to be 70(the crystal phase is pure and the molecular sieve has the best dispersion from the morphology). In summary, compared to static crystallization, rotational crystallization not only improves the dispersion of the crystal from the morphology, but also improves the crystallization efficiency of SAPO-5 samples through shortening the crystallization time and reducing the crystallization speed. At the same time, SAPO-5 samples was synthesized in a non-acetic acid system with a smaller water-silicon molar ratio(70) and a lower amount of template agent, which provided a simpler and economical method for the synthesis of SAPO-5 molecular sieve.