硅源与磷源对合成SAPO-34分子筛结构和形貌的影响

采用水热合成法制备了小晶粒SAPO-34分子筛,主要考察了不同硅源(硅溶胶,二氧化硅纳米粉和正硅酸乙酯)和磷源(磷酸,多聚磷酸)对合成SAPO-34分子筛的影响.实验结果表明:在合成液配比为1.0 Al2O3∶2.0 P2O5∶0.6 SiO2∶4.0 TEAOH∶105.0 H2O以及晶化温度为180 ℃晶化时间为48 h的条件下,二氧化硅纳米粉是较为理想的硅源,所合成的SAPO-34分子筛具有较高的结晶度,晶体呈现典型的立方体结构,晶粒大小为300 nm左右;而将多聚磷酸取代磷酸作为磷源后可以有效缩短合成时间至36 h,同时晶型由立方体结构转变为片状结构,但晶粒增大至为500 nm左右.

Influence of Different Silicon Source and Phosphoric Source on the Structure and Morphology of Small Gain SAPO-34 Molecular Sieves

The small gain SAPO-34 molecular sieves were prepared by hydrothermal synthesis method.The effects of different silicon source (silica sol, SiO2 nano powder, ethyl silicate) and phosphoric source (Phosphoric acid, poly phosphoric acid)on SAPO-34 formation were investigated.The results indicate that performance of nano-sized SiO2 powder is better than TEOS (tetraethoxysilane) and silica sol, the product prepared by nano-sized SiO2 powder has the high degree of crystallinity, the standard cubic structure with crystals size of about 300 nm under the condition of the initial gel mole ratio of 1.0 Al2O3∶2.0 P2O5∶0.6 SiO2∶4.0 TEAOH∶105.0 H2O with the crystallization temperature of 180 ℃ and the crystallization time of 48 h;when the poly phosphoric acid instead of phosphoric acid as the phosphoric source, the cubic crystals structure changed to flaky morphology and the crystals size increased to about 500 nm.