Synthesis of SAPO-34 Molecular Sieves Templated with Diethylamine and Their Properties Compared with Other Templates

Abstract

SAPO-34 molecular sieves were synthesized using diethylamine (DEA) as a template. Influencing factors, such as H3PO4 content, H2O content, Al source, and Si source, were investigated. Pure SAPO-34 could be obtained using the following synthesis gel conditions: 0.7 ≤ n(P2O5)/n(Al2O3) ≤ 1.2 and 25 ≤ n(H2O)/n(Al2O3) ≤ 100. The Al source has a great influence on the resulting sample composition. SAPO-34 could also be synthesized using triethylamine (TEA), morpholine (MOR), and a DEA-TEA mixture, respectively. The products were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy, thermogravimetry, and 29Si MAS NMR. The level of silicon incorporation into the SAPO-34 framework decreased in the following order of SAPO-34 (DEA) > SAPO-34 (MOR) > SAPO-34 (TEA). The Si(4Al) contents in the SAPO-34 frameworks followed the order of SAPO-34 (DEA) ≈ SAPO-34 (MOR) > SAPO-34 (TEA). 以二乙胺 (DEA) 为模板剂, 合成了 SAPO-34 分子筛, 详细考察了磷酸用量、水用量以及硅源和铝源等因素的影响. 结果表明, 在 0.7 ≤ n(P2O5)/n(Al2O3) ≤ 1.2 及 25 ≤ n(H2O)/n(Al2O3) ≤ 100 范围内, 可以得到纯相 SAPO-34 分子筛, 铝源对所得样品的组成影响较大. 同时, 采用三乙胺 (TEA)、吗啉 (MOR) 以及二乙胺-三乙胺 (DEA-TEA) 混合模板剂合成了 SAPO-34, 通过 X 射线衍射、X 射线荧光分析、扫描电镜、热重和 29Si 固体核磁共振等手段对所得样品进行了表征. 结果显示, 不同模板剂促使硅进入 SAPO-34 骨架的能力顺序为 SAPO-34 (DEA) > SAPO-34 (MOR) > SAPO-34 (TEA); SAPO-34 骨架中所能容纳的最大 Si(4Al) 含量顺序为 SAPO-34 (DEA) ≈ SAPO-34 (MOR) > SAPO-34 (TEA).