新型磷酸硅铝分子筛SAPO-56的合成与表征

以N,N,N',N'-四甲基-1,6-己二胺(TMHD)为模板剂,采用水热法在Al₂O₃-P₂O₅-SiO₂体系中合成了SAPO-56分子筛.固定模板剂和水,得到Al-Si-P三元体系相图.当原料物质的量比为0.52)/n(M)<0.7(M=SiO²⁺Al₂O³⁺P₂O₅),0.152O₃)/n(M)<0.4及0.12O₅)/n(M)<0.3时,出现SAPO-56合成的纯相区.固定合成凝胶中硅、铝、磷和水的量,模板剂的用量改变对合成影响较大.n(TMHD)/n(P₂O₅)≥2时,产物是纯SAPO-56.用XRD,SEM,IR,DTA-TG和吸附等方法研究了产物的物化性能.结果表明,SAPO-56分子筛具有较好的热稳定性(骨架坍塌温度为1150℃)和较大的水吸附量(41%).SAPO-56分子筛催化剂对甲醇转化制烯烃反应表现出了良好的催化活性和较高的C₂和C₃烯烃选择性.

Synthesis and Characterization of SAPO-56, a New Member of Silicoaluminophosphate

The molecular sieve SAPO-56 has been synthesized hydrothermally using N,N,N',N' tetramethyl 1,6-dihexane as template. In the Al₂O₃-SiO₂-P₂O₅ medium, phase diagram of SAPO-56 was obtained. Pure phase region of SAPO-56 appeared in the range of 0.52)/n(M)<0.7(M=SiO ²+Al₂O+³P₂O₅), 0.152O₃)/n(M)<0.4 and 0.12O₅)/n(M)<0.3. The effect of template amount on the synthesis of SAPO-56 was also investigated. Provided that other compositions (Si, Al, Pand H₂O) was fixed, it presented pure SAPO-56 crystal in the ratios of n(TMHD)/n(P₂O₅)≥2. The properties of SAPO-56 were characterized by XRD, SEM, TG-DTA, IRand adsorption technique which suggested that SAPO-56 had a good thermal stability and large water adsorption capacity. In the methanol to olefins reaction, SAPO-56 catalyst exhibited a high activity and selectivities to C₂, C₃ olefins.