Investigation on the Promoter-Induced Rapid Non-Aqueous Media Synthesis of SAPO-35 and Methanol-to-Olefin Reaction

Microporous SAPO-35 molecular sieves (Levyne type) were synthesized in non-aqueous media by using different inorganic promoters (HClO₄ ^-, HF, H₃PO₄, and NaNO₃) to enhance the rate of crystallization, and the as-synthesized materials were characterized by using different methods such as powder X-ray diffraction spectroscopy (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR), Brunauer-Emmett-Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS). From PXRD patterns, it was found that all the materials have a highly crystalline nature without any other impurities. SEM images reveal rhombohedral particles in all synthesis conditions. The framework structure of the synthesized materials was identified by FT-IR spectroscopy, and it reveals that all materials gave a similar framework structure. From BET and XPS, we have confirmed that the pore size and pore diameters along with the elemental compositions have a minor change. The ²⁷Al, ³¹P, and ²⁹Si MAS-NMR spectra of all the promoter-based SAPO-35 materials are close to those of the standard SAPO-35 material. All the above characterization studies reveal the formation of SAPO-35 in a short time with promoters. The catalytic application studies of these synthesized materials for a methanol-to-olefin conversion reaction were performed, and the efficiency of these materials was found to be similar to that of standard materials.