Effect of Ionothermal Synthesis on the Acidity and Catalytic Performance of a SAPO‐5 Molecular Sieve

SAPO‐5 molecular sieves (E‐SAPO‐5) were synthesized ionothermally in 1‐ethyl‐2,3‐dimethylimidazolium bromides ([EMMIM]Br) ionic liquid (IL). The samples were characterized by X‐ray diffraction (XRD), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), N2 isothermal adsorption‐desorptionand, temperature‐programmed desorption of ammonia (NH3‐TPD) and fourier transform infrared (FT‐IR) spectroscopy. Moreover, the catalytic performances of the samples in the methanol conversion reaction were investigated. Relative to the hydrothermal method, ionothermal synthesis favored the formation of large silica islands mainly by the SM3 substitution mechanism and decreased the B acid sites and the strong acid and total acid amounts of E‐SAPO‐5, which significantly influenced the distribution of the products in the methanol conversion reaction. Methanol underwent the methanol‐to‐dimethyl‐ether (MTD) reaction and methanol‐to‐olefin (MTO) reaction over the E‐SAPO‐5 and hydrothermally synthesized SAPO‐5, respectively. E‐SAPO‐5 exhibited high MTD activity at the high temperature of 450 °C with methanol conversion of 100% and dimethyl ether (DME) selectivity of 86.6%. A SAPO‐5 molecular sieve (E‐SAPO‐5) was ionothermally synthesized. Relative to the hydrothermal method, ionothermal synthesis facilitated the formation of large silica islands mainly by SM3 mechanism and dramatically decreased the number of B acid sites and the strong acid and weak acid amounts of E‐SAPO‐5. E‐SAPO‐5 exhibited high methanol‐to‐dimethyl‐ether (MTD) activity with methanol conversion of 100% and dimethyl ether selectivity of 86.6%.