Ionothermal synthesis of mesoporous SAPO-5 molecular sieves by microwave heating and using eutectic solvent as structure-directing agent

Abstract

SAPO-5 molecular sieve with AFI topology has been ionothermally synthesized by microwave irradiation and using eutectic mixture based on pentaerythritol and choline chloride as reaction medium. The resultant SAPO-5 molecular sieve was characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance ( 29Si MAS-NMR), N 2 physisorption, scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and thermogravimetry–differential thermal analysis (TG–DTA). 29Si MAS-NMR showed that the incorporation of Si in the calcined sample was mainly by the SM3 mechanism. N 2 physisorption measurements confirmed that the resulting SAPO-5 molecular sieve contained mesopores with a pore radius of about 3–30 nm. CHN and TG–DTA analysis revealed that it was choline that directed the synthesis of SAPO-5. Moreover, the factors affecting the crystallization of SAPO-5 molecular sieve were investigated in detail. The results showed that P 2O 5/Al 2O 3 ratios, HF/Al 2O 3 ratios and reaction temperature had great impact on the crystallization of SAPO-5.