Characterization of AlPO4-based molecular sieves and methanol conversion to light olefins

Of the AlPO₄-based molecular sieves, A1PO₄, SAPOs, and MeAPOs of different pore sizes were prepared at 100-200°C by a hydrothermal crystallization method. This study was purposed to maximize the yield of light olefins through methanol conversion. Crystal structure was confirmed by means of XRD and SEM, and acidity was examined by TPD and IR of adsorbed ammonia on the catalysts. It was found that SAPO-34 exhibited more than 90% selectivity for light olefins such as ethylene, propylene, and butylene due to shape selectivity through small pores, although it had a strong acidity. MeAPO-34 exhibited slightly lower selectivity for light olefins than SAPO-34 and different product distribution, depending on the electronegativity of the metal in its framework. SAPO17 and SAPO-44, which have the same pore size with SAPO-34 but different pore structure from SAPO-34, showed less selectivity for light olefins than SAPO-34.