(551e) ALPO-18 Membrane for Gas Separations

CO₂ separation property of AEI-type zeolite, a kind of small pore zeolites having 8-membered ring (0.38 × 0.38 nm) was investigated. AlPO₄-18 membrane was prepared on a tubular a-alumina support by a secondary growth method using seed crystals. AlPO₄-18 seed crystals were supported on a surface of support by a dip coating method. Seeded support was soaked in synthesis gel (1Al₂O₃ : 1P₂O₅ : 1.8DIPEA : 100H₂O¹) and a hydrothermal treatment was carried out at 453 K for 4 h. Gas permeation tests were performed for the mixture of CO₂ and CH₄. As a result, the AlPO4-18 membrane exhibited high CO₂ permselectivity. CO₂ permeance of 5 × 10^-7 mol m^-2 s^-1 Pa^-1 with separation factor for CO₂/CH₄ of 39 at 313 K. Kinetic diameters of CO₂ and CH₄ are 0.33 and 0.38 nm, respectively, suggesting that CO₂/CH₄ separation by AlPO₄-18 membrane is due to a molecular sieving effect.　In addition, AlPO₄-18 membrane separated hydrogen from the mixture of hydrogen and propane. We will discuss on the possibilities of applying such a type of inorganic membrane to apply to separations of gas mixture containing small molecules like hydroge, CO₂ and light hydrocarbons.