Influence of synthesis parameters on preparation of AlPO-18 membranes by single DIPEA for CO₂/CH₄ separation

CO2-selective AlPO-18 membranes were prepared hydrothermally on macroporous supports with a low-cost template N, N-diisopropylethylamine (DIPEA). The effects of synthesis parameters (such as gel dilution, synthesis temperature, synthesis time and aging time) on the structure, morphology and single gas permeation properties of CO2 and CH4 through AlPO-18 membranes were investigated in detail. The synthesis conditions had little effect on the membrane morphology but strongly affected the CO2/CH4 gas permeation properties of assynthesized AlPO-18 membranes. The best membrane was obtained at a synthesis temperature of 433 K for 15 h after aging the precursor gel (1Al(2)O(3): 1P205: 4DIPEA: 120H(2)O: 4IPA) for 24 h. The CO2 single gas permeance of this membrane was 1.1 x 10(-6) mol/(m(2) s Pa), with an ideal CO2/CH4 selectivity of 56 at 303 K and a 0.1 MPa pressure drop. The mixed gas CO2 permeance of same membrane with an equimolar CO2/CH4 mixture was 1.1 x 10(-6) mol/(m(2) s Pa) with a CO2/CH4 selectivity of 75 at 303 K and a 0.2 MPa pressure drop.