Synthesis and Permeation Properties of SAPO-34 Tubular Membranes

Abstract

A SAPO-34 membrane was prepared on an alumina tubular support. This membrane appears to exhibit molecular sieving properties with permeances that decrease as the kinetic diameter increases. The room-temperature permeances of H 2 and n -C 4 H 10 were 2.4 × 10 -8 and 1.9 × 10 -10 mol/(m 2 s Pa), respectively, and the permeances were in the order H 2 > CO 2 > N 2 > CH 4 > n -C 4 H 10 . As the temperature increased, the single gas permeances of H 2 and N 2 exhibited minima, whereas the permeance of CO 2 decreased and that of CH 4 increased. As the pressure increased with a constant pressure drop across the membrane, the permeances of H 2, CO 2, N 2, and CH 4 decreased. The H 2 /CH 4, CO 2 /CH 4, H 2 /N 2, and CO 2 /N 2 ideal selectivities at 300 K and 270 kPa feed pressure with a 138 kPa pressure drop were 25, 19, 7.4, and 5.7, respectively, and these selectivities decreased with increasing temperature and increased with increasing pressure. The ideal selectivity of N 2 /CH 4 was 3.4 at the same conditions and decreased with increasing temperature and increasing pressure. The H 2 /CO 2 ideal selectivity was 1.3 at the same conditions and increased with increasing temperature and pressure. At 270 kPa feed pressure and 138 kPa pressure drop, the CO 2 /CH 4 mixture selectivity was 30 at 300 K and 3.4 at 470 K.