Separation of light gas mixtures using SAPO‐34 membranes

Continuous SAPO‐34 membranes were prepared on porous alumina tubular supports, and shown to be useful for light gas separations at low and high temperatures. Single‐gas permeances of CO 2 , N 2 and CH 4 decreased with increasing kinetic diameter. For the best membrane at 300 K, the He and H 2 permeances were less than that of CO 2 , because He, H 2 , and CO 2 were small compared to the SAPO‐34 pore, and differences in the heat of adsorption determined the permeance order. The smaller component permeated the fastest in CO 2 /CH 4 , CO 2 /N 2 , N 2 /CH 4 , H 2 /CH 4 and H 2 /N 2 mixtures between 300 and 470 K. For H 2 /CO 2 mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400 K. The CO 2 /CH 4 selectivity at room temperature was 36 and decreased with temperature. The H 2 /CH 4 mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness.