Adsorption of CO 2 , CH 4 , C 3 H 8 , and H 2 O in SSZ-13, SAPO-34, and T-Type Zeolites

Single-component adsorption isotherms for CO 2, CH 4, C 3 H 8, and H 2 O on SAPO-34, SSZ-13, and zeolite T were measured, and isosteric heats of adsorption were estimated. Long equilibration times were required for C 3 H 8 adsorption in SAPO-34 and SSZ-13 because C 3 H 8 diffuses slowly in these zeolites, but C 3 H 8 isotherms were obtained quickly on zeolite T. Thus, when CO 2 and C 3 H 8 coadsorption loadings were measured by temperature-programmed desorption on SSZ-13, CO 2 loadings were higher than C 3 H 8 loadings at short times, whereas at long times, C 3 H 8 loadings were higher as C 3 H 8 displaced adsorbed CO 2 . In contrast, adsorption of CO 2 /C 3 H 8 mixtures equilibrated quickly in zeolite T because of the fast C 3 H 8 diffusion. These adsorption measurements may explain previously reported zeolite membrane behavior where C 3 H 8 decreased CO 2 permeances for SAPO-34, SSZ-13, and zeolite T membranes under most conditions, and steady state was only slowly obtained for SAPO-34 and SSZ-13 membranes in the presence of C 3 H 8 .