High-performance SAPO-34 membranes for CO2 separations from simulated flue gas

High-quality SAPO-34 membranes were fabricated by the secondary growth method on outside asymmetric tubular alumina supports. The effects of temperature, pressure and feed flow rate on the separation performance of SAPO-34 membranes were investigated for CO2 separations from simulated flue gas. Single CO2, N-2 and CH4 permeances were predicted by Maxwell-Stefan diffusion model, and the predictions were fit well with experimental data. The unexpected high CO2/N-2 selectivities were 170 and 110 with high CO2 permeances of similar to 1.38 x 10(-6) mol/(m(2)sPa)(=4120 GPU) through our SAPO-34 membrane for equimolar and 15/85 (vol/vol) CO2/N-2 mixtures at 243 K and 0.1 MPa pressure drop, respectively. The membrane also displayed aCO(2) permeance of 4.67 x 10(-7) mol/(m(2)s Pa) ( =1390 GPU) and a CO2/N-2 selectivity of 10.3 in a dry 15/85 (vol/vol) CO2/N-2 mixture at 423 K. The moister in feed gas (0.68 mol% water vapor) decreased CO2 permeance and CO2/N-2 selectivity by only 19.3% and 14.9% in a wet 15/85 (vol/vol) CO2/N-2 mixture at 423 K, respectively, compared to those in the dry mixture. The separation performance could be recovered to the original values after drying. The current SAPO-34 membranes were far beyond the upper bound of zeolite membranes in CO2/N-2 plots and showed potential applications in CO2 separations from power-plant flue gas.