Ultra-permeable high-selective SAPO-34 membranes for efficient CO2 capture

Ultra-permeable SAPO-34 membranes with membrane thickness of 0.8–1.2 μm were reproducibly fabricated using diluted mother liquids with H2O/Al2O3 ratios of 300 and 450. The orientation and thickness of the membranes were greatly affected by mother liquid dilution. Thickness-even SAPO-34 membranes were reproducibly prepared in a large synthesis time window, indicating that membrane synthesis had good robustness and it is suitable to the scale-up fabrication. The membranes prepared at H2O/Al2O3 ratio of 450 displayed ultrahigh CO2 permeances of (1.0–1.3) × 10−5 mol (m2 s Pa)−1 (∼30000–37000 GPU) and CO2/CH4 selectivities of (56–126) at 298 K and 0.2 MPa pressure drop. The typical membrane also displayed CO2 permeance of 7.6 × 10−6 mol (m2 s Pa)−1 (∼23000 GPU) and CO2/N2 selectivity of 35 for an equimolar CO2/N2 mixture. The separation performance of these thin SAPO-34 membranes was far beyond that of most reported membranes. Such CO2 permeances of the membranes are 200–350 times higher than that of commercial polyimide membranes. The membranes shows great potentials for CO2 capture from natural and flue gases.