A facile coating to intact SAPO-34 membranes for wet CO2/CH4 mixture separation

Abstract The excellent performance of SAPO-34 membranes for CO2/CH4 separation is detracted by the water interaction, resulting in membrane instability and low durability. Herein, a new facile coating strategy using α, ω-dihydroxypolydimethylsiloxane (PDMS) has been developed for surface protection of SAPO-34 membranes by dip-coating. The fabrication of coating layer was optimized by finely tailoring the coating solution parameters, such as the viscosity and PDMS concentration. The developed membranes were evaluated under dry and wet CO2/CH4 mixture systems with effect of temperature and pressure. PDMS/SAPO-34 membrane could provide high separation performance in both systems. The separation selectivity of 68 and CO2 permeance of 1.41 × 10−7 mol m−2 s−1 Pa−1 was achieved for wet mixture of CO2/CH4 at 80 °C during 120 h continuous operation. Furthermore, the PDMS/SAPO-34 membrane showed a wonderful performance after half a year storage, with 5–8% changes of CO2 permeance and selectivity for the dry CO2/CH4 mixtures, while for un-modified SAPO-34 membrane, a decline of 71% in CO2 permeance and 85% in CO2/CH4 separation selectivity was observed. The results demonstrated that the PDMS-coated SAPO-34 membrane could be a promising candidate for natural gas purification.