In this study, PES/Pebax composite membranes were prepared by coating the porous PES support layers by Pebax-1657. Film casting and pouring methods were used for coating Pebax layer. The effects of coating technique and conditions including coating solution concentration and curing temperature on CO2 and CH4 gas permeabilities of prepared composite membranes were investigated. SEM images were used to investigate the structure of the prepared membranes. Pure CH4 and CO2 gases were used to investigate the gas permeation properties of the prepared membranes at different trans-membrane pressures (1-11 bar) and feed temperatures (25-55°C). The obtained data showed that the prepared PES supports did not provide any CO2/CH4 selectivity. The results also showed the CO2/CH4 selectivity for the membrane prepared via pouring technique was higher than that of the film casting procedure due to the defect-free Pebax layer formation. CO2 and CH4 permeance increased as the feed temperature increased from 25 to 55°C. The results also showed that CO2 permeance increased from 6.8 to 10.1 GPU with an increase in feed pressure from 2 to 12 barg, while CH4 permeance remained almost constant and CO2/CH4 selectivity increased from 27 to 42.

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