Atmospheric CO 2 / CH 4 permeability of EVA copolymer/ SiO 2 composite membrane for biogas purification

The CO 2 and CH 4 permeabilities of poly(ethylene‐co‐vinyl acetate) (EVA)/SiO 2 composite membrane were investigated at atmospheric pressure. The membranes were fabricated by compression molding and characterized by Fourier transformed infrared spectroscopy, differential scanning calorimetry, a universal testing machine, and a contact angle analyzer. The effect of vinyl acetate content (18–33 wt%) was evaluated for both single‐gas and mixed‐gas permeation systems. A non‐pressurized homemade‐permeation cell was used for the single‐gas permeation of CO 2 and CH 4 , while a tubular membrane was utilized for a continuous separation of CO 2 /CH 4 mixture. CO 2 flux was readily increased (from 0.7 to 2.0 ml/m 2 .s) with vinyl acetate content (18–33 wt%). The enhanced CO 2 permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO 2 /CH 4 ) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO 2 as a filler (0.5–2.0 wt%) especially increased the membrane polarity and hence the CO 2 flux up to 6.0 ml/m 2 .s. However, the CH 4 flux was not affected by VA and SiO 2 contents.