AtmosphericCO₂/CH₄permeability ofEVAcopolymer/SiO₂composite membrane for biogas purification

Abstract

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.