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    Tubular EVA copolymer/SiO2/PEG composite membrane for CO2 removal from household biogas
    (2025-03-01)
    Watasit, Prachya
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    Ausavasukhi, Artit
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    ; ;
    The fuel efficiency of household biogas is generally regulated by its CO<inf>2</inf> content (25%–50%). To improve its heating value, atmospheric CO<inf>2</inf> removal of household biogas using a polymeric membrane was attempted to avoid a complicated separation process. A tubular membrane of poly(ethylene-co-vinyl acetate), composed of 28% and 18% vinyl acetate (E28 and E18) modified with SiO<inf>2</inf> and polyethylene glycol (PEG), was fabricated by blown film extrusion. Model biogas containing CO<inf>2</inf>/CH<inf>4</inf> (40/60 v/v) was separated in an in-house continuous gas separation module, in which CO<inf>2</inf> was mainly permeated out of the tubular membrane at atmospheric pressure. Blending the E28 matrix with E18 (10 wt%) improves the membrane processability and inhibits the CH<inf>4</inf> permeation, leading to enhanced CO<inf>2</inf>/CH<inf>4</inf> selectivity (from ~2.3 to 2.9). Well-dispersed SiO<inf>2</inf> particles (0.5 wt%) increase the membrane modulus and suppress CH<inf>4</inf> loss. However, adding more SiO<inf>2</inf> (0.75–1.0 wt%) leads to higher total gas permeation flux with lower CO<inf>2</inf>/CH<inf>4</inf> selectivity due to particle agglomeration. Incorporation of PEG (0.5–1.5 wt%) increased the membrane polarity and CO<inf>2</inf> permeability. The CO<inf>2</inf>/CH<inf>4</inf> selectivity was also improved (~5.3), only up to 1.0 wt% PEG content. Highlights: Composite EVA/SiO2/PEG membrane separates CO<inf>2</inf>/CH<inf>4</inf> at atmospheric pressure. The concentration gradient across the membrane drives CO<inf>2</inf>/CH<inf>4</inf> permeation. Adding SiO<inf>2</inf> hinders CH<inf>4</inf> permeability and enhances CO<inf>2</inf>/CH<inf>4</inf> selectivity. Increasing PEG content enhances membrane polarity and interaction with CO<inf>2</inf>.
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    Item type:Publication,
    Atmospheric CO2/CH4 permeability of EVA copolymer/SiO2 composite membrane for biogas purification
    (2021-09-10)
    Watasit, Prachya
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    ;
    Ausavasukhi, Artit
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    ;
    The CO<inf>2</inf> and CH<inf>4</inf> permeabilities of poly(ethylene-co-vinyl acetate) (EVA)/SiO<inf>2</inf> 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%) wasevaluated for both single-gas and mixed-gas permeation systems. A non-pressurized homemade-permeation cell was used for the single-gas permeation of CO<inf>2</inf> and CH<inf>4</inf>, while a tubular membrane was utilized for a continuous separation of CO<inf>2</inf>/CH<inf>4</inf> mixture. CO<inf>2</inf> flux was readily increased (from 0.7 to 2.0 ml/m<sup>2</sup>.s) with vinyl acetate content (18–33 wt%). The enhanced CO<inf>2</inf> permeability is attributed to the increase in polarity and also the decrease in crystallinity of the membrane. A satisfied gas separation selectivity (CO<inf>2</inf>/CH<inf>4</inf>) of 4.31 could be obtained from tubular membrane with 28 wt% VA content. The incorporation of SiO<inf>2</inf> as a filler (0.5–2.0 wt%) especially increased the membrane polarity and hence the CO<inf>2</inf> flux up to 6.0 ml/m<sup>2</sup>.s. However, the CH<inf>4</inf> flux was not affected by VA and SiO<inf>2</inf> contents.