(723j) Synthesis and Characterization of Cross-Linked Polyvinylalcohol / Polyethyleneglycol Blend Membranes for CO2/CH4 Separation

We have synthesized and characterized both zeolite 5A filled and unfilled, crosslinked polyvinylalcohol (PVA) / polyethyleneglycol (PEG) blend membranes for CO₂/CH₄ gas separation. The molecular weight (≤1000) of PEG showed slight influence on the selectivity of the resulting PVA/PEG membranes, while PEG (200) exhibited the highest permeability than any other PEG used. The cross-linked PVA/PEG membrane having 64 wt.% PEG (200) exhibited simultaneously high permeability and selectivity. The effects of zeolite 5A loading, feed pressure and temperature on the gas separation performance of both zeolite-filled and unfilled crosslinked PVA/PEG membranes were investigated. The experimental results showed that the zeolite-filled PVA/PEG membranes did not produce enhanced selectivity over the unfilled PVA/PEG membranes, but showed improved stability of performance as feed pressure increased. It was possibly attributed to the reduced compaction of zeolite-filled PVA/PEG membranes under high pressures. It was found that the selectivity of CO₂/CH₄ decreased as the zeolite 5A loading increased, while the CO₂ permeability initially decreased, followed by a drastic increase. The initial decrease of permeability could be due to either partial pore blockage of zeolite by polymer chains or the rigidification of polymer chains, while the following increase of permeability was due to the formation of additional porous network at high zeolite content. For both zeolite-filled and unfilled PVA/PEG membranes, increasing temperature caused the increase of their permeability but sacrificed their selectivity. The membranes were characterized by FTIR, TGA, DSC and SEM. FTIR results showed the zeolite 5A could be incorporated into PVA/EPG matrix. TGA showed that the incorporation of zeolite 5A improved the thermal stability of resulting PVA/PEG membranes, and SEM exhibited that the interfacial cracking between zeolite and blend polymer caused the decrease of selectivity as zeolite content increased.