Study On Quaternized Poly Ether Sulfone Fixed Carrier Membrane For CO₂Separation

Separating and capturing CO2, a greenhouse gas and an important carbon resource, is of great significance. Fixed carrier membranes (FCMs) are of great interest because of their potential to achieve high selectivity and permeability. Currently. FCMs materials are mostly water-soluble, which will swell under humidifying conditions, reducing the service life of the membranes. Besides, carriers of FCMs are mainly amine groups (primary, secondary and tertiary amine). Studies on Quaternary ammonium groups as carriers are rare. In this work, ImPES, an anti-swelling quaternized Polyethersulfone (PES) material was successfully synthesised with commercial water-insoluble PES as the polymer matrix and1-methylimidazole as the quaternary ammonium reagent. Without the addiction of active carrier, only by the material and the quaternary ammonium groups within itself, can we prepare CO2FCMs with good permeability, selectivity and stability.ImPES was synthesized through chloromethylated and quaternized reactions. Subsequently, ImPES/PP composite membranes were prepared by solvent evaporation method with polypropylene (PP) porous membrane as support. The effects of degree of Imidazolium (DIm), ImPES concentration and solvent evaporation temperature on the membrane separation performance were investigated. ImPES/PP with good separation performance can be obtained with relatively mild solvent evaporation temperature and appropriate ImPES concerntration. CO2separation performance is augmented with the increase of DIm, only when DIm was over50%, the carriers tended to form a connected transmission channel to obtain high CO2permeation and selectivity. ImPES/PP membrane of64%DIm and20wt.%ImPES concentration showed a CO2permeation of13.65GPU, CO2/N2and CO2/CH4seperation factor of69.30and48.75.The reversible reaction between CO2and carriers was enhanced with the increasing test temperature, thus CO2permeantion increased without sacrificing selectivity. Appropriate improving of feed gas pressure can slightly decreased the permeation of N2and CH4, while increased the permeation of CO2, thus increased the CO2selectivity. ImPES/PP FCMs exhibited good stability when operating at0.4MPa for10days without significant performance degradation. To further improve the performance of the ImPES/PP FCMs, Poly vinyl alcohol (PVA) was adopted to prepare more hydrophilic blend membranes. As water content increased within the membrane the carrier activity was enhanced. PVA-ImPES/PP membrane showed a CO2permeation of10.25GPU, CO2/N2and CO2/CH4seperation factor of102.5and78.85. PVA was also used to hydrophilicly modify PP membrane to prepare ImPES/PVA-PP membranes with thiner composite layer, which exhibited CO2permeation of29.63GPU, CO2/N2and CO2/CH4seperation factor of69.06and50.22.