In natural gas purification, membranes are attractive alternatives to the amine absorption processes, due to their lower cost, lower energy requirement, reduced environmental impact, and reduced size. In this work, it is desired to remove CO2 from natural gas using highly permselective hollow fiber membranes. Hollow fiber modules offer high surface area/volume for increased productivity compared to spiral wound and plate-in-frame modules. Carbon dioxide is usually the largest impurity in natural gas feeds and high CO2 partial pressures in the feed can lead to plasticization and loss of some methane product. Moreover, the presence of highly sorbing higher hydrocarbons in the feed can further reduce membrane performance. For polymer membranes to be used in these applications, they must be robust, resistant to plasticization, easily formed into asymmetric membrane forms and also exhibit adequate separation properties.
Covalent crosslinking has been shown to increase plasticization resistance in dense films by suppressing the degree of swelling and segmental chain mobility in the polymer, thereby preserving the selectivity of the membrane. This research focuses on extending the dense film success to asymmetric hollow fibers. The crosslinked hollow fibers reported here show the high selectivity and fluxes required for industrial application and are tested with model natural gas feeds at high pressures. The performance of the crosslinked hollow fiber membrane in the presence of high CO2 partial pressures and toluene (a highly sorbing contaminant) is investigated.