Crosslinked hollow fiber membranes for natural gas purification and their manufacture from novel polymers

Recent research has developed a class of crosslinkable polymers that can be used as effective membrane separators for carbon dioxide removal from natural gas. In asymmetric hollow fiber form, these materials provide significant cost and savings over traditional amine absorption towers. This work focuses on the development of a method for forming asymmetric hollow fibers membranes from novel polymers in general, with specific application to this group of crosslinkable polymers. The majority of current hollow fiber membranes for gas separations are formed from a relatively small class of hydrophobic polymers. As new materials are discovered, it is important that they be processable into asymmetric hollow fibers, a form which allows for maximum productivity with a relatively small unit operation. A process was developed in this work to first systematically characterize novel materials, and then to apply the characterization to hollow fiber formation. The process requires a minimal amount of material, and was validated using a crosslinkable polyimide. A closely related polyimide was used to show the effectiveness of crosslinked asymmetric hollow fiber membranes for the removal of CO2 from natural gas. Fibers were spun using the process described, then crosslinked in the solid state for stabilization against CO2-induced plasticization. Initial studies of the crosslinking reaction revealed that only moderate temperatures (180°C - 200°C) are required for stabilization. The crosslinking reaction also happened relatively quickly (less than one hour), making the process reasonable for use in high-speed fiber production. Stability was shown upon exposure to both liquid solvents and high CO2 pressures, and the fibers were shown to be effective separators, maintaining high selectivity and productivity at high pressures over time.Chemical Engineerin