(461e) Polymeric Co2-Selective Membranes Containing Mobile and Fixed Carriers

CO₂-selective membrane has many applications, including the purification of synthesis gas to obtain high purity hydrogen, the removal of CO₂ from natural gas for natural gas sweetening, and the separation of carbon dioxide from flue gas for the greenhouse gas sequestration. In this study, polymeric CO₂-selective membranes consisting of an amino acid salt as the mobile carrier and polyamine as the fixed carrier in crosslinked poly(vinyl alcohol) were synthesized.

Transport properties of the membranes synthesized including CO₂/H₂ selectivity, CO₂/N₂ selectivity, CO₂ permeability, and CO₂ flux were studied with a gas stream containing hydrogen, carbon dioxide, and nitrogen. The effects of temperature, feed pressure, water concentration, membrane thickness on transport properties were investigated. The membranes showed good CO₂ permeability and CO₂/H₂ selectivity up to 170^oC for the feed gas pressure of 2.1 atm and the sweep gas of atmospheric pressure. Yet both CO₂ permeability and CO₂/H₂ selectivity decreased as temperature increased from 110^oC to 170^oC, which was presumably due to the reduction of water retention in the membrane as the temperature increased. CO₂/H₂ selectivity and CO₂ flux were studied as a function of membrane thickness. Based on the transport data from the membranes of different thickness, the total mass transfer resistance of CO₂ through the membrane was determined as a function of membrane thickness. Thus, the ?true' permeability, which is independent of membrane thickness was determined. In addition, CO₂/CO selectivity was studied with a gas stream containing hydrogen, carbon monoxide, carbon dioxide, and nitrogen, which showed the membranes had high CO₂/CO selectivity over the temperature rang from 110^oC to 170^oC.