(609d) Natural Gas Sweetening By Membranes

Natural gas is one of the most important energy resources in the world. Methane is the main component, whereas significant amounts of impurities also co-exist in natural gas. Especially, the acidic components, i.e. hydrogen sulfide (H₂S) and carbon dioxide (CO₂), with coexistence of water (H₂O) can corrode processing and transporting equipment. In the Middle East, H₂S concentration in gas reservoirs can be as high as 30 mol.% with significant CO₂; therefore, sweetening natural gas prior to use has been a long-term industrial need for oil & gas companies, e.g. Aramco. Nevertheless, mature solvent-based natural gas processing cleanup processes suffers from significant drawbacks. Membranes are attractive alternatives benefiting from their lightweight, compact design, lower environmental impact, and ease of operation. However, although various membrane materials, e.g. rubbery/glassy polymer, inorganic and mixed matrix etc., have been investigated for natural gas processing, most of current studies focus on CO₂/CH₄ separation. The topic of developing membranes for H₂S/CH₄ or (CO₂ + H₂S)/CH₄ separation are less covered regardless of the higher importance of removing the more toxic H₂S from the mixture than CO₂ removal. Indeed, a membrane for combined CO₂ and H₂S separation from CH₄ are of high priority for the membrane community and the natural gas processing industry. Herein, we present our recent progress on (CO₂ + H₂S) simultaneous removal from highly “soared” natural gas, i.e. mixture with high concentration of CO₂ and H₂S, under realistic conditions by membranes. Our work suggests a new orientation of membrane material design toward natural gas processing.