(377d) Simultaneous Separation of CO2 and H2s from Natural Gas By Modified Poly(ether-block-amide) Membranes

Natural gas plays a significant role in the global energy mix. More than 40% of current global natural gas reserves are highly sour, containing substantial amounts of H₂S and CO₂. H₂S is toxic and its concentration in Middle East gas reservoirs can potentially reach up to 30 mol%; therefore, the produced natural gas must be treated and sweetened. Polymeric membrane-based separation technology offers a compact and passive pretreatment step to reduce the burden of traditional amine adsorption separation techniques. Our recent efforts toward the treatment of Aramco aggressive sour gases have provided number of technical routes to improve sour gas separation performance through synthesis and modification of novel structures including rigid glassy and rubbery polymers. In this talk we describe a new strategy to modify polyether-block-amide (PEBAX) rubbery membranes for enhanced sour gas separation performance by controlling crosslinking moieties and crosslinked networks in the membrane matrix. By blending either CO₂-philic oligomers (e.g. PEG) or incorporating nanoporous inorganic fillers (e.g. POSS) into membrane, followed by photo-polymerization, such modified rubbery membranes provided outstanding combined (H₂S+CO₂) separation performance for purification of sour gas streams (20% H₂S) under challenging feed pressures up to 800 psi, compared to commercial control. We demonstrate that the modification of commercial polymers by combining the concepts of blending and crosslinking provides a unique design strategy for achieving ultra-selective and highly permeable rubbery membrane materials for practical natural gas sweetening.