Removal of hydrogen sulfide from methane using PEO-segmented copolymer-based multilayer composite membrane

<p>The thermoplastic poly(urethane-urea) (PUU) was synthesized using polyethylene-glycol, 4,4ʹ-methylenediphenyl diisocyanate (MDI), and 1,2-ethandiamine (EDA) as a chain extender. A novel multilayer composite membrane consisting of the synthesized PUU, as a selective layer, a silicon rubber, as an interlayer, and the polyacrylonitrile (PAN) microporous support was prepared for the removal of acid gas. Moreover, the physical properties of the synthesized PEG-based polyurethane were investigated. Based on Differential Scanning Calorimeter (DSC) and ANDFourier Transform Infra-red Spectroscopy (FTIR) analyses, a higher microphase separation of hard and soft segments was observed for PUU. The permeabilities of pure CO₂, pure CH₄, and a ternary mixture of CH₄, CO₂, and H₂S through the multilayer composite membrane were measured at different temperatures and pressures. The maximum values of selectivity, <i>i.e</i>., 52 and 15 for H₂S/CH₄ and CO₂/CH₄, respectively, were found at 25°C and 5 bar. The permeances of H₂S and CO₂ in the ternary mixture decreased on increasing the feed pressure because of membrane compression. The higher the temperature, the higher was the permeability of the gases due to the more molecular movement of the polymer chains. Therefore, the gas selectivity in the synthesized composite membrane decreased by increasing the temperature. The experiments showed that replacing the pure-gas measurements with the gas mixture measurements can substantially produce more relevant results.