Novel Application of a Polyurethane Membrane for Efficient Separation of Hydrogen Sulfide from Binary and Ternary Gas Mixtures

Abstract

Abstract Recently we introduced a new polyurethane (PU) membrane synthesized from polypropylene glycol (PPG), hexamethylene diisocyanate (HDI), and 1, 4‐butane diol (BDO), and then studied the performance of the membrane for CO 2 removal. This paper presents a novel application of the PPG‐HDI‐BDO membrane for separation of H 2 S in binary and ternary gas mixtures. The gas transport properties of the membrane in binary H 2 S/CH 4 and ternary CH 4 /CO 2 /H 2 S gas mixtures at different temperatures, pressures, and gas compositions are investigated. Permeation tests show that the membrane has a high H 2 S/CH 4 selectivity (27.2), an outstanding H 2 S permeability of 790 Barrer, and a remarkable CO 2 permeability of 473 Barrer. The H 2 S permeability of 790 Barrer is the highest reported to this date for all PU membranes. The H 2 S permeability and H 2 S/CH 4 selectivity of the membrane increases with temperature. As the operating pressure increases, the CO 2 /CH 4 and H 2 S/CH 4 selectivities of the membrane increases. H 2 S and CO 2 permeabilities and H 2 S/CH 4 and CO 2 /CH 4 selectivities increase, as the H 2 S content of the feed increases. Solubility is most likely the dominant mechanism of gas permeation in this membrane. As the CO 2 content of the feed stream increases, the H 2 S permeability and H 2 S/CH 4 selectivity of the membrane decreases. The membrane has maximum H 2 S/CH 4 selectivities of 27.4 in binary H 2 S/CH 4 (with 0.075 mol% H 2 S) and 27.2 in ternary CH 4 /CO 2 /H 2 S (with 0.66 mol% H 2 S).