Performance and stability of cellulose triacetate membranes in humid high H₂S natural gas feed streams

The current study aims to provide a thorough understanding of the separation performance of the cellulose triacetate (CTA) membrane material in humid high H₂S natural gas feed streams. A systematic study of the gas separation performances of CTA polymers has been carried out in self-standing symmetric films and asymmetric hollow fiber membranes. The separation performance in H₂S-containing mixtures (CH₄/CO₂/H₂S, 80/5/15 mol%) were evaluated at 30 and 50 °C at 20, 35 and 50 bar, including higher hydrocarbons (butane and toluene) in the presence of various levels of humidity, up to 4500 ppm or 80 % RH, depending on conditions of temperature and pressure. For the first time, the effect of these contaminants and humidity together under sour gas conditions has demonstrated the promising stability of CTA membrane separation performance, both in terms of H₂S permeability and H₂S/CH₄ selectivity. The improvement in H₂S permeability is due to a combination of H₂S plasticization and competitive sorption making this phenomenon even more attractive and worth studying further.