Selective Separation of Methane from Carbon Dioxide through sII Hydrates Formation in a Semibatch Process

One of the challenges for production of natural gas from very sour gas reservoirs with CO₂ content up to 80% is the high cost of purification process. The hydrate-based gas separation (HBGS) process is gaining interest globally as a greener solution for separation of CO₂ from gaseous streams including sour hydrocarbon mixtures. However, separation of large amounts of CO₂ through gas hydrate formation typically leads to considerable loss of hydrocarbons. In this work, selective capturing of CH₄ from high CO₂ gas mixtures is investigated. Two water-soluble thermodynamic promoters, tetrahydrofuran (THF) and acetone, are used for this purpose. The results indicate that inclusion of these promoters dramatically increased CH₄ uptake by sII hydrate formation. However, only THF exhibited a favorable selectivity of CH₄. Moreover, this effect is pressure dependent, and the optimum pressure is around 4.5 MPa.