CO₂ Removal from a CO₂–CH₄ Gas Mixture by Clathrate Hydrate Formation Using THF and SDS as Water-Soluble Hydrate Promoters

This study investigates the use of hydrate formation to separate the CO 2 from a CO 2 –CH 4 gas mixture in the presence of water-soluble additives—tetrahydrofuran (THF) and/or sodium dodecyl sulfate (SDS)—at low concentrations. The influence of additive concentration and process operating conditions on the gas enclathration kinetics, the quantity of gas removed, and the selectivity of the separation are studied under quiescent hydrate-forming conditions in a batch reactor. Gas consumption and enclathration occur at high rates only when the two additives are used in combination. Similarly to what has been observed with pure CO 2, the proposed mechanism is that a mixed hydrate of structure sII containing THF forms first, which triggers the formation of CO 2 –CH 4 binary gas hydrate of structure sI. However, the gas separation was found not to be selective enough to the CO 2 for envisaging any practical application.