Impacts of the surfactant sulfonated lignin on hydrate based CO2 capture from a CO2/CH4 gas mixture

In the present work, we report an investigation of using an anionic surfactant sulfonated lignin (SL) to promote gas hydrate formation for CO 2 capture from a CO 2 /CH 4 gas mixture. The experiments were performed at 277.15 K in a stirred tank reactor. The initial overpressure (driving force) for hydrate formation was fixed at Δ P  = 2.5 MPa. The impacts of the SL presence on hydrate growth behavior and CO 2 separation efficiency were elucidated. The results indicated that hydrate nucleation was prolonged in the presence of SL but this stage was accelerated when adding 1.0 mol% tetrahydrofuran (THF) into the SL solution. Compared to THF/SL and sodium dodecyl sulfate (SDS) solutions, CO 2 recovery obtained in SL solutions was increased to 63.5 ± 2.9% and the separation factor was 4.0 ± 0.8. Gas consumption obtained in SL solutions was higher than that obtained in other systems like liquid water, SDS solution, THF solution, and tetra- n -butyl phosphonium bromide (TBPB) solution. Therefore, sulfonated lignin can be used as a promising surfactant to improve hydrate formation kinetics as well as the efficiency of CO 2 capture from CO 2 /CH 4 gas mixture, but there still exists a space to increase the CO 2 selectivity in the presence of SL.