Investigation of the Kinetics of sII, Semiclathrates, and Their Synergistic Combinations for Enhanced CO ₂ Capture from Flue Gas

Increased greenhouse gas emissions are one of the major causes of global warming. Research is being done exhaustively to reduce and arrest carbon emission from human actions by different methodologies. Strategies that are economical, simple, and efficient are preferred for this purpose. The prime objective in this study is to capture carbon dioxide from simulated flue gas (mainly a mixture of carbon dioxide and nitrogen) using gas hydrate technology. The study focuses on the hydrate formation from simulated flue gas with 25% carbon dioxide/75 mol % nitrogen composition in the presence of 1,3-dioxolane (sII hydrate former), TBAC (semiclathrate former), and various kinetic additives. The study was conducted at a uniform moderate pressure of 4 MPa with varying concentrations of 4 to 19.5 wt % of 1,3-dioxolane, 10 to 33.4 wt % of TBAC, and 0.1 to 0.5 wt % of amino acids in a temperature range of 275.2 to 289.2 K. For the first time, combinations of the sII structure former 1,3-dioxolane and the semiclathrate structure former TBAC were studied to improve the CO2 gas uptake and separation factor. Specific combinations of 3 mol % 1,3-dioxolane + 10 wt % TBAC with 0.5 wt % tryptophan showed synergistic effects in comparison with the individual trials of the respective additives. Gas uptakes observed employing 3 mol % 1,3-dioxolane + 0.5 wt % tryptophan and 10 wt % TBAB + 0.5 wt % tryptophan were 18.55 ± 0.605 and 1.59 ± 0.065 mmol gas/mol, respectively. The combination trial with 3 mol % 1,3-dioxolane + 10 wt % TBAC + 0.5 wt % tryptophan showed an improved gas uptake of 33.4 ± 0.90 mmol gas/mol, substantially higher than both the individual trials. The synergistic combination of thermodynamic promoters, with suitable kinetic additives and the optimization of concentrations, could be a step toward enhancing gas uptake/separation limitations in gas hydrate technology.