CO 2 capture from flue gas using clathrate formation in the presence of thermodynamic promoters
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Energy, ISSN: 0360-5442, Vol: 118, Page: 950-956
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- Engineering; Environmental Science; Carbon dioxide; Clathrate; Thermodynamic promoter; Flue gas
Tetrahydrofuran (THF) as a water-soluble sII clathrate former, cyclopentane (CP) as a water-insoluble sII clathrate former, and tetra n -butyl ammonium chloride (TBAC) as a water-soluble semiclathrate former were used to investigate their thermodynamic promotion effects on clathrate-based CO 2 capture from simulated flue gas. The phase equilibria of CO 2 (20%) + N 2 (80%) + promoter clathrates at different promoter concentrations revealed that the presence of THF, CP, and TBAC could significantly reduce the clathrate formation pressure. THF solutions provided the highest gas uptake and steepest CO 2 concentration changes in the vapor phase, whereas TBAC solutions showed the highest CO 2 selectivity (∼61%) in the clathrate phase. CP solutions exhibited a slower formation rate, but their final gas uptake and CO 2 selectivity in the clathrate phase were comparable to the THF solutions. Raman spectroscopy confirmed the enclathration of both CO 2 and N 2 in the clathrate cages and a structural transition due to the inclusion of promoters in the clathrate phase. The overall experimental results indicate that TBAC is a viable thermodynamic promoter for clathrate-based CO 2 capture from simulated flue gas, considering the lower pressure requirement for clathrate formation, higher CO 2 enrichment in the clathrate phase, non-toxicity, and non-volatility.