CO(2) Capture from Flue Gas Based on Tetra-n-butylammonium Fluoride Hydrates at Near Ambient Temperature

[Image: see text] Semiclathrate hydrates of tetra-n-butylammonium fluoride (TBAF) are potential CO(2) capture media because they can capture CO(2) at near ambient temperature under moderate pressure such as below 1 MPa. In addition to other semiclathrate hydrates, CO(2) capture properties of TBAF hydrates may vary with formation conditions such as aqueous composition and pressure because of their complex hydrate structures. In this study, we investigated CO(2) capture properties of TBAF hydrates for simulated flue gas, that is, CO(2) + N(2) gas, by the gas separation test with three different parameters for each pressure and aqueous composition of TBAF in mass fraction (w(TBAF)). The CO(2) capture amount in TBAF hydrates with w(TBAF) = 0.10 was smaller than that obtained with w(TBAF) = 0.20 and 0.30. The results found that gas pressure greatly changed the CO(2) capture amount in TBAF hydrates, and the aqueous composition highly affected CO(2) selectivity. The crystal morphology and single-crystal structure analyses suggested that polymorphism of TBAF hydrates with congruent aqueous solution may lower both the CO(2) capture amount and selectivity. Our present results proposed that an aqueous solution with w(TBAF) = 0.20 is advantageous for the CO(2) capture from flue gas compared to near congruent solutions of TBAF hydrates (w(TBAF) = 0.30) and dilute solution (w(TBAF) = 0.10).