Biogas separation by semiclathrate hydrates formed with tetra-n-butylammonium and tetra-n-butylphosphonium salts

Sanehiro Muromachi, Kosuke Ikeda, Kazuki Maesaka and Hiroyuki Miyamoto

Energy, 2024, vol. 290, issue C

Abstract: CH4/CO2 gas separation which frequently appears in biomass energy remains as a kind of challenge for gas hydrates, since these two molecules are similarly preferred by the hydrate phases. Semiclathrate hydrates can improve gas capture preference from the canonical gas hydrates by unique phase behavior. In this study, we perform parametric gas separation tests by the semiclathrate hydrates formed from major four ionic guests, i.e., TBAB, TBAC, TBPB and TBPC with pressure conditions of 1, 3 and 5 MPa and aqueous salt concentrations of 0.10, 0.20, 0.30 in mass fraction. The captured CO2 amounts basically increased with aqueous concentrations. The highest CO2 capture amount was obtained by the TBAB solution with 0.30 in salt mass fraction. TBAC showed the highest CO2 selectivity, while interestingly, the lower the pressure, the higher the CO2 composition in the TBAC hydrate phase, which means that the low-cost operation without high compression of biogas could be feasible and reasonable with this material. TBAB showed relatively simple behavior compared to N2 + CO2 and H2 + CO2 systems. The present results showed that it is possible to eliminate CH4 and enrich CO2 in the hydrate phase when the ionic guest and thermodynamic conditions are appropriately chosen.

Keywords: Semiclathrate hydrate; Gas separation properties; Mixed gas; Methane; CO2 capture; Biogas (search for similar items in EconPapers)
Date: 2024
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:290:y:2024:i:c:s0360544223035703

DOI: 10.1016/j.energy.2023.130176

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