Application of tetra-n-butyl ammonium bromide semi-clathrate hydrate for CO2 capture from unconventional natural gases

Abstract

In this study, tetra-n-butyl ammonium bromide (TBAB) semi-clathrate hydrate was employed for CO2 capture from unconventional natural gases exploited by supercritical CO2 injection. The TBAB hydrate formation kinetics and CO2 separation efficiency were studied under different TBAB concentrations and subcoolings using a stirred tank reactor. Optimum experimental conditions were obtained (2.8 MPa, ΔT = 6 K, 2.57 mol% TBAB), and the synergetic effect of sodium dodecyl sulfate (SDS) and TBAB on CO2 separation from CH4 + CO2 was investigated under these conditions. The results indicate that gas consumption and CO2 selectivity declined with the increase of subcooling, and the best CO2 selectivity was obtained at 2.57 mol% TBAB. The kinetics of TBAB hydrate nucleation and growth were promoted when adding SDS into the TBAB solution, but the CO2 separation efficiency was reduced. The CO2 selectivity obtained at 2.57 mol% TBAB was significantly improved as compared to the THF, THF/SDS, and TBPB systems. Therefore, TBAB is a prospective promoter for hydrate-based CO2 capture from CH4 + CO2. Continued efforts are required in the future to increase the gas consumption without sacrificing the CO2 separation efficiency.