Enclathration of tert-butyl alcohol in sII hydrates and its implications in gas storage and CO2 sequestration

The inclusion of tert-butyl alcohol (tBA) as a co-guest of clathrate hydrates in the presence of CH4, CO2, and N-2 was investigated for its potential role in gas storage and CO2 sequestration. The C-13 NMR, Raman spectroscopy, and powder X-ray diffraction revealed that the guest gas (CH4, CO2, and N-2) + tBA + water systems form sII hydrates. The enclathration of tBA molecules in the sII large (5(12)6(4)) cages resulted in significant thermodynamic stabilization of the CH4 + tBA and N-2 + tBA hydrates. However, the hydrate phase equilibrium curves of the CO2 + tBA hydrates were shifted to inhibited regions despite the participation of tBA molecules as a co-guest in the sII hydrate lattices. tBA was found to function as a thermodynamic promoter for both CH4 and N-2 hydrates, whereas it functioned as a thermodynamic inhibitor for CO2 hydrate. The overall experimental results provide a better understanding of the thermodynamic behaviors, structural transitions, and guest distributions of the guest gas (CH4, CO2, and N-2) + tBA hydrates for the potential use of tBA in gas storage and CO2 sequestration. (C) 2015 Elsevier Ltd. All rights reserved.