1-Propanol as a co-guest of gas hydrates and its potential role in gas storage and CO2 sequestration

• We examine the enclathration of 1-propanol as a co-guest of gas hydrates.
• 1-Propanol forms cubic structure II hydrates with CH4 and CO2.
• 1-PrOH does not act as a notable hydrate promoter or an inhibitor for CH4 hydrate.
• 1-PrOH functions as a significant thermodynamic hydrate inhibitor for CO2 hydrate.

The inclusion of 1-propanol (1-PrOH) as a co-guest of gas hydrates in the presence of CH4 and CO2 and its potential role in gas storage and CO2 sequestration were investigated focusing primarily on macroscopic hydrate phase equilibrium behavior and microscopic structural and cage filling characteristics. The powder X-ray diffraction (PXRD) patterns confirmed that both double CH4 + 1-PrOH and double CO2 + 1-PrOH hydrates are cubic structure II (sII) hydrates. 1-PrOH did not act as a remarkable thermodynamic hydrate promoter or inhibitor for CH4 hydrate systems, though it did act as a significant thermodynamic hydrate inhibitor for CO2 hydrate systems despite its participation as a co-guest in the hydrate lattices. The 13C NMR results revealed that 1-PrOH was found in the large 51264 cages of the sII hydrate along with CH4 at lower 1-PrOH concentrations, and the chemical formulas for the double CH4 + 1-PrOH hydrates were found to be 2.13 CH4 · 0.53 1-PrOH · 17 H2O for the 1-PrOH 1.0 mol% solution and 1.85 CH4 · 0.75 1-PrOH · 17 H2O for the 1-PrOH 5.6 mol% solution. The overall experimental results provide a better understanding of guest–host interaction, guest distributions, and structural transition in guest gas + 1-PrOH hydrates for the potential application of 1-PrOH in gas storage and CO2 sequestration.