Phase equilibrium and kinetics of gas hydrates formed from CO2/H2 in the presence of tetrahydrofuran and cyclohexane

Abstract

In the present study, tetrahydrofuran (THF) and cyclohexane (CH) were combined as a mixed promoter to improve the hydrate based gas separation (HBGS) process for the separation of CO2 from a CO2/H2 gas mixture (40 mol% CO2 and 60 mol% H2). The amount of THF and CH used was fixed at 1.0 mol% and 10 vol% respectively. The phase equilibrium data of gas hydrates formed in the presence of the mixed THF + CH promoter were measured between 275.15 K and 281.15 K, and were compared with that obtained in the presence of other thermodynamic promoters (THF, cyclopentane, etc.). The hydrate dissociation enthalpy was calculated from the phase equilibrium data measured in the presence of the mixed THF + CH promoter and was reported. In addition, kinetic experiments were conducted to assess the impact of the mixed promoter (1.0 mol% THF + 10 vol% CH) on CO2 selectivity from the CO2/H2 gas mixture. The results indicated that the addition of cyclohexane to 1.0 mol% THF solution shifted the hydrate formation conditions to higher temperatures and lower pressures as compared to those obtained in the presence of 1.0 mol% THF or 1.0 mol% TBANO3, and the hydrate based CO2 selectivity obtained in presence of the mixed THF + CH promoter was enhanced comparing with that obtained in the presence of THF.