Precombustion Capture of Carbon Dioxide and Hydrogen with a One-Stage Hydrate/Membrane Process in the Presence of Tetra-n-butylammoniurn Bromide (TBAB)

Trapping CO2 in hydrates is a promising approach to reduce the greenhouse gas emissions. This work presents the efficient separation process of CO2 from the simulated fuel gas (39.2 mol % CO2/H-2 binary mixture) based on the hydrate crystallization in the presence of tetra-n-butylammonium bromide (TBAB): The experiments were carried out in the TBAB concentration range of 0.14-1.00 mol %, the temperature range of 275.15-285.15K, the driving force range of 1.00-4.50 MPa, the gas/liquid phase ratio range of 0.86-6.47, and the hydrate growth time from 15 to 120 min. The results indicate that the increase of the TBAB concentration or the driving force can enhance the separation efficiency, except when the TBAB concentration is above 0.29 mol % or the driving force is above 2.50 MPa. The lower gas/liquid phase volume ratio and the hydrate growth time can also promote gas consumption. However, H-2 more competitively encages into the hydrate phase with time. In addition, the temperature change has little effect on the CO2 separation efficiency with the fixed driving force. It is worth noting that the one-stage hydrate formation/decomposition process for the fuel gas in the presence of 0.29 mol % TBAB at 278.15 K and 2.50 MPa driving force could obtain a 96.85 CO2-rich gas and a 81.57 mol % H-2-rich gas. The split fraction (SFr) and separation factor (SF) of CO2 are 67.16% and 136.08, respectively. On the basis of the data of the separation efficiency, a hybrid conceptual process for precombustion capture based on only one hydrate formation/decomposition stage coupled with membrane separation is presented.