Pre-combustion capture of CO2 from synthesis gas mixture CO2/H2 using hydrate formation

CO2 capture from CO2/H2 gas mixture is an attractive approach for reducing greenhouse gas emissions. This mixture is associated with power generation processes in power plants and typically contains 40% CO2 and 60% H2. A novel method for capturing CO2 from the above gas mixture is to use gas hydrate formation. This process is based on selective partition of CO2 between hydrate phase and gas phase. Due to their larger diameters, CO2 molecules have higher tendency to go into hydrate clathrates than H2 molecules, which ultimately results in a gas rich in carbon dioxide.
This study demonstrates the concept and presents the results of our experimental investigation for CO2/H2 separation by hydrate formation process. Since hydrate formation from water and gas requires high pressures, tetrabutylammonium bromide (TBAB) is added to the system to reduce the equilibrium pressure. TBAB forms semi-clathrates that can encage small gas molecules. The results shows that in one stage of gas hydrate formation and dissociation, CO2 can be enriched from 40% to 88%. In addition, the concentration of CO2 in equilibrium gas phase is reduced from 40% to 18%. While separation efficiency is comparable with the process without any additive, the presence of TBAB improves the operating conditions significantly. In addition, CO2 could be enriched to 98% by two stages of hydrate formation.