High purity carbon dioxide captured with guanidinium sulfate clathrate from carbon dioxide/hydrogen mixtures

CO₂ capture based on clathrate technology is an environmentally friendly separation approach, but low capture efficiency limits further commercial applications. Therefore, an innovative gas separation technology based on the efficient capture of CO₂ by guanidinium sulfate (Gua₂SO₄) clathrate was proposed. First, the phase equilibrium data of Gua₂SO₄ solution with CO₂, mixture (50.0 mol.% CO₂-50.0 mol.% H₂) were reported with temperature range from 294.6 to 304.6 K and pressure range from 0.25 to 0.92 MPa. They effectively reduced the formation pressure of CO₂ clathrate rather than H₂ clathrate, which revealed that it could selectively enter into clathrate cages. With the support of this theory, 72.0 wt.% (72.0 wt.%) Gua₂SO₄ solution was applied to obtain CO₂ concentration of 99.2 mol.% in the clathrate phase under the conditions of a gas-liquid ratio of 9.7, temperature of 277.0 K, and pressure of 1.0 MPa, realizing high-selective CO₂ capture of the gas mixture with 50 mol.% CO₂-50 mol.% H₂. With the decrease of driving force, the separation efficiency was increased. Raman analysis results further showed that H₂ did not enter the clathrate cages in the presence of Gua₂SO₄ during the separation of the CO₂-H₂ mixture, which was consistent with the experimental results. Furthermore, the minimum theoretical work of separation was calculated to be only 56.2 kJ/kg CO₂. This approach of high-selective CO₂ capture with Gua₂SO₄ provides new ideas and methods for the application of clathrate technology in the field of gas separation and carbon capture, which lays the foundation for commercial development.