Post-combustion CO2 Capture Using Clathrate Formation: Effects of Thermodynamic Promoters

Abstract

Clathrate-based CO2 capture from flue gas was investigated in the presence of tetrahydrofuran (THF) as a water-soluble sII hydrate former, tetra-butyl ammonium chloride (TBAC) as a semiclathrate former, and cyclopentane (CP) as a water-insoluble sII hydrate former. The clathrate stabilities of the CO2 (20%) + N2 (80%) + promoters (THF (1.0 and 5.6mol%), TBAC (1.0 and 3.3mol%), and CP (1.0 and 5.6mol%)) systems were measured using an isochoric method. The clathrate equilibrium pressures at a specified temperature were significantly reduced in the presence of these thermodynamic promoters. Gas uptake and CO2 composition analysis in both vapor and clathrate phases were conducted using gas chromatography. The 5.6 mol% THF solution showed the largest gas uptake during the clathrate formation, but it demonstrated the lowest CO2 concentration (35 %) in the clathrate phase after the completion of clathrate formation. TBAC solutions exhibited approximately 60% CO2 concentrations in the clathrate phases regardless of TBAC concentration. The inclusion of CO2 in the clathrate phase was also confirmed via Raman spectroscopy. The overall experimental results are useful for the clathrate-based CO2 capture process from flue gas.