Low-Cost Temperature Transition Mixtures (TTM) Based on Ethylene Glycol/potassium Hydroxide as Reversible CO2 Sorbents

A low-cost Transition Temperature Mixture (TTM) has been synthesized by mixing ethylene glycol and potassium hydroxide as a new non-aqueous CO₂ sorbent. Boric acid has been added to ensure the reversibility of the system and a small amount of water to modulate the viscosity and optimize the performances. The resulting mixtures have been characterized in terms of viscosity, conductivity and density over temperature (therefore ionicity via Walden plots) and the effect of temperature, pressure and the kinetics of the absorption have been evaluated. Under optimized conditions, the four-component mixture EG/KOH/BA/H₂O 3:1:1:3 can absorb 24 g_CO2/kg_sorbent in 30 minutes at 35°C at 1 atm (59 after 4 h) and 60 g_CO2/kg_sorbent in 30 minutes at high pressure (10 and 20 atm, 80 g_CO2/kg_sorbent after 50 min), while the desorption is quantitative after 30 minutes at only 60°C under a gentle N₂ flow. The system is robust enough to ensure multiple absorption/desorption cycles.