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

Abstract

A low-cost Transition Temperature Mixture (TTM) has been synthesized by mixing ethylene glycol and potassium hydroxide as a new non-aqueous CO<sub>2</sub> 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 <i>via</i> 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/H<sub>2</sub>O 3:1:1:3 can absorb 24 g<sub>CO2</sub>/kg<sub>sorbent</sub> in 30 minutes at 35°C at 1 atm (59 after 4 h) and 60 g<sub>CO2</sub>/kg<sub>sorbent</sub> in 30 minutes at high pressure (10 and 20 atm, 80 g<sub>CO2</sub>/kg<sub>sorbent</sub> after 50 min), while the desorption is quantitative after 30 minutes at only 60°C under a gentle N<sub>2</sub> flow. The system is robust enough to ensure multiple absorption/desorption cycles.