CO2 absorption by borate-promoted carbonate solution: Promotion mechanism and vapor liquid equilibrium

Carbonate-based solvents have advantages over amines for capturing CO2 from fossil fuel-fired power stations. However, due to slow reaction kinetics, boric acid has been proposed as rate promoter in carbonate-based solvents for reducing CO2 emission. In this work, borate promotion mechanism has been validated and vapor liquid equilibrium for 35 wt% carbonate solutions with 1 wt%, 3 wt% boric acid was investigated at 323 K, 333 K and 343 K. Based on complexation reaction with mannitol, results show that the tetrahydroxy borate ion, B(OH)4−, is considered as a reactive specie toward carbon dioxide absorption. Effect of boric acid and temperature on equilibrium CO2 partial pressures was discussed in the investigated CO2 loading range.