Carbon dioxide absorption into unpromoted and borate-catalyzed potassium carbonate solutions

Abstract

Potassium carbonate based solvents have the potential for capturing CO2 from emission sources such as power stations burning fossil fuels. However, due to poor reaction kinetics a rate promoter is considered necessary to improve the rate of reaction of CO2 with the solvent. Using a characterized wetted-wall column, we have studied the reaction kinetics of CO2 into unpromoted and borate-promoted 30wt% potassium carbonate solutions. Results presented here show that, at 80°C, addition of small amounts of boric acid (0.2M, 0.6M and 1.5M) accelerate the overall absorption process of CO2 in carbonate solvents by 3%, 10% and 29% respectively. The Arrhenius expression for the reactions CO2+OH− and CO2+B(OH)4− are kOH [M−1s−1]=2.53×1011exp(−4311/T [K]) and kborate [M−1s−1]=5.5×1011exp(−6927/T [K]); and the activation energies are 35.8kJmol−1 and 57.6kJmol−1 respectively. Experiments were conducted between 40°C and 80°C and at a bulk partial pressure of CO2 of 90kPa.