Experiments and kinetic modeling of absorption rates of CO2 into unpromoted K2CO3 solutions at low to high solvent loading

Absorption by aqueous potassium carbonate is gaining renewed interest as a post-combustion carbon capture technology due to its benign chemistry and low regeneration duty. In this work, we present new experimental data on the absorption rate of CO 2 into aqueous K 2 CO 3 . We performed absorption experiments on 25 wt% K 2 CO 3 at a temperature of 313–358 K and solvent loadings up to 70%, using a thermostatted, stirred batch reactor. A stagnant film model accounting for all reactive species was used to derive the second order rate constant ( k 2 ) for the reaction between CO 2 and OH − . The role of the reaction was found to diminish with increasing solvent loading due to a decrease in the hydroxide concentration, whereas the k 2 was instead found to increase with the solvent loading. To explain this behavior we developed an ion-contribution model that relates k 2 to the ionic composition of the solvent. The model describes the experiments over the whole range of data with good accuracy. The results of this work are relevant for industrial applications of aqueous K 2 CO 3 where the absorption process is operated at high solvent loading to minimize regeneration duties. • The absorption rate of CO 2 into 25 wt% aqueous K 2 CO 3 was measured at various temperatures and solvent loadings. • The rate constant of the reaction of CO 2 with the hydroxide ion increases with increasing solvent loading. • The reaction rate constant was related to the solvent composition.