Kinetic and Mechanistic Study of CO ₂ Absorption into Vanadium-Promoted Aqueous K ₂ CO ₃

Aqueous potassium carbonate (K2CO3)-based absorption processes are among the first-generation carbon capture technologies ready for large-scale deployment. The high stability of aqueous K2CO3 and its low regeneration energy demand present clear advantages. However, the inherently slow CO2 uptake by aqueous K2CO3 remains a key limitation. We present a comprehensive study on vanadium pentoxide (V2O5) as a rate promoter to enhance the absorption of CO2 in aqueous K2CO3. The absorption rate of CO2 was measured over a wide range of conditions, namely V2O5 concentrations up to 6 wt %, solvent loadings up to 60%, and temperatures between 313 and 358 K. The rate promoter was found to significantly enhance the absorption rate across all conditions, by up to a factor of 2–3 with respect to unpromoted K2CO3. Analysis of vanadium speciation indicated that this enhancement arises from the reaction between CO2 and hydrogen monovanadate (HVO42–), with a rate constant that increases exponentially with ionic strength. A kinetic model incorporating this relation accurately reproduced the observed absorption rates across the experimental range. The results of this work demonstrate V2O5 is an effective rate promoter under conditions typical of K2CO3-based processes, thus enabling reductions in compression duties and associated capital costs without major process changes.