Use of Vanadium(V) Oxide as a Catalyst for CO2 Hydration in Potassium Carbonate Systems

The kinetics of CO2 absorption into 30% w/w K2CO3 solutions containing 0.1-0.5 M K4V2O7 was investigated at temperatures of 40, 60, and 75 degrees C using a wetted wall column. Vanadium(V) speciation diagrams were developed under these conditions as a function of CO2 loading using V-51 NMR spectroscopy. From these studies it was determined that there are two oxyvanadate ions that promote the absorption of CO2, HVO42-, and HV2O73-. The Arrhenius expressions for the rate constants of these two species were found to be k(HVO4) = 2 x 10(11) exp(-4992/T) and k(HV2O7) = 5 x 10(18) exp(-10218/T), respectively. Comparison of the observed rate constants with other promoters revealed that both active vanadium species showed performances comparable with that of MEA and vastly superior performances over those of other inorganic promoters. Due to speciation changes as the vanadium concentration is increased, the relative performance of vanadium diminished with increasing total vanadium concentration. As such, vanadium may be more suitable as a secondary component and corrosion inhibitor in a promoted carbonate system.