High temperature sequestration of CO2 using lithium zirconates

Equilibrium and kinetics of CO2 reaction with lithium zirconates synthesised by two different methods are reported. Considerably faster rates of high temperature reaction were obtained for the new material synthesised by a soft-chemistry route without the use of alkaline metal dopants, in comparison with the available literature data, with the highest rate 0.83 wt% min-1. Lithium zirconate was found to be stable in consecutive forward-backward reaction cycles. Reaction rate dependency on the partial CO2 pressure was examined. The apparent slow reaction rates at pC O2 0.4 bar are due to mass transfer limitations. Detailed analysis of the reverse reaction of decomposition of lithium carbonate-zirconia mixed matrix revealed complex three-step behaviour, which was associated with the transition from reaction to mass transfer control. The latter was successfully eliminated in the material prepared from a high surface area zirconia precursor. Low temperature interaction between lithium zirconate and CO2 revealed during experiments performed at 25-550 C is also discussed.