Solution combustion synthesis of zirconia-stabilized calcium oxide sorbents for CO2 capture

Calcium looping process has not yet been commercialized due to challenges associated with the activity loss of CaO sorbents resulting from sintering of the particles in cyclic operations. In the present study, zirconia-stabilized calcium oxide sorbents have been developed through the solution combustion synthesis (SCS) method. The effects of preparation conditions (percentage of Zr stabilizer and fuel-to-metal oxide ratio) on the CO2 capture performance were investigated in a thermogravimetric analyzer. Sorbents with 20% calcium zirconate stabilizer and high fuel-to-metal oxide ratio exhibited an optimal combination of CO2 uptake capacity and stability. Increasing the fuel ratio improved the CO2 uptake capacity due to higher surface area and smaller particle size of the synthesized sorbents. However, increasing the ratio beyond six did not have any significant impact on the performance of the sorbent. Based on the results, the optimum fuel-to-metal oxide ratio for synthesis was six times the stoichiometric ratio. Two sorbents showing the best results (S20-4x and S20-6x) were tested in 50-cycle experiments under mild and harsh calcination conditions for long-term stability assessment. Sorbents displayed high uptake capacity (7.7 and 8.8 mol/kg, respectively, under mild conditions; and 5.0 and 6.5 mol/kg respectively, under harsh conditions) after 50 cycles, which is a significant improvement over the uptake of the benchmark limestone (4.1 and 1.7 mol/kg under mild and harsh conditions, respectively). Based on the results, Zr-stabilized sorbents prepared from solution combustion synthesis method are promising materials for calcium looping CO2 capture.