CO2 Capture Performance of Gluconic Acid Modified Limestone-Dolomite Mixtures under Realistic Conditions

Calcium looping (CaL) technology is potentially one of the more attractive ways to capture CO2 from fossil fuel power plants. However, with increasing numbers of reaction cycles, the CO2 capture capacity rapidly decreases. To address this shortcoming, limestone-dolomite mixtures reacted with gluconic acid to form Ca-Mg gluconics were explored to prepare highly effective, MgO-stabilized, CaO sorbents that exhibited a high and stable CO2 capture capacity over multiple cycles. The sorbents were all tested over 10 carbonation-calcination cycles, under realistic CaL conditions (calcination in a high CO2 concentration). The results indicate the development of an effective homogeneous composition between CaO and MgO, due to the small CaO crystallite size, porous texture, and nanosheet (∼100 nm thick) morphology. This provides sufficient void space for the volume expansion during carbonation to mitigate the effects of repeated cycle sintering and retain structural stability. Here, MgO content as low as 10 mol % was able to ensure a superior CO2 capture performance with a fast carbonation rate, high CO2 carrying capacities, and remarkable stability. Furthermore, these sorbents retained a conversion (above 90%) over multiple cycles following a recarbonation step.