Structure and surface insight into a temperature-sensitive CaO-based CO2 sorbent

Calcium looping process is a prospective strategy to remove CO2 from flue gas. However, the CO2 capture capacity of the CaO-based sorbents would be spoiled severe over the repeated cycles. In this work, a kind of NaCl-modified CaO-based sorbents were prepared by a simultaneous hydration and impregnation process and explored for cyclic CO2 capture by a simultaneous thermal analyzer. The promotion mechanism was discussed by electron microscope, X-ray diffraction, N-2 physisorption, X-ray photoelectron spectroscopy, and so on. Results showed that NaCl tailored the temperature sensitivity of CaO-based sorbents, and it was a good promoter to enhance the carbonation activity of CaO-based sorbents, especially under higher temperature modes. At higher temperatures, NaCl would cover the surface of CaO, and promote the CO2 transportability in the modified sorbent, and then greatly improve the carbonation ability of the sorbents over the cycles. After 50 repeated cycles, the CO2 capture capacity of "10 NaCl/CaO" still retained at 0.288 g/g and 0.237 g/g when carbonated at 650 degrees C and 750 degrees C, which were 2.05 and 2.63 times that of "CaCO3 AR" respectively. Hence, the temperature-sensitive CaO-based sorbent promoted by NaCl shows a promising prospect for CO2 capture from flue gas.