Fundamental research on gas–solid reaction between CO2 and Li2CuO2 linking application for solid CO2 absorbent

We compared reactivity between CO2 and Li2CuO2 with that between CO2 and Li4SiO4 by using XRD, SEM observation, and thermogravimetry in order to study fundamentally a potential of Li2CuO2 oxide for application to solid CO2 absorbents. The CO2 absorption ability of Li2CuO2 was examined by measuring rate constants for the gas–solid reaction between perfectly single-phase Li2CuO2 and CO2 at various temperatures in 100 vol% CO2 atmosphere using the rate theory with thermogravimetry using rapid heating. The measured rate constants were compared with those reported previously for Li4SiO4 at various temperatures. Almost no difference was found between these rate constants of Li2CuO2 and Li4SiO4 at temperatures less than 660 °C, but at temperatures higher than 670 °C, the rate constants of Li2CuO2 were greater than those of Li4SiO4. These results demonstrate that Li2CuO2 can outstrip the ability of Li4SiO4 to absorb CO2. Moreover, different from Li4SiO4, the CO2 absorption ability of Li2CuO2 decays only slightly, even if the atmospheric CO2 concentration decreases. -- Graphical abstract: Surface changes of Li2CuO2 and Li4SiO4 particles by progression of the gas–solid reactions between CO2 and these oxides. Highlights: • The CO2 absorption ability of perfect single-phase Li2CuO2 is reported. • Results show that Li2CuO2 can outstrip the Li4SiO4 ability to absorb CO2. • The oxide particle CO2 absorption ability is size- and surface-state-dependent