High-Temperature Adsorption of Carbon Dioxide on Mixed Oxides Derived from Hydrotalcite-Like Compounds

Various X n Y 3−n Al-hydrotalcite-like compounds (HTlcs) were synthesized by the constant pH coprecipitation method with the (X 2+ + Y 2+)/Al3+ molar ratio fixed at 3.0. Well-mixed oxides X n Y 3−n AlO were derived from corresponding HTlcs precursors upon calcination. Physicochemical characterization with X-ray diffraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and the Brunauer−Emmett−Teller equation indicates that the derived oxides are of either periclase or spinel phase, with an interparticle pore diameter of 9.6–15.4 nm. These oxides generally show a high CO2 adsorption capability at 350 °C. For example, CaCoAlO captures 1.39 mmol/g of CO2 (i.e., 6.12 wt %) from a gas mixture (8% CO2 in N2) at 350 °C and 1 atm in a fixed-bed reactor within 20 min. All other mixed oxides adsorb 0.87–1.28 mmol/g (3.83–5.63 wt %) of CO2. Therefore, these mixed oxides are potential cost-effective CO2 sorbents for environmental remediation. In addition, the CO2 adsorption behavior is well-described with the deactivation model. The species of CO2 formed on the sorbents are various carbonates, as revealed by in situ IR spectra as well as TGA.