Basic Properties of MgAl-Mixed Oxides in CO₂ Adsorption at High Temperature

The increase of consciousness towards global warming and the need to reduce greenhouse gas emissions lead to the necessity of finding alternative applications based on easy-to-use materials in order to control and reduce global CO₂ emissions. Layered Double Hydroxides (LDHs) and LDH-derived materials are potentially good adsorbents for CO₂, thanks to their low cost, easy synthesis, high sorption capacity, and surface basicity. They have been intensively studied in CO₂ capture at high temperature, presenting variable sorption capacities for MgAl LDHs with the same composition, but prepared under different synthesis conditions. The ambient temperature coprecipitation synthesis method is an attractive one-step procedure to synthesize LDHs under mild conditions, with low energy consumption and short synthesis time. The present study is based on the synthesis and characterization of hydrotalcites by a mild-conditions coprecipitation process and the production of derived mixed oxides to be used as CO₂ adsorbents. A critical comparison to similar materials is reported. Moreover, the effect of the surface basicity of the derived mixed oxides (measured by adsorption calorimetry) and the CO₂ sorption capacity are discussed, showing a linear correlation between the amount of weak and very strong basic sites and the CO₂ adsorption behavior.