No abstract

CO 2 adsorption at elevated pressure was studied in a Mg−Al (Mg/Al = 3) layered double hydroxide (LDH). The double-layered structure was prepared via a coprecipitation method. The sample's structure and microstructure evolutions were characterized using X-ray diffraction, scanning electron microscopy, N 2 adsorption, and thermogravimetric and calorimetric analyses. The CO 2 adsorption experiments were performed between 5 and 4350 kPa at different temperatures (30−350 °C). Elevated pressure experiments showed that this material was able to adsorb different quantities of CO 2 depending on the thermal evolution of its structure and microstructure. The highest CO 2 adsorption (5.7 mmol/g) was produced at 300 °C before the layered structure had completely collapsed. At these specific conditions the interlayer space was reduced from 7.78 to 4.39 Å. This interlayer change was attributed to the onset of LDH structural collapse. However, at this temperature the adsorption process must be favored over the adsorption−desorption equilibrium, allowing the maximum CO 2 capture.

Lithium cuprate (Li 2 CuO 2 ) was obtained by a solid state reaction and a subsequent ball milling process; then, the samples were characterized structurally and microstructurally. Additionally, both the Li 2 CuO 2 ball milled and the solid state samples, for comparison purposes, were tested in the CO 2 chemisorption process at moderate and low temperatures under different reaction conditions: (i) at moderate CO 2 pressure and (ii) in the presence of water vapor. In both cases, the textural and microstructural properties of the ball milled Li 2 CuO 2 samples showed excellent CO 2 chemisorption properties which are significantly enhanced due to CO 2 pressure effects or the presence of water vapor. All these results were attributed to the textural and morphological changes evidenced in the samples. The observed surface area increments show preponderant effects during CO 2 chemisorption at low and moderate temperatures.