Calorimetric study of the CO2 adsorption on carbon materials

Given the great interest in the CO2 removal and decreasing their impact on the environment, in this work, a calorimetric study of CO2 adsorption on different activated carbons was performed. For this purpose, we used two methodologies for the determination heat of CO2 adsorption: determination of CO2 isotherms at different temperatures and adsorption calorimetry. The heats determined by these two techniques were compared. In this regard, carbonaceous materials of granular and monolithic types were prepared, characterized, and functionalized for carbon dioxide adsorption. As precursor material, African palm stones that were activated with H3PO4 and CaCl2 at different concentrations was used. The obtained materials were functionalized in gas phase with NH3 and liquid phase with NH4OH, with the intention to incorporate the surface basic groups (amines or nitrogen groups) and subsequently were studied for CO2 adsorption at 273 K and atmospheric pressure. For characterization of these materials, the following techniques are used: N2 adsorption at 77 K and immersion calorimetry in different solvents. The experimental results show the obtaining of micropores and mesoporous (moderately) materials, with surface area between 430 and 1,425 m2 g−1 and pore volumes between 0.17 and 0.53 cm3 g−1. It was determined that there is a difference between the heats of CO2 adsorption obtained by the techniques employed. This deviation between the values corresponds to the methodological difference between the two experiments. In this work, we obtained a maximum adsorption capacity of CO2, which is greater than 334 mg CO2 g−1 at 273 K and 1 bar in carbon materials with moderate surface area and pores volume.