Comparison of Granular and Pellet Olive Stone-Based Activated Carbon in Adsorption-Based Post-Combustion CO2 Capture

In the present study, we evaluate the CO2 uptake capacities of four activated carbons (ACs) obtained from olive stones. Two of the samples were generated using a chemical process utilizing phosphoric acid, thereafter undergoing carbonization in a nitrogen steam, yielding both granular and pellet forms, designated CH-ACG-410 and CH-ACP-410, respectively. The third sample, labeled CO-ACG-390, was produced by carbonization under a steam-nitrogen flow, while the fourth sample, designated PH-ACG-850, was prepared by a physical process involving water vapor at 850 °C. The carbon materials obtained in granular and pellet form were subjected to textural characterization using N2 and CO2 adsorption isotherms at 77 K and 273 K, respectively. Additionally, surface chemistry was analyzed using FTIR, Boehm titration, and TPD-MS. The materials were also assessed for CO2 adsorption in a binary mixture consisting of 10% CO2 and 90% N2 at two temperatures, 25 and 50 °C. The results demonstrated that all prepared adsorbents exhibited competitive CO2 capture performance, with the CH-ACP-410 sample (pellet form), showing the highest adsorption capacities, achieving approximately 4.6 wt. % at 25 °C and 2.2 wt. % at 50 °C. This superior behavior can be attributed to the conditioning methods applied to this material, which significantly influenced its textural properties and, consequently, its CO2 adsorption capability.