Experimental strategy for the preparation of adsorbent materials from torrefied palm kernel shell oriented to CO2 capture

Abstract

In this study, an experimental strategy to obtain biochar and activated carbon from torrefied palm kernel shell as an efficient material for CO₂ removal was evaluated. Biochar was obtained by slow pyrolysis of palm kernel shell at different temperatures (350 °C, 550 °C, and 700 °C) and previously torrefied palm kernel shell at different temperatures (220 °C, 250 °C, and 280 °C). Subsequently, activated carbons were prepared by physical activation with CO₂ from previously obtained biochar samples. The CO₂ adsorption capacity was measured using TGA. The experimental results showed that there is a correlation between the change in the O/C and H/C ratios and the functional groups -OH and C=O observed via FTIR in the obtained char, indicating that both dehydration and deoxygenation reactions occur during torrefaction; this favors the deoxygenation reactions and makes them faster through CO₂ liberation during the pyrolysis process. The microporous surface area shows a significant increase with higher pyrolysis temperatures, as a product of the continuous carbonization reactions, allowing more active sites for CO₂ removal. Pyrolysis temperature is a key factor in CO₂ adsorption capacity, leading to a CO₂ adsorption capacity of up to 75 mg/g_CO2 for biochar obtained at 700 °C from non-torrefied palm kernel shell (Char700). Activated carbon obtained from torrefied palm kernel shell at 280 °C (T280-CHAR700-AC) exhibited the highest CO₂ adsorption capacity (101.9 mg/g_CO2). Oxygen-containing functional groups have a direct impact on CO₂ adsorption performance due to electron interactions between CO₂ and these functional groups. These findings could provide a new experimental approach for obtaining optimal adsorbent materials exclusively derived from thermochemical conversion processes.

Keywords: Activated carbon; Biochar; CO2 adsorption; Porous structure; Pyrolysis; Torrefaction.