Production of highly microporous carbons with large CO2 uptakes at atmospheric pressure by KOH activation of peanut shell char

Abstract

Highly microporous carbons with large CO2 uptakes at atmospheric pressure were prepared by KOH activation of peanut shell char at different temperatures (680–780 °C). The porous carbons (PCs) showed a microporosity of 99.0–99.5 %, with micropore volume and specific surface area varying from 0.73 to 0.79 ml/g and 1713 to 1893 m2/g, respectively. The adsorption of CO2 onto the PCs was a physisorption process. The CO2 uptakes of the PCs increased with decreasing the activation temperature. The 680 °C-activated sample showed a 1-bar CO2 uptake of 7.25 mmol/g (0 °C), which was among the highest values ever reported for biomass-based PCs. The high uptake was principally ascribable to its developed small micropores (<1 nm). Besides, this PC displayed a large 1-bar CO2 uptake at 25 °C (4.41 mmol/g), fast CO2 adsorption rate, moderate CO2-over-N2 selectivity, and excellent recyclability. These adsorption properties showed that the peanut-shell-based PC was a promising adsorbent for CO2 capture or storage.