Development of a cost-effective CO ₂ adsorbent from petroleum coke via KOH activation

The capture of CO ₂ via adsorption is considered an effective technology for decreasing global warming issues; hence, adsorbents for CO ₂ capture have been actively developed. Taking into account cost-effectiveness and environmental concerns, the development of CO ₂ adsorbents from waste materials is attracting considerable attention. In this study, petroleum coke (PC), which is the carbon residue remaining after heavy oil upgrading, was used to produce high-value-added porous carbon for CO ₂ capture. Porous carbon materials were prepared by KOH activation using different weight ratios of KOH/PC (1:1, 2:1, 3:1, and 4:1) and activation temperatures (600, 700, and 800 °C). The specific surface area and total pore volume of resulting porous carbon materials increased with KOH amount, reaching up to 2433 m ² /g and 1.11 cm ³ /g, respectively. The sample prepared under moderate conditions with a KOH/PC weight ratio of 2:1 and activation temperature of 700 °C exhibited the highest CO ₂ adsorption uptake of 3.68 mmol/g at 25 °C and 1 bar. Interestingly, CO ₂ adsorption uptake was linearly correlated with the volume of micropores less than 0.8 nm, indicating that narrow micropore volume is crucial for CO ₂ adsorption. The prepared porous carbon materials also exhibited good selectivity for CO ₂ over N ₂ , rapid adsorption, facile regeneration, and stable adsorption–desorption cyclic performance, demonstrating potential as a candidate for CO ₂ capture.