Effect of carbonization temperature on the physical properties and CO₂ adsorption behavior of petroleum coke-derived porous carbon

Cost-effective porous carbons for CO₂ capture were developed from petroleum coke using KOH as an activating agent. In particular, the effect of the carbonization temperature on the physical properties and CO₂ adsorption behavior of the prepared porous carbons was investigated while keeping the other conditions constant during KOH activation. The highest specific surface area and total pore volume of 1470 m²/g and 0.60 cm³/g were obtained for the porous carbon carbonized at 500 °C, with higher carbonization temperatures resulting in reduced porosities. XRD and FTIR analyses revealed that the structural disorder and amount of surface functional groups, both of which are favorable for porosity development during activation, had opposite trends with increasing carbonization temperature. Therefore, an optimal carbonization temperature existed for the maximum porosity. The porous carbon carbonized at 500 °C exhibited the highest CO₂ adsorption capacity of 4.17 mmol/g at 25 °C and 1 bar owing to its highest narrow micropore volume (pore size of less than 0.8 nm). In addition to its high CO₂ adsorption capacity, the prepared porous carbon presented good selectivity for CO₂ over N₂, moderate heat of adsorption, fast adsorption kinetics, facile regeneration, and stable adsorption working capacity during consecutive adsorption and desorption cycles, indicating its promise in practical CO₂ capture applications.