Sustainable synthesis of activated porous carbon from lignin for enhanced CO2 capture: A comparative study of physicochemical activation routes

Abstract

A sustainable and readily available material-lignin protobind 2400 was upcycled to activated porous carbon (APC) compatible with post-combustion CO2 capture. The effectiveness of the novel two-step physicochemical activation using KOH + CO2 and ZnCl2 + CO2 was compared with that of the respective physical (only CO2) and chemical activation (only KOH or ZnCl2). The effect of carbonization conditions (N2 or CO2 purging) on the resulting APC properties and CO2 adsorption performance was studied. The maximum BET surface area of 1480 m2/g and the best CO2 adsorption capacity of 5.68, 3.66, and 2.67 mmol/g were observed at 0, 25, and 40 C/1 bar, respectively. From the precursor to the final product, the APC yield falls within the range of 14.5-40.8 wt.%. The APC derived from lignin exhibited better CO2/N2 selectivity. The isosteric heat of adsorption for all the APCs remained below 40 kJ/mol, which suggested a lower energy requirement during the regeneration. The excellent reusability with fluctuations of only 0.51% in the amount of CO2 adsorbed over ten consecutive adsorption/desorption cycles, highlights the APC’s outstanding recyclability.