CO2 capture in lignin-derived and nitrogen-doped hierarchical porous carbons

Abstract

Nitrogen-doped and hierarchical porous carbons were synthesized from lignin precursor by KOH and NH3 activation with BET surface area of 1631–2922 m2/g. X-ray photoelectron spectroscopy (XPS) revealed 5.6–7.1 at.% nitrogen with predominantly pyridinic, amino and pyrrolic/pyridonic type of functionality. Maximum CO2 adsorption capacity at 298 K and 273 K and pressure upto 760 torr (1 bar) was found to be 5.48 and 8.6 mmol/g respectively, which is higher than that of majority of nitrogen-doped carbons, reported in literature. Ideal Adsorbed Solution Theory (IAST)-based selectivity for CO2/N2 revealed that selectivity increases with the increase in nitrogen content. IAST calculations were also employed to calculate the binary adsorption isotherms to simulate mixed gas adsorption for CO2 and N2 as a function of total pressure and mole fraction of CO2 in the gas mixture. Continuous CO2 adsorption-desorption studies for 10 cycles revealed that all the nitrogen-doped carbons retained its working capacity at the end of the cycles. Finally, a breakthrough study for (10/90) CO2/N2 mixture in a dynamic column experiment confirmed a physical separation of the two components. The overall results suggest that nitrogen-doped carbons from lignin can be used as potential adsorbents for CO2 capture purposes.