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

Nitrogen-doped and hierarchical porous carbons were synthesized from lignin precursor by KOH and NH3 activation with BET surface area of 1631e2922 m(2)/g. X-ray photoelectron spectroscopy (XPS) revealed 5.6e7.1 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 nitrogendoped carbons, reported in literature. Ideal Adsorbed Solution Theory (IAST)-based selectivity for CO2/N-2 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 N-2 as a function of total pressure and mole fraction of CO2 in the gas mixture. Continuous CO2 adsorptiondesorption 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/N-2 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. (C) 2017 Elsevier Ltd. All rights reserved.