Highly porous N-doped carbons impregnated with sodium for efficient CO2 capture

Abstract

Highly porous sodium-impregnated and N-doped carbon sorbents (SNSs) were prepared by KOH activation of polyacrylonitrile (PAN), followed by NaOH impregnation of the activated N-doped carbons. These new types of materials were investigated as sorbents for CO2 capture. Particularly, SNS2-20 prepared with the KOH/PAN ratio of 2 at 700 degrees C and 20 wt% NaOH based on the weight of the activated carbon exhibited the adsorption capacity of 6.84 and 4.48 mmol g(-1) at 0 and 25 degrees C under ambient pressure. Among the carbon sorbents reported to date, it showed the highest CO2 uptake of 3.03 and 1.90 mmol g(-1) at 0 and 25 degrees C under a typical pressure condition of post-combustion flue gas (0.15 bar CO2). The enhanced CO2 uptake is due to high porosity caused by KOH activation, enriched pyridonic/pyrrolic nitrogen contents, and strong basic sites generated by NaOH impregnation. Moreover, CO2/N-2 selectivities of 59.5, 68.9 and 79.4 at 0, 25 and 50 degrees C were achieved for the gas mixture (CO2 : N-2 = 15 : 85) according to the ideal adsorbed solution theory (IAST). The consecutive adsorption-desorption cycle experiments using SNS2-20 showed almost unaltered CO2 uptake capacities. Combined with its simple preparation, the high CO2 adsorption capacity and selectivity of the synthesized SNS2-20 could provide potential for practical applications of CO2 capture and storage.