Tailoring Nitrogen‐Doped Activated Carbons: Central Composite Design for Enhanced CO2 Adsorption

Abstract In a single step, nitrogen‐doped activated carbons have been synthesized using walnut shells and urea as precursors by chemical activation with K 2 CO 3 . The textural and elemental properties such as surface area, micropore volume, nitrogen content, and yield were optimized in a multivariable way using a central composite design of experiments 2 3 , varying the urea‐nutshell ratio, K 2 CO 3 ratio, and activation temperature. Activated carbon doped with the highest nitrogen presented a surface area of 895 m 2 g −1 , a micropore volume of 0.22 cm 3 g −1 , and a nitrogen content of 4.11 %. Furthermore, the yield of 13.85 % at urea impregnation ratio 1.56 gUrea gNutshell −1 , activating agent ratio 1.4 gK 2 CO 3 gCarbon −1 , and temperature of 591 °C, being the temperature and the urea impregnation ratio the significant variables in the responses evaluated. The best‐activated carbon doped with nitrogen presented a CO 2 adsorption capacity of 2.78 mol kg −1 , reversible adsorption‐desorption, and selectivity against nitrogen of 33.2 molCO 2 /molN 2 , superior to a commercial activated carbon with similar textural properties at the same experimental conditions and being in the order of magnitude as activated carbons synthesized under similar conditions.