Investigation of ammonia/steam activation for the scalable production of high-surface area nitrogen-containing activated carbons
2022
Liu, Xinxin | Zuo, Songlin | Cui, Nannan | Wang, Shanshan
Ammonia/steam activation was investigated using a gaseous mixture of reductive ammonia and oxidative steam as the activator in an effort to develop an industrially feasible method to produce nitrogen-containing activated carbons. The results show that the ammonia/steam mixture can activate charcoals in the temperature range of 850–950 °C and produce nitrogen-containing activated carbon with a surface area >2000 m²/g and nitrogen content of ∼5% at 950 °C. Moreover, it was found that employing an equation of the natural exponential function, y=ae−bx+c (a b and c are the constants), can quantitatively describe the evolution of the increased surface area, micropore volume and iodine adsorption capacity of the activated carbon material per gram of gasified char as a function of the char burn-off in the activation process. Analysis of the X-ray diffraction patterns of the activated chars further revealed that the activation proceeds via the chemical gasification of the carbon atoms in the amorphous regions and, subsequently, the graphite-like crystallite regions. The former and latter stages are responsible to the formation of a majority of the micropores and mesopores, respectively. In short, ammonia/steam activation is an efficient and cost-effective method to manufacture nitrogen-containing activated carbon materials on a large scale.
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