Textural properties prediction of KOH-activated carbon prepared from coal based on pyrolysis kinetics

Pyrolysis kinetics were used in this study to analyze the pore formation mechanism of coal activated with KOH. Experimental derivative thermogravimetry (DTG) curves were fitted using Achar and Coats–Redfern methods to obtain kinetic parameters, such as activation energies. The effects of heating rate and KOH ratio on the activation energy show similar trends. Another attempt was trying to correlate the activation energies with the textural properties. The direct fitting was initially used and the obtained activation energies showed little correlation with textural properties. Two improved methods, namely, single peak fitting and multi peak fitting, were introduced. The former only considered the interaction between KOH and coal, regardless of coal pyrolysis. The activation energies obtained showed linear relation with the total pore volumes/BET (Brunauer–Emmett–Teller) surface areas (R²=0.94/0.99). The latter used Gaussian function to deconvolute the DTG curves, and then, each theoretical DTG peak could be correctly fitted. The positive linear correlation between the summed activation energies derived from surface reactions and metallic K intercalation and micropore volumes/surface areas was obtained (R²=0.993/0.996). Therefore, the proposed methods could be successfully applied to design and analyze the textural properties of specific coals with KOH activation.

Graphical abstract