Investigations on carbonization processes of plain tobacco stems and H3PO4-impregnated tobacco stems used for the preparation of activated carbons with H3PO4 activation

In order to elucidate the mechanism of carbonization process of tobacco stems-based activated carbons with H3PO4-activation, the pyrolysis characteristics of plain tobacco stems and H3PO4-impregnated tobacco stems were investigated through thermogravimetry (TG) at different heating rates (5, 15, 30 K/min) under nitrogen atmosphere. Based on TG curves, the kinetic parameters of the processes, including pre-exponential factors and activation energies, were calculated using the method of Coats–Redfern. The pyrolytic kinetic models of plain tobacco stems and H3PO4-impregnated tobacco stems were set up. The main pyrolysis stage could be described by the first-order and 2.5-order global models for plain tobacco stems and H3PO4-impregnated tobacco stems, respectively. The results indicated that the activation energy of carbonization process of H3PO4-impregnated tobacco stems was lower about 32.67–38.71 kJ mol−1 than that of plain tobacco stems; furthermore, the kinetic parameters exhibited kinetic compensation effects.