Hydrothermal Carbonization vs. Pyrolysis: Effect on the Porosity of the Activated Carbon Materials

Porous carbon materials (specific area over 2400 m2 g−1) were obtained from birch wood chips, the waste of its thermochemical processing water-insoluble lignocellulosic pyrolysis tar, and their mixture, by thermochemical activation with NaOH at 800 °C. Raw materials were carbonized by two methods: pyrolysis (500 °C) and hydrothermal (250 °C) treatment. The elemental and chemical composition of precursors and the effect of these parameters on the obtained carbon materials’ structure and porosity were studied. Results of the study showed that the carbonization method has little effect on the activated carbons’ specific surface area values; however, it allows for the regulation of pore size distribution.