Influence of pyrolysis temperature on physicochemical properties of biochar obtained from the fast pyrolysis of pitch pine (Pinus rigida)

The aim of this study was to investigate the influence of pyrolysis temperature on the physicochemical properties and structure of biochar. Biochar was produced by fast pyrolysis of pitch pine (Pinus rigida) using a fluidized bed reactor at different pyrolysis temperatures (300, 400 and 500 °C). The produced biochars were characterized by elemental analysis, Brunauer–Emmett–Teller (BET) surface area, particle size distributions, field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, solid-state 13C nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). The yield of biochar decreased sharply from 60.7% to 14.4%, based on the oven-dried biomass weight, when the pyrolysis temperature rose from 300 °C to 500 °C. In addition, biochars were further carbonized with an increase in pyrolysis temperature and the char’s remaining carbons were rearranged in stable form. The experimental results suggested that the biochar obtained at 400 and 500 °C was composed of a highly ordered aromatic carbon structure.