Thermogravimetric pyrolysis of residual biomasses obtained post-extraction of carnauba wax: Determination of kinetic parameters using Friedman's isoconversional method

Thermogravimetric pyrolysis of carnauba straw and carnauba stalk was studied for the first time. The experiments were carried out at four different heating rates (5–20 °C min−1) and the kinetic parameters were calculated using three isoconversional methods such as Friedman (differential), KAS (integral), and OFW (integral). The activation energies and R2 were calculated for the conversions between 0.10 and 0.90. The average activation energies were found to be 225.28 (±26.83 kJ mol−1) for carnauba straw and 218.13 (±28.06 kJ mol−1) for carnauba stalk by the Friedman method; 223.17 (±17.72 kJ mol−1) for carnauba straw and 211.04 (±18.82 kJ mol−1) for carnauba stalk by KAS method; and 212.71 (±23.19 kJ mol−1) for carnauba straw and 217.94 (±17.85 kJ mol−1) for carnauba stalk by OFW method. The FTIR spectra showed bands characteristic of hemicellulose, cellulose, and lignin at 3331 cm−1 (O–H) and 3345 cm−1 (O–H); 2919 cm−1 (C–H) and 2928 cm−1 (C–H); and 1733 cm−1 (CO) and1723 cm−1 (CO). The carnauba straw presented molar ratios of 1.43 (H/C) and 0.78 (O/C), and the carnauba stalk of 1.39 (H/C) and 0.81 (O/C). The kinetic parameters, FTIR spectra, and molar ratios are in good agreement with other reported biomasses.