Thermal characterization and pyrolysis of digestate for phenol production

Digestate, the residue following of anaerobic digestion , had attracted great attention recently as potential feedstock of pyrolysis . The results of component analysis verified that digestate was suitable for phenol production due to its considerable lignin content. The thermal degradation of lignin in digestate mainly occurred around 350–450 °C in thermogravimetric analysis . The amorphous cellulose in digestate decomposed to short-chain acids, water and syngas rather than furfural at low temperature around 280 °C. Pyrolysis of digestate for phenol production was conducted under different reaction temperature and pressure. High reaction temperature contributed to phenol formation by facilitating the cleavage reactions of β-O-4 and C–C linkages among three phenylpropane units in lignin. Pyrolysis pressure promoted secondary monomolecular dissociation reactions of methoxyphenol to yield phenol and alkyl-phenol. The maximum phenolics (70.4%) and phenol (42.6%) contents were achieved at 450 °C with 5 MPa pressure in this work.