Effect of anaerobic pretreatment on vinegar residue for enhancement of syngas and phenols derived from pyrolysis

Abstract

AbstractAnaerobic digestion (AD) was applied as the pretreatment method to enhance the pyrolysis effect of vinegar residue (VR) in this study. Pyrolysis experiments were carried out in a fixed bed reactor. The functional groups of VR and AD‐treated VR (AVR) were quantitatively determined by Fourier‐transform infrared spectrometer (FTIR) using curve‐fitting method, prior to the in situ pyrolysis analysis using a thermogravimeter–gas chromatography–mass spectrometry (TG‐GC‐MS). The results show that AD was enhancing syngas and phenols to promote the pyrolysis effect of VR. AD process decomposed the hemicelluloses in VR, as indicated by the peak area decrease from 6.21% to 1.88% at 985 cm−1 assigned to glycosidic linkage in hemicellulose. The initial pyrolysis temperature (Ti) increased from 272°C to 300°C after AD, whereas the maximum weight loss rate temperature (Tm) decreased from 359°C to 349°C due to the ether linkage area percentage assigned in 1,035 cm−1 from cellulose increasing from 10.34% to 22.37% in AVR. The terminal pyrolysis temperature of AVR is lower than that of VR due to increment of lignin content and aromatic structure in AVR. The gas yield increases from 35.93% to 43.14% from AVR pyrolysis, and tar yield decreases by 24%. The formation of CO during pyrolysis was accelerated, whereas the hydrogen gas production increased significantly during pyrolysis after AD. The lignin‐derived phenols in tar increase from 20.67% to 42.16%, which is consistent with the analysis of TG‐GC‐MS.