Study on alcoholysis of pine sawdust in ethylene glycol and alcoholysis mechanism

The alcoholysis of pine sawdust with acidified ethylene glycol (EG) as solvent was investigated; the influence of reaction temperature and time on the conversion of pine sawdust was examined. The alcoholysis residual was characterized by thermogravimetry (TG), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and X-ray diffraction (XRD), whereas the composition and properties of hexane insoluble components (HIS) and hexane soluble ones (HS) were determined by FT-IR and gas chromatography-mass spectrometry (GC-MS). The results showed that the conversion of pine sawdust reaches a maximum of 95.3% at 160 ℃ after reaction for 90 min. By the alcoholysis, the amorphous components of cellulose and lignin were decomposed and the surface structure of alcoholysis residual is destructed. The hexane insoluble components are composed of compounds with oxygen-bearing functional groups such as hydroxyl, methoxyl and ether, whereas the hexane soluble components consist of mainly phthalic acid esters, methyl stearate, 2-methyl propyl caproate, 2-methyl propionic acid, polyethylene glycol and unreacted EG. The esterification of EG with carboxylic acid, derived from pine sawdust, can improve the stability of liquid product and promote the alcoholysis of pine sawdust, whereas the self-condensation of EG, forming polyethylene glycol, may increase the consumption of EG.