Liquefaction Mechanism of Lignin in the Presence of Phenol at Elevated Temperature without Catalysts. Studies on ß-O-4 Lignin Model Compound. I. Structural Characterization of the Reaction Products

Guaiacylglycerol-β-guaiacyl ether (GG) was used as a starting material to study the liquefaction mechanism of lignin in the presence of phenol under elevated temperature without catalysts. The liquefaction products of GG obtained were analyzed by means of GPC and GC-MS. It was found that liquefaction of GG first produced relatively low molecular weight intermediates, followed by gradual conversion of these reaction intermediates to the polymeric products. After isolation by liquid chromatographic method, 28 main reaction intermediates were obtained and identified with the help of MS and NMR. It was found that they are mainly composed of guaiacol and various phenolated products of coniferyl alcohol, such as diphenylpropenes, phenylcoumaranes. phenylcoumarones and phenylflavanes. The detailed NMR data of these compounds and their assignments were demonstrated in this article.