Structural Analysis of Lignin and its Thermal Performance under Supercritical Water Conditions

Abstract

This study investigated the application of supercritical water as green and environmentally friendly treatment medium for hydrolysis and decomposition lignin in order to obtain the relation the products of phenolic compounds and the lignin structural. The processes were studied using three different biomass feed-stocks: poplar alkali lignin (AL), corncob enzymatic/mild acidolysis lignin (EMAL), and cornstalk or benzene–ethanol-extracted lignin (BEL), and lignin were identified by elemental analysis, FTIR, 31P-NMR. Experiments were performed in a batch stainless steel reactor at supercritical water 375°C at residence time of 10min. Main phenolic compounds from decomposition of lignin were identified by external standard method. Results indicated that the functional groups of AL, EMAL and BEL had a marked influence on the produces. More phenol OH groups and more benzene and phenolic contents could be gained under supercritical water conditions. The total produces reached to 74mg/g of dry EMAL and which was a high quality raw material as the source of phenol and 4-ethylphenol. The AL compositions of guaiacol, 4-methylguaiacol, 3-methoxycatechol, 2,6-dimethoxyphenol, 1,2,3-trimethoxybenzene had more than EMAL and BEL.