NMR Characterization of Pyrolysis Oils from Kraft Lignin

摘要

The pyrolysis of softwood (SW) kraft lignin was examined at 400,500,600, and 700 ℃ The yields of pyrolysis oil, char, and gas were determined to be 35-44%, 57-38% and 8-18%, respectively. The pyrolysis oil has a comparable heating value with ethanol and coal. The elevated temperature of 700 ℃ was found as the point of primary decomposition of lignin and the secondary decomposition of pyrolysis oil. Gel permeation chromatography (GPC) and quantitative ~(13)C and ~(31)P NMR were used to characterize the pyrolysis oil. A ~(13)C NMR database was created to provide a more accurate chemical shift assignment database for analysis of pyrorysis oils. On the basis of the results of ~(13)C and ~(31)P NMR for the pyrolysis oil, aliphatic hydroxyl, carboxyl, and methoxyl groups are eliminated during pyrolysis. Cleavage of ether bonds in lignin was also shown to be a primary decomposition reaction occurring during thermal treatment The results of GPC analysis indicated that lower pyrolysis temperatures yielded a bio-oil that had a lower molecular weight and lower porydispersity value.