Studies On Solvothermal Degradation Of Lignin

Lignin is nature's second-largest renewable and alternative materials, which is composed of phenylpropane units cross-linked network structure polymer with low utilization rate. This article intends to use heat-solvent degrading lignin to small molecules products, such as organic acids, phenolic compounds, carboxyl or aldehyde phenolic chemicals with high additional value.Firstly, the degradation of lignin in methanol was studied, obtaining kinds of single ring aromatic compounds, which are guaiac-based structure primarily. After degradation, The weight-average molecular weight Mw from 12,600 down to 700, and the THF insoluble condensation product mainly composed of C-C bond structure, and almost no ether bond exist in TIS products by weak formation in IR and TGA analysis.Secondly, influences of temperature, reaction time and water content under various process conditions were investigated for lignin degradation. Results show that longer reaction time to cause the guaiac-based phenolic degradation, and significantly promote the 3,4-dimethoxy ethyl benzene and 3-methoxy-4-hydroxy propyl benzene. Raising temperature did accelerate reaction rate and the reaction temperature set at upper 300℃is appropriate, components of guaiacol, the 3-methoxy-4-hydroxy toluene,3,4-dimethoxy ethyl benzene and 3-methoxy-4-hydroxy acetyl benzene cargoes little or no generation in water. Compared to methanol system, methanol/H2O co-solvent system led to more heavy compounds and tar in TIS products.Finally, based on the alkali lignin research, the method was applied to Chinese Fir degradation. The weight average molecular weight degraded from several hundred thousand to Mw=200-800. Chinese fir is mainly composed of guaiacyl propane structure, hence, the TS products from degradation were guaiac-based chemical. The influence of the temperature on the degradation is significant and the appropriate temperature is 300-350℃.