Hydroliquefaction of lignin: Can it generate recycle solvents by itself?

Hydroliquefaction of lignin is an important method for obtaining sustainable aromatic chemicals. In this study, lignin was successfully converted to liquid products containing aromatic compounds via coal hydroliquefaction. Under optimum conditions, i.e., a tetralin (THN)/lignin ratio of 4:1, a reaction temperature of 400 degrees C, an initial H2 pressure of 3.0 MPa, and a reaction time of 4 h, the effects of catalysts on the hydroliquefaction of lignin were investigated. The results indicate that, for the hydroliquefaction of lignin, MoS2 is more advantageous than MoO3, Mo2C, and the absence of catalysts. Additionally, lignin derived from wood liquefies more easily than that derived from grass. Under the optimal conditions, the conversion of eucalyptus -derived organsolv lignin (EOL) and the oil yield were found to be 95.3 wt% and 83.5 wt%, respectively. These results were superior than those observed for coal hydroliquefaction, suggesting that lignin is easier to liquefy than coal. Further, the EOL, EOLHEX, and EOL-THF were characterized by 1H nuclear magnetic resonance, synchronous fluorescence spectrum, Fourier transform infrared spectroscopy, gel permeation chromatography, and elemental analysis techniques. The results show that there are not only multi -ring aromatic hydrocarbons (macromolecules) that cannot be detected by gas chromatography -mass spectrometry (GC-MS) spectra, but also multi -ring aromatic hydrocarbons (micromolecules) that can be detected by GC-MS spectra in lignin hydroliquefaction oil. The oils obtained at 400 degrees C and 450 degrees C contain multi -ring aromatic hydrocarbons of 28.5 wt% and 69.9 wt%, respectively, in yield. In conclusion, similar to coal hydroliquefaction, lignin can be liquefied by producing its own recycle solvents.