Composition Analysis of Organosolv Lignin and Its Catalytic Solvolysis in Supercritical Alcohol

The structural analysis and catalytic solvolysis performance of organosolv lignins from Chinese fir (softwood) and maple (hardwood) were investigated. Fourier transformation infrared spectroscopy (FTIR) analysis revealed that both Chinese fir lignin and maple lignin exhibited a guaiacyl–syringyl structure. Chinese fir lignin consisted of guaiacyl units principally, while maple lignin consisted of syringyl units mainly. The ratios of guaiacol-/syringol-type products obtained by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) were 2.53 for Chinese fir lignin and 0.29 for maple lignin, respectively. The catalytic solvolysis degradation was studied in supercritical ethanol/1-butanol at 300 °C with Ru/C to produce phenolic compounds. The degradation products of Chinese fir lignin were mainly guaiacol-type products, while the products of maple lignin consisted of both guaiacol- and syringol-type compounds. The yields of most products of maple lignin were much higher than those of Chinese fir lignin. The results show that the organosolv maple lignin is a potential feedstock for producing phenolic products through the solvolytic method

Hydrogen Transfer Hydrogenolysis of Organosolv Chinese Fir Lignin to Monophenols over NiZnAlO_<i>x</i> Catalyst

Lignin is the only naturally renewable aromatized polymer consisting of several phenyl propane structures linked by C–O and C–C bonds, so lignin can be depolymerized into value-added chemicals or liquid fuels. In this study, M5Zn5AlOx (M = Co, Ni and Cu) catalysts were obtained by the co-precipitation method and then were used in organosolv lignin depolymerization. Among these catalysts, the Ni5Zn5AlOx catalyst possessed the largest surface area and abundant surface oxygen vacancies as well as strong acidic sites on the surface, giving the highest yield of monophenols (about 14.49 wt %). The effect of Ni/Zn ratios on the lignin depolymerization was also investigated, and it was found that the surface area and the proportion of surface oxygen vacancies and strong acidic sites of the NiZnAlOx catalysts increased and then decreased with the Ni/Zn ratios increasing. Similarly, the yield of monomeric compounds increased and then decreased with the Ni/Zn ratios increasing. The highest yield of monophenols was 17.18 wt % obtained over the Ni3Zn7AlOx catalyst, a remarkable monomer yield from organosolv lignin. The two-dimensional 1H-13C heteronuclear single-quantum coherence nuclear magnetic resonance spectroscopy of bio-oil revealed that the linkage bonds in lignin could be effectively broken over the Ni3Zn7AlOx catalyst. This study provided an effective route to obtain high-value chemicals from organosolv lignin under nickel-based catalysts