Solvent Effect in Catalytic Lignin Hydrogenolysis

The solvent effect in the catalytic depolymerization of the three-dimensional network of lignin is discussed based on recent reports in this field. Also, the results of an experimental study on the depolymerization of kraft lignin are presented. The cleavage of ether bonds within the lignin network was promoted using ruthenium and platinum on activated carbon (Ru/C and Pt/C), two common hydrogenolysis catalysts. Methanol was identified as a suitable solvent. Noteworthy, under the chosen reaction conditions, the catalysts showed significant resilience to the sulfur present in kraft lignin. The conversion of kraft lignin to lignin oil was strongly affected by the reaction conditions. Although the Ru/C catalyst provided the highest yield at supercritical conditions, a maximum yield was obtained for the Pt/C catalyst at near-critical conditions. The formation of guaiacol, 4-alkylguaiacols, isoeugenol, and 4-ethyl-2,6-dimethoxyphenol is attributed to the solubility of oligomeric lignin fragments in the solvent and the relative propensity of specific groups to adsorb on the catalyst surface.

Automated summary

This paper discusses the solvent effect in the catalytic depolymerization of lignin, as well as presents the results of an experimental study on the depolymerization of kraft lignin. The study finds that ruthenium and platinum catalysts, particularly Pt/C, show resilience to sulfur in kraft lignin, and methanol is a suitable solvent. The reaction conditions strongly affect the conversion of kraft lignin to lignin oil, with different catalysts showing different optimal conditions. The formation of specific products is attributed to the solubility of oligomeric lignin fragments in the solvent and the adsorption of specific groups on the catalyst surface.