Catalyst Support and Solvent Effects during Lignin Depolymerization and Hydrodeoxygenation

We studied and compared the hydrodeoxygenation (HDO) and depolymerization of aldehyde-stabilized lignin and 4-propylguaiacol (PG), a model lignin monomer. We demonstrated by liquid phase adsorption that PG HDO catalyzed by Ru/C can be achieved in isooctane but not in 1,4-dioxane due to competitive solvent binding to the active sites. Unfortunately, alkanes cannot be used as solvents for real lignin due to limited solubility. However, we show that competitive solvent binding is suppressed when switching from activated carbon to oxophilic metal oxide supports such as TiO2, yielding 32%mol of an equimolar mixture of cyclohexanes and cyclohexanols from real lignin.