Selective Conversion of Enzymatic Hydrolysis Lignin into Alkylphenols in Supercritical Ethanol over a WO3/γ-Al2O3 Catalyst

A WO3/γ-Al2O3 catalyst prepared by an incipient-wetness impregnation method is employed in the selective conversion of enzymatic hydrolysis lignin (EHL) into various alkylphenols in supercritical ethanol. In the reaction, EHL is completely dissolved and converted into aliphatic and aromatic compounds with a total yield of 363.4 mg/g lignin at 320 °C for 8 h. The yield of aromatic compounds is 315.8 mg/g lignin, accounting for 86.9% of the total yield of the products, and the overall selectivity of alkylphenols reaches 67.5%. Compared to WO3 and H2WO4, the WO3/γ-Al2O3 shows a higher activity for the conversion of EHL in supercritical ethanol. Besides, ethanol is found to be the most effective solvent for the depolymerization of EHL with the WO3/γ-Al2O3 catalyst. The WO3/γ-Al2O3 keeps the high catalytic activity in three reuses.