A one-pot process for the depolymerization of lignin-rich corncob residue (LRCR) is investigated in supercritical ethanol over an alumina supported NiMo (NiMo/Al) alloy catalyst. The LRCR, as a major by-product in corncob enzymatic hydrolysis process, was completely liquefied and effectively transformed into aromatic compounds without the formation of tar or char under optimal reaction condition. Reaction temperature, time, solvent and initial hydrogen pressure have significant effects on the depolymerization of LRCR. The highest overall aromatic yield of 255.4 mg/g LRCR with 57.9 wt % alkylphenols (e.g., 4-ethylphenol, 2,5-diethylphenol and 2,6-diisopropylphenol) was achieved with initial 27.6 bar (gauge) hydrogen in supercritical ethanol at 320 ºC for 7.5 h. The depolymerization of LRCR is also examined over Ni/γ-Al2O3, Mo/γ-Al2O3, and the physical mixture of these two catalysts. The NiMo/Al alloy catalyst exhibits much higher activity than that of other catalysts, and a synergistic effect between Ni and Mo active species is proposed. Furthermore, XRD results show that Mo1.24Ni0.76 alloy is expected to be an important active species for the depolymerization reaction.

A WO 3 /γ-Al 2 O 3 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 WO 3 and H 2 WO 4 , the WO 3 /γ-Al 2 O 3 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 WO 3 /γ-Al 2 O 3 catalyst. The WO 3 /γ-Al 2 O 3 keeps the high catalytic activity in three reuses.

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