Endogenous hydrogen-driven lignin depolymerization into jet fuel precursors over supported nickel catalyst

The catalytic hydrogenolysis of aromatic C–O bonds in lignin to produce phenolic jet fuel precursors offers a promising route for lignin valorization. However, conventional methods often suffer from reliance on noble metal catalysts, harsh reaction conditions, and external hydrogen gas. Herein, we report a strategy using isopropanol as the in-situ hydrogen donor with non-precious Ni/CeO2 catalyst to hydrogenolyze lignin and lignin dimers under N2 atmosphere. The Ni/CeO2 catalyst proved highly effective in cleaving aromatic C–O bonds, mainly producing aromatic hydrocarbons and cyclohexanol. At 240 oC for 2.5 h, complete conversion of benzyloxybenzene (BOB) and 2-phenoxyphenylethanol (POPE) was achieved, and diphenyl ether (DPE) achieved 96.9 mol% conversion. A series of control experiments confirmed that Ni0 species serve as the primary active sites of Ni/CeO2, and the strong interfacial interaction between Ni and CeO2 also plays an indispensable role. For the depolymerization of organosolv lignin, syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) phenolic monomers are the main products, with carbon numbers ranging from C7 to C11, serving as effective phenolic precursors for jet fuel. A maximum monophenol yield of 36 wt% was achieved under the conditions of 240 oC, 7.5 h, and a catalyst/lignin mass ratio of 75/100. Characterization of the lignin oil and the spent catalyst confirmed that this system effectively depolymerizes lignin, with the catalyst exhibiting excellent structural stability and regenerability. In summary, this work provided an efficient approach for producing valuable phenolic precursors for jet fuel from lignin.