The conversion of guaiacol into the nylon precursors, cyclohexanol and cyclohexanone, is catalyzed by palladium supported on high surface area ceria (Pd/HS CeO2) under mild conditions (100 °C, ≤1 bar H2) via sequential hydrodemethoxylation and hydrogenation. In contrast, the 2-methoxycyclohexanol side product is generated by direct guaiacol hydrogenation. Reaction selectivity is determined by competing C-O bond hydrogenolysis versus arene hydrogenation. Hydrogenolysis selectivity increases as H2 pressure decreases, and over 80% H2 is incorporated into the products at 1 bar H2. Higher reactivity of guaiacol than anisole implies that the hydroxyl group is essential in Pd/HS CeO2 catalysis. Participation of water in the conversion is evidenced by deuterium incorporation at non-exchangeable positions when the reaction is performed in D2O. The combination of near quantitative mass balance of H2, high recyclability, and use of water as a solvent offers a simple, green and efficient conversion of lignin-derived aromatics into commercial products.
Available at: http://works.bepress.com/aaron_sadow/72/
This is a manuscript of an article posted as Zhou, Hui, Hsin Wang, Aaron D. Sadow, and Igor I. Slowing. "Toward Hydrogen Economy: Selective Guaiacol Hydrogenolysis under Ambient Hydrogen Pressure." Applied Catalysis B: Environmental (2020): 118890. DOI: 10.1016/j.apcatb.2020.118890. Posted with permission.