The influence of pore structures and Lewis acid sites on selective hydrogenolysis of guaiacol to benzene over Ru/TS-1

Here, we report a Ru/TS-1 catalyst for selective hydrogenolysis of guaiacol to benzene in the aqueous phase at conditions of 240 °C and 0.2 MPa H2, achieving a benzene yield of 86% with a hydrogenolysis rate of 103.1 mmol g−1 h−1. It was found that Silicalite-1 (MFI type) with suitable pore sizes supported Ru nanoparticles (NPs) favored for hydrogenolysis of guaiacol, whereas de-aluminated Ru/HBEA, Ru/HY and Ru/MWW (without acidic sites) accelerated the parallel reactions of hydrogenation of aromatics. In addition, Ru NPs located at the orifice of Silicalite-1 was proved to be more electron-deficient and active than Ru NPs on the outer surface, as evidenced by CO-IR characterization and activity tests on Ru/Silicalite-1 (with and without templates). Moreover, Brønsted acid sites (BAS) on Ru/MFI highly promoted the hydrogenation rates of aromatics, while Lewis acid sites (LAS) on Ru/TS-1 and Ru/MFI led to a linear increase of guaiacol hydrogenolysis rate to benzene, probably due to the enhanced absorbance capability of guaiacol and phenol on the LAS of MFI. Thus, pore structure properties of MFI coupled with abundant LAS (TS-1) as well as Ru NPs on the orifice of pores of TS-1 construct a promising catalyst for achieving efficient aromatic hydrocarbons from selective hydrogenolysis of lignin.