Ru nanoparticles supported on various metal-modified (La, Zr, Cr, Ce and Ga) α-Al2O3 for the selective hydrogenolysis of lignin and its derived ethers

Abstract

Controlling the C-O bond hydrogenolysis while suppressing the direct hydrogenation of aromatic rings in lignin-derived ethers is critical and challenging for the utilization of lignin. Herein, a series of metal-modified (La, Zr, Cr, Ce and Ga) α-Al2O3-supported Ru-based catalysts were synthesized for the conversion of diphenyl ether (DPE). The catalyst characterizations demonstrate that the metal modification cannot change the chemical valence of Ru but promotes the dispersion of Ru nanoparticles and adjusts the adsorption state of DPE. The results indicate that the metal modification inhibits the arenes hydrogenation at low temperatures but facilitates the C-O bond cleavage during heating (at low H2 pressures or an inert atmosphere). Ru-Cr/α-Al2O3 shows the highest reaction rate for DPE conversion at 1 MPa Ar and 200 °C. Moreover, Ru-Cr/α-Al2O3 not only efficiently converts different lignin model compounds by hydrogenolysis, but also achieves the controlled depolymerization of real lignin to generate guaiacols under mild conditions.