Morphologically Cross‐Shaped Ru/HZSM‐5 Catalyzes Tandem Hydrogenolysis of Guaiacol to Benzene in Water

Abstract

AbstractHydrogenolysis of C−O bonds is an important tool for synthesis of valuable fuels and chemicals from biomass. In this contribution, we report that morphologically cross‐shaped HZSM‐5‐loaded Ru nanoparticles have demonstrated high activity in the selective hydrogenolysis of guaiacol to benzene in water with 97 % yield and a rate of 7.8 g g−1 h−1 accompanied with high durability. N2 sorption analysis showed that Ru/HZSM‐5 (cross‐shaped) had a large mesoporous surface area and pore volume for loading small and uniform Ru nanoparticles, as confirmed by TEM images. The stronger interaction of Ru and cross‐shaped HZSM‐5 was simultaneously confirmed by a higher hydrogen reduction temperature of RuO2 on calcined Ru/HZSM‐5, a blueshift of Ruδ+‐(CO)n, Ruδ+‐(CO), and Ru0‐(CO) species in the IR spectra of adsorbed CO, and a higher Ru 3d5/2 binding energy in X‐ray photoelectron spectroscopy measurements. The reaction constant in guaiacol hydrogenolysis to phenol over cross‐shaped Ru/HZSM‐5 (0.051 min−1) was 3–4 times higher than that on spherical and cuboid Ru/HZSM‐5 (0.012–0.029 min−1) at identical conditions, attributed to the remarkable hydrogenolysis catalytic capability of Ru nanoparticles on cross‐shaped HZSM‐5. In addition, adsorption of guaiacol and hydrogen was more substantial on cross‐shaped Ru/HZSM‐5, as evidenced by of IR and mass spectroscopy, respectively. The higher adsorption of guaiacol is attributed to the abundant Lewis acid sites on cross‐shaped Ru/HZSM‐5, as the Al−OH enriched Lewis acid sites favor the adsorption of oxygen‐containing guaiacol. The higher rate constant in the primary step, together with the adsorbed high concentrated reactant and hydrogen (with nearly first‐order reaction kinetics) on cross‐shaped Ru/HZSM‐5, facilitates the overall tandem reaction, leading to an excellent hydrogenolysis catalyst working at hydrothermal conditions for biomass conversion.