Pd-loaded two-dimensional NiO nanosheet zeolite catalyst for selective hydrogenolysis of sorbitol to produce 1,2-propanediol and ethylene glycol

Abstract

1,2-propanediol (1,2-PDO) and ethylene glycol (EG), as key precursors for high-value fine chemicals, represent one of the core challenges in green chemical engineering through the development of biomass-directed conversion systems. This study constructed a bifunctional x%NiO@Hβ-1 %Pd hierarchical porous catalyst through an interfacial engineering strategy: utilizing the confinement effect of two-dimensional mesoporous nickel silicate nanosheets to load Ni onto Hβ zeolite, and anchored highly dispersed Pd nanoparticles on the NiO@Hβ surface through NaBH₄-induced in situ reduction, systematically investigated the structure-activity relationship of this catalyst for sorbitol hydrogenolysis in Ca(OH)₂ alkaline aqueous systems. Combined NH₃-TPD and N₂ adsorption-desorption characterization revealed that, the introduction of Hβ zeolite significantly modulated the catalyst acidity and pore structure—the total acid amount of 25 %NiO@Hβ-1 %Pd reached 4.13 mmol/g (representing a 104 % enhancement compared to the support-free system), the desorption peak at 550°C corresponds to strong Lewis acid sites formed by Ni-O-Si bonds, the pore system with 69 % mesopore content (BET specific surface area of 541.6 m²/g) provides efficient transport pathways for reactant diffusion. Mechanistic studies revealed that, the Brønsted acid sites of Hβ selectively adsorb sorbitol C-O bonds through hydrogen bonding interactions, while spillover hydrogen species at the Pd-Ni interface synergistically induce selective C-C bond cleavage in cooperation with strong Lewis acid sites, ultimately achieved a total diol carbon yield of 80.3 C% for 1,2-PDO/EG under conditions of 220°C and 3 MPa H₂. This work provides new insights into the “acid-metal-mass transfer” ternary synergistic mechanism for precise hydrogenolysis of biomass polyols.