Controlling transformation of sorbitol into glycols over Ru-WO_x modified biomass-derived N-doped carbon

Glycols, such as 1,2-propanediol (1,2-PDO) and ethylene glycol (EG), are considered as a kind of essential intermediates for producing high-value fine chemicals. The direct conversion of biomass derivatives into glycols is still a great challenge for the chemical industry. In this study, we developed an efficient and green process for synthesizing bimetallic Ru/WO_x modified biomass-derived N-doped carbon catalysts (Ru/WNC) by tandem hydrothermal carbonization of bamboo shoot, thermal pyrolysis and hydrothermal reduction process. The structure, surface properties, and catalytic activity of Ru/WNC catalyst for sorbitol hydrogenolysis to 1,2-PDO and EG in an aqueous alkaline solution with Ca(OH)₂ as base promoter were studied in detail. Results displayed that N incorporation would lead to ligand effects by combining with the active metal Ru and WO_x. The introduction of WO_x would promote Ru nanoparticles with small size (~ 2.4 nm) well distributed on the carbon surface, as well as improve the capability of hydrogen spillover. Meanwhile, Ca(OH)₂ and rich basic W⁵⁺ sites on Ru/WNC would promote the cleavage of the C–C bonds by the retro-aldol condensation. As a result, the bimetallic catalyst has demonstrated superior hydrogenolysis activity for 1,2-PDO and EG formation in a basic medium. The highest sorbitol conversion (75.4%) and the total selectivity of 1,2-PDO and EG (84.6%) were achieved by the cooperative action of metallic Ru and WO_x species. The possible reaction mechanism of Ru/WNC in the basic medium was also discussed. This study provides informative principles for the design of efficient hydrogenolysis catalysts for biomass-derived glycols production.