Ru/TiO₂ Catalyzed High‐Yield Synthesis of Furanic Diols by 5‐Hydroxymethylfurfural Hydrogenation with Switchable Selectivity

Abstract 5‐Hydroxymethylfurfural (HMF) is a versatile platform molecule that can be derived from biomass feedstocks and catalytically converted into various value‐added chemicals. In this work, selective hydrogenation of HMF is investigated to produce valuable furan‐based diols, namely 2,5‐bis‐hydroxymethylfuran (BHMF) and 2,5‐bis‐hydroxymethyltetrahydrofuran (BHMTHF), using TiO 2 supported Ru catalysts. The catalyst performance was fine‐tuned to achieve over 98% yield to BHMF and BHMTHF under optimized reaction conditions with very good recyclability. We pointed out several key factors allowing to maximize the yield towards the respective diols. Features such as the Ru nanoparticle size, the strength of metal‐support interactions and the presence of residual chlorine were found to significantly influence the reaction. A characteristic volcano‐shaped relationship was obtained between the particle size and the catalytic activity giving the highest diol yield for an optimum Ru nanoparticle size of 1.6 nm. Further, metal‐support interactions were found to be responsible for providing optimum Ru‐TiO x interfacial surface sites and chlorine was affecting the electronic properties of Ru nanoparticles, potentially benefiting to the selective formation of BHMF. The reaction time was shown to control the hydrogenation of the furan ring and the selectivity of the reaction, that can be directed optimally towards BHMF or BHMTHF.