ReO_x/TiO₂: An Efficient Catalyst for the Production of Butanediols From Erythritol in Water

This work reports the use of non noble monometallic heterogeneous catalysts for the efficient hydrodeoxygenation of erythritol (ERY) toward butanediols in aqueous media. ERY is a biosourced polyols of growing interest, as it can be selectively converted into valuable C₄ molecules, particularly butanediols (BDO), which are key building blocks for polymer synthesis. However, achieving high BDO selectivity remains challenging due to the complex reaction network leading to multiple by-products. The catalysts developed in this study consist of rhenium nanoparticles supported on titania materials with different crystallographic phases. These ReO_x/TiO₂ catalysts were prepared by wet impregnation and thoroughly characterized using inductively coupled plasma optical emission spectroscopy, XRD, thermogravimetric analysis, XPS, STEM, H₂-TPR, and NH₃-TPD to elucidate the influence of TiO₂ crystallinity on rhenium dispersion, reducibility, acidity, metal-support interactions, and catalytic behavior. Among the tested materials, ReO_x/TiO₂ based on mixed-phase TiO₂ (P25, anatase-rutile) exhibited optimal physicochemical properties, enabling efficient CO bond cleavage. Under 240°C and 60 bar H₂, it achieved 98% ERY conversion with 55% selectivity toward BDO after 6 h. Mechanistic investigations revealed that the catalyst promotes simultaneous removal of vicinal hydroxyl groups through deoxydehydration, accounting for the high selectivity toward 1,2-BDO. Continuous-flow tests demonstrated excellent stability without rhenium leaching.