Molecular Ruthenium Cyclopentadienone Bifunctional Catalysts for the Conversion of Sugar Platforms to Hydrogen

Molecular ruthenium cyclopentadienone complexes were employed for the first time as pre-catalysts in the homogeneously catalysed Aqueous Phase Reforming (APR) of glucose. Shvo's complex resulted the best pre-catalyst (loading 2 mol %) with H₂ yields up to 28.9 % at 150 °C. Studies of the final mixture allowed to identify the catalyst's resting state as a mononuclear dicarbonyl complex in the extracted organic fraction. In situ NMR experiments and HPLC analyses on the aqueous fraction gave awareness of the presence of sorbitol, fructose, 5-hydroxymethylfurfural and furfural as final fate or intermediates in the transformations under APR conditions. These results were summarized in a proposed mechanism, with particular emphasis on the steps where hydrogen was obtained as the product. Benzoquinone positively affected the catalyst activation when employed as an equimolar additive.