Bioethanol Production from Unpretreated Cellulose under Neutral Selfsustainable Hydrolysis/Hydrogenolysis Conditions Promoted by the Heterogeneous Pd/Fe3O4 Catalyst.

The direct conversion of untreated microcrystalline cellulose into C2-C3 alcohols, through a one-pot process promoted by the heterogeneous bimetallic Pd/Fe3O4 catalyst, is presented. The process is selfsustainable without the addition of external molecular hydrogen or acid/basic promoters and is mainly selective toward ethanol. At 240 °C, a complete cellulose conversion was reached after 12 h with an ethanol molar selectivity of 51% among liquid products. The synergistic effect played by water (which aids in the chemical pretreatment means of cellulose through the hydrolysis process) and the Pd/Fe3O4 catalyst (which catalyzes the hydrogenolysis reaction driving the pattern of obtained products) is elucidated.

Glycerol hydrogenolysis promoted by supported palladium catalysts.

Catalytic hydrogenolysis, with high conversion and selectivity, promoted by supported palladium substrates in isopropanol and dioxane at a low H(2) pressure (0.5 MPa), is reported for the first time. The catalysts, characterized by using BET isotherms, transmission electron microscopy (TEM), temperature-programmed reduction (TPR), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were obtained by coprecipitation and impregnation techniques. The coprecipitation method allows catalysts with a metal-metal or a metal-support interaction to be obtained, which enhances the catalytic performance for both the conversion of glycerol and the selectivity to 1,2-propanediol. Analogous reactions carried out with catalysts prepared by using impregnation are less efficient. A study of the solvent and temperature effect is also presented. The obtained results allow the hydrogenolysis mechanism to be inferred; this involves both the direct replacement of the carbon-bonded OH group by an incoming hydrogen or the formation of hydroxyacetone as an intermediate, which subsequently undergoes a hydrogenation process to give 1,2-propanediol. Finally, catalytic tests on a large-scale reaction at a higher H(2) pressure and recycling of the samples were carried out with the better performing catalysts (Pd/CoO and Pd/Fe(2)O(3) prepared by using coprecipitation) to verify possible industrial achievements.