The surface structures of ReO x supported on CeO 2 at low loadings have been elucidated through 18 O isotopic exchange Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ReO x is present in four distinct structures, a di-oxo structure with two ReO terminal bonds, a mono-oxo species that contains one ReO terminal bond, a mono-oxo species that contains a hydroxyl group, and a crosslinked ReO x species. The isotopic exchange Raman spectroscopy shows a red shift resulting from the 18 O exchange in the OReO, ReO, Re−OH, and Re−O−Re species, which allowed for the deconvolution of the various structures. Time-resolved DRIFTS showed significant exchange of 18 O over time and reconfirmed the results from the Raman spectroscopy. The presence of multiple surface species supports the existence of competing reaction mechanisms for the simultaneous hydrodeoxygenation over the ReO x −Pd/ CeO 2 catalyst and deoxydehydration over the ReO x /CeO 2 catalyst.

In this study, we demonstrate that for the simultaneous hydrodeoxygenation (HDO) of 1,4-anhydroerythritol a comparable yield of tetrahydrofuran is obtained at half the previously reported H2 pressure. The simultaneous hydrodeoxygenation was conducted using a heterogeneous ReO x –Pd/CeO2 catalyst. An L9 Taguchi design of experiment was enacted to elucidate the temperature, pressure, and catalyst loading effects on the yield of the HDO reaction by testing pressures ranging from 40 to 80 bar H2, temperatures of 100–180 °C, and Re loadings of 2–4 wt %. Our design showed that the yield of this reaction is significantly affected by the reaction temperature only. An L9 Taguchi design was conducted for xylitol simultaneous hydrodeoxygenation with pressures ranging from 5 to 10 bar H2, temperatures of 140–180 °C, and Re loadings of 2–4 wt %. The xylitol design elucidated the direct relation of pressure, and the inverse relation of temperature and catalyst loading, to yield with the optimal reaction condition being 140 °C and 10 bar H2.

Selective removal of oxygen from biomass-derived polyols is critical toward bridging the gap between biomass feedstocks and the production of commodity chemicals. In this work, we show that earth-abundant molybdenum oxide based heterogeneous catalysts are active, selective, and stable for the cleavage of vicinal C–O bonds in biomass-derived polyols. Catalyst characterization (Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)) shows that partially reduced MoO x centers are responsible for C–O bond cleavage and are generated in situ by hydrogen dissociated atoms over palladium (Pd) nanoparticles. We find that the support, TiO2, facilitates communication between the hydrogen dissociating metal and dispersed MoO x sites through hydrogen spillover. Reactivity studies using a biomass-derived model substrate (1,4-anhydroerythritol) show the effective removal of vicinal hydroxyls over MoO x -Pd/TiO2 producing tetrahydrofuran with >98% selectivity at 29% conversion. Catalyst stability is demonstrated upon cycling. These studies are critical toward the development of low-cost heterogeneous catalysts for sustainable hydrodeoxygenation of biobased polyols to platform chemicals.

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Thermochemical conversion of tobacco residues to value-added bio-fuels and chemicals via fast pyrolysis, in combination with torrefaction pretreatment, in a rotating blade ablative reactor under vacuum conditions.