In MgO–SiO2 catalysts for the transformation of bio-ethanol into butadiene, the generation of more selective sites is achieved by the dispersion of isolated Si4+ atoms in MgO.

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In this study we explore the use of Ga as a new component in MgO‐SiO2 catalysts for the Lebedev reaction (the one‐pot conversion of ethanol to butadiene). Several characterisation techniques (XRD, temperature‐programmed desorption of NH3, BET measurements, IR spectroscopy) and in situ spectroscopic studies (DRIFTS‐MS) were performed with the aim to correlate the properties of the modified materials with the catalytic results. We concluded that the wet impregnation of Ga3+ on the MgO‐SiO2 catalyst creates new Ga−O(H)−Si sites. These sites interact strongly with alcohol and not only facilitate its dehydrogenation to acetaldehyde and its transformation into the intermediate crotyl alcohol but also enhance the dehydration of the latter because of an improved acidity. However, an appropriate amount of gallium oxide is needed to avoid excessive acidity, which is conducive to an increased selectivity to ethylene.

The visible‐light‐mediated photo‐catalytic selective valorisation of glucose using TiO2‐supported Ag nanoparticles is shown for the first time. The optimisation of the catalyst composition, substrate‐to‐catalyst ratio and reaction medium proved that a near total suppression of the mineralisation pathway could be achieved with a selectivity to partial oxidation products and small‐chain monosaccharides as high as 98 %. The primary products were determined to be gluconic acid, arabinose, erythrose, glyceraldehyde and formic acid. Under UVA light, the selectivity to organics decreases because of the production of CO2 from mineralisation. A reaction mechanism is proposed based on an α‐scission process combined with the Ruff degradation reaction, which explains the presence of the oxidation products, the smaller carbohydrates and formic acid. X‐ray photoelectron spectroscopy, UV/Vis spectroscopy and microscopy studies showed the presence of plasmonic 4 nm particles of silver that were oxidised to silver oxide over the course of the reaction, and recycling studies revealed that this was not detrimental to activity.

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