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The condensation of ethanol to 1-butanol in the presence of different catalyst systems based on a Pd dehydrogenating/hydrogenating component and magnesium hydroxide-derived materials as basic ingredient was studied in a fixed-bed reactor. The metal was incorporated by wetness impregnation, and the resulting material was then reduced in situ with hydrogen at 573 K for 1 h before reaction. The bifunctional catalysts were tested in a fixed-bed reactor operated in the gas phase at 503 K and 50 bar with a stream of helium and ethanol. A bifunctional catalyst supported on a synthetic composite based on Mg and high surface area graphite (HSAG) was also studied. Improved catalytic performance in terms of selectivity towards 1-butanol and stability was shown by the Pd catalyst supported on the Mg-HSAG composite after thermal treatment in helium at 723 K, presumably due to the compromise between two parameters: adequate size of the Pd nanoparticles and the concentration of strongly basic sites. The results indicate that the optimal density of strongly basic sites is a key aspect in designing superior bifunctional heterogeneous catalyst systems for the condensation of ethanol to 1-butanol.

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A number of inorganic carbonaceous materials (activated carbon, high surface area graphite and graphenic materials) have been used as supports of Ru nanoparticles in order to determine their catalytic properties in the base-free aqueous-phase oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). In particular, we have studied in detail reduced graphene oxide (rGO) and nitrogen doped reduced graphene oxide (NrGO), which are the support materials that produce more selective ruthenium catalysts. Also the effects of different metal precursors used in the preparation of the Ru nanocrystallites have been evaluated. Both support materials and Ru catalysts were characterized by elemental analysis, nitrogen physisorption (BET), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The point of zero charge (PZC) for the graphenic materials was also determined. Interestingly the different supports significantly modify the catalytic performances, the graphenic materials being those that under our experimental reaction conditions produce the highest selectivity to FDCA. On these supports (rGO and NrGO) the highest HMF conversion was achieved by using triruthenium dodecacarbonyl as the ruthenium precursor. For the improved catalyst, Ru supported on NrGO, the yield of FDCA becomes close to 80%. This catalyst has been reused several times with neither loss of activity nor modification in selectivity values. Characterization data indicate these catalytic results can be correlated to the basic properties of the NrGO support as well as to the surface properties of Ru nanoparticles. These findings indicated that the metal precursor and the surface functional groups exposed on the support can modulate the catalytic properties, in particular amending the selectivity towards FDCA production.

Formic acid, a major product of biomass processing, is regarded as a potential liquid carrier for hydrogen storage and delivery. The catalytic dehydrogenation of FA to generate hydrogen using heterogeneous catalysts is of great interest. Ni based catalysts supported on silica were synthesized by incipient wet impregnation. The effect of doping with an alkaline earth metal (calcium) was studied, and the solids were tested in the formic acid decomposition reaction to produce hydrogen. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and programmed temperature surface reaction (TPSR). The catalyst doped with 19.3 wt.% of Ca showed 100% conversion of formic acid at 160 °C, with a 92% of selectivity to hydrogen. In addition, all the tested materials were promising for their application, since they showed catalytic behaviors (conversion and selectivity to hydrogen) comparable to those of noble metals reported in the literature.

Bifunctional catalysts supported over high-surface-area graphite comprising copper and a series of metallic oxides (MgO, BaO, ZnO, or MnO) that exhibit different acid/base properties were studied in the ethanol condensation reaction to 1butanol in a continuous flow reactor. This condensation reaction goes through the Guerbet mechanism, consisting of a multistep process based on hydrogenation/dehydrogenation reactions as well as base-catalyzed aldol condensation and acid-catalyzed dehydration reactions. The catalytic tests were performed in a fixed-bed reactor working in the gas phase at 50 bar and 503 K. The catalyst 5Cu-Mn/G exhibited the highest yield toward 1-butanol followed closely by 5Cu-Mg/G, unlike their counterparts with BaO and ZnO as the metal oxide. The cooperative action between the metal function as the hydrogenating/dehydrogenating agent and the suitable quantity of medium-high-strength basic sites and medium-weak-strength acid sites is responsible for the highest 1butanol yields.

A one-pot three-component synthesis of dihydropyrimidinones (DHPMs) via Biginelli reaction was carried out at 100 °C using benzaldehyde, ethyl acetoacetate and urea as reactants, in the presence of ethanol and free solvent, in heterogeneous catalytic medium. The Mo (30 wt%) metal oxides (Al2O3, SiO2 or MgO) used catalysts were prepared by sol-gel, impregnation and microemulsion methods and characterized by X-Ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX), Nitrogen Adsorption - Brunauer-Emmett-Teller (BET), and NH3-Temperature Programmed Desorption (TPD) methods. The Mo-SiO2 sample prepared by the sol-gel method exhibited the highest DHPM yield (87%), in free solvent with a reaction time of 30 min. The high efficiency, in the Biginelli reaction, of the Mo-SiO2 catalyst is due to its structural, textural and acid properties. Highly dispersed αMoO3 species of orthorhombic structure having a high contribution of strong acidic sites would be the active species in the Biginelli synthesis  Copyright © 2020 BCREC Group. All rights reserved