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Mono- and bimetallic UiO-66 nanocatalysts were synthesized using the solvothermal synthesis method and evaluated in the aldol condensation reaction of benzaldehyde and acetone in a batch reactor. N2 physisorption, thermogravimetric analysis, temperature-programmed desorption of ammonia, X-ray diffraction, field-emission scanning electron microscopy–energy-dispersive X-ray, X-ray photoelectron spectroscopy, potentiometric titration, and Fourier transform infrared were used to characterize the nanocatalysts. The higher activity exhibited by the Zr/Hf-UiO-66 catalyst could be attributed to the lower orbital energy interaction with benzaldehyde, as shown by density functional theory. A synergetic effect is observed for the bimetallic UiO-66 nanocatalyst between Zr and Hf, obtaining a higher reaction rate than the monometallic nanocatalysts. Meanwhile, this antagonistic effect was shown in the bimetallic catalysts between Zr and Ce, which was less active than the monometallic UiO-66 catalyst due to free COOH generated during the synthesis. Finally, the selectivity results showed that incorporating Hf and Ce on Zr-UiO-66 favors benzalacetone formation by cross-coupling condensation of benzaldehyde and acetone at isoconversion conditions. [ABSTRACT FROM AUTHOR]

The catalytic performance of Ru impregnated perovskites‐based catalysts (Ru/SrZrO3 and Ru/BaZrO3) in the conversion of levulinic acid (LA) into higher valuable chemicals was carried out at different reaction temperatures. The Ru/SrZrO3 and Ru/BaZrO3 catalysts, with a loading of 2.0 Ru atoms nm−2, were prepared by incipient impregnation, and characterized by different techniques. The characterization results indicate presence of dispersed Ru catalysts, with a crystalline structure, with absence of carbonate species for Ru/SrZrO3 and larger carbonates as segregated phase and with stronger basic sites for Ru/BaZrO3. At higher reaction temperatures (200 °C – 250 °C), the higher strength of the basic sites of Ru/BaZrO3 had a direct influence on the levulinic acid (LA) conversion reaction. Differences in the apparent activation energy (Eap) values follow the same trend. The catalysts produce a 100 % of selectivity towards GVL. The formation of GVL was proposed to proceed via the intermediacy of 4‐hydroxypentanoic acid due to the presence of basic surface sites. [ABSTRACT FROM AUTHOR]

The synthesis of methanol by carbon dioxide hydrogenation has been studied using copper-molybdenum carbides supported on high surface area graphite, reduced graphene oxide and carbon nanotubes. The synthesis conditions and the effect of the support were studied. The catalysts were prepared in situ using H2 or He at 600 °C or 700 °C. Both molybdenum carbide and oxycarbide were obtained. A support with less reactive carbon resulted in lower proportion of carbide obtained. The best results were achieved over a 5 wt.% Cu and 10 wt.% Mo on high surface area graphite that reached 96.3% selectivity to methanol. [ABSTRACT FROM AUTHOR]

A new two-step solution route has been developed for the preparation of hollow inorganic fullerene-like (IF) MoS2 particles with a quantitative yield. First, core–shell MoSx/ZnS (x∼ 3–4) particles were synthesized by depositing amorphous MoSx on the ZnS seeds in a solution containing ethylene glycol and elemental sulfur. Core–shell particles contain a 7–9 nm size ZnS core surrounded with an amorphous MoSx sulfide shell. Then the core–shell particles were thermally treated at 400–750 °C. As a result, 20–50 nm size IF-like MoS2 particles were crystallized, whereas ZnS left the interior of the particles and formed bulky crystals aside. At the moment of ZnS crystallization a burst-out of the MoS2 walls occurs and the resulting IF particles contain openings, which make the internal voids accessible for gas adsorption. By means of varying the Mo/Zn ratio in the solvothermal reaction mixture, the number of slabs in the onion-like particles can be controlled. Due to the intermediate presence of the ZnS core, relatively large voids are created in the resulting IF-MoS2. The solids as obtained possess high specific surface area, enhanced thiophene HDS activity and exceptional thermal stability. Particle size and wall thickness can be controlled by means of variation of the Mo/Zn atomic ratio in the solution. [ABSTRACT FROM AUTHOR]