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• Controllable activity and selectivity of Pd/C hydrogenation catalysts. • Effect of the carbon support on the structure and catalytic properties of Pd NPs. • Effect of the Pd precursor on the structure and catalytic properties of Pd NPs. • Addition of a second metal and the synergistic effect in Pd-based bimetallic catalysts. Carbon-supported palladium catalysts are widely used for hydrogenation of various organic compounds in the fine chemical industry. The nanoscale geometry and electronic structure of supported Pd nanoparticles play a crucial role in providing the necessary catalytic properties. To improve catalytic activity and selectivity of Pd nanoparticles, it is possible to fine tune their intrinsic properties (e.g., size and oxidation state) by controlling the chemical transformations at different stages of catalyst preparation. Recent years have seen considerable advancement in developing new catalyst preparation techniques as well as in understanding the mechanism of active site formation. This review summarizes some of the existing approaches to regulating the catalytic properties of carbon-supported palladium by variation of the carbon support, the composition of palladium precursor and its reduction conditions, as well as the addition of a second active metal. The data presented may be useful for researchers developing efficient Pd/C catalysts for hydrogenation of polyfunctional organic compounds. [ABSTRACT FROM AUTHOR]

• MgAl-layered hydroxides were synthesized on the surface of γ-Al 2 O 3 using its Al atoms. • Modification of alumina changed the mechanism of [PtCl 6 ]2− anchoring. • Adsorption occurs with localization of 2–4 nm platinum particles in the MgAl-phase. • Catalyst with supported LDH provides a higher stability in propane dehydrogenation. Layered magnesium-aluminum hydroxides of hydrotalcite-like structure were synthesized on the surface of γ-Al 2 O 3. The synthesis was performed via the interaction of aluminum and magnesium hydroxides and carbonate ions in the pores of alumina support. Novelty of the approach was that the synthesis involved the boehmite phase AlO(OH) that formed directly on the surface of γ-Al 2 O 3 under hydrothermal conditions. This approach provides fixation of the forming layered phase on the surface of initial support and retains textural parameters of the support. The formation of a layered structure on the γ-Al 2 O 3 surface was confirmed by XRD analysis and electron microscopy studies. Investigation of the H 2 [PtCl 6 ] anchoring on γ-Al 2 O 3 with supported magnesium-aluminum hydroxide by UV–vis DRS, 195Pt NMR and HRTEM showed that platinum was adsorbed on the surface as chloride forms of the complexes with a low degree of hydrolysis even at a low metal content. Catalytic properties of the synthesized supported platinum catalysts were examined in a model reaction of propane dehydrogenation. In comparison with the alumina-platinum catalyst, the modified sample showed a better stability at a somewhat higher yield of propylene because the formation of heavy products was suppressed. [ABSTRACT FROM AUTHOR]

The effect of the nature of alkaline agent and pH value of hydrolysis of Pd(II) chloride complex into palladium polynuclear hydroxo complexes, as precursor of active component in Pd/C catalyst, on the dispersion of palladium particles supported on carbon material Sibunit was revealed. It was shown that an increase in the particle size of supported palladium enhances the specific catalytic activity in hydrogenation of 2,4,6-trinitrobenzoic acid and changes the direction of the transformation (increases the fraction of non-aromatic intermediate, cyclohexane-1,3,5-trione trioxime, in the products). The results obtained are essential for optimizing the particle size of supported palladium in selective hydrogenation of polyfunctional organic compounds. [ABSTRACT FROM AUTHOR]

Bimetallic Pd-Ru/C catalysts prepared with different carbon supports were shown to be much more active in the liquid-phase hydrogenation of benzaldehyde in comparison with their monometallic analogs. In the case of systems based on nanoglobular carbon, the synergistic effect manifested itself as an increased selectivity for benzyl alcohol (86–90%) at a complete conversion of benzaldehyde, whereas the catalysts containing carbon nanotubes were highly active in hydrogenolysis of the C O bonds, which caused an increased yield of toluene (up to 56%). The synergistic effect between palladium and ruthenium in the reaction under study can be related to the changes in the electronic and dispersion state of the supported metals upon interaction with each other and formation of Pd-Ru alloy. In terms of the electronic factor, the enhanced catalytic performance of bimetallic systems can be a result of facilitation of electrophilic activation of the C O bond in benzaldehyde owing to an increased fraction of the electron-deficient palladium species. The nature of carbon support was shown to affect the electronic state of supported metals and thus catalytic properties of bimetallic Pd-Ru/C systems. [ABSTRACT FROM AUTHOR]

The study considered the formation and catalytic properties of the active sites in Pd/C and Ru/C catalysts supported on carbon nanotubes (CNT) and carbon black (CB). The nature of carbon support was shown to affect the dispersion of supported metal and its catalytic properties in the aqueous-phase hydrogenation of furfural. The 1.5% Pd/CB catalyst demonstrated a high selectivity (99%) for furfuryl alcohol during hydrogenation of furfural at a temperature of 50 °C and hydrogen pressure of 0.5 MPa. The 1.5% Pd/CNT catalyst was not active under mild conditions of the reaction (50 °C, 0.5 MPa), but had a greater tendency to reduce the furan ring under severe conditions (90 °C, 0.5 or 2.0 MPa) as demonstrated by an increased yield of tetrahydrofurfuryl alcohol. The ruthenium samples showed a low activity in aqueous-phase hydrogenation of furfural irrespective of the support nature and reaction conditions, possibly due to irreversible adsorption of water on the active sites. [ABSTRACT FROM AUTHOR]