•Hydrogenation of furfural to furfuryl alcohol in the presence of Pd/C and Ru/C.•The effect of carbon support nature on the formation of Pd and Ru sites.•The effect of supported metal on the ...catalytic performances of Pd/C and Ru/C.
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 0.5MPa. The 1.5% Pd/CNT catalyst was not active under mild conditions of the reaction (50°C, 0.5MPa), but had a greater tendency to reduce the furan ring under severe conditions (90°C, 0.5 or 2.0MPa) 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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The results of studies related to the development of synthesis, determination of formation conditions and elucidation of the mechanism of palladium–carbon catalyst action are integrated and ...critically analyzed. The attention is focused on Pd/NGC compositions (NGC is nanoglobular carbon). Methods for NGC preparation with an emphasis on its most common form, carbon black, are considered. The following issues are addressed: mechanisms of formation of carbon nanoglobules and their aggregates, methods of varying the size of nanoglobules, functionalization of the NGC surface to make it suitable as a support for palladium nanoparticles, views on the formation mechanism of palladium clusters and nanoparticles on the carbon support surface and effect of the structure and surface chemistry of carbon nanoglobules on the state of palladium sites in Pd/NGC compositions. The published data on selective hydrogenation of organic compounds in the presence of Pd/NGC catalytic compositions are integrated and systematized. The catalytic properties of Pd/NGC are analyzed in comparison with the properties of palladium catalysts supported on other carbon materials (activated carbon, carbon nanotubes). The influence of preparation conditions of NGC-based palladium compositions on their catalytic properties in practically important hydrogenation reactions is discussed. Promising trends for further research on the development of molecular design methods, study of the genesis of Pd/NGC compositions and extension of their applications in hydrogenation processes are considered. The bibliography includes 623 references.
Porous carbon–carbon composite materials (PCCCM) were synthesized by the alkaline dehydrochlorination of polyvinyl chloride solutions in dimethyl sulfoxide containing the modifying additives of a ...nanostructured component (NC): graphite oxide (GO), reduced graphite oxide (RGO) or nanoglobular carbon (NGC), with subsequent two-step thermal treatment of the obtained polyvinylene–NC composites (carbonization at 400 °C and carbon dioxide activation at 900 °C). The focus of the study was on the analysis and digital processing of transmission electron microscopy images to study local areas of carbon composite materials, as well as to determine the distances between graphene layers. TEM and low-temperature nitrogen adsorption studies revealed that the structure of the synthesized PCCCM can be considered as a porous carbon matrix in which either carbon nanoglobules (in the case of NGC) or carbon particles with the “crumpled sheet” morphology (in the case of GO or RGO used as the modifying additives) are distributed. Depending on the features of the introduced 5–7 wt.% nanostructured component, the fraction of mesopores was shown to vary from 11% to 46%, and SBET—from 791 to 1115 m2 g−1. The synthesis of PCCNC using graphite oxide and reduced graphite oxide as the modifying additives can be considered as a method for synthesizing a porous carbon material with the hierarchical structure containing both the micro- and meso/macropores. Such materials are widely applied and can serve as adsorbents, catalyst supports, elements of power storage systems, etc.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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•The effect of preparation conditions on the dispersion of metal in Pd/C catalyst.•TOF in hydrogenation of TNBA enhances with increasing in the particle size of Pd.•The effect of Pd ...particle size on the directions of TNBA transformation.
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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A facile direct deposition approach for the preparation of recyclable Pd/C catalysts simply by stirring a solution of tris(dibenzylideneacetone)dipalladium(0) with a suitable carbon material was ...evaluated. An extraordinarily rapid catalyst preparation procedure (<5 min) under mild conditions and its excellent performance in cross‐coupling and hydrogenation reactions were demonstrated. The key point for catalyst design is the direct deposition of Pd0 centers onto the highly accessible surface area and the avoidance of ill‐defined PdII/Pd0 states.
DIY catalysts: Efficient Pd/Carbon catalysts are prepared using a simple experimental procedure based on the direct deposition of Pd0 species from a commercially available tris(dibenzylideneacetone)dipalladium(0) complex. Application in cross‐coupling and hydrogenation reactions and easy catalyst recycling are demonstrated.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Hydrogenation of 2,4,6-trinitrobenzoic acid over Pd/Sibunit catalyst.•Identification of numerous reaction intermediates using NMR spectroscopy.•Scheme of transformations of substrate ...and intermediates in an aqueous medium.
Results of the catalytic hydrogenation of 2,4,6-trinitrobenzoic acid (TNBA) in the presence of 1% Pd/C catalyst with analysis of the reaction products at the steps corresponding to the consumption of 1, 3, 5, 6, 8 and 9mols of hydrogen per mol of TNBA are presented. Numerous reaction intermediates were identified using the 1H and 13C NMR spectroscopy; the reaction mixture composition was assessed quantitatively at different steps of the hydrogenation. The data obtained were used to propose a scheme of TNBA transformations over the Pd/C catalyst in the aqueous-phase reaction conditions. The data on the component composition at different steps of TNBA hydrogenation are important to understand the process chemistry, to explore the possibility of selective formation of different types of intermediate nitroamino compounds, and to synthesize high-performance catalysts for the hydrogenation of aromatic polynitro compounds.
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•Synergistic effect between Pd and Ru in benzaldehyde hydrogenation was observed.•Pd-Ru/NGC catalysts are highly selective for benzyl alcohol.•Pd-Ru/CNTs are highly active in ...hydrogenolysis of CO bonds.•The formation of Pd-Ru alloy is one of the reasons of synergistic effect.
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 CO 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 CO 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.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The effect of hydrothermal treatment (HTT) of gamma -alumina on the state of its surface functional cover, anchoring of hexachloroplatinate, and properties of platinum sites was investigated. ...Hydrothermal treatment of gamma -Al2O3 was found to increase the fraction of surface bridging OH groups and concentration of Lewis acid sites (LAS) and alter the metal complex-support interaction. Adsorption of hexachloroplatinate on the support surface is accompanied mainly by the formation of outer-sphere complexes, which are characterized by a lower reduction temperature. As a result, dispersion and electronic state of supported platinum are changed. Influence of gamma -Al2O3 hydrothermal treatment on the catalytic properties of Pt/Al2O3 in n-hexane transformations and propane dehydrogenation was demonstrated. The revealed effect of gamma -Al2O3 hydrothermal treatment on the formation of platinum sites in Pt/Al2O3 catalysts can be of fundamental importance for the steps of supported system synthesis where solid phase is contacting with water and aqueous solutions (impregnation and drying).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ni(Mg)Al-layered double hydroxides (LDH) were synthesized by coprecipitation. Structural properties of LDH and mixed oxides Ni(Mg)AlOx, obtained by LDH calcination, were studied by XRD and SEM. ...Textural properties of Ni(Mg)AlOx were studied by the nitrogen adsorption-desorption method. It was found that the formation of the single-phase LDH was occurred for any nickel content in the samples. The mixed oxides have a high specific surface area, the value of which decreases with increasing nickel content in the samples. Ni(Mg)AlOx are characterized by high activity in furfural hydrogenation. Selectivity of the formation of different reaction products depends on the nickel content in the catalysts. The full furfural conversion with the furfuryl alcohol selectivity no more than 65% was observed for the catalyst with a low nickel content. At the same time an increase in selectivity for furfuryl alcohol up to 84% occurs for the NiAl-catalyst with a furfural conversion not exceeding 43%.
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•Synthesis of single-phase Ni(Mg)Al-layered hydroxides by coprecipitation.•Structural and textural properties of the Ni(Mg)Al-layered hydroxides and their calcined forms.•High activity of the Ni(Mg)AlOx catalysts in the reaction of aqua-phase furfural hydrogenation.•Selectivity of products formation can vary by changing the nickel amount in the Ni(Mg)AlOx catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Some commercial chlorinated polymers can be transformed into carbon nanofibers by high power ion beam irradiation.•Two types of carbon nanofibers have been synthesized - continuous ...and “bamboo-like” nanofibers.•CNFs growth rate is 107 times higher than known methods.•The influence of dehydrochlorination of the polymer on synthesis of carbon nanofibers was investigated.
Carbon nanofibers (CNFs) have been rapidly synthesized on the surface of low-cost commercial chlorinated polymers (chlorinated polyvinyl chloride, polyvinyl chloride), which contains iron compounds, under the action of a high power ion beam at room temperature. Organic (Fe(C5H5)2) and inorganic (FeCl3⋅6H2O и Fe(NO3)3·9H2O) iron compounds were used as catalytic additions. SEM, TEM and Raman spectroscopy were used to investigate the morphologies and structure of irradiated polymers. CNFs had a most probable diameter in the range 50–90 nm and a maximum length of up to 10 μm. The maximum CNFs growth rate was estimated as 160 μm/μs. A possible growth mechanism for CNFs is discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
