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Selective hydrogenation of substituted nitroaromatic compounds is an extremely important and challenging reaction. Supported metal catalysts attract much attention in this reaction because the properties of metal nanoparticles (NPs) can be modified by the nature of the support. Herein, the support morphology on the catalytic performance of selective hydrogenation of 3‐nitrostyrene to 3‐vinylaniline was investigated. Pt NPs supported on octadecahedral α‐Fe2O3 supports with a truncated hexagonal bipyramid shape (Pt/α‐Fe2O3‐O) and rod‐shaped α‐Fe2O3 supports (Pt/α‐Fe2O3‐R) were prepared by glycol reduction method. Detailed characterizations reveal that the electronic structure and dispersion of Pt NPs can be modified by the supports. The Pt/α‐Fe2O3‐O catalyst exhibited superior catalytic performance for hydrogenation of 3‐nitrostyrene because of its low coordinated Pt sites and the small Pt NPs size, which is benefit from the high‐index exposed surfaces of truncated hexagonal bipyramid‐shaped α‐Fe2O3 support. The structural evolution during the catalytic reaction was investigated in detail by identical location transmission electron microscopy (IL‐TEM) method, which found that the high cycling activity of Pt/α‐Fe2O3‐O catalyst during the cycle experiment results from the stability of Pt NPs. [ABSTRACT FROM AUTHOR]

Metallic platinum nanocatalysts play a key role in the liquid‐phase selective hydrogenation of substrates with more than one unsaturated bond. However, the commonly applied explanation for the effects of different electronic and geometric properties of catalysts on reactions remains of a heuristic nature due to the difficulties involved in preparing catalysts with precise structure. In this work, we have directly loaded pre‐synthesized metallic platinum nanoparticles onto well‐structured ZnO nanorods and then subjected them to thermal treatment in a reductive atmosphere for different temperatures. The effects of the different electronic and geometric properties of the catalysts on the selective reduction of 3‐nitrostyrene to 3‐vinylaniline as a model reaction have been rigorously explored through an analysis of the catalyst structures and the activity and selectivity profiles. Both the electron transfer from zinc to platinum and the decreased platinum surface density as a result of the formation of PtZn intermetallic compounds are key factors for improving the selectivity for the desired 3‐vinylaniline. Azobenzene was detected in the reaction with all the Pt/ZnO catalysts after 10–90 min, which indicates that the reaction follows a condensation mechanism. [ABSTRACT FROM AUTHOR]

Supported bimetallic PdxCuy catalysts with precisely controlled Pd/Cu ratios were prepared and characterized by combining sample averaged and microscopic techniques. The active-site isolation effect on reactivity and reaction pathway control with different extent of Pd ensembles in acetylene hydrogenation is unravelled systematically. [ABSTRACT FROM AUTHOR]

The varied surface structures of a Pd catalyst showed different catalytic performances in the partial hydrogenation of acetylene. The exposed Pd (1 0 0) facet is considered to be the most selective of all other facets for the formation of ethylene, but it is unstable and the fine structure needs to be revealed during the reaction. Herein, the evolution of the surface structure of cubic Pd nanoparticles, which are all bound with (1 0 0) facets, was studied by transmission electron microscopy in the partial hydrogenation of acetylene. Furthermore, the relation between the varying surface structure and the activity/selectivity was correlated. The (1 0 0) facets of Pd were transformed into stepped facets during the reaction, derived by adsorption/desorption of the reactants and energy compensation, which was the main reason for the decrease in the selectivity towards ethylene. [ABSTRACT FROM AUTHOR]

A composite catalyst including palladium nanoparticles on titania (TiO2) and on nitrogen-modified porous carbon (Pd/TiO2@NC) is synthesized from palladium salts, tetrabutyl titanate, and chitosan. N2 sorption isotherms show that the catalyst has a high BET surface area (229 m2 g−1) and large porosity. XPS and TEM characterization of the catalyst shows that palladium species with different chemical states are well dispersed across the TiO2 and nitrogen-modified porous carbon, respectively. The Pd/TiO2@NC catalyst is very active and shows excellent stability towards hydrogenation of vanillin to 2-methoxy-4-methylphenol using formic acid as hydrogen source. This activity can be attributed to a synergistic effect between the Pd/TiO2 (a catalyst for dehydrogenation of formic acid) and Pd/NC (a catalyst for hydrogenation of vanillin) sites. [ABSTRACT FROM AUTHOR]

A series of gallia-supported Pd-Ga catalysts that consist of metallic nanoparticles on three porous polymorphs of Ga2O3 (α-, β-, and γ-Ga2O3) were synthesized by a controlled co-precipitation of Pd and Ga. The effects of formation of Ga-Pd intermetallic compounds (IMCs) were studied in four catalytic reactions: methanol steam reforming, hydrogenation of acetylene, and methanol synthesis by CO and CO2 hydrogenation reactions. The IMC Pd2Ga forms upon reduction of α- and β-Ga2O3-supported materials in hydrogen at temperatures of 250 and 310 °C, respectively. At higher temperatures, Ga-enrichment of the intermetallic particles is observed, leading to formation of Pd5Ga3 before the support itself is reduced at temperatures above 565 °C. In the case of Ga-Pd/γ-Ga2O3, no information about the metal particles could be obtained owing to their very small size and high dispersion; however, the catalytic results suggest that the IMC Pd2Ga also forms in this sample. Pd2Ga/gallia samples show a stable selectivity towards ethylene in acetylene hydrogenation (≈75 %), which is higher than for a monometallic Pd reference catalyst. An even higher selectivity of 80 % was observed for Pd5Ga3 supported on α-Ga2O3. In methanol steam reforming, the Ga-Pd/Gallia catalysts showed, in contrast to Pd/Al2O3, selectivity towards CO2 of up to 40 %. However, higher selectivities, which have been reported for Pd2Ga in literature, could not be reproduced in this study, which might be a result of particle size effects. The initially higher selectivity of the Pd5Ga3-containing samples was not stable, suggesting superior catalytic properties for this IMC, but that re-oxidation of Ga species and formation of Pd2Ga occurs under reaction conditions. In methanol synthesis, CO hydrogenation did not occur, but a considerable methanol yield from a CO2/H2 feed was observed for Pd2Ga/α-Ga2O3. [ABSTRACT FROM AUTHOR]

Abstract: Uniformly dispersed ruthenium nanoparticles supported on non-functional carbon nanotubes (CNT) have been successfully synthesized by using a facile and solvent-free microwave-assisted thermolytic method with dodecacarbonyltriruthenium as the precursor. The results show that 2–4nm sized spheres of Ru nanoparticles were uniformly dispersed and supported on non-functional CNT by several minutes'' exposure to microwave irradiation without solvent. The Ru/CNT catalysts show the desired conversion of about 80% and selectivity to hydrocinnamaldehyde of about 72% in the selective hydrogenation of cinnamaldehyde, where the catalytic performance has been found to depend on both the Ru loading and the surface properties of CNT. [Copyright &y& Elsevier]

Supported gold nanoparticles are emerging catalysts for heterogeneous catalytic reactions, including selective hydrogenation. The traditionally used supports such as silica do not favor the heterolytic dissociation of hydrogen on the surface of gold, thus limiting its hydrogenation activity. Here we use gold catalyst particles partially embedded in the pore walls of mesoporous carbon with carbon atoms occupying interstitial sites in the gold lattice. This catalyst allows improved electron transfer from carbon to gold and, when used for the chemoselective hydrogenation of 3-nitrostyrene, gives a three times higher turn-over frequency (TOF) than that for the well-established Au/TiO2 system. The d electron gain of Au is linearly related to the activation entropy and TOF. The catalyst is stable, and can be recycled ten times with negligible loss of both reaction rate and overall conversion. This strategy paves the way for optimizing noble metal catalysts to give an enhanced hydrogenation catalytic performance. Gold is among the least active metals toward molecules at a solid-liquid or solid-gas interface. Here the authors demonstrate that the gold nanocatalysts with d electron gain due to C occupying interstitial sites in its lattice boost catalytic hydrogenation. [ABSTRACT FROM AUTHOR]

• Optimized Pt x Co y -oCNTs were synthesized by a modified oleyamine reduction method. • With the decrease of Pt/Co ratio, the selectivity of C = O bonds increased obviously. • The structural evolution of catalyst was studied by identical location TEM method. The selective hydrogenation of cinnamaldehyde (CAL) is an extremely important transformation. Herein, oxygen functionalized carbon nanotubes (oCNTs) supported a series of Pt x Co y bimetallic nanoparticles (NPs) with varied Pt to Co ratios were synthesized. The introduction of Co significantly affects the electronic structure of Pt NPs, which clearly promotes the selectivity to cinnamyl alcohol (COL). Among all Pt x Co y -oCNTs catalysts, PtCo 3 -oCNTs exhibited the best catalytic performance and a selectivity of over 76% towards COL at a CAL conversion of 99% was obtained. Further characterization of the fresh, used and cycled catalysts revealed that the NP structures were stable and did no change. The structural evolutions during the catalytic reaction were also investigated by identical location transmission electron microscopy (IL-TEM) method in detail, which found that the deactivation of PtCo 3 -oCNTs catalyst during the cycle experiment results from the agglomeration and detachment of PtCo 3 NPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultra-dilute HEA with core–shell structure was synthesized via reduction temperature driven. • The role of each constituent metal site in ultra-dilute HEA was studied. • Atomically dispersed Zn and electron-rich Cu resulted in 87.32% furfuryl alcohol yield at 90℃. • Cu precipitation in ultra-dilute HEA inhibited the selective hydrogenation of furfural. • DFT proved atomically dispersed Zn was the active sites for the adsorption of furfural. Furfuryl Alcohol (FOL) from the catalytic hydrogenation of furfural represented a promising intermediate for industrial application. However, the high selectively of FOL in mild temperature was limited due to the over hydrogenation. Here, we synthesized the novel ultra-dilute high-entropy alloys (HEAs) with multiple metal sites and core–shell structure for boosting the selectivity of furfural hydrogenation to furfuryl alcohol. The results showed that the furfural was converted to FOL with the conversion of 87.32% and selectivity of 100% at 90℃ over ultra-dilute HEA (NiCoCuZnFe/C-800). The catalyst had redistribution of electrons between Cu (2.00) and atomically dispersed Zn (1.65) due to the different electronegativity. The electron-rich Cu repelled the furan ring and prevented the over hydrogenation, while the atomically dispersed Zn presented the strongest –CHO adsorption performance. Moreover, the core–shell structure enhanced the stability of the catalysts during hydrogenation reaction and the porous carbon shell improved the transferring of furfural and electronic. [ABSTRACT FROM AUTHOR]

• RuSnB/CeO 2 efficiently catalyzes cinnamaldehyde hydrogenation to cinnamyl alcohol in water. • Structural and electronic modification by Sn and B species enhance catalytic property of Ru sites. • Water-involved hydrogen-exchange route co-exists with H 2 -dissociation-hydrogenation. • H 2 -dissociation is not rate-limiting step whereas facile H 2 O-activation accelerates reaction. The CeO 2 -supported ternary RuSnB catalysts were synthesized by incipient wetness impregnation procedures and applied in hydrogenation of cinnamaldehyde in pure water as the solvent. A synergy effect between Ru-based catalysts and water molecules has afforded the efficiently selective transformation of cinnamaldehyde to cinnamyl alcohol with the satisfactory conversion and selectivity. Structural characterization results suggested the incorporation of Ru sites into the SnO x matrix and the electronic interaction between Ru and B additives in RuSnB/CeO 2 catalyst. The isotopic exchange studies have demonstrated that both dissociative activation of H 2 and H 2 O (deuterated D 2 and D 2 O) were apparently affected by the status of Ru sites. Furthermore, the kinetics tests in D 2 O solvent have also revealed the co-existence of water-involved hydrogen-exchange route with the direct hydrogenation route using dissociative H 2 during the hydrogenation reaction. The optimal Ru 2 Sn 1 B 1 /CeO 2 catalyst could afford the best H 2 O-activation capability and thus accelerate the reaction rate in the H 2 O-involved hydrogenation. [ABSTRACT FROM AUTHOR]