Excellent catalytic properties over nanocomposite catalysts for selective hydrogenation of halonitrobenzenes

Metal Nanoclusters Synthesized in Alkaline Ethylene Glycol: Mechanism and Application

The "unprotected" metal and alloy nanoclusters (UMCs) prepared by the alkaline ethylene glycol method, which are stabilized with simple ions and solvent molecules, have the advantages of a small particle size, a narrow size distribution, good stability, highly efficient preparation, easy separation, surface modification and transfer between different phases. They can be composited with diverse materials to prepare catalytic systems with controllable structures, providing an effective means of studying the different factors' effects on the catalytic properties separately. UMCs have been widely used in the development of high-performance catalysts for a variety of functional systems. This paper will review the research progress on the formation mechanism of the unprotected metal nanoclusters, exploring the structure-function relationship of metal nanocluster catalysts and the preparation of excellent metal catalysts using the unprotected metal nanoclusters as building blocks or starting materials. A principle of the influence of carriers, ligands and modifiers in metal nanocluster catalysts on the catalytic properties is proposed.

Platinum clusters anchored on sulfur-doped ordered mesoporous carbon for chemoselective hydrogenation of halogenated nitroarenes

Chemoselective hydrogenation of unsaturated organic compounds is a significant research topic in the catalysis field. Herein, a sulfur-doped ordered mesoporous carbon (SMC) material was prepared to anchor ultrafine platinum (Pt) clusters for the chemoselective hydrogenation of halogenated nitroarenes. The confinement effect of the ordered pores and the strong metal-support interaction caused by Pt clusters and sulfur atoms, efficiently suppress the aggregation and regulate the electronic states of the ultrafine Pt clusters. Thus, the hydrogenation of parachloronitrobenzene (p-CNB) shows high selectivity catalyzed by the ultrafine Pt clusters with electron-rich states. Meanwhile, the catalytic performance of the hydrogenation reaction catalyzed by Pt/SMC is capable of being maintained after at least 5 cycles, and the catalytic universality can also be applied to different halogenated nitroarenes hydrogenation. Therefore, this study may promote the research into the construction of noble metal-based catalysts for chemoselective hydrogenation reactions in green and sustainable chemical processes.

A highly CO-tolerant atomically dispersed Pt catalyst for chemoselective hydrogenation

The hydrogenation activity of noble metal, especially platinum (Pt), catalysts can be easily inhibited by the presence of a trace amount of carbon monoxide (CO) in the reaction feeds. Developing CO-resistant hydrogenation catalysts with both high activity and selectivity is of great economic interest for industry as it allows the use of cheap crude hydrogen and avoids costly product separation. Here we show that atomically dispersed Pt over α-molybdenum carbide (α-MoC) constitutes a highly CO-resistant catalyst for the chemoselective hydrogenation of nitrobenzene derivatives. The Pt₁/α-MoC catalyst shows promising activity in the presence of 5,000 ppm CO, and has a strong chemospecificity towards the hydrogenation of nitro groups. With the assistance of water, high hydrogenation activity can also be achieved using CO and water as a hydrogen source, without sacrificing selectivity and stability. The weakened CO binding over the electron-deficient Pt single atom and a new reaction pathway for nitro group hydrogenation confer high CO resistivity and chemoselectivity on the catalyst.

Selectivity Control on Hydrogenation of Substituted Nitroarenes through End-On Adsorption of Reactants in Zeolite-Encapsulated Platinum Nanoparticles

Platinum nanoparticles encapsulated into zeolite Y (Pt@Y catalyst) exhibit excellent catalytic selectivity in the hydrogenation of substituted nitroarenes to form the corresponding aromatic amines, even after complete conversion. With the hydrogenation of p-chloronitrobenzene as a model, the role of zeolite encapsulation toward perfect selectivity can be attributed to constraint of the substrate adsorbed on the platinum surface in an end-on conformation. This conformation results in the activation of only one adsorbed group, with little influence on the other one in the molecule. Owing to a much lower apparent activation energy of Pt@Y for the hydrogenation of a separately adsorbed nitro group than that of the adsorbed chloro group, the Pt@Y catalyst can prevent hydrodechlorination of p-chloronitrobenzene under mild conditions. Moreover, such a conformation results in a reduced adsorption energy of target p-chloroaniline on the platinum surface; thus suppressing the reactivity of hydrodechlorination of p-chloroaniline to circumvent further C-Cl bond breakage.

Highly efficient Fischer–Tropsch synthesis over an alumina-supported ruthenium catalyst

A highly active catalyst for Fischer–Tropsch synthesis at 423 K was prepared, on which the adsorbed CO dissociated at 303 K.

Spontaneously grown Ni(OH)2on iron oxide nanoparticles with enhanced energy storage performance for electrodes of asymmetric supercapacitors

Spontaneously grown Ni(OH)₂over iron oxides for enhanced electrochemical energy storage performance in asymmetric supercapacitors.

Highly efficient and durable platinum nanocatalysts stabilized by thiol-terminated poly(N-isopropyl acrylomide) for selective hydrogenation of halonitrobenzene to haloaniline

Thermosensitive polymer PNIPAM-SH stabilized Pt nanocatalyst was firstly applied in the selective hydrogenation of halonitrobenzenes to haloanilines and exhibited notably high and steady selectivity as well as high durability.

A phosphorus–carbon framework over activated carbon supported palladium nanoparticles for the chemoselective hydrogenation of para-chloronitrobenzene

A novel Pd–P–C framework structure was fabricated. Pd with electron-rich properties exhibits superior selectivity up to 99.9% for the hydrogenation of p-CNB to p-CAN.

Ru nanoparticles supported on nitrogen-doped porous carbon derived from ZIF-8 as an efficient catalyst for the selective hydrogenation of p-chloronitrobenzene and p-bromonitrobenzene

Ruthenium (Ru) nanoparticles (NPs) are supported on nitrogen-doped porous carbon (NPC) derived from metal-organic-framework (MOF) ZIF-8 for the first time. NPC is prepared by the direct carbonization of ZIF-8 crystals, which not only retains the original morphology of ZIF-8 but also provides a high surface area and stable chemical-physical properties. Ru NPs were supported by different methods. Four types of Ru-based catalysts are tested in the selective hydrogenation of p-chloronitrobenzene (p-CNB) and p-bromonitrobenzene (p-BNB) to haloanilines. Different catalytic activities and selectivities are obtained through these catalysts. After the screening of the catalysts and reaction conditions, high conversion and selectivity were obtained. The hydrogen pressure is limited to 1.5 MPa, which is much lower than most previous reports, and the dehalogenation reaction is restricted to a very low level. Furthermore, the dehalogenation properties of the Ru/NPC catalysts are also studied.

Pt–FeOx/SiO2catalysts prepared by galvanic displacement show high selectivity for cinnamyl alcohol production in the chemoselective hydrogenation of cinnamaldehyde

Intimately interacting Pt–FeO_xentities preparedviagalvanic displacement are highly selective for the chemoselective hydrogenation of the CO bond in cinnamaldehyde.

Selective electrocatalytic hydrogenation using palladium nanoparticles electrochemically formed in layer-by-layer multilayer films

Sequential adsorption of PdCl₄²⁻ within weak polyelectrolyte layer-by-layer (LbL) self-assembled multilayer films with further electrochemical reduction to yield Pd⁰ nanoparticles (Pd-NPs) and later heat treatment.

Nano Cu-catalyzed efficient and selective reduction of nitroarenes under combined microwave and ultrasound irradiation

In situ preparation of copper nanoparticles from a copper acetate precursor and its application as an efficient catalyst for the selective reduction of aromatic nitro compounds with hydrazine hydrate under combined microwave and ultrasound irradiation were described in detail. The results reveal the synergetic effect of microwave and ultrasound on the synthesis of copper nanoparticles, and formation of various amino derivatives.

Magnetically recoverable nanoflake-shaped iron oxide/Pt heterogeneous catalysts and their excellent catalytic performance in the hydrogenation reaction

In this study, a kind of unique Fe2O3/Pt hybrid consisting of uniform platinum nanoparticles deposited on a nanoflake-shaped Fe2O3 support was prepared by using a solvothermal reaction followed by a heat-induced reduction process. The prepared Fe2O3 sample displays well-defined nanoflake-like morphology; remarkably, there are many specific cavities on its surface. In addition, uniform Pt nanoparticles with narrow size distribution were deposited onto the surface of the preformed flake-like Fe2O3 support to form the Fe2O3/Pt hybrid via a facile heat-induced reduction reaction. Thus, the prepared Fe2O3/Pt hybrid can serve as heterogeneous catalyst over the hydrogenation reaction. Results demonstrated that the specific Fe2O3/Pt heterogeneous catalyst exhibits good catalytic performances, including high conversion, specific selectivity, and excellent recycling durability, over hydrogenation reactions for different substrates. Furthermore, the prepared Fe2O3/Pt heterogeneous catalyst could be easily separated from the product mixture by using a magnet and could be recycled for 10 cycles without catalytic activity loss. In a word, the present synthetic approach is facile, scalable, and reproducible, which can be easily facilitated to prepare other types of noble metals/metal oxide composite systems.

A recyclable nanoparticle-supported rhodium catalyst for hydrogenation reactions

Catalytic hydrogenation under mild conditions of olefins, unsaturated aldeydes and ketones, nitriles and nitroarenes was investigated, using a supported rhodium complex obtained by copolymerization of Rh(cod)(aaema) [cod: 1,5-cyclooctadiene, aaema^–: deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with acrylamides. In particular, the hydrogenation reaction of halonitroarenes was carried out under 20 bar hydrogen pressure with ethanol as solvent at room temperature, in order to minimize hydro-dehalogenation. The yields in haloanilines ranged from 85% (bromoaniline) to 98% (chloroaniline).