Hydrogenation Of Nitroaromatics Research Articles

Green synthesis of gold nanoparticles by a newly isolated strain Trichosporon montevideense for catalytic hydrogenation of nitroaromatics.

To investigate green synthesis of gold nanoparticles (AuNPs) by Trichosporon montevideense, and to study their reduction of nitroaromatics. AuNPs had a characteristic absorption maximum at 535nm. Scanning electron microscopy images revealed that the biosynthesized nanoparticles were attached on the cell surface. X-ray diffraction analysis indicated that the particles formed as face-centered cubic (111)-oriented crystals. The average size of AuNPs decreased from 53 to 12nm with increasing biomass concentration. The catalytic reduction of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-nitrophenylamine and m-nitrophenylamine (0.1mM) by NaBH4 had reaction rate constants of 0.32, 0.44, 0.09, 0.24 and 0.39min(-1) with addition of 1.45×10(-2) mM AuNPs. An eco-friendly approach for synthesis of AuNPs by T. montevideense is reported for the first time. The biogenic AuNPs could serve as efficient catalysts for hydrogenation of various nitroaromatics.

High-Yield Production of Boron Nitride Nanosheets and Its Uses as a Catalyst Support for Hydrogenation of Nitroaromatics.

Single- or few-layered h-BN nanosheets (BNNSs) are analogous to graphene and possess unique properties. However, their technological applications were severely hindered by the low production efficiency of BNNSs. We reported here a study in which BNNSs were efficiently produced by exfoliating bulk h-BN powder in thionyl chloride without using any dispersion agents. The BNNSs yield was as high as 20%, and it could be doubled through the second round of exfoliation of the h-BN precipitate. Microscopic results revealed that the BNNSs generally consisted of 3-20 layers. Pd nanoparticles were successfully immobilized and uniformly distributed on BNNS surfaces through the deposition-precipitation method. The resultant Pd-BNNS catalyst exhibited high catalytic activity and recyclability for the hydrogenation of nitro aromatics, demonstrating that BNNSs served as a promising platform to fabricate heterogeneous catalysts.

Interfacial electronic effects control the reaction selectivity of platinum catalysts.

Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

Pyrite nanoparticles: an Earth-abundant mineral catalyst for activation of molecular hydrogen and hydrogenation of nitroaromatics

Pyrite (FeS2) nanoparticles, a kind of Earth-abundant mineral, can efficiently activate molecular hydrogen under mild conditions.

A Fe3O4@Nico@Ag nanocatalyst for the hydrogenation of nitroaromatics

We report the fabrication and characterization of a magnetically recyclable Fe3O4@Nico@Ag catalyst for reduction reactions in the liquid phase. Fe3O4 is a magnetic core and nicotinic acid was used as the linker for Ag. The characterization was done with X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometry (VSM), and ultraviolet-visible spectroscopy. VSM measurements proved the superparamagnetic property of the catalyst.

Fe3O4@Hpipe-4@Cu Nanocatalyst for Hydrogenation of Nitro-Aromatics and Azo Dyes

In this study, a facile method is described for the Cu deposited Piperidine-4-carboxylic acid (Hpipe-4) coated magnetite (Fe3O4) nanoparticles. For which, Fe3O4 was used as magnetic core, Hpipe-4 as linker and active copper nanoparticles as the catalyst. For the reduction of Cu 2? to Cu 0 was accomplished by NaBH4. The phase and morphology of the as-prepared product is characterized by means of X-ray powder diffractometry, energy dispersive spectrometry, Scanning electron microscopy. Magnetic and catalytic properties of the product were followed by vi- brating sample magnetometer and UV-Vis spectrophome- ter respectively. Experiments showed that the as-prepared Fe3O4@Hpipe-4@Cu nanocatalyst owned strong catalytic activity for the reduction of some aromatic nitro-com- pounds and organic azo dyes and also emphasizes the ef- fect of copper nanoparticles on the degradation of rate of hazardous compounds by NaBH4 .F e 3O4@Hpipe-4@Cu nanocatalyst show great promise for the treatment of in- dustrial dye pollutants hence environmental protection. Graphical Abstract

A study on the selective hydrogenation of nitroaromatics to N-arylhydroxylamines using a supported Pt nanoparticle catalyst

Selective hydrogenation of nitroarenes to N-arylhydroxylamines at high rates over supported Pt-NPs.

Photocatalytic Hydrogenation of Nitroaromatics to Anilines on Silica-Supported Iron Oxides with Hydrazine Monohydrate as a Reductant

Photocatalytic Hydrogenation of Nitroaromatics to Anilines on Silica-Supported Iron Oxides with Hydrazine Monohydrate as a Reductant

ChemInform Abstract: Selective Hydrogenation of Nitroaromatics by Colloidal Iridium Nanoparticles.

Poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized iridium nanoparticles (Ir NPs) showed high chemoselectivity for hydrogenation of nitroaromatics having –CHO, >C=O, –CN, and –Cl functional groups to aff...

ChemInform Abstract: The Hydrogenation of Nitroarenes Mediated by Platinum Nanoparticles: An Overview

AbstractReview: 74 refs.

ChemInform Abstract: Platinum N‐Heterocyclic Carbene Nanoparticles as New and Effective Catalysts for the Selective Hydrogenation of Nitroaromatics.

AbstractFunctional groups such as hydroxy, benzyloxy, carbonyl, cyano, and halogens are tolerated under the present reaction conditions.

Gold catalysts for the synthesis of aromatic azocompounds from nitroaromatics in one step

One-step selective hydrogenation of nitroaromatics to obtain symmetric azocompounds with high yields has been performed with a gold supported on cerium oxide catalysts. Au/TiO2 and Au/CeO2 catalysts direct the reaction by two different pathways and with different selectivities. In situ FTIR studies reveal that the surface concentration of the intermediate nitrosobenzene is decisive in directing the reaction trough the different reaction pathways. In this way, while on Au/TiO2 a fast hydrogenation of the nitrosobenzene intermediate leads to a low surface concentration of the nitrosocompound, on Au/CeO2 nitrosobenzene is more stabilized on the catalyst surface leading to a lower hydrogenation and a higher coupling rate, resulting in high selectivities to azobenzene. On Au/CeO2, the relative weak adsorption of the azo with respect to the azoxycompound on the catalyst surface avoids the consecutive hydrogenation of azocompounds to the corresponding anilines until all the azoxy has been consumed. Asymmetric azobenzenes have also been obtained with very high yields on TiO2, through the Mills reaction.

Synthesis of In2S3–CNT nanocomposites for selective reduction under visible light

In2S3–carbon nanotube (In2S3–CNT) nanocomposites have been prepared via a facile refluxing wet chemistry process. The as-synthesized In2S3–CNT nanocomposites can be used as selective and active visible-light-driven photocatalysts toward hydrogenation of nitroaromatics to amines in water. Photoirradiation (λ > 420 nm) of In2S3–CNT photocatalysts suspended in water containing nitroaromatics produces the corresponding amines with high yields. The control experiments reveal that an inert atmosphere and the addition of a hole scavenger are both indispensable for the visible-light-driven photocatalytic hydrogenation of nitroaromatics over In2S3–CNT. In comparison with blank In2S3, the obviously enhanced photocatalytic performance of the In2S3–CNT photocatalyst is mainly ascribed to the unique physicochemical properties of CNTs, which enhances the adsorptivity of the substrate and performs as an electron reservoir to trap electrons, thereby hindering the recombination of photogenerated electron–hole pairs. It is hoped that the current work on the facile synthesis of semiconductor In2S3–CNT nanocomposites can broaden the applications of semiconductor-carbon based composite photocatalysts in the field of photocatalytic selective organic transformations under mild conditions.

Platinum N‐Heterocyclic Carbene Nanoparticles as New and Effective Catalysts for the Selective Hydrogenation of Nitroaromatics

AbstractIn this communication, we report the first synthesis of Pt NPs stabilized with NHC ligands and their investigation as catalysts in the chemoselective hydrogenation of nitroarenes. The results in catalysis show that by a proper choice of the NHC stabilizer and the adjustment of the NHC/metal ratio, these NHC‐capped Pt NPs exhibit high levels of activity and selectivity in the hydrogenation reactions. In particular, Pt NPs stabilized with 2 equiv. of IPr carbene (PtIPr0.2) catalyze the chemoselective reduction of a series of functionalized nitroarenes under mild conditions (1 bar H2, 30 °C). This catalyst tolerates the presence of a range of functional groups including hydroxyl, benzyloxy, carbonyl and olefinic moeities as well as halogens.

Effects of Pd on Catalysis by Au: CO Adsorption, CO Oxidation, and Cyclohexene Hydrogenation by Supported Au and Pd–Au Catalysts

Incorporating small amounts of Pd into supported Au catalysts has been shown to have beneficial effects on selective hydrogenation reactions, particularly 1,3-butadiene hydrogenation and the hydrogenation of nitroaromatics, especially p-chloronitrobenzene. Appropriate Pd incorporation enhances hydrogenation activity while maintaining the desirable high selectivity of supported Au catalysts. To better understand this phenomenon, a series of alumina- and titania-supported Au and dilute Pd–Au catalysts were prepared via urea deposition–precipitation. The catalysts were studied with infrared spectroscopy of CO adsorption, CO oxidation catalysis, and cyclohexene hydrogenation catalysis with the goal of understanding how Pd affects the catalytic properties of Au. CO adsorption experiments indicated a substantial amount of surface Pd when the catalyst was under CO. Adsorption experiments at various CO pressures were used to determine CO coverage; application of the Temkin adsorbate interaction model allowed for the determination of adsorption enthalpy metrics for CO adsorption on Au. These experiments showed that Pd induces an electronic effect on Au, affecting both the nascent adsorption enthalpy (ΔH0) and the change in enthalpy with increasing coverage. This electronic modification had little effect on CO oxidation catalysis. Michaelis–Menten kinetics parameters showed essentially the same oxygen reactivity on all the catalysts; the primary differences were in the number of active sites. The bimetallic catalysts were poor cyclohexene hydrogenation catalysts, indicating that there is relatively little exposed Pd when the catalyst is under hydrogen. The results, which are discussed in the context of the literature, indicate that a combination of surface composition and Pd-induced electronic effects on Au appear to increase hydrogen chemisorption and hydrogenation activity while largely maintaining the selectivities associated with catalysis by Au.

Rutile Crystallites Isolated from Degussa (Evonik) P25 TiO2: Highly Efficient Photocatalyst for Chemoselective Hydrogenation of Nitroaromatics

We report that the rutile crystallites, isolated from Degussa (Evonik) P25 TiO2 by a hydrofluoric acid treatment, behave as a highly efficient photocatalyst for hydrogenation of nitroaromatics. Photoirradiation (λ >300 nm) of the isolated rutile particles with alcohol as a hydrogen source successfully promotes chemoselective hydrogenation of nitroaromatics to anilines, with an activity higher than that of commercially available rutile TiO2. The high activity of the isolated rutile particles is due to the specific distribution of structural defects (oxygen vacancy sites) on the particles. These particles contain a relatively small number of inner defects behaving as recombination centers for photoformed electron (e–) and positive hole (h+) pairs, and a relatively large number of surface defects behaving as reduction sites for nitroaromatics. Photoexcitation of the isolated particles therefore promotes efficient charge separation between e– and h+, and facilitates rapid reduction of nitroaromatics adsorbed ...

Selective Hydrogenation of Nitroaromatics by Colloidal Iridium Nanoparticles

Abstract Poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized iridium nanoparticles (Ir NPs) showed high chemoselectivity for hydrogenation of nitroaromatics having –CHO, >C=O, –CN, and –Cl functional groups to afford the corresponding aniline compounds under atmospheric hydrogen at room temperature in aqueous–organic biphasic medium.

ChemInform Abstract: In situ Synthesized Pd Nanoparticles Supported on B‐MCM‐41: An Efficient Catalyst for Hydrogenation of Nitroaromatics in Supercritical Carbon Dioxide.

AbstractIn the reaction of the substituted aromatic nitro‐compounds the order of reactivity is ortho < meta < para.

ChemInform Abstract: The Development of Gold Catalysts for Use in Hydrogenation Reactions

AbstractReview: 333 refs.

Selective hydrogenation of nitroaromatics by ceria nanorods

Ceria (CeO2) nanorods with well-defined surface planes can be synthesized and utilized for the hydrogenation of nitroaromatics. The CeO2 nanorods containing a {110} plane can efficiently and selectively catalyse the hydrogenation of nitroaromatics with N2H4 as a reducing agent, while nano-ceria with a {100} or {111} plane shows poor performance for the reaction.