Hydrogenation Of Nitroaromatics Research Articles

Synthesis of layered double hydroxide-supported platinum nanocatalyst for highly efficient and selective hydrogenation of nitroaromatics

In this work, highly dispersed platinum nanoclusters (or single atoms) supported on layered double hydroxides (Pt/FeNi-LDHs, Pt/FeCo-LDHs, Pt/CoNi-LDHs) are synthesized. The as-prepared catalysts are used for the selective hydrogenation of nitroaromatics, the catalysts showed high activity, selectivity and stability. The as-synthesized catalysts are characterized by thermal-gravity (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), high resolution TEM (HRTEM), scanning TEM (STEM), STEM-EDS elemental analysis and inductively coupled plasma emission spectroscopy (ICP-OES) methods, which prove that the Pt species are highly dispersed on the support. Take p-nitroacetophenone reduction as an example, the 0.4%Pt/FeNi-LDHs catalyst also shows excellent catalytic performance (conversion = 98.2%, turnover frequency (TOF) = 1100.5 h−1) and high selectivity to p-aminoacetophenone (93.8%) among these as-prepared catalysts even at low temperature (60 °C). Its excellent performance is probably due to the uniform distribution of the platinum species and the interaction of Pt–FeNi-LDHs conducive to the selective hydrogenation of –NO2 groups.

Defective MNiFeO (M = Cu, Zn, Co, Mn) NRs derived from cation-exchanged Fe2Ni-MOFs for catalytic nitroarene hydrogenation

Catalytic hydrogenation reduction provides a potential route to detoxify nitro compounds. Spinel NiFe2O4 (NiFeO) serves as a natural abundance and low-cost catalyst but suffers from low catalytic activity due to poor redox nature and limited active sites. Herein, defective MNiFeO (M = Cu, Zn, Co, Mn) nanorods (NRs) were synthesized by pyrolysis of cation-exchanged Fe2Ni-MOFs. The introduction of M modified the electronic structure of NiFeO and thus accelerated the electron transfer and proton transport in the hydrogenation of nitro aromatics. CuNiFeO exhibited the highest catalytic activity with a turn frequency of 2.89 × 105h−1, giving 308- and 422-fold larger than that of NiFeO-Vo and NiFeO in the reduction of 4-nitrophenol (4-NP). CuNiFeO NRs also presented exceptional performances in the reduction of the other nitroarenes. The remarkable improvement in activity of mesoporous CuNiFeO may be attributed to its ternary composites, and increased oxygen vacancies. This work not only provides a simple route to constructing mesoporous MNiFeO NRs with oxygen vacancies, but also further discusses the effects of metal component and oxygen defects in the catalytic reduction of 4-NP.

Sulfur-doped graphitic carbon nitride decorated with starch, Fe3O4, and Ag nanoparticles: As efficient and magnetic recoverable nanocatalyst for hydrogenation of nitroaromatics in aqueous media

The reduction of nitroaromatics to corresponding anilines in the presence of the metal catalyst is an important and useful synthetic way in various applications. Silver nanoparticles have recently attained very interest as effective catalysts in the reduction of nitroaromatics by NaBH4. In this study, in situ sulfur-doped graphitic carbon nitride, exhibited as S-g-C3N4, was prepared, employing thiourea as an inexpensive precursor via a simple thermal method and applied as ideal catalyst support. Ag nanoparticles were stabilized on magnetic S-g-C3N4 modified with starch (S-g-C3N4/starch-Fe3O4-Ag). Several spectroscopic and microscopic methods approved the formation of S-g-C3N4/starch-Fe3O4-Ag nanocatalyst and the results have been well interpreted in this context. S-g-C3N4/starch-Fe3O4-Ag presented a good catalytic activity for the reduction of aromatic compounds bearing the nitro group when NaBH4 was employed as the reductive agent. The reduction efficiency of 4-nitroaniline in an aqueous medium was obtained at 99% in the presence of 5 mg of catalyst at 50 °C for 90 min. This prepared nanocatalyst's good catalytic potency and stability can be attributed to the synergistic interaction between very dispersed Ag nanoparticles and support.

Fast and selective reduction of nitroarenes under visible light with an earth-abundant plasmonic photocatalyst

Reduction of nitroaromatics to the corresponding amines is a key process in the fine and bulk chemicals industry to produce polymers, pharmaceuticals, agrochemicals and dyes. However, their effective and selective reduction requires high temperatures and pressurized hydrogen and involves noble metal-based catalysts. Here we report on an earth-abundant, plasmonic nano-photocatalyst, with an excellent reaction rate towards the selective hydrogenation of nitroaromatics. With solar light as the only energy input, the chalcopyrite catalyst operates through the combined action of hot holes and photothermal effects. Ultrafast laser transient absorption and light-induced electron paramagnetic resonance spectroscopies have unveiled the energy matching of the hot holes in the valence band of the catalyst with the frontier orbitals of the hydrogen and electron donor, via a transient coordination intermediate. Consequently, the reusable and sustainable copper-iron-sulfide (CuFeS2) catalyst delivers previously unattainable turnover frequencies, even in large-scale reactions, while the cost-normalized production rate stands an order of magnitude above the state of the art.

Non-contact biomimetic mechanism for selective hydrogenation of nitroaromatics on heterogeneous metal nanocatalysts

Non-contact biomimetic mechanism for selective hydrogenation of nitroaromatics on heterogeneous metal nanocatalysts

Dye-loaded metal-organic helical capsules applied to the combination of photocatalytic H2S splitting and nitroaromatic hydrogenation.

Two dye-loaded metal-organic capsules constructed with different spatial sizes and functional groups simulated the enzymatic substrate activation for hydrogenation of nitroarenes with the kinetics obeying the Michaelis-Menten mechanism.

Enhanced Tandem Hydrogenation of Nitroaromatics to Alicyclic Amines Under Mild Condition by Metal-Assisted Hydrogenation of Ru-Pd Dual Sites on C3n4 Nanosheets

Enhanced Tandem Hydrogenation of Nitroaromatics to Alicyclic Amines Under Mild Condition by Metal-Assisted Hydrogenation of Ru-Pd Dual Sites on C3n4 Nanosheets

Tetrametallic Copper Complex to Nanoscale Copper: Selective and Switchable Dehydrogenation-Hydrogenation under Light.

A discrete, photoactive, ultrafine copper nanocluster of fewer than hundreds of atoms with stimuli-responsive switchable redox-active states is highly desired to control two different antagonistic reactions. Herein, a mixed-valent tetrametallic copper complex (C-1) of N-O-N Schiff base ligand is disclosed, in which the five different Cu-Cu interactions were used to generate photoactive nanoscale copper [LCu0 n , S-1] through the reduction of coordinated imine to the amine of C-1. The presence of a ligand provides stability and helps to homogenize the material (S-1) in the organic solvent. The cluster showed stimuli (O2 /light)-responsive switching between its reduced (S-1) and oxidized [LCu0 n-m CuOm , S-2] states that allows it to serve as a highly and poorly active (bistate, relative rate >5-12 fold) catalyst for the dehydrogenation of alcohols to aldehydes and hydrogenation of nitroaromatics to amino aromatics under the light.

Highly dispersed Ru anchored on nanosheet N-doped carbon for efficient and chemoselective hydrogenation of nitroaromatics to aromatic amines under mild conditions

An efficient catalyst for chemoselective hydrogenation of nitroaromatics to produce aromatic amines under mild conditions is highly desirable. In this work, a series of N-doped carbon (NC-x) with high nitrogen contents were firstly synthesized by pyrolysis of 1-butyl-3-vinylimidazolium bromide-co-acrylonitrile with a template of g-C3N4. Furthermore, Ru/NC-x catalysts were successfully prepared by ultrasonic-assisted impregnation method. The catalysts were characterized by various methods in detail, e.g.X-ray diffraction, N2 physical adsorption-desorption, Transmission electron microscopy, Raman spectra, Scanning electron microscopy and H2 temperature programmed reduction. Characterization results revealed that N-doping on carbon contributed to the high dispersion of Ru nanoparticles and resulted in the forming of the electron-deficient of Ru species. Nanosheet Ru/NC-2 with high N-doping content of 28 wt% exhibited superior performance under room temperature, i.e., nitrobenzene conversion >99.0% and aniline selectivity 98.4%. Kinetic study indicated that the hydrogenation of nitrobenzene over Ru/NC-2 was the first-order kinetics with an intrinsic activation energy of 43.7 kJ/mol. Density functional theory calculation results suggested that Ru-Nx species, especially, Ru-pyrrolic-N facilitated nitrobenzene adsorption and H2 dissociation, resulting in enhanced catalytic performance. In addition, the excellent stability of Ru/NC-2 made it essentially reserved for 410 h in the fixed-bed reactor. Moreover, Ru/NC-2 exhibited superior performance for the hydrogenation of various nitroaromatics to corresponding aromatic amines. This work could provide meaningful guidance on designing effective and stable catalyst for chemoselective hydrogenation of nitroaromatics to aromatic amines under mild conditions.

Recent Advances in Hydrogenation Reactions Using Bimetallic Nanocatalysts: A Review

AbstractHydrogenation reactions have been studied for many decades now and have developed from reactions that appear simple to now being recognized for their many complexities. These reactions are generally catalyzed using monometallic and more recently, with bimetallic nanocatalysts. Hydrogenation plays a vital role in food, chemical, petrochemical, pharmaceuticals, and dye industries to name a few. The hydrogenated products derived from several biomass‐based compounds are potential fossil fuels. Such products when employed in daily life, can help conserve natural resources. While hydrogenation of alkynes and alkenes are among the simplest of hydrogenation reactions, the most extensive and elegant manifestation of this reaction is seen in polymerization. Polymers like polythene, polypropylene (plastic) have replaced materials like glass, stainless steel, etc., in making daily use items for the obvious advantages of the former. Purification of alkenes is achieved by partially hydrogenating the respective alkynes present in trace amounts. This serves as an important step in the polymerization process. The presence of nitro group on aromatic rings makes them carcinogenic in nature which harms living organisms. For a safe environment, the elimination or modification of this nitro group becomes imperative. The products of hydrogenation of nitroaromatics and amino aromatics form the basis of pharmaceuticals and dyestuffs. A plethora of bimetallic catalysts have been used to catalyze these hydrogenation reactions. These catalysts are evaluated based on their selectivity and efficiency. This review highlights the recent advancements in the field of hydrogenation of nitro compounds, carbonyl compounds, and unsaturated hydrocarbons catalyzed by bimetallic nanoparticles.

Binary CuO/TiO2 nanocomposites as high-performance catalysts for tandem hydrogenation of nitroaromatics

In situ hydrogenation of unsaturated compounds by released hydrogen from various hydrogen sources is a good strategy to achieve highly selective hydrogenation. In this work, inexpensive CuO/TiO 2 nanocomposites were systematically screened their performance for catalyzing dehydrogenation of ammonia borane (AB) and the tandem hydrogenation of some nitroaromatics. Those CuO/TiO 2 binary nanocomposites were found to maximize the hydrogen production from the catalytic hydrolysis of AB. Owing to a positive in-situ hydrogen activation, under mild conditions these CuO/TiO 2 nanocomposites exhibited highly excellent reactivities accompanying with better recyclability in the current one-pot hydrogenation. Notably, a selected CuO (0.5) /TiO 2(0.5) nanocomposites displayed high activity and regioselectivity (up to100% yield of aim product) as well as increased ability of inhibiting the dehalogenation reaction, especially for 4-bromonitrobenzene or 4-iodonitrobenzene (up to 71.65% yield for 4-bromoaniline or 68.02% yield of 4-iodoaniline). Moreover, that CuO (0.5) /TiO 2(0.5) nanocomposites from a co-precipitation method displayed relatively better recyclability against those two control samples obtained from a stepwise preparation process. Owing to positive in-situ hydrogen activation mechanism, CuO/TiO 2 binary nanocomposites from co-precipitation method display highly excellent reactivity, regioselectivity, and better recyclability for the tandem hydrogenation of aromatic nitro-compounds under highly mild conditions. • Binary CuO/TiO2 nanocomposites exhibited attractive reactivity toward the tandem hydrogenation of nitro-compounds. • Control experiments powerfully confirm a positive in-situ hydrogen activation benefitting the efficient tandem hydrogenation. • Distinguishable catalytic performances were observed for those catalysts coming from different preparation methods.

Facile fabrication of graphene encapsulating 3d transition metal nanoparticles as highly active and anti-poisoning catalysts for selective hydrogenation of nitroaromatics

Graphene encapsulating 3d transition metal nanoparticles (Ni, Co, Fe@G) are successfully fabricated through pyrolysis of complexes which are simply prepared via “acid-base reactions” between metal hydroxides and carboxylic acid such as citric acid. In particular, the Ni@G catalyst exhibits outstanding catalytic activity and selectivity (>99%) toward the reduction of various nitroaromatics under mild conditions (1 MPa H2, 60 °C), even in the presence of poisons (CO and thiophene etc.). This “acid-base reactions” based method provides a facile and scalable approach to prepare graphene encapsulating 3d transition metals with wide ranges of applications.

Zinc modification of Ni-Ti as efficient NixZnyTi1 catalysts with both geometric and electronic improvements for hydrogenation of nitroaromatics

Zinc modification of Ni-Ti as efficient NixZnyTi1 catalysts with both geometric and electronic improvements for hydrogenation of nitroaromatics

Fabrication of Pd/Mg2 P2 O7 via a Struvite-Template Way from Wastewater and Application as Chemoselective Catalyst in Hydrogenation of Nitroarenes.

A highly efficient heterogeneous catalyst Pd/Mg2 P2 O7 was fabricated by combining palladium nanoparticles (PdNPs) and mesoporous Mg2 P2 O7 fibers/rods. Mg2 P2 O7 fibers with ultra-high specific surface area were prepared from struvite as templates, which were synthesized from waste water containing N- and P-containing pollutants. This strategy provided a novel pathway for developing advanced catalysts from eutrophication-polluted water. The composite Pd/Mg2 P2 O7 showed brilliant performance in selective hydrogenation of nitro aromatics to give anilines. As an example of nitrobenzene hydrogenation, the conversion to aniline and selectivity were found to reach almost 100 % at a temperature of T=90 °C and under a pressure of P =2.0 MPa. The superior performance was found to originate from PdNPs, which were boosted by electron transfer afforded by the nanofiber Mg2 P2 O7 supports. The favorable adsorption of withdrawing groups (-NO2 ) was realized by synergistic effects between Pd and oxygen vacancies provided by pyrolysis of struvite. The catalyst remained stable after cycles of reuse with little degradation in catalytic performance.

Ultra-high loading single CoN3 sites in N-doped graphene-like carbon for efficient transfer hydrogenation of nitroaromatics

Atomically dispersed non-noble metal single-site catalysts (SSCs) provide a promising approach to meet the catalytic requirements that traditional nanoparticles cannot accomplish. However, they often suffer from formidable challenges of cumbersome route, unmanageable loading, inevitable burial of active site and insufficient stability. Herein, we present a facile and hard template-assisted spatial confinement strategy to prepare Co SSCs embedded in N-doped graphene-like carbon (NG) with ultra-high loading of 10.26 wt%, which is close to the parent CoPc (10.31 wt%). Furthermore, the microstructure, surface area and Co loading in the titled catalysts can be easily manipulated via altering the synthesis parameters. The optimized Co SSCs@NG-800-50 catalyst shows excellent transfer hydrogenation of nitrobenzene with > 99% conversion and 96.3% aniline selectivity as well as good universality for various nitroaromatics in the presence of HCOOH. DFT calculations in combination with elaborate experiments unveil that the active H is firstly generated by the dissociation of C-H bond rather than the recognized O-H bond in HCOOH, then it is used for the hydrogenation of nitroaromatics on CoN3 site in Co SSCs@NG-800-50 catalyst, revealing the reaction mechanism of the tandem catalysis. This report paves a novel route to design and construct efficient and high-loading non-noble metal SSCs.

Preparation of thermal stable supported metal (Cu, Au, Pd) nanoparticles via cross-linking cellulose gel confinement strategy

Hydrogel is low-cost porous material that has been used as effective support for confining metal nanoparticles due to its interconnected three-dimensional (3D) networks. Cellulose gel with covalently crosslinking has good thermal stability and can be used as support to stabilize metal nanoparticles in the high temperature environment. In this work, (Cu, Pd, Au) nanoparticles were immobilized on covalently crosslinked cellulose gel via adsorption and in situ reduction, followed by pyrolysis to obtain carbon-supported metal nanoparticles. Typically, the Cu nanoparticles were highly dispersed in the gels due to the interconnected networks and functional groups that restricted the aggregation of metal nanoparticles and improved the stability of the gel framework during pyrolysis. The results were confirmed by XRD, TEM, XPS, and FT-IR analyses. Furthermore, the Cu NPs exhibited good catalytic activity and selectivity for the hydrogenation of nitroaromatics with a TOF of 6656 h −1 , which was comparable to previously reported Pd catalysts. The catalyst remained its activity after 10 recycles, demonstrating the high stability and activity of the Cu NPs prepared by this method. This work provides a green synthetic pathway for the construction of size-controlled metal nanoparticles immobilized on a carbon support.

Plasmon-Mediated Nitrobenzene Hydrogenation with Formate as the Hydrogen Donor Studied at a Single-Particle Level

Hydrogenation of nitroaromatics is typically performed under harsh reaction conditions, which would bring safety issues and energy waste. The key for the hydrogenation reaction is to finely control the product selectivity under mild conditions. Herein, the anisotropic Pd–Au nanorods (NRs) exhibited efficient plasmon-enhanced selective hydrogenation of nitrobenzene to aniline with formate as the hydrogen donor. Under visible-light irradiation, both conversion and selectivity for nitrobenzene hydrogenation can reach nearly 100%. Plasmon-induced interaction between formic acid (FA), nitrobenzene, and plasmonic nanostructures was explored by single-particle photoluminescence (PL) measurement in situ. The complete quenching phenomenon of localized surface plasmon resonance PL for single Pd–Au NR was observed when immersed in FA. In addition, light-induced adsorption enhancement of nitrobenzene was discovered, which is vital for the plasmon-enhanced catalysis. This work provides direct evidence for the carrier transfer from Au–Pd NRs to FA via single-particle PL measurement and will give guidance to the rational design of hybrid plasmonic catalysts to promote eco-friendly organic conversion.

Size Effect in Hydrogenation of Nitroaromatics Using Support-Immobilized Atomically Precise Gold Clusters

Three types of phosphine-stabilized gold clusters, [Au19(PhC≡C)9(Hdppa)3](SbF6), [Au20(PP3)4](Cl)4, and [Au22(Dppee)7](Cl)2, were chemically synthesized and deposited onto hydroxyapatite, TiO2 and ...

Simultaneous oxidative and reductive reactions in one system by atomic design

Single-atom catalysts often exhibit unexpected catalytic activity for many important chemical and biological reactions with respect to their bulk counterparts, and have been recognized as potential substitutes for natural enzymes. Here we report a biomimetic composite, yolk–shell Pd1@Fe1, that features two compatible single-atom systems with atomically dispersed Fe1 sites in a N-doped carbon shell and Pd1 sites in a yolk derived from a metal–organic framework. Directly utilizing the O2 and H2 sources generated on-site from the electrocatalytic overall water splitting, the as-synthesized yolk–shell Pd1@Fe1 could simultaneously catalyse nitroaromatic hydrogenation and alkene epoxidation reactions and lead to a cascade synthesis of amino alcohols. Our findings provide a versatile strategy to integrate different single metal sites within one system to allow the continuous and easy synthesis of complex compounds for various challenging reactions. Single-atom catalysts can exhibit improved catalytic performance with respect to their bulk counterparts. Now, the authors introduce a yolk@shell catalyst with spatially separated Pd and Fe single sites that simultaneously catalyse nitroaromatic hydrogenation and alkene epoxidation reactions, leading to a cascade synthesis of amino alcohols.

Silver Nanoparticles Immobilized Covalent Organic Microspheres for Hydrogenation of Nitroaromatics with Intriguing Catalytic Activity

Herein, we present a scalable and economic synthesis of covalent organic microspheres, a highly cross-linked microspherical polymer, through a single step process. The as-synthesized imine-linked m...