Hydrogenation Of Nitroaromatics Research Articles

Foam Ti Supported Pd Catalysts for the Selective Hydrogenation of Nitroaromatics.

The selective hydrogenation of nitroaromatics plays an essential role in the chemical industry for the synthesis of anilines and their derivatives, which are known as crucial fine chemicals and pharmaceuticals. In this study, we demonstrate the preparation of Pd/Ti monolith catalyst containing well-isolated metallic Pd sites on Ti substrate through a simple impregnation method, showing remarkable catalytic properties in the selective hydrogenation of nitroaromatics containing various functional groups. Kinetic analyses reveal an apparent activation energy of 61 kJ/mol and the kinetic isotope effect (KH2/KD2) of ~1.7 in the hydrogenation of 3-chloronitrobenzene over Pd/Ti-200 ppm catalyst, indicating the facile dissociation of dihydrogen and the subsequent efficient hydrogenation. The Pd/Ti-200 ppm catalyst also demonstrates good stability and recyclability, maintaining its performance over multiple cycles. This simple but innovative approach not only enhances the efficiency of Pd catalysts in the selective hydrogenation of nitroaromatics but also offers significant potential for industrial applications in aniline production.

Ag nanoparticles on arginine-cyanoguanidine functionalized magnetic g-C3N4: A catalyst for nitroaromatic hydrogenation and regioselective click reactions

This study describes the development of a novel hybrid nanocatalyst that was obtained by doping magnetic g-C3N4 with Ag nanoparticles and modifying it with arginine and cyanoguanidine (Ag@Fe3O4-g-C3N4-Arg-CG). Comprehensive characterization of the nanocatalyst using techniques such as FTIR, XRD, SEM, and TGA confirmed its structural and morphological properties. The catalytic efficiency of the synthesized nanostructure was evaluated in two key reactions: the reduction of nitroaromatic compounds and a click reaction for 1,2,3-triazole synthesis. The results demonstrate that Ag@Fe3O4-g-C3N4-Arg-CG effectively reduced various nitroaromatic compounds to substituted anilines at room temperature using NaBH4 as the reducing agent. Nitrobenzene reduction did not proceed in aprotic solvents such as acetonitrile, CH2Cl2, and dimethylformamide, whereas it exhibited a high reaction yield in protic solvents such as ethanol and water. The highest yield (100 %) was observed in water at 50 °C using H2O solvent. Additionally, the nanohybrid exhibited significant potential for “green” click chemistry by efficiently synthesizing 1,2,3-triazoles under mild conditions, with low catalyst loading. Its magnetic properties facilitated easy recovery, and the catalyst maintained high activity over six cycles, making it suitable for sustainable applications in organic transformations.

Thermally-stable single-site Pd on CeO2 catalyst for selective amination of phenols to aromatic amines without external hydrogen.

Developing a new route to produce aromatic amines as key chemicals from renewable phenols is a benign alternative to current fossil-based routes like nitroaromatic hydrogenation, but is challenging because of the high dissociation energy of the Ar-OH bond and difficulty in controlling side reactions. Herein, an aerosolizing-pyrolysis strategy was developed to prepare high-density single-site cationic Pd species immobilized on CeO2 (Pd1/CeO2) with excellent sintering resistance. The obtained Pd1/CeO2 catalysts achieved remarkable selectivity of important aromatic amines (yield up to 76.2%) in the phenols amination with amines without external hydrogen sources, while Pd nano-catalysts mainly afforded phenyl-ring-saturation products. The excellent catalytic properties of the Pd1/CeO2 are closely related to high-loading Pd single-site catalysts with abundant surface defect sites and suitable acid-base properties. This report provides a sustainable route for producing aromatic amines from renewable feedstocks.

Thermally‐stable single‐site Pd on CeO2 catalyst for selective amination of phenols to aromatic amines without external hydrogen

Developing a new route to produce aromatic amines as key chemicals from renewable phenols is a benign alternative to current fossil‐based routes like nitroaromatic hydrogenation, but is challenging because of the high dissociation energy of the Ar‐OH bond and difficulty in controlling side reactions. Herein, an aerosolizing‐pyrolysis strategy was developed to prepare high‐density single‐site cationic Pd species immobilized on CeO2 (Pd1/CeO2) with excellent sintering resistance. The obtained Pd1/CeO2 catalysts achieved remarkable selectivity of important aromatic amines (yield up to 76.2%) in the phenols amination with amines without external hydrogen sources, while Pd nano‐catalysts mainly afforded phenyl‐ring‐saturation products. The excellent catalytic properties of the Pd1/CeO2 are closely related to high‐loading Pd single‐site catalysts with abundant surface defect sites and suitable acid‐base properties. This report provides a sustainable route for producing aromatic amines from renewable feedstocks.

Full Selectivity Control over the Catalytic Hydrogenation of Nitroaromatics Into Six Products

AbstractA full selectivity control over the catalytic hydrogenation of nitroaromatics leads to the production of six possible products, i.e., nitroso, hydroxylamine, azoxy, azo, hydrazo or aniline compounds, which has however not been achieved in the field of heterogeneous catalysis. Currently, there is no sufficient evidence to support that the catalytic hydrogenation of nitroaromatics with the use of heterogeneous metal catalysts would follow the Haber's mechanistic scheme based on electrochemical reduction. We now demonstrate in this work that it is possible to fully control the catalytic hydrogenation of nitroaromatics into their all six products using a single catalytic system under various conditions. Employing SnO2‐supported Pt nanoparticles facilitated by the surface coordination of ethylenediamine and vanadium species enabled this unprecedented selectivity control. Through systematic investigation into the controlled production of all products and their chemical reactivities, we have constructed a detailed reaction network for the catalytic hydrogenation of nitroaromatics. Crucially, using oxygen‐isolated characterization techniques is essential for identifying unstable compounds such as nitroso, hydroxylamine, hydrazo compounds. The insights gained from this research offer invaluable guidance for selectively transforming nitroaromatics into a wide array of functional N‐containing compounds, both advancing fundamental understanding and fostering practical applications in various fields.

Full Selectivity Control over the Catalytic Hydrogenation of Nitroaromatics Into Six Products.

A full selectivity control over the catalytic hydrogenation of nitroaromatics leads to the production of six possible products, i.e., nitroso, hydroxylamine, azoxy, azo, hydrazo or aniline compounds, which has however not been achieved in the field of heterogeneous catalysis. Currently, there is no sufficient evidence to support that the catalytic hydrogenation of nitroaromatics with the use of heterogeneous metal catalysts would follow the Haber's mechanistic scheme based on electrochemical reduction. We now demonstrate in this work that it is possible to fully control the catalytic hydrogenation of nitroaromatics into their all six products using a single catalytic system under various conditions. Employing SnO2-supported Pt nanoparticles facilitated by the surface coordination of ethylenediamine and vanadium species enabled this unprecedented selectivity control. Through systematic investigation into the controlled production of all products and their chemical reactivities, we have constructed a detailed reaction network for the catalytic hydrogenation of nitroaromatics. Crucially, using oxygen-isolated characterization techniques is essential for identifying unstable compounds such as nitroso, hydroxylamine, hydrazo compounds. The insights gained from this research offer invaluable guidance for selectively transforming nitroaromatics into a wide array of functional N-containing compounds, both advancing fundamental understanding and fostering practical applications in various fields.

Highly dispersed Pd nanoparticles supported by magnetically separable Fe3O4@ SiO2 nanotube for catalytic hydrogenation of nitroaromatics

Selective hydrogenation of nitroaromatics is a crucial industrial reaction, but there are still challenges in developing nanocatalysts with stable active centers, yet easily recyclable characteristics. Here, a magnetically separable Pd/Fe3O4@SiO2 nanocatalyst was prepared through the seeding growth of silica on the Fe3O4 nanocrystal cluster (NC) followed by in situ reduction of Pd nanoparticles (NPs) on the amino group modified Fe3O4@SiO2 nannotube (NT). The nanocatalyst showed good activity and stability in the hydrogenation of a series of nitroaromatics as the Pd NPs were highly dispersed on the nanotubes. Meanwhile, it could be easily separated from the reaction solution and well-redispersed in the solvent for the next-round reaction due to the superparamagnetic property of the Fe3O4 NC and the good dispersibility of silica in many organic solvents. The magnetically separable nanocatalyst combined the high activity of the nanocatalyst and the convenient separation of a traditional heterogeneous catalyst, which effectively promote the practical application of nanomaterials in catalysis.

Highly efficient Zn-MOF derived Carbon-Nitrogen material based catalyst for nitroaromatic Hydrogenation: The role of Zn-O-C bond and Pyridinic-N

Zn-based catalysts have great feature of environmental friendliness and developmental potential to replace precious metals in heterogeneous catalytic hydrogenation. In this work, a porous CN material-based catalysts containing trace Zn were prepared by high-temperature pyrolysis using zeolitic imidazolate framework (ZIF-8) material as precursor. The result shows that (Zn)NC-800 and (Zn)NC-600–700 exhibit outstanding hydrogenation ability and good stability in nitro compounds hydrogenation reaction. Based on the results of characterization and DFT calculations, two hydrogenation active sites complete the hydrogenation of nitro compounds in (Zn)NC-800 and (Zn)NC-600–700: the residual trace Zn in the form of Zn-O-C bond can activate the CN structure and promote the conversion of nitrobenzene; the pyridinic-N is confirmed to accelerate the electron transfer and enhance the selectivity to aniline. This work has an enlightening significance for the efficient development of heterogeneous catalytic hydrogenation catalysts.

Surface crystallized supramolecular to achieve highly dispersed ultrafine nano-palladium in-situ deposition to promote thermal/electrocatalytic reduction

To promote the greening and economization of industrial production, the development of advanced catalyst manufacturing technology with high activity and low cost is an indispensable part. In this study, nitrogen-doped hollow carbon spheres (NHCSs) were used as anchors to construct a supramolecular coating formed by the self-assembly of boron clusters and β-cyclodextrin by surface crystallization strategy, with the help of the weak reducing agent characteristics of boron clusters, highly dispersed ultra-small nano-palladium particles were in-situ embedded on the surface of NHCSs. The deoxygenation hydrogenation of nitroaromatics and the reduction of nitrate to ammonia were used as the representatives of thermal catalytic reduction and electrocatalytic reduction respectively. The excellent properties of the constructed Pd/NHCSs were proved by the probe reaction. In the catalytic hydrogenation of nitroaromatics to aminoaromatics, the reaction kinetic rate and activation energy are at the leading level. At the same time, the constructed Pd/NHCSs can also electrocatalytically reduce nitrate to high value-added ammonia with high activity and selectivity, and the behavior of Pd/NHCSs high selectivity driving nitrate conversion was revealed by density functional theory and in situ attenuated total reflection Fourier transform infrared (ATRFTIR) technique. These results all reflect the feasibility and superiority of in-situ anchoring ultra-small nano-metals as catalysts by surface crystallization to build a supramolecular cladding with reducing properties, which is an effective way to construct high-activity and low-cost advanced catalysts.

Attractive Tandem Hydrogenation of Nitroaromatics Using AB as a Hydrogen Source over Pomelo Peel-Templated Bimetallic CuO–NiO/PP Nanocomposites

Attractive Tandem Hydrogenation of Nitroaromatics Using AB as a Hydrogen Source over Pomelo Peel-Templated Bimetallic CuO–NiO/PP Nanocomposites

Polydopamine-assisted immobilization of metallic nanoparticles confined regionally in bamboo microchannels as continuous-flow microreactors for enhanced catalysis

In contrast to conventional plant-based microreactors where the nanocatalyst is anchored on the inner walls of microchannel structures, this study presents a bamboo-based flow microreactor in which the metallic nanocatalyst is immobilized within polydopamine (PDA) region-modified bamboo microchannels. This novel design facilitates a large surface area for nanocatalyst loading, enhances mass transfer, and reduces nanocatalyst leaching. Firstly, the hierarchical PDA architecture was fabricated on the wall surface of required bamboo microchannels through an ammoniation-induced self-assembly process to serve as a nanocatalyst support layer. The thickness of PDA architectures was modulated by adjusting the flow duration. Secondly, the metallic nanoparticles (NPs), including Pd, Au, and Ag, were effectively immobilized within the hierarchical PDA architectures as highly efficient catalysts using a flow-assisted method with minimal chemical usage and low catalyst loading (Pd content: 0.011 wt%). The catalytic performances of the proposed Pd-PDA/bamboo microreactor were evaluated for the continuous hydrogenation of nitroaromatics under flow conditions, encompassing variations in Pd content, nitroaromatic concentration, and liquid flow rate. The optimized Pd-PDA/bamboo microreactor exhibited high average conversion (>97 %) of nitroaromatics during 20 days of continuous operation without any noticeable deactivation or loss in activity due to its excellent stability resulting from firm immobilization of active metallic NPs within hierarchical PDA architectures. Additionally, this bamboo microreactor demonstrated potential applicability in environmental pollution treatment through azo dye hydrogenation.

Enhancing nitroaromatics reduction through synergistic participation of Ni NPs and nickel ferrite/C nanocomposite: A path towards greener industrial viability

Ni/Fe-citrate gel was reduced in an H2/Ar, forming Ni NPs decorated NiFe2O4-C for eco-friendly nitroaromatics reduction. In-depth characterization of the catalyst highlighted the synergistic interaction between Ni NPs and NiFe2O4 (Ni/NiFe2O4-C), achieving ∼ 99 % conversion of nitroaromatics into amines at 70 °C and 0.5 MPa H2 in water. The cooperative effects of Ni NPs, NiFe2O4, and carbon were instrumental in enhancing the adsorption of hydrogen and nitroaromatics, and the kinetic study showed effectively reducing the activation barrier for the reduction. The HR-TEM, XPS, and H2-TPR provided valuable insights into the formation of Ni NPs and the NiFe2O4 framework, emphasizing their synergistic relationship. Raman spectroscopy and TGA analysis confirmed the formation of carbon. Remarkably, the highly active Ni/NiFe2O4-C catalyst recycled for five cycles without losing activity. p-Aminophenol on 7 g will receive significant attention, emphasizing the substantial promise of this sustainable transition metal-based catalyst for the eco-friendly hydrogenation of nitroaromatics.

Encapsulated Dye in Coordination-Assembled Octahedron for Visible-Light-Driven Proton Reduction and Nitroaromatic Hydrogenation.

To mimic the finely tuned natural photosynthetic systems, a large metal-organic octahedron was synthesized by one-pot self-assembly with modified triphenylamine ligands and redox-active cobalt ions. By encapsulating an organic dye, fluorescein (Fl), within the inner cavity of the octahedron, the host-guest supramolecular system was provided for light-driven hydrogen production. The intimate distance between the redox site and the photosensitizer in the supramolecular metal-organic cage allowed the photoinduced electrons to transfer from the excited state Fl* to the redox cobalt center in a pseudo-intramolecular pathway. The supramolecular system showed good performance in light-driven hydrogen production and the reduction of nitroaromatic compounds. Control experiments based on a mononuclear compound resembling a cobalt corner of the octahedron and inhibitor competition provided evidence of enzyme-like catalytic behavior. The supramolecular reaction pathways within confined spaces contribute to the superior activity of the host-guest system.

Sophisticated construction of single-atom cobalt catalyst based on microbial hyphae for high-performance hydrogenation

Utilizing biomass as a versatile catalyst building platform holds tremendous promise for catalyst design. In this study, we demonstrate a facile and effective method to fabricate high-performance catalysts using Trichoderma afroharzianum hyphae derived carbon fiber (TAHCF) embedded with Co1-N3P1 active sites for nitroaromatic hydrogenation. This strategy leverages the intrinsic self-assembly and metal ion adsorption capabilities of Trichoderma afroharzianum (TA). During the carbonization process, amino acid-rich fungi undergo transformation into biochar substrates co-doped with functional heteroatoms, facilitating the creation of TAHCF single-atom catalyst. Moreover, the catalytic performance can be further enhanced by tailoring the coordination structure of metal atoms on the carbon substrates. Remarkably, we achieve a high turnover frequency of 1553 h−1 for the hydrogenation of nitrobenzene, along with exceptional conversion and selectivity for various nitro compounds with the metal loading as low as 0.02 wt%. Our study presents a characteristic synthetic method that advances the design of single-atom catalysts by leveraging the inherent structure characteristics of biomass in the pursuit of energy sustainability.

Solvent-free selective hydrogenation of nitroaromatics to azoxy compounds over Co single atoms decorated on Nb2O5 nanomeshes

The solvent-free selective hydrogenation of nitroaromatics to azoxy compounds is highly important, yet challenging. Herein, we report an efficient strategy to construct individually dispersed Co atoms decorated on niobium pentaoxide nanomeshes with unique geometric and electronic properties. The use of this supported Co single atom catalysts in the selective hydrogenation of nitrobenzene to azoxybenzene results in high catalytic activity and selectivity, with 99% selectivity and 99% conversion within 0.5 h. Remarkably, it delivers an exceptionally high turnover frequency of 40377 h–1, which is amongst similar state-of-the-art catalysts. In addition, it demonstrates remarkable recyclability, reaction scalability, and wide substrate scope. Density functional theory calculations reveal that the catalytic activity and selectivity are significantly promoted by the unique electronic properties and strong electronic metal-support interaction in Co1/Nb2O5. The absence of precious metals, toxic solvents, and reagents makes this catalyst more appealing for synthesizing azoxy compounds from nitroaromatics. Our findings suggest the great potential of this strategy to access single atom catalysts with boosted activity and selectivity, thus offering blueprints for the design of nanomaterials for organocatalysis.

Ultrasmall Nickel Nanoparticles on a Covalent Triazine Framework for Ammonia Borane Hydrolysis and Transfer Hydrogenation of Nitroaromatics

Ultrasmall Nickel Nanoparticles on a Covalent Triazine Framework for Ammonia Borane Hydrolysis and Transfer Hydrogenation of Nitroaromatics

Metal nanocatalysts confined within hydrophobic zeolite for selective hydrogenation of nitroaromatics

Metal nanocatalysts confined within hydrophobic zeolite for selective hydrogenation of nitroaromatics

Highly dispersed platinum and phosphomolybdic acid (PMo) on the UiO-66 metal–organic framework (MOF) for highly efficient and selective hydrogenation of nitroaromatics

Pt-PMo@UiO-66 (0.32 wt% Pt) shows the highest catalytic activity and selectivity to one –NO2 hydrogenation in nitroarene hydrogenation due to its novel structure and synergism.

Catalysis for the hydrogenation of nitroaromatics by highly dispersed palladium nanoparticles anchored on a resorcin[4]arene-based metal–organic dimer containing amino groups

A new family of resorcin[4]arene-based metal–organic dimers (1–9) were self-assembled, and the catalyst Pd@2 displayed efficient catalytic performance for nitroarene hydrogenation.

Cobalt nanoparticles decorated polyhedral oligomeric silsesquioxane: synthesis, and catalytic hydrogenation of nitroaromatics

Cobalt nanoparticles decorated polyhedral oligomeric silsesquioxane: synthesis, and catalytic hydrogenation of nitroaromatics