Showing papers on "Nitrobenzene published in 2020"

Nitrogen-doped carbon nanotubes as a highly active metal-free catalyst for nitrobenzene hydrogenation

Abstract: A series of metal-free N-doped carbon nanotubes (CNTs) are fabricated using an in-situ synthesis and post nitridation treatment. N-doped carbon nanotubes with various defects, nitrogen contents, and nitrogen species are employed as the catalysts for nitrobenzene hydrogenation. The potential active sites of N-doped carbon nanotubes are explored in terms of catalytic performance in nitrobenzene hydrogenation as well as DFT calculations of hydrogen adsorption on carbon nanotubes and nitrogen species. Active and selective hydrogenation of nitrobenzene is achieved over N-doped carbon nanotubes prepared by post nitridation. Pyrrolic-N in the N-doped carbon nanotubes is found to play an active site for nitrobenzene hydrogenation, which is greatly in favor of the chemisorption and dissociation of hydrogen molecules. N-doped carbon nanotubes with pyrrolic-N show an encouraging catalytic hydrogenation activity in nitrobenzene reduction. These findings provide a promising route for the rational design of the metal-free hydrogenation catalysts and the development of carbon nanotube-based materials.

Highly Efficient Hydrogenation of Nitrobenzene to Aniline over Pt/CeO2 Catalysts: The Shape Effect of the Support and Key Role of Additional Ce3+ Sites

Abstract: Pt/CeO2 catalysts with different support shapes and prereduction temperatures were prepared and tested in the liquid-phase hydrogenation of nitrobenzene. Detailed characterizations reveal that the ...

A multi-responsive chemosensor for highly sensitive and selective detection of Fe3+, Cu2+, Cr2O72- and nitrobenzene based on a luminescent lanthanide metal-organic framework.

Abstract: Excessive release of some hazardous chemicals, such as Fe3+, Cu2+, Cr2O72- and nitrobenzene, may endanger public health and the environment; therefore, targeted effective sensing strategies are important In this report, a series of lanthanide-based metal-organic frameworks (Ln-MOFs), namely {[Ln(dpc)(2H2O)]·(Hbibp)05}n (H4dpc = 2-(3',4'-dicarboxylphenoxy) isophthalic acid, bibp = 4,4'-bis(imidazolyl) biphenyl, for I-VI, Ln = La, Ce, Pr, Nd, Sm, and Eu) were hydrothermally synthesized and characterized Single-crystal X-ray diffraction indicates that I-VI are isostructural and the lanthanide center is nine-coordinated with a distorted tetrakaidecahedral configuration The as-synthesized Ln-MOFs are assembled into three-dimensional frameworks through the connections of dpc4- ligands and hydrogen bonding interactions Notably, Eu-MOF (VI) behaves as a multi-responsive luminescent sensor toward Fe3+, Cu2+, Cr2O72- and nitrobenzene with high sensitivity, selectivity, stability and anti-interference ability against the coexistence of other ions or molecules based on high luminescence quenching efficiency Additionally, Eu-MOF (VI) shows excellent luminescence stability and retains its structural integrity within the pH range of 2-12 in an aqueous solution and its solid sample maintains high thermodynamic stability up to 320 °C Furthermore, the possible luminescence sensing mechanisms have been discussed in detail, and are supported by PXRD analysis, UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS) or density functional theory (DFT)

Metal-Free H2 Activation for Highly Selective Hydrogenation of Nitroaromatics Using Phosphorus-Doped Carbon Nanotubes.

Abstract: We reported that phosphorus-doped carbon nanotubes (P-CNTs), showing metal-like properties, can efficiently promote metal-free hydrogenation of nitrobenzene (1a) to aniline (2a) using molecular hyd...

A novel sustainable metal organic framework as the ultimate aqueous phase sensor for natural hazards: detection of nitrobenzene and F− at the ppb level and rapid and selective adsorption of methylene blue

Abstract: Herein, a new cationic Cu(II)-based porous and water stable metal–organic framework (MOF), [{Cu(bipy)1.5(H2pdm)}·2NO3·H2O]n (Cu-MOF-1), is synthesised via a slow evaporation process using pyridine-2,6-dimethanol (H2pdm) and 4,4′-bipyridine (bipy). The MOF is characterized using Fourier-transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), magnetic analysis and single-crystal X-ray diffraction analysis. The structural unit of Cu-MOF-1 consists of two Cu(II) ions bridged by bipy and supported by H2pdm. This material exhibits excellent sensing ability for nitrobenzene (NB) and fluoride ions (F−) in 100% aqueous medium with an ultra-low limit of detection of 0.093 and 1.203 ppb for NB and F−, respectively. The detection of nitro aromatic compounds (NACs) was found to be governed by photo-induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) mechanisms, while vapour pressure played a major role in NB detection, with a high fluorescence quenching of 96.4%. Moreover, the MOF showed high water stability, significant recyclability and microporosity. The MOF was also employed for the adsorption and separation of methylene blue (MB) from a mixture of three dyes (MB, rhodamine-B and methyl orange). At equilibrium, the removal percentage of Cu-MOF-1 for MB was 98.23% and the mechanism of dye adsorption was also explored. Thus, the present MOF was determined to be a sustainable multifunctional material for the aqueous phase sensing of hazardous NB and fluoride ions, as well as an excellent dye adsorbent.

Highly Efficient Hydrogenation of Nitroarenes by N-Doped Carbon-Supported Cobalt Single-Atom Catalyst in Ethanol/Water Mixed Solvent.

Abstract: The cobalt single atoms supported on N-doped carbon (Co SAs/NC) were prepared by the direct pyrolysis of metal-organic framework (MOF) precursor. Compared with Co nanoparticle (NP) catalysts prepared by impregnation, the Co SAs/NC catalyst showed a much better performance in the selective hydrogenation of nitrobenzene, giving a specific activity 5.4 and 32.0 times higher than those of Co NPs supported on N-doped carbon and active carbon, respectively. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray absorption fine structure (XAFS), X-ray photoelectron spectra (XPS), N2 adsorption-desorption isotherms, and X-ray diffraction (XRD) characterizations revealed that the atomically dispersed Co species and doped nitrogen atoms in carbon support contributed to the high activity of Co SAs/NC. The reaction rate and aniline selectivity were further remarkably enhanced by introducing water into the reaction system. By adding 30% water to the solvent of ethanol, the activity was increased from 43.2 to 76.8 h-1 and the aniline selectivity was increased from 62.8 to 99.1%. Combining experimental results and density functional theory (DFT) calculations evidenced that the promoting effect of water addition was attributed to its differentiating ability in the competitive adsorption between nitrobenzene and aniline in the hydrogenation reaction. This catalytic system was highly efficient for the selective hydrogenation of various nitroarenes.

Cobalt Nanoparticles Encapsulated in Nitrogen-Doped Carbon Shells: Efficient and Stable Catalyst for Nitrobenzene Reduction

Abstract: In this work, cobalt nanoparticles@N-doped carbon nanocomposites (Co@NC) with controllable Co contents have been prepared by pyrolysis of Zn/Co bimetal zeolitic imidazolate framework-9 (Zn/Co-ZIF-9...

Ultrasound-assisted diversion of nitrobenzene derivatives to their aniline equivalents through a heterogeneous magnetic Ag/Fe3O4-IT nanocomposite catalyst

Abstract: A heterogeneous magnetic catalytic system is fabricated and suitably applied for the fast and direct conversion of nitrobenzene (NB) derivatives to their aniline forms. For this purpose, different conditions and methods have been checked with numerous catalytic amounts of the nanocatalyst composite, which was constructed of iron oxide and silver nanoparticles and possessed an isothiazolone organic structure. Herein, the mechanistic aspect of the catalytic functioning of this highly efficient nanocatalyst is highlighted and discussed. Firstly, a convenient preparation route assisted by ultrasonication for this metal and metal oxide nanocomposite is presented. Further, a fast and direct reduction strategy for NBs is investigated using ultrasound irradiation (50 kHz, 200 W L−1). As two great advantages of this catalyst, high magnetic property and excellent reusability are also mentioned. This report well reveals that a really convenient conversion of NBs to anilines can be achieved with a high yield during the rapid reaction time in presence of mild reaction conditions.

Pt decorated hierarchical Sb2WO6 microspheres as a surface functionalized photocatalyst for the visible-light-driven reduction of nitrobenzene to aniline

Abstract: Optimizing the structure of semiconductor materials and introducing functional metal clusters have emerged as an effective strategy to improve the photocatalytic performances of catalysts through the synergistic effect between metals and supports. In this work, Pt nanocluster decorated hierarchical Sb2WO6 microspheres which are assembled from ultra-thin nanosheets with only 3.3 nm thickness (Pt/SWO-NS) jointly achieve an efficient photocatalytic reduction of nitrobenzene to aniline and show 10 times higher activity than Pt decorated bulk Sb2WO6 (Pt/SWO-bulk). More importantly, the respective roles of SWO-NS and Pt nanoclusters are deeply studied. SWO-NS with a unique 2D structure, abundant unsaturated surface sites and good visible light response would be favorable for stabilizing Pt nanoclusters, adsorbing and activating more nitrobenzene molecules and providing abundant photo-generated electrons. Meanwhile, Pt nanoclusters serve as electron enrichment centers to decompose HCOONH4 to produce rich ·CO2− and active H for reducing the activated nitrobenzene molecules. In addition, on combining coordination chemistry, a possible synergistic mechanism for hierarchical Sb2WO6 microspheres and Pt nanoclusters is proposed to elucidate the efficient reduction of nitrobenzene to aniline. We believe that this work would provide an effective strategy to optimize catalytic performance by the design of applicable nanocomposites with synergistic effects.

Convenient conversion of hazardous nitrobenzene derivatives to aniline analogues by Ag nanoparticles, stabilized on a naturally magnetic pumice/chitosan substrate

Abstract: Herein, silver nanoparticles (Ag NPs), as an effective catalyst for the reduction process of nitrobenzene derivatives to non-hazardous and useful aniline derivatives, are conveniently synthesized on an inherently magnetic substrate. For this purpose, an efficient combination of volcanic pumice (VP), which is an extremely porous igneous rock, and a chitosan (CTS) polymeric network is prepared and suitably used for the stabilization of the Ag NPs. High magnetic properties of the fabricated Ag@VP/CTS composite, which have been confirmed via vibrating-sample magnetometer (VSM) analysis, are the first and foremost advantage of the introduced catalytic system since it gives us the opportunity to easily separate the particles and perform purification processes. Briefly, higher yields were obtained in the reduction reactions of nitrobenzenes (NBs) under very mild conditions in a short reaction time. Also, along with the natural biocompatible ingredients (VP and CTS) in the structure, excellent recyclability has been observed for the fabricated Ag@VP/CTS catalytic system, which convinces us to do scaling-up and suggests the presented system can be used for industrial applications.

A new 3D four-fold interpenetrated dia-like luminescent Zn(II)-based metal–organic framework: the sensitive detection of Fe3+, Cr2O72−, and CrO42− in water, and nitrobenzene in ethanol

Abstract: A new three-dimensional zinc-based metal–organic framework, namely [Zn2(4,4′-nba)2(1,4-bib)2]n (1), where 4,4′-H2nba = 3-nitro-4,4′-biphenyldicarboxylic acid and 1,4-bib = 1,4-bis(imidazole-1-ylmethyl)benzene, has been solvothermally synthesized and structurally characterized via single-crystal X-ray diffraction, IR spectroscopic, elemental, thermogravimetric, and Hirshfeld surface analyses. In the crystal structure of 1, the oxygen and nitrogen atoms of two 4,4′-nba2− and two 1,4-bib ligands bind to the metal ion, creating irregular tetrahedral geometry. The 4,4′-nba2− and 1,4-bib ligands serve as linear bidentate linkers to form a four-fold interpenetrated 3D framework with dia-like topology. Luminescence studies revealed that 1 can be used as a highly sensitive multi-responsive luminescent sensor for sensing Fe3+, Cr2O72−, and CrO42− in H2O, and nitrobenzene in C2H5OH. The detection limits of Fe3+, Cr2O72−, CrO42− and nitrobenzene can reach 1.76 μM, 3.25 μM, 3.8 μM and 0.19 μM, respectively. Moreover, 1 can be recycled at least five times for sensing Fe(III) and Cr(VI). The sensitivity and stability of 1, 1@Fe3+, 1@Cr2O72, and 1@CrO42− were also investigated at different pH and temperature values. 1 exhibited satisfactory sensing abilities when the pH ranged from 3 to 10, and the temperature ranged from 5 °C to 75 °C, indicating that 1 could act as a fluorescent probe for Fe3+ under physiological pH conditions. These results support the idea that 1 has good anti-interference abilities and potential for sensing Fe(III), Cr(VI) and nitrobenzene in real environments. In addition, the possible fluorescence quenching mechanism was explored in this paper.

Pickering Emulsions of Fluorinated TiO2: A New Route for Intensification of Photocatalytic Degradation of Nitrobenzene.

Abstract: Fluorination of the TiO2 surface has been often reported as a tool to increase the photocatalytic efficiency due to the beneficial effects in terms of production of oxidizing radicals. Moreover, it is shown that the unique amphiphilic properties of the fluorinated TiO2 (TiO2-F) surface allow one to use this material as a stabilizer for the formulation of Pickering emulsions of poorly soluble pollutants such as nitrobenzene (NB) in water. The emulsions have been characterized in terms of size of the droplets, type of emulsion, possibility of phase inversion, contact angle measurements, and optical microscopy. The emulsified system presents micrometer-sized droplets of pollutant surrounded by the TiO2-F photocatalyst. Consequently, the system can be considered to be composed of microreactors for the degradation of the pollutant, which maximize the contact area between the photocatalyst and substrate. The enhanced photocatalytic activity of TiO2-F was confirmed in the present paper as the apparent rate constants of NB photodegradation were 16 × 10–3 and 12 × 10–3 min–1 for fluorinated and bare TiO2, respectively. At NB concentrations largely exceeding its solubility, the rate constant was 0.04 × 10–3 min–1 in the presence of both TiO2 and TiO2-F. However, unlike TiO2, TiO2-F stabilized NB/water emulsions and, under these conditions, the efficiency of NB photocatalytic degradation in the emulsified system was ca. 18 times higher than in the nonemulsified one. This result is relevant also in terms of practical applications because it opens the route to one-pot treatments of biphasic polluted streams without the need of preliminary physical separation treatments.

Pd nanoparticles stabilized with phosphine-functionalized porous ionic polymer for efficient catalytic hydrogenation of nitroarenes in water

Abstract: Small palladium nanoparticles stabilized with phosphine-functionalized porous ionic polymer (Pd@P(QP-TVP)) were successfully prepared through a free-radical copolymerization, successive anion-exchange and chemical reduction method. Physicochemical characterization studies suggested that the prepared catalyst featured large surface area, a hierarchically porous structure, amphiphilic surface wettability, and strong electron interaction between Pd nanoparticles and the polymer scaffold. We demonstrated the use of the solid catalyst for water-mediated reduction of nitrobenzene with H2 as a hydrogen source. Notably, a low Pd dosage was sufficient for a high yield (99.7%) of aniline with a remarkable turnover frequency (TOF) of 5982 h−1. Furthermore, the Pd@P(QP-TVP) catalyst can be easily recovered and reused at least 5 times without significant loss of activity. Additionally, a number of functional nitroarenes can be efficiently transformed to arylamines in high yields under optimal conditions. Thus, this work provided a highly active, stable and heterogeneous Pd catalyst for the environmentally benign and cost-effective hydrogenation of nitroarenes.