Catalyst For Hydrogenation Of Nitrobenzene Research Articles

Using Density Functional Theory To Unravel the Size-Dependent Effect of Au Nanoparticles and Au Single Atoms Adsorbed on Carbon Nitride for the Hydrogenation of Nitrobenzene

Hydrogenation of nitrobenzene to aniline is extensively applied in the chemical and pharmaceutical industries, and exploring high-activity and environmentally friendly nanoscale catalysts remains a great challenge. Herein, we investigated the activity of Au(100) nanoparticles, Au single-atom catalysts, and Au cluster catalysts of different sizes anchored on C2N for the hydrogenation of nitrobenzene to aniline based on density functional theory. The results indicate that the Au single-atom catalyst shows excellent activity for nitrobenzene to aniline with an extremely low limiting potential (UL = −0.45 V). In addition, the hydrogenation mechanism of nitrobenzene on different sizes of Au catalysts is elucidated by electronic structure information and thermodynamics. This indicates that the high metal activity of the Au single-atom catalyst and the efficient desorption of aniline are essential as superior catalysts for hydrogenation of nitrobenzene to aniline. This work not only explores an efficient nanoscale catalyst for nitrobenzene hydrogenation but also provides an idea for tuning the size of transition metals to enhance catalytic capacity.

NICKEL CATALYTIC ACTIVITIES ON THE SUPPORTS OF SILICA AND ACTIVATED CARBON EXTRACTION FROM LOCAL RICE HUSK FOR NITROBENZENE HYDROGENATION: A COMPARATIVE STUDY

Activated carbon (RHAC) and Silica (RHSiO2) both were prepared from Rice Husk (RH) with very simple methods. These supports were used for the preparation of Ni catalyst for hydrogenation of nitrobenzene by wet impregnation and reductive deposition method. Ni/RHSiO2 and Ni/RHAC catalysts are characterized by BET, XRD, SEM, and TPR techniques. Well, dispersion of Ni on these supports shows excellent conversion of nitrobenzene to Aniline.

Development of Highly Efficient, Glassy Carbon Foam Supported, Palladium Catalysts for Hydrogenation of Nitrobenzene.

Glassy carbon foam (GCF) catalyst supports were synthesized from waste polyurethane elastomers by impregnating them in sucrose solution followed by pyrolysis and activation (AC) using N2 and CO2 gas. The palladium nanoparticles were formed from Pd(NO3)2. The formed palladium nanoparticles are highly dispersive because the mean diameters are 8.0 ± 4.3 (Pd/GCF), 7.6 ± 4.2 (Pd/GCF-AC1) and 4.4 ± 1.6 nm (Pd/GCF-AC2). Oxidative post-treatment by CO2 of the supports resulted in the formation of hydroxyl groups on the GCF surfaces, leading to a decrease in zeta potential. The decreased zeta potential increased the wettability of the GCF supports. This, and the interactions between –OH groups and Pd ions, decreased the particle size of palladium. The catalysts were tested in the hydrogenation of nitrobenzene. The non-treated, glassy-carbon-supported catalyst (Pd/GCF) resulted in a 99.2% aniline yield at 293 K and 50 bar hydrogen pressure, but the reaction was slightly slower than other catalysts. The catalysts on the post-treated (activated) supports showed higher catalytic activity and the rate of hydrogenation was higher. The maximum attained aniline selectivities were 99.0% (Pd/GCF-AC1) at 293 K and 98.0% (Pd/GCF-AC2) at 323 K.

Highly Efficient Mesoporous Core-Shell Structured Ag@SiO2 Nanosphere as an Environmentally Friendly Catalyst for Hydrogenation of Nitrobenzene.

The size-uniformed mesoporous Ag@SiO2 nanospheres’ catalysts were prepared in one-pot step via reducing AgNO3 by different types of aldehyde, which could control the size of Ag@SiO2 NPs and exhibit excellent catalytic activity for the hydrogenation of nitrobenzene. The results showed that the Ag core size, monitored by different aldehydes with different reducing abilities, together with the ideal monodisperse core-shell mesoporous structure, was quite important to affect its superior catalytic performances. Moreover, the stability of Ag fixed in the core during reaction for 6 h under 2.0 MPa, 140 °C made this type of Ag@SiO2 catalyst separable and environmentally friendly compared with those conventional homogeneous catalysts and metal NPs catalysts. The best catalyst with smaller Ag cores was prepared by strong reducing agents such as CH2O. The conversion of nitrobenzene can reach 99.9%, the selectivity was 100% and the catalyst maintained its activity after several cycles, and thus, it is a useful novel candidate for the production of aniline.

Application of carbon nanotube coated aluminosilicate beads as “support on support” catalyst for hydrogenation of nitrobenzene

Nitrogen-doped bamboo-like carbon nanotube (N-BCNT) coating was synthesized onto the surface of zeolite beads by using Catalytic Chemical Vapour Deposition (CCVD) method to develop a “support on support” (SoS) system. These complex structured materials were used as supports during the preparation of hydrogenation catalysts. Rhodium, palladium and platinum nanoparticles were deposited homogeneously onto the surface of the N-BCNTs of the SoS (final metal content 2wt%). The catalytic activity of these samples was compared in the hydrogenation of nitrobenzene. The Pt/N-BCNT-zeolite sample was the most active (182mol nitrobenzene after 30min). The activity of the other two catalysts at 20bar was well below this value, 99.5mol after 60min and 96mol after 120min for Pd and Rh, respectively. The aniline selectivity was different for the three catalysts and they facilitate the formation of various by-products (e.g. N-methylaniline, cyclohexylamine). The usage of the Pd and Pt/N-BCNT-zeolite catalysts are more convenient, as only one main by-product was formed. It was confirmed that the zeolite supported N-BCNTs are efficient catalyst supports in hydrogenation processes. Furthermore, by using this special SoS structure to support the catalytic metals the applicability is widened and the catalyst removal is easier.

PVA‐encapsulated Palladium Nanoparticles: Eco‐friendly and Highly Selective Catalyst for Hydrogenation of Nitrobenzene in Aqueous Medium

In aqueous medium without any other additives, palladium (Pd) nanoparticles with water-soluble polyvinyl alcohol (PVA) as stabilizer were synthesized for the catalytic hydrogenation of nitrobenzene. Under the optimum experimental conditions, the nitrobenzene conversion and the selectivity for aniline were 99.3 % and 100 %, respectively. Comprehensive characterization methods, including TEM, UV/Vis, confocal laser scanning microscopy (CLSM), XRD and XPS allowed a better understanding of the role of PVA aggregates and the properties of Pd nanoparticles. The nitrobenzene conversion exceeded 80 % even after 6 cycles without any treatment of the catalyst. A mechanism about the hydrogenation of nitrobenzene catalyzed by Pd/PVA system was proposed. The Pd/PVA catalyst also exhibited excellent activity and selectivity, particularly to ortho-fluoronitrobenzene and ortho-nitrotoluene. This research can provide a reference for the environmentally friendly catalysis for hydrogenation of nitrobenzene and other substituted nitrobenzene compounds.

A carboxylic acid functionalized SBA-15 supported Pd nanocatalyst: an efficient catalyst for hydrogenation of nitrobenzene to aniline in water

The catalytic performance of a PdNPs/SBA-COOH has been investigated for the first time in the selective hydrogenation of nitrobenzene with hydrous hydrazine at RT in water medium.

Facile-fabricated iron oxide nanorods as a catalyst for hydrogenation of nitrobenzene

β-FeOOH nanorods were prepared by a poly ethylene glycol (PEG) assisted precipitation of FeCl3 ∙ 6H2O aqueous solution with urea. Na2CO3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The as-prepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH (iron oxides hydroxide) nanorods, fabricated by annealing β-FeOOH nanorods at 250°C in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.

Ligand-controlled fabrication of core-shell PdNi bimetallic nanoparticles as a highly efficient hydrogenation catalyst

A series of PdNi/SiO2 bimetallic nanoparticles were synthesized using polyvinylpyrrolidone (PVP) and 2,6-bis(5,6-dimethyl-1,2,4-triazine-3-yl) pyridine (BTP) as ligands through sol-gel method. BTP was proved to be an effective ligand that can delay the reduction of palladium (II), which helps the formation of palladium-rich shell bimetallic nanoparticles. Pd3Ni7-BTP/SiO2 exhibited the best catalytic performance (TOF=180h−1) among all the catalysts for hydrogenation of nitrobenzene under ambient conditions and was successfully reused for at least five times without loss in activity. The excellent catalytic performance could be ascribed to the small nanoparticle size (2.14nm) and the palladium-rich shell structure it bears.

Monolithic catalysts for hydrogenation of nitrobenzene to aniline: influence of aluminum suspension properties

Aluminum suspensions with different properties were prepared and characterized by UV–Vis spectra, BET, XRD and NH3-TPD. A layer of Al2O3 was coated onto the cordierite monolith by sol–gel method. Pd/Al2O3/cordierite monolith catalysts with the same Pd loading and particle size were prepared, and tested by nitrobenzene hydrogenation under solvent-free conditions. The adsorption of nitrobenzene on acid sites might be the primary effect under the reaction conditions, and a good linear relationship between hydrogenation rate and the acid content of the Al2O3 layer was observed. Furthermore, the stronger acid sites were responsible for the lower aniline selectivity.

Reduced graphene oxide as a catalyst for hydrogenation of nitrobenzene at room temperature

Reduced graphene oxide was used as a catalyst for reduction of nitrobenzene at room temperature. High catalytic activity and stability were exhibited in circular experiments. The catalytic procedure was in situ monitored by NMR and N-phenylhydroxylamine was proved to be the intermediate in this catalytic reaction.

Pt–Pd bi-metal nanoparticles captured and stabilized by imine groups in a periodic mesoporous organosilica of SBA-15 for hydrogenation of nitrobenzene

Pt–Pd bi-metal nanoparticles (bi-MNPs) captured and stabilized by imine groups inside a periodic mesoporous organosilica of SBA-15 (PMO-SBA-15) and their catalytic performances in the hydrogenation of nitrobenzene were investigated. The PMO-SBA-15 was synthesized via a one-pot condensation process by hydrolysis of tetraethoxysilane (TEOS) in the presence of P123 (EO 20PO 70EO 20) involving the assembly of triethylenetetramine silsesquioxane organic precursor. Aqueous PtCl 6 2 - and Pd 2+ ions were reduced by NaBH 4 to form Pt and Pd nanopaprticles, which were captured in real-time by imine groups inside the channels of the PMO-SBA-15 to obtain the sample of Pt–Pd/PMO-SBA-15. The obtained samples were characterized by TG-DTG analysis, FT-IR spectra, XRD, N 2 adsorption–desorption measurement and TEM micrograph. The results indicated that both the PMO-SBA-15 and Pt–Pd/PMO-SBA-15 retained the typical characteristics of mesoporous SBA-15 and the dispersed Pt–Pd bi-MNPs well entrapped into the channels of PMO-SBA-15 with the size of ca. 2.5 nm. The MNPs/PMO-SBA-15 was used as a catalyst for hydrogenation of nitrobenzene under 0.1 MPa H 2 at 15–60 °C. It was found that the bi-MNPs of Pt and Pd inside the PMO-SBA-15 were more active than the monometallic Pt or Pd nanoparticles due to the synergetic effect and the segregation behavior between Pt and Pd interaction. 100% of nitrobenzene conversion and >99% of selectivity to aniline were obtained over the Pt–Pd/PMO-SBA-15 (Pt:Pd = 1:1) catalyst. Furthermore, the Pt–Pd/PMO-SBA-15 catalyst could be recovered for reuse without significant loss of catalytic activity and selectivity.

Preparation of magnetic γ‐Al2O3 supported palladium catalyst for hydrogenation of nitrobenzene

AbstractSpherical alumina support with magnetic core of 134 nm in diameter was prepared by the controlled hydrolysis of aluminums iso‐propoxide. The magnetite Fe3O4 nanoparticles were first synthesized by coprecipitation. Later silica film was coated onto the surface of Fe3O4 nano particles with the sodium silicate acidification method. Alumina was supported on Fe3O4/SiO2 film by the controlled hydrolysis of aluminum alkoxide in a dilute solution consisting of cyclohexane and 2‐propanol. Finally, magnetic alumina supported palladium catalysts were prepared by microemulsion method. The surface morphology and crystal structure of the magnetic alumina and catalysts were characterized by XRD, TEM, BET, and VSM, respectively. The results showed that these kinds of composite particle exhibit superparamagnetic behavior with zero coercivity and remanence. The catalysts show high activity for nitrobenzene directly hydrogenating to aniline under mild conditions. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Polymer-Protected Ni/Pd Bimetallic Nano-Clusters: Preparation, Characterization and Catalysis for Hydrogenation of Nitrobenzene

Well-dispersed and stable colloidal dispersions of polymer-protected Ni/Pd bimetallic nanoclusters have been obtained over an entire composition range by an improved polyol reduction method, in which nickel(II) sulfate and palladium(II) acetate were reduced at high temperature by ethylene glycol in the presence of poly(N-vinyl-2-pyrrolidone). Transmission electron microscopy indicates that these bimetallic nanocluster particles have definitely monodispersed size-distributions, with each particle containing both nickel and palladium atoms. The alloy structure has also been shown by X-ray diffraction and extended X-ray absorption fine-structure analysis. X-ray absorption near-edge spectroscopic and X-ray photoelectron spectroscopic data have confirmed that the nickel in the bimetallic nanoclusters is in the zero-valence state, as stabilized by the presence of Pd. Dispersions of these bimetallic nanoclusters were used as homogeneous catalysts for hydrogenation of nitrobenzene at 30 °C under an atmospheric pressure of hydrogen. The catalytic activities are demonstrated to be dependent on the metal composition of the particles. The highest activity can be achieved for a bimetallic nanocluster with a molar ratio of Ni:Pd = 2:3, which exhibits 3.5 times greater activity than that of a typical colloidal palladium catalyst.

EPR STUDY OF THE SYSTEM [DIAQUOCOBALOXIME + AMINE] AS A CATALYST FOR THE HYDROGENATION OF NITROBENZENE

Abstract Reaction of cobalt dimethylglyoxime dihydrate with amines gives rise to a catalyst for hydrogenation of nitrobenzene. Solutions of this catalyst in acetone are paramagnetic and EPR spectra of these solutions were measured. The presence of nitrobenzene considerably alters the EPR spectra. It was also observed that electron transfer from cobaloximes to TCNE is only possible in the presence of PhNO2. Changes of the EPR spectra during catalytic process were observed and interpreted.

EPR Studies of solvent coordination in bis(dimethylglyoxime)cobalt II complexes as catalysts for hydrogenation of nitrobenzene

EPR spectra of diaquocobaloxime and dimorpholine cobaloxime in different solvents have been studied in frozen solutions. It has been observed that magnetic parameters for solvent complexed cobaloximes depend strongly on the nature of the solvent, whereas morpholine-complexed cobaloxime shows no substantial variation of magnetic parameters with the solvents. The rates of nitrobenzene hydrogenation catalyzed by cobaloximes show considerable variation with solvent. It has been concluded that three elementary processes important for catalysis: hydrogen and nitrobenzene activation as well as hydrogen transfer, take place in the region of the active complex remote from the z axis.

Preparation of new cobaloximes and their use as precursors of active catalyst for hydrogenation of nitrobenzene

Preparation of new cobaloximes and their use as precursors of active catalyst for hydrogenation of nitrobenzene