Liquid-phase Hydrogenation Of Nitrobenzene Research Articles

Erratum to: Synthesis of Nickel-Containing Sapropel Based Catalysts and Their Study in the Liquid-Phase Hydrogenation of Nitrobenzene

Erratum

Synthesis of Nickel-Containing Sapropel Based Catalysts and Their Study in the Liquid-Phase Hydrogenation of Nitrobenzene

Synthesis of Nickel-Containing Sapropel Based Catalysts and Their Study in the Liquid-Phase Hydrogenation of Nitrobenzene

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

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 solvent-free, selective liquid phase hydrogenation of nitroarenes to aniline in slurry bubble mode on porous NiMo bimetallic catalyst

NiMo bimetallic catalysts were prepared by a solid reaction method. On the NiMo catalyst, the selective liquid phase hydrogenation of nitrobenzene to aniline was achieved in slurry bubble mode. And the high yields (98.9%) were obtained under the conditions of 80 °C, solvent-free and atmospheric pressure. The effect of Mo on the catalytic behavior of Ni based catalyst was investigated. The characterization displayed that the inclusion of Mo could improve the specific surface area and pore volume, and the solid reaction method made metal Mo enrichment on the surface of catalyst. These two aspects should be responsible for excellent catalytic performance of NiMo catalyst. In sum, we described a simple and efficient NiMo catalyst and provided a facile and green procedure for liquid phase hydrogenation of nitrobenzene to aniline.

KINETICS OF HYDROGENATION OF NITROBENZENE, 4-NITROTOLUENE, 4-NITROANILINE AND 2-CHLORO-4-NITROANILINE ON SUPPORTED PALLADIUM CATALYST

A study of the kinetics of liquid phase hydrogenation of nitrobenzene, 4-nitrotoluene, 4-nitroaniline and 2-chloro-4-nitroaniline on supported palladium catalyst in aqueous solutions of 2-propanol of different composition was carried out. The influence of the substituent on the value of the total amount of hydrogen absorbed during the reaction and the kinetics of the hydrogenation of substituted nitrobenzenes was discussed. It was found out that the reaction selectivity to 2-chloro-1,4-phenylenediamine decreases due to by-reaction dehalogenation. The degree of dehalogenation depends on the composition of solvent and may be approximately estimated by the values of the absorbed hydrogen volume during the reaction. Also, the presence of the donor-acceptor substituents is capable of exerting influence on the reaction rate of hydrogenation of the nitro compound.

Water-soluble palladium nanoparticles as an active catalyst for highly selective hydrogenation of nitrobenzene to aniline

Palladium (Pd) nanoparticles (NPs) stabilized by tri-block copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene (P123) micelles were synthesized in water using a hydrogenation reduction method. Well-dispersed P123 micelles in the aqueous phase favored the stabilization of Pd NPs. The P123–Pd micellar catalyst was first applied in the liquid phase hydrogenation of nitrobenzene (NB), showing excellent catalytic activity, and the only reaction product detected was aniline (AN). Using water as the reaction medium and under mild conditions, both the preparation of catalysts and NB hydrogenation were convenient and environmentally friendly. Under the optimal conditions, the isolated catalyst phase could be recycled at least five times, and the catalytic activity and selectivity remained unchanged. A reaction scheme was suggested. First-order kinetics was determined at 3.0 MPa hydrogen pressure and temperature 30–75 °C, and the activation energy was 40.18 kJ mol−1. This work provides an environmentally benign and effective method for the hydrogenation of NB to AN.

Thermal reduction of graphite oxide derivatives for preparation of supports for platinum hydrogenation catalysts

Thermal reduction of graphite oxide and its derivatives under argon atmosphere has been studied by means of thermogravimetric analysis. Carbon materials prepared via thermal reduction of graphite oxide derivatives in argon at 900°С during 3 h have been used for deposition of platinum from H2PtCl6 solutions. Pt particles supported on the support catalyze liquid-phase hydrogenation of nitrobenzene and dec-1-ene under atmospheric pressure of H2. Thermal reduction of the supports based on graphite oxide results in the formation of the structural defects significantly enhancing the catalytic activity.

Effect of pretreatment of graphite oxide on activity of platinum supported catalysts in liquid-phase hydrogenation

The effect of the reduction procedure of graphite oxide (GO) on activity of platinum supported catalysts in liquid-phase hydrogenation of nitrobenzene and dec-1-ene was studied. The following methods were applied to prepare the catalysts: simultaneous reduction of graphite oxide and H2PtCl6; deposition of platinum on graphite oxide which was preliminary subjected to reduction with sodium tetrahydroborate or hydrazine hydrate, or to thermal reduction at 1000 and 1050 °С. It was shown that at equal Pt particles size of ca. 2 nm the catalyst supported on thermally reduced graphite oxide is more active in the model reactions than the catalysts supported on chemically reduced graphite oxide. The catalyst prepared by simultaneous reduction was the least active.

Encapsulation of Bimetallic Metal Nanoparticles into Robust Zirconium-Based Metal-Organic Frameworks: Evaluation of the Catalytic Potential for Size-Selective Hydrogenation.

The realization of metal nanoparticles (NPs) with bimetallic character and distinct composition for specific catalytic applications is an intensively studied field. Due to the synergy between metals, most bimetallic particles exhibit unique properties that are hardly provided by the individual monometallic counterparts. However, as small-sized NPs possess high surface energy, agglomeration during catalytic reactions is favored. Sufficient stabilization can be achieved by confinement of NPs in porous support materials. In this sense, metal-organic frameworks (MOFs) in particular have gained a lot of attention during the last years; however, encapsulation of bimetallic species remains challenging. Herein, the exclusive embedding of preformed core-shell PdPt and RuPt NPs into chemically robust Zr-based MOFs is presented. Microstructural characterization manifests partial retention of the core-shell systems after successful encapsulation without harming the crystallinity of the microporous support. The resulting chemically robust NP@UiO-66 materials exhibit enhanced catalytic activity towards the liquid-phase hydrogenation of nitrobenzene, competitive with commercially used Pt on activated carbon, but with superior size-selectivity for sterically varied substrates.

Liquid phase hydrogenation of nitrobenzene

Hydrogenation of nitrobenzene (NB) was carried out in methanol solutions (initial concentration 0.8moll−1) over a Pd/C catalyst (3wt.% of Pd; reaction mixture contained 2.2mgPdl−1) over the pressure range of 2–4MPa and temperature 30–70°C in a laboratory scale batch reactor. Zero order kinetics was observed at hydrogen pressures above 2MPa Under applied experimental conditions the apparent activation energy was 35±1kJmol−1. A detailed analysis of the reaction mixture inspired the hypothesis that a C6H5–NO(H) moiety is formed on the catalyst surface and it undergoes further condensation to azoxybenzene (AOB) releasing water. However, very low concentrations of azobenzene (AB) and hydrazobenzene (HAB) in the reaction mixture indicate that the reaction route to the formation of aniline by hydrogenation of AOB to AB, hydrazobenzene (HAB) and subsequent hydrogenolysis to AN is of low probability. Hydrogenolysis of AOB to C6H5–NO(H) and C6H5–N(H), where the latter is hydrogenated to AN, is more likely. Based on the experimental observations a new reaction scheme for the heterogeneous catalytic hydrogenation of NB was proposed.

Liquid-phase hydrogenation of nitrobenzene and o-nitrochlorobenzene in the presence of phosphorus-containing palladium nanoparticles

The properties of phosphorus-modified palladium catalysts in the liquid-phase hydrogenation of nitrobenzene and o-nitrochlorobenzene have been investigated. A general regularity in the reduction of the nitro compounds in the presence of the phosphorus-containing palladium catalysts is an autoacceleration observed at large P: Pd ratios of 0.7–1.5. The autoacceleration is due to a redox process between the intermediate (azoxy derivative) and PdP2, a component of the catalyst nanoparticles. A promoting effect of elemental phosphorus on the chemoselectivity of the Pd-P catalysts in o-nitrochlorobenzene hydrogenation has been discovered. The main factors responsible for the changes in the quantitative characteristics of the phosphorus-modified palladium nanoparticles are considered. Among these factors there are the nature of the nanoparticles, their size, and the state of the surface layer. The properties of the Pd-P catalysts are determined by the proportions of palladium clusters and palladium phosphides (Pd(0) and Pd x P) in the nanoparticles. The formation of the clusters and phosphides has been confirmed by X-ray diffraction and X-ray photoelectron spectroscopy.

Influence of preparation method and palladium content on Pd/C catalysts activity in the liquid phase hydrogenation of nitrobenzene to aniline

Two sets of Pd/C catalysts with 1–10wt.% Pd content supported on active carbon were prepared by a conventional formaldehyde method. One set was prepared using H2[PdCl4] complex and other one with Na2[PdCl4]. In spite of different metal loadings, average crystallite size of palladium particles estimated by XRD and TEM analyses was virtually the same in all the cases, from 3 to 5nm. Catalysts were tested for nitrobenzene hydrogenation in a stirred autoclave with the presence of methanol as a solvent, at 5MPa and 50°C. Ratio of Pd to nitrobenzene substrate was in every reaction mixture the same: 15.4mg of palladium per mol of nitrobenzene. Specific initial catalyst activity (initial reaction rate) for catalysts with 1–4wt.% Pd content for both sets of catalysts was comparable. It means that palladium complex used for the preparation had no-effect on catalyst activity. With palladium content higher than 4wt.% a significant drop in the catalytic activity and increase in amount of the leached palladium were observed, which should be prescribed for the formation of agglomerates of palladium crystallites (revealed by TEM) and consequent decrease in concentration of catalytic sites. Because of a decrease in catalytic activity, the reaction times were longer, which caused a higher metal leaching.

Hydrogenation of nitrobenzene to p-aminophenol using Pt/C catalyst and carbon-based solid acid

Liquid phase hydrogenation of nitrobenzene to p-aminophenol (PAP) in water was studied over a catalyst system composed of Pt/C and carbon-based solid acid which was prepared by one-step hydrothermal carbonization of various carbon sources including starch, sucrose, glucose and furfural in sulfuric acid aqueous solution at 180°C for 4h. The effects of carbon-based solid acid type, Pt/C catalyst loading, hydrogen pressure and reaction temperature on nitrobenzene conversion and PAP selectivity were investigated. The results showed that PAP selectivity was favored at high acid density of the carbon-based solid acid. The carbon-based solid acid prepared from starch, with the highest SO3H amount, gave the highest PAP selectivity among the catalysts used. An increase in Pt/C catalyst loading led to an increased nitrobenzene conversion but a decreased PAP selectivity. A high reaction temperature was in favor of nitrobenzene conversion and PAP selectivity. Under the optimal reaction conditions, nitrobenzene conversion and PAP selectivity reached 61.0% and 77.8%, respectively.

Self-assembly of Mesoporous Ni–P Nanosphere Catalyst with Uniform Size and Enhanced Catalytic Activity in Nitrobenzene Hydrogenation

Mesoporous Ni–P amorphous alloy nanospheres with controllable sizes and compositions were synthesized by chemical reduction of Ni(OH)2 colloidal particles co-assembling with surfactant hexadecyl-trimethyl-ammonium bromide in liquid crystal mesophase using hypophosphite as reductant. The effects of the synthesis conditions on the particle size, composition and mesostructure of the mesoporous Ni–P nanospheres were systematically studied. It was found that the size of the mesoporous Ni–P nanospheres could be tuned from 35 to 90 nm by changing the reduction temperature, and the phosphorus content of the Ni–P products could be adjusted in the range of 20.1 to 27.6 % by changing the molar ratio of H2PO2 −/Ni2+. The active surface area and the thermal stability of the mesoporous Ni–P nanosphere catalyst are much higher than those for the conventional nonporous Ni–P amorphous alloy. In the liquid phase hydrogenation of nitrobenzene, the typical mesoporous Ni–P nanosphere catalyst exhibits much higher activity and better selectivity than the conventional nonporous Ni–P. The correlation between the catalytic performance and the structural properties is discussed based on the results of detailed characterization.

Volcano-Curves for Dehydrogenation of 2-Propanol and Hydrogenation of Nitrobenzene by SiO2-Supported Metal Nanoparticles Catalysts As Described in Terms of a d-Band Model

To confirm whether the activity trends in multistep organic reactions can be understood in terms of the Hammer–Norskov d-band model in combination with the linear energy relations, we studied correlations between the reaction rates for dehydrogenation and hydrogenation reactions and the position of the d-band center (ed) relative to the Fermi energy (EF), the ed – EF value, of various metal catalysts. SiO2-supported metal (M = Ag, Cu, Pt, Ir, Pd, Rh, Ru, Ni, and Co) catalysts with the same metal loading (5 wt %) and similar metal particle size (8.9–11.7 nm) were prepared. The dehydrogenation of adsorbed 2-propanol in a flow of He and the hydrogenation of adsorbed nitrobenzene in a flow of H2 were tested as model reactions of organic reactions on the metal surface. As a test reaction of H2 dissociation on the surface, SiOH/SiOD exchange on the M/SiO2 catalysts in a flow of D2 is carried out. The liquid phase hydrogenation of nitrobenzene under 3.0 MPa of H2 is adopted as an organic reaction under realistic...

Liquid Phase Hydrogenation of Nitrobenzene over Nickel Supported on Titania

The catalytic hydrogenation of nitrobenzene to aniline employing nickel impregnated on rutile, anatase, and high surface area titania supports has been investigated. The nickel is present in elemental state as fcc phase on the catalyst as evidenced by X-ray diffraction results. The Ni crystallite size was found to be greater for Ni/anatase. The temperature-programmed reduction results suggest a greater metal-support interaction for Ni/rutile. The observed order of catalytic activity for the hydrogenation of nitrobenzene is Ni/rutile > Ni/anatase > Ni/TiO 2 . A conversion of 99% was observed for Ni/rutile at 140°C and hydrogen pressure of 1.96 MPa. Interestingly, aniline is the only product formed which demonstrates the catalytic hydrogenation of nitrobenzene proceeds with atom economy. Both Ni/rutile and Ni/anatase exhibited a better stability than Ni/TiO 2 . The hydrogenation proceeds with the preferential adsorption of hydrogen on nickel present in the catalyst surface, possibly assisted by TiO x species. The hydrogenation of nitrobenzene on nickel supported titania catalysts takes place with the preferential adsorption of hydrogen to form nickel hydride species. Ni/rutile catalyst is found to possess better activity and stability. Aniline is formed exclusively suggesting the reduction proceeds with atom economy.

The Dynamic Structure of Gold Supported on Ceria in the Liquid Phase Hydrogenation of Nitrobenzene

AbstractWith regard to heterogeneous catalysis by gold and, in particular, hydrogenation reactions, there is no consensus on the oxidation state of the catalytically active species. By means of high‐resolution X‐ray absorption spectroscopy, we determined in situ the oxidation state of gold in the functioning catalyst Au/CeO2 in the slurry phase of the hydrogenation of nitrobenzene at high pressure. The conversion of nitrobenzene was monitored simultaneously by means of online attenuated total reflectance–Fourier transform infrared spectroscopy. We found that catalysts without measurable amounts of cationic gold were more active than catalysts with cationic gold. Any cationic gold that remained after pretreatment was reduced under reaction conditions, without any loss of activity. No evidence was found that the cationic gold contributed to the catalytic activity.

Platinum- and palladium-containing carbon nanomaterials as catalysts for hydrogenation and hydrogenating amination

The catalytic activity of the carbon nanomaterials containing platinum and palladium in the model reactions of liquid-phase hydrogenation of nitrobenzene and hydrogenating amination was investigated. The catalytic systems based on nanodiamonds are more efficient than platinum-containing fullerene black, multi-walled nanotubes, and carbon nanofibers.

Liquid-Phase Hydrogenation of Nitrobenzene over Ag-Ni Bimetallic Catalysts Prepared by Adsorption Phase Synthesis

Liquid-Phase Hydrogenation of Nitrobenzene over Ag-Ni Bimetallic Catalysts Prepared by Adsorption Phase Synthesis

Liquid Phase Hydrogenation of Nitrobenzene to Para-Aminophenol over Pt/ZrO2 Catalyst and SO4 2−/ZrO2–Al2O3 Solid Acid

ZrO2–Al2O3 binary oxide was prepared by homogeneous coprecipitation method. SO4 2−/ZrO2 and SO4 2−/ZrO2–Al2O3 were prepared by impregnation method and were characterized by BET, XRD and TPD. Pt/ZrO2 was prepared by incipient wetness impregnation of ZrO2 with an aqueous solution of H2PtCl6. Subsequently, hydrogenation of nitrobenzene to para-aminophenol over Pt/ZrO2 catalyst and SO4 2−/ZrO2–Al2O3 solid acid using water as solvent was performed. The results indicate that para-aminophenol as well as a small quantity of aniline and ortho-aminophenol are obtained without using any environmentally undesirable liquid acid. The para-aminophenol selectivity reaches to 74.9% with 44.8% of nitrobenzene conversion under the optimal reaction conditions. And the amount of Al2O3 in SO4 2−/ZrO2–Al2O3 has great influence on the selectivity to para-aminophenol. Hydrogenation of nitrobenzene to para-aminophenol over Pt/ZrO2 catalyst andSO4 2−/ZrO2–Al2O3 solid acid was developed. The results indicate that para-aminophenol as well as a small quantity of aniline and ortho-aminophenol are obtained without using any environmentally undesirable liquid acid. The para-aminophenol selectivity reaches to 74.9 with 44.8% of nitrobenzene conversion under the optimal reaction conditions. And the amount of Al2O3 in SO4 2−/ZrO2–Al2O3 has great influence on the selectivity to para-aminophenol.