Selective Reduction Of Nitrobenzene Research Articles

CuO-NiO-TiO2 bimetallic nanocomposites for catalytic applications

CuO-NiO-TiO2 nanocomposites with of 0.01–5.0 wt.% of Cu:Ni (1:1) supported on TiO2 were prepared by a decomposition method. The catalysts structure and chemical composition were studied by means of XRD, SEM, EDX, TEM, FT-IR, UV–DRS, BET-analysis and compared for direct sunlight photo-degradation of methylene blue with commercial P25 catalyst. These studies revealed that the catalyst efficiency solely depends on the percentage of Cu-Ni dopants. The catalyst with low metal dopants displayed better photocatalytic activity. The optimum doping concentration for photo-degradation was 0.05 wt.%. The nanocomposite with higher metal loading (5.0 wt.%) was effectively employed as heterogenous catalyst for selective reduction of nitro benzene to aniline using sodium borohydride and for air oxidation of tertiary amine functionality to a tertiary amide. The synergistic effect of the metals was confirmed by comparing the catalytic activity with individual metal dopings.

The durability of carbon nanotubes in the selective reduction of nitrobenzene.

Surface oxidized carbon nanotubes (oCNTs) were quite stable for the selective reduction of nitrobenzene, while notable deactivation was observed for the un-oxidized sample (rCNTs). The adsorption of N-containing compounds had a negligible effect, but the formation of a carboxyl group and anhydride was mainly responsible for the deactivation of rCNTs.

Highly active TiO2/g-C3N4/G photocatalyst with extended spectral response towards selective reduction of nitrobenzene

A simple self-assembly photochemical reduction method has been proposed to prepare highly photocatalytic TiO2 nanowire/g-C3N4 nanosheet/graphene heterostructures (TiO2/g-C3N4/G). In this hybrid structure, graphene enhances the charge transportation during photocatalytic process, and TiO2 nanowires prevent graphene and g-C3N4 from restacking. Meanwhile, g-C3N4 with a more suitable band gap, extends the adsorption edge of the TiO2/g-C3N4/G composite to visual-region. Benefiting from the positive synergetic effect, 97% of nitrobenzene can be selectively reduced within 4h by using TiO2/g-C3N4/G as the photocatalyst. The TiO2/g-C3N4/G composite with 3D structure demonstrates a great potential in selective oxidation and reduction of organics for the synthesis of high added-value organic compounds.

Identifying active sites of CoNC/CNT from pyrolysis of molecularly defined complexes for oxidative esterification and hydrogenation reactions

Cobalt chelate complexes bonded to 2 to 3 nitrogens in the graphene lattice are the active sites for the oxidative esterification of benzyl alcohol by molecular oxygen, the selective reduction of nitrobenzene by hydrogen and the hydrogenated coupling of nitrobenzene and benzaldehyde.

Cogeneration of cyclohexylamine and electrical power using PEM fuel cell reactor

Cogeneration of cyclohexylamine (CHA) and electrical power using a PEM fuel cell reactor were performed by the selective reduction of nitrobenzene (NB). The maximum power density was 1.5 mW cm −2 at a current density of 15 mA cm −2 during cogeneration with the reduction of NB in ethanol. The current density varied from 1.6 to 24 mA cm −2 with the change of external load. A selectivity of 57.3% to CHA, and a selectivity of 28.2% to aniline (AN), with 8.2% conversion of NB were obtained when the hydrogen flow rate was 20 ml min −1 at 70 °C for 2 h. Effects of Pt catalyst loading and NB concentration on the behavior of cogeneration were also studied.

Role of alkali promoters on Mn 3O 4 in the selective reduction of nitrobenzene

The influence of Li +, Na + and K + ions on the activity and selectivity of Mn 3O 4 in the selective reduction of nitrobenzene has been studied. The alkali ions show both a promoting (low concentrations) and a blocking (higher concentrations) effect. Reducibility measurements of the various catalysts (thermogravimetry, temperature-programmed reduction), adsorption heat experiments (heat-flow microcalorimetry) and determination of the composition of the surface layers (X-ray photoelectron spectroscopy) exclude an influence of the promoter on the reducibility of the catalyst, on the heat of adsorption of nitrobenzene and on the oxidation state of manganese. It can be seen that most of the alkali ions are present in the surface layers of the catalyst. The most likely mechanism is that by which the promoter influences a certain adsorption mode of nitrobenzene existing at the reaction temperature on the surface of Mn 3O 4.

Alkali hydroxides as promoters of Mn 3O 4 in the selective reduction of nitrobenzene; an X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and ion scattering spectroscopy study

The promoting mechanism of alkali ions on Mn 3O 4 in the selective reduction of nitrobenzene has been investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and ion scattering spectroscopy. It appeared that the alkali ions accumulate on the outermost surface layer, but do not change the oxidation state of manganese. Heating of the fresh catalysts in ultra-high vacuum results in a disappearance of the alkali ions from the surface. This shows that the alkali ions migrate easily over the surface at elevated temperatures. However, when the catalysts have been treated with nitrobenzene, the same heating procedure does not result in a disappearance of the promoter ions. Moreover, it can be seen that the surface has been covered with adsorbates derived from nitrobenzene. It can be concluded that the promoting effect is not due to the electronic structure changes in the interior of the Mn 3O 4 catalyst, but is rather due to one of the following mechanisms: (a) an electrostatic field effect of alkali cations or (b) the formation of intermediates with the reaction components, in the adsorbed layer.

Study of the catalytic activity of metal complexes attached to a solid support. 6. Reduction of nitrobenzene and its halogenated derivatives by chemically bound hydrogen in the presence of immobilized Rh complexes

1. Rhodium complexes [(RhCl (COD)]2, RhCl(PPh3)3, and RhCl3 immobilized on silica gel modified by amino and aminophosphine groups catalyze selective reduction of nitrobenzene into aniline in Ar medium (25–82.4°C) by transfer of hydrogen from 2-propanol (KOH promotor) and sodium borohydride. 2. The rate of reduction of nitrobenzene by sodium borohydride is one to two orders of magnitude higher than with 2-propanol. 3. Incorporation of a halogen in the benzene ring results in a decrease in the rate of reduction of the nitro group. Reduction of halonitrobenzenes by sodium borohydride takes place in two stages: The NO2 group is reduced first, and the halogen is then cleaved.

Selective reduction of nitrobenzene to nitrosobenzene on oxidic catalysts

Pure unpromoted Mn3O4 appears to be a very suitable catalyst for the selective reduction of nitrobenzene to nitrosobenzene; the oxygen vacancies required to split off oxygen atoms can be created both by the phenyl group of nitrobenzene itself and by an additional reducing agent like e.g. methane.

Metal cluster catalysis. 2. Selective reduction of nitrobenzene catalyzed by rhodium carbonyl cluster anions. Evidence for water gas shift reaction

Abstract The rhodium cluster complex, Rh6(CO)16, has been found to catalyze the homogeneous reduction of nitrobenzene to aniline at temperatures above 80 °C in the presence of N,N-dimenthylbenzylamine, using any one of the following reducing gases: (1) H2/CO, (2) H2, (3)CO/H2O. The reductions are highly selective and aniline was the only product detected. The same result was obtained using Amberlyst A-21 resin beads which contained polymerbound N,N-dimethylbenzylamine moieties which, in turn, immobilize the rhodium clusters. It was shown, by using D2O, and following deuterium incorporation into the resulting aniline, that the water is the source of hydrogen when CO/H2O was used. When nitrobenzene is absent, this catalyst system promotes the water—gas shift reaction. Unlike aromatic nitro groups, aliphatic nitro groups were not reduced. However, the water—gas shift reaction was catalyzed. The kinetics of aniline formation were first order in nitrobenzene and the effect of pressure on the reaction is described. Use of the resin catalyst led to lower rates and a remarkably air sensitive catalyst system relative to the homogeneous reactions.

Selective Reduction of Nitrobenzene by Sodium Borohydride in the presence of Co (III) Complexes

The reduction of nitrobenzene by NaBH4 in the presence of various Co (III) complexes was investigated at 25°C in aqueous solution in nitrogen atmosphere. A nearly equimolar mixture of aniline and azoxybenzene was obtained from nitrobenzene in the presence, of Co(NH3)63+ salts, except nitrate, and chloroammine Co (III) complexes. Upon the substitution of a portion of NH3 ligands of Co(NH3)63+ by NO2- or CN-, the product varied to aniline for [Co(NO2)3 (NH2)6-x](3-x)+ and to azoxybenzene for [Co(CN)x(NH3)6-x] (3-X)+. No reaction occurred, however, when completely substituted Co (NO2)63+ or Co (CN)63- was used. The main product was azoxybenzene in the case of Co(III) ethylenediamine complexes.