Reductions nitrobenzene

Deactivated catalyst is carefully regenerated in a mixture of air and steam at 300-400°C. Hydrocarbons are purged from the system and the catalyst rereduced with hydrogen in steam before it is reused. 

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Pardey and coworkers—Rh, Cu, and Ir complexes heterogenization and applications of water-gas shift (e.g., nitrobenzene reduction, hydroformylation). 

The water-gas shift rates are obviously much lower when heterogenized in comparison with the Rh complexes in homogeneous solutions of the amines (also see Tables 30-33). Kinetics for nitrobenzene reduction were performed for the cis-[Rh(CO)2(2-picoline)2]PF6 catalyst, and reported in 2000. Kinetics displayed a first order dependence on Pco over the range 0-1.9 atm in the temperature range 80-120 °C. As with the kinetics previously reported by Lima Neto and coworkers,121 it was suggested that the CO addition preceded the rate limiting step. A non-linear dependence on the rate versus Rh concentration, as with the previous study, suggested participation by both mononuclear and polynuclear species. 

Pardey and coworkers159,161 also reported results for water-gas shift and nitrobenzene reduction for the related Rh complex, [Rh(COD)(amine)2](PF6), where COD = 1,5-cyclooctadiene, immobilized on P(4-VP), and results are reported in... 

Table 38 Nitrobenzene reduction rates for [Rh(COD)(amine)2]PF6 P(4-VP)161 heterogenized on...

Table 40 Nitrobenzene reduction rates for rhodium pyrazolate complexes in different solvents160 ...

Nitrobenzene oxidation was carried out by adding 50 mg of dry soda lignin into a mixture of 7 mL of 2 M NaOH and 4 ttiL of nitrobenzene in a 15 ttiL steel autoclave. Then, the antoclave was heated to 165°C for 3 hours in a preheated thermostat oil bath. After the autoclave was cooled to room temperature, the mixture was then transferred to a liqnid-hquid extractor for continuous extraction with chloroform (5 x 20 mL) in order to remove any nitrobenzene reduction product and excess nitrobenzene. The oxidation mixtnre was then acidified by concentrated HCl to pH 3 and further extracted with chloroform (5x15 mL). The solvent from the second chloroform solution was then removed using a rotary evaporator at 40°C under reduced pressure in order to obtain the nitrobenzene oxidation mixture. The mixture was then dissolved into dicloromethane and made up to 10 luL. This mixture was then used as a stock solution for high performance liquid chromatography (HPLC) analysis [6]. 

With nitrobenzene, reduction to an intermediate stage results in the formation of a complex which, as is also the case with the initial complexes formed with ferricyanide, benzoquinone, and benzaldehyde, cannot react in the manner shown in the first conclusion. These species require the presence of added alkali, which apparently effects the displacement of reduced substrate by hydroxyl anion to yield hydroxypentacyanocobaltate(III). All of the substrates mentioned have been found to undergo catalytic hydrogenation when added to the catalyst system in less than stoichiometric quantities in the presence of alkali. 

Nikitas, isotherms, 936, 952, 1195 Nitrobenzene reduction, 1376 Nonaqueous solutions, coadsorption of hydrogen and organic molecules, 13-10 see also hydrogen coadsorption Non -faradaic electrochemical modification of catalytic activity, 1371 Nonlocalized adsorption, 928, 958 Nonpolarizable interfaces, 812, 857, 1055, 1060, 1111... 

Magnesium oxide exhibited high activity and high selectivity in the hydrogen transfer from alcohols to studied nitroarenes. Because of the limited space of the paper the complete amine yield - temperature dependence was shown only for nitrobenzene reduction (Table 1). However, also for other reactants the yield of the aminic product increased continously between the values obtained at the lowest (350°C) and the highest (450°C) reaction temperatures. Below 350°C the complete lack of activity of MgO in the studied transformation was noted. The same was observed by us earlier (ref. 2) in the case the catalytic transfer reduction of other functional groups. 

The catalyst decay during nitrobenzene reduction was studied in long-time experiments. The gradual poisoning of the catalyst was observed (Table 5) which led in 4-5 hrs to the significant diminishing of reactant conversion. 

The decrease of aniline yields (mole 8 ) during nitrobenzene reduction with various alcohols, temperature - 450°C, donor acceptor ratio-3, HLSV-l... 

Nitroaromatic compounds (NACs) are one of the widespread contaminants in the environments. Sources of NACs are numerous they originate from insecticides, herbicides, explosives, pharmaceuticals, feedstock, and chemicals for dyes (Agrawal and Tratnyek, 1996). Under anaerobic conditions, the dominant action is nitro reduction by zero-valent iron to the amine. Other pathways do exist, such as the formation of azo and azoxy compounds, which is followed by the reduction of azo compounds to form amines. Also, in addition to the possibility of azo and azoxy compounds, phenylhydrox-ylamine may be an additional intermediate (Agrawal and Tratnyek, 1996). Nitrobenzene reduction forms the amine aniline. Known for its corrosion inhibition properties, aniline cannot be further reduced by iron. Additionally, it interferes with the mass transport of the contaminant to the surface of the iron. The overall reaction is as follows ... 

Grignard additions, 9, 59, 9, 64 indium-mediated allylation, 9, 687 in nickel complexes, 8, 150 ruthenium carbonyl reactions, 7, 142 ruthenium half-sandwiches, 6, 478 and selenium electrophiles, 9, W11 4( > 2 in vanadocene reactions, 5, 39 Nitrites, with trinuclear Os clusters, 6, 733 Nitroalkenes, Grignard additions, 9, 59-60 Nitroarenes, and Grignard reactivity, 9, 70 Nitrobenzenes, reductive aminocarbonylation, 11, 543... 

Scherer MM, Johnson K, Westall JC, Tratnyek PG. Mass transport effects on the kinetics of nitrobenzene reduction by iron metal. Environ Sci Technol 2001 35 2804-2811. 

The aniline processes that are currently in use include (1) hydrogenation of nitrobenzene, (2) nitrobenzene reduction with iron filings, and (3)... 

Nitrobenzene Reduction with Iron Filings. The older Bechamp method for iron oxide pigment production gives aniline as a coproduct and is operated by Bayer in West Virginia. Nitrobenzene is reduced by reaction with iron filings in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous or ferric state and the coproduct aniline is separated. The yield is 90 to 95 percent of theoretical. The reactions are represented as follows.138... 

About 70% of all iron oxide pigments are produced synthetically. Copperas or ferrous sulfate heptahydrate (FeS04-7H20) is the primary source of iron. It is a byproduct of the sulfate process for the manufacture of titanium dioxide as well as a by-product of pickling operations in the steel industry. Other sources of iron include ferric sulfate, ferrous chloride, ferric chloride, and the iron oxide slurry from the production of aniline by nitrobenzene reduction. 

Weigh accurately about 200 mg of a dned, extracted wood meal (40-60 mesh) with known moisture and extractives contents or 50 mg of a dned, purified lignin preparation The specimen, 7ml of 2M NaOH, and 0 4ml of freshly distilled nitrobenzene are placed m a 10-ml stainless steel bomb (Note 1) The bomb is sealed tightly with a screw cap fitted with a Teflon gasket and heated at 170°C for 2 5h m an electrically preheated (170°C), thermostated aluminum block with six holes to accommodate the cylindrically shaped bombs or in a thermostated oil bath The bomb is shaken occasionally and, after the heating period, is removed from the heater and cooled with ice water The oxidation mixture is transferred to a liquid-liquid extractor, and extracted continuously with CHCI, for 4h to remove nitrobenzene reduction products and any excess nitrobenzene The oxidation mixture is acidified to pH 3-4 with cone HC1, and further extracted continuously with CHCI, for 48 h The solvent from the second CHCI, solution is removed at 40°C under reduced pressure to obtain the nitrobenzene oxidation mixture The mixture is then dissolved m 5 ml of CH2C12 and transferred to a 10-ml volumetric flask The solution is made up to 10 ml... 

In the context of the present discussion, it is worth noting that virtually all the experimental systems that exhibit such "anomalous temperature-dependent transfer coefficients are multistep inner-sphere processes, such as proton and oxygen reduction in aqueous media [84]. It is therefore extremely difficult to extract the theoretically relevant "true transfer coefficient for the electron-transfer step, ocet [eqn. (6)], from the observed value [eqn. (2)] besides a knowledge of the reaction mechanism, this requires information on the potential-dependent work terms for the precursor and successor state [eqn. (7b)]. Therefore the observed behavior may be accountable partly in terms of work terms that have large potential-dependent entropic components. Examinations of temperature-dependent transfer coefficients for one-electron outer-sphere reactions are unfortunately quite limited. However, most systems examined (transition-metal redox couples [2c], some post-transition metal reductions [85], and nitrobenzene reduction in non-aqueous media [86]) yield essentially temperature-independent transfer coefficients, and hence potential-independent AS orr values, within the uncertainty of the double-layer corrections. 

Mechanism Mechanism of nitrobenzene reduction to aniline is shown in Scheme 6.36. 

Another interesting example of formation of aminyloxides is the thermal decomposition of benzoylperoxide in benzene in presence of nitrobenzene. Reduction of nitrobenzene to nitrosobenzene to some extent and subsequent spin-trapping of phenyl radical gives diphenylaminyloxide83. ... 

Therefore, we have to adapt the complete reaction scheme of nitrobenzene reduction for nitroaliphatic compounds hydrogenation and to consider both coupling reactions and TBHA disproportionation. 

The general principles of modeling a vapor-phase reaction on a solid catalyst in a fixed-bed reactor are illustrated by applying them to the specific case of nitrobenzene reduction to aniline. Several models of varying complexity are discussed. 

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