Iron, aniline production with

Aniline can also be made by two other methods. In the first, nitrobenzene is reduced by reaction with scrap iron in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous state, and the coproduct aniline is separated. This route accounts for less than 5 percent of the current aniline production. The other process avoids nitrobenzene entirely and involves the vapor-phase ammonolysis of phenol, using an alumina catalyst. Aniline is formed with dipheny-lamine as a by-product. About 20 percent of the aniline is produced by this route. 

Nicholson, developed processes for the successful bulk production of nitrobenzene and aniline in batteries of closed iron reactors fitted with power-driven stirrers (Figure 6). For aniline, Nicholson adopted the B6champ reduction process and introduced steam into the reaction mixture by employing a hollow stirrer tube. The product aniline was obtained by distilling with steam after the addition of lime. Within a few years the standard reduction mixture became iron filings and hydrochloric acid. Production improvements and better quality benzene enabled aniline to be obtained in 90-95% yield. 

This older technique, which uses a mixture of iron filings and hydrochloric add to reduce nitrobenzene to aniline, is employed today only to produce iron oxide pigments, with aniline produced as a by-product... 

It is economically advantageous to conduct the manufacture of aniline from chlorobenzene in conjunction with the large-scale production of chlorine and chlorinated products, to permit the introduction of cheap chlorobenzene into the aniline plant. With such a setup, this process competes favorably with the older method involving the iron-acid reduction of nitrobenzene. 

The classical method for preparing hydroquinone is based on the oxidation of aniline with manganese dioxide or sodium dichromate in sulfuric acid. The qui-none which is obtained as an intermediate is reduced to hydroquinone with iron filings in dilute hydrochloric acid. This process, which is still used e.g. in India and China, is characterized by the simultaneous production of large amounts of manganese or chromium and iron salts, together with ammonium sulfate. For this reason, oxidative cleavage of p-diisopropylbenzene similarly to phenol synthesis was developed for the production of hydroquinone. 

As an example, the commercial preparation of aniline may be described. Nitrobenzene is reduced by finely divided iron and water with a little hydrochloric acid, the products formed being ferrous chloride, magnetic oxide of iron and aniline. The aniline is distilled over with steam and the greater part of it separates from the distillate on standing. The aqueous layer, which contains a little aniline, is afterwards placed in the boiler which supplies steam to the still, so that in the next distillation the aniline is carried over into the still again. 

Anilines react with T -cyclohexa-l,3-dienyliumiron complexes in acetonitrile under reflux to form 5-(2-anilino)-substituted (cyclohexa-l,3-diene)iron complexes. At room temperature, the kinetic N-alkylated product is formed. Upon heating at reflux, it rearranges to the thermodynamically more stable C-alkylation product (electrophilic aromatic substitution) in the presence of anilinium tetrafluoroborate that is formed in the course of the reaction fiom excess aniline. The 5-(2-anilino)-substituted (cyclohexa-1,3-diene)iron complexes undergo oxidative cyclization in the presence of various oxidizing agents followed by concomitant aromatization and demetalation to afford carbazoles (Scheme 4-167). Inunediate consecutive oxidative cyclization after... 

In the reduction of nitro compounds to amines, several of the iatermediate species are stable and under the right conditions, it is possible to stop the reduction at these iatermediate stages and isolate the products (see Figure 1, where R = CgH ). Nitrosoben2ene [586-96-9] C H NO, can be obtained by electrochemical reduction of nitrobenzene [98-95-3]. Phenylhydroxylamine, C H NHOH, is obtained when nitrobenzene reacts with ziac dust and calcium chloride ia an alcohoHc solution. When a similar reaction is carried out with iron or ziac ia an acidic solution, aniline is the reduction product. Hydrazobenzene [122-66-7] formed when nitrobenzene reacts with ziac dust ia an alkaline solution. Azoxybenzene [495-48-7], C22H2QN2O, is... 

Benzanthrone has been prepared by three general methods, the first of which is generally regarded as the best (i) by heating a reduction product of anthraquinone with sulfuric acid and glycerol,1 or with a derivative of glycerol, or with acrolein. The anthraquinone is usually reduced in sulfuric acid solution, just prior to the reaction, by means of aniline sulfate, iron, , or copper. It has also been prepared (2) by the action of aluminum or ferric chloride on phenyl-a-naphthyl ketone, and (3) from i-phenylnaphthalene-2-carboxylic acid. ... 

This reduction step can be readily observed at a mercury electrode in an aprotic solvent or even in aqueous medium at an electrode covered with a suitable surfactant. However, in the absence of a surface-active substance, nitrobenzene is reduced in aqueous media in a four-electron wave, as the first step (Eq. 5.9.3) is followed by fast electrochemical and chemical reactions yielding phenylhydroxylamine. At even more negative potentials phenylhydroxylamine is further reduced to aniline. The same process occurs at lead and zinc electrodes, where phenylhydroxylamine can even be oxidized to yield nitrobenzene again. At electrodes such as platinum, nickel or iron, where chemisorption bonds can be formed with the products of the... 

A few triphenylmethane dyes are still obtained by empirical methods first used in the early processes of dye manufacture. For example, in the production of magenta (Cl Basic Violet 14), a mixture of aniline, toluidines and nitrotoluenes is heated with zinc and iron(II)... 

The iron salts of the dimethyl ester of acetylhematoporphyrin and of the tetramethylhematoporphyrin yield verdoparahematin when treated with fermenting yeast under anaerobic conditions. The reduction product has been isolated by Stier as a double compound with pyridine. Mention may also be made of the reduction of hydroxyhemoglobin by means of yeast, which has been investigated more closely by Neumann. A few acid and basic dyestuffs are very slowly cleaved by reduction with fermenting yeast. In the case of p-aminoazobenzene, p-dimethylamino-azobenzene and 2,4-diaminoazobenzene, aniline has been claimed as the... 

This process is used principally in Europe. It was first developed in 1854 for the production of aniline. Nitrobenzene was reduced to aniline using metallic iron, hence the process was termed the aniline or nitrobenzene process. Iron oxides were formed as unusable, grey/black products. Around 1925, Laux found that addition of iron chloride modified the process so that iron oxides suitable for use as pigments could be produced. With this additive alone, magnetite with a high tinting strength results, i. e. 

The Badische AniKn- und Soda-Fabrik prepared a nitride of undetermined composition by heating a mixture of silica and carbon in an atm. of nitrogen. The reaction proceeds at a relatively low temp, if a hydroxide or salt of a metal be added. The product contains silicon nitride mixed with the nitride of the metal. The Badische Anilin- und Soda-Fabrik also removed many of the impurities—iron, carbon, silicates, carbides, silicides, and phosphides—by treatment with acids or mild oxidizing agents which do not affect the silicon nitride. A. S. Larsen and O. J. Storm prepared the nitride by the action of nitrogen on molten silicides—e.g. ferrosilicon. 

Nitrate accumulation may occur in plants growing on soil fertilized with nitrate under moisture-deficient conditions. In the stomachs of ruminant animals, nitrate (NOj) ingested with plant material is reduced to nitrite (N02). The nitrite product enters the bloodstream and oxidizes the iron(II) in hemoglobin to iron(III). The condition that results is methemoglobinemia, which was discussed in Section 15.3 in connection with aniline poisoning. 

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