Bechamp process

The reduction of the nitro group to yield aniline is the most commercially important reaction of nitrobenzene. Usually the reaction is carried out by the catalytic hydrogenation of nitrobenzene, either in the gas phase or in solution, or by using iron borings and dilute hydrochloric acid (the Bechamp process). Depending on the conditions, the reduction of nitrobenzene can lead to a variety of products. The series of reduction products is shown in Figure 1 (see Amines byreduction). Nitrosobenzene, /V-pbenylbydroxylamine, and aniline are primary reduction products. Azoxybenzene is formed by the condensation of nitrosobenzene and /V-pbenylbydroxylamine in alkaline solutions, and azoxybenzene can be reduced to form azobenzene and hydrazobenzene. The reduction products of nitrobenzene under various conditions ate given in Table 2. 

C6H5N02 + 9Fe + 4H20 = 4C6H5NH2 + 3Fe304 Invented in 1926 by J. Laux at Bayer and used commercially thereafter. It was an improvement on the Bechamp process. 

Anhydrous sodium tungstate, 25 382 Anhydrous stannic chloride, 24 803 Anhydrous stannous chloride, 24 802-803 Anhydrous zinc chloride, 26 617 Anhydrous zinc sulfate, 26 617 Aniline, 2 783-809, 17 250, 259 alkylation, 2 197 Bechamp process, 2 490 from benzene, 3 619t, 620 chemical reactions, 2 783-789 derivatives, 2 783-809 economic aspects, 2 790-791... 

Laux Process. This is a modification of the Bechamp process for the iron reduction of nitrobenzene to aniline which leaves iron oxide as the residue. Incorporation of iron or aluminium chlorides into the reduction process produces high quality yellow and red iron oxide pigments... 

Bechamp batch process Bechamp reaction Beck and Guthke cell Becke line technique... 

The Faux process is a modification of the Bechamp reaction that was discovered in 1854. It has been used for the reduction of nitrobenzene to aniline using metallic iron ... 

The old Bechamp batch process for reduction of nitroben2ene (iron-hydrochloric acid) is obsolete however, Mobay Chemical Corporation is operating a plant using this process for production of pigment grade iron oxide as weU as aniline. 

Bechamp A process for reducing organic nitro-compounds to amines, using iron, ferrous salts, and acetic acid. Invented by A. J. Bechamp in 1854 and still used for making certain aromatic amines. 

The process of reduction of nitrocompds was discovered in 1842 by N,Zinin, a prof at the Univ of Kazan, Russia. He prepd aniline by reducing nitrobenzene with (NH )2S. A less expensive reducing agent, Fe and dil acid, was proposed in 1854 by Bechamp. The reduction process by Fe and acid was used on a large scale by Perkin. With cheap aniline the synthetic dyestuff industry was born... 

The problem of how to stabilize nitrostarch has been solved by different means, but the majority of stabilization processes remain obscure as patent secrets. None the less, from certain observation some general conclusions can be made. It was early observed by Bechamp [13] that nitrostarch obtained by nitration in nitric acid alone is more stable than one obtained by means of nitric acid mixed with sulphuric acid. This has been confirmed experimentally by Hackel and T. Urbanski [18], and seems likely to be explained by the formation of starch sulphates or mixed nitric and sulphuric esters of starch. 

The next most useful process is that of Bechamp,2 which involves the direct arsonation of phenols, aromatic amines, and certain of their derivatives by heating with arsenic add. 

For the reduction of nitroarenes to aminoarenes by the catalytic hydrazine H-transfer reduction method, the classical hydrogenation catalysts Ni, Pd and Pt are most commonly used [1] [2]. In a more extended study [3] we were able to confirm previously reported observations [4] that these reductions can also be catalysed by modified iron oxides hydroxides. This method for the production of many aromatic amines offers several advantages compared to the conventional processes still employed in industry, such as the environmentally imfavourable Bechamp [5] and Zinin reductions [6]. It is an outstanding feature of the novel reduction method presented here that further reducible substituents in nitroazo compounds, such as... 

Explanations of the mechanism of iron and acid (Bechamp) reductions can be made on the basis of observed chemical phenomena as well as electronic theory. Both explanations are useful in providing a better understanding of the reduction process and in providing guides for efficient industrial operations. 

The original process was the Bechamp method for manufacturing iron oxide pigment in which aniline is produced as a by-product. It is still used to a limited extent. Nitrobenzene is reduced by reaction with iron fillings in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous or ferric state and by-product aniline is recovered. The chemistry is illustrated in Eqs. (2) and (3) ... 

It is better to prevent waste generation than to treat or clean up waste after it has been created. The earlier messy Bechamp reductions using Fe-HCl and generating a highly acidic waste sludge are replaced by clean catalytic processes using suitably designed multiphase reactors (Section 1.3 and Chapters 7A and 8). 

Catalytic processes are superior to processes that use stoichiometric reagents (Bechamp reduction cited earlier). There is a continuous improvement in catalysts. Many acid-catalyzed reactions (esterifications, hydrations, alkylations) have been replaced by benign ion exchange resins in the H form (Wasker and Pangarkar 1992, 1993). The newer catalysts are not only more selective but also more active in enhancing reaction rates. In some cases, for instance, replacement of mineral acids by ion exchangers allows the use of low-cost material of construction and facile separation/recycle of the catalyst while simultaneously eliminating ultimate neutralization of the product by a base. 

The first satisfactory experimental proof that alcoholic fermentation is caused by a non-organised ferment (enzyme) in yeast was given by Buchner, who adopted for it Bechamp s name zymase. Buchner found that if the yeast cells are crushed by trituration with sand and kieselguhr and the paste is pressed in a cloth bag, a liquid free from yeast cells is obtained which produces alcoholic fermentation. The activity is not destroyed by evaporation to dryness at 30 -35° or precipitation by alcohol. Arthur Harden and others showed that a co-enzyme, separable from yeast-juice by dialysis, and an inorganic phosphate, are also involved in alcoholic fermentation, the process being apparently very complicated. 

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