Nitrobenzene production

Between 1996 and 2001, the nitrobenzene sales price varied from US 0.30 per pound to US 0.35 per pound263. 

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Another concentration method involves passing an inert gas such as N2 or CO2 through the reaction medium (12). As the gas passes through, it becomes humidified and carries captured water with it. Most of the energy required for the gas humidification comes from the heat of reaction. An advantage is that expensive drying equipment is not needed. Also, the sulfuric acid mist formed in typical concentrators is minimized. Du Pont uses a similar process in its nitrobenzene production faciUty. 

Economic Aspects. The two main areas affecting the economic aspects for nitrobenzene production are process related costs, including raw ... 

This process may be carried out by a batch or a continuous process. The continuous process is more effective for large plants. Both processes wash the crude nitrobenzene with water. The crude nitrobenzene is fed to a distillation system to separate the water, benzene and dinitrobenzene. This process requires reactor cooling and a system for sulfuric acid reconcentration. Yields by the continuous process are 95% to 96% of theoretical. Bayer used this process in the United States until it discontinued nitrobenzene production in 1994258. ... 

Nitrobenzene (Aniline). The U.S. nitrobenzene production was about 2 billion lb in 1999. Two types of manufacturing processes were used the direct nitration and the adiabatic nitration process. In the direct nitration system, benzene is mixed with a mixture of nitric/ sulfuric acid. The reaction can be carried out in either a batch or a continuous system. Those reactors require a cooling system to keep it at constant temperature. It also requires a separate system for sulfuric acid reconcentration. In the adiabatic process, water is flashed off under vacuum before the sulfuric acid/nitrobenzene separation. The advantage of the adiabatic process is to eliminate a separated sulfuric acid reconcentration unit. This also will provide a better heat integration. Recently, the disposal of nitrophenols has become a major issue for aniline manufacture. Small amounts of nitrophenols are always made during the benzene... 

The hydrogen sulphite anion acts as a base to help remove the proton so as to re-form the aromatic ring to result in the nitrobenzene product. 

There has been a gradual increase in nitrobenzene production volume in the United States from 73,600 metric tons (kkg) in 1960 to 434,900 kkg in 1986. Based on increased production capacity and increased production of aniline (the major end-product of nitrobenzene) in 1987, it is likely that nitrobenzene production volume will continue to increase (Collins et al. 1982 Dunlap 1981 EPA 1985a SRI 1985, 1986, 1987, 1988 USITC 1987, 1988). 

The primary use of nitrobenzene is in the captive production of aniline, with about 97.5% of nitrobenzene production consumed in this process. The major use of aniline is in the manufacture of polyurethanes. Nitrobenzene is also used as a solvent in petroleum refining, in the manufacture of cellulose ethers and acetate, and in Friedel-Crafts reactions to hold the catalyst in solution. It is also used in the synthesis of other organic compounds including acetaminophen, which is an over-the-counter analgesic commonly known as Tylenol . 

Production, Use, Release and Disposal. Available data indicate that most nitrobenzene produced in the United States is consumed in the production of aniline, but current quantitative data on the amount of nitrobenzene released to the environment during nitrobenzene production and use are sparse. Collection of this information would be helpful in evaluating the effect of current industrial practices on environmental levels of nitrobenzene. 

Nitrobenzene production using nitric acid and sulfuric acid... 

Occurs in the high-boiling fraction of coal tar. Most conveniently prepared by Skraup s reaction by healing a mixture of aniline, glycerol, sulphuric acid and nitrobenzene. Used in the manufacture of dyestuffs, and pharmaceutical products. 

Add 23 g. of powdered (or flake ) sodium hydroxide to a solution of 15 ml. (18 g.) of nitrobenzene in 120 ml. of methanol contained in a 250 ml. short-necked bolt-head flask. Fix a reflux water-condenser to the flask and boil the solution on a water-bath for 3 hours, shaking the product vigorously at intervals to ensure thorough mixing. Then fit a bent delivery-tube to the flask, and reverse the condenser for distillation, as in Fig. 59, p. 100, or Fig. 23(D), p. 45). Place the flask in the boiling water-bath (since methanol will not readily distil when heated on a water-bath) and distil off as much methanol as possible. Then pour the residual product with stirring into about 250 ml. of cold water wash out the flask with water, and then acidify the mixture with hydrochloric acid. The crude azoxybenzene separates as a heavy oil, which when thoroughly stirred soon solidifies, particularly if the mixture is cooled in ice-water. 

Nitrobenzene. Nitrobenzene, of analytical reagent quality, is satisfactory for most purposes. The technical product may contain dinitrobenzene and other impurities, whilst the recovered solvent may be contaminated with aniline. Most of the impurities may be removed by steam distillation after the addition of dilute sulphuric acid the nitrobenzene in the distillate is separated, dried with calcium chloride and distilled. The pure substance has b.p. 210°/760 mm. and m.p. 5 -7°. 

A brief account of aromatic substitution may be usefully given here as it will assist the student in predicting the orientation of disubstituted benzene derivatives produced in the different substitution reactions. For the nitration of nitrobenzene the substance must be heated with a mixture of fuming nitric acid and concentrated sulphuric acid the product is largely ni-dinitrobenzene (about 90 per cent.), accompanied by a little o-dinitrobenzene (about 5 per cent.) which is eliminated in the recrystallisation process. On the other hand phenol can be easily nitrated with dilute nitric acid to yield a mixture of ortho and para nitrophenols. It may be said, therefore, that orientation is meta with the... 

If the presence of unreduced nitrobenzene is suspected (odour and/or high b.p. residue), treat all the product with excess of dilute hydrochloric acid and remove the nitrobenzene either by steam distillation or by ether extraction render the residue alkaline with sodium hydroxide solution and isolate the aniline os before. 

The commercial product, m.p. 53-55°, may be used. Alternatively the methyl -naphthyl ketone may be prepared from naphthalene as described in Section IV,136. The Friedel - Crafts reaction in nitrobenzene solution yields about 90 per cent, of the p-ketone and 10 per cent, of the a-ketone in carbon disulphide solution at — 15°, the proportions ore 65 per cent, of the a- and 35 per cent, of the p-isomer. With chlorobenzene ns the reaction medium, a high proportion of the a-ketone is also formed. Separation of the liquid a-isomer from the solid p-isomer in Such mixtures (which remain liquid at the ordinary temp>erature) is readily effected through the picrates the picrate of the liquid a-aceto compound is less soluble and the higher melting. 

Reductive carbonylation of nitro compounds is catalyzed by various Pd catalysts. Phenyl isocyanate (93) is produced by the PdCl2-catalyzed reductive carbonylation (deoxygenation) of nitrobenzene with CO, probably via nitrene formation. Extensive studies have been carried out to develop the phosgene-free commercial process for phenyl isocyanate production from nitroben-zene[76]. Effects of various additives such as phenanthroline have been stu-died[77-79]. The co-catalysts of montmorillonite-bipyridylpalladium acetate and Ru3(CO) 2 are used for the reductive carbonylation oLnitroarenes[80,81]. Extensive studies on the reaction in alcohol to form the A -phenylurethane 94 have also been carried out[82-87]. Reaction of nitrobenzene with CO in the presence of aniline affords diphenylurea (95)[88]. 

Reaction of 1 2 3 tribromo 5 nitrobenzene with sodium ethox in ethanol gave a single product CsHyBrjNOs m quantitative yield Suggest... 

Pentafluoro 6 nitrobenzene reacts readily with sodium methoxide m methanol at room temperature to yield two major products each having the molecular formula C7H3F4NO3 Suggest reasonable structures for these two compounds... 

Mixtures of HNO, H2SO4, and SO also result in high concentrations of NO/, and toluene can be readily nitrated at —40 to — 10°C as a result (6). At these low temperatures, the formation of the meta-isomer of mononitrotoluene (MNT) is greatiy reduced. Such a reduction is highly desired in the production both of dinitrotoluenes (DNTs) employed to produce intermediates for polyurethane production and of trinitrotoluene (TNT), which is a high explosive. > -MNT results in the production of undesired DNT and TNT isomers (see Nitrobenzene and nitrotoluenes). 

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. 

Fig. 1. Reduction products of nitrobenzene (1) nitrosobenzene [98-95-3] (2) /V-pbenylbydroxyl amine [100-65-2] (3) aniline [62-53-3] (4) azoxybenzene...

In the last few years several modifications to the traditional mixed acid nitration procedure have been reported. An adiabatic nitration process was developed for the production of nitrobenzene (9). This method eliminated the need to remove the heat of reaction by excessive cooling. The excess heat can be used in the sulfuric acid reconcentration step. An additional advantage of this method is the reduction in reaction times to 0.5—7.5 minutes. 

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