Location: RER - Europe
The process “chloronitrobenzene, at plant, RER” is modelled for the production of chloronitrobenzene from chlorobenzene in Europe. Raw materials are modelled with a stoechiometric calculation. Emissions are estimated. Energy consumptions, infrastructure and transports are calculated with standard values.
o-Chloronitrobenzene (C6H4ClNO2; CAS 88-73-3, OCNB) crystallizes as light yellow monoclinic needles. The compound is very soluble in ether, benzene, or hot ethanol, but insoluble in water. Nitration of chlorobenzene with mixed acid typically gives an isomer mix in 98 % yield consisting of 34 – 36 % 2- chloronitrobenzene, 63 – 65 % 4- chloronitrobenzene, and only ca. 1 % 3- chloronitrobenzene. The ortho – para ratio of about 0.55 is in sharp contrast to the 1.6 obtained with nitrotoluene isomers. As with the nitration of toluene, much work has been done on isomer control so that the producer might have some flexibility towards the balance of isomer demand. Although no major change in ratio has been achieved, the situation is better for nitrochlorobenzene than nitrotoluenes, because the favored isomer is in much greater demand. In further contrast to the nitration of toluene, the nitration of chlorobenzene in the presence of phosphoric acid decreases the proportion of 4- chloronitrobenzene, and the use of phosphoric acid in the presence of a transition-metal catalyst is said to increase the ortho – para ratio to ca. 0.8.
Even though the rate of nitration of chlorobenzene is an order of magnitude slower than that of benzene, comparable temperatures (40 –70 °C) are adequate, and the techniques and equipment are very similar to those described for benzene. In Meissner units the slower reaction rate is compensated by placing additional reactors in series, thereby facilitating flexible operation of this plant type as a basis for multipurpose installations.
The mixed product output stream is the same whether produced by a batch or continuous process, and the isomers are separated by a combination of fractional crystallization and distillation. For a simple first separation the isomer mixture is held at a temperature slightly above its crystallization point (15 °C), whereby much of the 4- chloronitrobenzene crystallizes and can be separated. Fractional distillation gives a para-rich distillate containing all the meta isomer and an ortho-rich still residue. Each of these is crystallized, separated, and the liquid component is refractionated to gradually accumulate high-purity ortho and para products, together with intermediate fractions for continual recycle. at a temperature slightly above its crystallization point (15 °C), whereby much of the 4- chloronitrobenzene crystallizes and can be separated. Fractional distillation gives a para-rich distillate containing all the meta isomer and an ortho-rich still residue. Each of these is crystallized, separated, and the liquid component is refractionated to gradually accumulate high-purity ortho and para products, together with intermediate fractions for continual recycle.

2-Chloronitrobenzene derivatives find many outlets in the synthesis of colorants and effect chemicals. Reduction with iron produces 2-chloroaniline, and electrolytic reduction followed by rearrangement of the resulting hydrazo derivative leads to 3,3′-dichlorobenzidine, both of which are important diazo components. In the alternative, more economical hydrogenation process, a modified catalyst is required to inhibit dechlorination as a side reaction. Typically, a platinum on carbon catalyst, together with a small quantity of an inorganic acid acceptor such as magnesium oxide, is used; however, up to 2 % aniline may still be formed. The alternative use of morpholine as a dechlorination suppressor, rather than just an acid acceptor, is recommended for 2- and 4- chloronitrobenzene, this reduces the extent of dechlorination to 0.5 %. The use of modified catalyst systems based on platinum, rather than the conventional nickel catalyst used in the production of most aniline derivatives, is essential for hydrogenation of all nitrohalo aromatics.
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Gerald Booth: Nitro Compounds, Aromatic. Published online: 2000. In: Ullmann's Encyclopedia of Industrial Chemistry, Seventh Edition, 2004 Electronic Release (ed. Fiedler E., Grossmann G., Kersebohm D., Weiss G. and Witte C.). 7 th Electronic Release Edition. Wiley InterScience, New York, Online-Version under: DOI: 10.1002/14356007.a17_411

Undefined unit processes (UPRs) are the unlinked, multi-product activity datasets that form the basis for all of the system models available in the ecoinvent database. This is the way the datasets are obtained and entered into the database by the data providers. These activity datasets are useful for investigating the environmental impacts of a specific activity (gate-to-gate), without regard to its upstream or downstream impacts.