Monochlorobenzene

Continuous chlorination of benzene at 30—50°C in the presence of a Lewis acid typically yields 85% monochlorobenzene. Temperatures in the range of 150—190°C favor production of the dichlorobenzene products. The para isomer is produced in a ratio of 2—3 to 1 of the ortho isomer. Other methods of aromatic ring chlorination include use of a mixture of hydrogen chloride and air in the presence of a copper—salt catalyst, or sulfuryl chloride in the presence of aluminum chloride at ambient temperatures. Free-radical chlorination of toluene successively yields benzyl chloride, benzal chloride, and benzotrichloride. Related chlorination agents include sulfuryl chloride, tert-huty hypochlorite, and /V-ch1orosuccinimide which yield benzyl chloride under the influence of light, heat, or radical initiators. 

With the discontinuation of some herbicides, eg, 2,4,5-trichlorophenol [39399-44-5] based on the higher chlorinated benzenes, and DDT, based on monochlorobenzene, both for ecological reasons, the production of chlorinated benzenes has been reduced to just three with large-volume appHcations of (mono)chlorobenzene, o-dichlorobenzene, and -dichlorobenzene. Monochlorobenzene remains a large-volume product, considerably larger than the other chlorobenzenes, in spite of the reduction demanded by the discontinuation of DDT. 

Nitration of chlorobenzenes, mosdy monochlorobenzene in the United States, with nitric acid has wide industrial appHcations. 

Nitrated monochlorobenzene is used as a building block to produce many other products. There is also some commercial nitration of o-dichlorobenzene in the United States and Western Europe. 

Chlorobenzenes are generally considered nonflammable materials with the exception of monochlorobenzene, which has a flash point of 34.5°C and is a flammable solvent based on DOT standards. 

The chlorobenzene operations in the United States were developed primarily for the manufacture of phenol, aniline, and DDT. However, with the process changes in the production of phenol and aniline, the phase-out of DDT production, and changes in the herbicide and solvent markets, the U.S. production of chlorinated benzenes has shmnk by more than 50% since the total production peaked in 1969. U.S. production of monochlorobenzene peaked in the 1960s and decreased to a low of 101 million kg in 1986 with an 11% and 9% increase, respectively, in 1988 and 1989. 

Commercial chlorination of benzene today is carried out as a three-product process (monochlorobenzene and 0- and -dichlorobenzenes). The most economical operation is achieved with a typical product spHt of about 85% monochlorobenzene and a minimum of 15% dichlorobenzenes. Typically, about two parts of -dichlorobenzene are formed for each part of (9-isomer. It is not economical to eliminate the coproduction of the dichlorobenzenes. To maximize monochlorobenzene production (90% monochlorobenzene and 10% dichlorobenzene), benzene is lightly chlorinated the density of the reaction mixture is monitored to minimize polychlorobenzene production and the unreacted benzene is recycled. 

In 1988, the United States consumption of monochlorobenzene was 120 million kilograms 42% for the production of nitrochlorobenzenes, 28% for solvent uses, and the remaining 30% for other appHcations such as diphenyl ether, ortho- and i ra-phenylphenols, sulfone polymers, and diphenyldichlorosilane, an intermediate for specialty siHcones. 

The production of chlorobenzenes in Eastern Europe is concentrated in the former Soviet Union, Poland, and Czechoslovakia. The estimated capacity is 200—250 thousand metric tons the former Soviet Union has most (230 thousand tons) of this capacity. There is trade between Eastern and Western Europe on monochlorobenzene and the dichlorobenzenes, but the net trade balance is probably even at about 20 thousand metric tons. Eastern Europe exported 20 thousand metric tons of monochlorobenzene principally to Germany, Erance, and the United States. 

Japan, as of January 1, 1989, had a total capacity of 28 thousand metric tons of monochlorobenzene and 49 thousand tons of dichlorobenzenes. The Japanese prices have remained fairly constant since 1985. The Japanese consumption of -dichlorobenzene is 81% for moth control, 11% for PPS resins, and 8% for dye-stuffs. There has been very Htde export from Japan of chlorobenzenes and imports have been mainly -dichlorobenzene from the United States, Germany, Prance, and the United Kingdom. 

Monochlorobenzene. The largest use of monochlorobenzene in the United States is in the production of nitrochlorobenzenes, both ortho and para, which are separated and used as intermediates for mbber chemicals, antioxidants (qv), dye and pigment intermediates, agriculture products, and pharmaceuticals (Table 5). Since the mid-1980s, there have been substantial exports of both o-nitrochlorobenzene, estimated at 7.7 million kg to Europe and -nitrochlorobenzene, estimated at 9.5 million kg to the Far East. Solvent use of monochlorobenzene accounted for about 28% of the U.S. consumption. This appHcation involves solvents for herbicide production and the solvent for diphenylmethane diisocyanate manufacture and other chemical intermediates. 

Other apphcations for monochlorobenzene include production of diphenyl-ether, ortho- and i ra-phenylphenol, 4,4 -dichlorodiphenylsulfone, which is a primary raw material for the manufacture of polysulfones, diphenyldichlorosilane, which is an intermediate for specialty siUcones, Grignard reagents, and in dinitrochlorobenzene and catalyst manufacture. 

Today the sulphonation route is somewhat uneconomic and largely replaced by newer routes. Processes involving chlorination, such as the Raschig process, are used on a large scale commercially. A vapour phase reaction between benzene and hydrocholoric acid is carried out in the presence of catalysts such as an aluminium hydroxide-copper salt complex. Monochlorobenzene is formed and this is hydrolysed to phenol with water in the presence of catalysts at about 450°C, at the same time regenerating the hydrochloric acid. The phenol formed is extracted with benzene, separated from the latter by fractional distillation and purified by vacuum distillation. In recent years developments in this process have reduced the amount of by-product dichlorobenzene formed and also considerably increased the output rates. 

Chlorobenzene (monochlorobenzene) Chlorobromomethane 2-Chloro-l, 3-butadiene, see Chloroprene Chlorodifluoromethane (Freon 22)... 

Chloro-1 -nitropropane Chloroacetaldehyde a-Chloroacetophenone Chlorobenzene (monochlorobenzene) o-Chlorobenzylidine malononitrile Chlorobromomethane Chlorodiphenyl (42% chlorine) Chlorodiphenyl (54% chlorine) 2-Chloroethanol (ethylene chlorohydrin) Chloroform... 

Molybdenum insoluble compounds Molybdenum soluble compounds Monochloroacetic acid Monochlorobenzene (chlorobenzene) Monocrotophos Monomethyl aniline Monomethyl hydrazine Monomethylarsonic acid Morpholine... 

To a solution of 16.4 g (0.05B mol) of the free base in 75 ml of dry acetonitrile is added dropwise while cooling (ice bath) and stirring 14.5 ml (0.053 mol) of 3.6N ethereal hydrogen chloride. An equal volume of anhydrous ether is addedand the product altered, dried and recrystallized from monochlorobenzene. The product melts at about 177°C to 17B°C with sintering at about 176°C. The yield is about 11.0 g (60%). 

Typical liquid-phase reaction conditions for the chlorination of benzene using FeCls catalyst are 80-100°C and atmospheric pressure. When a high benzene/Cl2 ratio is used, the product mixture is approximately 80% monochlorobenzene, 15% p-dichlorobenzene and 5% o-dichlorobenzene. 

Chlorobenzene, also monochlorobenzene and paradichlorobenzene Chlorinator operation HCl absorption Condensers, HCl absorbers... 

Amines (primary and secondary aromatic) / -Chloranil The reaction depends on the catalytic effect of silica gel. Monochlorobenzene, as solvent for the reagent, also contributes. There is no reaction on cellulose layers. [17, 22]... 

Phenol (C5H5OH) or carboUc acid is an aromatic hydrocarbon derived originally from coal tar, but prepared synthetically in a process that utilizes monochlorobenzene as a starting point. Ninety-eight percent phenol appears as transparent crystals, while liquefied phenol consists of 88% USP solution of phenol in water. 

Monochlorobenzene is produced by the reaction of benzene with chlorine. A mixture of monochlorobenzene and dichlorobenzene is produced, with a small amount of trichlorobenzene. Hydrogen chloride is produced as a byproduct. Benzene is fed to the reactor in excess to promote the production of monochlorobenzene. 

Using the data given below, calculate the stream flows and draw up a preliminary flow-sheet for the production of 1.0 tonne monochlorobenzene per day. 

Design a plant to produce 20,000 tonnes/year of monochlorobenzene together with not less than 2000 tonnes/year of dichlorobenzene, by the direct chlorination of benzene. 

The subscripts B, M and D denote benzene, monochlorobenzene and dichlorobenzene respectively. 

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