Chlorohydrin units

Stereoselective aldol condensation. The Ph4SbBr-catalyzed condensation of tin enolates with a-chlorocycloalkanones furnishes predominantly aldol products with a cij-chlorohydrin unit. 

Only industrial producers (e.g. Dow) with a highly integrated and cost competitive supply chain of chlorine-caustic soda (through production from caustic soda by NaCl electrolysis) to provide chlorine for the chlorohydrin reactor and sodium hydroxide for the dehydrochlorination step can operate chlorohydrin units for propylene oxide production competitively with indirect oxidation units. 

Ethylene glycol was originally commercially produced in the United States from ethylene chlorohydrin [107-07-3J, which was manufactured from ethylene and hypochlorous acid (eq. 8) (see Chlorohydrins). Chlorohydrin can be converted direcdy to ethylene glycol by hydrolysis with a base, generally caustic or caustic/bicarbonate mix (eq. 9). An alternative production method is converting chlorohydrin to ethylene oxide (eq. 10) with subsequent hydrolysis (eq. 11). 

Propylene oxide [75-56-9] is manufactured by either the chlorohydrin process or the peroxidation (coproduct) process. In the chlorohydrin process, chlorine, propylene, and water are combined to make propylene chlorohydrin, which then reacts with inorganic base to yield the oxide. The peroxidation process converts either isobutane or ethylbenzene direcdy to an alkyl hydroperoxide which then reacts with propylene to make propylene oxide, and /-butyl alcohol or methylbenzyl alcohol, respectively. Table 1 Hsts producers of propylene glycols in the United States. 

Synthesis. The total aimual production of PO in the United States in 1993 was 1.77 biUion kg (57) and is expected to climb to 1.95 biUion kg with the addition of the Texaco plant (Table 1). There are two principal processes for producing PO, the chlorohydrin process favored by The Dow Chemical Company and indirect oxidation used by Arco and soon Texaco. Molybdenum catalysts are used commercially in indirect oxidation (58—61). Capacity data for PO production are shown in Table 1 (see Propylene oxide). 

Production of propylene oxide in the United States in 1993 was estimated at 1,240,000 metric tons, and as having a 10-yr average aimual growth rate of 3.9% (229). Projections were for continued growth at about 4%/yr. Producers include Dow Chemical s chlorohydrin plants in Ereeport, Texas, and Plaquemine, Louisiana, and ARCO Chemical s hydroperoxide plants in Bayport and Chaimelview, Texas. Texaco started up a 180,000-t/yr plant in Port... 

The most important chemical reaction of chi orohydrin s is dehydrochloriaation to produce epoxides. In the case of propylene oxide. The Dow Chemical Company is the only manufacturer ia the United States that still uses the chlorohydrin technology. In 1990 the U.S. propylene oxide production capacity was hsted as 1.43 x 10 t/yr, shared almost equally by Dow and Arco Chemical Co., which uses a process based on hydroperoxide iatermediates (69,70). More recentiy, Dow Europe SA, aimounced a decision to expand its propylene oxide capacity by 160,000 metric tons per year at the Stade, Germany site. This represents about a 40% iacrease over the current capacity (71). 

The merchant market for chi orohydrin s is small, primarily for specialty appHcations. Ethylene chlorohydrin is sold ia the United States by BASF Corp., Parsippany, N.J., available ia 230 kg net lined steel dmms. Glycerol monochlorohydrin (3-chloro-l,2-propanediol) is available from Dixie Chemical Co., Houston, Tex., in lined steel dmms (227.3 kg net) from Raschig Corp., Richmond, Va. and from Henley Chemicals, Inc., Montvale, N.J., ia steel dmms (240 kg net). Glycerol dichi orohydrin (l,3-dichloro-2-propanol) is not currentiy being produced for the U.S. merchant market but has been available ia the past at a selling price of 5—6/kg. 

Ethylene oxide has been produced commercially by two basic routes the ethylene chlorohydrin and direct oxidation processes. The chlorohydrin process was first iatroduced dufing World War I ia Germany by Badische Anilin-und Soda-Eabfik (BASE) and others (95). The process iavolves the reaction of ethylene with hypochlorous acid followed by dehydrochlofination of the resulting chlorohydrin with lime to produce ethylene oxide and calcium chloride. Union Carbide Corp. was the first to commercialize this process ia the United States ia 1925. The chlorohydrin process is not economically competitive, and was quickly replaced by the direct oxidation process as the dominant technology. At the present time, all the ethylene oxide production ia the world is achieved by the direct oxidation process. 

About 2 X 10 Ib/yeai of 1,2-epoxypropane is produced in the United States as an intennediate in the preparation of various polymeric materials, including polyurethane plastics and fofflns and polyester resins. A large fraction of the 1,2-epoxypropane is made from propene by way of its chlorohydrin. 

One ocher reaction noc shown is the formation of propylene dichloride. The demand for this compound is generally insufficient to absorb all the coproduction, so it also ends up on the list of things to be disposed of coming from the PO-chlorohydrin process, But despite this and all the ocher problems already mentioned about the chlorohydrin route, the process remains economically healthy—breathing heavily, but healthy. Indeed, 40 to 50% of the PO produced in the United States comes from this route. 

Benson and Teta (1993) studied the mortality among 278 chlorohydrin production workers who had ever been employed at a facility in the United States between 1940 and 1967. The follow-up period was from 1940 to 1988. This was a 10-year update of an earlier study conducted by Greenberg et al. (1990). There were 147 deaths (SMR, 1.0) and 40 cancer deaths (SMR, 1.3) observed. Excesses of pancreatic cancer (SMR, 4.9 95% CI, 1.6-11.4 8 cases) and lymphatic and haematopoietic cancers (SMR, 2.9 95% CI, 1.3-5.8 ... 

Olsen et al. (1997) studied mortality among 1361 men employed at two chlorohydrin production facilities in the United States similar to that studied by Benzon and Teta (1993). There were 300 deaths (SMR, 0.9) and 75 cancer deaths (SMR, 0.9) observed. The risks of pancreatic cancer (SMR, 0.3 95% CI, 0.01-1.4 1 case) and lymphatic and haematopoietic cancers (SMR, 1.3 95% CI, 0.6-2.4 10 cases) were less than those observed by Benson and Teta and no other cancers were observ ed in excess. It was not possible to link mortality to any particular chemical exposure and levels of exposure were not reported. 

Chlorohydrin for the manufacture of dinitrochlorohydrin must be as pure as possible and should contain the minimum amount of water, HC1 and polymerization products of glycerine, since ithe presence of these substances favours the formation of an emulsion during nitration and washing. Usually chlorohydrin was made in the explosives factory. After a single distillation the substance was transferred to the nitrating unit generally in admixture with glycerine. 

In the past, glycerol was produced mainly from propene via allyl chloride and epi-chlorohydrin, a process developed by I. G. Farben and in operation since 1943. Today, glycerol is obtained almost completely as a coproduct in oleochemistry (fat splitting) and biodiesel production (transesterification) with 110 kg crude glycerol or 100 kg pure glycerol per ton of biodiesel [37]. With the rise in biodiesel production, the availability increased while the price decreased drastically by approximately 66% within 15 years in the United States [38]. 

Ethylene oxide was discovered in 1859 by Wurtz. He stated that ethylene oxide could not be made by direct oxidation of ethylene, and it was nearly 80 years before this was disproved. Wurtz made ethylene oxide by the method known today as the chlorohydrin process, in which ethylene is reacted in turn with hypochlorous acid and base. This process was commercialized during World War I in Germany, and until 1985 was still used commercially in the United States. 

At the same time, all these processes might be prompted by the shift of the oxygen bridge, whereupon room is left around the HO-C-C(Me) unit for further operations. Such a shift would be driven by a still unclear ejection of chloride anion without the normal hydride transfer to the chlorine-bearing carbon. Curiously, there seems to be a natural propensity of compound I towards such a bizarre change since just heating it at 100°C or above causes its equilibration with pinol chlorohydrin VI. 

The chlorohydrin process practiced by Dow Chemical in the United States, weds the chlorine component of chloralkali technology to propylene oxide production. Chlorine added to water produces hypochlorous acid and hydrochloric acid (Eq. 19.44). 

Until 1969, the only method for producing propylene oxide was the chlorohydrin process, using a technique similar to that used to synthesize ethylene oxide, and most of the production units were converted ethylene oxide plants. 

It was found that the reaction was a general one between aliphatic halogen compounds and water-soluble allaJine or Jkaline-earth polysulfides. Many different organic dihalides have been found to react with ium polysulfide to produce polymers. Commercially available dihalides include uthylene dichloride, propylene dichloride, dichloroethyl ether, tri ycol dichloride, and dichlorodiethyl formal. Dichlorodiethyl formal is the chief dihalide used in the polymers produced in the United States. It is made by the reaction of ethylene chlorohydrin with formaldehyde in the presence of an acidic catalyst ... 

I.2. Propylene Chlorohydrin. Propylene chlorohydrin is one of the most important intermediates used in the production of PO, which is a raw material for producing propylene glycols and urethane polyether polyols. The United States and Western Europe are the largest producers of propylene chlorohydrin, accounting for 74% of the world s production. The main environmental issues relate to the chlorinated waste generated in the process and the disposal of the byproduct calcium chloride sludge. The formation of... 

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