Solvent - chlorinated

Chlorinated solvents - such as trichloroethane (TCE) - are used by textile manufacturers to dissolve other substances during manufacturing and to clean fabrics. TCE is an ozone-depleting substance that can persist in the environment. It is also known to affect the central nervous system, liver and kidneys. Sinee 2008 the EU has severely restricted the use of TCE in both produets and fabrie cleaning. 

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Uses. Tetrahydrofurfuryl alcohol is of interest in chemical and related industries where low toxicity and minimal environmental impact are important (134). For many years tetrahydrofurfuryl alcohol has been used as a specialty organic solvent. The fastest growing appHcations are in formulations for cleaners (135) and paint strippers (136), often as a replacement for chlorinated solvents (137). Other major appHcations include formulations for crop sprays, water-based paints, and the dyeing and finishing of textiles and leathers. Tetrahydrofurfuryl alcohol also finds appHcation as an intermediate in pharmaceutical appHcations. 

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

Properties. The DPXs are all crystalline soHds melting points and densities are given in Table 1. Their solubiUty in aromatic hydrocarbons is Limited. At 140°C, the solubiUty of DPXN in xylene is only about 10%. DPXC is more readily soluble in chlorinated solvents, eg, in methylene chloride at 25°C its solubihty is 10%. In contrast, the corresponding figure for DPXN is 1.5%. 

Because of its relatively high, price, there have been continuing efforts to replace acetylene in its major appHcations with cheaper raw materials. Such efforts have been successful, particularly in the United States, where ethylene has displaced acetylene as raw material for acetaldehyde, acetic acid, vinyl acetate, and chlorinated solvents. Only a few percent of U.S. vinyl chloride production is still based on acetylene. Propjiene has replaced acetylene as feed for acrylates and acrylonitrile. Even some recent production of traditional Reppe acetylene chemicals, such as butanediol and butyrolactone, is based on new raw materials. 

Chlorinated Solvents. Originally, successive chlorination and dehydro-chlorination of acetylene was the route to trichloroethylene [79-01-6], C2HCI3, and perchloroethylene [127-18-4], C2C1. ... 

Chlorine cannot be stored economically or moved long distances. International movements of bulk chlorine are more or less limited to movements between Canada and the United States. In 1987, chlorine moved in the form of derivatives was 3.3 million metric tons or approximately 10% of total consumption (3). Exports of ethylene dichloride, vinyl chloride monomer, poly(vinyl chloride), propylene oxide, and chlorinated solvents comprise the majority of world chlorine movement. Countries or areas with a chlorine surplus exported in the form of derivatives include Western Europe, Bra2il, USA, Saudi Arabia, and Canada. Countries with a chlorine deficit are Taiwan, Korea, Indonesia, Vene2uela, South Africa, Thailand and Japan (3). 

Calcium carbide has been used in steel production to lower sulfur emissions when coke with high sulfur content is used. The principal use of carbide remains hydrolysis for acetylene (C2H2) production. Acetylene is widely used as a welding gas, and is also a versatile intermediate for the synthesis of many organic chemicals. Approximately 450,000 t of acetylene were used aimuaHy in the early 1960s for the production of such chemicals as acrylonitrile, acrylates, chlorinated solvents, chloroprene, vinyl acetate, and vinyl chloride. Since then, petroleum-derived olefins have replaced acetylene in these uses. 

Solvent Resistance. Elastomeric fibers tend to swell in certain organic solvents mbber fibers swell in hydrocarbon solvents such as hexane. Spandex fibers become highly swollen in chlorinated solvents such as tetrachloroethylene [127-18-4] (Perclene). Although the physical properties of spandex fibers return to normal after the solvent evaporates, considerable amounts of its stabilizers may have been extracted. Therefore, the development of stabilizers that are more resistant to solvent extraction has become important as solvent scouring during mill processing replaces aqueous scouring at many mills, especially in Europe (26). 

Of the estimated 710,000 t consumed in 1990, 25% was used to produce vinyl chloride [75-01-4] monomer (VCM), 14% for vinyl acetate [108-05-4] monomer (VAM), 23% for butanediol, 14% for industrial use, and the balance to produce other products such as acryUc acid, synthetic mbber, chlorinated solvents, and acetylene black. The demand for PVC is expected to decrease as legislation limiting its use in packaging is pending. Consequentiy, VCM consumption will also suffer. 

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

Acylation. In chlorinated solvents, maleic anhydride reacts with aromatic hydrocarbons (ArH) in the presence of aluminum chloride... 

A more energy-efficient variation of photohalogenation, which has been used since the 1940s to produce chlorinated solvents, is the Kharasch process (45). Ultraviolet radiation is used to photocleave ben2oyl peroxide (see Peroxides and peroxide compounds). The radical products react with sulfuryl chloride (from SO2 and CI2) to Hberate atomic chlorine and initiate a radical chain process in which hydrocarbons become halogenated. Thus, for Ar = aryl,... 

Transesterification. There has been renewed interest in the transesterification process for preparation of polycarbonate because of the desire to transition technology to environmentally friendly processes. The transesterification process utilizes no solvent during polymerization, producing neat polymer direcdy and thus chlorinated solvents may be entirely eliminated. General Electric operates a polycarbonate plant in Chiba, Japan which produces BPA polycarbonate via this melt process. 

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

The fluorinated titanocycle related to (28) is not obtained from C H CMUCgF. Photolysis of CP2T1X2 always gives first scission of a Cp—Tibond. In a chlorinated solvent, the place vacated by Cp is assumed by Cl. In the absence of some donor, the radical dimerizes (298—299). 

The physical properties of vinyl chloride are Hsted in Table 1 (12). Vinyl chloride and water [7732-18-5] are nearly immiscible. The equiUbrium concentration of vinyl chloride at 1 atm partial pressure in water is 0.276 wt % at 25°C, whereas the solubiUty of water in vinyl chloride is 0.0983 wt % at 25°C and saturated pressure (13). Vinyl chloride is soluble in hydrocarbons, oil, alcohol, chlorinated solvents, and most common organic Hquids. 

The Evaluation of Carcinogenic Risks to Humans Dy Cleaning, Some Chlorinated Solvents and Otherindustrial Chemicals, L4RC Monographs, 63 (Feb. 1995). 

DAG is treated with ethanol and hydrochloric acid in the presence of inert solvent, eg, chlorinated solvents, hydrocarbons, ketones, etc. The L-ascorbic acid precipitates from the mixture as it forms, minimising its decomposition (69). Cmde L-ascorbic acid is isolated through filtration and purified by recrystallization from water. The pure L-ascorbic acid is isolated, washed with ethanol, and dried. The mother Hquor from the recrystallization step is treated in the usual manner to recover the L-ascorbic acid and ethanol contained in it. The cmde L-ascorbic acid mother Hquor contains solvents and acetone Hberated in the DAG hydrolysis. The solvents are recovered by fractional distillation and recycled. Many solvent systems have been reported for the acid-catalyzed conversion of DAG to L-ascorbic acid (46). Rearrangement solvent systems are used which contain only the necessary amount of water required to give >80% yields of high purity cmde L-ascorbic acid (70). 

Dichlorine monoxide is an intermediate in the manufacture of calcium hypochlorite. It has been used in sterilization for space appHcations (70) (see Sterilization techniques). Its use in the preparation of chlorinated solvents (71) and chloroisocyanurates has been described. Chlorine monoxide has been shown to be effective in bleaching of pulp (qv) and textiles (72—74). 

Chlorination of various hydrocarbon feedstocks produces many usehil chlorinated solvents, intermediates, and chemical products. The chlorinated derivatives provide a primary method of upgrading the value of industrial chlorine. The principal chlorinated hydrocarbons produced industrially include chloromethane (methyl chloride), dichloromethane (methylene chloride), trichloromethane (chloroform), tetrachloromethane (carbon tetrachloride), chloroethene (vinyl chloride monomer, VCM), 1,1-dichloroethene (vinylidene chloride), 1,1,2-trichloroethene (trichloroethylene), 1,1,2,2-tetrachloroethene (perchloroethylene), mono- and dichloroben2enes, 1,1,1-trichloroethane (methyl chloroform), 1,1,2-trichloroethane, and 1,2-dichloroethane (ethylene dichloride [540-59-0], EDC). 

Acetjiene has found use as a feedstock for production of chlorinated solvents by reaction with hydrogen chloride or chlorine (6). However, because of safety concerns and the lower price of other feedstock hydrocarbons, very Htfle acetylene is used to produce chlorinated hydrocarbons in the United States (see Acetylene-derived chemicals). 

Many chlorinated hydrocarbons react readily with aluminum in the so-caHed bleeding reaction. A red aluminum chloride—chlorinated hydrocarbon complex is formed. Storage of uninhibited chlorinated solvents in aluminum vessels results in corrosion in a short period of time. Proprietary organic inhibitors permit commercial use of reactive solvents such as 1,1,1-trichloroethane and trichloroethylene for cleaning of aluminum. 

The physical properties of methylene chloride are Hsted in Table 1 and the binary a2eotropes in Table 2. Methylene chloride is a volatile Hquid. Although methylene chloride is only slightly soluble in water, it is completely miscible with other grades of chlorinated solvents, diethyl ether, and ethyl alcohol. It dissolves in most other common organic solvents. Methylene chloride is also an excellent solvent for many resins, waxes, and fats, and hence is well suited to a wide variety of industrial uses. Methylene chloride alone exhibits no dash or fire point. However, as Htde as 10 vol % acetone or methyl alcohol is capable of producing a dash point. 

Further dechlorination may occur with the formation of substituted diphenyhnethanes. If enough aluminum metal is present, the Friedel-Crafts reactions involved may generate considerable heat and smoke and substantial amounts of hydrogen chloride, which reacts with more aluminum metal, rapidly forming AlCl. The addition of an epoxide inhibits the initiation of this reaction by consuming HCl. Alkali, alkaline-earth, magnesium, and zinc metals also present a potential reactivity hazard with chlorinated solvents such as methylene chloride. 

Eatahties have occurred when unprotected workers have entered an unventilated tank or piece of equipment that contained high vapor concentrations of a chlorinated solvent such as methylene chloride. 

Reactivities of several chlorinated solvents, including chloroform, with aluminum, iron, and 2inc in both dry and wet systems have been deterrnined, as have chemical reactivities in oxidation reactions and in reactions with amines (11). Unstabilized wet chloroform reacts completely with aluminum and attacks zinc at a rate of >250 //m/yr and iron at <250 //m/yr. The dry, uiiinhibited solvent attacks aluminum and zinc at a rate of 250 )J.m/yr and iron at 25 ]lni / yr. 

Carbon tetrachloride is the oldest and was the most extensively used chlorinated solvent in degreasing and dry-cleaning operations for many years. Consequently, its narcotic and toxic properties have been the subject of much investigation. Carefiil investigations have repeatedly shown carbon tetrachloride to be one of the most harm fill of the common solvents (37). 

Toxicity. 1,1-Dichloroethane, like all volatile chlorinated solvents, has an anesthetic effect and depresses the central nervous system at high vapor concentrations. The 1991 American Conference of Governmental Industrial Hygienists (ACGIH) recommends a time-weighted average (TWA) solvent vapor concentration of 200 ppm and a permissible short term exposure level (STEL) of 250 ppm for worker exposure. The oral LD q of... 

Dichloroethane [107-06-2] ethylene chloride, ethylene dichloride, CH2CICH2CI, is a colorless, volatile Hquid with a pleasant odor, stable at ordinary temperatures. It is miscible with other chlorinated solvents and soluble in common organic solvents as well as having high solvency for fats, greases, and waxes. It is most commonly used in the production of vinyl chloride monomer. 

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