Industrial solvents methylene chloride

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. 

PROBLEM 8.13 The industrial degreasing solvent methylene chloride, CH2C12, is prepared from methane by reaction with chlorine ... 

Chloromethanes have varied applications in the chemical industry. Methyl chloride is mainly used in the manufacture of silicones, tetramethyl lead, and as a solvent. Methylene chloride (often called methylene dichloride or di-chloromethane, DCM) is a multipurpose solvent, a degreasing agent, and a... 

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). 

A deterrnination that carbon monoxide might be a metaboUte of methylene chloride in humans (33) suggests that unacceptable levels of carboxyhemoglobin would exist in the blood of persons exposed to methylene chloride vapors at concentrations greater than 500 ppm for extended periods of time. These conditions are rarely encountered in most industrial appHcations. However, as with any organic solvent, adequate ventilation should be provided to ensure compliance with all industrial and governmental regulations. 

Methylene Chloride White Paper, Halogenated Solvents Industry Alliance (HSIA), Feb. 1989. 

Extraction from Aqueous Solutions Critical Fluid Technologies, Inc. has developed a continuous countercurrent extraction process based on a 0.5-oy 10-m column to extract residual organic solvents such as trichloroethylene, methylene chloride, benzene, and chloroform from industrial wastewater streams. Typical solvents include supercritical CO9 and near-critical propane. The economics of these processes are largely driven by the hydrophihcity of the product, which has a large influence on the distribution coefficient. For example, at 16°C, the partition coefficient between liquid CO9 and water is 0.4 for methanol, 1.8 for /i-butanol, and 31 for /i-heptanol. 

Unlike petroleum hydrocarbons, organic compounds in general followed a different evolutionary path. Chlorinated solvents are a common group of organic compounds, and are also the most frequently encountered contaminant in groundwater. Common industrial chemicals that are characterized as chlorinated solvents include trichloro-ethene (TCE), 1,1,1-trichloroethane (TCA), tetrachloroethene (PCE) or perchloro-ethylene, chlorofluorocarbon (Freon)-113 (i.e., 1,1,2-trichloroethane or 1,2,2-tri-fluoroethane), and methylene chloride. In 1997, the EPA reported the presence of TCE and PCE in 852 of 945 groundwater supply systems throughout the United States and in 771 of 1420 Superfund sites. 

The three examples related to solvent replacement cover the generation and evaluation of solvent alternatives for Ethyl Glycol Acetate, Ethyl Glycol and Methylene Chloride. Where feasible, the selected solvent alternatives have been tested under conditions of industrial application and/or laboratoiy scale experiments with very encouraging results. 

The above solution procedure has been applied to find replacement solvents for the following solvents Ethyl Glycol Acetate, Ethyl Glycol and Methylene Chloride. These three solvents are extensively used in the paints and ink industry, although, recent studies have shown that they carry an appreciable environmental burden in addition to being found harmful for the health of the people exposed to them (for example, employees in the manufacturing plants and/or consumers). 

The remaining solvent candidate, i.e., Propanone was tested as a replacement of Methylene Chloride under laboratory conditions and the results were found to be promising (Constantinou 2005). Eventhough it was not applied under actual industrial conditions, Propanone appears to be a likely replacement for Methylene Chloride. 

Kraft Lignin. A softwood kraft lignin (KL) was isolated from a partly evaporated, industrial kraft black liquor by precipitation through the addition of dilute sulfuric acid as described elsewhere (7). The lignin was thereafter fractionated by successive extraction with organic solvents (7). The KL fraction used in the present investigation was the second of five fractions obtained (propanol soluble - methylene chloride insoluble). 

The irritancy properties of isophorone have also been observed in humans exposed occupationally to isophorone. In an industrial hygiene survey, Kominsky (1981) reported that the eye and nose irritation complained of by a screen printer could have been caused by 4-minute exposure to 25.7 ppm isophorone, which was measured in the personal breathing zone while the worker was washing a screen. Lee and Frederick (1981) found that eye, respiratory, and skin irritation were among the complaints of 27/35 workers in a printing plant where isophorone and other solvents (xylene, methylene chloride, and toluene) were used. On the day of measurement, two of the screen printers were found to be exposed to 8-hour TWA concentrations of isophorone of 0.7 and 14 ppm, but it was not clear whether these two individuals were among the workers complaining of irritation. The odor threshold for isophorone in air has been reported to be 0.2 ppm (v/v) (Amoore and Hautala 1983). 

The wood industry is the major consumer of technical chloro-phenols. In the United States and in Canada it has been assumed that more than Q0% of pentachlorophenol (PCP) is used for wood perservation and wood protection (38,5jJ. PCP dissolved in various solvents (mineral spirits, fuel oil, kerosene and methylene chloride), is the major compound used for wood perservation. This procedure involves the use of pressure and vacuum cycles to obtain deep and optimum retention of the perservative. This process is used to produce a product which will have a long period of service such as railway ties, pilings and hydropoles. 

Food Applications, Carbon dioxide, a nontoxic material, can be used to extract thermally labile food components at near-ambient temperatures. The food product is thus not contaminated with residual solvent, as is potentially the case when using conventional liquid solvents such as methylene chloride or hexane. In the food industry, C02 is not recorded as a foreign substance or additive. Supercritical solvents not only can remove oils, caffeine, or cholesterol from food substrates, but can also be used to fractionate mixtures such as glycerides and vegetable oils into numerous components. 

The forest industry has used extensive amounts of chloropheols (CPs) for the preservation of timber against blue sapstain fungi. In the U.S., pentachorophenol (PCP) ia mainly used (Cirelli, 1978), while in Europe and Japan, various CP congener mixtures are typical. Preservative solutions are prepared either by dissolution of CPs in sodium hydroxide to produce concentrated chlorophenate solutions, or dissolution in fuel oil or kerosene. If these solvents are not available, liquid petroleum gas, methylene chloride, isopropyl alcohol, or methanol are used. 

Ethylene glycol in the presence of an acid catalyst readily reacts with aldehydes and ketones to form cyclic acetals and ketals (60). 1,3-Dioxolane [646-06-0] is the product of condensing formaldehyde and ethylene glycol. Applications for 1,3-dioxolane are as a solvent replacement for methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane, and methyl ethyl ketone as a solvent for polymers as an inhibitor in 1,1,1-trichloroethane as a polymer or matrix interaction product for metal working and electroplating in lithium batteries and in the electronics industry (61). 1,3-Dioxolane can also be used in the formation of polyacetals, both for homopolymerization and as a comonomer with formaldehyde. Cyclic acetals and ketals are used as protecting groups for reaction-sensitive aldehydes and ketones in natural product synthesis and pharmaceuticals (62). 

More than 4.5 million metric t of solvents is used in the United States annually, and it has been suggested by industry experts that ethyl lactate could replace conventional solvents in more than 80% of these applications (34). Vertec Biosolvents Inc. is currently using ethyl lactate in soy oil-solvent blends. Applications targeted by Vertec Biosolvents include conventional solvents that are under environmental scrutiny such as methylene chloride, methyl ethyl ketone, and N-methyl pyrrolidone (36). Table 3 lists the selling prices of some common solvents. 

One of the major uses of activated carbon is in the recovery of solvents from industrial process effluents. Dry cleaning, paints, adhesives, polymer manufacturing, and printing are some examples. Since, as a result of the highly volatile character of many solvents, they cannot be emitted directly into the atmosphere. Typical solvents recovered by active carbon are acetone, benzene, ethanol, ethyl ether, pentane, methylene chloride, tetrahydrofuran, toluene, xylene, chlorinated hydrocarbons, and other aromatic compounds [78], Besides, automotive emissions make a large contribution to urban and global air pollution. Some VOCs and other air contaminants are emitted by automobiles through the exhaust system and also by the fuel system, and activated carbons are used to control these emissions [77,78],... 

Methylene chloride (CH2C12) and chloroform (CHC13) are also good solvents for cleaning and degreasing work. Methylene chloride was once used to dissolve the caffeine from coffee beans to produce decaffeinated coffee. Concerns about the safety of coffee with residual traces of methylene chloride prompted coffee producers to use liquid carbon dioxide instead. Chloroform is more toxic and carcinogenic than methylene chloride it has been replaced by methylene chloride and other solvents in most industrial degreasers and paint removers. 

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