Halogenated hydrocarbons trichloroethylene

It is important to produce HCl rather than elemental chlorine, CI2, because HCl can be easily scmbbed out of the exhaust stream, whereas CI2 is very difficult to scmb from the reactor off-gas. If the halogenated hydrocarbon is deficient in hydrogen relative to that needed to produce HCl, low levels of water vapor may be needed in the entering stream (45) and an optional water injector may be utilized. For example, trichloroethylene [79-01 -6] C2HCI2, and carbon tetrachloride require some water vapor as a source of hydrogen (45). 

Halogenated hydrocarbons depress cardiac contractility, decrease heart rate, and inhibit conductivity in the cardiac conducting system. The cardiac-toxicity of these compounds is related to the number of halogen atoms it increases first as the number of halogen atoms increases, but decreases after achieving the maximum toxicity when four halogen atoms are present. Some of these compounds, e.g., chloroform, carbon tetrachloride, and trichloroethylene, sensitize the heart to catecholamines (adrenaline and noradrenaline) and thus increase the risk of cardiac arrhythmia. 

Several lower partially halogenated hydrocarbons (dichloromethane, bromo-methane, trichloroethylene, 1,1,1-trichloroethane) have no measurable flash point, but are nonetheless capable of forming flammable and explosive mixtures with air, and several such accidents are recorded. 

Soluble in alcohol, ether (Weast, 1986), and many low molecular weight hydrocarbons (pentane, hexane, heptane), and halogenated hydrocarbons such as chloroform, methylene chloride, trichloroethylene. 

The analytes separated on GC column are determined by a halogen-specific detector, such as an electrolytic conductivity detector (ELCD) or a microcoulo-metric detector. An ECD, FID, quadrupole mass selective detector, or ion trap detector (ITD) may also be used. A photoionization detector (PID) may also be used to determine unsaturated halogenated hydrocarbons such as chlorobenzene or trichloroethylene. Among the detectors, ELCD, PID, and ECD give a lower level of detection than FID or MS. The detector operating conditions for ELCD are listed below ... 

The aliphatic and aromatic hydrocarbons may contain a substituted halogen element and are often referred to as halogenated hydrocarbons. These include, for example, perchloroethylene, trichloroethylene, and carbon tetrachloride. Organic solvents are very useful and have extensive applications in industry because they help in the manufacture of oils, fats, resins, rubber, and plastics. In fact, the role of organic solvents increased in the latter half of the nineteenth century with the development of the coal-tar industry. The wide application of organic solvents grew and became diverse and global. 

Workers come in contact with a large number of chemical substances in work areas, as does the general public. The commonly found chemical carcinogens are grouped under (1) polycyclic aromatic hydrocarbons (PAHs), (2) nitroso compounds, (3) halogenated hydrocarbons (solvents e.g., carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride), (4) inorganic metals and minerals (beryllium, cadmium, nickel, cobalt, chromium, asbestos and arsenic), and (5) naturally occurring chemical substances (aflatoxins). 

Halogenated hydrocarbons. Several of these compounds are commonly used as solvents. Examples include carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride. 

The sorption capacity of diatomite (the ratio of lbs of sorbent required to clean up lbs of spilled liquid) ranges from 1.1 for aliphatic hydrocarbons such as isoprene to 2.5 for aliphatic halogenated hydrocarbons such as trichloroethylene. The sorption capacity of diatomite is rather poor. However, this material is relatively inexpensive and can be purchased for approximately 1.50/lb, depending upon quantity ordered. 

The sorption capacity of clay ranges from 1.0 for alcohols and basic compo unds such as allyl alcohol and ammonium hydroxide respectively, to 1.6 for aliphatic halogenated hydrocarbons such as trichloroethylene. Therefore, the sorption capacity of clay is very low when compared to the other materials available. However, this material is one of the most inexpensive materials and can be purchased for approximately 0.04/lb to 0.12/lb depending upon supplier and quantity ordered. 

Aliphatic and aromatic halogenated hydrocarbons are widely used as industrial reagents, cleaning agents and solvents. The toxicity of the individual substances is very varied, e.g. relative to trichloroethane (nominal toxicity = 1), trichloroethylene, chloroform and carbon tetrachloride have a toxicity of 8, 60 and 190, respectively. (s. tab. 30.3)... 

Early uses of trichloroethylene included degreasing, and by 1940, a formulation of trichloroethylene named Trilene had widespread use as an anesthetic. Toxicity soon became apparent, especially after cranial nerve injuries and activated latent herpes infections resulted from anesthesia (Defalque 1961 Humphrey and McClelland 1944). Other important halogenated hydrocarbons include methylene chlo-... 

G. R. Umbreit (24) has used the gas-equilibration technique to measure several halogenated hydrocarbons, employing both flame ionization detection (FID) and electron capture (EC). Halogenated hydrocarbons included dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2,2-trichlo-... 

Products of incomplete combustion have been shown to increase as the catalyst deactivates. Agarwal et al. report that the oxidation of a mixed stream of trichloroethylene and C5-C9 hydrocarbons over a chromia alumina catalyst produced CO equal to 32% of the total CO + CO2 with fresh catalyst. With a deactivated catalyst, CO had risen to 54% of the total carbon oxides produced. Pope et al. report products of incomplete combustion for the oxidation of 1,1,1-trichloroethane over a cobalt oxide catalyst. The cause of the catalyst deactivation has not been established, but both Agarwal et al. and Michalowiczl reference evidence of carbonaceous deposits on the catalyst after oxidation of halogenated hydrocarbons. ESCA studies by Hucknall et al. O have always shown a carbon residue on palladium alumina catalysts in addition to adsorbed halogen. 

Causes of acute chemical hepatitis include exposure to industrial solvents such as halogenated hydrocarbons (methylene chloride, trichloroethylene, and trichloroethane) carbon tetrachloride (only rarely encountered in modem industry) and dimethylformamide, dinitropropane, and di-methylacetamide. The jet and rocket fuel components hydrazine and monomethylhydrazine are also potent hepatotoxins. 

Beside -alkanes, MN-100 also shows high affinity to halogenated hydrocarbons (Table 10.6). Chlorocarbons are retained somewhat longer than the corresponding -alkanes having approximately the same polarizability. The especially strong retention of trichloroethylene is peculiar, and is most likely caused by an additional contribution of specific interactions between the 7t-system of the adsorbate s double bond and the aromatic polymer to the total adsorption energy. In contrast, fluorocarbons are more weakly retained than -alkanes with similar polarizability most likely, the dispersion interactions of fluorocarbons with aromatic polymers are weaker. 

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