Problems Chlorine

Because HCl is constandy present in most parts of the equipment, corrosion is always a potential problem. Chlorine and benzene, or any recycled material, must be free of water to trace amounts to prevent corrosion and deactivation of the catalyst. The reactor product contains HCl and iron. In some plants, the product is neutralized with aqueous NaOH before distillation. In others, it is handled in a suitably-designed distillation train, which includes a final residue from which FeCl can be removed with the high boiling tars. 

The low unsaturation requires powerful curing systems whilst the hydrocarbon nature of the polymer causes bonding problems. To overcome these problems chlorinated and brominated butyl rubbers (CIIR and BUR) have been introduced and have found use in the tyre industry. 

Cleaning protocols may often simply reduce the recirculating water to pH 6 to 7 and use a high dose of chlorine to achieve, say, 2 to 3 ppm free CI2 for 3 to 4 hours. For this process to work successfully, it needs to be undertaken in association with 100 to 200 ppm of biodispersant, plus 1 to 2 ppm of antifoam. Or for specific identified problems, chlorine may be used in conjunction with nonoxidizer, plus biodispersant and antifoam, of course. Where it is not possible to reduce the pH, bromine may replace chlorine. 

The catalysts used in the steam reforming process are poisoned by trace components in the hydrocarbon feed - particularly sulphur, chlorine and metal compounds. Sulphur is the most common problem. Chlorine compounds are... 

PROBLEM Chlorine has two isotopes 75% of all chlorine atoms are chlorine-35 and 25% are chlorine-37. How many neutrons are in these isotopes What is the atomic mass of chlorine ... 

While the results of the Wohler-Liebig paper could easily be fitted into Berzelius scheme, a parallel development could not. Some candles bleached with chlorine had given off highly irritating vapors at a gathering at the Tuileries. Dumas was asked to investigate the problem. Chlorine, it turned out, had replaced hydrogen in the wax, volume for volume, or equivalent for equivalent as... 

Controls vary with the problem. Chlorination and other chemical treatments commonly used for water-based problems in HVAC equipment may not be effective. Designated smoking areas have not always removed contaminants from the general office environment. When contaminants build up as a result of an inadequate supply of outdoor air, likely sources of contaminants for sick building syndrome are the HVAC systems. When located, the specific causes require removal at the source. 

Chlorine (usually as NaOCl) is an excellent universal biocide. Problems Chlorine compounds are corrosive to metals (only slightly with stainless steels). Chlorine is neutralized by organic matter (but a more concentrated solution, e.g., 1% NaOCl, will probably overcome the problem). Many of the chlorine household bleaches make effective and economical biocides. NaOCl (10%) stored in brown plastic bottles was stable for two years at 4°C and 1% solution for 20 weeks at 24 °C. Addition of 0.1% anionic detergent increases the power of hypochlorite (a useful anionic agent is sodium lauryl sulfate, 496). CAUTION A few anionic and some nonionic detergents will reduce active chlorine compounds. 

Currently, due to environmental problems, chlorine-free bleaching treatments are increasingly used considering that the residual effluent from traditional treatments contains organochlorine compounds with high toxicity [51],... 

An excess of ethylene is used to ensure essentially complete conversion of the chlorine, which is thereby eliminated as a problem for the downstream separation system. 

In a single reaction (where selectivity is not a problem), the usual choice of excess reactant is to eliminate the component which is more difficult to separate in the downstream separation system. Alternatively, if one of the components is more hazardous (as is chlorine in this example), again we try to ensure complete conversion. 

In practice, there is likely to be a trace of decane in the reactor eflfluent. However, this should not be a problem, since it can either be recycled with the unreacted chlorine or leave with the product, monochlorodecane (providing it can still meet product specifications). 

This problem is solved in the reactor shown in Fig. 10.6. Ethylene and chlorine are introduced into circulating liquid dichloroethane. They dissolve and react to form more dichloroethane. No boiling takes place in the zone where the reactants are introduced or in the zone of reaction. As shown in Fig. 10.6, the reactor has a U-leg in which dichloroethane circulates as a result of gas lift and thermosyphon effects. Ethylene and chlorine are introduced at the bottom of the up-leg, which is under sufficient hydrostatic head to prevent boiling. 

The toxicological problems associated with asbestos have been widely pubHshed and asbestos has been banned from most uses by the EPA. However, modem diaphragm cell chlorine plants have not had difficulty meeting the required exposure limits for asbestos fibers, and, as of 1990, the chlorine industry had an exemption allowing the continued use of asbestos as a diaphragm material. 

The practical problems He ia the separatioa of the chlorine from the hydrogea chloride and nitrous gases. The dilute nitric acid must be reconcentrated and corrosion problems are severe. Suggested improvements iaclude oxidation of concentrated solutions of chlorides, eg, LiCl, by nitrates, followed by separation of chlorine from nitrosyl chloride by distillation at 135°C, or oxidation by a mixture of nitric and sulfuric acids, separating the... 

Use of mercuric catalysts has created a serious pollution problem thereby limiting the manufacture of such acids. Other catalysts such as palladium or mthenium have been proposed (17). Nitration of anthraquinone has been studied intensively in an effort to obtain 1-nitroanthraquinone [82-34-8] suitable for the manufacture of 1-aminoanthraquinone [82-45-1]. However, the nitration proceeds so rapidly that a mixture of mono- and dinitroanthraquinone is produced. It has not been possible, economically, to separate from this mixture 1-nitroanthraquinone in a yield and purity suitable for the manufacture of 1-aminoanthraquinone. Chlorination of anthraquinone cannot be used to manufacture 1-chloroanthraquinone [82-44-0] since polychlorinated products are formed readily. Consequentiy, 1-chloroanthraquinone is manufactured by reaction of anthraquinone-l-sulfonic acid [82-49-5] with sodium chlorate and hydrochloric acid (18). 

For many waste streams, electrical efficiencies are compromised owing to the corrosivity of the solution toward the precipitated metals and/or the low concentrations of metals that must be removed. The presence of chloride in the solution is particularly troublesome because of the formation of elemental chlorine at the anode. Several commercial cells have become available that attempt to address certain of these problems (19). 

TSCA also addresses the problem of polychlorinated biphenyls (PCBs) and chlorinated fluorocarbons (CECs). EPA has developed regulations on the cleanup, handling, and disposal of PCBs. The manufacture and use of CECs has been banned for all but essential uses, in accordance with the Montreal Agreement, an international treaty on worldwide use of CECs. 

In dyehouses where sulfide effluent is a problem, sulfur dyes of good chlorine fastness that dye satisfactorily from a dithionite—caustic alkaU bath offer an advantage. Included in this group are Cl Sulfur Black 11, Cl Sulfur Red 10 [1326-96-1] (Cl 53228), Cl Sulfur Brown 96 [1326-96-1] (Cl 53228), Cl Vat Blue 42, and Cl Vat Blue 43. The shades of these dyes can be brightened by the addition of vat dyes thus increasing the fastness of the resulting dye. 

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