Alternative processes chlorine

In two proposed alternative processes, the chlorine is replaced in the hypochlorination reaction by hypochlorous acid [7790-92-3] HOCl, or tert-huty hypochlorite. In the first, a concentrated (>10% by weight) aqueous solution of hypochlorous acid, substantially free of chloride, chlorate, and alkah metal ions, is contacted with propylene to produce propylene chlorohydrin (113). The likely mechanism of reaction is the same as that for chlorine, as chlorine is generated in situ through the equiUbrium of chlorine and hypochlorous acid (109). 

In the second proposed alternative process, tert-huty hypochlorite, formed from the reaction of chlorine and tert-huty alcohol, reacts with propylene and water to produce the chlorohydrin. The alcohol is a coproduct and is recycled to generate the hypochlorite (114—116). No commercialisation of the hypochlorous acid and tert-huty hypochlorite processes for chlorohydrin production is known. 

Terrence Collins is the Thomas Lord Professor of Chemistry at Carnegie Mellon University who contends that the dangers of chlorine chemistry are not adequately addressed by either academe or industry, and alternatives to chlorine and chlorine processors must be pursued. He notes, Many serious pollution episodes are attributable to chlorine products and processes. This information also belongs in chemistry courses to help avoid related mistakes. Examples include dioxin-contaminated 2,4,5-T, extensively used as a peacetime herbicide and as a component of the Vietnam War s agent orange chlorofluorocarbons (CFCs) polychlorinated biphenyls (PCBs the pesticides aldrin, chlordane, dieldrin, DDT, endrin, heptachlor, hexachlorobenzene, lindane, mirex, and toxaphene pentachlorophe-... 

An average size of continuous treatment plant for antifelt treatment of wool releases approximately 140 g/hour AOX. As an optimization of the process is possible only within certain limits, alternative processes for an antifelt treatment have to be chosen to substitute the chlorination process, for example, enzymatic processes, oxidative processes (KMn04, persulfate), or corona or plasma treatment. In many cases combinations with resin treatments are proposed. 

SUFFET The European community uses ozone as an alternative to chlorine, and I personally have a problem with the thought process that ozone does not produce other chemicals that might be as toxic or carcinogenic as those produced by chlorination. At present, we do not have good analytical methodologies to identify those ozonation products. So that is my basic difference with the European thesis in terms of using ozone and not too much chlorine. 

The relatively low conversions of the gaseous reactant in many processes, like the chlorination of toluene above, pose problems for the process design of such operations. One approach for the chlorine-toluene process would be simply to pass the C12-HC1 mixture through a downstream section of plant to separate the unreacted chlorine which would then be recycled to the reactor. In an alternative design chlorine might be passed from the first reactor into a second reactor in series, and then if necessary into a third reactor, and so on, as shown in Fig. 4.7. However, the problem arises because a bubble column with a low aspect ratio or a singleimpeller agitated tank behaves essentially as a well-mixed reactor (aspect ratio is... 

Epichlorohydrine Epichlorohydrine is an intermediate chemical with an annual production rate of 1.2 million tons (2007) worldwide and is used mainly for epoxy resins (80%) and elastomers [45], It is produced in a multistep process from propene using chlorine and base, releasing a major amount of chloride waste. An alternative process starting vice versa from glycerol was patented by several producers (Dow Chemical, Solvay, and Spolchemie) [46], Plants with a total capacity of approximately 100,000 tons/year are in operation, while plants with greater capacities ( 250,000 tons/year) are under construction [38], With them, approximately 25% of the worldwide production will produced from glycerol by the end of the decade. 

Rhone-Poulenc (now Rhodia) developed up to commercial scale an alternative process based on zeolite Beta [229,230] using acetic anhydride as reactant (Table 2.9). The original process used acetyl chloride in combination with 1.1 equivalents of AICI3 in a chlorinated hydrocarbon solvent, and generated 4.5 kg of aqueous effluent, containing AICI3, HCl, solvent residues and acetic acid, per kg of product. The... 

Alternatives for chlorinated hydrocarbon solvents, e.g. solvent-free processes, chemistry in water... 

The chloride must be purified by distillation to free it from unreacted solids and from impurities in the carbon. This is difflcult because of the hygroscopicity of ThCU and its high boiling point, 942°C. An alternative process [C6] reacts thorium oxalate with an excess of carbon tetrachloride and a small amount of chlorine as catalyst,... 

Iodine Trichloride. ci,i mol wt 233.39. Cl 45.60%, I 54.40%. IC[3. Prepd by adding finely powdered iodine to an excess of liq chlorine, which is then boiled away Thomas, Depuis, Compt. Rend. 143, 282 (1906) Booth, Morris, Inorg. Syn. 1, 167 (1939). Alternate process Birk. Angew. Chem. 4l, 751 (1928) Z. Anorg. Affgem. Chem. 172, 399 (1928) Wilke-DSrlurt. Wolff, ibid. 185, 333 (1930). 

Since HCl is formed in the ethylene process and is required for the acetylene method, the combination of both methods is commercially significant. Alternatively, the chlorine in the ethylene process can be replaced by hydrogen chloride, which is oxidized to chlorine by the addition of oxygen. 

Volume V addresses corrosion, environmental issues, and future developments. Chapter 14 covers the principles of corrosion and how to minimize corrosion in chlor-alkali operations, exemplified by case studies. Alternate processes for producing chlorine and caustic are outlined in Chapter 15. 

Chlorine is produced not only by the electrolysis of sodium chloride solutions but also from HCl, KCl, and other metal chlorides, by both chemical and electrochemical methods. The amount of chlorine from alternative processes is about 5.9% of the total world production. In the United States, it was about 4.0% of the total in 2002 [1]. Most of this chlorine was from the electrolysis of KCl in mercury or membrane cells (Table 15.1) and from HCl. Only small amounts are produced by the electrolysis of other metal chlorides. 

Other chapters deal with utility systems, cell room design and arrangement (with an emphasis on direct current supply), alternative processes for the production of either chlorine or caustic without the other, the production of hypochlorite, industrial hygiene, and speculations on future developments in technology. There is an Appendix with selected physical property data. 

The precipitation of basic calcium hypochlorites can be nsed to ranove calcium chloride. The excess calcium that is not associated with calcium hypochlorite can be precipitated by adding sulfate or carbonate, but this is less effective, and does not remove other impurities that remain in the calcium hypochlorite after the solution is evaporated. In either case, the conversion of lime to calcium hypochlorite is reduced by the amount of calcium salts that are removed from the process. In an earlier process, a concentrated lime slurry is chlorinated at 40-45 C to form crystals of hemibasic calcium hypochlorite. These are ranoved by filtration and snspended in a slurry of chlorinated lime. Chlorine is then added to make calcinm hypochlorite dihydrate crystals that are removed by filtration. The filtrate is mixed with lime to precipitate dibasic calcium hypochlorite. The dibasic calcium hypochlorite is ranoved by filtration, snspended in recycled liquor, and chlorinated to form crystals of calcium hypochlorite dihydrate. Throughout the process, seed crystals are used and the filtrates are recycled. " Alternatively, slow chlorination at 15°C is used to directly produce calcium hypochlorite dihydrate instead of the hanibasic compound in the first step. Dibasic calcium hypochlorite is made from the filtrate and processed as before. " ... 

After production, the thorium tetrachloride must be purified by fractional distillation to hberate it from unreacted solids and other impurities because of its high boiling point (942 C), the operation is difficult and an alternative process in which thorium oxalate reacts with an excess carbon tetrachloride with traces of chlorine as catalyst has been developed. The process is achieved batchwise in a vertical graphite reactor at 600°C and produces a pure sohd thorium tetrachloride in a single step ... 

Radiation from ultraviolet (UV) light sources is commonly used to destroy microorganisms in both drinking and wastewater filtration and is a particularly attractive alternative to chlorination as there is no addition of chemicals. UV radiation with a wavelength of ca. 255 nm penetrates the cell wall of the microorganisms where it is absorbed by the DNA (and RNA) to either prevent replication of the cell or induce death of the cell. To be effective the water to be treated must exhibit relatively low turbidity (e.g. low solids concentration) as higher turbidities can prevent sufficient penetration of the UV into the depth of the process stream. 

An alternative process is bulk-phase halogenation (74-76). Dry butyl rubber is fed into a specially designed extruder reactor and contacted in the melt phase with chlorine or bromine vapor. By-product halogen acids are vented directly, avoiding the need for a separate neutralization step. Halogenated rubbers comparable in composition and properties to commercial products can be obtained. 

Alternatives to Chlorine Gas in Circuit Board Manufacturing Photocircuits Corporation, in Glen Cove, NY, manufactures printed circuit boards for use in computers, cars, phones, and many other products. The facility formerly used chlorine gas in the copper etching process used to make circuit boards, but switched to sodium chlorate. This change reduced hazards to employees and eliminated an off-site vulnerability zone that encompassed 21,000 people. 

The most promising alternative to chlorination is ozonation. If the raw water being processed for drinking water contains bromide, the latter will be oxidized to bromate by ozone. The concentration of the bromate formed depends on the following parameters [31,32] ... 

AUyl chloride is produced by hot radical chlorination [route (a) of Topic 5.3.5). To achieve high selectivity of chlorine substitution versus chlorine addition to the double bound, high reaction temperatures of around 500 °C are needed. In addition, alternative process schemes using HCl as the chloride source under oxychlorination conditions are known. 

An alternate process, rarely used for commercial production, involves the reaction of ethylene with hypochlorous acid to form ethylene chlorohydrin. This chlorohydrin is then dehydrochlorinated with lime to produce ethylene oxide and calcium chloride. Major by-products of this process are 1,2-dichloroethane, bis-(2-chloroethyl) ether, acetaldehyde, trace acetylenes, and other chlorinated hydrocarbons. The reaction product is purified by fractional distillation. 

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