Alternative processes hypochlorite

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. 

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. 

In the process the Ni-Cd batteries are first shredded and leached of the metal components in concentrated hydrochloric acid. This leachate consists of a solution of the dissolved metals, mainly Fe, Ni, Cd with small amounts of Co, Cu and Hg at a pH of approximately 0. The Cd is extracted with a commercial metal ion extractant, then stripped into an aqueous electrolyte solution from which cadmium is electrowon. After extraction of the cadmium, the leachate is contacted with sodium hypochlorite, at pH 4, to oxidise Fe(II) to Fe(III) and induce precipitation of ferric hydroxide. The filtrate now contains mainly Ni which is recovered by electrodeposition. The processing of 1000 kg of batteries will produce 200 kg of Ni metal and 159 kg of Cd metal and 500 kg of ferro-nickel scrap. An alternative process [33], is operated in China for the recovery of Ni and Cd from Ni/Cd batteries. 

The anhydride can be made by the Hquid-phase oxidation of acenaphthene [83-32-9] with chromic acid in aqueous sulfuric acid or acetic acid (93). A postoxidation of the cmde oxidation product with hydrogen peroxide or an alkaU hypochlorite is advantageous (94). An alternative Hquid-phase oxidation process involves the reaction of acenaphthene, molten or in alkanoic acid solvent, with oxygen or acid at ca 70—200°C in the presence of Mn resinate or stearate or Co or Mn salts and a bromide. Addition of an aHphatic anhydride accelerates the oxidation (95). 

Because of the simplicity of the manufactuting process it is cheaper than neutral calcium hypochlorite, and because of its higher av CI2 and better stabiHty, it is a superior alternative to bleaching powder [64175-94-6J. 

An alternative to the direct anodic oxidation of organic contaminants are the methods of indirect oxidation with the aid of oxidizers formed electrochemically in situ. These oxidizers (or mediators) can be obtained in both anodic and cathodic processes. Anodic agents are the salts of hypochloric acid (hypochlorites), the permanganates, the persulfates, and even ozone. 

Generally, although not exclusively, a scrubber with a recycle loop of the caustic scrubbing liquor is used cases of once-through scrubbing liquor operation do exist. The scrubber may be operated in batch, semi-batch or continuous mode with respect to the liquid. Process hazards exist in batch and continuous mode, the most significant of which is over-chlorination. Batch-wise operations leads to periodic high loads on the hypochlorite destruction unit. In order to even out these loads, and improve the process safety, a study of alternative treatment options has been undertaken. 

This chapter has therefore shown that cost minimisation of the treatment of hypochlorite effluent streams is achieved only through consideration of a wide range of process alternatives. The optimal solution for a given plant is dependent on a number of aspects, which include not only the rate and concentration of the stream as well as its required exit concentration, but also the configuration and operational mode of the caustic scrubber and any existing treatment system. 

Sodium hypochlorite is also manufactured by the electrolysis of sodium-chloride solution without a diaphragm (p. 97), the solution being less concentrated than that prepared by the chlorine process from sodium hydroxide, but free from the excess of alkali characteristic of that prepared by the older method.2 The process is carried out either in the apparatus designed by Kellner,3 or in that of Haas-Oettel,4 sodium chlorate being a by-product (v. infra). It is noteworthy that electrolysis of sodium-chloride solution with an alternating current also produces sodium hypochlorite.5... 

The formation of benzimidazoles by cyclization of aryl amidines can be accomplished in a number of ways, but is usually carried out under anhydrous conditions in the presence of a base. Thus cyclizations of (45 R = OH) induced by benzenesulfonyl chloride in pyridine or triethylamine generally give yields of greater than 60%. The more direct process of oxidizing the parent compounds (45 R = H) with sodium hypochlorite under basic conditions gives even higher yields (70-98%). Intermediates in these reactions are the )V-haloamidines (45 R = C1) a nitrene intermediate may be involved or merely dehydrochlorination with concomitant cyclization (Scheme 25). Alternative cyclization procedures include oxidation of the parent amidines (45 R = H) by manganese dioxide or lead tetraacetate and thermal... 

An alternative chlorination process involves the use of sodium hypochlorite (NaOCl) as the oxidant. Reactions with sodium hypochlorite are similar to those of chlorine, except that there is no caustic requirement for destruction of free cyanide in the oxidation stages. Alkali, however, is required to precipitate metal-cyanide complexes as hydroxides. The entire oxidation-precipitation process is a typical chemical oxidation precipitation process system. All chlorination equipment, chlorine compounds, etc., are commercially available (27). 

Answer The thermal homolysis of the weak oxygen-chlorine bond in r-butyl hypochlorite produces a r-butoxy radical that starts the chain. This radical will abstract a hydrogen atom from the benzylic methylene of 1-phenylpropane to give a resonance-delocalized benzylic radical, the most stable of all the possible alternatives. The propagation loop completes when the benzylic radical abstracts a chlorine atom from t-butyl hypochlorite and creates a r-butoxy radical to start the process over again. The products are 1-chloro-1-phenylpropane and r-butanol. 

Traditionally, long slow processes are carried out to obtain correct balance between the required properties of whiteness, absorbancy etc. in one hand and chemical damage on the other. The traditional process usually consists of chlorination, extraction of the chlorinated lignin by scouring in soda-ash and then bleaching preferably with alternate chlorite and peroxide stages or even hypochlorite bleach. Process details of conventional method are shown in Table 4.14. Lime boil is... 

Vi scose/cotton blends can be bleached either by batch method on j ig and winch or by a continuous process using J-Box [150]. Bleaching is done on a winch with sodium hypochlorite (2 g/1 available chlorine) adjusted to pH 10-11 with sodium carbonate, for 1 h at 25°C, or alternatively, with 5 g/1 sodium chlorite adjusted to pH 4 with acetic acid for 30 min at 80°C. Alternatively, the bleaching treatment may follow with alkaline hydrogen peroxide at 85 C. 

Chorine based oxidants (particularly the element itself and sodium hypochlorite) are used in a number of areas of the chemical industry. Chlorinated intermediates such as epichlorhydrin and chlorinated solvents have traditionally been extensively used in a variety of chemical processes. Environmental pressure, both consumer based and legislative, is currently being exerted, and will increase in the future, for the reduction, and probably eventual removal, of the use of these reagents and intermediates. H202 based technology is well placed to offer environmentally acceptable alternatives and is already used in many areas for this reason. 

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