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United States Patent Office 2,34,151

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United States Patent Office 2,34,151 Patented Apr. 18, 1944 2,347,151 UNITED STATES PATENT OFFICE 2,34,151. PRODUCTION OF YPOALOUSACD SOLUTIONS Chester C. Crawford, Berkeley, and Theodore W. - Evans, Oakland, Calif., assignors to Shee velopment Company, San Francisco, Califa corporation of Delaware No Drawing. Application April 30, 1940, Serial No. 332,604 8 Claims. (C. 23-152) The present invention relates to the prepara tain excessive quantitles of organic chlorides of tion of hypohalous acids, and more particularly the type of trichlorpropane and tetrachlorpropyl pertains to a novel process of preparing hypo ether. Similarly, the reaction between ethylene chlorous acid solutions which are substantially and these chloride ions containing aqueous solu free from halide ions, such as chloride ions. tions of hypochlorous acid, instead of producing Hypochlorous acid, usually in the form of its quantitative yields of ethylene chlorhydrin, also aqueous solutions, is employed in a relatively large results in the formation of ethylene dichloride. number of chemical and industrial processes. For In fact, even when the chlorhydrination of un example, in the production of organic halohy saturated organic compounds with such aqueOuS drins, a hypochlorous acid solution is interacted O hydrochlorous acid solutions containing halide With unsaturated organic compounds, which in ions is effected under the most optimum condi clude the olefins, such as ethylene, propylene, tions, the reaction products still contain relatively butylenes, amylenes, and the like, members of the high percentages of organic halides. acetylene series as acetylene, propine, butine, and It is therefore the main object of the present their homologues, diolefins, such as allene, buta 5 invention to provide a process for the efficient diene, isoprene, alcohols as cinnamyl alcohol, al and economic production of hypochlorous acids dehydes and ketones as acrolein, coumarin and which are free from or which contain only very ketenes, halides as vinyl chloride, ally bromide, limited quantities of inorganic halides. A fur allyl chloride, methallyl chloride, acetylene di ther object is to provide a process for the pro chloride, and the like, and their homologues and 20 duction of aqueous hypochlorous acid solutions analogues. Also, hypochlorous acid is sometimes which are Substantially free from chloride ions. employed for the manufacture of bleaching pow A still further object is to produce relatively con ders, particularly when it is desired to produce centrated aqueous hypochlorous acid solutions high-grade bleaching powders which are substan Substantially free from chloride ions. tially free from various undesirable impurities. It has now been discovered that aqueous hypo One of the Common methods of synthesis of a chlorous acid solutions containing halide ions may hypohalous acid includes the reaction between be effectively treated for the recovery of aqueous water and a halogen. For instance, the produc hypochlorous acid solutions substantially free tion of hypochlorous acid by the reaction of chlo from, or containing Only small and relatively rine and Water follows the equation 3) negligible concentrations of the halide ion, by HaO--Cla->HOC1-i-HC) subjecting such halide ion-containing solutions In order to neutralize the hypochloride acid to a distillation in the presence of a halogen gas. formed as a result of the aforementioned reaction, It has been further discovered that by distilling it is customary to employ an alkali, Such as sodium the aqueous hypochlorous acid solution contain or calcium hydroxide, or the like. The addition of 3. ing the halide ions, in the presence of a halogen such alkali neutralizes the hydrochloric acid, but gas and, preferably, in the presence of steam or of simultaneously forms an inorganic halide, which, another inert gaseous or vaporous substance, it is in most cases, is Water-soluble, thus forming an possible to obtain a substantially quantitative and aqueous hypochlorous acid Solution containing a highly efficient recovery of the hypochlorous acid greater or lesser concentration of halide ions. The 40 while leaving the inorganic halides in the undis presence of this inorganic halide in the hypo tied fraction. chlorous acid is frequently highly undesirable. The distillation according to the present in This is particularly true When the hypochlorous Vention is generally effected at a temperature of acid is employed for the chlorhydrination of un about 100 C. Although atmospheric pressures saturated organic compounds of the class defined may be employed, the distillation may also be hereinabove, it being noted that the presence of made undef reduced pressures, which will natu halide ions in aqueous hypochlorous acid Solu rally vary the degree of heating necessary for the tions tends to form undesirable by-products of distillation of the hypochlorous acid. Ordinary the type of organic halides or polyhalides, when distillation, whether in the presence or absence of such hypochlorous acid solutions are-employed as SO steam, however, is undesirable because at such one of the reactants in the above-mentioned distillation temperatures the reaction favors the chorhydrination reactions. For instance, when liberation of excessive quantities of chlorine gas alyl chloride is intimately commingled With an with the concurrent formation of hypochlorites aqueous hypochlorous acid solution containing and chlorates. The latter are naturally non-dis such free chloride ions, the reaction products con- tillable and, therefore, become a total loss so far 2 2,347,15i as the yield of hypochlorous acid is concerned free from or containing only a very low chloride In order to decrease this loss by conversion of ion concentration. This solution was quite stable. some of the hypochlorous acid into the corre Thus, a sample of a distillate produced according sponding hypochlorite and chlorate salts, the to the present invention and originally having a process of the present invention provides for the 0.73 M HOCl concentration, upon standing for maintenance of a relatively high halogen gas Con three days without any protection from light, etc., centration in the vapor phase evolved during the was found to have a 0.71 M HOCl concentration. distillation operation. For this purpose, the dis In other words, only 0.02 MI of the hypochlorous tillation is effectively realized by the distillation acid decomposed. On the other hand, hypochlo of the aqueous hypochlorous acid solutions con 0 rous acid solutions containing Sodium chloride Or taining halide ions (chloride ions), with the con like halides, when allowed to stand in the light, current passage of halogen gas through the dise decompose very rapidly so that it is frequently tillation zone. In fact, in order to obtain Sub necessary to prepare such chloride ion-containing stantially quantitative yields of the hypochlorous aqueous hypochlorous acid solutions immediately acid, it is desirable, if not essential, to employ a 5 before their utilization, and not to allow them to high concentration of the free halogen in the dis stand for any appreciable length of time. tillation or stripping column. Furthermore, it is Although the above disclosure was made With desirable to maintain the aqueous hypochlorous particular reference to the use of Sodium hy acid solution subjected to the distillation in ac droxide for the neutralization of the hydrochloric cordance with the process of the present inven 20 acid formed as a by-product during the prepara tion in an acidic state, preferably in the vicinity tion of the hypochlorous acid, it is possible to use of a pH of 3 or 4. Somewhat lower and higher the hydroxides of other metals, such as the other pH values may be employed without considerable alkali metals, the alkaline earth metals, and the impairment of the yields, as this will be obvious like. Naturally, the Salts formed during Such from the examples presented hereinbelow. HOW 25 neutralization will be different. However, when ever, in order to obtain optimum yields, it is best such salts are soluble in Water, the aqueous hya operate at a pH of below about 5, and prefer pochlorous acid solution will contain the unde ably within the aforementioned pH range in the sirable free chloride ions. Therefore, the proc vicinity of 3 and 4. w ess of the present invention is applicable to the The distillation according to the present in SO treatment of aqueous hypochlorous acid Solutions vention may be effected in a batch, intermittent containing water-soluble halide (e. g. chloride) or continuous manner. For example, the halide salts, and the recovery therefrom of solutions containing aqueous hypochlorous acid solution which are substantially free from the halide ions. may be fed continuously into a heat insulated The following examples will serve to indicate distillation or stripping column countercurrent to the operation of the present invention, it being a rising stream of steam and a halogen gas, Such understood that there is no intention of being as chlorine. In a preferred embodiment, the feed limited by any details of Operation, such as tem of the halide-containing solution may be made perature, pressure, concentrations of the starting at some intermediate point of the column, while material and of final distillate, etc., the inven the steam and the halogen gas are introduced 40 tion being co-extensive in scope with the appended substantially at or near the base thereof. The claims. undistilled fraction, comprising an aqueous solu Eacomple I tion of the inorganic halide or halides (such as the chlorides) present in the starting material An aqueous hypochlorous acid Solution prepared may be withdrawn intermittently or continuously 5 by the interaction of chlorine, water and Sodium from the bottom of the tower or column. The hydroxide, and therefore containing sodium chlo overhead fraction leaving the top of the column ride in Solution, was distilled in a four-foot strip may be treated (as by cooling) to separate the ping Column filled with 10 mm, glass beads. The halogen gas which may then be recycled back into column was surrounded with a steam jacket to and through the column.
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