SU922070A1 - Method for purifying solution of alkali metal hydroxite from chlorate - Google Patents

Description

(SM METHOD FOR CLEANING ALKALINE METAL HYDROXIDE SOLUTION FROM CHLORATE.

I

The invention relates to a method for the purification of an alkali metal hydroxide solution from chlorate, obtained by electrolysis of a solution of the corresponding alkali metal chloride by the method with a filter diaphragm.

Commercial solutions of alkali metal hydroxide with a concentration of 4250 wt.% Contain 0.3% chlorates.

The high content of chlorate prevents the use of such hydroxide in the production of chloroprene from butadiene. .

A known method for the decomposition of chlorate in a concentrated solution of sodium hydroxide obtained by Metering with a diaphragm filter is that dithionites and a small amount of divalent and ferric iron compounds are added to the solution, and neo-acid (i.e. gas not absorbed and dissolved in the solution. Dites are used; sodium ionite in an amount of 3 moles and 1-10 ppm of divalent and ferric ions, which is enough to decompose 1 mole of chlorate. The process is carried out at a temperature above 1.

The disadvantage of this method is the contamination of the alkali metal hydroxide solution being treated with compounds of bivalent and trivalent iron.

10 and dithionite reducing agent, which, in turn, requires an additional operation to remove them from solution. ..

Claims (2)

5 The closest in technical essence and the achieved result is a method of cleaning an alkali metal hydroxide solution from chlorate, which consists in reducing the latter with hydrogen at and above and an increased pressure (1.76 kg / cm) in the presence of a ruthenium catalyst 2. The disadvantages of this method are the lack of a process associated with the need to treat an alkali solution at elevated temperature and pressure, as well as the use of a scarce ruthenium catalyst. The purpose of the invention is to simplify the process and eliminate the use of scarce components. This goal is achieved by cleaning the solution of alkali metal hydroxide from chlorate by reducing the latter with hydrogen, at elevated temperature and in the presence of one or more organic compounds selected from the group of butene diol, dichlorobutene, citric acid as a catalyst. The reduction of chlorate is carried out at 5-55 ° C. In the practical implementation of the method, it is advisable to carry out the reduction by electrolytic hydrogen obtained in the same process of electrolysis of an alkali metal chloride by the method with a filter diaphragm in which an alkali metal hydroxide solution is obtained. At the same time, the amount of electrolytic hydrogen spent on processing the volume of a solution of commercial 2–50% alkali, equivalent to 1 t of 100% alkali, is approximately 280 nm, i.e. the amount of hydrogen that is formed during electrolysis by the method with a filter diaphragm simultaneously with 1 ton of alkali. Example 1. 1.6 g butandiol per 1 l of alkali solution (2.59 kg per 1 ton of caustic soda) are introduced into a solution of cauditic soda containing i NaOH and 0.15% MaС10 and then treated with electrolytic hydrogen at 50 ° C, consumption hydrogen 110 nm per 1 ton of alkali solution (250 nm per 1 ton of caustic soda) for hours. The content in the sodium hydroxide solution after treatment,%: sodium chlorate is 0.017; butendiol O, 1; NaCl 0.1. Example 2. 1.5 g, 3, -Dichloro-1-butene per. Are introduced into a solution of caustic soda containing CAA oCaOH and 0.33 MaCtO. V liter of alkali solution (2.35 kg per 1 t of 100% caustic soda) and then treated with electrolytic hydrogen at a hydrogen consumption of 20 nm per 1 t of alkali solution (55 nm per 1 t of caustic soda) | within 1.3 hours. The content in the sodium hydroxide solution after treatment,%: sodium chlorate is 0.013; unwashed 3, dichloro-1-butene 0.1; HaCtO ,. Example 3. Into a solution of caustic soda containing 4 NaOH and 0.13 (faCtO,) 1.8 g of citric acid are added to 1 l of alkali solution (2.82 kg per 1 ton of caustic soda) and then treated with electrolytic hydrogen at 50 ° C, consumption of hydrogen 170 nm per 1 ton of alkali solution (387 nm per 1 ton of caustic soda) for 7.2 hours. Content in A4% sodium hydroxide solution after treatment,%: sodium chlorate 0.021; sodium citrate 0.12 ; -NaCt 0.1. Example: 0.5 g butandiol, 0.5 g 3, -Dichloro-1-butene and 0.6 are added to a solution of caustic soda containing kk% NaOH and -0.13 NaCIOj. g of citric acid in 1 liter ra alkali solution and then treated with electrolytic hydrogen at 50 ° C, hydrogen consumption 120 nm per 1 ton of alkali solution (270 nm per 1 ton of caustic soda) for 5.5 h. Content in sodium hydroxide solution after treatment: sodium chlorate 0.015; mixture These organic compounds 0.11; NaCt The presence of these organic impurities does not prevent the use of the product in the production of chloroprene. Deeper cleaning of chlorate is impractical. As the temperature rises, the hydrogenation time decreases, however, in this case, the concentration of organic catalysts with hydrogen increases. Therefore, the temperature of hydrogenation should not exceed EO-YuO C. Below C the time of hydrogenation increases dramatically. The optimum process temperature is 50i: 5 ° C. The production of chloroprene satisfies the content of sodium chlorate in a solution of caustic soda not more than 0.025%. The proposed method is simple, since it is carried out under normal hydrogen pressure and at a temperature lower than that known. At 59,220, the process does not require a deficient ruthenium catalyst. Claim 1. The method of purifying an alkali metal hydroxide solution from chlorate by reducing the latter with hydrogen at elevated temperature and in the presence of a catalyst, is due to the fact that, in order to simplify the process and eliminate the use of scarce components, use one or more organic compounds selected from the group: butendiol, dichlorobutene, citric acid. 2. The method according to p. 1, about tl and h ayusch And with the fact that the recovery of chlorate is carried out at 45-55 0. Sources of information taken into account at the time of the examination 1. Application of Japan No. 53-70988, cl. From 01 D 1/28, published 1978 2. French patent number, class, C 01 D 1/28, published. 1977.