RU1775498C - Method of producing chlorine and hydroxides of potassium or sodium - Google Patents

Abstract

The invention relates to a technology for producing chlorine and potassium and sodium hydroxides by the diaphragm method and allows to improve the quality of electro-alkali by reducing the content of alkali metal chlorate and oxygen in it in chlorine). In the known method for producing chlorine and hydroxides of an alkali metal by electrolysis of aqueous solutions of an alkali metal chloride in a solid cathode electrolyzer with a filtering diaphragm, comprising periodically introducing iron group salts into the feed brine, hydrochloric acid is preliminarily added in the amount of 1-3 g / l (in terms of hydrogen chloride), and the metal salt of the iron group is introduced in an amount of 2-7 mg in terms of metal ion per 1 g of active chlorine in terms of alkali metal hypochlorite to the content in the feed with a salt of a metal salt of an iron group of 5-20 mg / L upon reaching a concentration of active chlorine in the anolyte of 1.0 g / L. 2 tab. cl

Description

The invention relates to electrochemical production technology, in particular to the production of chlorine and sodium and potassium hydroxides by the diaphragm method.

The aim of the invention is to improve the quality of the alkali obtained by reducing the chlorate content in it and reducing the oxygen content in chlorine.

The proposed method is illustrated by examples.

EXAMPLE 1 A feeding brine containing 310 g / l NaCl and 1.5 g / l hydrochloric acid is fed into the anode space of a chlorine diaphragm electrolyzer. At a concentration of active chlorine of 1.2 g / l, nickel chloride in an amount of 5.0 mg per 1 g of active chlorine is introduced into the feed brine

when it is contained in a feed brine of 10 mg / l. Prior to the introduction of the catalyst, the electro-alkali contained NaOH - 160 g / l, No. СЮз - 0.6 g / l, 02 - in chlorine gas 3.0%. Electrolysis is carried out at a current density of 0.15 A / CNi2 using an OPTA and a steel cathode. The diaphragm surface was 40 cm2. The composition of the resulting alkali NaOH - 160 hl, NaCIOs - 0.3 g / l, chlorine gas contained 2.9% oxygen.

Example 2. Similar to example 1, but the feeding brine containing 1.5 g / l hydrochloric acid and 350 g / l KCI is fed into the anode space. The composition of the resulting KOH electro-alkali is 180 g / l, KSyuz - 0.29 g / l . The oxygen content of chlorine gas is 3.0%.

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14 Yu

The electrolysis indices during the introduction of the process at other values of the parameters of the claimed method are given in Table 1. The concentration of alkali obtained, the electrolysis temperature, and the content of active chlorine in the anolyte are as described in Example 1.

As can be seen from the data presented, when using the proposed method, a regulated content of sodium or potassium chlorate (0.35 g / l) in alkali is achieved and the content of 02 in chlorine does not increase. Moreover, the goal is not achieved beyond the stated parameters, so with a decrease in the concentration of hydrochloric acid less than 1 g / l and the amount of catalyst less than 2 mg per 1 g of active chlorine at a catalyst concentration in the feed brine of less than 5 mg / l, the regulated content is reached chlorate ions in electro-alkali (see experiments 1, 5). With an increase in the concentration of hydrochloric acid above 3.0 g / l, the number of catalysts more than 7 kg per 1 g of active chlorine with a catalyst concentration in the anolyte of more than 20 mg / l, the quality of the electro-alkali does not improve (see experiments 12,13), and the yield is alkali flow and the chlorine content of the chlorine gas is reduced.

The necessity of introducing a catalyst at a concentration of active chlorine of more than 1.0 g / l is confirmed by the data given in Table 2.

As can be seen from the data given in this table, with a lower content

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5

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5

active chlorine, the use of salts of the iron group is not effective, due to the low content of sodium chlorate in the electro-alkali, which makes the introduction of a catalyst not effective (see experiment 1, table 2).

Thus, the application of the claimed method will allow, on the one hand, to improve the quality of the obtained products of electro-alkali and chlorine gas and, on the other hand, will save catalysts (metal salts of the iron group) by reducing their supply to the cell.

Claims (1)

The claims A method for producing chlorine and potassium or sodium hydroxides by electrolysis of an aqueous solution of the corresponding chloride in a solid cathode electrolyzer with a filtering diaphragm, comprising periodically introducing iron group metal salts into the feed brine, characterized in that, in order to reduce the content of chlorate in hydroxide and oxygen in chlorine, Hydrochloric acid is preliminarily introduced into the feed brine in an amount of 1-3 g / l in terms of hydrogen chloride, and when the concentration of active chlorine in the anolyte reaches 1.0 g / l, the group metal salt is introduced 2 to 7 mg g of iron in the feed brine, calculated as a metal ion per 1 g of active chlorine, until the metal salt of the iron group is 5-20 mg / l in the feed brine. Table 1 table 2 The amount of products obtained when introduced into the cell in mg (in terms of metal) of nickel chloride per 1.0 g / l of active chlorine. The concentration in the NlClz brine is 15 mg / L; the HCI is 2.0 g / L.