CS258640B1 - A method of producing high purity sodium sulfide - Google Patents

Abstract

The principle of the method consists in the conversion of sodium hydroxide into sodium sulfide in the following stages: preparation of sodium sulfide, conversion of sodium sulfide into hydrosulfide with the simultaneous decomposition of thiocomplexes into iron sulfides, filtering of iron sulfides and conversion of iron-free sodium hydrosulfide into sodium sulfide by the action of sodium hydroxide withdrawn from the end absorber. The sodium sulfide solution is evaporated under vacuum to remove water to give a white product.

Description

3 25 8B 40

The invention relates to a process for the production of high purity sulphide sodium. Accordingly, sodium sulfide can be produced with a low content of colored compounds, for example iron compounds, especially thiocomplexes.

According to German Patent Specification No. 499,417 of the British Patent Specification No. 284,958, the thiocomplex of iron in sodium sulfide releases skyanides and decomposes with zinc powder or some zinc salts (NSR Patent No. 414 970, Japanese Patent Specification No. 1702/51). , copyright USSR 33141). While reacting with cyanides, white sodium sulfide is obtained but the iron is not removed. The decomposition of the thiocomplex zinc is uneconomical.

The iron thiocomplex formed in sulifidesodium with a concentration above 23 percent by weight decomposes to iron sulphide by diluting sodium sulphide below 20 per cent by weight. The ferrous sulphide precipitates in a finely-filterable form. Dilution of the concentrated sodium sulphide with water results in an increase in the energy costs of water evaporation. The purification of sodium sulfide by means of alcohols, which is the subject of U.S. Pat. No. 2,838,074 and U.S. Pat. No. 1,016,242, 1,068,677, 1,127,335.

According to U.S. Pat. No. 2,662,000 and U.S. Pat. No. 1,300,909, high purity sodium sulphide is only made from sodium hydroxide at a concentration of up to 30 per cent by weight through hydrosulfide. In accordance with the present invention, sodium sulphide with a low content of iron thiocomplexes from sodium hydroxide at concentrations above 30 percent by weight can be produced.

The production process consists in firstly saturating the sodium hydroxide with hydrogen sulfide to form sodium thiocomplex in a dark red color, and then reacting it with hydrogen sulfide in a sulfide-to-hydrogen sulfide molar ratio of 0.5 to 1, with the thio-complex being reacted. it turns into iron sulfides. The reaction product is freed from sulfides by filtration, and the filtrate is treated with sodium hydroxide at a molar ratio of sodium hydrosulfide to sodium hydroxide of 1: 1. After evaporation of the water, sodium sulfide is obtained containing 10 to 10% by weight of sodium sulfide. 30 ppm.

The following reactions are under way: 2 NaOH + H2S - NazS + 2 H2O + 51.4 kj

At a concentration of sodium sulfide above 23% by weight, these thio-complexes are formed in the presence of iron ions | SøV * (OH. 2 Η ^ ΟI— t'ÍJ · u

On. <

HJO

1 FeA> - (GHH OH, (OH) ;,

NazS H2S - 2 NaSH + 40.7 kj

NaSH + NaOH - Na 2 S + H 2 O + 5.3 kj

The iron compounds are the starting materials and intermediates in the sodium sulphide due to the corrosion of the process equipment. Also the sulphide is itself corrosive and its corrosive effect increases with temperature increase. It is therefore advantageous to work at the lowest temperatures allowed by the process to produce sodium sulfide. The iron content of the sodium sulfide prepared by the conventional method is in the range of 200 to 350 ppm. The compounds are dark colored and sodium sulphide with the aforementioned iron content cannot be applied for demanding target products.

The temperature at which sodium hydroxide or sulfide can be reacted with the hydrogen sulfide is dependent on the concentration of the starting sodium hydroxide. By regulating the temperature, the formation of sodium sulphide crystals is prevented before the iron thiocomplete is decomposed and the iron sulphide is filtered off. Sodium hydroxide is heated to at least 60 ° C before contacting it with hydrogen sulfide, and the heat-reacting mixture is allowed to rise to a maximum of 150 ° C under the influence of the reaction heat.

Crystallization temperatures of the aqueous solution

Claims (2)

In fact, sodium sulfide 258S40 S increases with increasing concentration. One percent by weight of sodium sulfide in an aqueous solution of sodium hydroxide at a concentration of 38.4 per cent by weight has a crystallization temperature of 58.5 ° C. An aqueous sodium sulfide solution concentrating 40 percent by weight with a crystallization temperature of 94.5 ° C. The 43% w / w hydrosulfide has a crystallization temperature of 12.5 ° C. The temperature increases with a decrease in the sodium hydrogen sulfide content and the sodium sulfide increase. Due to the decrease in the crystallization temperature of the reaction solution with the increase in the sodium sulfosulfide content, the conversion of the sodium sulfide to the hydrosulfide can be carried out at temperatures below 100 ° C. The absorption of hydrogen sulfide in sodium hydroxide is advantageous in two or three consecutive sequestered sorbers, so that the hydrogen sulfide is reacted quantitatively. The conversion of sodium hydrosulfide to sulfidium is preferred by the sodium hydroxide stretched from the end absorber. In fact, the sodium hydroxide version in the end absorber is low due to the conversion of sodium hydroxide in the first or first absorption. The process for producing high purity sodium sulfide can be carried out in a batchwise or continuous process. By way of illustration, examples are given but are not intended to limit the invention. EXAMPLE 1 Two moles of aqueous sodium hydroxide at a concentration of 42 percent by weight were heated to 60 DEG C. in a loading working absorber and brought into contact with one mole of hydrogen sulfide. Within three hours, the temperature in the absorber increases to 120 ° C and is maintained at this temperature until sodium hydroxide is converted to sodium sulfide. The gases from the first absorber are contacted at the second end absorber with sodium hydroxide at a concentration of 42 per cent by weight. They remove hydrogen sulfide residues from the gas at the end absorber. The sodium sulfide solution formed in the first absorber is treated with hydrogen sulfide in a molar ratio of sodium sulfide to sulfuric acid for one hour over a period of 5 hours. During this period, the temperature of the reaction mixture is gradually reduced to 90 ° C. The aqueous sodium sulfosulfide solution is filtered to remove iron sulfides. The filtrate obtained is then treated with sodium hydroxide withdrawn from the second end absorber. An aqueous solution of sodium sulfide is obtained, from which water is evaporated under a pressure of 670 Pa. Solid white sodium sulfide with an iron content of 10 ppm was obtained. Example 2 The procedure is the same as in Example 1, with the difference that three consecutive absorbers are operated. The gasses from the first and second absorbers are absorbed by the third absorber. An aqueous solution of sodium hydrosulphide is withdrawn from the second absorber, and the sulphide of the iron is removed by filtration. The filtrate from the second absorber is contacted with sodium hydroxide withdrawn from the third, end absorber. OBJECT OF THE PREPARATION OF HIGH PURITY OF SODIUM SULFIDE characterized in that the 30% to 60% by weight hydrogen hydroxide is heated to at least 60 ° C and contacted with hydrogen sulfide, preferably in the sodium hydroxide molar ratio. to 2: 1 hydrogen sulfide, at a maximum temperature of 150 ° C, the aqueous sodium sulfide solution is reacted with hydrogen sulfide at a molar ratio of sodium sulfide to hydrogen sulfide 1: 0.5 to 1 with a gradual reduction in the reactor to 100 ° C, in the same reactor or in the second reactor, the gases from the first or the two reactors are fed to a final reactor in which sodium hydroxide of the same concentration as sodium hydroxide in the first reactor is contacted; or a mixture of sodium sulfide and sodium hydrosulfite is filtered off from the iron sulfide precipitate and the filtrate is treated with sodium hydroxide solution from the final absorbance of the hydrosulfide molar ratio. sodium hydroxide 0.95 to 1.05, the resulting sodium sulfide solution is filtered off, the water is evaporated to give a solid white sodium sulfide.