DE2329894A1 - PROCESS FOR THE PRODUCTION OF ALKALINE HODANIDES - Google Patents

Description

Li. Vx ν. OV La.k \ jYes Il \; LJ \ JI J.Vi L> J. VERSUCHSBiHTiICBE DEK ßLF: GBAU-i ORSCHUNG

43 Gsson-f'rciy

Frillenclorfcr Siroße SSI Telephone (OiKlJ 20711

A 8 / S1- / 01.)

Process for the production of Alkalirlioö anid cn

The invention relates to a method for producing Alkali rhodanides from alkali cyanides ^ and Schv / efel.

Alkali rhodanides, in particular sodium rhodanide, can be manufacture by various known methods. (See Gmelins Handbuch der Anorg. Chemie, 8th edition (1967), sodium supplementary volume, Delivery 4, system no. 21). It is known to convert ammonium rhodanide with sodium hydroxide solution to sodium rhodanide to obtain. However, this process has the disadvantage that the ammonia formed is completely free at higher temperatures must be aborted and thereby the simultaneous formation of thiourea is possible.

However, it is also known to use lithium cyanide in aqueous solution to implement with elementary law. Despite the use of higher temperatures, this known method has only a minor one Reaction speed and is therefore not suitable for a technical production of liatrium rhodanide.

409882/0501

Έιϊ is wide ??. * B ska 73 nt, sodium cryarid in vnlför. ■■.; ·. «; ■: ■. · Solution with ITatriuui- or / ji ^: a; ioniuDpoi; v;" .: iil. t'icl uw ^ ursetivL-ZL, voraua ^ üsctat there are iai Rc: ai: tion! 3gc >>: Lsch sufficient Sebi / e ^ e-lwasGt'.estoffionen available «A Ii a chi, eil dieocs procedure iat that the atmosphere is contaminated by the exhaust air with low proportions of sulfuric oxygen and ammonia and that the separation of the Schucfc! ions becomes very difficult.

The invention is based on the object of creating an environmentally friendly and safe process for the production of alkali metal rhodanides from alkali metal cyanides.

According to the invention, this object is achieved in that elemental sulfur suspended in a water-miscible organic solvent and mixed with an alkali metal cyanide solution reacted at temperatures below the boiling point of the solvent, the organic solvent was distilled off from the reaction mixture and the alkali metal thiocyanate formed separates the distillation residue.

It has surprisingly been found that the reaction between the alkali metal cyanide and sulfur takes place using the heat of reaction without the supply of external heat with a significantly increased reaction rate, if it in the presence of an organic solvent which is miscible with water he follows. It is therefore beneficial to have the sulfur in one. Suspended ketone, aldehyde or alcohol. For example are acetone, methyl ethyl ketone, methyl alcohol or Propyl alcohol suitable solvents.

The heat of reaction released is very large. However, it has proved to be advantageous if one carries out the reaction at temperatures up to about 50 G ^0. In addition, the start reaction can be accelerated if the reaction is carried out with stirring or shaking

- 3 - 409882/0501

BATH ORIGINAL

Hold 50 ^{0 G.}

\ v.ii.l man au;!. ' do without cooling, it is advantageous to ν / ·:;. au wan the alkali-yanide solution of the vision in the organic solvent add drop by drop.

£ ,; ii-rfc is further advantageous when adding to the reaction mixture .Start the reaction a small amount of Alkalirhodanid in wüßrlger solution adds. In this way the disappears Grc'Jir.e between the organic and aqueous phase and it A uniform reaction mixture results. Also through the tie measure will speed up the reaction rate.

According to the process, no hydrogen sulfide is produced or other exhaust gases. The organic solvents used can be removed from the reaction mixture without loss cut off and regain. These solvents can therefore be used without polluting the wastewater Process used again.

Another advantage of the process is that the sulfur does not have to be finely ground. Step this way usually when handling powdered sulfur by irritation of the eyes, especially in poor weather conditions.

The method according to the invention can be particularly advantageous to render water-soluble metal cyanides harmless, preferably use the waste products of the hardening salts used for hardening iron products.

These waste products accumulate in the hardening units and are either processed or stored in safe landfills have to be. Recently it is due to the environmental protection regulations the transport and landfilling of these waste products have become very difficult. With the method according to the invention Alkali rhodanide can also be produced without difficulty from waste products with a low cyanide content. The so

- 4 - 409882/0501

BATH ORIGINAL

The cyanides shown are mainly used in the textile industry used to solatize some synthetic fibers before they are stained.

The method according to the invention is based on the examples explained in more detail:

example 1

22.5 parts by weight of sulfur are suspended in 50 parts by weight of acetone with stirring. 114 parts by weight of a 30% strength sodium cyanide solution are added to this suspension in small portions with constant stirring. The maximum reaction temperature here is 55 ⁰ C. After a reaction time of 100 min, the acetone is released from the. The reaction mixture is distilled off and obtained by crystallization from the aqueous distillation residue 54> 8 parts by weight of sodium rhodanide. This amount corresponds to a theoretical yield of $ 97.

Example 2

In 114 parts by weight of a 30 ^ strength Natriuracyanidlösung a suspension of 22.5 parts by weight of sulfur in 25 wt, parts by acetone is added slowly so that the reaction temperature does not exceed 50 ⁰ O increases with the addition. After the reaction mixture has been worked up according to Example 1, 55> 4 parts by weight of sodium rhodanide, that is 96 ^σ / ο of theory, are obtained.

Example 5

190 parts by weight of a 30% strength potassium cyanide solution, 50 parts by weight Methyl ethyl ketone and 44 »4 parts by weight of sulfur mixed and without shaking or stirring for 50 hours at normal temperature ditched. After the work-up of the reac

- 5 - 409882/0501

tion mixture.es according to Example 1 98 parts by weight of potassium iodoanide, that is 3b fo of theory.

Example 4

22% by weight of a 30% strength i-sodium cyanide solution, 40 parts by weight of sulfur and 55 parts by weight of propyl alcohol are mixed and left to stand for 65 hours 94 % of the theory are preserved.

Claims

409882/0501

Claims (6)

Claims Process for the preparation of alkali metal cyanides from alkali metal cyanides and sulfur, characterized in that elemental sulfur is suspended in a water-miscible organic solvent and reacted with an alkali metal cyanide solution at temperatures below the boiling point of the solvent, the organic solvent is distilled off from the reaction mixture and the alkali metal cyanide formed is removed separates the distillation residue. 2) Method according to claim 1, characterized in that the sulfur is suspended in a ketone, aldehyde or alcohol. 3) Process according to Claim 1 and 2, characterized in that the reaction is carried out at temperatures up to about 50 ^° C. 4) Process according to claim 1 to 3, characterized in that the reaction is carried out with stirring or shaking. 5) Process according to claim 1 to 4, characterized in that the alkali metal cyanide solution is added dropwise to the sulfur suspension in the organic solvent. 6) Process according to claim 1 to 5 » characterized in that a small amount of dissolved alkali metal anide is added to the reaction device at the beginning of the reaction. 409882/0501