DE489844C - Process for the production of alkali cyanides - Google Patents

Description

Process for the preparation of alkali metal cyanides It is known that by the action of ammonium formate or formamide vapors on heated caustic alkalis Alkali cyanides can be obtained.

It has now been found that this process proceeds significantly differently if one takes place under reduced pressure or in the presence of inert gases, such as. B. nitrogen, optionally with the addition of catalysts, especially those of the dehydrating type, works, with temperatures above 500 ' being used when working without catalysts.

The advantage of the new method is z. B. can be seen from the fact that in the above-mentioned known procedure, yields of hydrogen cyanide of only a few percent are obtained, which completely exclude a technical execution of the process, while working according to the present invention excellent yields, for. B. when applying a vacuum of 15 mm Hg yields of 7011/0 and more of the theoretically possible amount is obtained.

As has also been shown, alkali metal cyanides can also be used in good Yield obtained when using ammonium formate or formamide vapors instead of caustic alkalis act on alkali carbonates or mixtures of alkali carbonates and caustic alkalis Here, too, it is particularly advantageous if under reduced pressure or is carried out in the presence of inert gases. The water produced during the reaction and the carbonic acid are then removed very quickly from the reaction mixture.

Instead of formamide or ammonium formate, one can use the above also alkyl formate-ammonia or formic acid-ammonia mixtures use. A mixture of alkali metal formate and ammonium carbonate can also be used go out. When heated to higher temperatures, the alkali formate is initially formed and ammonium carbonate formamide, which converts into hydrocyanic acid with elimination of water, the then equilibrates with the alkali metal carbonate formed from the ammonium carbonate converts to cyanide with the release of carbonic acid and water. A special addition of alkali carbonate or caustic alkali is not required in this case. Under Under certain circumstances it is also advisable here to work at reduced pressure, however not necessary for the production of cyanide. The one released during the reaction Here carbonic acid obviously plays the same role as in the above-mentioned case the addition of inert gases. A mixture can also be used instead of ammonium carbonate apply ammonia and carbonic acid. Example z Formamide is used in a boiler evaporated at 150 'in vacuo. The fumes will then through a heated to 40o ° tower, in which a mixture of caustic soda and soda, the 0.5 a /, aluminitrine phosphate has been added is located. It forms Sodium cyanide, the erit-speaking, amounts of water and carbonic acid are sucked off. It is advisable to connect several such towers one behind the other.

Example 2 A mixture of caustic soda heated to 55o ° is added 1 part of methyl formate, 1 part of ammonia and 5 parts of nitrogen. It educates sodium cyanide, while aqueous methyl alcohol is distilled off.

Example 3 An intimate mixture of sodium formate and ammonium carbonate becomes quickly heated to about 5oo °, it forms sodium cyanide, while carbonic acid and water escape. Instead of ammonium carbonate, you can also use a mixture of Use ammonia and carbon dioxide.

Example q. Formamide vapors pass through at a vacuum of 50 mm Hg a melt consisting of 75% soda and 25% sodium cyanide, its temperature 55o ° is directed. With a yield of 85% and more on the applied Related to formamide, the formamide vapors combine with the soda to form sodium cyanide around while carbonic acid escapes. The remaining 15% formamide can partly be used as Formamide, partly recovered as ammonia.

Claims (3)

PATENT CLAIMS: 1. Process for the production of alkali metal cyanides by The effect of formamide or ammonium formate on caustic alkalis at elevated temperatures, characterized in that one under reduced pressure or in the presence of inert Gases works, optionally in the presence of catalysts, while working without catalysts, temperatures above 500 ° are to be used. 2. Amendment of the Process according to claim 1, characterized in that the caustic alkalis are partially or replaced entirely by alkali carbonates. 3. The method according to claim 1 and 2, characterized characterized in that the formamide, etc., by mixtures of alkyl formate or formic acid and ammonia or of alkali formate and ammonium salts or mixtures forming the latter replaced. q .. embodiment of the method according to claim 3, characterized that in the case of using mixtures of alkali metal formate with ammonium carbonate or with ammonia and carbonic acid, the addition of caustic alkalis or alkali carbonates is omitted.