IL36158A - Process for the preparation of cyanogen - Google Patents

Description

Process for the preparation of cyanogen DEUTSCHE Shis invention relates to the manufacture of The German Specification DAS discloses a process for the manufacture of cyanogen by the reaction of hydrogen cyanide with nitrogen dioxide and water in the presence of a cupric This process gives satisfactory but the cyanogen thus formed contains an amount of nitrogen This has the drawback on the one the handling of this gas mixture on a technical scale is not free of danger because of the possibility that explosive mixtures are and on the other hand the recovery of the pure cyanogen entails considerable technical According to the German Specification cyanogen can be prepared by the reaction of hydrogen cyanide with gaseous oxygen in the presence of cupric salts and of oxygen activators at a precisely regulated in the acidic This process is difficult to perform on a technical scale owing to the required large excess of oxygen over the hydrogen which excess has subsequently to be separated from the and also owing to the required very precise control of the pH the cupric salt solution has to be prior to the to about in order to the speed of Comparative experiments have shown that in this anthrahydroquinone is used as an oxygen a special peak in the gas which is not present when is used instead of oxygen and points to a different course of the The cyanogen yield amounts to This yield is similar 3 addition of a change cyanogen As 1 of the German Specification the throughput of hydrogen cyanide is It cannot appreciably be accelerated by the addition of oxygen transfer agents or It is that the formation of cyanogen from hydrogen cyanide in the of cupric salts follows the reaction 2 4 2 I Shis reaction the cupric ions have unless the cuprous cyanide thereby formed can be oxidised at a sufficiently quick rate to cupric ions in accordance with the equation 2 4 HC1 2 2 ECU ΪΪ ne of cupric chloride hydrate used in accordance vith Example 1 of the Specification as a catalyst the amount required by equation I above for converting cyanide to cyanogen in the course of one fact shows the difficulty in the way of the cuprous ions in the process described by the aforesaid In contrast thereto it has been in accordance with present that cyanogen can be prepared in very good and within a toclinically satisfactory if the hydroge cyanide is reacted with hydrogen peroxide in the sulfate presence of cupric ferric salts are added to the reaction mixture they increase appreciably speed of the of the cuprous ions to cupric which controls salts It been found to be advantageous to add certain organic solvents to the reaction mixture in order to decrease the tendency of the hydrogen peroxide to It has been surprising to find that the relatively rapid decomposition of the hydroge peroxide to water and oxygen is completel inhibited by the presence of cupric and ferric ions and that the oxidation potential of the hydrogen peroxide can be utilized in favour of the of cuprous ions to cupric ions in accordance with equation possibly coupled with the of ferrous ions to ferric in accordance with the following equations 2 2 course of reaction is favoured by the addition of organic The addition of solvents has a favourable influence on the reaction of hydrogen peroxide above all at temperatures above since i inter the decomposition of hydrogen peroxide water and molecular organic solvents behave The use of such solvents gives the possibility to react the hydrogen which is dissolved in the organic solven in the aqueous catalyst solution and then to recover the solvent without further with The presence of ferric salts in an exclusively aqueous reaction solution accelerates the of the euprous ions to eu ric ions in accordance with e uations and to such that in this no decomposition of the hydrogen peroxide to water and molecular oxygen If the reaction is carried out in the organic solvent in the presence of ferric cupric these optimal reaction conditions achieve the best The reaction of hydrogen cyanide peroxide under these conditions proceeds so rapidly that the rate of throughput of the hydrogen cyanide is controlled merely by the rate of dissipation of the heat of In other the quicker dissipation of the heat of hydrogen cyanide can be The hydrogen cyanide is used in gaseous or liquid Even aqueous solutions can be used if they contain at least by weight of hydrogen Spent acid is also The cupric salts to be used in accordance with the as well as the corresponding ferric are contained in the reaction mixture in concentrations of up to by weight percentage of both It ia preferred to use the cupric and ferric ions in equivalent Preferred aggregate percentages of the salts are about by The cupric and ferric salts may be used in technical The iron salt initially added as ferrous salt since this will be oxidized in situ by the hydrogen The reaction is carried out at temperatures between 0 and preferably at The pressure may be chosen at Thus it is possible to carry out the process at atmospheric at a moderately or a moderately Of where atmospheric pressure is the vacuum not be so high Hydrogen peroxide is used in aqueous solution of by preferably by It is also possible to solutions of hydrogen peroxide in organic those obtained in accordance with the specifications of German patent applications P 18 02 and P 19 51 The hydrogen cyanide and hydrogen peroxide are reacted in equivalent calculated as pure and Organic either or suitable for use in the process of this invention are mainly alkyl esters of aliphatic alkyl Ethyl acetate and aeetate have been found to be especially saturated alkyl and aikylene especially tetramethyl have been found to be very The proportion of the organic solvent in the reaction mixture may amount to up to by preferably from The and salt solutions are mixed in a known in drum mixers or worm Where solutions of hydroge peroxide in organic solvents are an especially advantageous working procedure consists in introducing the hydrogen peroxide solution into an aqueous solution of the hydrogen cyanide An important advantage achieved by the process according to this as compared with known consists in fact that nearly pure free from oxygen and from nitrogen is obtained in very good the yield per volume per time is considerably increased on the hydrogen peroxide chromatography it contains only traces of hydrogen cyanide and Example 3 In an apparatus as described in Example g of B and g of are dissolved in 50 ml of methylene sulfone and the solution is cooled with ice A mixture of g of liquid hydrogen cyanide and of aqueous hydrogen peroxide is dropped into the flask in the course of 75 minutes and the temperature of the mixture is between 10 and Condensation of the produced gases yields of a condensate according to the gas contains of pure As a the condensate was to 0oG and the gas thus produced was again analysed by was found to be pure cyanogen and its amount which was of the calculated on the hydrogen peroxide The residue of g of hydroge cyanide and water Exampl 4 The process described in this Example is carried out in the apparatus diagrammatically illus in the accompanyin A solution of kg of and of in kg of water is fed through conduit into a reactor 1 whic provided heat exchanger Id and a stirrer Prom his reactor the mixture is fed by means of a pump 7 through conduit li stills 3 and circulated back to the reactor amounts of hydrogen cyanide and hydrogen peroxide moles of HCl 1 mole of are supplied through conduits la the cyanogen formed escapes through conduit and condenser where any hydrogen cyanide vapours entrained are and is withdrawn from the system through conduit In the still 2 the reaction mixture is liberated from dissolved cyanogen and unreacted residual hydrogen cyanide gases are returned to the reactor through conduit concentrated in the still 3 by the removal of both that introduced with the hydrogen peroxide solution and that formed by the and the concentrate is returned to the reactor 1 through conduits and The water vapours flow from the still 3 through conduit heat exchanger and conduit lo into a separator This apparatus is so as to in the course of 9 at a reaction temperature of constant with the aid of the heat exchanger coil Id in the reactor and at a gauge pressure of kgs of hydrogen cyanide and kg of aqueous hydrogen The output is 5950 of crude cyanogen gas by chromatographic is found to be composed of cyanogen nitrogen oxygen The yield is of the If the reaction mixture may be kept circulating through conduit heat exchanger 6 and conduit with the aid of pump with a view to keeping the temperature The reference numerals 5 to 5p in the figure denote Example With the apparatus in the manner described in Example kg of hydrogen cyanide and kg of aqueous hydrogen peroxide per hour are processed in the course of 6 hours in a solution of kg of and kg of in kg of and kg of methylene The reaction temperature is maintained at and the reaction mixture is kept under a pressure of product consists of 3770 liters of cyanogen gas containing of cyanogen and constitutes a yield of of the Example 6 In a flask as described in Example g of and of are dissolved in 100 g of water and the solution is maintained at under agitation while g of hydrogen cyanide and 102 ml of aqueous hydrogen peroxide are introduced in the course of 60 The gas by the reaction is analysed by gas It contains a constant proportion of of cyanogen and about of cyanogen The remainder of the gas consists of oxygen and hydrogen Example 7 In a flask as described in Example of and g of are dissolved in 100 g of tetraraethylene sul the mixture is maintained under agitation at and a mixture of g of hydrogen cyanide and ml of aqueous hydrogen peroxide is introduced in the The gas formed by the reaction analysed by gas chromatography and found to contain a constant proportion of of cyanogen and about of cyanogen The remainder of the consists of oxygen and hydrogen Example 8 In a flask as described in Example 25g of and of are dissolved in 50g of water and 27g of hydrogen cyanide and an equivalent amount of aqueous hydrogen peroxide ml of which correspond to of added in the course of 100 minutes while the ture of the reaction mixture is kept between and There occurs a development of gas which contains 97 of pure as ascertained by gas The process is carried out similarly as described in 4 in an apparatus designed for continuous A solution of of and of cupric sulfate in 30 kg of water is fed into a reactor For rapid mixing the solution is circulated by means of a pump from and back to the reactor through a pipe circuit which includes a heat Equivalent amounts of hydrogen peroxide and hydrogen cyanide mole of 2 moles of are introduced into the reactor through separate feed The cyanogen gas formed continuously escapes through a duct connected to the top of the The reaction mixture is pumped to a still where it is liberated from dissolved cyanogen and unreacted hydrogen cyanide the residual solution of copper and iron salts is concentrated S by the evaporation of The solution is then returned to the In course of some amount of hydrogen cyanide is consumed by being oxidized to and will in that have to be As described in this of were reacted with of aqueous hydrogen peroxide to form kghour of in hours of uninterrupted operation at 22 to The yield of cyanogen was of the calculated in The cyanogen contained of and of as described in Examples 4 and the copper and iron recovered for in the their recovery can be effected in a different manner the one described after the recovery of the cyanogen the copper and iron may be basic cupric carbonate end basic ferric Suitable precipitan for alkali metal carbonates earth metal Calcium carbonate is particularly suitable this The copper and iron are reconcentrated into the desired the by reaction with the corresponding insufficientOCRQuality

Claims (2)

1.

2 A process for the preparation of cyanogen by the catalytic oxidation of hydrogen the oxidation is effected by means of hydrogen peroxide in the presence of cyanide or A process according to Claim wherein the reoxidation of the cuprous ions in the course of the reaction is accelerated by the presence of ferric A process according to Claim wherein a salt with the same ion as that of the cuprie salt is A process according to Claims 2 or wherein a ferrous salt is initially to the other oxidised in situ to the corresponding ic t by the action of the hydrogen A process according to any of Claims 1 to wherein the uncontrolled decomposition of hydrogen peroxide is inhibited by the addition of organic solvents to the reaction A process according to Claim wherein tetramethylene sulfone is used as the organic A process according to any of Claims 1 to wherein the hydrogen cyanide is used as a liquid or an aqueous A process according to any of Claims 1 to wherein the hydrogen peroxide is used as an aqueous solution of ht A process according to any of Claims 1 to wherein the reaction is carried out at a temperature of and a A process according to any of Claims 1 to wherein the solution of the copper and when this iron remaining after the recovery of cyanogen is centrated and in the A process according to any of Claims 1 to wherein the copper salt when this the iron is or are precipitated om the reaction after the recovery of the by reaction with an alkali metal carbonate or metal and the precipitate is verted by reaction with the corresponding into the desired salt or salts to be used in the For the Applicants insufficientOCRQuality