GB867227A - Improvements in or relating to the manufacture of hydrocyanic acid - Google Patents

Abstract

<PICT:0867227/III/1> Hydrocyanic acid is produced from a gaseous mixture of ammonia and a lower hydrocarbon of the aliphatic series by exposing it at sub-atmospheric pressure to the action of an electric arc discharge, supplying it at a rate of 120-350 litres (measured at N.T.P) per hour per kilowatt of power consumed by the arc. An oxygen free mixture of ammonia gas with gaseous lower aliphatic hydrocarbon, i.e. one containing 1-12 carbon atoms/molecule, preferably one containing 1-4 carbon atoms/molecule, is introduced through 17 into the reactor 15, which is provided with a double wall 16, a water jacket, and means to evacuate the interior thereof to a pressure of 40-120 mm., preferably 40-75 mm. of mercury and at a rate depending upon the hydrocarbon used. Thus for methane the rate is 270-350 litres/hour/kw of power consumed by the arc; 240-260 litres/hour/kw when the hydrocarbon contains 2 carbon atoms per molecule and 180-240 litres/hour/kw. When the hydrocarbon contains 3 carbon atoms or more. The mixture of ammonia and hydrocarbon may contain stoichiometric proportions of the reactants or a 10% excess of either one. The mixture is passed through an electric arc struck between electrodes 18 and 19 which are preferably obliquely disposed to one another and which rotate about their axes. The electrodes may be further drawn apart by mechanisms 7 and 71 which causes the arc to be extended through the gas. The rate of supply of the gases is such that they are subjected to the arc for only 0.04 to 0.001 seconds. The electrical circuit shown in the Figure is a device for maintaining a high voltage: amperage ratio, e.g. 400:1 to 1500:1 and also a temperature of 1100-1500 DEG C., preferably 1100-1300 DEG C., in the arc. After reaction the gaseous product containing hydrocyanic acid is removed from the reactor at 20 to be cooled and the acid recovered.