Patent GB-489979-A (GB)
Title: Improvements in or relating to the production of alkali metal and hydrogen peroxides
IPC: C01B15/023
Filed: 1937-06-15
Abstract: In the production of alkali metal and hydrogen peroxides by the reduction of an organic azo-type compound substantially insoluble in water to the corresponding hydrazo compound, and its subsequent re-oxidation to the azo compound, the reduction of a solution of the azo compound in a water-immiscible organic solvent being effected by means of an alkali metal amalgam in the presence of water, the reduction is effected while maintaining the solution and the water in an emulsion of the type in which the water is the disperse phase and the solvent for the azo-type compound the continuous phase.  The azo compounds are of the type R-N=N-R1 in which R and R1 represent the same on different aryl, substituted aryl or alkyl radicals.  Benzene is a suitable water-immiscible solvent.  An emulsion of the required type may be prepared by limiting the amount of water present during the preparation of the emulsion.  The proportion of water present may then be increased to some extent without altering the character of the emulsion by the addition of water with agitation. The shape of reaction vessel employed is of importance; the agitation of a mixture of given proportions of a solution of azo-toluene in benzene, water and sodium amalgam in a spherical two liter flask results in the formation of a "water-in-oil" emulsion and a rapid rate of reduction, using a vessel of the same capacity having straight sides and a conical bottom and charged with the same ingredients, an "oil-in-water" emulsion is formed and a very slow rate of reduction results; the withdrawal of some of the water changes the type of emulsion and the reduction to hydrazo-toluene is quickly completed. It is preferable so to conduct the agitation that there is a rapid circulation of the emulsion across the surface of the amalgam, e.g. by placing the stirrer off centre in the flask.ALSO:In the production of hydrazo compounds by the reduction of a solution of the corresponding water-insoluble azo compound in a water immiscible solvent by means of alkali metal amalgam in the presence of water, the reduction is effected while maintaining the solution and the water in an emulsion of the type in which the water is the disperse phase and the solvent for the azo compound the continuous phase.  The azo compounds are of the type R-N = N-R1 in which R and R1 represent the same or different aryl, substituted aryl or alkyl radicals. Benzene is a suitable water-immiscible solvent.  An emulsion of the required type may be prepared by limiting the amount of water present during the preparation of the emulsion.  The proportion of water may then be increased to some extent without altering the character of the emulsion by the addition of water with agitation. The shape of the reaction vessel is of importance; the agitation of a mixture of given proportions of a solution of azo toluene in benzene, water and sodium amalgam in a spherical two-litre flask results in the formation of a "water-in-oil" emulsion and a rapid rate of reduction. Using a vessel of the same capacity with straight sides and a conical bottom and charged with the same ingredients, an "oil-in-water" emulsion is formed and a very slow rate of reduction results; the withdrawal of some water changes the type o emulsion and the reduction to hydrazotoluene is quickly completed.  It is preferable so to conduct the agitation that there is a rapid circulation of the emulsion across the surface of the amalgam, e.g. by placing the stirrer off centre in the flask.