Patent GB-449360-A (GB)
Title: Improvements in the manufacture and production of alkali metal peroxides
IPC: C01B15/023
Filed: 1935-05-30
Abstract: <PICT:0449360/III/1> Alkali metal peroxides are obtained by the oxidation with gaseous oxygen or air of organic compounds which contain in the molecule at least two hydrogen atoms which can be readily eliminated by oxidation in solutions containing caustic alkali or alkali metal alcoholate, the precipitated peroxide being separated, the oxidized organic compound being reduced again and the initial substances used up in the formation of the peroxide, e.g. water and alkali, being continuously or periodically replaced in the solution.  Suitable organic compounds are hydrazobenzene, indigo white and anthrahydroquinone.  Solutions in ethyl alcohol may be used.  The solution to be treated may be prepared with the aid of a mixture of at least two organic liquids, one of which has a good solvent power for the organic compound, e.g. benzene, xylene, tetrahydronaphthalene and ortho-dichlorbenzene, while the other has a good solvent power for caustic alkali or alkali metal alcoholate, e.g. the lower aliphatic alcohols.  With solutions having a low water content the compound NaHO2 is obtained while the presence of several per cent of water results in the production of Na2O2.8H2O.  The reduction and the replenishment of the alkali metal content of the solution can be effected simultaneously by treatment with an alkali metal amalgam; or part only of the reduction may be so effected, the reduction being completed by means which do not introduce alkali metal, e.g. by reducing with metallic zinc, electrolytically or catalytically with hydrogen.  The solution may be divided into two parts, each part being differently reduced or the methods of reduction may be employed consecutively on the same solution.  The solution should be allowed to stand between the oxidation and the separation of the precipitated peroxide.  After reduction with alkali metal amalgan excess alkali may be precipitated as chloride by treatment with gaseous hydrochloric acid, or as carbonate by treatment with carbon dioxide.  An alkaline hydrazobenzene solution may be brought into intimate contact with oxygen in a stirred oxidation container, the solution and precipitated peroxide then flowing through a wide pipe into an intermediate container which is kept full by an automatically actuated outlet valve.  The suspension then passes to a centrifuge for the separation of the peroxide.  The precipitate free solution flows through a reservoir into a stirred reduction vessel where it is contacted with liquid sodium amalgam. The solution and amalgam are separated by means of several tanks and filters, the reduced solution returning to the oxidizing container and the spent amalgam flowing to an electrolysis cell for regeneration.  Water may be replenished at a suitable point in the cycle, say after the centrifuge.  The oxidation vessel and intermediate container and their connections should be provided with devices to remove deposits.  As shown in Fig. 2, the intermediate container B of circular cross section is provided with a rotating frame a to which elastic scrapers are attached.  The connecting pipe to the oxidizing container O is kept free by means of a reciprocating open ring e and the connecting pipe with the centrifuge is kept free by a reciprocating ring f.  The automatic valve takes the form of a weight loaded pinch valve V.  The precipitated peroxide may be washed with alcohol and dried under reduced pressure at 30 DEG  C.