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UNITED STATES ATENT OFFICE 2,648,596 SODIUM SUPEROXIDE PRODUCTION William H. Schechter, Zelienople, Pa. Application August 5, 1950, Serial No. 177,977 10 Claims. (0]. 23-.9-184). 1 2 This invention relates 'to sodium superoxide, streamof air '"or . Although in that way NaOz. it is possible to prepare , or The alkali metal oxides are useful for various tetroxide, the literature on the subject shows that, purposes. For example, (NazOz) curiously enough, the corresponding oxide of so and potassium superoxide, or tetroxide (K204), dium, i. e., NaOgz, has never been prepared by release oxygen in contact with moisture. They combustion or ‘metallic sodium in air or oxygen, have ‘therefore been used extensively in breathing Or by air or oxygen oxidation of sodium perox apparatus and for maintaining the atmosphere ide (NazOz), which is the highest oxide of so in closed spaces respirable, as in submarines or dium that has beenprepared heretofore by com in other places where the atmosphere vwould bustion of sodium in an oxygen-containing at otherwise become de?cient in oxygen. Those ox~ mosphere. Consequently, this desirable sodium ides are particularly adapted to such purposes be superoxide has not been available as a substitute cause when they are brought into contact with for the foregoing oxygen-evolving compositions. exhaled air the moisture contained in it reacts A primary object of this ‘invention is to pro with the oxide to liberate an amount of oxygen vide sodium superoxide. equivalent to that consumed in respiration, and Another object is to provide a method of pro at the same time the ‘oxide also ?xes the exhaled ducing sodium superoxide in admixture with low carbon dioxide. For this reason thesesubstances er oxide of sodium that issimple, easily per are especially adapted for use in breathing ap formed, and adapted to provide products contain paratus of the self-contained type. ing desired content of available oxygen. Sodium peroxide has been used on a very large 'Yet another :object is to provide a simple and scale for such purposes. However, there is theo e?ective method of making substantially pure retically available from it at N. T. P. only about NaOz. 145 cc. of oxygen per gram. Mixed oxides of so I have discovered, and it is upon this that my dium (NazOz) and potassium (K204) have there invention is in large part predicated, that if in fore been used to some extent because the form steadof followinglprior practices of producing supplied commercially gave a greater yield of the alkali metaloxidesby combustion in an oxy oxygen per unit weight than is available from gen-containing atmosphere at normal ‘pressure, NazOz, namely, about 190 to 200 cc. per gram. or at pressures r-near atmospheric, metallic so More recently, substantially “pure potassium , dium or sodiumperoxide be heated in a ‘bomb, tetroxide has been used for these purposes because ' 1. e., a closed pressure container, to an elevated there is theoretically available from it 236 cc. of temperature in (contact with oxygen under pres oxygen per gram. ' sure substantially above‘atmospheric, the super Obviously, it "is advantageous and desirable ‘to oxide is‘formed. If, however, thetemperature be obtain from such materials as great a yield/as raised while subjecting the sodium peroxide to possible of oxygen per unit weight. Thus, vwhere high oxygen pressure, the peroxide is progres space is important, the greater the yield per unit sively converted to- the superoxide by continued weight the more compact the device ‘using it. exposure at a given temperature and pressure, Also, on the same basis a given amount of the or by increase in oxygen pressure at given tem oxygen-exchanging material will have longer ef perature and time of exposure. Under proper fective life. Again, in a self-contained breathing 40 conditions substantially pure sodium superoxide apparatus the weight and compactness ‘factors can be ‘produced in this way. Or, if the pure are of importance, to minimize ‘fatigue of va Work superoxide is ‘not needed, mixtures of‘ Na2O2~NaO2 er using it, and accordingly the ‘higher the ‘oxy having greater contents of available oxygen than gen-evolving power of such a. substance the less 45 Naz'oz, ‘K02 or mixtures of them maybe pro the weight required in a canister designed to give duced by the method of the invention. a predetermined working-time. The content of sodium superoxide ‘in products Theoretically, sodiumsuperoxid'e, NaOz, would made by my-method'may be determined readily be better than sodium peroxide, potassium by treating a weighed-sample with a solution that tetroxide, or their mixtures as used heretofore, - is 2M with-respect to "HCl and 1M in ferric chlo because at 100 per cent purity it should liberate ride. From the corrected volume of O2 evolved 305.6 cc. ‘of oxygen per gram at vN. T. P. How per gram of product the weight per cent of NaOz ever, .oxides of sodium and potassiumdare pro is then calculated'by the formula duced by oxidation of therespective metals, com monly by burning the metal in contact with a 65 2,648,596 4 The numerator represents the cc. of 02 per gram peroxide is ?nely divided and presents larger beyond that required for pure NazOz, and the de surface area. The best conversions have been nominator the difference in cc. of O2 evolved per obtained with sodium peroxide made by atom gram between pure NaOz and NazOz. ization of molten metallic sodium in accordance The factors described above have been demon with U. S. Patent No. 2,405,580 to C. E. Jackson. strated by numerous tests and they are illustrated This peroxide is of very low bulk density and by the following data of runs made in a high possesses very high exposed surface area; it was pressure bomb of about 180 ml. capacity: used in the runs represented in the drawing. The graphs show how conversion of Naif): Product 10 to NaOz can be controlled in 4 to 6 hour runs according to variation in temperature and pres 1d/[tarting1ateria Press,p. s. i. Tgrapq. Tl‘iime,rs. sure. Thus, 90 per cent conversion is to be had cc. Oz/g'm. Pggzgzlt at 1450 p. s. i. 02 pressure at 350° C., or by heating at 400° C. under about 1310 p. s. i. 02 NazOz ______.. 1, 500 450 12 277 82. 5 15 pressure. Likewise, substantially pure NaOz Nero: ______2,000 450 12 281 84. 5 NazOz ______2,000 500 2 263 73.5 (more than 99% purity) is produced at 1800 N m0: ______2, 000 500 4. 75 289 89. 5 p. s. i. and 400° C. Where lower contents of NaOz in Na2O2 su?ice for particular purposes I have found also that the reaction can be ac they may be had at lower pressures and tem celerated by mixing the Na2o2 with a wide va peratures, as appears from the graphs. riety of metallic oxides that act to catalyze the As further showing'how the pressure may be reaction. Thus at 2000 p. s. i. oxygen pressure. lowered through increase in pressure, at 450° C. 500° C., and two hours exposure in the small an oxygen pressure of 1700 p. s. i_. suf?ced to bomb conversions of Na2O2 to 70 per cent NaOz produce 97 per cent NaOz in 4 to 6 hours. ' were obtained with M003, V205, ‘CdO, F9203, 25 Tests have shown high purity sodium Super CrzOs, NizOs, MgO, CO203, C110, TiOz. Of oxide made in this way to ‘be satisfactorily stable these, CdO and TiOz have given optimum re at 65° C. (150° F.) so that its stability at the sults. Thus, with 1.2 per cent by weight of CdO maximum temperaturesto which it Would nor 88 per cent of NaOz was produced from NazOz mally be exposed, even in the tropics, is assured. at 2000 p. s. i. 02 and 500° C. after four hours. It tends to lose oxygen very slowly at 100° C., About 0.6 per cent of CdO has been found to however. - exert the optimum effect. The effect of T102 NaOz, or mixtures with NazOz, made at 450° (0.68 per cent by weight of the Nazoz) is shown C. is generally fused solid. It may be granu by the following data: lated or ground to prepare it for use. Operation at 400° C. causes some shrinkage of the original Product charge after 5 hours, and substantial shrinkage Press. Temp. Time after 24 hours. At 350° C. and lower there is 110 Catalyst p. s. i.’ ° 0. ’ Hrs.’ P _ t appreciable shrinkage during the conversion. cc. 021cm. Gwen '° NaCz Thus the bulk density of the product can be 40 controlled by the temperature and the duration None ______2, 000 500 4 266 75. 5 of the run. It is affected also by the pressure. TiOz ______2, 000 500 4 289 89. 5 Lower temperatures than those given above by way of exempli?cation may be used but re Runs made in a larger bomb, or autoclave, quire longer times and higher pressures, and the have shown that higher percentages of sodium 45 conversion is generally less. Thus, at 200° C. superoxide, and even essentially pure NaOz can and 3275 p. s. i. oxygen pressure 11 per cent of be obtained at lower temperatures than in the NaOz is obtained after 100 hours. , ' ' ' small bomb. This is due, I believe, in part to Similarly, metallic sodium can be converted reduced corrosion of the bomb material, or liner to NaOz by treatment, at high temperatures and material, and in part to the fact that my work 50 high oxygen pressures. For instance, at 180 shows the reaction Na2O2—>NaO2 to be exo Atm. abs. O2 pressure and 300° C. metallic Na thermic. The latter factor acts in larger masses gave a product that evolved O2 equivalent to of NazOz by causing local higher temperature 70 per cent conversion to NaOz. Test has shown than in the case of small bodies where heat that NaOz can be produced by my method also losses are greater. 55 from NazO. Of course mixtures of Na and NazC) The accompanying drawing is a series of or NazOz or both oxides, may be treated similarly. graphs representing temperature-pressure-com The desirability of this substance as a substi~ position relationships in the conversion of tute forv the sodium and potassium oxides that NaaOz to NaOz after 4 to 6 hours, in accordance have been used heretofore as oxygen-evolving with the invention. The data were obtained with substances is evidenced by the fact that a mix a bomb made from Type 347 stainless steel, of ture ‘of the peroxide and superoxide obtained in 4.6 liter capacity and holding charges of NazOz this way and containing 93 percent of the super of 3 to 3.5 lbs. Heat was supplied by electric oxide liberates 292 cc. of oxygen (N. T. P.) per strip heaters. The bomb was provided with a gram, .while at 99 per cent purity it evolves 303 nickel liner made by welding a nickel disc to the 65 cc. per gram. » - i . ~ . . bottom of a nickel tube. This is necessitated by Evidence that this product is indeed a. super the fact that at the temperatures involved so— oxide has been obtained by magnetic suscepti dium peroxide attacks stainless steel. “Pyrex” bility determinations. Extrapolation of a plot glass liners may be used up to about 450° C. for of the gram susceptibility in 0. gas. units found short periods, but for most purposes nickel liners for various mixtures of sodium peroxide ‘and are best. superoxide gave a valuefor pure superoxidecor Experience has shown that in the practice of responding to an effective magnetic moment of this method sodium peroxide that is dense or 2.07 Bohr magnetrons, which is in excellent agree in the form of hard granules yields products of ment with the moments of other lower available oxygen content than where the 75 reported in the literature. . 2,648,596 5 6 The process provided by this invention may 6. In a method or making sodium superoxide be performed simply and readily in high pres (Naoz) the steps comprising heating sodium sure apparatus with which the art is familiar peroxide and as a catalyst a minor amount and which therefore needs no detailed descrip of oxide of a metal having an atomic weight tion. 01 greater than that of sodium in a closed con This application is a continuation-in-part of tainer to a temperature of at least about 200° my copending application Serial No. 79,905, ?led C. while supplying oxygen under a pressure of March 5, 1949, now abandoned. at least about 1500 p. s. i. and thereby produc According to the provisions of the patent ing said superoxide from said peroxide. and re statutes, I have explained the principle and covering the oxidized product thus formed. mode of practicing my invention and have il 7. In a method of making sodium superoxide lustrated and described what I now consider (Nam) the steps comprising heating sodium to represent its best embodiment. However, I peroxide and a minor amount of desire to have it understood that, within the in a closed container to a temperature of about scope of the appended claims, the invention may 15 450° C. to 500° C. while supplying oxygen under be practiced otherwise than as speci?cally il a pressure of at least about 1750' p. s. i. and lustrated and described. thereby producing said superoxide from said I claim: peroxide, and recovering the oxidized product 1. In a method of making sodium superoxide thus formed. (NaOz) the steps comprising heating at least 20 8. In a method of making sodium superoxide one material of the group metallic sodium, so (NaOz): the steps comprising heating sodium dium monoxide, and sodium peroxide in a closed peroxide and a minor amount of titanium di container to a temperature of at least about 200° oxide in a closed container to a temperature of C. while supplying oxygen under a pressure of about 500° C. while supplying oxygen under a at least about 1500 p. s. i. and thereby produc pressure of about 2000 p. s. i. and thereby pro ing said superoxide from said material, and re ducing said superoxide from said peroxide, and covering the oxidized product thus formed. recovering the oxidized product thus formed. 2. In a method of making sodium superoxide 9. The method of producing sodium super (NaOz) the steps comprising heating metallic oxide, NaOz, which comprises heating sodium sodium in a closed container to a temperature - peroxide in a closed container to a temperature of at least about 200° C. while supplying oxygen of at least about 200° C. in an atmosphere of under a pressure of at least about 2700 p. s. i. oxygen supplied under a pressure of at least and thereby producing said superoxide from said about 200 atmospheres and recovering the super material, and recovering the oxidized product oxide formed. thus formed. 10. That method of producing sodium super 3. In a method of making sodium superoxide oxide, NaOz, which comprises heating sodium (Naoz) the steps comprising heating sodium peroxide in a closed container to a temperature peroxide in a closed container to a temperature of about 400° C. in an atmosphere of oxygen between about 300° C‘. and 500° C. while sup under a pressure of at least about 1310 pounds plying oxygen under a pressure between about per square inch, and recovering the superoxide 1500 and 2000 p. s. i. and thereby producing formed. said superoxide from said peroxide, and recover WILLIAM H. SCHECHTER. ing the oxidized product thus formed. 4. In a method of making sodium superoxide (NaOz) the steps comprising heating sodium References Cited in the ?le of this patent peroxide in a closed container to a temperature UNITED STATES PATENTS between about 450° C. and 500° C‘. while sup Number Name Date plying oxygen under a pressure between about 2,405,580 Jackson ______Aug. 13, 1946 1500 and 2000 p. s. i. and thereby producing 2,414,116 Miller ______.._ Jan. 14. 1947 said superoxide from said peroxide, and recov ering the oxidized product thus formed. FOREIGN PATENTS 5. That method of making sodium superoxide Number Country Date (NaOz) which comprises heating sodium perox 8,503 Great Britain ______Nov. 23, 1911 ide in a closed container to a temperature of OTHER REFERENCES at least about 300° C. while supplying oxygen under a pressure of at least about 1700 p. s. i. J. W. Mellor’s “A Comprehensive Treatise on for a time to produce equilibrium condition and Inorganic and Theoretical Chem,” vol. 2, page thereby producing said superoxide from said 493, Longmans, Green and Co., N. Y. peroxide, and recovering the oxidized product "Chem. Abstracts,” vol. 42, No. 8, pages 2533 thus formed. 60 (1948), published by ACS.