3,809,746 United States Patent Office Patented May 7, 1974 2 The exothermic reaction during mixing is represented 3,809,746 by the following equations: PROCESS FOR PRODUCING POTASSUM SUPEROXDE Hydration Satoshi Takahashi, Tokyo, Japan, assignor to Fire Re search Institute, Fire Defence Agency, Ministry of KOH--HO(1)->KOHaq--12.9 Kcal. (1) Home Affairs, Tokyo, Japan Neutralization No Drawing. Filed Feb. 11, 1972, Ser. No. 225,637 Claims priority, application Japan, Feb. 22, 1971, 2KOHCc)--HO(1)-> 46/7,999 nt. C. C01b 13/00, 15/00 KO(c)--2HO(1) --5.4 Kcal. (2) U.S. C. 423-581 5 Claims 10 Decomposition ABSTRACT OF THE DISCLOSURE KO(c)--HO(1)->2KOH(c) - 43.7 Kcal. (3) Potassium hydroxide and a concentrated aqueous hydro Thus the separation of the product mixture from halo gen peroxide solution are mixed under high vacuum the 5 genated hydrocarbons requires a time-consuming cum compounds forming potassium peroxide-hydrogen peroX bersome operation, always facing the danger of ignitio ide KO-2H2O, which is heat-dried and then dehydrated by sudden decomposition. at an elevated temperature to form potassium Super While the process taught by the above-mentioned U.S. oxide KO2. patent not only requires a carefully controlled cooling 20 process in order to cope with the vigorous exothermic reaction according to the Equations 1 and 2 it must also SPECIFICATION often meet the cooling demand caused by decomposition This invention relates generally to manufacturing of heat accumulated in the system according to the Equa potassium superoxide and more specifically to a wet proc tion 3. ess for producing the Superoxide. 25 Furthermore, the product obtained by such known proc The potassium superoxide has found significant value esses, even when subjected to vacuum distillation, cannot as a relatively rich source of oxygen for breathing appara be evaporated because of the self-cooling property at tuses and for restricted atmospheric areas such as Sub evaporation and requires a considerably long period to marines. This compound can be utilized as a solid state reach complete dryness and the decomposition according storage medium for oxygen and as absorbent of carbon di 30 to the Equation 3 often takes place thereby lowering the oxide. Presently such higher oxide is being considered for purity of the product obtained. use as an oxygen supply and carbon dioxide absorbent in It is the primary object of this invention to provide an manned space vehicles. improved and simplified process for producing potassium Potassium superoxide has in the past been produced by superoxide. 35 A specific object of this invention is to provide an im the combustion of pure potassium peroxide in oxygen. proved and an economical process for producing potas Such processes involve the use of pure potassium per sium superoxide. oxide and thereby suffer from the attendant problem A further object of this invention is to provide a proc factors of cost, handling and storage of the material. ess for producing potassium superoxide from readily avail U.S. Pat. No. 2,648,596 issued to Schechter is cited. An 40 able materials under reasonable production conditions. example of an attempt to circumvent the problems of the Another object of this invention is to provide a process prior art is found in the chemical procedural approach for obtaining potassium superoxide from a reaction mix disclosed in U.S. Pat. No. 2,908,552 issued to Cunning ture obtained by directly mixing solid potassium hydrox ham. Recently, in U.S. Pat. 3,120,997 a wet process was ide with hydrogen peroxide. disclosed by which potassium superoxide from potassium 45 Still another object of the present invention is to pro hydroxide KOH and concentrated hydrogen peroxide vide a novel industrial process free from the dangerous H2O can be synthetized. Further, the following year in operations and hazards mentioned above. the French Pat. 1,460,714, a process for synthetizing With the foregoing and other objects in view, the in potassium superoxide by employing halogenated hydro vention resides in the following specification and ap carbons as reaction buffers and cooling accelerators dur 50 pended claims. ing mixing and subsequently pyrolizing the obtained mix According to the process of the present invention ture under atmospheric pressure, was disclosed. However, potassium hydroxide and concentrated hydrogen peroxide the synthesis disclosed in said French patent does not are mixed and reacted in a vessel under a highly reduced lead to the quality standard obtainable by the process dis pressure. closed in said U.S. patent in purity of the product ob 55 More specifically according to the present invention, tained, and moreover the mixing of KOH and hydrogen particles or paste of potassium hydroxide are placed in peroxide solution, even when carried out under carefully a reaction container positioned on a heater in the vacuum controlled cooling conditions, sometimes leads to rapid vessel eventually employed, and hydrogen peroxide solu decomposition due to the floating on the surface of the tion is introduced into said reaction container at a low mixture of halogenated hydrocarbons. Such decomposi 60 flow rate by aspiration from an outside reservoir through a pipe equipped with a control valve. tion often causes an ignition of the system, and the dam Though a significant amount of heat is generated in age of such an accident becomes serious in production on the reaction container due to vigorous exothermic reac commercial scale because of the evolved heat accumulated tions according to the Equations 1 and 2, said heat is in the system. 65 immediately dissipated from the system as the latent heat 3,809,746. 3 4. of evaporation of excessive water originally present in perature not exceeding 50° C. by the heater until the hydrogen peroxide and water generated by the reaction drying was completed. When the drying was visually con between potassium hydroxide and hydrogen peroxide, firmed to be complete, the decomposition was initiated since the reaction system is constantly kept under highly by local heating with said heater to obtain yellow KO. reduced pressure. Consequently the mixture in the reac tion container can be kept constantly at a temperature Time required: 1 hr; Purity: 85%. below a critical temperature which would trigger off the EXAMPLE 2 decomposition according to the Equation 3. 48 ml. of 55% HO solution was introduced to 30 gr. These differences are schematically shown in the fol of granular KOH, G.R. grade, similarly to the Example lowing flow-chart: O 1. After drying the product was maintained at 60° C. and locally heated by the heater thereby initiating rapid Conventional process: decomposition to obtain KO. KOH and HOaq Time required: 55 minutes; Purity: 89% mixed under - Vacuum a-> EXAMPLE 3 atmospheric Evaporation 5 pressure 30 ml. of 90% HO solution was introduced to 30 gr. - Q of granular, KOH and the succeeding operations were car Dried - Decoraposition - KO ried out similarly to those in the Example 2. KO-2H2O Time required: 50 minutes; Purity: 86% Cooling 20 As is understood from the preceding description and -Q1 examples, the advantages of the process according to the Process of this invention: present invention are: KOH and HOaq - Dried -> Decomposition - KO (1) shortened reaction time due to simplified process, mixed under (2) economization in labor due to simplified process, reduced pressure (3) elimination of coolant and associated equipment to avoid an explosion and (4) improvement in the reliability of the process and the Vacuum evaporation -- Q1 product purity. 30 Thus the process according to this invention is highly | economical compared with the conventional process in Heating consideration of time, equipment and labor being econo -- q mized to less than half. What is claimed is: 35 1. A process for producing potassium superoxide which The use of hydrogen peroxide solution of unnecessarily comprises mixing and reacting a member selected from high concentration will elevate the reaction temperature, the group consisting of granular potassium hydroxide and accelerating the decomposition rate according to the an aqueous paste of potassium hydroxide with a concen Equation 3 and thus lowering the purity of KO2. Con 40 trated aqueous solution of hydrogen peroxide under a sequently in case of hydrogen peroxide solution of high high vacuum on the order of 5 mm. Hg, heating the reac concentration it is recommended to make a paste of KOH tion product to dryness at a temperature lip to 50 C. particles with water of necessary amount comparable to and decomposing the thus obtained KOa2H2O2 at an ele that calculated from the thermodynamic Equation 1 in vated temperature higher than 50 C. to about 60 C. order to obtain a high purity of KOz. Also in case of 45 whereby potassium superoxide KO2 is obtained. using hydrogen peroxide and KOH particles alone instead 2. A process for producing potassium superoxide KO2 of KOH paste, it is preferable to keep the concentration comprising the steps of placing potassium hydroxide in a of hydrogen peroxide solution within the range of 40 reaction container, subjecting said potassium hydroxide to 80%. high vacuum of the order of 5 mm. Hg, adding an aque According to the process of the present invention the 50 ous solution of hydrogen peroxide through a measuring effective utilization of the heat of hydration resulting tube to said reaction container for reaction with the po from the Equation 1 and the heat of neutralization re tassium hydroxide, the reaction producing evaporation of sulting from the Equation 2 for eliminating the water water contained in said aqueous solution and evaporation contained in the hydrogen peroxide solution and gener of water which is formed during the reaction, said evapo ated from the reaction 2 can be attained and it is usually 55 rations holding the reaction temperature below a decom unnecessary to supply heat to the heater for drying.