3,743,706 United States Patent Office Patented July 3, 1973 2 tracts which contain over 35 weight percent HO, e.g. 3,743,706 up to 55%, especially preferred are aqueous extracts con PROCESS FOR THE PRODUCTION OF ORGANIC taining 45 to 55 weight percent HO. The preferred HYDROGEN PEROXEDESOLUTION are acetates, most preferably n-. Gerhard Kabisch and Wolfgang Kunkel, Rheinfelden, In the anthraquinone process there are used alkyl Germany, assignors to Deutsche Gold- und Silber anthraquinones such as, 2-ethyl anthraquinone, 2-butyl ScheideanstaltGermany vormals Roessler, Frankfurt am Main, anthraquinone, 2-isopropyl anthraquinone, 2-amyl anthra No Drawing. Filed Aug. 9, 1971, Ser. No. 170,366 quinone, 2-sec. butyl anthraquinone, 2-t-butyl anthra Claims priority, application Germany, Aug. 19, 1970, quinone, 2-sec. amyl anthraquinone, and mixtures of P 20 41. 1249 10 them as well as their partially nuclear hydrogenated de nt. C. C01b: 15/02, 15/00 rivatives, e.g. the tetrahydro anthraquinones such as 2 U.S. C. 423-588 9 Claims ethyl tetrahydro anthraquinone. The esters employed are alkyl alkanoates such as ethyl ABSTRACT OF THE DISCLOSURE acetate, propyl acetate, , , 5 propyl formate, butyl formate, , t-butyl Organic hydrogen peroxide solutions are obtained by acetate, , , octyl acetate, extracting aqueous crude hydrogen peroxide solutions heptyl acetate, hexyl acetate, cyclohexyl formate, cyclo arising from the anthraquinone process using as the pentyl acetate, cyclohexyl acetate, , extraction agent carboxylic acid esters having a total of , propyl propionate, , 4 to 10 carbon atoms. 20 , methyl valerate, methyl isovalerate, 2 ethylbutyl acetate, sec-hexyl acetate, isopropyl propionate, amyl propionate, propyl butyrate, isobutyl butyrate, The present invention is directed to a process for the methyl isobutyrate, ethyl isobutyrates, propyl isobutyrate, production of hydrogen peroxide solutions in organic isopropyl isobutyrate, amyl isobutyrate, ethyl valerate, solvents. Such H2O2 solutions today have acquired a large 25 methyl isovalerate, propyl isovalerate, methyl caproate, industrial importance, for example for the production of methyl pivalate, ethyl pivalate, propyl pivalate, isopropyl water free (anhydrous) percarboxylic acid solutions. pivalate, butyl pivalate, sec. butyl pivalate, amyl pivalate Hydrogen peroxide is produced on a large scale to and methyl of 2,2-dimethyl valeric acid. over 90% by the so called anthraquinone process and is It could not be predicted that carboxylic acid esters hav accumulated in the extraction step of the cyclic process in 30 ing a total of 4 to 10 carbon atoms could be used for the the form of aqueous solutions having an H2O2 content extraction of HO from aqueous solutions of up to of about 20-35 weight percent. Hydrogen peroxide con 55% HO content since British Pat. 931,119 teaches that centrates, as the HO commercial product with an H2O2 esters are soluble in highly concentrated aqueous H2O2. content of 65-70 weight percent for example still are ob Surprisingly, however, the esters used according to the tained exclusively today by total distillation of the crude 35 invention are largely insolubule in the H2O2-crude ex extract, products with HO contents of over 80% are tract of the anthraquinone process and in regard to the recovered practically only by two distillations. absorbing of H2O2 and water possess such a good selectiv The production of organic HO solutions on the basis ity that they make outstanding extraction media. Thus, for of these aqueous products can take place by extracting an example (see Table I) the H2O:HO ratio of 50:50 in about 30 weight percent solution with ether, adding an 40 the aqueous starting solution can be increased to a ratio organic solvent and then separating the ether by distilla of over 78:22 in the organic phase. While one the one tion (see Houben-Weyl, Methoden der organischen hand esters with less than 4 carbon atoms, as for example, Chemie, Sauerstoffverbindangen III, vol. 8, page 33). , are soluble in the aqueous crude extract These known methods because of their troublesomeness and therefore cannot be used in the process of the present and dangerousness until now have been limited to use in 45 invention, on the other hand carboxylic acid esters with laboratory techniques. more than 10 carbon atoms possess so small an H2O2 It is also known (for example see British Pat. 931,119) absorptive power that their use is uneconomical. Esters to dissolve highly concentrated, preferably over 80 weight with a total number of carbon atoms in the range of 4-10, percent, aqueous HO solutions in organic solvents. If however, fulfill surprisingly well the conditions of suffi water free HO solutions are desired the water can be 50 cient insolubility and a high absorptive power for HaO2 subsequently removed by azeotropic distillation. This in the extraction of H2O2 from an aqueous crude extract process, however, until now has not been accepted in the up to 55%. art since the necessary, highly concentrated HO is an The extraction media of the invention moreover, are expensive material due to high energy costs. good entraining agents for water since they form favor A process has recently become known through German 55 able azeotropes with it so that water free solutions are patent application 1,802,003 and the corresponding obtained in a simple manner, if an entraining distillation Schreyer et al. U.S. application 856,070 filed Sept. 8, is carried out for the removal of the residual water after 1969 and now abandoned and the continuation-in-part the extraction. Schreyer et al. application 79,315 filed Oct. 8, 1970 in In contrast to the known processes, especially that which non aqueous HO solutions are produced by 60 of British Pat. 931,119 the process of the invention has separating the H2O present in the working solution of the decided advantage that the concentration of H2O is the anthraquinone process with the aid of easily volatile carried out by simple extraction instead of expensive organic solvents. Also in this industrially more attractive distillation latter being also accompanied by H2O2-losses. process it is a matter of a total distillation of the HO The process with the extraction agents of the inven solvent mixture. 65 tion can be carried out in a practical manner simply and It has now been found that there can be obtained solu safely either batchwise or continuously in the usual ex tions of H2O in organic solvents under industrially sim traction apparatuses (columns, extraction machines, mixer ple and economically favorable conditions if the aqueous settlers). crude extract formed in the anthraquinone process is The extraction temperature can be between 0 and 60 washed with a carboxylic acid ester having a total of 4 70 C., preferably, however, the temperature is between 10 to 10 carbon atoms. Preferably there are used such ex and 40 C. 3,743,706 3 4 Unless otherwise indicated all parts and percentages as the oxidizing gas amounted to 1.0 weight percent on are by weight. the average. The extraction steps consisted of two spray EXAMPLE 1. columns, each 100 millimeter in diameter and 9 meters The binodal curves for the system HO-H2O2-carbox long. Each of the columns had on their bottom as a ylic acid ester were determined by turbidity titration at distributor a perforated plate with a free cross section 20° C. The concentration of H2O in several esters in of 4.2%. In the extraction column there were fed hourly equilibrium with 50% aqueous hydrogen peroxide and 4.75 liters of water. There arose HO in an amount of the concentration of the water taken up are shown in 7.8 liters (density 1.194 at 15 C.) whose concentration Table I. on the average amounted to 50 weight percent. The O amount of H2O obtained corresponded to an extraction ABLE I yield of 98%. The temperature in the hydrogenation step Weight percent of was 43 C. and the catalyst was palladium. ------mm Proportion O2 in 20 in EEOI2O The 50% H2O2 had a carbon content of 187 mg. Ester ester ester in ester C./liter. After passage through a 4 meter long washing n-Propy acetate. 3. 5.0 72.4:27.6 5 column (50 mm. in diameter). (filled with aromatic hy Isopropyl acetate 2.5 4.5 73.6:24, 4 drocarbon, boiling range 160-185. C.), the carbon value n-Butyl acetate.----- 7.2 2.0 78.32 Methylpropionate------22.0 10.0 68.8:31, 2 in the 50% H2O2 was lowered to 162 mg. C./I. What is claimed is: EXAMPLE 2 1. A process for the production of a solution of hy 20 drogen peroxide in an organic solvent by extraction of In an extraction machine whose efficiency corresponded aqueous crude hydrogen peroxide solution formed in to 5 theoretical steps there was extracted 50% aqueous the anthraquinone process and containing 35 to 55 weight HO with propyl acetate. After the extraction equilibrium percent H2O2 comprising extracting said aqueous hydro was reached at room temperature the solutions flowing gen peroxide solution with a carboxylic acid ester having off were analyzed. The aqueous phase still contained 25 a total of 4 to 10 carbon atoms at a temperature of 0 17.0% HO, the organic phase contained 8.8 weight to 60° C. percent H2O2. 2. The process according to claim 1 wherein the ester EXAMPLE 3 is an alkyl alkanoate. 3. The process according to claim 2 wherein the con 2.19 kg. of 50% aqueous HO was extracted hourly 30 centration of HO2 in the starting solution is 45-55 weight in an extraction column with 9.682 kg. of n-propyl ace percent. tate at room temperature. 4. The process according to claim 3 wherein the extrac From the head of the column there was drawn of tion is carried out at 10 to 40° C. a solution which contained 9% (1.0 kg.) H2O2, 4% 5. The process according to claim 2 wherein the ex (0.44 kg.) of HO and 87% (9.67 kg.) of n-propyl ace 35 traction is carried out at 10 to 40 C. tate. 6. The process according to claim 2 wherein the ester The raffinate leaving the bottom of the column con is an alkyl acetate or alkyl propionate. tained 12.5% (0.09 kg.) HO, 2% (0.015 kg.) propyl 7. The process according to claim 6 wherein the ester acetate and 85.5% (0.65 kg.) of water. has 4 to 6 carbon atoms. The amount of HO, taken up in the organic phase 40 8. The process according to claim 7 wherein the ester corresponded to 93% of the amount fed in as aqueous is an acetate. H2O2. 9. The process according to claim 8 wherein the ester EXAMPLE 4 is n-propyl acetate. The 50% HO is produced according to Ser. No. References Cited 69152 (corresponding to Belgian Pat. 756014) in a techni 45 UNITED STATES PATENTS cal apparatus there was recycled a working solution through the process steps hydrogenation, filtration, oxida 3,592,776 7/1972 Fletcher et al. ------23-207 tion and extraction. The working solution had a com position analogous to that of German Pat. 1,261,838. FOREIGN PATENTS The solvent consisted of 25 parts by volume trioctyl 50 931,119 7/1963 Great Britain ------252-86 phosphate and 75 parts by volume of a technical alkyl benzene having a boiling range of 160 to 185° C. In OSCARR. VERTIZ, Primary Examiner the solution there were dissolved 125 grams/l. of 2-ethyl H. S. MILLER, Assistant Examiner anthraquinone. The flow of the working solution amounted to 500 liters per hour. The HO content in the working 55 U.S. C. X.R. solution after the oxidation step using 10% excess air 252-186