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Nov. 1, 1938. N. H. VAGENiUS ET AL 2,135,363 METHOD OF PREPARING QUINCNE Filed Oct. 10, 195-1, FlG.-l 2/ 20 IN VENTORS M23 HAROL 0 By V'Gf/V/l/é‘ Ma 120440 1[ ff/ao. 94 A TTORNEKS‘ . Patented Nov; 1, 1938 / ' __. UNITED STATES‘ PATENT o..FFicEjf-,_' 2,135,368 METHOD or PREPARING QUINONE Nels' Harold Kidd, Vagcnius, Warrensville, Chicago, Ohio Ill., and Rollo Application October 10, Serial No. ‘147,726 3, 7 ‘Claims. (Cl. 204-9) Our invention relates to a method of producing quinones, the phenol addition products thereof and hydroquinones, and more particularly to an improved method vof producing such compounds by the oxidation of the phenols. In producing quinones or hydroquinones it has heretofore been proposed to oxidize aromatic hydrocarbons, such as benzene, by passingtan electric current through A further. object'of our invention is to provide an improved process of producing quinone or the phenol addition products thereof by the electro chemical oxidation of phenol by'means of which. high uniform yields of such compounds may be 5 obtained. - -' Another object of'our invention is to ‘ provide a process of producing quinone-or the phenol anode serving to oxidize the hydrocarbon. Such addition products’ thereof from an electrolyte containing phenol by means of which the con centration of the phenol is maintained substan processes, however, are diflicult to control and tially constant and the quinone or a phenol ad an emulsion of benzene in an aqueous solution of . a salt or mineral acid, the oxygen formed at the various other ‘compounds may be formed, such as phenols and polyphenols, or if the oxidation is continued for a suf?cient length of time, the de sired products are oxidized to complete disinte gration in preference to the hydrocarbons. Attempts have also been made to oxidize the phenols, particularly phenol itself. Reports of investigations show, however, that in addition to quinone and phenoquinone other oxidation prod 1o dition product-thereof is quickly removed from the oxidation zone as soon ash is formed. A further object of our invention is‘to provide 15 an improved method of preparing hydroquinone by means of which quinone or a phenol addition product of quinone is ?rst formed by the oxida tion of a phenol and the hydroquinone is formed by the‘ electrochemical reduction of the quinone 201 or a phenol addition product thereof. Another object of our invention is to provide an ucts are formed, such as resinous bodies, ‘poly-v phenols, catechol, fatty acids, etc. In view of improved solution or electrolyte in which quinone the side reactions which take place and the num erous other products which are formed it has. heretofore been impractical to produce quinone, the phenol addition products thereof or hydro quinone, commercially by such processes. We have made the discovery that if phenol is . or a phenoladdition product thereof isv insoluble dissolved in an aqueous solution of a mineral acid or an acidv salt in certain speci?ed propor trochemical reduction to produce hydroquinone and phenol, and the phenol is again utilized in tions and the temperature maintained within a speci?ed range, phenols may be effectively and commercially oxidized to quinone or the phenol the process. an addition products thereof, depending upon the ' ‘at certain speci?ed temperatures. T25 A still further object of our invention is to pro vide an improved process in which a phenol addi tion product of quinone is formed by the oxida tion of a phenol, the product is subjected to elec Although we do not desire to be limited in this respect we prefer to utilize the electrochemical method of oxidizing the vphenols to produce qui-' 35 nones or the phenol'addition products thereof, and this method has accordingly been illustrated in the accompanying drawing in which Fig. 1 is a diagrammatic view of an apparatus for pro concentration of the phenol and the temperature at which the reaction takes place. The quinone, or the phenol addition products thereof, may then be reduced to hydroquinone. While we do not desire to be limited in this respect, our process is particularly adapted for producing quinones or the phenol addition prod- ' ucts thereof by the electrochemical oxidation of, the phenols. Our invention also contemplates in its more speci?c form the production of quinone or the phenol addition products thereof by the oxidation of the phenols and their subsequent reduction preferably by electrochemical means, to form hydroquinone. paratus for producing quinone or a phenol addi tion product thereof, and reducing it to hydro vide an improved process of producing quinone or phosphoric acid. ' Solvents'which are neutral or the phenol addition products thereof by the oxi slightly acid may also be ‘employed, such as the ducing quinone or the phenol addition products 40 thereof; and Fig. 2 is a similar view of an ap quinone. . r 45 ' In practicing our invention in accordance with I the method illustrated in the drawing, phenol or a homologue‘ of phenol, such as cresol or xylenol, is dissolved in the electrolyte composed of a dilute solution of a mineral acid which does not It is therefore an object of our invention to pro- ' react with the phenol, such as sulphuric acid or dation of phenols. ' ' Another object of our invention is to provide an effective process of preparing quinone, the phenol alkali bisulphates. For example, sodium bisul phate, aluminum sulphate and potassium alum 55 inum sulphate have been found suitable. The addition products thereof, or hydroquinone, by ' electrolyte may be present in amounts ranging means of which such compounds may be econom-. from 5% to 20%, although we do not desire to ically and practically produced in an economical be limited in this respect as good results have manner. -.been obtained when the electrolyte-is present in 60 2,185,868 2 I amounts as low as 1%. As the electrolyte we prefer to utilizean aqueous solution containing approximately 10% of sulphuric acid. vAs illus trated in the drawing, the electrolytelwhich con . tains the dissolved phenol is placed in a suitable plating tank ,2 that is capable of resisting the solvent action of the electrolyte or any of the oxidation products which are formed. The plat ing tank or cell is provided with an anode 3 which 10 is preferably formed of rolled or polished lead. , maintain a substantially uniform concentration _. of-the phenol in the electrolyte. As the quinone or phenol addition product thereof is produced and removed from the oxidation zone, additional 10 phenol should be added from the supply tank ‘I. gauze having approximately twenty meshes per square inch. In preparing quinone or pheno quinone a porous diaphragm 5 is preferably inter posed between the electrodes although this is not process may ‘be improved by adding a small _ seen that the concentration of the phenol in the electrolyte is a material factor in determining whether quinone, phenoquinone or a mixture of these two compounds is formed. While we have enumerated certain concentra tions of phenol and speci?ed certain temperatures at which quinone, phenoquinone or a mixture thereof will crystallize from the electrolyte, we prefer to maintain the electrolyte at a tempera ture below 7° C. The temperature of the elec trolyte should be above the freezing point and below 12° C. The most desirable temperature, however, is slightly, above the freezing point, say from approximately3° to 5° 0., because the qui 50 none or phenoquinone is less soluble in the elec trolyte at low temperatures. Suitable means, such as coils 6 through which.a cooling fluid or refrig erant is passed, may be provided to maintain the electrolyteat the desired temperature. If itis desired to produce q?inhydrone', the electrolyte is maintained at a temperature from approximately 12° to 17° 0., preferably about 15° C. In producing qi?nhydrone it is also essential that the porous diaphragm be omitted. .In plTQducing quinone,“ is essential that the concentration of the phenol should be maintained below 1% and in producing the addition products of quinone, such as phenoquinone or quinhydrone, it is essential that the concentration of the phenol 65 in the electrolyte should be maintained below 5% and preferably below 3%,; otherwise undesirable side reactions will take place. During the passage of the current the quinone or phenol addition product thereof is removed 70 from‘ the zone of oxidation, ?ltered as indicated at 8 from the mother liquor which may be returned to the electrolyte'by means of a suitable pump 9 75 proximately one ampere per twenty-eight square inches of surface. 5 To obtain uniform yields it is also desirable to The cathode 4 may be formed of 'copper or bronze essential. If it is desired to produce quinhydrone, however, the porous diaphragm should be omit ‘ted; otherwise a precipitate containing undesir able products will be obtained. A direct current is then passed through the electrolyte. The particular product which is formed will depend upon the temperature and the concentra tionyof the phenol and whether a porous dia phragm is employed. If the concentration of the 25 phenol is maintained low, for example, if not more than 1% is present and the temperature is kept below 12° C., the product will be composed principally of quinone, although some pheno quinone may be produced. If the concentration 30 of the phenol is increased, a greater amount of phenoquinone will be produced. When the con centration of the phenol in the electrolyte is pres ent in amounts ranging from 2% to 5% and the temperature is_ maintained below 12° C. pheno 35 quinone will be produced. ‘It will therefore be 55 the anode may be varied within reasonable limits, we prefer to maintain the voltage below 3.5 volts.v The current density at the anode should be ap-~ We have also found that the e?iciency of the amount of a catalyst. For example, approximate ly one gram of chromium sulphate for each ?ve 15 hundred grams of electrolyte has been found suit able. The quinone or phenol addition product thereof may, if desired, be reduced to hydroquinone by any; of the usual processes. In accordance with 20 our invention the quinone or phenol addition product thereof is ?rst formed by‘the method which has just been described and then reduced to hydroquinone by electrolytic reduction. The oxidation of the phenols to quinone or the phenol 25 addition products thereof and the subsequent re duction may be performed separately or the two processes may be combined as illustrated in Fig. 2 of the drawing. As illustrated in Fig. 2, the apparatus utilized in 30 producing the quinone or phenol addition product thereof, is similar to that shown in Fig. 1 and the parts have consequently been designated by the same numerals. The quinone or phenol addition product thereof which ‘is separated from the 35 mother liquor by ?ltration or other suitable means is introduced into the electrolyte l2a of an elec troplating cell or tank i2. The electrolyte in the reducing step may be composed of a dilute solu tion of sulphuric acid. It is not necessary that all 40 of the quinone or the phenol addition product thereof should be in solution. The cell I2 is provided with an anode 13 which may be formed of lead and a cathode M which may be formed of copper or bronze gauze similar 45 to that utilized in the oxidation cell. The current is then passed through theelectrolyte utilizing ap proximately two volts and substantially the same current density as that employed during the'oxi dation step. The temperature of the electrolyte 50 is maintained at approximately 60° C. and if nec essary suitable coils I5 through which a heating ?uid may be .passed are provided for this purpose. The efficiency of the reduction step may also be improved by adding a suitable catalyst, such as 55 titanium sulphate or tin sulphate. Approximate ly twp grams of the catalyst for each one hundred grams of electrolyte has been found satisfactory. The contents of the cell are then treated with av small amount of charcoal and allowed to cool. 60 If quinone orpquinhydrone are ?rst prepared they will be reduced to hydroquinone during ‘the reduction step. If phenoquinone is-?rst prepared, during the reducing step the quinone is reduced to hydroquinone and the phenol floats upon the surface of the hydroquinone and may be removed by ‘any suitable means or method, ~such as by skimming or decantation, or as illustrated in the drawing the phenol may be returned to the sup ply tank ‘I by means of a pump l6 and pipe 41. The hydroquinone which separates in the form of . crystals may then be removed from the cell l2 and and pipe Hi. the crystallized product being col separated from the mother liquor at I8 by ?ltra lected in the receptacle ll. tion or other suitable means and collected in the ' ' Although the voltage and current density at ' . receptacle I9. The mother liquor may then be ‘(I 3 2,185,868 returned to the cell I 2 by pump 20 and pipe 2|. As previously stated, we do not desire to limit our invention to the electrochemical method of producing quinone or the phenol addition prod ucts thereof. For example, the phenol in the concentration speci?ed may be dissolved in a dilute solution of phosphoric or sulphuric acid, say a solution containing 1% to 20% of such acid or preferably from 5% to 20%, and the oxidation 10 may be performed by means of suitable oxidizing agents such as ozone, hydrogen peroxide or per sulphuric acid. ‘ By oxidizing the phenol and maintaining the concentration of the phenol and the tempera 15 ture within the range speci?ed during the elec trochemical method of oxidation, either quinone or a phenol addition product thereof, such as phenoquinone or quinhydrone, will precipitate and may be intermittently or continuously re from the spirit and scope thereof. ' Our disclosure, description and examples given herein are purely illustrative and are not intended to be in any sense limiting. - What we claim is: 1. The process of producing a quinone oxida tion product of a phenol, at least part of which is obtained as a precipitated solid, which com prises passing a direct electric current through an aqueous solution of an acidic inorganic elec 10 trolyte which is a solvent for the phenol and which contains a substantial amount but less than three per cent of the phenol in solution while maintaining the electrolyte at a temperature 15 ranging from 0° C. to 17° C. 2. The process of producing a quinone oxida tion product of a phenol, at least part of which is obtained as a precipitated solid, which com prises passing a direct electric currentthrough an aqueous solution of an acidic inorganic elec 20 trolyte which is a solvent for the phenol and which contains a substantial amount but less than three per cent of the phenol in solution while phenol is added to or mixed with a chilled aque- ' maintaining the electrolyte at a temperature 20 moved from the sphere of the reaction. By utilizing the essential features of our inven tion it is also possible to prepare the phenol ad dition products of quinone. For example, if ous solution of quinone or an aqueous solution containing an electrolyte such as sulphuric or ranging from 0° C. to 17° C., and removing'the phosphoric acid, and the temperature is main tained below 12° C., or preferably below 7° C., as they are formed. . phenoquinone will separate. In a like manner, by adding an aqueous solution of hydroquinone, 3. The process of producing a quinone oxida tion product of a' phenol, at least part of which is obtained as a precipitated solid. which comprises 30 or an aqueous solution of hydroquinone contain passing a direct electric current through a di ing an electrolyte, to an aqueous solution of lute aqueous solution of sulphuric acid contain ing a substantial amount but less than three per cent of phenol to ,oxidize the phenol while maintaining the electrolyte at a temperature. 35 ranging from 0° C. to 17° C. 4. The process of producing phenoquinone, at least part of which is obtained as a precipitated solid, which comprises passing a’ direct electric current through an acidic inorganic electrolyte 40 quinone, or mixing the solutions together and maintaining ‘the temperature between 12° and 17° C., quinhydrone may be precipitated. It will therefore be seen that the quinhydrone may be readily converted into hydroquinone, or hydro quinone may in turn be converted into quinhy drone. 40 oxidation products from the zone of reaction ' ‘ . From the foregoing speci?cation it will be ap parent that we have provided a practical and effective method of producing quinone or the phenol addition products thereof byv the oxida tion of phenols ‘which may be commercially and economically utilized in preparing the desired product. It will also be seen that we have provided an which is a solvent forv phenol and which con tains more than one per cent and less than three per cent of phenol in solution while mainr taining the electrolyte at a temperature ranging from 0° C. to 7° C. n 5. The process of producing quinone which comprises passing a direct electric current economical and practical method of electrochem ically oxidizing the phenols by means of which through an aqueous solution of an acidic inor quinones, phenoquinones, quinhydrones and hy and which contains a substantial amount but less than one per‘ cent of phenol while main droquinones may be produced in an e?ective and commercial manner. It will also be apparent that we have provided an improved process by means of which phenols may be readily oxidized to quinone or the phenol ganic electrolyte which is a solvent for phenol taining the temperature of the electrolyte be tween 0° C. and 7° C. 6. The process of producing a mixture of qui none and phenoquinone, at least part of which 55 addition products thereof without forming large is obtained as a precipitated solid, which com quantities of other oxidation products and that prises passing a direct electric current through the products thus obtained may be readily and an aqueous solution of an acidic inorganic elec trolyte which is a solvent for'phenol and which effectively reduced to hydroquinone by electro contains from one per cent to three per cent of chemical means. phenol in solution while maintaining the tem It will also be‘ understood that we have pro vided a method by means of which quinones or the phenol addition, products thereof may be effectively converted into hydroquinones by elec tro chemical reduction. It will be understood in the specification and perature of the electrolyte between 0° C. and 7° C. 7. The process of producing quinhydrone, at least part of which is obtained as a precipitated solid, which comprises passing a direct electric current between electrodes placed inan acidic ' claims that the term “quinone oxidation product inorganic electrolyte which is a solvent for of a phenol” is intended to include not only quinone itself but also the phenol addition prod phenol and which contains phenol in substantial amounts but less than three per cent while maintaining the temperature of the electrolyte ucts thereof. _ To those skilled in the“ art many modi?cations and widely differing embodiments of our inven tion will suggest themselves without departing between 12° C. and 17° C. NE'LS HAROLD VAGENIUS.‘ RDLLO J. EDD.