US1612361A - A cobpobation of - Google Patents

Description

H. J. CREIGHTON Filed March 26, 1926 v X 1| /0 467i PROCESS FOR ELECTROLYTICALLY REDUCING SUGARS TO ALCOHOL Dec. 28 1926 Strona,

STATES Erice.

HENRY JERMAIN CIBJEIVGIEI'LON,` OF. SWARIIHMOBE, PENNSYLVANIA, ASSIGNOB, TO

.ATLAS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

f rnoonss Fon ELEc'rBoLYTIcALLY REDUCING sneaks To ALCOHOL.

Application led March 26, 192'6. Serial No. 97,782.

This invention relates to a process for electrolytica'lly reducing sugars to the corresponding alcohols in neutral electrolytic or in alkaline solution and more particularly for electrolytically reducing mannose tomannite. By this process, most marked economies in the reduction of such sugars have been edected as will be hereinafter set forth.

in the reduction of sugars as developed by Fischer, the solution of sugar is shaken` with sodium amalgam prepared by adding metallic sodium to mercury. These amalgams contain 2.5 per cent sodium. lThe must necessarily be dilute because an ama amalgam by Water; there being formed sodium hydroxide and hydrogen, and it is this hydrogen which reduces the sugar.

As the alkalinity of the solution increases, the rate of reduction is retarded, and it is necessary to neutralize or partially neutralize the sodium hydroxide from time to time with sulphuric acid. This produces large quantities of sodium sulphate in the solution.

I have found that the same result may be accomplished more cheaply by producing the sodium amalgam by passing an electric current through a solution of a suitable sodium compound (sodium hydroxide, sodium chloride, etc), between an insoluble anode and a mercury cathode` the sodium liberated by the current dissolving in the mercury and 'forming a sodium amalgam. Thls amalgam may then be added to the solution of sugar or sugars which will-be reduced in the way previously described. In this case, however, we have the conversion of an expensive substance like sodium hydroxide into large quantities ot relatively cheap sodium sulphate. If sodium chloride is used for the production of the amalgam then it will be necessary to get rid of, or utilize the chlorine liberated at the anode. The production of large quantities of sodium sulphate 1n the sugar solution still remains. Under the process constituting the present invention, the objections just referred to may be largely eliminated by the production of an amalgam electrolytically. directly in the sugar solu` tion. I use a cell which is divided into two parts by a porous diaphragm. One section .of this cell (the cathodic section) contains a mercury cathode and means for agitating same; the .other section, of the cell (the anodic sectlon) contains an anode of suitable 55 material (platinum, lead dioxide, ete). In the cathodic section is placed an aqueous solution of mannose containing sodium or other alkali sulphate or other suitable compounds of the alkali or alkaline earth metals.

A suitable concentration for this catholyte is 15 to 25 percent sugar and 5 percent sodium sulphate. In lthe anodic compartment is placed an aqueous solution of sodium sulphate,

(for example 5 per cent,) or other suitable 75 electrolyte.- As an example of the strength of the current and the voltage employed, I may mention that good results have been obtained with a current of one and one-half amperes per square decimeter or cathode sur- 30 face, the voltage varying from 5 to 8 volts. depending upon the temperature, rate of stirring of the mercury cathode, etc. I have found the rate of stirring of the mercury cathode to be an important factor. more violent the agitationbf the mercury, the more rapidly the. reduction of the sugar proceeds.A It has also been found, however` that if the mercury is stirred too violently it becomes completely broken up into tiny droplets separated one from the othervby a film of the catholyte, and this causes the resistance of the cell to increase enormously. I have observed that in the operation of this process, the catholyte becomes grav and opaque due to the formation of finely divided suspended mercury, the presence of which possibly accelerates the reaction; and I sometimes add finely divided mercury to the catholyte. I have found it desirable to agitate the mercury cathode as vigorously as possi-ble without undue rise in the cell voltage. I preferably include a voltmeter X in the circuit with the cell and the operator may eiectively control the rate of agitation by noting the reading of the voltmeter. In the accompanying drawing: Fig. 1 is a dlagrammatic, vertical sectional The 85 view ott one form of electrolysis cell which may be employed inthe practice oit the process and;I

Fig. 2 is a view illustrating -the stirrer or agitator, hereinafter described-` n Referring to the drawing, 5 designates'a iar, or like container, constituting the main body of the cell. A body of mercury 6, disposed in the lower prtion of jar 5, constitutes the cathodic material of the cell and may be brought. into electrical connection with the negative conductor of the cell, by means of a metallic rod or'post 7, which prog'ects downwardlythrough a tube 8 ot suitable insulating material, such as glass, and has its lower end disposed in-the body of mercury. An agitator 9 is disposed in the body of mercury and is capable of being rotated from the exterior of the cell. As indicative of the fact that the agitator is capable of being so rotated from the exterior of the cell, I have conventionally illustrated a pulley 10 upon a shaft 11 of the agitator, but it is to be understood that any suitable means for rotation of the agitator may be employed.

The anode 12 of the cell consists of a suitable-material, such aslead or lead coated with lead dioxide. This anode is suspended in a porous cylinder 13, such as alundum, unglazed porcelain, etc., which is the porous diaphragm hereinbefore referred to.` Any suitable means may be employed for suspending the porous diaphragm, the anode, the agitator and the post 7 in the body 5. As one way of accomplishing that result, I have illustrated a cap or cover 14, which may be of glass, hard rubber or any other Suitable material, and from which the several elements mentioned are suspended. In the use of the cell just described, an aqueous solution of mannose. or other sugar or sugars, containing sodium sulphate or other suitable electrolyte and illustrated at A, is placed in the main body or cell 5, and constitutes the catholyte, hereinbefore referred to, while in the porous cylinder is placed the aqueous solution of sodium sulphate or other suitable electrolyte B, hereinbefore referred to.

A specific example of the operation of the process follows:

,An aqueous solution containing between 15 and 25 per cent of mannose and 5 per centof sodium sulphate is placed in the body 5 of the cell, on top'of the'mercury cathode 6, and the lead dioxide anode 12, contained in an alundum cylinder 18, is surrounded with an aqueous solution containing 5 per cent of sodium sulphate, the levels of the solutions in 5 and 13 being the same. An electric current having a strength of one and one-half ampees for every square decimeter of cathode 'surface is passed through' the cell, the mercury cathode being vigorousaeiaaei ly agitated by the agitator 9. 1lYWen the current is turned on, 'the sulphate ions are discharged at the lead dioxide anode and the discharged ions subsequently react with the Water forming oxygen and sulphuric acid in the alundum cylinder. In the cathodic section of the cell sodium ions discharge at the mercury cathode and the resulting sodium atoms unite with the mercury, orming sodium amalgam, which subsequently dccomposes the Water, forming nascent hydrogen and sodium hydroxide. The nascent hydrogen formed in this way reduces the mannose to mannite. Continuous decomposition of this amalgam would tend to increase continuously the alkali (sodium hydroxide) content of the catho; lyte as in the process previously described. This continuous increase, however, is prevented by the fact that hydrogen lions migrate from the anodic section ot' the cell into the catholyte and there neutralize some of the alkali, and hydroxyl ions (alkali) migrate from the catholyte into the alundum cylinder and there neutralize some of the acid, the net result of both neutralizations being the re-formation of sodium sulphate. In this way a limited amount of sodium sulphate is used over and over again. The rates of migration of these ions and other conditions are such that the catholyte al- `ways remains slightly alkaline (which is an advantage since I have shown that the electrolytic reduction of sugars takes place but slowly and with some sugars not at all, in an acid solution); and the anolyte always remains somewhat acid. Vhen reduction is complete the alkaline catholyte can be rendered neutral by the addition of the acid ano# lyte. While the catholyte is maintained in an alkaline condition, the neutralization referred to may be cai'ried to Such a point that the catholyte will be almost neutral. Therefore, I have in some of the appended claims used the term non-acid in describingr the natui'e of the solution, by which term I intend to cover both neutral clectrolytic and alkaline solutions. Bya neutral electrolytic solution, I mean a neutral solution containing an electrolyte. v

The reason a diaphragm cell has been used is that the sugar and the resulting alcohol must. be prevented from coming in contact with the anode, as otherwise they would be oxidized. It is obvious that the diaphragm lmust be sufficiently porous to permit the migration of the hydrogen-ions, hydroxyl-ions and other ions, and at the same time suiliciently denseto prevent the di'usion of the catholyte into the anode section of thecell, but atvthe Fame time not so dense as to increase unduly the voltage of the cell. The diaphragm material must also be of such a. nature as to withstand the act-ion of alkali on one side and the action mey I method to vLaisser vmixtures of sugars, for example mixtures of mannose and glucose, may be reduced by this the corresponding alcohols. Thus, the sugar syrup prepared by standard methods from vegetable ivory, consisting largely of mannose and some glucose and possibly other sugars maybe very readily reduced by the electrolytic method just described, and the resulting mannite or the mixed alcohols may be separated from the catholyte by .proper extraction methods.v It has been found that it. is much cheaper to reduce the syrupof mixed sugars obtained from vegetable ivory and then extract the mannite from the product of the reduction process, than to separate the mannose from the mixed sugars and then reduce said mannose to mannite. While the out-line of the process given above refers only to the electrolytic reduction of mannose, I have found that glucose, mannose, levulose, xylose, and mixtures of these-may be reduced in neutral electrolytic 'or alkaline solution between a mercury cathode and an insoluble anode in a divided or diaphragm cell. I believe that I am the first to use a neutral solution of sugar or sugars. containing a. neutral electrolyte, or an alkaline solution of sugar or sugars to be reduced as the catholyte in an electrolytic reduction process and I desire to claim the same broadly. Furthermore, I wish it to be understood that where the terms sugar or sugars arel used in this application they include pentoses, hexoses and all reducible sugars and mixtures of the same.

Although I have given specific examples and detailed descriptions of the process, I do not limit myself tothe use of sodium sulphate as an electrolyte. but include within the scope of my invention other sulphates of the alkali metals, such as potassium sulphate for example, other suitable compounds of the alkali and alkaline earth metals, such as magnesium sulphate for example, or any other suitable electrolyte. I do not limit myself to the concentrations of lthe electrolyte and sugars hereinbefore set forth, nor to the current densities herein given, nor to the number and arrangement of the porous diaphragms, nor to the material of same, nor to the materials used for the electrodes.

It is to be understood that the invention is notlimited by the recital of the specific' formed. However, the invention includes within its purview whatever changes. fairly come within'either the terms or the spirit of the apended claims.

Having described my invention, what I claim is:

1. The electrolytic rduction oi a sugar which comprises disposing a non-acid electrolytic solution of the sugar to be reduced between the anode and cathode of an electrolysis cell. I

2. The electrolytic reduction ofl a sugar which comprises disposing a non-acid electrolytic solution of the sugars between the anode and cathode of an electrolysis cell, in

the lpresence of a catalyst.V

3. The electrolytic reduction of a sugar which comprises disposing a non-acid electrolytic solution of -the sugar between the electrodes of an electrolysis cell, wherein the cathode isfa material having a high hydrogen over-voltage.

4. The electrolytic reduction of a sugar which comprises disposing a solution of the sugar 'between the electrodes of an electroly sis cell, wherein the cathode is mercury, and agitating said mercury during the reduction process.

5. The electrolytic reduction of a sugar which comprlses disposing a non-acid electrolytic solution. of the sugar between the electrodes of an electrolysis cell, wherein the cathode is mercury, and agitating said mercury durmg the reduction process.

6. The electrolytlc reduction of a. sugar to an alcohol which consists of disposing a 7. The electrolytic reduction of a sugar-to an alcohol which consists of disposing a non-acid electrolytic solution of the sugar to be reduced and a catalyst as the catholyte in an electrolysis cell, wherein the cathode consists of a body of mercury and agitating said mercury during the reduction process.

8. The electrolvtic reduction of a sugar to an alcohol which consists of disposing a non-acid electrolytic solution of the sugar to be reduced as the catholyte of an electrolysis cell. wherein the cathode is a suitable metal amalgamated with mercury.

9. The electrolytic reduction of a sugar to an alcohol which consists of disposing a catalyst and a non-acid electrolvtic solution of the sugar to be reduced as the catholytc of an electrolysis cell. wherein the cathode is a suitable metal amalgamated with mercury.

l0. The electrolytic reduction of a nonacid electrolytic solution of a sugar to an alcohol. p

11. The electrolytic reduction of a sugar toan alcohol in the' presence of finely divided mercury which consists of disposing very finely divided mercury and a non-acid electrolytic solution of the 4'sugar to `be reduced as the catholyte of an electrolysis cell, wherein the cathode consists of a body of mercury or a suitable metal amalgamated with mercury.

12. The herein described process which consists of'adding a suitable non-acid electrolyte to a sugar solution that is to be reduced to an alcohol to render the solution conducting rand then electrolytically reducing said sugar.

13. The herein described process which consists of adding a suitable compound of the alkali or alkaline earth metals to a sugar solution that is to be reduced to an alcohol to render the solution conducting and then elec- .trolytically reducing said sugar.

14. The herein described process which consists of adding two or more suitable nonacid electrolytes to a sugar solution that is to be reduced to an alcohol to render the sovlutio'n conducting and then electrolytically 4conducting and then electrolytically reducing said sugar.

16. The herein described process which consists of adding a mixture of two or more sulphates of the alkali 'metals to a sugar solution that is to be reduced to an alcohol to render thesolution conducting and then clectrolytically reducing said sugar.

17. The herein described process which conssts of adding a sulphate of an alkali metal to a sugar solution that is to be reduced to an alcohol to render the solution conducting and then electrolytically reducing said solu` tion. l

18. rl`he herein described process which consists ot adding a sulphate of an alkali Vmetal to 'a sugar solution that is to be reduced to an alcohol to render the solution conducting and then electrolytically reducing said solution in a cell wherein said solution constitutes the electrolyte.

19.'l`he herein described process which consists of'adding a sulphate of an alkali metal to a sugar solution thatl is to be rethe same in a cell, wherein the cathode conslsts of mercury and said solution constitutes the catholyte and agitating the catholyte and mercury together as vigorously as possible ^`without undue rise of yoltage inthe cell.

21. The hereinI descrlbed process of reducing a sugar to an alcohol which consists of adding a sulphate of an alkali metal to an 1 aqueous solution of the sugar to be reduced and then utilizing such solution as the catholyte in a cell, the anode and cathode of which are separated from `each other by a wall of a nature to resist the passage of the enV a nature to prevent the passage of the sugar and the produced alcohol but to permit the passage of hydrogen,hyxdroxyl and other ions and agitating the mercury cathode during the reduction process.

23. The herein described process of reducing a sugar to an alcohol which consists of treating a neutral aqueous solution of the sugar containing a sulphate of an alkali metal or an alkaline aqueous'solution of the sugar in an electrolysis cell having a mercury cathode which is separated from the `anode of the vcell by a wall of a nature to prevent the passage of the sugar and the produced alcohol but to permit the passage of hydrogen, hydroxly and other ions and agitating the mercury cathode and the sugar solution during the reduction process.

24. The process consisting of electrolytically treating a neutral aqueous solution of a sugar containing a sulphate of an alkali metal in a' two-compartment cell, one compartment of which'contains an anode, said compartments being separated by a wall of porous material of a nature to prevent the passage of the sugar solution or the formed alcohol-but to permit. the passage of hydrogen, hydroxyl and other ions, the sugar solution and the electrolyte constituting the l catholyte in the one compartment, the other compartment containing an anolyte, and agitat-ing the mercury cathode.

25. The process of electrolytically treating a neutral a ueousv solution of a sugar containing a hy roxide or carbonate of an alkalir metal in a two-compartment cell, one compartment of which 'contains a mercury cathode and the other compartment of which contains an anode, said compartments being separated by a wall of porous material of a nature to prevent the passage of the sugar sans@ or al@ .armed alaba but to permit the passage of hydrogen, hydroxyl and other ions, the sugar solution and the electrolyte constitutino the catholyte in the one compartment, the other compartment containing an anolyte, and agitating the mercury cathode.

26. The process of electrolytically treating a neutral aqueous solution of a sugar containing a sulphate of an alkali metal in a two-compartment cell, one compartment of which contains an anode of a material which does not dissolve during the passage of the electric current and the other compartment of which contains a mercury cathode, said compartments being separated by a wall of porous material of a nature to prevent the passage of the sugar .solution or the formed alcohol but to permit the passage of hydrogen, hydroxyl and other ions, the sugar solution and the electrolyte constituting the catliolyte in the one compartment, the other compartment containin an aqueous solution of a sulphate of an a kali metal.

27. The herein described process consisting of reducing a sugar to an alcohol by adding sodium sulphate to an aqueous sugar solution and treating said solution electrolytically in an electrolysis cell, the cathode of which is composed of mercury, sodium amalgam being formed-electrolytically directly in the cell.

28. The hercindescribed process consisting of reducing a sugar to an alcohol by adding sodium sulphate to an aqueous sugar solution and treating said solution in the cathdic compartment of'a two-compartyment cell, said cathodic compartment containing a mercury cathode and the anodic compartment containing an anode and an aqueous solution of sodium sulphate or other suitable electrolyte. r

29. The herein described proccs consisting ofv reducing a sugar to an alcohol by adding sodium sulphate to an aqueous sugar solution and treating said solution electro- .lytically in an electrolysis cell, the cathode of which is compose of mercury, sodium amalgam being formed directly in the cell, and agitating the mercury and the solution.

30. The herein described process consisting of reducing a sugar to an alcohol by adding sodium sulphate to an aqueous sugar solution and treating said solution in the catliodic compartment of a twocompartment cell, said cathodic compartment containing a mercury cathode and the anodic compartnient containing an anodev and an aqueous solution of sodium sulphate or other suitable electrolyte, and agitating the mercury and the sugar` solution.

31. The herein described process consisting of reducing a sugar to an alcohol by adding sodium sulphate to an aqueous sugar solution and treating said solution electrolytically in an electrolysisl cell, the cathode of which is com osed of mercury, sodium amalgam bein o'rmed electrolytically directly in the ce l, and a itating the mercury as vigorously as possib e without excessive rise of voltage .in the cell circuit.

32. The herein described process consisting of reducing sugars such as a pentose, a mixtureof pentoses, a hexose, a mixture of hexoses, and mixtures of pentoses and hexoses to the corresponding alcohols by add.-

ing a sulphate of an alkali metal to an aqueous solution of the sugar, or sugars and treating said solution electrolytically in the catliodic compartment of an electrolysis cell, the cathode of which is composed of mercury, and agitating the mercury and the solution of sugar or sugars as vigorously as possible Without undue rise of Voltage in the cell circuit.

The herein described process of reducing mannose .to mannite which consists of lsubJecting a solution containing mannose, Water and a sulphate of an alkali metal to the action of an electric current in an electrolysis cell having a body of mercury as a cathode, alkali inctal amalgam being formed directly in the cell for the reduction of the mannose to mannite.

34. The herein described process of reducing mannose to mannite )which consistsof subjecting a solution containing mannose, Water and a sulphate of an alkali metal to the action of an electric current in an electrolysis cell having a body of mercury as a cathode, and agitating the mercury and the solution, alkali metal amalgam being formed directly in the cell for the reduction of the mannose to mannite.

The herein described process of reducing mannose to mannite which consists of electrolyzing a solution containing mannose, Water and a sulphate of an alkali metal in a cell divided into two compartments by Va porous Wall, one compartment of which contains a. mercury cathode and the solution"` of mannose and the sulphate of the alkali metal and the other compartment of which contains-an anode of suitable material and an aqueous solution of a sulphate of an alkali metal, alkali metal' amalgam being formed directly in the Acathodic compartment for the reduction of the sugar, and agitating the sugar solution and the mercury as vigorously as possible Without undue rise in the cell voltage.

B6. The herein described process of reducing a'sugar to an alcohol WhichAV consists I of subjecting an aqueous solution containing from 15 to 25 per cent sugar and 5 per cent sodium sulphate to the action of an electric current in an electrolysis cell having a bodv of mercury as a cathode, sodium amalgam being formed directly in the cell for the reduction of said sugar to an alcohol.

37.1The lherein described process of re- 40. The herein described process of reducl40 ducing a sugar to an alcohol which consists -of subjecting an aqueous solution of sugar containing sodium sulphate to the action of an electric current in an electrolysis cell having a body of mercury as a cathode, sodium amalgam being formed directly in the cell.

88. The herein described process of reducing a sugar to an alcohol which consists of subjecting an aqueous solution of'sugar containing sodium sulphate to the action of anelectric current in 'an electrolysis cell having. a 4body of mercury as a cathode, and agitating the mercury and the solution, sodium amalgam 'being formed directly in the cell.

39. The herein described process of reducing a'sugr to an alcohol which consists of subjecting an aqueous solution of the sugar containing an alkali sulphate to the action of an electric current in an electrolysis cell, the anode and cathode ot which are separated from each other by a porous `Wall which prevents mixing of the anolyte and catholyte but permits the passage of hydrogen, hydroxyl and other ions, the cathodic 'section of the cell containing a body of mercury as a cathode and in which sec- Y tion the sugar solution and the alkali sulphate constitute the catholyte, the anodic section of the cell containing an anode and a suitable electrolyte; an' alkali metalamal'- gam being formed in the cathodic section by the discharged ions of the alkali metal and the mercury and undue increase of the alkalinity ofthe catholyte being prevented bythe migration of hydrogen ions romthe anodic section, which hydrogen ions reduce said alkalinity.

ing a sugar to an alcohol` which consists of subjecting an aqueous solution of the sugar containing an alkali sulphate to the actlon of an electric current in an electrolysis cell, the anodes and cathodes of which are separated from each other by porous walls which prevent mixing of the anolytes and catholytes but permit passage of hydrogen, hydroxyl and other ions, the cathodic sections ofthe cell containing bodies of mercury as the cathodes and in which sections the sugar solution and the sulphate of the alkali metal constitute the catholytes, the anodic sections containing anodes of a material which does not dissolve during thcl passage of the electric current and anolytes consisting of an aqueous solution of an alkali sulphate or other suitable electrolyte; an alkali metal amalgam being formed in the cathodic Vsect-ions by the discharged ions of the alkali metal and the mercury and undue increase of the yalkalinity of the catholytes being prevented by the migrationof hydrogen ions from the anodic sections, which hydrogen ions reduce 'said alkalinity, hydroxyl ions migrating from the cathodic sections into the anodicsections and reducing the acidity of the anolytes. l Y

41. The herein described method of reducing a sugar solution to the corresponding alcohol which consists of agitating said solution together with the mercury cathode of an electrolysis cell and controlling the rate of agitation in accordance With the indicated voltage of-said cell.

In testimony whereof he aiixes his signature.

HENRY JERMAIN CREIGHTON.-

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