US1712951A - Electrolysis reduction cell - Google Patents

Description

May 14, 1929.

H. .1t cRElGH'roN ELECTROLYSIS REDUCTION CELL Filed March 26 Patented May 14, 1929.

.UNITI-:o STATES HENRY JERMAIN CREIGHTON, F

ATLAS .POWDER COMPANY, OF DELAWARE.

SWARTHMRE, PENNSYLVANIA,` ,ASSIGNR T0 WILMINGTON, DELAWARE, A CORPQEATIDN' lDF nLnc'rnoLYsIs nnnuo'rron entr.

This invention relates to an electrolysis cell for carrying out certain'reduction processes. lt is of particular utility in reducing sugars to alcohols, and for the purposes of explanau tion2 l will describe its construction and operation from,that standpoint. However, l desire to protect the use of this cell in every relation in which it may be found of utility, because-as this description proceeds, it will tu become apparent that any reduction which may be brought about by the use of a` sodium or other, alkali metal amalgam may be carried out to advantage in said cell.

ln my Patent 1,612,361 of December 28,

la 1926, l have claimed the process of reducing sugars to alcohols by a cell like that herein shown and described.

IThis cell is divided into two parts by a porous diaphragm. One section of this cell (the 2li cathodic section) contains a mercury cathode and means for agitating the same; the other4 section of the cell (the anodic section) contains a suitable anode material (platinum, lead dioxide, etc). lin this particular reduc- ?lll tion process, an aqueous solution of mannose containing, for example, 5% of sodium sulphate is placed in the cathodic section. il. suitable concentration for this catholyte is to sugar and 5% sodium sulphate. ln

au the anodic compartment is placed an aqueous solution of sodium sulphate, for example 5%. .las an example of the strength of the current and the voltage employed, l may mention that good results have been obtained with a current of one and one-half ampere per square decimeter .of cathode surface, the voltage varyinir between 5 and 8 volts, depending upon the temperature, rate of stirring of the mercury cathode, etc. I have found the rate Alu of stirring of the mercury cathode. to be an important factor. The more violent the agitation. of the mercury, the more rapidly the reduction of the sugar proceeds. It has also been found, however, that if the mercury is t5 stirred too violently it becomes completely broken up into tiny droplets separated one from the other by a lm of the catholyte, and this causes the resistance of the cell to increase enormously. l have observed that in t@ the operation of this process, the catholyte becomes gray and opaque due to the formation of nely divided suspended mercury, the presence of which possibly aids and accelerates Application uled March 26, 1926. Serial No. 97,783.

the reaction. l have found it desirable to agitate the mercury as vigorously as possible without undue rise in voltage. l preferably include a voltmeter X in the circuit of the cell and the operator may ed'ectively control the rate of agitation by noting the reading of the voltnieter.

f .lin the accompanying drawiner:

F ig. l is a diagrammatic, vertical sectional. view of the electrolysis cell of the present invention, and

Fig. 2 is a sectional view showing the stirrer or agitator hereinafter described.

Referring to the drawing, 5 designates a jar, or like container, constituting the main body of the cell. A body of mercury 6, disposed in the lower portion of thejar 5, constitutes the cathodic material of the cell and may dll be brought into electrical connection with the negative conductor of the'cell, by means of a metallic rod or post 7, which projects downwardly through a tube 8, made of 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. les indicative of the fact that the agitator is capable of being so rotated from the exterior of the cell, l have conventionally illustrated a pulley 10 upon the shaft 11 ofthe agitator, but it is to be understood that any suitable means of rotating the agitator may be employed. Furthermore, various forms of agitators may be` used though ll have found `the one illustrated to be very satisfactory.

This agitator comprises the straight, oppositely inclined blades 9a, 9b, the lower edges of which may, advantageously, just clear the bottom of the cell and the inclination of which is such as to thoroughly stir the mercury and catholyte Without excessive breaking up of the latter.

The anode 12 of the cell consists of a suit-v able material, such as lead or lead coated with lead dioxide. This anode is suspended in a porous cylinder 13, such as 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. plishing that result, I have illustrated a cap or cover 14, which may be of glass, hard rub- As one Way of accomber-or any other suitable material, and from which the several elements mentioned are suspended. In the use of the cell 1n con]unct1on with reducmg sugars, an aqueous solution of "mannose, or other sugar or sugars, containing An aqueous solution containing betweenl.

and 25 per cent of mannose and 5 per cent of 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 the porous cylinder 13, is surrounded with an aqueous solution containing 5l 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 land one-half aml peres for every square decimeter of cathode Vsurface is passed through the cell, the mercury cathode being vigorously agitated by the agitator 9. When 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 porous cylinder. In the cathodic section of the cell sodium ions discharge at the mercury cathode and the resulting sodium atoms unite with the mercury, forming sodium amalgam, which subsequentl decomposes the water, forming nascent hydiogen and sodium hydroxide. The nascent hydrogen formed in this way reduces the mannose to mannite. Continuous decomposi-V tion of this amalgam would tend to increase continuously the alkali (sodium hydroxide) content of the catholyte as in the 'process previously described. This continuous increase, however, is prevented by the fact that hydrogen ions migrate from the' anodic section of the cell into the cathol te and there neutralizel some of the alkali, an hydroxyl ions (alkali) -migrate from the cathol terinto the porous c linder and there neutra ize some of the acid, t e result 4of both neutralizatibns being the re-formation of sodium sulphate. In this way a limited amount of sodium. sulphate is used overand over again. The rates of migration of these ions and other conditions are such that the catholyte always remains slightly alkaline l(which is an advantao'e since lI 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. When reduction is complete the alkaline catholyte can be rendered neutral by the addition of the acid anlyte. While, as stated, the catholyte is maintained in a sometating the same,

what alkaline condition during the reduction process, the neutralization referred to may be carried to such a point that the catholyte will be almost neutral. s

DThe diaphragm is of importance because the sugar and the resulting alcohol must be prevented from coming in contact with the anode, since, otherwise, they would be oxidized. It is obvious that the diaphragm must he sufficiently porous to permit the migration of the hydrogen-ions, hydroxyl-ions and sulphate-ions and at the same time suiiciently dense to prevent the diffusion of the catholyte into the anode section, but at the same 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 action of alkali on one side and the action of acid on the other. The invention contemplates the use of such modifications and rearrangements of parts as may be found to be desirable. For example, it would be a mere matter of choice to combine a number of the cells in a battery or to multiply the diaphragms or to vary their nature, shape and arrangement. Further, I do not limit myself to the use of sodium s ulphate as an electrolyte but contemplate the use of any suitable sulphate of an alkali metal, or compound of an alkali or an alkaline earth metal, or sulphates of two or more alkali metals, or two or more suitable compounds of alkali, or alkaline earth metals and I wish it to be understood that the term sulphate of an alkali metal is used in the appended claims in its broadest significance and is intended to include the various modifications thereinvrecited.

For example, I may use potassium sulphate, sodium carbonate, magnesium sulphate, calcium nitrate,`etc.

Having described my invention, what I claim is:

- 1; An electrolysis cell of the character demercury therein constituting the cathode thereof, an agitator projecting into the mercury cathode for directly engaging and agia'porous cy inder, the interior of which constitutes the anodic section, an anode in said cylinder, an anolyte in said cylinder, and a cat olyte in the container and surrounding said cyllnder, the walls of the cylinder being ofsuch porosity as to prevent tie passage of the catholyte into the anodic section, while permitting the passage of hydrogen ions from the anodic section to the cathodic section, and the passage of hydroxyl ions from the cathodic section to the anodic section. y I A Q An electrolysis cell of the character de'- scribed, comprising a container constituting a cathode section, a porous diaphragm separating the cathodic section from the anodic section, an anode in the anodic section, said diaphragm Tooling of such porosity as to prevent ibo passage of oothoiyte into the anodic section, Wiiiio pormiitiiig the passage of hyldrogen ioi'ls from the anodio section to tino cotiiooiio section, and permittin the passago of iiydioiiyi ions fiom the cat odio section io ish@ uniodiio.socfiiony o 'bodyof mercury in

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