US2324002A - Electrolytic cell - Google Patents

Description

y 3, 1943. D. J. KENNEDY ETAL ELECTROLYTIC CELL 30, 1940 2 Sheets-Sheet 1 Filed Nov lNvENToRs Douqms Joszpn KENNEDY WALTER EqsERT BARKER Q M ATTORN EY July 13,1943.

D. J. KENNEDY ETAL ELEGTROLYT I C CELL -Filed Nov. 30, 1940 2 Sheets-Sheet 2 FIG. 3.

GRAPH/76' GRAPH! TE ANODE rm u. h fl l. 2 1m I I I r I Douams JOSEPH KENNEDY WALTER Eeazm- BARKER W ATTORNEY Patented July 13, 1943 2,324,002 ELECTROLYTIC CELL Douglas Joseph Kennedy and Walter Egbert Barker, Shawinigan Falls, Quebec, Canada, assignors to Shawinigan Chemicals Limited, Montreal, Quebec, Canada, a corporation of Canada Application November 30, 1940, Serial No. 368,068 In Canada September 10, 1940 3 Claims.

This invention relates to an electrolytic cell.

Objects It is a principal object of the invention to provide a device of this nature having an arrangement of electrodes and semi-permeable diaphragms allowing separate circulation into and out of the cell of both anolyte and catholyte, with a minimum of intermixing and with no exposure of the electrolytes to the atmosphere.

It is a further object of the invention to provide an electrolytic cell in which the current efficiency is extremely high for the type of electrolytic process for which the cell is designed.

With these and other objects in view, a preferred form of cell according to the invention is featured by a combination of headers, tubular coaxially disposed anodes, cathodes and semipermeable diaphragms, and connections thereto. The arrangement is such that a catholyte solution may be made to flow out of contact with the atmosphere from a storage container into the cell between the cathodes and semi-permeable cliaphragms, and then back to the storage container; at the same time the anolyte solution may be circulated from a second storage tank through hollow anodes and between theirsurfaces and the semi-permeable diaphragms back to the storage tank. In this manner, both catholyte and anolyte solutions may be continuously withdrawn from the cell for the utilization of the electrolysis products and for replenishing the raw materials of the electrolysis. The cell may be .provided with an outer casing in which a cooling liquid may be circulated.

Having thus generally described the invention, reference will now be made to the accompanying drawings which illustrate a preferred form of cell according to the invention, and in which:

Figure 1 is an elevation of this cell with the casing partly removed to show the cathodes.

Figure 2 is a plan view of the cell shown in Figure 1.

Figure 3 is a vertical cross section taken along the line 3-3 of Figure 2.

Detailed description More detailed reference will now be made to the drawings. The cell includes a circular catholyte inlet header III of rubber-covered steel, Karbate, hard rubber, or some other material resistant to chlorides. The header Ill is provided with an inlet pipe l5 and also includes outwardly extending flanges II, to which are connected by means of bolts l2, 9. lower impregnated graphite cathode tube sheet 20. A number of impregnated graphite tubular cathodes 30, leading from the catholyte inlet header III, are set in openings in the tube sheets 20 and extend upwardly therefrom to meet an upper impregnated graphite tube sheet 40. The cathodes are cemented within openings in the upper and lower tube sheets with electrically conductive cement.

A catholyte outlet header 50 has a lower flange 5| connected by bolts 52 to the tube sheet 40. The header 50 is provided with an outlet tube 55. The header 50 also includes an upper flange 53 upon which there is mounted an impregnated graphite anolyte header 6!]. Above the anolyte header is mounted an impregnated graphite anode tube sheet 10, the header 50 serving to insulate the tube sheets 40 and 10 from one another. Extending downwardly from the tube sheet 10 are hollow cylindrical graphite anodes 80 which are co-axially arranged within the cathodes 30, these anodes being secured at their upper ends to bushings 8| screwed into threaded openings in the tube sheet 10. Electrically conductive cement completes the joint between the anodes, bushings and tube sheet.

Mounted on the anode tube sheet 10 is an impregnated graphite gas dome 90 having a flange 9']. Bolts Hi0 extend downward through the flange 9 I and also the anolyte header 60, the tube sheet Ill and the flange 53 of the header 50, thus connecting all these parts together.

A number of semi-permeable tubular diaphragms H0 are mounted with their top ends sealed in openings in the anolyte header 60, and extending downwardly therefrom. Rubber stoppers III areset in depressions in the anolyte header 60, to engage the ends of the diaphragms 0. Each of these diaphragms extends downwardly co -axially between an anode and a cathode, and is closed at the bottom. A spacer I I2 at the bottom of each diaphragm holds a respective anode co-axial with the diaphragm. On the top of the header l0 and separating the chamber which it forms from the lower ends of the diaphragms is a perforated plate I! of porcelain or any porous non-conducting chloride resisting material. This plate serves to support the weight of the diaphragms.

The anolyte header is provided with an impregnated graphite gas outlet pipe 6| leading to the gas dome. An anolyte inlet tube 62 extends through the gas dome. An impregnated gas outlet pipe 63 also leads from the gas dome to permit collection of the gas. The anolyte header is also provided with an outlet 65 for the anolyte.

(not shown in the figure).

The positive electrical connection is made with the anode tube sheet 10, which is an electrical conductor leading to the anodes. The negative connection is made with the cathode tube sheet 40, which is a conductor leading to the cathodes.

A cylindrical casing I20 extends between the tube sheets 20 and Hi forming a compartment in which a fluid for cooling the electrodes may be circulated.

Operation The operation of the cell will be better undenstood by a description of its use in the production. of chromous chloride and chlorine as intermediates in the manufacture of ethylene chlorhydrin. It must, however, be understood that the invention is in no way limited to this particular use.

In the process of producing ethylene chlorhydrin, an aqueous solution of chromic chloride (CrCla) is pumped from a storage tank into the catholyte inlet header I I]. The catholyte is caused to flow from the header up between the surfaces of the cathodes, and the semi-permeable diaphragms 0, into the catholyte header 50, and then through the outlet 55 to the catholyte tank.

The anolyte, a solution of hydrochloric acid which may contain. some chromic chloride, is made to flow into the .anolyte inlet header by way of the inlet tube 62. The anolyte flows by gravity down through the hollow anodes 80 and then up between their outer surfaces and the semi-permeable dlaphragms H into the anolyte outlet header 60 and thence from the anolyte outlet tube 65 to the anolyte storage tank.

An electrical current is passed through the cell from the connections to the tube sheets 40 and 10.

Due to the electrolytic action which takes place chloride ions are discharged at the anode and chlorine gas is evolved, while at the cathode hydrogen ions are discharged which are immediately'consumed in the reduction of the chromic chloride to chromous chloride. Any hydrogen not consumed in the said reduction will be evolved as gaseous hydrogen and will leave the cell with the catholyte solution.

At the anode surfaces, chlorine gas is evolved and passes from the anolyte header, through the pipe it, into the chlorine dome, whence it is collected from the outlet pipe 63.

The anolyte, during its passage through the cell, becomes somewhat depleted of hydrochloric acid, due to the evolution of chlorine gas. It is therefore, made to circulate continuously through an absorber (not shown in the figure) countercurrent to a stream of hydrogen chloride gas so that the hydrochloric acid content of the anolyte is continuously replenished.

The catholyte is passed, countercurrent to a stream of acetylene, through a reactor tower By this means the acetylene is hydrogenated to ethylene and the chromous chloride oxidized to chromic chloride. The catholyte is also passed countercurrent to a stream of hydrogen chloride in" an absorber. This is to replenish the chloride ions lost by the catholyte during its passage through the cell,

when some chloride ions migrated through the.

diaphragms to the anodes. The ethylene and the chlorine are, subsequently reacted toform ethylene chlorhydrin.

It should be observed that the continuous production of chlorine and chromous chloride can be carried out economically only in an electrolytic cell possessing the structural features and arrangement of electrodes and diaphragms peculiar to the cell herein described. Essential conditions for this process fulfilled by our cell are:

(l) Passage of both the catholyte and the anolyte into and out of the cell. In this way not only is the chromous chloride available for the hydrogenation of acetylene at a point outside of the cell, but both catholyte and anolyte may be conveniently enriched with hydrogen chloride.

(2) A minimum of intermixing of catholyte and anolyte. Diaphragms of low"permeability, such as those made from aluminum oxide, are required to prevent the anolyte which is highly oxidizing due to the presence of dissolved chlorine, from mixing with the catholyte. Such mixing would result in greatly decreased current efliciency.

(3) Exclusion of the atmosphere from the circulating electrolytes. The chromous chloride containing catholyte will absorb oxygen from the air and rapidly lose its reducing power i'he anolyte is saturated with chlorine gar would be lost on exposure to the atmosphere.

(4) Relatively high linear velocities of the catholyte over the surfaces of the cathodes resulting in high current efliciencies. This condition is brought about by the coaxial arrangement of our cylindrical electrodes and diaphragms with a minimum spacing between cathodes and diaphragms.

While the cell has been particularly described in connection with the production of chromous chloride and chlorine in the manufacture of ethylene chlorhydrin, the combination of its structural features may have other uses and it is not wished that the description of this particular process be taken in a limiting sense. Moreover, the description of the material from which the parts of the cell are made has been particularly for use in the above process and might vary in other uses, particularly if the electrolyte and the products of electrolysis are not corrosive.

The applicants have found that for the electrically conductive parts of the cell the following materials are suitable. The anodes are of graphite, the cathodes of Karbate, this being the trade-mark name of an impregnated graphite composition, the diaphragms are of another trade-marked product, Alfrax" which is an aluminum oxide composition. For this particular process the headers are of rubber-covered steel. The chlorine dome is of impregnated graphite as are the outlet pipes.

It will be understood that various modifications may be made in this invention without departing from the spirit thereof or thescope of the claims, and therefore the exact forms shown are to be taken as illustrative only and not in a limting sense, it being desired that only such limitations shall be placed thereon as may be imposed by the state of the prior art or are set forth in the accompanying claims.

We claim:

1. An electrolytic cell suitable for the production of chlorine and chromous chloride of the type having a plurality of electrode couples, in which the electrodes are hollow and tubular, each anode extends within the cathode for a major portion of its length, a semi-permeable diaphragm separates each anode from its cathode, comprising in combination, a gas chamber common to said plurality of'electrode couples having which openings from which the anodes extend downwardly beneath the gas chamber, an anclyte out let chamber beneath the gas chamber from which semi-permeable diaphragms extend, a catholyte outlet chamber beneath the anolyte outlet cham ber from which the cathodes extend downwardly to a catholyte inlet chamber, each anode and semipermeable diaphragm forming therebetween an anolyte passage extending from the gas chain bar to the anclyte outlet chamber, each cathode and its semi-permeable diaphragm forming therebetween a catholyte circulation passage sep arated from said anolyte circulation passage and extending from the catholyte inlet chamber to the catholyte outlet chamber, a gas exit in the gas chamber, an acolyte inlet in the gas chamher, a gas exit from the anoiyte outlet chamber to the gas chamber, an inlet to the catholyte inlet chamber, an outlet from the cathclyte outlet chamber and respective electrical connections to the anodes and cathodes,

2. An electrolytic cell suitable for the produc-: tion of chlorine and chromous chloride, compris= ing in combination, a horizontally extending gas dome, an anode tu as beneath said gas dome and connected therem, said anode tube sheet and gas dome forming therebetween an anolyte inlet chamber, an acolyte inlet in said gas dome, a gas outlet inv saidg'as dome, an insulated ano= lyte outlet header beneath. said tube sheet and connected thereto, said tube sheet and said outlet header forming therebetween an anolyte outlet chamber, a gas passage extending between said anolyte outlet chamber and said inlet chamber, a

catholyte outlet header connected to said acolyte outlet header, a cathode tube sheet beneath said catholyte outlet header, said cathode tube sheet and said inlet header forming therebetween a catholyte outlet chamber, said catholyte outlet header insulating the anolyte outlet header from the cathode tube sheet, a catholyte outlet in said catholyte outlet header, a second cathode tube sheet vertically spaced considerably apart from said first cathode tube sheet, a catholyte inlet header beneath said cathode tube sheet and com nected thereto to form a catholyte inlet chamber, a plurality of elongated tubular cathodes having respective ends set in said respective cathode tube sheets and each having an. open end communicating with said catholyte inlet and outlet chem bei's respectively, a plurality of hollow tubular dill anodes set in said anode tube sheet and each.

ers, each diaphragm extending downwardly between an anode and a cathode, each diaphragm having an open end communicating with the anolyte outlet chamber and a closed, end, each semi-permeable diaphragm and adjacent anode forming therebetween an enclosed elongated an olyte circulatlonpassage extending from the am olyte inlet header to the anolyte outlet header and separating an anode from a cathode, each cathode and its semi-permeable diaphragm form ing therebetween an enclosed catholyte circulation passage extending from the catholyte inlet chamber to the, catholyte outlet chamber, the catholyte and anolyte circulation passages being arranged for the circulation of the anolyte and catholyte out of contact with. each other and out of contact with the atmosphere, and respective electrical connections to said anodes and cath= odes,

3, An electrolytic cell suitable for the production. of. chlorine and chromous chloride, compris: ing in combination; four enclosed jfitaposed chambers including a first top chamber, a second chamber immediately below the top chamber, a third chamber immediately below the second chamber, a fourth chamber vertically spaced from and below the third chamber; a plurality" of hollow tubular cathodes extending between the third and fourth chambers, a plurality of hollow elongated anodes extending from the first chamber and passing through the second and third chambers but out of communication therewith, the interior of each anode communicating with the first chamber and being axially posi= tioned in relation to cathode and extending therewithin, a plurality of semi-permeable dia phragms each arranged to separate an anode from a cathode, each semi-permcable diaphragm having an open end communicating with the second chamber and forming with the adjacent enclosed anode an elongated anolyte passage leading from the first to the second chamber, each cathode having an open end communicating with the third and fourth chambers to form with the adjacent diaphragm an enclosed catholyte passage separated from said anolyte passage and extending between the third and fourth cham= bers, an anolyte inlet to the first chamber, an anolyte outlet from the second chamber, a. oath olyte outlet from the third chamber, a catholyte inlet to the fourth chamber, a gas outlet from the first; chamber, a gas passage from the second chamber to the first chamber and respective electrical connections to the anodes and cathodes.

DOUGLAS JOSEPH KENNEDY, WALTER EGBERT

Images