US3657099A

US3657099A - Electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile

Info

Publication number: US3657099A
Application number: US33630A
Authority: US
Inventors: Maomi Seko; Akira Yomiyama; Tetsuya Miyake; Koji Nakagawa; Muneo Yoshida; Koji Inada
Original assignee: Asahi Chemical Industry Co Ltd
Current assignee: Asahi Kasei Corp; Asahi Chemical Industry Co Ltd
Priority date: 1969-05-07
Filing date: 1970-05-01
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18
Also published as: BR7018862D0; FR2042464A1; GB1312319A; NL151447B; DE2022696A1; DE2022696B2; NL7006605A; DE2022696C3

Abstract

An electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile, which comprises one or more sets of an anode plate, a cation exchange membrane and a cathode plate superposed with each other, and at least one duct formed between said anode plate and said membrane and between said cathode plate and said membrane through which electrolyte is passed at a high flowing rate, said duct having at least one turning portion which is positioned outside of an electric current path flowing across the anode and cathode plates.

Description

United States Patent Seko et al. [451 Apr. 18, 1972 [54] ELECTROLYTIC CELL FOR 204/269, 275

PRODUCING ADIPONITRILE BY ELECTROLYTIC [56] References Cited HYDRODIMERIZATION OF UNITED STATES PATENTS ACRYLONITRILE 2,708,658 5/1955 Rosenberg ..204/257 [72] Inventors: Maomi Seko, Tokyo; Akira Yomiyama, 3,084,113 4/1963 Vallino; ..204/263 Nobeoka; Tetsuya Miyake, Nobeoka; Koji Nakagawa, Nobeoka; Muneo Yoshida, Nobeoka; Koji Inada, Nobeoka, all of Japan Assignee: Asahi Kasei Kogyo Kabushiki Kaisha,

Osaka, Japan Filed: May 1, 1970 Appl. No.: 33,630

Foreign Application Priority Data May 7, 1969 Japan ..44/34499 US. Cl. ..204/253, 204/73 A, 204/263,

204/269 Int. Cl ..B0lk 3/10 Field of Search ..204/73 A, 245, 253, 257, 263,

Primary ExaminerJohn l-l. Mack Assistant Examiner-W. I. Solomon Attorney-Flynn & Frishauf [5 7] ABSTRACT An electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile, which comprises one or more sets of an anode plate, a cation exchange membrane and a cathode plate superposed with each other, and at least one duct formed between said anode plate and said membrane and between said cathode plate and said membrane through which electrolyte is passed at a high flowing rate, said duct having at least one turning portion which is positioned outside of an electric current path flowing across the anode and cathode plates.

10 Claims, 16 Drawing Figures PATENTEDAPR 18 I972 SHEET 1 BF 5 nu m C! PATENTEDAPR 18 m2 8, 657. 099

SHEET 20F 5 FIG. I d

l6 8 9 IO LL 5 W \1 k u PATENTEDAPR 18 m2 SHEET 3 OF 5 FIG. 3b

PATENTEDAPR 18 I972 SHEET H 0F 5 fi L FIG. 4b

ELECTROLYTIC CELL FOR PRODUCING ADIPONITRILE BY ELECTROLYTIC HYDRODIMERIZATION OF ACRYLONITRILE The present invention relates to a construction of an electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile.

Methods for producing adiponitrile by electrolysis of acrylonitrile have been publicly known in the art, as disclosed in Japanese Pat. Nos. 4733/ 1965 and 11249/1966. Upon con ducting tests we have found that these conventional methods have some limitations in industrially practicing the same, as hereinafter described.

When producing adiponitrile by electrolytic hydrodimerization of acrylonitrile, acrylonitrile and adiponitrile are easily oxidized to be lost and hydrogen cyanide gas is produced at the anode area of an electrolytic cell. Furthermore, gaseous mixtures of oxygen and acrylonitrile produced at the anode area may cause explosion, which is dangerous Accordingly, it is desired to separate anode and cathode chambers by means of a sheet of membrane.

When producing adiponitrile by reduction of acrylonitrile, a surface of the cathode becomes alkaline, and at this surface layer bis-cyanoethyl-ether is produced by reaction of acrylonitrile and water. Further hydrolysis products of acrylonitrile and adiponitrile and propionitrile are produced at this surface layer.

In order to prevent the production of these by-products, it is necessary to reduce the thickness of the alkaline surface layer formed at the cathode surface to be as thin as possible. For this purpose, it is desired that flowing rate of catholyte on the cathode surface is maintained above cm./sec., and preferably above 1 m./sec.

An electrolytic cell having large capacity which can be used in industry is advantageously made in a dual-electrode type construction. A dual-electrode type electrolytic cell includes a plurality of unit cells which are superposed with each other and electrically connected in series, and consequently high voltage can be applied thereto, so that rectification efficiency is increased, with a transformer having reduced capacity, which is economical. However, electrolyte is usually fed to the cells of the respective units separately, so that current leakage may occur through pipings for feeding the electrolyte. The current leakage is of course undesirable in itself because it produces loss of current, and it is particularly undesirable for electrolysis of acrylonitrile because hydrogen cyanide and the explosive oxygen and acrylonitrile gas mixture may be produced and a part of the piping may be abnormally corroded since a part of cathode works as an anode because of the current leakage. If highly conductive liquid such as sulfuric acid is used as anolyte the current leakage is further increased and a dangerous gas mixture of hydrogen and oxygen may be produced.

In order to reduce the current leakage it is necessary to use a finer and longer tube to feed the electrolyte to each unit cell, and consequently the volume of electrolyte to be fed to each unit cell must be minimized.

In order to reduce the flow rate of the electrolyte, it is required to provide a device for holding the distance between the membrane and the electrode surface as constant and narrow as possible. It is preferable to provide a tortuous duct for passing the electrolyte on the electrode surface.

In the hydrodimerization of acrylonitrile, it has been found that if there is local stagnation of electrolyte owing to eddy current caused in the duct, a deposit of polymerized acrylonitrile on the electrode surface appears, and such deposit increases the eddy current, thereby further increasing the deposit. Even if the deposit of polymer may be relatively thin in the order of 0.2 mm. thickness, it acts to reduce largely the feeding rate of acrylonitrile to the electrode surface and increase the by-product of propionitrile above 5 percent, thus reducing the yield of adiponitrile. Accordingly, it is required that no obstacle which may cause eddy current exists in the passage of the catholyte on the cathode surface. It is also required that the duct has no abruptly curved portion therein.

It is preferable that the duct for passing electrolyte on the cathode surface comprises only straight portions through which the electrolyte uniformly flows.

It is an object of the present invention to provide a novel electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile.

It is another object of the present invention to provide an electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile which eliminates all of the above-mentioned disadvantages.

The other objects and advantages will be apparent from the description which will be made with reference to the accompanying drawings.

Among the known electrolytic cells for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile, a typical one is disclosed in Dutch Pat. No. 6,707,472, in which electrolyte flows in passages which are arranged in the same direction in parallel relationship and restrictions are provided at inlet and outlet ports of these passages to hold the flowing rate uniform through said passages. In such construction, the volume of the electrolyte passing through the unit cell is relatively large, resulting in increase of pressure loss.

An example of the known electrolytic cells including curved ducts is disclosed in US. Pat. No. 2,708,658. The cell has a curved duct which is arranged between a pair of ion-exchange membranes, instead of being formed between a membrane and an electrode plate, for the purpose of desalting solution, so that this cell has no defect of producing polymer even if electric current is passed through the turning portion of the curved duct. Thus, in the construction of this US. Patent, the electric current is passed through the turning portions of the duct.

Other electrolytic cells have been known in the art, but any of them cannot solve all of the problems mentioned above. These problems can be solved by the present invention.

In accordance with the present invention, the electrolytic cell comprises an anode chamber and a cathode chamber separated by a membrane, the cathode chamber providing at least one duct for passing electrolyte, said at least one duct preferably having a rectangular shape in the cross section and being formed by the electrode, the membrane and a spacer for holding uniform the distance between the electrode and the membrane, with no obstacle being formed in said duct. The duct has a width of 0.5 to 50 cm. in the direction of flow therein. The duct has at least one turning portion so that the entire length of the duct in the perpendicular direction of flow is made longer than the length of one side of the electrode, and electric current is applied only on the straight portions of the duct.

Further, in accordance with the present invention the electrolytic cell is a dual-electrode type cell in which a duct for passing electrolyte comprises straight portions situated on the cathode surface and turning portions around the periphery of the electrode, so that electric current does not pass through the turning portions. Such arrangement provides the entire length of the passage of electrolyte on the electrode surface which is substantially longer than the length of one side of the electrode. By this construction, the electrolyte on the cathode surface can be held at high flowing rate, while the volume of the electrolyte fed to the cell is relatively small.

Various electrolysis methods, such as using homogeneous solution or emulsion, have been known in the art. The present invention can be applied to any of the methods.

Although the membrane may be made of any material which can prevent acrylonitrile and adiponitrile from diffusing into the anode chamber and has high conductivity, a cationexchange membrane is preferred. A sulphonic type cationexchange membrane based on styrene-divinyl benzene is superior in chemical stability and mechanical strength, and can be used in a reinforced form with any reinforcement such as glass fiber or a homogeneous form having no reinforcement. Preferably, the membrane having thickness of 0.5 to 2 mm. is used to prevent the diffusion of acrylonitrile or other material and to provide necessary mechanical strength.

The cathode may be made from lead, lead alloy, cadmium, zinc, carbon or the like. More particularly, lead-antimony, lead-silver, lead-antimony or like alloys which can be also used as anode material may be advantageously used in the dual-electrode type cell since such material can be used as an anode at one side and as a cathode at the other side.

The anode may be made from lead peroxide, lead, lead alloy such as lead-antimony, lead-silver, lead-antimony-silver or ferrous oxide, carbon, platinum or the like.

The anolyte is preferably an acidic solution, particularly, sulfuric acid solution, where lead alloy which is superior in corrosion resistant property is used as the anode material.

In a dual-electrode type cell, an electrode acts as an anode at one side and a cathode at the other side, so that the electrode can be made as a single piece when the same material is used as the anode and cathode. When the material of the anode and that of the cathode are different from each other, the anode and cathode plates are connected together to form a dual-electrode.

In order to form the turning portions of the duct at the outside of the electrode plate, an electrode frame of insulating material may be provided, which has an anode plate and a cathode plate attached to the opposite sides of said frame and electrically connected together by a rod passing through the frame.

Preferably a spacer may be provided to hold the cathode plate and the membrane at uniform distance. If the distance between the cathode plate and the membrane is extremely small, there is a danger of these parts coming into contact with each other, while if the distance is extremely large the required voltage is increased and the required volume of flow is also increased. The desired distance is between 0.5 and mm.

To form an electrolyte path on the cathode surface which is straight and has no obstacle, the spacer contacting with the cathode surface is made in the form of a straight strip arranged in parallel relationship. The strip has practically 2 to 20 mm. width. If the distance between the strips is too great, the membrane may come into contact with the electrode, while if the distance is to little, the pressure loss is excessively increased. Therefore, the preferable distance is 0.5 to 50 cm.

The duct is formed between the strips which serves as spacers positioned between the cathode plate and the membrane. The catholyte flows in the duct as a straight flow.

The length of one side of the electrode is about 20 cm. to 2 m., in industrial equipment. In the construction according to the present invention, the flow of the electrolyte has at least one turning portion so as to make the entire length of the duct longer than the length of said one side of the electrode, and the turning portion is positioned at the outside of the cathode plate, so as to prevent electric current from passing through the turning portion. The turning portion may be provided within the thickness of the spacer, or it may be carved in the electrode frame outside the periphery of the electrode plate. In the latter case, it is essential to form the duct in such shape that the eddy current produced in the turning portion exerts substantially no effect over the flow in the straight portions.

The turning portions and the straight portions may be connected successively so as to form a single duct, but pressure loss may be excessively increased in a large scale electrolytic cell. In such a case, two or more sets of ducts may be provided.

The feeding pressure of the electrolyte should be maintained below kg./cm. at the inlet side.

The anode chamber is preferably made in the similar construction with that of the cathode chamber. If the both constructions are identical, the pressure losses in these chambers are equal when the flowing rates are maintained at the same value, so that the differential pressure acting on the membrane becomes null.

It is desired to minimize the differential pressure across the membrane so that the membrane having decreased mechanical strength and increased electrical conductivity can be used. The differential pressure should be below 1 kg./cm. preferably below 0.3 kg./cm.

The anode chamber requires less accuracy than the cathode chamber, so that a reinforcing porous plate or screen may be set in the anode chamber at the side of the membrane for the purpose of facilitating the discharge of gas or sludge produced in the anode chamber.

The electrolyte can be fed into the anode and cathode chambers through noales provided around the electrode frame. The respective nozzles are connected to conduits having sufficiently long distance and sufficiently small diameter to maintain the current leakage outside of the cell to low value, and the electrolyte is fed through a header thereto. The current leakage is preferably maintained at 5 percent or less.

In another construction, conduits may be formed in the peripheral portions of superposed unit cells, and slits may be formed to connect said conduits to the ducts on the cathode and anode surfaces, whereby the catholyte and anolyte can be fed. In order to reduce the current leakage the slits should be as long and fine as possible.

The spacer, the electrode frame and the conduits may be made from any material which is electrically insulating and corrosion-resistant to the catholyte and anolyte, such as polypropylene, rubber, heat-resistant vinyl-chloride, vinylchloride or the like.

The accompanying drawings illustrate several embodiments of the present invention, in which:

FIGS. 1a, 1b, 1c and 1d illustrate a first embodiment of the present invention, FIG. 1a being an exploded perspective view of the electrolytic cell, FIG. 1b being an exploded perspective view of one set of components of the cell, namely electrode plates, spacers and a membrane, FIG. 1c being front views of these components and FIG. 1d being an enlarged sectional view of the set of the components;

FIGS. 20, 2b and 2c illustrate a second embodiment of the present invention, FIG. 20 being an exploded perspective view of one set of components of the electrolytic cell, FIG. 2b being front views of these components and FIG. 2c being an enlarged sectional view of the set of the components;

FIGS. 3a, 3b and 3c illustrate a third embodiment of the present invention, FIG. 3a being an exploded perspective view of one set of components of the electrolytic cell, FIG. 3b being front views of the components and FIG. 30 being an enlarged sectional view of the set of the components;

FIGS. 4a, 4b and 4 c illustrate a fourth embodiment of the present invention, FIG. 4a being an exploded perspective view of one set of components of the cell, FIG. 4b being front views of the components and FIG. 40 being an enlarged sectional view of the set of the components; and

FIGS. 5a, 5b and 5c illustrate a fifth embodiment of the present invention, FIG. 5a being an exploded perspective view of a set of components of the cell, FIG. 5b being front views of the components and FIG. 5c being an enlarged sectional view of the set of the components.

Now the invention will be explained, with reference to the drawings. FIGS. la, 1b, 1c and 1d illustrate a first embodiment of the invention. Referring to FIGS. 1a and lb, the electrolytic cell includes electrode frames 1, spacers 2 and cationexchange membranes 3. Referring to FIGS. 10 and 1d, the frame 1 comprises a board 8 of insulating material and electrode plates 9 fitted in both sides of said board 8 in flush therewith. The electrode plates 9 are electrically connected together by a conductive rod 10 passing through the board 8. The electrode frame 1 has feeding and discharging nozzles 16 at its periphery, through which tunnel-like feeding and discharging

ports

11 and 12 extend to the surface of the electrode. The spacer 2 is made of a thin plate of insulating material having substantially the same size as the frame 1 and having a cut-out portion 20 therein to form a duct 19. When the frames 1, the spacers 2 and the cation exchange membrane 3 are superposed successively, the respective cut-out portions are enclosed between the electrodes and the membrane to form the duct 19 for the electrolyte.

The duct 19 forms essentially one flowing path which leads from the feeding port 11 to the discharging port 12 and includes at least one turning portion, the length of said path being substantially longer than that of one side of said electrode frame. When the electrode frame 1 and the spacer 2 are superposed with each other, the turning portions are formed at the outside of the electrode plate 9, so that electrolysis occurs only in the straight portions of the duct 19. Although the width and the thickness of the duct 19 depend on the conditions of the electrolysis and the property of the cation exchange membrane, the width within the range from 0.5 to 50 cm. and the thickness within the range from 0.5 to 5 mm. are employed in practical use. The thickness of the duct 19 is substantially equal to that of the insulating plate 18 used for the spacer 2,

The electrolytic cell is fabricated from the above components, as will be described below. First of all, a pair of press heads 6 are put with a substantial space therebetween and a pair of anode and cathode frames 4 and 5 respectively are put inside of said press heads 6, as shown in FIG. 1a. Each of the anode and cathode frames 4 and 5 respectively has an electrode plate 9 fitted in one side thereof. Then, the spacers 2, the cation-exchange membranes 3, the spacers 2 and the electrode frames 1 are put in this order successively and they are pressed together by means of the press heads 6 to form the electrolytic cell. Although one electrolytic cell may include two to several hundred electrode frames to obtain desired capacity, it is preferable in practical use that the one cell includes less than two hundred electrode frames.

The above electrolytic cell can be used to perform the electrolytic hydrodimerization of acrylonitrile, as follows.

Direct current is applied across the anode and cathode frames 4 and 5, respectively while the catholyte and the anolyte are being fed to a cathode chamber 22 formed by the duct 19 enclosed between the cation-exchange membrane and the cathode, and an anode chamber 23 adjoining to said cathode chamber, respectively. The electrode plates 9 fitted in the electrode frame 1 forms a cathode when it confronts the anode frame 4, while it forms an anode when it confronts the cathode frame 5. In the above construction of the electrolytic cell, no obstruction is formed in the duct 19 and there is no restriction therein as in the electrolytic cell disclosed in Dutch Pat. No. 6,707,472, so that any kind of electrolyte can be used. There is no stagnation of gas or accumulation of precipitate on the electrode surface owing to the electrolyte flowing on the electrode surface at high flowing rate, above 10 cm./sec. and preferably above 1 m./sec. Therefore, the electrolytic cell can be used in horizontal position as shown in FIG. 1, vertical position or inclined position at any angle,

The distribution of the electrolyte to the electrolytic cell can be made by headers for the anolyte and the catholyte through flexible tubes leading to the respective electrode frames. In order to prevent the current leakage, the flexible tubes must be as long and small in cross section as possible. In the construction according to the invention, the flexible tubes can be made sufiiciently long in length and small in diameter to reduce the current leakage to negligible value, since the volume of the electrolyte flowing one electrode chamber is substantially small.

FIGS. 2 and 3 illustrate modified forms of the electrolytic cell according to the present invention.

FIG. 2 illustrates a construction which is substantially similar to that shown in FIG. 1, except that portions corresponding to the turning portions of the duct 19 in the spacer 2 shown in FIG. 1 are formed by grooves 14 carved in an electrode frame 1 and a spacer 2 is formed in a shape of a ladder as shown in FIG. 21).

FIG. 3 illustrates another construction in which a portion corresponding to the spacer 2 is formed as an integral part of an electrode frame 1, and consequently an electrolytic cell is constituted from two components, namely, electrode frames 1 and cation-exchange membranes 3. Electrolyte passing through a duct 19 flows into a groove 14 formed in the frame at the end of said duct, where it reverses its flowing direction and then flows into a next duct 19. Thus, the electrolyte fed to a feeding port 11 at one end of the electrode frame flows through an essentially single duct having at least one turning portion and it is discharged through a discharging port 12.

In the construction of the electrolytic cell as shown in FIGS. 1, 2 and 3, the width of the duct 19 depends mainly on the surface area of the electrode and the entire length of the duct as required. If the cation-exchange membrane 3 has not sufficient strength to maintain the required width of the duct, one or more fine strips 21 are provided in the duct to prevent the deformation of the membrane. The strip used for such purpose may be made of fine insulating material having the same thickness as that of the spacer 2 and width of 3 to 20 mm., and positioned in parallel with the flowing direction.

FIGS. 4 and 5 illustrate other forms of the electrolytic cell according to the present invention, which are somewhat different from those shown in FIGS. 1 to 3.

FIG. 4 shows a construction in which an electrode frame 1 is formed of a single electrode plate 9 having feeding and discharging conduits 15 at its peripheral portion. The electrode plate forms an anode at its one side surface and a cathode at its other side surface when current is applied thereto. A spacer 2 used in this construction is made of a thin plate having a cut portion 20 to form a duct 19 having at least one turning portion, which is substantially identical with that shown in FIG. 1, and said spacer has conduits 15 as shown in FIG. 4b. In this construction, a shield plate 7 having a central opening and feeding and discharging conduits 15 at its peripheral portion is positioned between the spacer 2 and the electrode plate 9, so that the turning portions of the duct 19 are shielded from direct current applied to the cell. The shield plate 7 is made of a thin insulating plate having a thickness of 0.05 to 0.2 mm.

The electrolytic cell is fabricated by setting a pair of press heads 6, putting an anode plate 4 and a cathode plate 5 inside of said press heads, in the same manner as shown in FIG. 1, then putting the shield plate 7, the spacer 2, the cationexchange membrane 3, the spacer 2, the shield plate 7 and the electrode plate repeatedly in this order between said anode and cathode plates and pressing these parts together by said press heads. The electrolyte is fed to the respective chambers of the cell through the feeding and discharging conduits 15 and the nozzles 16 extending through the press heads 6. The feeding and discharging conduits extending through the electrode plates 9 must be completely sealed by means of seals 17 at the area contacting with the electrolyte passing through the conduits, in order to prevent the electrolyte from contacting with the electrode plates, which may cause electrolysis.

FIG. 5 illustrates another form of the electrolytic cell according to the present invention, which is a modified form of FIG. 4. In the form shown in FIG. 5, an electrode frame 1 made from insulating material has a central opening, into which an electrode plate 9 having the same thickness as that of the electrode frame is fixed. The electrolytic cell includes spacers 2 and cation-exchange membranes 3 which are identical with those shown in FIG. 4. The electrode plate 9 has such dimensions as to sufficiently cover only straight portions of a duct 19 to prevent current from flowing through turning portions of the duct. The electrode plate is formed as an integral piece which acts as an anode at one side and a cathode at the other side. The electrode plate 1 has conduits 15 at its peripheral portion, as shown in FIG. 5b, through which electrolyte is fed to the respective chambers.

It will be understood from the above description that a shield plate 7 such as shown in FIG. 4 is not required in this construction. Therefore, the electrolytic cell includes three components, namely, the electrode frames 1, the spacers 2 and the cation-exchange membranes 3, which are repeatedly superposed with each other to form a cell having any desired capacity. Although a single electrolytic cell can be formed from two to several hundred electrode plates, it is preferably made from less than two hundred plates in practical use.

Now, the invention will be explained with reference to typical examples.

EXAMPLE 1 The electrolytic cell as shown in FIG. 3 has been operated under the following conditions.

Electrode frame Material: polypropylene Size: 1,300 X 1,300 X 20 mm.

Electrode plate (anode & cathode) Material: hard lead Size: 1,220 X 1,140 X 4 mm.

Spacer Material: polypropylene Size: 1,300 X 1,300 X 2 mm.

Passage: Width-40 mm.

Entire length-27.30 m. Number-24 Current passing area-109 dm.

Cation-exchange membrane Material: sulphonate type strong acidic ion exchange membrane based on butadiene copolymer Size: 1,280 X 1,280 X 1.2 mm.

Catholyte Material: aqueous solution containing acrylonitrile and tetraalkyl ammonium salt as supporting salt Flowing rate: 600 l./hr./chamber Anolyte Material: 2N aqueous solution of sulphuric acid Flowing rate: 550 l./hr./chamber Number of chambers 40 pairs Current 2,200 amp.

After the electrolytic cell was operated for about 1,000 hours under the above conditions, adiponitrile was produced in the catholyte at the rate of 145 kg. (average)/hour. The pressure drop of the catholyte in the cell was 2.8 kg./cm. while the pressure drop of the anolyte was 2.9 kg./cm. The variation of the flowing rate between the respective chambers was below 3 percent, and consequently extremely uniform distribution of the flowing rate was obtained. After operation, no accumulation of precipitate was found in the electrolytic cell.

EXAMPLE 2 The electrolytic cell and the conditions of operation in Example l were modified as follows:

Spacer Size: 1,300 X 1,300 X 2 mm.

Passage: Width- 140 mm.

Entire length-9.12 m.

Number-8 Two strips each having width of 10 mm. and length of 1,140 mm. were inserted in one duct.

Current passing area-109 dm.

Catholyte Flowing rate: 1.7 M /hr./chamber Anolyte Flowing rate: 1.6 M /hr./chamber Number of chambers 10 pairs Current 2,200 amp.

After the cell was operated for about 400 hours under the above conditions, adiponitrile was produced at the rate of 48 k g.(average)/ hour. After operation, no accumulation of precipitate was found in the cell.

EXAMPLE 3 The electrolytic cell as shown in FIG. 5 was operated under the following conditions.

Electrode frame Outer frame Material: polypropylene Outside size: 1,000 X 1,000 X 6 mm. Inside size: 820 X 810 mm.

Electrode plate Size: 838 X 828 X 6 mm. Conduits Number: 1 for feeding anolyte l for discharging anolyte 1 for feeding catholyte l for discharging catholyte Size: 80 X 30 mm.

The outer frame and the electrode plate were connected by stepped joint, with packing material inserted therein to prevent leakage.

Spacer Material: polypropylene Size: 1,000 X 1,000 X 2 mm.

Passage: Width-25 mm.

Number-22 Entire length17.8 In. Current passing areaea-44 clm.

When the electrode frame and the spacer were superposed as shown in FIG. 5, the turning portions of the duct were positioned at the peripheral portion of the electrode frame. Thus current passes only through the straight portions of the duct.

Cation-exchange membrane Material: same as Example 1.

Size: 980 X 980 X 1 mm.

Catholyte Material: same as Example 1.

Flowing rate: 380 l./hr./chamber Anolyte Material: same as Example 1.

Flowing rate: 350 l./hr./chamber Number of chambers 20 pairs Current 900 Amp.

After the cell was operated for about 300 hours under the above conditions, adiponitrile was produced at the rate of 31 kg.(average)/hour. After operation, no accumulation of precipitate was found in the electrolytic cell.

When the above electrolytic cell was operated for about 300 hours while applying current across the turning portions of the duct, the yield of adiponitrile was lowered and the volume of by-product, such as propionitrile and biscyanoethyl-ether was increased. After the operation, accumulation on the cathode of 780 mg.(average) per chamber was found around the turning portions.

Average yields of material when current was passed across the turning portions and those when no current was passed were as follows.

Current passing across turning portions 1. An electrolytic cell for producing adiponitrile by electrolytic hydrodimerization of acrylonitrile, comprising at least one set of an anode plate, a cathode plate and a membrane superposed between said anode and cathode plates, and at least one duct formed between said membrane and said cathode plate, said at least one duct having at least one turning portion therein to form a substantially longer path for flowing electrolyte than the length of one side of said plate, said turning portion being positioned outside of the path of the current applied across said anode and cathode plates.

2. An electrolytic cell according to claim 1, in which said membrane is a cation-exchange membrane.

3. An electrolytic cell according to claim 1, in which the distance between said cathode plate and said membrane is 0.5 to 5 mm.

4. An electrolytic cell according to claim 1, in which said at least one duct has straight portions arranged in parallel relationship.

5. An electrolytic cell according to claim 1, in which said at least one duct has a width between 2 mm. and 20 mm.

6. An electrolytic cell according to claim 1, in which the turning portions are formed in peripheral portions of the cathode plate outside of the path of the current applied across said anode and cathode plates.

7. An electrolytic cell according to claim 6, in which the turning portions of said at least one duct are in the shape of grooves.

8. An electrolytic cell according to claim 1, in which at least one duct is formed by a spacer having a cut-out portion, said spacer being positioned between said membrane and said

Claims

2. An electrolytic cell according to claim 1, in which said membrane is a cation-exchange membrane.
3. An electrolytic cell according to claim 1, in which the distance between said cathode plate and said membrane is 0.5 to 5 mm.
4. An electrolytic cell according to claim 1, in which said at least one duct has straight portions arranged in parallel relationship.
5. An electrolytic cell according to claim 1, in which said at least one duct has a width between 2 mm. and 20 mm.
6. An electrolytic cell according to claim 1, in which the turning portions are formed in peripheral portions of the cathode plate outside of the path of the current applied across said anode and cathode plates.
7. An electrolytic cell according to claim 6, in which the turning portions of said at least one duct are in the shape of grooves.
8. An electrolytic cell according to claim 1, in which at least one duct is formed by a spacer having a cut-out portion, said spacer being positioned between said membrane and said cathode plate.
9. An electrolytic cell according to claim 8, in which the turning portions of said at least one duct are provided within the thickness of the spacer.
10. An electrolytic cell according to claim 1, in which a reinforcing porous plate is provided at the anode side on said membrane.