US3558453A

US3558453A - Preparation of alkene halides

Info

Publication number: US3558453A
Application number: US704822A
Authority: US
Inventors: Jaspal Singh Mayell
Original assignee: American Cyanamid Co
Current assignee: Wyeth Holdings LLC
Priority date: 1968-02-12
Filing date: 1968-02-12
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26

Abstract

THERE IS PROVIDED A ONE STEP ELECTROLYTIC PROCESS FOR MANUFACTURE OF MONOHALOGENATED ALKENES BY ELECTROLYZING IN AN ELECTROLYTIC CELL AN AQUEOUS SOLUTION OF A METAL HALIDE BETWEEN TWO GAS-PERVIOUS, LIQUID-IMPERVIOUS ELECTRODES. AN OXYGEN-CONTAINING GAS IS IMPINGED ON THE SURFACE OF ONE OF THE ELECTRODES WHILE AN ALKENE IS IMPINGED ON THE SURFACE OF THE SECOND ELECTRODE AND A MONOHALOGENATED ALKENE IS RECOVERED.

Description

J. S. MAYELL PREPARATION ALKENE HALIDES Jan 26, 1971 Filed Feb. 12, 1968 INVENTOR. JASPAL SINGH MA YE LL ATTORNEY United States Patent 3,558,453 PREPARATION OF ALKENE HALIDES Jaspal Singh Mayell, Stamford, Conn., assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine Filed Feb. 12, 1968, Ser. No. 704,822

' Int. Cl. C0711 9/00 US. Cl. 204-81 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a novel electrolytic process for the manufacture of alkene halides. More particularly, it relates to a method for the manufacture of monohalogenated alkenes, such as vinyl chloride, l-chloropropene-l,

1 chloro-Z-methylpropene-1, vinyl bromide and l-chloro- '4-methylpentene-l, in a'one step process utilizing an oxygen-containing gas-depolarized electrode.

In the past, a monohalogenated alkene, such as vinyl chloride, was produced by a vapor phase reaction of acetylene and hydrochloric acid to prepare said vinyl halide. Due to safety and economic considerations, however, this method has largely been replaced by a two-step process'o'f manufacture of vinyl chloride from'ethylene. In-this two' step process, ethylene can be converted to dichloroethylene by either a vapor phase reaction of "ethylene with chlorine or, more recently,'by the oxychlo- -rination process where a liquid phase reaction "of ethylene with hydrochloric acid occurs utilizing a cupric-cuprous couple as a catalyst in the presence of oxygen. The dichloroethylene made from either method is then thermally cracked and the resulting product is vinyl chloride. Because both of these ethylene reactions require two distinct chemical process steps, it has been desired to have 'a com- "rnercially feasible one step process utilizing ethylene to form vinyl chloride. For'similar considerations, the same "is true for other monohalogenated alken'es of the vinyl It is, therefore, a principal objectof this present invention to provide *anovel process for'the manufacture of monohalogenat'ed alkene compounds from' alkenes. further object is to provide an electrolytic process for a direct one step process for manufacture of monohalogenated alkene compounds. Other objects and advantages will become apparent from a consideration of'the following detailed-description. 7 v 1 An electrolytic method and cell are provided 'so as to obtain from a' brine solution with minimal power expenditure a halogen, substantially free from hydrogen, which reacts with an alkene to form the monohalogenated alkenes. In its broadestaspecflthe' method of the invention contemplates the .use of. an electrolytic cell in which (1) an aqueous metal halide solution as the electrolytic medium, (2) a plurality of gas-liquid electrodes, one of which is oxygen-containing gas-depolarized, (3) an external power source and (4) an alkene, are present so that the halogen can react with the alkene to form the desired product.

A variety of electrolytic cells can be used for effecting the processing of a brine solution according to the process of the invention. One such cell comprises a container ice which is electrically inert and which may, if desired, be provided with any suitable heating means. There is introduced through a suitable port of the container an aqueous solution of a metal halide, such as sodium chloride, sodium bromide, potassium chloride, potassium bromide and equivalent metal halides, usually ranging in concentration from about 15% to about 30%. The cell is also provided with a gas-permeable and liquid-impermeable positive electrode which constitutes the anode and a gaspermeable but liquid-impermeable negative electrode which constitutes the cathode. In assembling the overall cell, the respective electrodes are separated from each other by the electrolyte and electrically linked to an external power source. There is also provided on both the cathode side and the anode side of the container liquidimpermeable chambers into which a suitable oxygen-containing gas, such as oxygen or air, is introduced solely for the purpose of contacting the gas-permeable-liquid-impermeable cathode and into the anode chamber an alkene gas, such as ethylene, propylene, butylene, isopropylene, B-methyIbutylene-l, pentene, 4-methylpentene-l, and other equivalent alkenes, is introduced solely for the purpose of contacting the gas-permeable-liquid-impermeable anode. In operation, the cell, whose contents are maintained at temperatures ranging from 25 C. to about 100 C. and preferably between about C. and 0, forms halogen gas at the anode thereof. This halogen gas passes through the gas-permeable-liquid-impermeable electrode and contacts the alkene in the anode chamber forming the final product which is withdrawn from the cell. At the cathode side of the cell, oxygen is reduced to hydroxyl ion which then reacts with the alkali metal ions in the electrolyte to form an alkali metal hydroxide. During electrolysis, however, hydrogen gas is not evolved.

The gas-permeable-liquid-impermeable electrodes employed in this process can advantageously be prepared from an electrically conductive material, such as carbon,

.to which there is added a noble metal or other active metal catalyst. Further, a metallic screen may be impressed on the electrode and a suitable electrical lead then attached thereto. In order to avoid any electrolyte flowing into the zone when the oxygen-containing gas is introduced, the cathode is backed, for instance, with a porous polytetrafluoroethylene sheet, thereby permitting only the oxygen-containing gas to flow through the electrodes backing. If desired, the cathodes surface fronting on the electrolyte can be modified with an ion exchange resin membrane, such as, for instance, a copolymer of styrene sulfonic acid on polytetrafluoroethylene and a copolymer of acrylic acid on polyethylene.

Advantageously, the halogen conversion from brine solution requires a voltage range from about 1.1 to about 3.1 volts. This range is satisfactory to maintain an effective difference in potential across the cell. It is found that for best operations there should be established an external potential for each cell of between 2.4 volts and about 3.0

volts at a current density of milliamperes per square centimeter. The invention will be described in detail in conjunction with the following drawing which is to be taken as nonlimiting.

The sole drawing is an exploded view of one embodiment of a possible electrical cell, in cross section, which 'may be used in this invention. The halogen produced from permeates through an anode and a porous polytetrafluoroethylene separator 6 and comes in contact with ethylene which enters at port 7, reacting, and the product vinyl chloride is collected through an exit port 8. The brine solution is in contact with the positive electrode or anode 5, a negative electrode or cathode 9, and an ion exchange membrane 10'.

In general, the positive electrode 5 is prepared by molding a noble metal, graphitic carbon or a mixture of graphitic carbon and a noble metal with a water-proofing agent, such as polytetrafluoroethylene, into an electrode into which is embedded a tantalum metallic screen 11 directly linked to an external power source (not shown) through a suitable wire lead 12. The negative electrode 9 is prepared in a similar fashion as is the positive electrode 5 in which there is embedded a tantalum screen 13 connected to the same external power source (not shown) through a suitable wire lead 14.

Sealing gaskets

15 and 16 are provided so as to prevent any leakage of electrolyte. The cathode is backed by a porous polytetrafluoroethylene 17 so as to allow only gas but not liquid to permeate through it. There is also provided a polytrifluoromonochloroethylene chamber 18 having an inlet port 19 for introducing oxygen-containing gas. Any excess or unreacted oxygen-containing gas is permitted to exit through port 20. Spacer 21 is provided to prevent the buckling of the cathode and also for uniform distribution of the oxygen-containing gas at the cathode surface. The chamber 18 is backed by another inert gasket 22. There is also provided a polytrifluoromonochloroethylene chamber 23 having an outlet port 8 for exiting vinyl chloride. An inert, rigid, plastic screen spacer 24 is provided to prevent the buckling of the anode and also for uniform distribution of the chlorine gas at the anode surface. The chamber 23 is also backed by gasket 25. The entire assembly is held in place by end

stainless steel plates

26 and 27, secured by bolts and nuts (not shown). There are also provided

electrical heating pads

28 and 29 attached to

end plates

26 and 27. A thermocouple 30 and a thermistor 31 are positioned in the chamber 2 to maintain a constant temperature control.

In order to demonstrate the advantages of the process of the present invention, the following examples are presented.

EXAMPLE 1 A aqueous solution of sodium chloride is continuously circulated in the electrolytic chamber of the electrolysis cell. The two sides of the electrolytic chamber are positioned by two gas-pervious-liquid-impervious graphitic carbon electrodes containing about 5% polytetrafluoroethylene. Oxygen is allowed to fiow over the cathode surface not facing the electrolyte and ethylene is allowed to flow over the anode surface not facing the electrolyte. The area of each electrode exposed to the electrolyte is 20 cm. The surface of the cathode facing the electrolyte is covered with a low resistance Permion 1010 ion exchange membrane. The gases coming out from the anodic compartment are passed through a trap cooled to -40 C.

The solution is electrolyzed for 5 hours and 40 minutes, at 60 C., at a constant current of 1.0 amperes which is equivalent to a current density of 50 ma./cm. The solution obtained in the trap weighed 3.03 grams and analysis by vapor phase chromatography indicated that the solution contained vinyl chloride in good yield.

EXAMPLE 2 A aqueous solution of potassium chloride is continuously circulated in the electrolytic chamber of the same cell used in Example 1. Air is allowed to flow over the cathode surface not facing the electrolyte and isobutylene is allowed to flow over the anode surface not facing the electrolyte.

The electrolytic cell is operated in the same manner as Example 1. Analysis of the solution product shows the presence of 1-chloro-2-methylpropene-1.

EXAMPLE 3 A 20% aqueous solution of sodium chloride is continuously circulated in the electrolytic chamber of the same cell used in Example 1. Oxygen is allowed to fiow over the surface of the cathode in the same fashion as described in Example 1 and propylene is allowed to flow over the surface of the anode in the same fashion as described in Example 1.

The electrolytic cell is operated in the same manner as Example 1. Upon analysis, propylene chloride is found in the resultant solution in good yield.

Substituting 4-methylpentene-l for propylene and operating the cell in identical manner as Example 1, the resulting product l-chloro-4-methylpentene-l is found in good yield.

I claim:

1. An electrochemical process for production of monohalogenated alkenes which comprises: electrolyzing an aqueous metal halide solution in an electrolytic cell having a gas pervious, liquid impervious porous membrane anode through which is passed the halogen gas product of such electrolysis and reacting said halogen gas as it emerges from the outer surface of said porous anode with an alkene supplied to said outer surface and recovering monohalogenated alkene product from fluids removed from said outer surface of said anode.

2. The process according to claim 1 wherein the alkene is ethylene.

3. The process according to claim 1 wherein the alkene is propylene.

4. The process according to claim 1 wherein the aqueous solution of a metal halide to be electrolyzed is sodium chloride.

5. The process according to claim 1 wherein the aqueous solution of a metal halide to be electrolyzed is sodium bromide.

6. The process according to claim 1 in which the conversion of the aqueous metal halide solution to a halogen occurs at a temperature ranging from about 25 C. to about 100 C.

7. A process defined by claim 1 wherein said process is carried out in the defined cell which further comprises an oxygen-depolarized porous cathode.

8. The process according to claim 1 in which electrolysis is carried out with a potential established across the cell from about 1.1 volts to about 3.1 volts.

9. The process according to claim 1 wherein said electrodes are each backed with a porous, unsintered, polytetrafluoroethylene membrane.

References Cited UNITED STATES PATENTS 2,273,795 2/ 1942 Heise et al. 204-81 3,288,692 11/1966 Leduc 204 JOHN H. MACK, Primary Examiner R. L. ANDREWS, Assistant Examiner US. Cl. X.R. 204263 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,55 |53 Dated January 26, 1971 Inventor(s) JASPAL SINGH MAYELL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column L line 52, cancel "Claim 1" and substitute Claim 7 Column LL, line 55, cancel "Claim 1" and substitute Signed and sealed this 27th day of April 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents OHM P0-1050 (10-69)