Electrolytic oxidation process

• US 4,032,416 A
• Filed: 03/10/1976
• Issued: 06/28/1977
• Est. Priority Date: 03/10/1976
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Cutler, Leonard Harry
• Primary Examiner(s): Andrews, R. L.
• Application Number:
  US05/665,550
• Time in Patent Office: 475 Days
• Field of Search: 204/72, 204/79, 204/292
• US Class Current: 205/431
• CPC Class Codes: C25B 3/29 Coupling reactions

Abstract

Dialkyldithiocarbamates are electrolytically oxidized to tetraalkylthiuram disulfides in a direct current electrolytic cell divided into a cathode compartment and an anode compartment separated from each other by a cationic membrane. The anode is stationary and has active surfaces of shiny platinum. Tetraalkylthiuram disulfides are obtained in high yield and in high degree of purity. The product tetraalkylthiuram disulfides are useful as vulcanization accelerators, fungicides, and seed treating agents.

Claims

1. A process for the electrolytic oxidation of a dialkyldithiocarbamate to a tetraalkylthiuram disulfide, said process comprising

(1) introducing a catholyte and an anolyte to an electrolytic cell divided into a cathode compartment and an anode compartment separated from each other by a cationic membrane capable of resisting migration of hydroxyl ions under process conditions, the active anode surfaces being shiny platinum;

the anolyte being an aqueous solution of an alkali metal dialkyldithiocarbamate, and the catholyte being a dilute aqueous alkali solution;

(2) connecting the anode and the cathode to a direct current source of a high enough voltage to provide a current density sufficient to effect oxidation of the dialkyldithiocarbamate to tetraalkylthiuram disulfide; and

(3) recovering the tetraalkylthiuram disulfide from the anode compartment.

2. The process of claim 1 wherein the catholyte is a solution of at most 17 weight percent sodium hydroxide;

the anolyte is a solution of a 20-40 weight percent sodium the anolyte temperature is at least about 60°

C.; and

the current density is at least about 0.2 amp/cm² .

3. The process of claim 2 wherein the anolyte is agitated.

4. The process of claim 3 wherein the dialkyldithiocarbamate is dimethyldithiocarbamate.

5. The process of claim 1 wherein the anode has, in addition to the active shiny platinum surfaces, also passive surfaces of titanium, tantalum, or columbium.

6. The process of claim 5 wherein the catholyte is a solution of at most 17 weight percent sodium hydroxide;

the anolyte is a solution of a 20-40 weight percent sodium dialkyldithiocarbamate;

the anolyte temperature is at least about 60°

C.;

the current density is at least about 0.2 amp/cm² ; and

the anolyte is agitated.

7. The process of claim 6 wherein the dialkyldithiocarbamate is dimethyldithiocarbamate.

8. The process of claim 1 wherein the dialkyldithiocarbamate salt is sodium salt, and it is present in a concentration of about 20-40 weight percent of the anolyte.

9. The process of claim 1 wherein the anode current density is at least 0.2 amp/cm², and the anolyte temperature is at least about 60°

C.

10. The process of claim 1 wherein the anolyte is agitated.

11. A process for the production of tetraalkylthiuram disulfides, wherein in the first stage a dialkylamine, carbon disulfide, and part of effluent sodium hydroxide from the cathode compartment of an electrolytic cell divided into a cathode compartment and an anode compartment by a cationic membrane capable of resisting migration of hydroxyl ions under the electrolysis conditions, the active surfaces of the anode being shiny platinum, are combined to form aqueous sodium dialkyldithiocarbamate in a reactor;

sodium dialkyldithiocarbamate solution about 20-40 weight percent is fed to the anode compartment of said electrolytic cell;

aqueous sodium hydroxide is introduced to the cathode compartment;

direct current is applied to the electrodes, the anode current density being at least about 0.2 amp/cm² ;

the solids in the effluent from the anode compartment, which contains the precipitated tetraalkylthiuram disulfide, are concentrated to give dialkyldithiocarbamate solution for recycle and a concentrated slurry of product tetraalkylthiuram disulfide;

the slurry is filtered and washed with water;

the filtrate and wash water are combined with the dialkyldithiocarbamate product from the reactor; and

effluent from the cathode compartment is degassed to give hydrogen and caustic, the caustic being recycled in part to the cathode compartment and in part to said reactor.

12. The process of claim 11 wherein the dialkyldithiocarbamate is dimethyldithiocarbamate.

13. The process of claim 11 wherein the anolyte temperature is at least about 60°

C. and the anolyte is agitated.

14. The process of claim 11 wherein the anode has, in addition to its active shiny platinum surfaces, also inactive surfaces of titanium, tantalum, or columbium.

15. The process of claim 11 where the concentration of sodium hydroxide in the cathode compartment is at most about 17 weight percent.