Method for producing polysulfides by means of electrolytic oxidation

• US 6,517,699 B2
• Filed: 08/27/2001
• Issued: 02/11/2003
• Est. Priority Date: 02/26/1999
• Status: Expired due to Term

• Current Assignee: Asahi Glass Company, Limited (AGC, Inc.), Kawasaki Kasei Chemicals Ltd. (Air Water Incorporated), Nippon Paper Industries Company Limited (Nippon Paper Group Incorporated)
• Original Assignee: Asahi Glass Company, Limited (AGC, Inc.), Kawasaki Kasei Chemicals Ltd. (Air Water Incorporated), Nippon Paper Industries Company Limited (Nippon Paper Group Incorporated)
• Inventors: Watanabe, Keigo, Andoh, Tatsuya, Shimohira, Tetsuji, Tanaka, Junji, Nanri, Yasunori
• Primary Examiner(s): Wong, Edna
• Application Number:
  US09/938,579
• Publication Number:
  US 20020053520A1
• Time in Patent Office: 533 Days
• Field of Search: 205/414, 205/444, 205/554, 205/494, 205/746, 205/758, 205/759, 205/770
• US Class Current: 205/414
• CPC Class Codes: C25B 1/00 Electrolytic production of inorganic compounds or non-metals
• CPC Class Codes: C25B 11/031 Porous electrodes
• CPC Class Codes: C25B 11/075 consisting of a single catalytic element or catalytic compound
• CPC Class Codes: C25B 11/089 Alloys
• CPC Class Codes: C25B 15/025 of electrolyte parameters
• CPC Class Codes: C25B 9/13 Single electrolytic cells with circulation of an electrolyte
• CPC Class Codes: C25B 9/19 with diaphragms
• CPC Class Codes: D21C 11/0057 Oxidation of liquors, e.g. in order to reduce the losses of sulfur compounds, followed by evaporation or combustion if the liquor in question is a black liquor deodorisation of gases D21C11/08; combustion D21C11/12, D21C11/14
• CPC Class Codes: D21C 11/0078 Treatment of green or white liquors with other means or other compounds than gases, e.g. in order to separate solid compounds such as sodium chloride and carbonate from these liquors; Further treatment of these compounds fractionating of spent liquors D21C11/0042

Abstract

The present invention has an object to obtain a cooking liquor containing polysulfide-sulfur at a high concentration by minimizing by-production of thiosulfate ions. The present invention is a method for producing polysulfides, which comprises introducing a solution containing sulfide ions into an anode compartment of an electrolytic cell comprising the anode compartment provided with a porous anode, a cathode compartment provided with a cathode, and a diaphragm partitioning the anode compartment and the cathode compartment, for electrolytic oxidation to obtain polysulfide ions, characterized in that the porous anode is disposed so that a space is provided at least partly between the porous anode and the diaphragm, and the apparent volume of the porous anode is from 60% to 99% based on the volume of the anode compartment.

Claims

1. A method for producing polysulfides, which comprises:

in an electrolytic cell having an anode compartment provided with a porous anode, a cathode compartment provided with a cathode, and a diaphragm which partitions the anode compartment and the cathode compartment, wherein the porous anode is positioned in the anode compartment so as to provide a space at least partly between the porous anode and the diaphragm such that the apparent volume of the porous anode ranges from 60% to 90% based on the volume of the anode compartment,

introducing a solution containing sulfide ions into the anode compartment; and

conducting electrolysis in the electrolytic cell so as to form polysulfide ions in the solution of the anode compartment.

2. The method for producing polysulfides according to claim 1, wherein the porous anode has a physically continuous three dimensional network structure.

3. The method for producing polysulfides according to claim 2, wherein the porous anode is such that at least its surface is made of nickel or a nickel alloy containing nickel in an amount of at least 50 wt %.

4. The method for producing polysulfides according to claim 3, wherein the surface area of the porous anode is from 2 to 100 m^2/m2 per effective current-carrying area of the diaphragm.

5. The method for producing polysulfides according to claim 4, wherein the electrolysis is carried out under a condition such that the pressure in the anode compartment is higher than the pressure in the cathode compartment.

6. The method for producing polysulfides according to claim 3, wherein the electrolysis is carried out under a condition such that the pressure in the anode compartment is higher than the pressure in the cathode compartment.

7. The method for producing polysulfides according to claim 2, wherein a diameter of a portion corresponding to a thread of a net constituting the network is from 0.01 to 2 mm.

8. The method for producing polysulfides according to claim 7, wherein the diameter is from 0.02 to 1 mm.

9. The method for producing polysulfides according to claim 2, wherein an average pore diameter of the network of the anode is from 0.001 to 5 mm.

10. The method for producing polysulfides according to claim 9, wherein the average pore diameter is from 0.2 to 2 mm.

11. The method for producing polysulfides according to claim 1, wherein the surface area of the porous anode is from 2 to 100 m²/m² per effective current-carrying area of the diaphragm.

12. The method for producing polysulfides according to claim 11, wherein the electrolysis is carried out under a condition such that the pressure in the anode compartment is higher than the pressure in the cathode compartment.

13. The method for producing polysulfides according to claim 1, wherein the electrolysis is carried out under a condition such that the pressure in the anode compartment is higher than the pressure in the cathode compartment.

14. The method for producing polysulfides according to claim 1, wherein the current density in the electrolysis is from 0.5 to 20 kA/m² per effective current-carrying area.

15. The method for producing polysulfides according to claim 1, wherein the solution containing sulfide ions, is made to pass through the anode compartment at an average superficial velocity of from 1 to 30 cm/sec.

16. The method for producing polysulfides according to claim 1, wherein the solution containing sulfide ions is white liquor or green liquor in a pulp production process.

17. The method for producing polysulfides according to claim 16, further comprising withdrawing liquid from the anode compartment containing polysulfide product as an electrolytically oxidized white liquor or green liquor which is then supplied to a next step of processing without recycling the liquid to the anode compartment.

18. The method for producing polysulfides according to claim 1, wherein the apparent volume of the porous anode is from 70 to 99%.

19. The method for producing polysulfides according to claim 1, wherein said anode has a surface area per volume of the anode compartment of from 500 to 20,000 m²/m³.

20. The method for producing polysulfides according to claim 1, wherein said porous anode has a porosity of from 30 to 99%.

21. The method for producing polysulfides according to claim 20, wherein said porosity is from 50 to 98%.

22. The method for producing polysulfides according to claim 1, wherein said cathode comprises a material having alkali resistance.

23. The method for producing polysulfides according to claim 22, wherein said cathode comprises nickel, Raney nickel, nickel sulfide, steel or stainless steel.

24. The method for producing polysulfides according to claim 1, wherein the diaphragm partitioning the anode compartment and the cathode compartment is a cation exchange membrane.

25. The method for producing polysulfides according to claim 1, wherein said porous anode comprises carbon fibers, carbon felts, carbon papers, metal foams, meshed metals or meshed carbon.

26. The method for producing polysulfides according to claim 1, wherein said porous anode comprises a metal electrode having platinum applied to a surface thereof.