Process for degrading organic substances in an aqueous composition

• US 20100294727A1
• Filed: 01/29/2009
• Published: 11/25/2010
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: Solvay SA (Solvac SA)
• Original Assignee: Solvay SA (Solvac SA)
• Inventors: Blancke, Ward, Gilbeau, Patrick
• Granted Patent: US 8,795,536 B2
• Time in Patent Office: Days
• US Class Current: 210/748.13
• CPC Class Codes: C01D 3/14 Purification
• CPC Class Codes: C02F 1/048 Purification of waste water by evaporation
• CPC Class Codes: C02F 1/22 by freezing
• CPC Class Codes: C02F 1/30 by irradiation
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 1/722 Oxidation by peroxides
• CPC Class Codes: C02F 1/76 with halogens or compounds of halogens C02F1/4674 takes precedence
• CPC Class Codes: C02F 2101/10 Inorganic compounds
• CPC Class Codes: C02F 2101/30 Organic compounds
• CPC Class Codes: C02F 2103/36 from the manufacture of organic compounds
• CPC Class Codes: C02F 2201/46115 Electrolytic cell with membranes or diaphragms
• CPC Class Codes: C02F 2209/02 Temperature
• CPC Class Codes: C02F 2209/03 Pressure
• CPC Class Codes: C02F 2209/06 pH

Abstract

Process for degrading organic substances in an aqueous composition comprising a step (a) wherein, in a liquid reaction medium, said aqueous composition is reacted with at least one composition comprising hydroxide ions (OH⁻) and hypochlorite in a molar ratio between hydroxide and hypochlorite higher than or equal to 0.001 and lower than 1.5, in order to oxidize said organic substances.

Claims

1. A process for degrading organic substances in an aqueous composition comprising a step (a) wherein, in a liquid reaction medium, said aqueous composition is reacted with at least one composition comprising hydroxide ions (OH⁻

) and hypochlorite in a molar ratio between hydroxide and hypochlorite higher than or equal to 0.001 and lower than 1.5, in order to oxidize said organic substances.

2. The process according to claim 1 wherein the aqueous composition containing the organic substances contains at least one salt, comprising a further step (b1), wherein at least part of the reaction medium of step (a) is subjected to an operation selected from the group consisting of cooling, evaporative crystallization, and any combination thereof, in order to precipitate at least part of the salt, followed by a step wherein at least part of the precipitated salt and at least part of the water present in the aqueous composition are recovered.

3. The process according to claim 1 wherein step (a) is carried out at a first pH value and comprising a further step (b2), wherein, at least part of the reaction medium of step (a) is subjected to an acidification operation in order to bring the pH at a second value lower than the first pH value of step (a) and the organic substances are further oxidized.

4. The process according to claim 3, wherein at least one compound selected from the group consisting of chlorine, hypochlorite, chlorate, chlorine dioxide, dichlorine monoxide, and any mixture thereof, is added to the reaction medium of step (b2).

5. The process according to claim 4, wherein the compound is chlorine and the partial pressure of chlorine during step (b2) is higher than or equal to 0.001 bar and lower than or equal to 10 bar.

6. The process according to claim 3, wherein during or after step (b2), a treatment with UV-visible light is carried out on the reaction medium.

7. The process according to claim 6, wherein the UV-visible light has a wavelength higher than or equal to 100 nm and lower than or equal to 400 nm, wherein the UV-visible light is emitted by a source and wherein the ratio between the electrical energy consumed by the source in Wh and the volume of the treated part of the reaction medium of step (a) in liter is higher than or equal to 1 Wh/l and lower than or equal to 100 Wh/l.

8. The process according to claim 3, wherein during or after step (b2), a treatment by electrolysis is carried out on the reaction medium.

9. The process according to claim 8, wherein the treatment by electrolysis is carried out in an anodic compartment of a divided electrolysis cell, wherein the anodic current density is higher than or equal to 1 A/m2 of anode and lower than or equal to 25000 A/m² of anode and wherein the ratio between the surface of the anode and the volume of the part of the treated reaction medium from step (a) is higher than or equal to 0.001 cm⁻

1 and lower than or equal to 1 cm<sup>−

1</sup>.

10. The process according to claim 3, wherein step (b1) is carried out on the reaction medium obtained at the end of step (b2).

11. The process according to claim 2 wherein at least one of the steps (a), (b1) and (b2) is carried out in a continuous mode.

12. The process according to claim 1 wherein the reaction of step (a) is carried out in at least one of the following conditions:

i. a pH controlled and maintained in a range which lowest limit is higher than or equal to 6 and which highest limit is lower than or equal to 11,

ii. a temperature higher than or equal to 10°

C. and lower than or equal to 200°

C.,

iii. a pressure higher than or equal to 1 bar (absolute) and lower than or equal to 11 bar,

iv. when step (a) of the process is carried out in a discontinuous mode, a duration higher than or equal to 0.05 h and lower than or equal to 8 h,

v. when step (a) of the process is carried out in a continuous mode, a residence time higher than or equal to 0.05 h and lower than or equal to 8 h.

13. The process according to claim 1 wherein step (a) is carried out in a continuous mode, and wherein the reaction of step (a) is carried out in at least two consecutive reaction zones, at least one of which is operated under mixed regime and at least one other of which is operated under plug flow regime.

14. The process according to claim 3 wherein the reaction of step (b2) is carried out in at least one of the following conditions:

i. a pH controlled and maintained in a range which lowest limit is higher than or equal to 0.01 and which highest limit is lower than 6,

ii. a temperature higher than or equal to 10°

C. and lower than or equal to 200°

C.,

iii. a pressure higher than or equal to 1 bar (absolute) and lower than or equal to 11 bar,

iv. when step (b2) of the process is carried out in a discontinuous mode, a duration higher than or equal to 0.05 h and lower than or equal to 8 h,

v. when step (b2) of the process is carried out in a continuous mode, a residence time higher than or equal to 0.05 h and lower than or equal to 8 h.

15. The process according to claim 1 wherein the aqueous composition containing the organic substances to be treated originates from a process for manufacturing an epoxide, or from a process for manufacturing a chlorinated organic compound, or from both processes.