Wet air oxidation process using recycled catalyst
View Patent ↗A system and method for the treatment of process streams. A catalyst mediates a wet oxidation process at elevated temperatures and pressures for treating at least one undesirable constituent in an aqueous mixture. The aqueous mixture may be contacted with a catalyst and an oxidizing agent at an elevated temperature and a superatmospheric pressure. At least a portion of the catalyst may be precipitated by a pH adjustment and recycled back to contact the aqueous mixture.
1. A catalytic wet oxidation process, comprising:
contacting an aqueous mixture containing at least one undesirable constituent to be treated with a copper catalyst and an oxidizing agent at an elevated temperature and superatmospheric pressure at a pH below about 2 or above about 13 at which the catalyst is substantially soluble to treat the at least one undesirable constituent within a wet oxidation reactor and form an oxidized aqueous mixture within the wet oxidation reactor;
precipitating at least a portion of the catalyst solely by adjusting a pH level of the oxidized aqueous mixture to form a precipitated catalyst; and
recycling at least a portion of the precipitated catalyst to contact the aqueous mixture.
2. The process according to claim 1 , wherein contacting the aqueous mixture with the catalyst occurs prior to bringing the aqueous mixture to the elevated temperature.
3. The process according to claim 1 , wherein contacting the aqueous mixture with the catalyst occurs prior bringing the aqueous mixture to the superatmospheric pressure.
4. The process according to claim 1 , further comprising monitoring the pH level of the aqueous mixture.
5. The process according to claim 1 , wherein the aqueous mixture is oxidized in a continuous process.
6. The process according to claim 5 , further comprising replenishing the catalyst.
7. The process according to claim 1 , wherein contacting the aqueous mixture with the oxidizing agent comprises contacting the aqueous mixture with an oxygen-containing gas.
8. The process according to claim 1 , wherein precipitating at least a portion of the catalyst comprises increasing the pH of at least a portion of the oxidized aqueous mixture.
9. The process according to claim 1 , wherein precipitating at least a portion of the catalyst comprises decreasing the pH of at least a portion of the oxidized aqueous mixture.
10. The process according to claim 1 , wherein the precipitated catalyst comprises copper oxide.
11. The process according to claim 1 , wherein adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to range of pH of from about 6 to about 12.
12. The process according to claim 11 , wherein adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to range of pH of from about 8 to about 9.
13. The process according to claim 1 , further comprising adjusting the pH of at least a portion of the precipitated catalyst.
14. The process according to claim 13 , wherein adjusting the pH of at least a portion of the precipitated catalyst comprises adjusting the pH to a level at which at least a portion of the precipitated catalyst solubilizes.
15. The process according to claim 1 , further comprising clarifying the oxidized aqueous mixture, thereby forming a first separated solution, prior to precipitating at least a portion of the catalyst from the oxidized aqueous mixture.
16. The process according to claim 15 , further comprising contacting the first separated solution with the aqueous mixture containing at least one undesirable constituent to be treated.
17. The process according to claim 1 , further comprising recovering substantially all of the catalyst.
18. The process according to claim 1 , wherein the aqueous mixture is oxidized for a period of time sufficient to treat the at least one undesirable constituent.
19. The process according to claim 1 , wherein the superatmospheric pressure is from about 30 atmospheres to about 275 atmospheres.
20. The process according to claim 1 , wherein the elevated temperature is from about 240° C. to about the critical temperature of water.
21. The process according to claim 1 , wherein the elevated temperature is above the critical temperature of water.
22. The process according to claim 1 , wherein precipitating the at least a portion of the catalyst is accomplished with a two step catalyst settling process comprising:
performing a rough clarification in a first clarifier to produce a first supernatant and a first separated solution including soluble catalyst;
contacting at least a portion of the first separated solution with the aqueous mixture;
settling at least a portion of the first supernatant in a second clarifier to produce solidified catalyst and an oxidized effluent essentially free of catalyst;
contacting the solidified catalyst from the second clarifier with the aqueous mixture; and
withdrawing the oxidized effluent essentially free of catalyst from the second clarifier.
23. The process according to claim 22 , further comprising adjusting a pH of the at least a portion of the first supernatant prior to settling the at least a portion of the first supernatant in the second clarifier.
24. The process according to claim 22 , further comprising adjusting a pH of the solidified catalyst from the second clarifier prior to contact with the aqueous solution.