Regeneration of caustic solutions

1. A caustic recovery system comprising:

an oxygen source that is fluidly coupled to an oxidizer tower and configured to provide oxygen to the oxidizer tower;

a caustic source configured to provide spent caustic and an oxidation catalyst source configured to provide an oxidation catalyst;

wherein the caustic source and the oxidation catalyst source are fluidly coupled to each other and the oxidizer tower via a mixing device, wherein the mixing device is configured to provide a mixture of spent caustic and oxidation catalyst to the oxidizer tower;

wherein the oxidizer tower is configured to allow introduction of the mixture an oxygen recycle stream, and the oxygen at a lower portion of the tower to thereby provide co-current contact of the spent caustic and catalyst with the oxygen and the recycle stream and to so produce regenerated caustic,

wherein the oxidizer tower further includes a recycling conduit that is configured to deliver the oxygen recycle stream from an upper vent opening of the oxidizer tower to a lower feed opening of the oxidizer tower, and

wherein the oxygen recycle stream is substantially free of waste gases.

2. The system of claim 1 wherein substantially all of any gasses vented from the oxidizer tower are fed back into the tower as the oxygen recycle stream.

3. The system of claim 2 further comprising a compressor or eductor that is configured to deliver the oxygen recycle stream to the tower.

4. The system of claim 3 wherein the oxygen source is configured to provide the oxygen to the tower as a gas stream comprising at least 88% O2.

5. A method of regenerating caustic comprising:

feeding into a lower portion of an oxidizer tower an oxygen recycle stream, an oxygen-containing stream, and a mixture of spent caustic and oxidation catalyst;

co-currently contacting the mixture of spent caustic and oxidation catalyst with the oxygen recycle stream and the oxygen-containing stream to so produce regenerated caustic;

withdrawing the regenerated caustic from the oxidizer tower; and

recycling an oxygen recycle stream from an upper vent opening of the oxidizer tower to a lower feed opening of the oxidizer tower, wherein the oxygen recycle stream is substantially free of waste gases.

6. The method of claim 5 wherein the oxygen-containing stream comprises at least 88% oxygen O2.

7. The method of claim 5 wherein natural gas is not intermingled with the spent caustic and oxygen-containing stream in the oxidizer tower.