Processes and systems for recovery of styrene from a styrene-containing feedstock
In various embodiments, the present disclosure describes processes and systems for recovery of styrene from a styrene-rich feedstock. The processes and systems maintain performance of an extractive solvent used in the styrene recovery. In general, the processes include introducing a styrene-rich feedstock to an extractive distillation column, removing a styrene-rich stream from the extractive distillation column, introducing the styrene-rich stream to a solvent recovery column, removing a styrene-lean stream from the solvent recovery column, separating and treating a portion of the styrene-lean stream to form a treated extractive solvent and recycling the treated extractive solvent. In some embodiments, the treating process also includes steam stripping. Styrene-recovery systems including an extractive distillation column, a solvent recovery column, a solvent treatment apparatus having at least one equilibrium stage and a continuous circulation loop connecting these components are also disclosed herein.
1. A process for recovering styrene and maintaining performance of an extractive solvent in a system for recovery of styrene from a styrene-rich feedstock, said process comprising the steps of:
(a) introducing the styrene-rich feedstock to an extractive distillation column;
(b) removing a styrene-rich stream from the extractive distillation column;
wherein the styrene-rich stream comprises styrene and the extractive solvent;
(c) introducing the styrene-rich stream to a solvent recovery column;
(d) removing a styrene-lean stream from the solvent recovery column;
wherein an amount of styrene in the styrene-lean stream is less than an amount of styrene in the styrene-rich stream;
(e) separating a portion of the styrene-lean stream;
(f) treating the portion of the styrene-lean stream with an organic solvent to form a treated extractive solvent; and,
(g) recycling the treated extractive solvent.
2. The process of claim 1 , wherein the treating step further comprises washing the styrene-lean stream with water.
3. The process of claim 2 , wherein a ratio of the water to the extractive solvent is about 4 to about 0.2.
4. The process of claim 1 , wherein the extractive solvent comprises about 0 to about 40% of the styrene-lean stream.
5. The process of claim 1 , wherein the extractive solvent comprises about 0 to about 10% of the styrene-lean stream.
6. The process of claim 1 , wherein the treating step takes place in a liquid-liquid equilibrium system comprising at least one equilibrium stage.
7. The process of claim 6 , wherein there are up to seven equilibrium stages.
8. The process of claim 1 , wherein the organic solvent comprises at least one hydrocarbon.
9. The process of claim 1 , wherein the treating step comprises mixing the styrene-lean stream with the organic solvent and then mixing with water.
10. The process of claim 1 , further comprising:
adding at least one co-solvent to the extractive solvent.
11. The process of claim 10 , wherein the at least one co-solvent is selected from the group consisting of co-boiling aromatic compounds and glycol ethers.
12. A process for recovering styrene and maintaining performance of an extractive solvent in a system for recovery of styrene from a feedstock comprising styrene and ethylbenzene, said process comprising the steps of:
(a) introducing the feedstock to an extractive distillation column;
(b) removing a styrene-rich stream from the extractive distillation column;
wherein the styrene-rich stream comprises styrene and the extractive solvent;
(c) introducing the styrene-rich stream to a solvent recovery column;
(d) removing a styrene-lean stream from the solvent recovery column;
wherein an amount of styrene in the styrene-lean stream is less than an amount of styrene in the styrene-rich stream;
(e) separating a portion of the styrene-lean stream;
(f) treating the portion of the styrene-lean stream using steam stripping to produce steam-distilled extractive solvent and undistilled extractive solvent;
wherein undistilled extractive solvent is further treated with an organic solvent and water wash to form a treated extractive solvent; and
wherein the treated extractive solvent is recirculated to the styrene-lean stream for further steam stripping; and
(g) recycling the distilled extractive solvent.
13. The process of claim 12 , wherein the extractive solvent comprises about 0 to about 40% of the styrene-lean stream.
14. The process of claim 12 , wherein the steam stripping comprises using a steam stripping column to separate the extractive solvent from the styrene-lean stream.
15. The process of claim 12 , wherein the step of treating the undistilled extractive solvent with an organic solvent and water wash takes place in a liquid-liquid equilibrium system comprising at least one equilibrium stage.
16. The process of claim 12 , further comprising:
adding at least one co-solvent to the extractive solvent.
17. The process of claim 16 , wherein the at least one co-solvent is selected from the group consisting of co-boiling aromatic compounds and glycol ethers.