Method for purification of a solvent for separation of styrene by extractive distillation and for separation of styrene

Patent metadata

Field	Value
Publication number	US-11465953-B2
Application number	US-201916961623-A
Country	US
Kind code	B2
Filing date	Jan 9, 2019
Priority date	Jan 12, 2018
Publication date	Oct 11, 2022
Grant date	Oct 11, 2022

Abstract

A method for purification of a styrene-containing feedstock includes steps of introducing the styrene-containing feedstock into the middle of an extractive distillation column, and a solvent for the extractive distillation into the upper part of the column; discharging a raffinate oil from the top of the column, and a rich solvent rich in styrene from the bottom of the column. The rich solvent is then introduced into the middle of the solvent recovery column for vacuum distillation to obtain a crude styrene from the top of the solvent recovery column, and a lean solvent is discharged from the bottom of the solvent recovery column and recycled to the upper part of the extractive distillation column. A portion of the rich solvent is sent to a solvent purification zone for a liquid-liquid extraction using water to obtain a mixture of a styrene polymer and styrene.

First claim

The invention claimed is:

1. A method for purification of a solvent for separation of styrene by extractive distillation, comprising:
(1) feeding a styrene-containing feedstock into a middle part of an extractive distillation column and a solvent for extractive distillation into an upper part of the extractive distillation column to carry out extractive distillation;
discharging a raffinate oil from a top of the extractive distillation column; and
discharging a rich solvent rich in styrene from the from a bottom of the extractive distillation column;
(2) feeding a first portion of the rich solvent into a solvent recovery column to carry out vacuum distillation;
discharging a crude styrene from a top of the solvent recovery column;
discharging a lean solvent from a bottom of the solvent recovery column;
and feeding the lean solvent to the upper part of the extractive distillation column; and
(3) feeding water and a second portion of the rich solvent into a solvent purification zone to carry out liquid-liquid extraction;
discharging a mixture of a styrene polymer and styrene from a top of the solvent purification zone; and
discharging a purified solvent containing water from a bottom of the solvent purification zone.

2. The method according to claim 1 , further comprising feeding a solvent purifying agent into the solvent purification zone, said solvent purifying agent comprising not less than 98% by mass of styrene and optional alkylaromatics.

3. The method according to claim 2 , wherein said solvent purifying agent is the crude styrene discharged from the top of the solvent recovery column or a topping styrene discharged from the top of a styrene refining column.

4. The method according to claim 1 , wherein the solvent purification zone is at a temperature of 20-65° C. and a pressure of 0.2-0.8 MPa.

5. The method according to claim 4 , wherein the temperature of the solvent purification zone is 30-60° C., and a number of equilibrium theoretical stage of the liquid-liquid extraction carried out in the solvent purification zone is 2-10.

6. The method according to claim 1 , wherein a mass ratio of the second portion of the rich solvent fed into the solvent purification zone to a total amount of the rich solvent is 0.5-20%.

7. The method according to claim 1 , wherein a mass ratio of the water fed into the solvent purification zone to the second portion of the rich solvent fed into the solvent purification zone is 0.2-2.0.

8. The method according to claim 2 , wherein a mass ratio of the solvent purifying agent fed into the solvent purification zone to the second portion of the rich solvent is 0.05-0.5, and a mass ratio of the water to the second portion of the rich solvent is 0.2-2.0.

9. The method according to claim 1 , further comprising:
feeding a mixture of the styrene polymer and the styrene discharged from the top of the solvent purification zone into a styrene refining system to obtain a refined styrene product, a topping styrene, and a polymer-rich tar.

10. The method according to claim 1 , further comprising regenerating a portion of the lean solvent discharged from the bottom of the solvent recovery column in a solvent regeneration column by steam stripping to obtain a regenerated solvent and a tar.

11. The method according to claim 10 , a mass ratio of the portion of the lean solvent to a total amount of the lean solvent is 0.5-10%.

12. The method according to claim 10 , wherein the solvent regeneration column has a reboiler that is a falling film evaporator placed outside the solvent regeneration column.

13. The method according to claim 1 , wherein the solvent for the extractive distillation is at least one selected from the group consisting of sulfolane, diethylene glycol, triethylene glycol, tetraethylene glycol, N,N-dimethylacetamide, and N-formylmorpholine.

14. The method according to claim 1 , wherein the styrene-containing feedstock is a styrene-containing C 8 fraction.

15. A method for separation of styrene by an extractive distillation, comprising:
(1) feeding a styrene-containing feedstock into a middle part of an extractive distillation column and a solvent for an extractive distillation into an upper part of the extractive distillation column to carry out extractive distillation;
discharging a raffinate oil from a top of the extractive distillation column; and
discharging a rich solvent rich in styrene from a bottom of the extractive distillation column;
(2) feeding a first portion of the rich solvent into a solvent recovery column to carry out vacuum distillation;
discharging a crude styrene from a top of the solvent recovery column; and, after drying and decolorizing treatment, feeding the dried and discolorized crude styrene into a styrene refining column; and
discharging a lean solvent from a bottom of the solvent recovery column;
(3) feeding a second portion of the rich solvent into a lower part of a solvent purification zone and water into an upper part of the solvent purification zone to carry out liquid-liquid extraction;
discharging a mixture of a styrene polymer and styrene from a top of the solvent purification zone; and
discharging a purified solvent containing water from a bottom of the solvent purification zone;
(4) drying and discolorizing a stream discharged from the top of the solvent purification zone and then feeding the dried and discolorized stream into the styrene refining column; and
(5) discharging a topping styrene from a top of the styrene refining column after distillation, a refined styrene product from an upper part of the styrene refining column, and a tar rich in polymer from a bottom of the styrene refining column.

16. The method according to claim 15 , feeding a solvent purifying agent into the solvent purification zone, wherein said solvent purifying agent is a crude styrene or the topping styrene discharged from the top of the styrene refining column.

17. The method according to claim 15 , wherein the solvent purification zone is at a temperature of 20-65° C., and a pressure of 0.2-0.8 MPa.

18. The method according to claim 15 , wherein a mass ratio of the second portion of the rich solvent fed into the solvent purification zone to a total amount of the rich solvent is 0.5-20%.

19. The method according to claim 15 , wherein a mass ratio of the water fed into the solvent purification zone to the second portion of the rich solvent is 0.2-2.0.

20. The method according to claim 16 , wherein a mass ratio of the solvent purifying agent fed into the solvent purification zone to the second portion of the rich solvent is 0.05-0.5, and a mass ratio of the water to the second portion of the rich solvent is 0.2-2.0.

21. The method according to claim 15 , further comprising:
feeding a portion of the lean solvent into a solvent regeneration column to carry out steam stripping distillation;
returning a vapor phase discharged from a top of the solvent regeneration column to a lower part of the solvent recovery column; and discharging a tar from a bottom of the solvent regeneration column,
wherein the solvent regeneration column is at a pressure of 10-30 kPa, and a temperature is 110-150° C., and has a mass ratio of the steam to the lean solvent of 3-8.

22. The method according to claim 21 , wherein a mass ratio of the lean solvent fed into the solvent regeneration column to a total amount of the lean solvent is 0.5-10%.

23. The method according to claim 21 , wherein the solvent regeneration

Assignees

• China Petroleum & Chem Corp
• Sinopec Res Inst Petroleum

Inventors

• Tang Wencheng
• Tian Longsheng
• Zhao Ming
• Gao Siliang
• Yang Nan
• Qie Siyuan
• Bian Zhifeng

Classifications

• B01D3/10

  Vacuum distillation (B01D3/12 takes precedence) · CPC title

• C07C7/08 Primary

  by extractive distillation · CPC title

• C07C7/10

  by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids · CPC title

• B01D3/40

  Extractive distillation · CPC title

• B01D3/148

  in combination with at least one evaporator · CPC title