Isoprene extraction with preserved C5 feedstock

Patent metadata

Field	Value
Publication number	US-10065907-B2
Application number	US-201515537442-A
Country	US
Kind code	B2
Filing date	Dec 15, 2015
Priority date	Dec 18, 2014
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

A process for extracting isoprene from a pyrolysis gas mixture or a C5 fraction wherein isoprene is purified by plural extractive distillations in the presence of a polar solvent and cyclopentadiene is effectively removed and recycled as a feedstock without being converted into its dimer, dicyclopentadiene. The isoprene recovered from the process described is more than 99.5% pure.

First claim

I claim:

1. A process of extracting isoprene from a mixture comprising C 5 hydrocarbons, comprising:
feeding the mixture comprising C 5 hydrocarbons into a first extractive distillation column and extractively distilling the mixture by contact with a first polar solvent to form a first overhead product comprising isoprene and a first slip stream comprising cyclopentadiene and substantially no dicyclopentadiene;
feeding the first overhead product to a second extractive distillation column and extractively distilling the first overhead product by contact with a second polar solvent to form a second overhead product comprising unextracted C 5 hydrocarbons and a second slip stream comprising isoprene and other hydrocarbons;
washing the second slip stream with water in a solvent wash column;
cooling the second overhead product in a cooler; and
distilling the second slip stream in a distillation column to form a third overhead product comprising high-purity isoprene, and a bottom product.

2. A process of extracting isoprene from a mixture comprising C 5 hydrocarbons, comprising:
feeding the mixture comprising C 5 hydrocarbons into a first extractive distillation column and extractively distilling the mixture by contact with a first polar solvent to form a first overhead product comprising isoprene and a first slip stream comprising cyclopentadiene and substantially no dicyclopentadiene;
feeding the first overhead product to a second extractive distillation column and extractively distilling the first overhead product by contact with a second polar solvent to form a second overhead product comprising unextracted C 5 hydrocarbons and a second slip stream comprising isoprene and other hydrocarbons;
removing solvent impurity in the second slip stream in a solvent wash column;
cooling the second slip stream; and
distilling the second slip stream in a distillation column to form a third overhead product comprising high-purity isoprene, and a bottom product.

3. The process of claim 1 , further comprising washing the first slip stream with water in a solvent wash column and cooling the first overhead product and separating the first slip stream into an oil fraction comprising cyclopentadiene and substantially no dicyclopentadiene and a water fraction comprising the polar solvent.

4. The process of claim 1 , further comprising treating a bottom solvent stream of the first extractive distillation column to remove dicyclopentadiene impurity by contacting the bottom solvent stream in a liquid-liquid extraction column, obtaining a purified bottom solvent product stream and a top product stream comprising hydrocarbons and dicyclopentadiene.

5. The process of claim 4 , further comprising washing the top product stream with water in a second liquid-liquid extraction column to remove solvent from the hydrocarbons and returning the solvent as a co-feed to the second extractive distillation column and sending the hydrocarbons to a cracker as a feed material.

6. The process of claim 1 , further comprising recycling the oil fraction comprising cyclopentadiene to a cracker to form one or more olefins.

7. The process of claim 1 , wherein the third overhead product has an isoprene purity of at least 99.5% by mass.

8. The process of claim 1 , wherein the first polar solvent and the second polar solvent are N-2-methylpyrrolidone.

9. A process of extracting isoprene from a Pygas mixture comprising C 5 to C 10 hydrocarbons, comprising:
distilling the Pygas mixture in a depentanizer distillation column to form a first overhead product comprising C 5 hydrocarbons and a first bottom product comprising C 6 to C 10 hydrocarbons;
feeding the first overhead product into a first extractive distillation column and extractively distilling the first overhead product by contact with a first polar solvent to form a second overhead product comprising isoprene, and a first slip stream comprising cyclopentadiene and substantially no dicyclopentadiene;
feeding the second overhead product to a second extractive distillation column and extractively distilling the second overhead product by contacting with a second polar solvent to form a third overhead product comprising unextracted C 5 hydrocarbons, and a second slip stream comprising isoprene and other hydrocarbons;
distilling the second slip stream;
washing the second slip stream in a solvent wash column;
cooling the second slip stream; and
feeding the second slip stream to a distillation column to form a fourth overhead product comprising high-purity isoprene, and a bottom product.

10. The process of claim 9 , further comprising cooling the first washed slip stream and separating the first washed slip stream into an oil fraction comprising cyclopentadiene and substantially no dicyclopentadiene and a water fraction comprising the polar solvent.

11. The process of claim 10 , further comprising recycling the oil fraction comprising cyclopentadiene to a cracker to form one or more olefins.

12. The process of claim 9 , wherein the fourth overhead product has an isoprene purity of at least 99.5% by mass.

13. The process of claim 1 , wherein the first polar solvent and the second polar solvent are N-2-methylpyrrolidone.

14. The process of claim 2 , further comprising washing the first slip stream with water in a solvent wash column and cooling the first overhead product and separating the first slip stream into an oil fraction comprising cyclopentadiene and substantially no dicyclopentadiene and a water fraction comprising the polar solvent.

15. The process of claim 2 , further comprising treating a bottom solvent stream of the first extractive distillation column to remove dicyclopentadiene impurity by contacting the bottom solvent stream in a liquid-liquid extraction column, obtaining a purified bottom solvent product stream and a top product stream comprising hydrocarbons and dicyclopentadiene.

16. The process of claim 15 , further comprising washing the top product stream with water in a second liquid-liquid extraction column to remove solvent from the hydrocarbons and returning the solvent as a co-feed to the second extractive distillation column and sending the hydrocarbons to a cracker as a feed material.

17. The process of claim 2 , further comprising recycling the oil fraction comprising cyclopentadiene to a cracker to form one or more olefins.

18. The process of claim 2 , wherein the third overhead product has an isoprene purity of at least 99.5% by mass.

19. The process of claim 2 , wherein the first polar solvent and the second polar solvent are N-2-methylpyrrolidone.

Assignees

• Sabic Global Technologies Bv

Inventors

• Abdelghani Mohamed Sabri

Classifications

• C07C7/10

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

• C10G45/60

  characterised by the catalyst used · CPC title

• C07C7/04

  by distillation · CPC title

• C10G2300/70

  Catalyst aspects · CPC title

• C10G70/042

  with the use of auxiliary compounds · CPC title