Conversion of propylene to ethylene

Patent metadata

Field	Value
Publication number	US-11136278-B2
Application number	US-202017100698-A
Country	US
Kind code	B2
Filing date	Nov 20, 2020
Priority date	Nov 20, 2019
Publication date	Oct 5, 2021
Grant date	Oct 5, 2021

Abstract

Processes and systems for the conversion of propylene to ethylene may include introducing a propylene feed stream to a C3 metathesis reactor, converting the propylene to ethylene and 2-butene. The metathesis reactor effluent may be recovered and separated in a fractionation system to recover an ethylene product, a C3 fraction, a C4 fraction, and a C5+ fraction. All or a portion of the C3 fraction may be fed to the C3 metathesis reactor to produce additional ethylene. The C4 fraction may be converted in a C4 isomerization/metathesis reaction zone by: (i) isomerization of 2-butenes to 1-butene, (ii) metathesis of the 1-butene and 2-butene to produce propylene and 2-pentene, and/or (iii) autometathesis of the 1-butene to produce ethylene and 3-hexene. An effluent from the C4 isomerization/metathesis reaction zone may then be recovered and fed from the C4 isomerization/metathesis reaction zone to the fractionation system.

First claim

What is claimed:

1. A process for the conversion of propylene to ethylene, comprising:
introducing a propylene feed stream to a C3 metathesis reactor;
contacting the propylene with a metathesis catalyst in the C3 metathesis reactor to convert the propylene to ethylene and 2-butene and recovering an effluent from the C3 metathesis reactor;
separating the effluent in a fractionation system to recover an ethylene product fraction, a C3 fraction, a C4 fraction, and a C5+ fraction;
feeding all or a portion of the C3 fraction to the C3 metathesis reactor to produce additional ethylene;
feeding the C4 fraction to a C4 isomerization/metathesis reaction zone;
converting the C4 fraction in the C4 isomerization/metathesis reaction zone by: (i) isomerization of a portion of the 2-butenes to 1-butene, (ii) metathesis of the 1-butene and 2-butene to produce propylene and 2-pentene, and/or (iii) autometathesis of the 1-butene to produce ethylene and 3-hexene;
recovering an effluent from the C4 isomerization/metathesis reaction zone, the effluent comprising ethylene, propylene, butenes, pentenes, and hexenes; and
feeding the effluent from the C4 isomerization/metathesis reaction zone to the fractionation system.

2. The process of claim 1 , further comprising feeding at least a portion of the C5+ fraction to the C3 metathesis reactor.

3. The process of claim 2 , wherein the effluent from the C3 metathesis reactor comprise C7+ olefins, the process further comprising purging a portion of the C5+ fraction.

4. The process of claim 2 , further comprising isomerizing 2-pentene and 3-hexene in the C3 metathesis reaction zone to produce 1-pentene and 1-hexene.

5. The process of claim 1 , further comprising withdrawing a portion of the C3 fraction as a C3 product fraction.

6. The process of claim 1 , further comprising feeding a mixed C4 fraction comprising n-butenes to the C4 isomerization/metathesis reaction zone.

7. The process of claim 1 , wherein the C4 isomerization/metathesis reaction zone comprises an isomerization reactor for isomerizing the 2-butene to 1-butene, a C4 superfractionator for separating a 1-butene fraction from a 2-butene fraction, and a metathesis reactor for converting the 1-butene via autometathesis to ethylene and 3-hexene and for converting 1-butene and 2-butene via metathesis to propylene and 2-pentene.

8. The process of claim 7 , further comprising feeding at least a portion of the 2-butene fraction recovered in the C4 fractionator to the isomerization reactor.

9. The process of claim 1 , further comprising:
feeding hydrogen and a mixed C5 stream to a decyclopentenizer to selectively hydrogenate any cyclopentadiene in the mixed C5 stream and to recover an overheads fraction comprising n-C5 olefins and i-C5 olefins, including 2-pentene, 1-pentene, 3-methyl 1-butene, and 2-methyl-2-butene, and a bottoms stream and/or side draw comprising cyclopentenes;
feeding ethylene and the overheads fraction to a C5 isomerization/metathesis reaction zone for:
isomerizing the 1-pentene to 2-pentene;
isomerizing the 3-methyl-1-butene to 2-methyl-2-butene;
metathesizing the 2-pentene with ethylene to produce 1-butene and propylene; and
metathesizing the 2-methyl-2-butene with ethylene to produce isobutene and propylene;

recovering the metathesis products and unreacted feed components as an effluent from the C5 isomerization/metathesis reaction zone;
fractionating the effluent to recover an ethylene fraction, a propylene fraction, a C4 fraction, and a C5 fraction;
feeding the C5 fraction to the C5 isomerization/metathesis reaction zone.

10. A system for the conversion of propylene to ethylene, comprising:
a flow line for providing propylene from a feed source;
a C3 metathesis reactor for contacting the propylene with a metathesis catalyst to convert the propylene to ethylene and 2-butene and recovering an effluent from the C3 metathesis reactor;
a fractionation system for separating the effluent to recover an ethylene product fraction, a C3 fraction, a C4 fraction, and a C5+ fraction;
a flow line for feeding all or a portion of the C3 fraction to the C3 metathesis reactor;
a flow line for feeding the C4 fraction to a C4 isomerization/metathesis reaction zone;
the C4 isomerization/metathesis reaction zone, for converting the C4 fraction by: (i) isomerization of a portion of the 2-butenes to 1-butene, (ii) metathesis of the 1-butene and 2-butene to produce propylene and 2-pentene, and/or (iii) autometathesis of the 1-butene to produce ethylene and 3-hexene;
a flow line for feeding an effluent from the C4 isomerization/metathesis reaction zone to the fractionation system, the effluent comprising ethylene, propylene, butenes, pentenes, and hexenes.

11. The system of claim 10 , further comprising a flow line for feeding at least a portion of the C5+ fraction to the C3 metathesis reactor.

12. The system of claim 11 , further comprising a flow line for purging a portion of the C5+ fraction.

13. The system of claim 10 , further comprising a flow line for withdrawing a portion of the C3 fraction as a C3 product fraction.

14. The system of claim 10 , further comprising a flow line for feeding a mixed C4 fraction comprising n-butenes to the C4 isomerization/metathesis reaction zone.

15. The system of claim 10 , wherein the C4 isomerization/metathesis reaction zone comprises an isomerization reactor for isomerizing the 2-butene to 1-butene, a C4 superfractionator for separating a 1-butene fraction from a 2-butene fraction, and a metathesis reactor for converting the 1-butene via autometathesis to ethylene and 3-hexene and for converting 1-butene and 2-butene via metathesis to propylene and 2-pentene.

16. The system of claim 15 , further comprising a flow line for feeding at least a portion of the 2-butene fraction recovered in the C4 fractionator to the isomerization reactor.

17. The system of claim 10 , further comprising:
a flow line for providing hydrogen and a flow line for providing a mixed C5 stream;
a decyclopentenizer to selectively hydrogenate any cyclopentene and/or cyclopentadiene in the mixed C5 stream and to recover a C5 overheads fraction comprising n-C5 olefins and i-C5 olefins, including 2-pentene, 1-pentene, 3-methyl 1-butene, and 2-methyl-2-butene, and a bottoms stream and/or side draw comprising n-pentanes, i-pentanes, cyclopentene and/or cyclopentane;
a C5 isomerization/metathesis reaction zone receiving an ethylene feed and the C5 overheads fraction, the C5 isomerization/metathesis reaction zone being configure for:
isomerizing the 1-pentene to 2-pentene;
isomerizing the 3-methyl-1-butene to 2-methyl-2-butene;
metathesizing the 2-pentene with ethylene to produce 1-butene and propylene; and
metathesizing the 2-methyl-2-butene with ethylene to produce isobutene and propylene;

a flow line for recovering an effluent from the C5 isomerization/metathesis reaction zone;
a separation system for fractionating the effluent from the C5 isomerization/metathesis reaction zone to recover an ethylene fraction, a propylene fraction, a C4 fraction, and a C5 fraction;
a flow line for feeding the C5 fraction to the C5 isomerization/metathesis reaction zone.

18. The system of claim 17 , wherein the ethylene fed to the C5 isomerization/metathesis reaction zone comprises (i) a fresh ethylene feed, (ii) the ethylene fraction, and/or (iii) a portion of the ethylene product fraction.

19. The system of claim 18 , further comprising a flow line for feeding the propylene fraction to the C3 metathesis reaction zone.

Assignees

• Lummus Technology Inc

Inventors

• Choi Sukwon

Classifications

• C07C11/02

  Alkenes · CPC title

• C07C5/2512 Primary

  with metal oxides · CPC title

• C07C4/06 Primary

  Catalytic processes {(C07C4/025 takes precedence)} · CPC title

• C07C2523/30

  Tungsten · CPC title

• C07C2521/06

  Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof · CPC title