Circular economy for plastic waste to polyethylene and chemicals via refinery crude unit

Patent metadata

Field	Value
Publication number	US-11518943-B2
Application number	US-202017131839-A
Country	US
Kind code	B2
Filing date	Dec 23, 2020
Priority date	Dec 23, 2019
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

Provided is a continuous process for converting waste plastic into recycle for polyethylene polymerization or for normal alpha olefins. The process comprises selecting waste plastics containing polyethylene and/or polypropylene and then passing the waste plastics through a pyrolysis reactor to thermally crack at least a portion of the polyolefin waste and produce a pyrolyzed effluent. The pyrolyzed effluent is separated into offgas, a naphtha/diesel fraction, a heavy fraction, and char. The naphtha/diesel fraction is passed to a crude unit in a refinery from which is recovered a straight run naphtha fraction (C 5 -C 8 ) or a propane/butane (C 3 -C 4 ) fraction. The straight run naphtha fraction, or propane and butane (C 3 -C 4 ) fraction, is passed to a steam cracker for ethylene production. The ethylene is converted to normal alpha olefin and/or polyethylene. Also, a heavy fraction from the pyrolysis reactor can be combined with a heavy fraction of normal alpha olefin stream recovered from the steam cracker. The combined heavy fraction and heavy fraction of normal alpha olefin stream can be passed to a wax hydrogenation zone to produce wax.

First claim

What is claimed is:

1. A continuous process for converting waste plastic into recycle for normal alpha olefins comprising:
(a) selecting waste plastics containing polyethylene and/or polypropylene;
(b) passing the waste plastics from (a) through a pyrolysis reactor to thermally crack at least a portion of the waste plastics and produce a pyrolyzed effluent;
(c) separating the pyrolyzed effluent into offgas, a naphtha/diesel fraction, a heavy fraction, and char;
(d) passing the naphtha/diesel fraction to a crude unit in a refinery;
(e) recovering a straight run naphtha fraction (C 5 -C 8 ) from the crude unit;
(f) passing the straight run naphtha fraction to a steam cracker for ethylene production; and
(g) passing ethylene to a normal alpha olefin synthesis unit to produce normal alpha olefins.

2. The process of claim 1 , wherein the naphtha/diesel fraction of (c) is passed directly to a refinery crude unit and contaminants are removed in a crude unit desalter.

3. The process of claim 1 , wherein contaminants are removed at the pyrolysis reactor.

4. The process of claim 1 , wherein volume flow of naphtha/diesel fraction to the crude unit in the refinery comprises up to 50 volume % of total hydrocarbon flow to the crude unit.

5. The process of claim 4 , wherein the naphtha/diesel flow comprises up to 20 volume %.

6. The process of claim 4 , wherein the waste plastics selected in (a) are from plastics classification group 2, 4 and/or 5.

7. A continuous process for converting waste plastic into recycle for polyethylene polymerization comprising:
(a) selecting waste plastics containing polyethylene and/or polypropylene;
(b) passing the waste plastics from (a) through a pyrolysis reactor to thermally crack at least a portion of the waste plastics and produce a pyrolyzed effluent;
(c) separating the pyrolyzed effluent into offgas, a naphtha/diesel fraction, a heavy fraction, and char;
(d) passing the naphtha/diesel fraction to a crude unit in a refinery;
(e) recovering a straight run naphtha fraction (C 5 -C 8 ) from the crude unit;
(f) passing the straight run naphtha fraction to a steam cracker for ethylene production;
(g) passing ethylene to a normal alpha olefins synthesis unit to produce normal alpha olefins, and recovering a heavy fraction (C 22+ ) normal alpha olefin stream;
(h) combining the heavy fraction from (c) with the heavy fraction (C 22+ ) normal alpha olefin stream from (g); and
(i) passing the combined heavy fraction and heavy fraction of normal alpha olefin stream from (g) to a wax hydrogenation zone to produce wax.

8. The process of claim 7 , wherein the naphtha/diesel fraction of (c) is passed directly to a refinery crude unit and contaminants are removed in a crude unit desalter.

9. The process of claim 7 , wherein contaminants are removed at the pyrolysis reactor.

10. The process of claim 7 , wherein the heavy fraction of normal alpha olefin stream in (g) is taken from normal alpha olefins produced using ethylene produced in the steam cracker.

11. The process of claim 7 , wherein ethylene produced in (f) is subsequently polymerized.

12. The process of claim 11 , wherein polyethylene products are prepared from the polymerized ethylene.

13. The process of claim 7 , wherein heavy naphtha/diesel is recovered from the crude unit and further processed in the refinery to clean gasoline, diesel, or jet fuel.

14. The process of claim 7 , wherein atmospheric gas oil is recovered from the crude unit and further processed in the refinery to clean gasoline, diesel, or jet fuel.

15. The process of claim 7 , wherein virgin crude oil is passed to the crude unit and the amount of virgin crude oil processed by the crude unit is reduced due to the naphtha/diesel fraction passed to the crude unit.

16. The process of claim 7 , wherein volume flow of naphtha/diesel fraction to the crude unit in the refinery comprises up to 50 volume % of total hydrocarbon flow to the crude unit.

17. The process of claim 16 , wherein the naphtha/diesel flow comprises up to 20 volume %.

18. A continuous process for converting waste plastic into recycle for polyethylene polymerization comprising:
(a) selecting waste plastics containing polyethylene and/or polypropylene;
(b) passing the waste plastics from (a) through a pyrolysis reactor to thermally crack at least a portion of the waste plastics and produce a pyrolyzed effluent;
(c) separating the pyrolyzed effluent into offgas, a naphtha/diesel fraction, a heavy fraction, and char;
(d) passing the naphtha/diesel fraction to a crude unit in a refinery;
(e) recovering a portion of a propane and butane (C 3 -C 4 ) fraction from the crude unit;
(f) passing the recovered C 3 -C 4 fraction from (e) to a steam cracker for ethylene production;
(g) combining the heavy fraction from (c) with a heavy fraction (C 22+ ) of normal alpha olefin stream; and
(h) passing the combined heavy fraction and heavy fraction (C 22+ ) of normal alpha olefin stream from (g) to a wax hydrogenation zone to produce wax.

19. The process of claim 18 , wherein the naphtha/diesel fraction of (c) is passed directly to a refinery crude unit and contaminants are removed in a crude unit desalter.

20. The process of claim 18 , wherein contaminants are removed at the pyrolysis site.

21. The process of claim 18 , wherein the heavy fraction of normal alpha olefin stream in (g) is synthesized from ethylene produced in the steam cracker.

22. The process of claim 18 , wherein ethylene produced in (f) is subsequently polymerized.

23. The process of claim 22 , wherein polyethylene products are prepared from the polymerized ethylene.

24. The process of claim 18 , wherein heavy naphtha/diesel is recovered from the crude unit and further processed in the refinery to clean gasoline, diesel, or jet fuel.

25. The process of claim 18 , wherein the waste plastics selected in (a) are from plastics classification group 2, 4 and/or 5.

26. A process for converting waste plastic into chemicals useful in preparing polyethylene and wax comprising:
(a) selecting waste plastics containing polyethylene and/or polypropylene;
(b) pyrolyzing the waste plastics and recovering a naphtha/diesel fraction and a heavy fraction;
(c) passing the naphtha/diesel fraction to a crude unit in a refinery; and
(d) passing the heavy fraction in (b) to a wax hydrogenation zone.

Assignees

• Chevron Usa Inc

Inventors

• Timken Hye-Kyung

Classifications

• C10G9/36

  with heated gases or vapours · CPC title

• C10G50/00

  Production of liquid hydrocarbon mixtures from lower carbon number hydrocarbons, e.g. by oligomerisation · CPC title

• C10G2400/08

  Jet fuel · CPC title

• C10G1/002 Primary

  in combination with oil conversion- or refining processes · CPC title

• C10B53/07

  {of solid raw materials consisting} of synthetic polymeric materials, e.g. tyres (recovery or working-up of waste materials of organic macromolecular compounds or compositions based thereon by dry-heat treatment for obtaining partially depolymerised materials C08J11/10; production of liquid hydrocarbon mixtures from rubber or rubber waste C10G1/10) · CPC title