Circular economy for plastic waste to polyethylene via refinery FCC and alkylation units
Provided in one embodiment is a continuous process for converting waste plastic into recycle for polyethylene polymerization. The process comprises selecting waste plastics containing polyethylene and/or polypropylene, and 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 pyrolysis oil and optionally wax comprising a naphtha/diesel and heavy fraction, and char. The pyrolysis oil and wax is passed to a refinery FCC unit from which a liquid petroleum gas C 3 -C 5 olefin/paraffin mixture fraction is recovered. The liquid petroleum gas C 3 -C 5 olefin/paraffin mixture fraction is passed to a refinery alkylation unit, with a propane and butane fraction recovered from the alkylation unit. The propane and butane fraction is then passed to a steam cracker for ethylene production. In another embodiment, a naphtha fraction (C 5 -C 8 ) is recovered from the alkylation unit and passed to the steam cracker. In another embodiment, a propane/propylene fraction (C 3 -C 3 = ) is recovered from the FCC and passed to the steam cracker.
1. 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 polyolefin waste and produce a pyrolyzed effluent;
(c) separating the pyrolyzed effluent into offgas, char and a pyrolysis oil and optionally wax comprising a naphtha/diesel fraction and a heavy fraction;
(d) passing the pyrolysis oil and wax from (c) to a refinery FCC unit;
(e) recovering a liquid petroleum gas comprising C 3 -C 5 olefin/paraffin mixture fraction from the FCC unit;
(f) passing the liquid petroleum gas C 3 -C 5 olefin/paraffin mixture fraction to a refinery alkylation unit;
(g) recovering a propane fraction and a butane fraction from the alkylation unit; and
(h) passing the propane fraction, or butane fraction or combination of propane and butane fraction to a steam cracker for ethylene production.
2. The process of claim 1 , wherein a gasoline and heavy fraction are recovered from the refinery FCC unit.
3. The process of claim 2 , wherein the gasoline fraction recovered from the refinery FCC unit is combined with an alkylate gasoline fraction recovered from the alkylation unit.
4. The process of claim 1 , wherein an alkylate gasoline fraction is recovered from the refinery alkylation unit.
5. The process of claim 1 , wherein ethylene produced in (h) is subsequently polymerized.
6. The process of claim 5 , wherein polyethylene products are prepared from the polymerized ethylene.
7. The process of claim 1 , wherein the amount of gasoline produced by the FCC and alkylation units is increased with recycled pyrolysis oil and wax to the pyrolysis reactor.
8. The process of claim 1 , wherein at least some contaminants are removed from the recovered pyrolysis oil of step (c) before the oil is passed to the FCC unit in (d).
9. The process of claim 1 , wherein the waste plastics selected in (a) are from plastics classification group 2, 4, and/or 5.
10. The process of claim 1 , wherein the volume flow of pyrolysis oil and wax to the refinery FCC unit comprises up to about 50 volume % of the total hydrocarbon feed to the FCC unit.
11. The process of claim 10 , wherein the volume flow of pyrolysis flow to the refinery FCC unit is up to about 20 volume % of the total feed to the FCC unit.
12. 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 polyolefin waste and produce a pyrolyzed effluent;
(c) separating the pyrolyzed effluent into offgas, char and a pyrolysis oil and optionally wax comprising a naphtha/diesel fraction and a heavy fraction;
(d) passing the pyrolysis oil and wax from (c) to a refinery FCC unit;
(e) recovering a liquid petroleum gas comprising C 3 -C 5 olefin/paraffin mixture fraction from the FCC unit;
(f) passing the liquid petroleum gas comprising C 3 -C 5 olefin/paraffin mixture fraction to a refinery alkylation unit;
(g) recovering a naphtha fraction from the alkylation unit; and
(h) passing the naphtha fraction to a steam cracker for ethylene production.
13. The process of claim 12 , wherein a gasoline and heavy fraction are recovered from the refinery FCC unit.
14. The process of claim 12 , wherein an alkylate gasoline fraction is recovered from the refinery alkylation unit.
15. The process of claim 13 , wherein the gasoline fraction recovered from the refinery FCC unit is combined with an alkylate gasoline fraction recovered from the alkylation unit.
16. The process of claim 15 , wherein the amount of gasoline produced by the FCC and Alkylation units is increased with recycled pyrolysis oil to the pyrolysis reactor.
17. The process of claim 12 , wherein at least some contaminants are removed from the recovered pyrolysis oil of step (c) before the oil is passed to the FCC unit in (d).
18. The process of claim 12 , wherein the waste plastics selected in (a) are from plastics classification group 2, 4, and/or 5.
19. The process of claim 12 , wherein ethylene produced in (h) is subsequently polymerized.
20. The process of claim 19 , wherein polyethylene products are prepared from the polymerized ethylene.
21. The process of claim 12 , wherein the volume flow of pyrolysis oil and wax to the refinery FCC unit comprises up to about 50 volume % of the total hydrocarbon feed to the FCC unit.
22. The process of claim 21 , wherein the volume flow of pyrolysis flow to the refinery FCC unit is up to about 20 volume % of the total feed to the FCC unit.