Process for converting waste plastic into lubricating oils

• US 6,822,126 B2
• Filed: 04/18/2002
• Issued: 11/23/2004
• Est. Priority Date: 04/18/2002
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Miller, Stephen J.
• Primary Examiner(s): Dang, Thuan D.
• Application Number:
  US10/126,831
• Publication Number:
  US 20030199718A1
• Time in Patent Office: 950 Days
• Field of Search: 208/18, 208/27, 208/950, 585/241
• US Class Current: 585/241
• CPC Class Codes: C10G 1/00 Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal mechanical winning of oil from oil-shales, oil-sand, or the like B03B
• CPC Class Codes: C10G 1/002 in combination with oil conversion- or refining processes
• CPC Class Codes: C10G 1/10 from rubber or rubber waste
• CPC Class Codes: C10G 45/64 containing crystalline alumino-silicates, e.g. molecular sieves
• CPC Class Codes: C10G 65/043 at least one step being a change in the structural skeleton
• CPC Class Codes: Y10S 208/95 Processing of "fischer-tropsch" crude

Abstract

Provided is a continuous process for converting waste or virgin plastics into lube oils. The plastic feed is maintained in a heater at preferred temperatures of 150° C.-350° C. The feed is continuously passed to a pyrolysis reactor preferably maintained at a temperature of 450° C.-700° C. and at atmospheric pressure. Relatively short residence times are employed. Optionally, the reactor effluent is processed in a hydrotreating unit. The effluent is fed to an isomerization dewaxing unit and fractionated to recover lube oil stocks. Preferably, the feed to the pyrolysis reactor can be a blend of waste plastic and waxy Fischer-Tropsch fractions.

Claims

1. A continuous process for converting waste plastic into lube oil stock comprising:

(a) passing a waste and/or virgin polyolefin into a heating unit blanketed with an inert gas and maintained at a temperature between 150°

C. and 350°

C. to provide a molten feed;

(b) continuously passing the molten feed through a flow-through pyrolysis reactor maintained at a temperature sufficient to depolymerize at least a portion of the polyolefin and at an absolute pressure of at least one bar to produce a pyrolyzed effluent;

(c) passing at least a portion of the effluent from the pyrolysis reactor to a catalytic isomerization dewaxing unit;

(d) fractionating the product from the isomerization dewaxing unit; and

(e) recovering a lubricating oil base stock.

2. A process according to claim 1, wherein the lubricating oil base stock comprises a neutral oil and/or a bright stock.

3. A process according to claim 1, wherein the polyolefin is a polyethylene, a polypropylene or an EPDM elastomer.

4. A process according to claim 3, wherein the polyolefin is a high density or low density polyethylene.

5. A process according to claim 1, further comprising passing at least a portion of the pyrolyzed effluent of step (b) to a hydrotreating unit to remove a significant portion of any nitrogen-containing, sulfur-containing and/or oxygenated contaminants;

and passing at least a portion of the effluent from the hydrotreating unit to the catalytic isomerization dewaxing unit of step (c).

6. A process according to claim 1, wherein the catalyst in the isomerization dewaxing unit contains an intermediate pore size molecular sieve SAPO.

7. A process according to claim 1, wherein the molten feed comprises 5-95 wt % of the polyolefin.

8. A process according to claim 7, wherein the molten feed comprises 95-5 wt % of a Fischer-Tropsch wax.

9. A process according to claim 1, wherein the feed rate in the pyrolysis reactor ranges from about 0.5 to about 5.0 hr⁻

1 LHSV.

10. A process according to claim 1, wherein the temperature in the pyrolysis reactor is in the range of about 450°

C. to about 700°

C.

16. A process according to claim 1, wherein the effluent of the pyrolysis reactor is separated into at least a light fraction, a middle fraction and a heavy fraction.

17. A process according to claim 16, wherein at least a portion of the heavy fraction is circulated back to the pyrolysis reactor.

18. A process according to claim 16, wherein at least a portion of the light fraction is circulated to a oligomerization reactor.

19. A process according to claim 16, wherein at least a portion of the middle fraction is circulated to a hydrotreating unit and a catalytic isomerization dewaxing unit.

11. A continuous process for converting waste or virgin plastic into lube oil stock comprising the steps of:

(a) passing solid waste and/or virgin polyethylene or a liquid containing said polyethylene into a heating unit maintained at a temperature of about 200°

C. to about 350°

C. and under a blanket of an inert gas to provide a heated feed;

(b) continuously passing the heated feed through a pyrolysis flow-through reactor maintained at a temperature of about 500°

C. to about 650°

C., a pressure of about 1 bar, and a residence time up to about 1 hour to produce a pyrolyzed effluent;

(c) passing the effluent from the pyrolysis reactor to a separator and recovering at least a heavy fraction;

(d) passing at least a portion of the said heavy fraction to a catalytic isomerization dewaxing unit;

(e) passing the product from the isomerization dewaxing unit to a distillation unit; and

, recovering a lube oil stock.

12. A process of claim 11, wherein the polyethylene contains a high molecular weight fraction which is removed prior to forwarding to the heating unit.

13. A process of claim 11, wherein the catalyst in the isomerization dewaxing unit comprises a molecular sieve SAPO.

14. A process of claim 11, wherein said heated polyethylene feed contains a heavy Fischer-Tropsch wax.

15. A process of claim 11 further comprising passing at least a portion of the heavy fraction of step (c) to a hydrotreating unit and passing the product from the hydrotreating unit to the catalytic isomerization dewaxing unit of step (d).