Fluid catalytic cracking to produce and recover light olefins

• US 8,066,868 B1
• Filed: 12/20/2006
• Issued: 11/29/2011
• Est. Priority Date: 12/20/2006
• Status: Active Grant

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Zimmermann, Joseph E.
• Primary Examiner(s): Caldarola; Glenn
• Assistant Examiner(s): Boyer; Randy
• Application Number:
  US11/642,455
• Time in Patent Office: 1,805 Days
• Field of Search: 208/46, 208/95, 208100-104, 208/106, 208113-124
• US Class Current: 208/113
• CPC Class Codes: C10G 21/00 Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents C10G17/00, C10G19/00 take precedence
• CPC Class Codes: C10G 55/06 including at least one catalytic cracking step
• CPC Class Codes: Y02P 30/40 Ethylene production

Abstract

Processing schemes and arrangements are provided for the processing a heavy hydrocarbon feedstock via fluidized catalytic cracking with selected hydrocarbon fractions including light olefins being obtained via absorption and separation product recovery.

Claims

1. A process for catalytic cracking a heavy hydrocarbon feedstock and recovering select hydrocarbons including light olefins, the process comprising:

contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidized reactor zone at effective conditions to produce light olefins to form a fluid catalytic cracker effluent stream comprising a range of hydrocarbons;

separating the fluid catalytic cracker effluent stream in a separation system to form a first separation system stream comprising primarily C₄−

hydrocarbons and at least a second separation system stream comprising primarily C₅+ hydrocarbons;

cooling at least a portion of the first separation system stream;

then compressing at least a portion of the first separation system stream;

then contacting at least a portion of the first separation system stream in an absorption system with an absorption solvent at effective conditions to absorb a significant portion of C₂+ hydrocarbons from the first separation process stream to form a first absorption system stream comprising primarily methane and hydrogen and to form a second absorption system stream comprising a portion of the absorption solvent and C₂+ hydrocarbons, wherein the effective conditions to absorb a significant portion of C₂+ hydrocarbons in the absorption system comprise a temperature of about 4°

C. to about 27°

C. (about 40°

F. to about 80°

F.);

separating at least a portion of the second absorption system stream to form at least a first process stream comprising at least a portion of the absorption solvent and at least one second process stream comprising a remaining portion of the second absorption system stream; and

returning at least a portion of the first process stream to the absorption system as the absorption solvent.

2. The process of claim 1 wherein the contacting of the heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst comprises contacting the heavy hydrocarbon feedstock with a blended catalyst comprising regenerated catalyst and coked catalyst in a fluidized reactor zone at hydrocarbon cracking reaction conditions to produce a fluid catalytic cracker effluent stream containing hydrocarbon products including light olefins, the catalyst having a catalyst composition including a first component comprising a large pore molecular sieve and a second component comprising a zeolite with no greater than medium pore size, the zeolite with no greater than medium pore size comprising at least 1.0 wt. % of the catalyst composition.

3. The process of claim 1 wherein the step of separating at least a portion of the second absorption system stream comprises forming a first separated process stream comprising primarily C₂ hydrocarbons and the process further comprises separating at least a portion of the first separated process stream in a C₂ separation unit to form a first C₂ separation unit stream comprising primarily ethylene and a second C₂ separation unit stream comprising primarily ethane.

4. The process of claim 1 wherein the step of separating at least a portion of the second absorption system stream comprises forming a second separated process stream comprising primarily C₃ hydrocarbons and the process further comprises separating at least a portion of the second separated process stream in a C₃ separation unit to form a first C₃ separation unit stream comprising primarily propylene and a second C₃ separation unit stream comprising primarily propane.

5. The process of claim 1 wherein the step of separating at least a portion of the second absorption system stream comprises forming a third separated process stream comprising primarily gasoline.

6. The process of claim 1 wherein the absorption solvent comprises primarily C₄ hydrocarbons.

7. The process of claim 1 wherein the effective conditions to absorb a significant portion of C₂+ hydrocarbons in the absorption system comprise a pressure of at least about 1,379 kPag (about 200 psig).

8. The process of claim 1 wherein the step of contacting at least a portion of the first separation system stream in an absorption system comprises:

contacting at least a portion of the first separation system stream in a primary absorption unit with a primary absorption solvent at effective conditions to absorb a significant portion of C₂+ hydrocarbons to form a first primary absorption unit stream comprising primarily methane and hydrogen and to form a second primary absorption unit stream comprising at least a portion of the primary absorption solvent, C₂+ hydrocarbons, a quantity of light olefins and a reduced quantity of hydrogen and methane;

contacting at least a portion of the first primary absorption unit stream in a secondary absorption unit with a secondary absorption solvent comprising a liquid portion of the first separation system stream at effective conditions to absorb light olefins to form a first secondary absorption unit stream comprising primarily methane and hydrogen and a second secondary absorption unit stream comprising a quantity of C₂+ hydrocarbons including light olefins;

stripping at least a quantity of methane and hydrogen from at least a portion of the second primary absorption unit stream in a stripper unit at effective conditions to form a first stripper unit stream comprising a quantity of hydrogen and methane and a second stripper unit stream comprising at least a portion of the primary absorption solvent and C₂+ hydrocarbons including light olefins; and

returning at least a portion of the first stripper unit stream to the primary absorption unit.

9. The process of claim 8 further comprising stripping a liquid portion of the first separation system stream in the stripping unit.

10. The process of claim 1 wherein the second absorption system stream includes a quantity of at least one impurity selected from the group consisting of hydrogen sulfide, mercaptan, sulfur, water, carbon dioxide, and acetylene, the process further comprising treating at least a portion of the second absorption system stream in a treatment system to remove at least a portion of the impurity.

11. A process for catalytic cracking a heavy hydrocarbon feedstock and recovering select hydrocarbons including light olefins, the process comprising:

contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidized reactor zone at effective conditions to produce light olefins to form a fluid catalytic cracker effluent stream comprising a range of hydrocarbons wherein the hydrocarbon cracking catalyst comprises contacting the heavy hydrocarbon feedstock with a catalyst in a fluidized reactor zone at hydrocarbon cracking reaction conditions to produce a cracked stream containing hydrocarbon products including light olefins, the catalyst having a catalyst composition including a first component comprising a large pore molecular sieve and a second component comprising a zeolite with no greater than medium pore size, the zeolite with no greater than medium pore size comprising at least 1.0 wt. % of the catalyst composition;

separating the fluid catalytic cracker effluent stream in a separation system to form a first separation system stream comprising primarily C₄−

hydrocarbons and at least a second separation system stream comprising primarily C₅+ hydrocarbons;

contacting at least a portion of the first separation system stream in an absorption system with an absorption solvent at effective conditions to absorb a significant portion of C₂+ hydrocarbons from the first separation system stream to form a first absorption system stream comprising primarily methane and hydrogen, and to form a second absorption system stream comprising at least a portion of the absorption solvent, C₂+ hydrocarbons and a quantity of at least one impurity selected from the group consisting of hydrogen sulfide, mercaptan, sulfur, water, carbon dioxide, and acetylene;

treating at least a portion of the second absorption system stream in a treatment system to remove at least a portion of the impurity;

separating at least a portion of the treated second absorption system stream to form a first process stream comprising at least a portion of the absorption solvent, a first separated process stream comprising primarily C₂ hydrocarbons, a second separated process stream comprising primarily C₃ hydrocarbons, and a residual separated process stream comprising a remaining portion of the second absorption system stream;

returning at least a portion of the first process stream to the absorption system as the absorption solvent;

separating the first separated process stream in a C₂ separation unit to form a first C₂ separation unit stream comprising primarily ethylene and a second C₂ separation unit stream comprising primarily ethane; and

separating the second separated process stream in a C₃ separation unit to form a first C₃ separation unit stream comprising primarily propylene and a second C₃ separation unit stream comprising primarily propane.

12. The process of claim 11 wherein the absorption solvent comprises primarily C₄ hydrocarbons.

13. The process of claim 11 wherein the effective conditions to absorb a significant portion of C₂+ hydrocarbons in the absorption system comprise a pressure of at least about 1,379 kPag (about 200 psig) and a temperature of about 4°

C. to about 27°

C. (about 40°

F. to about 80°

F.).

14. The process of claim 11 wherein the step of contacting at least a portion of the first separation system stream in an absorption system comprises:

contacting at least a portion of the first separation system stream in a primary absorption unit with a primary absorption solvent at effective conditions to absorb a significant portion of C₂+ hydrocarbons to form a first primary absorption unit stream comprising primarily methane, hydrogen, and a quantity of light olefins and to form a second primary absorption unit stream comprising at least a portion of the primary absorption solvent and C₂+ hydrocarbons and a reduced quantity of methane and hydrogen;

contacting at least a portion of the first primary absorption unit stream in a secondary absorption unit with a secondary absorption solvent comprising a liquid portion of the first separation system stream at effective conditions to absorb light olefins to form a first secondary absorption unit stream comprising primarily methane and hydrogen and a second secondary absorption unit stream comprising a quantity C₂+ hydrocarbons including light olefins;

stripping at least a quantity of methane and hydrogen from at least a portion of the second primary absorption unit stream in a stripping unit at effective conditions to form a first stripper unit stream comprising a quantity of hydrogen and methane and a second stripper unit stream comprising at least a portion of the primary absorption solvent and C₂+ hydrocarbons including light olefins; and

returning at least a portion of the first stripper unit stream to the primary absorption unit.

15. The process of claim 11 wherein prior to the step of contacting at least a portion of first separation system stream in an absorption system, the process further comprises:

cooling at least a portion of the first separation system stream to a temperature of about 4°

C. to about 27°

C. (about 40°

F. to about 80°

F.); and

compressing at least a portion of the first separation system stream to a pressure of at least about 1,379 kPag (about 200 psig).

16. The process of claim 11 wherein the catalyst comprises a blended catalyst comprising regenerated catalyst and coked catalyst.

17. A process for catalytic cracking a heavy hydrocarbon feedstock and recovering select hydrocarbons including light olefins, the process comprising:

contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidized reactor zone at effective conditions to produce light olefins to form a fluid catalytic cracker effluent stream comprising a range of hydrocarbons;

separating the fluid catalytic cracker effluent stream in a separation system to form a first separation system stream comprising primarily C₄−

hydrocarbons and at least a second separation system stream comprising primarily C₅+ hydrocarbons;

contacting at least a portion of the first separation system stream in a primary absorption unit with a primary absorption solvent at effective conditions to absorb a significant portion of C₂+ hydrocarbons to form a first primary absorption unit stream comprising primarily methane and hydrogen and to form a second primary absorption unit stream comprising at least a portion of the primary absorption solvent, C₂+ hydrocarbons, a quantity of light olefins and a reduced quantity of hydrogen and methane;

contacting at least a portion of the first primary absorption unit stream in a secondary absorption unit with a secondary absorption solvent comprising a liquid portion of the first separation system stream at effective conditions to absorb light olefins to form a first secondary absorption unit stream comprising primarily methane and hydrogen and a second secondary absorption unit stream comprising a quantity of C₂+ hydrocarbons including light olefins;

stripping at least a quantity of methane and hydrogen from at least a portion of the second primary absorption unit stream in a stripper unit at effective conditions to form a first stripper unit stream comprising a quantity of hydrogen and methane and a second stripper unit stream comprising at least a portion of the primary absorption solvent and C₂+ hydrocarbons including light olefins; and

returning at least a portion of the first stripper unit stream to the primary absorption unit;

separating at least a portion of the second stripper unit stream to form at least a first process stream comprising at least a portion of the primary absorption solvent and at least one second process stream comprising a remaining portion of the second absorption system stream; and

returning at least a portion of the first process stream to the absorption system as the primary absorption solvent.

18. The process of claim 17 wherein prior to the step of contacting at least a portion of the first separation system stream in an absorption system, the process further comprises:

cooling at least a portion of the first separation system stream to a temperature of about 4°

C. to about 27°

C. (about 40°

F. to about 80°

F.); and

then compressing at least a portion of the first separation system stream to a pressure of at least about 1,379 kPag (about 200 psig).

19. The process of claim 17 wherein the second stripper unit stream includes a quantity of at least one impurity selected from the group consisting of hydrogen sulfide, mercaptan, sulfur, water, carbon dioxide, and acetylene, the process further comprising treating at least a portion of the second absorption system stream in a treatment system to remove at least a portion of the impurity.

20. The process of claim 17 wherein the step of separating at least a portion of the second stripper unit stream comprises forming a second separated process stream comprising primarily C₃ hydrocarbons and the process further comprises separating at least a portion of the second separated process stream in a C₃ separation unit to form a first C₃ separation unit stream comprising primarily propylene and a second C₃ separation unit stream comprising primarily propane.