PROCESS FOR DESULFURIZATION OF CRACKED NAPHTHA

• US 20090188837A1
• Filed: 01/29/2008
• Published: 07/30/2009
• Est. Priority Date: 01/29/2008
• Status: Active Grant

• Current Assignee: Catalytic Distillation Technologies (Lummus Technology LLC)
• Original Assignee: Catalytic Distillation Technologies (Lummus Technology LLC)
• Inventors: Podrebarac, Gary G.
• Granted Patent: US 7,927,480 B2
• Time in Patent Office: Days
• US Class Current: 208/210
• CPC Class Codes: C10G 2300/4087 Catalytic distillation
• CPC Class Codes: C10G 2400/02 Gasoline
• CPC Class Codes: C10G 45/02 to eliminate hetero atoms without changing the skeleton of the hydrocarbon involved and without cracking into lower boiling hydrocarbons; Hydrofinishing

Abstract

A process for the desulfurization of a fluid catalytically cracked naphtha wherein the valuable olefins are retained and recombinant mercaptans are prevented from forming, resulting in a low sulfur naphtha. Embodiments disclosed herein may allow for more flexibility in varying the end point of the naphtha used in gasoline blending

Claims

1. A process for reducing the sulfur content of a hydrocarbon stream, the process comprising:

feeding a pre-fractionated naphtha stream comprising organic sulfur compounds to a first catalytic distillation reactor system having one or more reaction zones comprising a hydrodesulfurization catalyst;

feeding hydrogen to the first catalytic distillation reactor system;

concurrently in the first catalytic distillation reactor system;

fractionating the pre-fractionated naphtha stream into a heavy naphtha fraction and an intermediate naphtha fraction;

contacting hydrogen and the intermediate naphtha fraction in at least one of the reaction zones to form hydrogen sulfide and an intermediate naphtha fraction of reduced organic sulfur content;

contacting hydrogen and the heavy naphtha fraction in at least one of the reaction zones to form hydrogen sulfide and a heavy naphtha fraction of reduced organic sulfur content;

recovering the intermediate naphtha fraction, hydrogen sulfide, and any unreacted hydrogen as a first overheads fraction;

recovering the heavy naphtha fraction and dissolved hydrogen sulfide as a first bottoms fraction;

stripping the hydrogen sulfide from the first overheads fraction;

feeding the stripped first overheads fraction to a second catalytic distillation reactor system having one or more reaction zones comprising a hydrodesulfurization catalyst;

feeding hydrogen to the second catalytic distillation reactor system;

concurrently in the second catalytic distillation reactor system;

fractionating the stripped first overheads fraction stream into a light intermediate naphtha fraction and a heavy intermediate naphtha fraction;

contacting hydrogen and the light intermediate naphtha fraction in at least one of the reaction zones to form hydrogen sulfide and a light intermediate naphtha fraction of reduced organic sulfur content;

contacting hydrogen and the heavy intermediate naphtha fraction in at least one of the reaction zones to form hydrogen sulfide and a heavy intermediate naphtha fraction of reduced organic sulfur content;

recovering the light intermediate naphtha fraction, hydrogen sulfide, and any unreacted hydrogen as a second overheads fraction;

recovering the heavy intermediate naphtha fraction as a second bottoms fraction;

recycling at least a portion of the second bottoms fraction to the first catalytic distillation reactor system;

stripping the hydrogen sulfide from the first bottoms fraction to recover a heavy naphtha fraction of reduced sulfur content;

stripping the hydrogen sulfide from the second overheads fraction to recover a light intermediate naphtha fraction of reduced sulfur content.

2. The process of claim 1, further comprising recycling at least a portion of the second bottoms fraction to the second catalytic distillation reactor system.

3. The process of claim 1, further comprising:

partially condensing the first overheads fraction; and

recycling at least a portion of the partially condensed first overheads fraction to the first distillation column reactor system as reflux.

4. The process of claim 3, wherein the partially condensing the first overheads fraction comprises cooling the first overheads fraction and separating the resulting vapor and liquid in at least one of a hot drum and a cold drum.

5. The process of claim 1, further comprising:

partially condensing the second overheads fraction; and

recycling at least a portion of the partially condensed second overheads fraction to the second distillation column reactor system as reflux.

6. The process of claim 5, wherein the partially condensing the second overheads fraction comprises cooling the second overheads fraction and separating the resulting vapor and liquid in at least one of a hot drum and a cold drum.

7. The process of claim 1, further comprising:

feeding a full range naphtha stream comprising organic sulfur compounds, including mercaptans, and highly unsaturated compounds, including dienes, to a third catalytic distillation reactor system having one or more reaction zones comprising a catalyst comprising a Group VIII metal;

feeding hydrogen to the third catalytic distillation reactor system;

concurrently in the third catalytic distillation reactor system;

fractionating the full range naphtha stream into a light naphtha fraction and an intermediate-heavy naphtha fraction;

contacting mercaptans and the dienes in at least one of the reaction zones to form sulfides and a light naphtha fraction of reduced mereaptan content;

recovering the light naphtha fraction having a reduced mercaptan content and any unreacted hydrogen as a third overheads fraction;

recovering an intermediate-heavy naphtha fraction including the sulfides as a third bottoms fraction; and

feeding at least a portion of the third bottoms to the first catalytic distillation reactor system as the pre-fractionated naphtha feed.

8. The process of claim 1, further comprising:

fractionating a full range naphtha stream into a light naphtha fraction and an intermediate-heavy naphtha fraction;

feeding at least a portion of the intermediate-heavy naphtha fraction to the first catalytic distillation reactor system as the pre-fractionated naphtha feed.

9. The process of claim 8, further comprising removing at least a portion of the mercaptans in the light naphtha fraction using a caustic wash process.

10. The process of claim 1, further comprising:

feeding hydrogen and the full range naphtha to a fixed bed hydrodesulfurization reactor having one or more reaction zones comprising a hydrodesulfurization catalyst to produce an effluent comprising hydrogen sulfide and a full range naphtha of reduced sulfur content;

fractionating the effluent into a light naphtha fraction and an intermediate-heavy naphtha fraction;

feeding at least a portion of the intermediate-heavy naphtha fraction to the first catalytic distillation reactor system as the pre-fractionated naphtha feed.

11. The process of claim 1, wherein the light intermediate naphtha fraction has an end point of about 320°

F. or less.

12. The process of claim 1, wherein the light intermediate naphtha fraction has an end point of about 280°

F. or less.

13. The process of claim 1, wherein the pre-fractionated naphtha has a boiling range from about C6 to about 480°

F. or greater.

14. The process of claim 1, wherein the pre-fractionated naphtha has a boiling range from about 140°

F. to about 480°

F. or greater.

15. The process of claim 1, wherein the stripped first overheads fraction fed to the second catalytic distillation reactor system contains less than 200 ppm hydrogen sulfide.

16. The process of claim 1, wherein the light intermediate naphtha fraction of reduced sulfur content contains less than 10 ppm sulfur.