REGENERATION OF ALKALI METAL REAGENT

• US 20110147274A1
• Filed: 12/14/2010
• Published: 06/23/2011
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Original Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Inventors: Oldenburg, Paul D., Baird, William C. JR., Soto, Jorge L., McConnachie, Jonathan M., Bearden, Roby JR., Leta, Daniel P., Brown, Leo D., Greaney, Mark A., Vann, Walter D., Han, Lu, Bielenberg, James R.
• Granted Patent: US 8,404,106 B2
• Time in Patent Office: Days
• US Class Current: 208/230
• CPC Class Codes: B01D 2251/404 of calcium
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 53/1468 Removing hydrogen sulfide
• CPC Class Codes: B01D 53/501 by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• CPC Class Codes: B01D 53/52 Hydrogen sulfide
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants
• CPC Class Codes: C01B 17/22 Alkali metal sulfides or polysulfides
• CPC Class Codes: C01B 17/32 Hydrosulfides of sodium or potassium
• CPC Class Codes: C01D 1/22 with carbonates or bicarbonates
• CPC Class Codes: C01F 11/06 of carbonates
• CPC Class Codes: C01F 11/18 Carbonates
• CPC Class Codes: C10G 19/02 with aqueous alkaline solutions
• CPC Class Codes: C10G 19/08 Recovery of used refining agents
• CPC Class Codes: C10G 29/16 Metal oxides
• CPC Class Codes: C10G 32/02 by electric or magnetic means
• 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

After desulfurizing a hydrocarbon feedstream using an alkali metal reagent, the hydrocarbon feedstream can include particles of spent alkali metal salts. The spent alkali metal salts can be separated from the hydrocarbon feedstream and regenerated to form an alkali metal reagent, such as a alkali hydroxide or alkali sulfide. The regeneration process can pass through an intermediate stage of forming an alkali carbonate by successive reactions with carbon dioxide and calcium oxide. The calcium oxide can also be regenerated.

Claims

1. A method for regenerating an alkali metal salt reagent, comprising:

a) receiving a hydrocarbon feedstream having an API gravity of at least about 20, the hydrocarbon feedstream including at least about 7.5 wt % of alkali metal salt particles, the alkali metal salt particles comprising alkali metal hydrogen sulfide particles;

b) washing the hydrocarbon feedstream with water to form a hydrocarbon product stream and an aqueous alkali metal salt stream containing alkali metal salt;

c) treating at least a portion of the aqueous alkali metal salt stream with carbon dioxide under effective conditions to form an aqueous alkali carbonate stream;

d) mixing the aqueous alkali carbonate stream with regenerated calcium oxide under effective conditions to form an aqueous alkali metal hydroxide and calcium carbonate solids;

e) separating the calcium carbonate from the aqueous alkali metal hydroxide; and

f) heating the calcium carbonate under effective conditions to form regenerated calcium oxide, wherein at least a portion of the regenerated calcium oxide is used for said mixing with aqueous alkali carbonate.

2. The method of claim 1, wherein the alkali metal salt particles further comprise at least one of alkali metal hydroxide or alkali metal sulfide particles.

3. The method of claim 1, further comprising:

removing water from the aqueous alkali metal hydroxide to provide a concentrated aqueous alkali metal hydroxide stream having a concentration of at least about 30 wt %; and

contacting the concentrated aqueous alkali metal hydroxide stream with a hydrocarbon feedstream under effective conditions to at least partially desulfurize the hydrocarbon feedstream.

4. The method of claim 1, wherein the aqueous alkali carbonate stream includes aqueous bicarbonate, the method further comprising heating the aqueous alkali carbonate stream to convert aqueous bicarbonates to aqueous carbonates prior to the mixing with the regenerated calcium oxide.

5. The method of claim 1, wherein the alkali metal hydroxide is comprised of potassium hydroxide, sodium hydroxide, or a combination thereof.

6. The method of claim 5, wherein effective conditions for treating the aqueous alkali carbonate stream with regenerated calcium oxide comprise a temperature of at least about 135°

C. (275°

F.) and a pressure of at least about 200 psig (1379 kPa).

7. The method of claim 5, wherein washing the hydrocarbon feedstream and separating potassium hydrogen sulfide particles from the hydrocarbon feedstream in step b) comprises desalting the hydrocarbon feedstream using an electrostatic precipitator.

8. The method of claim 5, wherein heating the calcium carbonate under effective conditions comprises heating the calcium carbonate to at least about 900°

C. (1652°

F.).

9. The method of claim 5, further comprising seeding the aqueous alkali carbonate stream with calcium carbonate particles prior to or during said mixing with regenerated calcium oxide.

10. The method of claim 5, wherein heating the calcium carbonate further comprises forming carbon dioxide, the method further comprising:

collecting the carbon dioxide formed by heating of the calcium carbonate, wherein at least a portion of the collected carbon dioxide is used for said treating of the aqueous alkali metal salt stream.

11. The method of claim 5, wherein washing the hydrocarbon feedstream with water to form a hydrocarbon product stream and an aqueous alkali metal salt stream containing alkali metal salt is performed under conditions of at least 120°

C. (248°

F.) and 100 psig (690 kPa).

12. The method of claim 5, wherein mixing the aqueous alkali carbonate stream with regenerated calcium oxide under effective conditions to form alkali hydroxide and calcium carbonate solids is performed under conditions of at least 120°

C. (248°

F.) and 200 psig (1379 kPa).

13. The method of claim 1, further comprising:

mixing at least a portion of the aqueous alkali metal hydroxide with a hydrocarbon feedstream having an API less than about 19 and a sulfur content of at least about 0.5 wt % under effective desulfurization conditions to form an at least partially desulfurized hydrocarbon feedstream and alkali metal hydrogen sulfide particles.

14. The method of claim 13, wherein the effective desulfurization conditions include a pressure from about 50 to about 3000 psi (345 to 20,684 kPa), a temperature from about 600°

F. to about 900°

F. (316°

C. to 482°

C.), and a aqueous alkali metal hydroxide concentration of at least about 7.5 wt % relative to the weight of the hydrocarbon feed.

15. The method of claim 14, wherein the effective desulfurization conditions further comprise a hydrogen partial pressure about 100 to about 2500 psi (689 to 17,237 kPa).

16. The method of claim 14, further comprising:

heating the mixed hydrocarbon feedstream and aqueous alkali metal hydroxide to form alkali metal hydroxide particles, alkali metal sulfide particles, or a combination thereof to a temperature of at least 150°

C. (302°

F.) and removing at least a portion of the water therein prior to subjecting the mixed hydrocarbon feedstream and aqueous alkali metal hydroxide stream to effective desulfurization conditions.

17. The method of claim 16, wherein the alkali metal hydroxide is comprised of potassium hydroxide, sodium hydroxide, or a combination thereof.

18. A method for regenerating an alkali metal salt reagent, comprising:

a) receiving a hydrocarbon feedstream having an API gravity of at least about 20, the hydrocarbon feedstream including at least about 7.5 wt % of alkali metal salt particles, the alkali metal salt particles comprising alkali hydrogen sulfide particles;

b) washing the hydrocarbon feedstream with water to form a hydrocarbon product stream and an aqueous stream containing alkali metal salt;

c) splitting the aqueous stream comprising alkali metal salt into a first portion and a second portion;

d) treating the first portion of the aqueous alkali metal salt stream with carbon dioxide under effective conditions to form aqueous alkali carbonate;

e) mixing the aqueous alkali carbonate with calcium oxide under effective conditions to form alkali hydroxide and calcium carbonate solids;

f) separating the calcium carbonate from the aqueous alkali hydroxide;

g) combining the second portion of aqueous alkali metal salt with the aqueous alkali hydroxide;

h) dehydrating the combined aqueous alkali metal salt and aqueous alkali metal hydroxide to form alkali metal sulfide; and

i) heating the calcium carbonate under effective conditions to form regenerated calcium oxide, wherein at least a portion of the regenerated calcium oxide is used for said mixing with aqueous alkali carbonate.

19. The method of claim 18, wherein dehydrating the combined aqueous alkali metal salt and aqueous alkali hydroxide comprises heating the combined aqueous alkali metal salt and aqueous alkali hydroxide to at least about 350°

C. (662°

F.).

20. The method of claim 19, wherein the alkali metal salt is comprised of potassium hydroxide, sodium hydroxide, or a combination thereof.