Sulfone cracking using supercritical water

Abstract

The invention relates to a process for removing sulfur compounds from a hydrocarbon stream. The hydrocarbon stream is contacted with water, at supercritical conditions and also subjects an effluent hydrocarbon stream to separation techniques. The resulting hydrocarbon stream is substantially free of sulfur oxides, sulfoxides, and sulfones.

Claims

1. A process for converting oxides of sulphur, sulfones and sulfoxides in a hydrocarbon stream into their salt derivatives and SO.sub.x gases, wherein x is 2 or 3, comprising: a) contacting said hydrocarbon stream with water, at supercritical water conditions in a reaction zone of a reactor, to form an effluent stream which contains said SO.sub.x gases, said hydrocarbon stream and water being combined at a volume ratio of from about 1:5 to about 1:1, b) transferring said effluent stream to a separator, and c) separating said SO.sub.x gases from said effluent stream.

2. The process of claim 1, comprising adding a molybdenum catalyst to said reaction zone.

3. The process of claim 1, comprising reacting said hydrocarbon stream and water at supercritical water conditions in a basic medium.

4. The process of claim 3, comprising reacting said hydrocarbon stream and water at supercritical water conditions in the presence of fluoride ions.

5. The process of claim 4, wherein said fluoride ions are obtained from at least one alkali metal compound of Group IA of the Periodic Table.

6. The process of claim 1, comprising reacting said hydrocarbon stream and water at supercritical water conditions in an acidic medium.

7. The process of claim 6, wherein said acid medium is liquid or solid.

8. The process of claim 7, comprising reacting said hydrocarbon stream and water at supercritical water conditions in the presence of formic acid.

9. The process of claim 1, wherein said sulfones, sulfoxides, and oxides of sulfur, have a boiling point in the range of from about 180 C. to about 1500 C.

10. The process of claim 1, wherein residence time in said reaction zone is from about 1 minute to about 600 minutes.

11. The process of claim 10, wherein the residence time is from about 5 minutes to about 120 minutes.

12. The process of claim 11, wherein the residence time is from about 10 minutes to about 60 minutes.

13. The process of claim 1, wherein the hydrocarbon stream/water volume ratio is 1:5.

14. The process of claim 1, wherein the hydrocarbon stream/water volume ratio is 1:2.

15. The process of claim 1, wherein the hydrocarbon stream/water volume ratio is 1:1.

16. The process of claim 1, wherein said reaction zone is selected from the group consisting of a batch, fixed-bed, ebullated-bed, moving-bed and a slurry-bed reactor.

17. The process of claim 1, wherein the hydrocarbon stream is whole crude oil, synthetic crude oil, bitumen, oil shale, coal liquid, a refined intermediate or a final product.

18. The process of claim 2, wherein the molybdenum catalyst is supported on a material selected from the group consisting of silica-alumina, alumina, natural or synthetic zeolites and activated carbon.

19. The process of claim 2, comprising reacting said hydrocarbon stream and water in more than one reactor, more than one reactor being arranged in series or parallel and each of said reactors containing a different catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow diagram of the process of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) The present invention comprehends a process to convert hydrocarbon streams containing oxides of sulfur, sulfones and sulfoxides. The process includes the following steps:

(3) a) contacting the hydrocarbon stream with water in a reactor at supercritical water conditions in the absence of a catalyst or in the presence of a catalyst or additive; and,

(4) b) subjecting the effluent hydrocarbon stream to a vapor/liquid/liquid separator to obtain a hydrocarbon fraction free of oxides of sulfur, SOx and water containing salts and derivatives of oxides of sulfur.

(5) In the process of the present invention, sulfones and sulfoxides and mixtures thereof are recovered from oxidative desulfurization by extraction and/or adsorption and/or absorption and/or membrane separation and/or distillation and/or solvent deasphalting and/or filtration and/or phase separation and are contacted with supercritical water either in the presence or absence of a catalytic system to break the carbon-sulfur bond.

(6) The sulfoxides and/or sulfones may be derivatives of aliphatic sulfides, aromatic sulfides and mercaptans having a boiling point above 180 C. and up to about 1500 C.

(7) The sulfoxides and/or sulfones may be derived from feedstocks, which may be whole crude oil or its fractional distillates boiling between 36 C. and 370 C. or residues boiling above 370 C. or hydrocarbons from intermediate refinery processing units, such as coking gas oils, FCC cycle oils, deasphalted oils, bitumens from tar sands and/or its cracked products, coal liquids.

(8) Referring now to the drawing (FIG. 1), there is schematically illustrated an embodiment suitable for practicing the invention that includes two major vessels that are functionally described as supercritical water reactor vessel 10 and vapor/liquid/liquid separator vessel 20. All other process equipment, such as pumps, heat exchangers, flash vessels and valves are not shown in the drawing FIGURE.

(9) In a particularly preferred embodiment, all of the vessels are operated as components in a continuous process. The hydrocarbon stream containing oxidized sulfur products including sulfoxides and sulfones feedstream 11, water 12 and the optional catalyst or additives 13 are combined and the combined feedstream 14 is fed to the supercritical water reactor vessel 10. The supercritical water reactor vessel 10 can be operated as an ebullated-bed reactor, a fixed-bed reactor, a tubular reactor, a moving-bed reactor or a continuous stirred-tank reactor.

(10) The supercritical water reactor effluents stream 15 is then transferred to the vapor/liquid/liquid separator 20 to separate and recover the reaction products SO.sub.x, wherein x is 2 or 3 and other hetero-containing gases, H.sub.2S and NH.sub.3 stream 16, hydrocarbons 17 and water containing salt derivatives of sulfones and sulfoxides 18. The recovered water stream 19 can be recycled back to the supercritical water reactor or bled/rejected from the process stream 20.

(11) The reaction with supercritical water may take place in the presence or absence of a catalytic system. The catalysts which can be used may be homogeneous or heterogeneous catalysts, which may include one or a combination of elements from Groups IVB, V and VI of the Periodic Table. The catalysts may be metals or dispersed on support material, with the preferred catalyst being molybdenum.

(12) The support material may be silica-alumina, alumina, natural or synthetic zeolites, or activated carbon.

(13) The reactors, if more than one, may be arranged in series or parallel and may contain different types of catalysts/additives or may be operated at different water-to-oil ratios.

(14) The reactions are carried out at temperatures above supercritical conditions, namely, in the range of about 380 C., to about 600 C., and at a pressure range of about 220 bars to about 450 bars.

(15) The residence time can be about 1 minute to about 600 minutes, with a preferred residence time of about 5 minutes to about 120 minutes, with a residence time of about 10 minutes to about 60 minutes being preferred.

(16) The oil-to-water volume ratio can be about 1:5, with a ratio of about 1:2 being preferred and a ratio of about 1:1 being especially preferred.

(17) Exemplary of the sulfones and sulfoxides which are present in crude oil fractions, but not limited thereto, are sulfones and sulfoxides of thiols, sulfides, benzothiophene, dibenzothiophene, naphthothiophene, naphthobenzothiophene, benzonaphthothiopene and their alkylated derivatives.

(18) While the cracking mechanism employing supercritical water is not known with certainty, it is postulated that hydrogen is generated at supercritical water conditions, which minimizes coke formation and enhances the cracking reactions, resulting in the stabilization of the free radicals which are formed.

(19) The sulfone cracking of the present invention may take place optionally in a basic medium, such as fluorides, or in an acidic medium using solid or liquid acids, such as formic acid.

(20) Fluoride ion is known to be an efficient and strong base for use in organic reactions, if employed in dry aprotic solvents. However, the hydrogen bond of protic solvents usually serve to mask the fluoride ion by a specific solution which makes the fluoride ion a weak base. Water at elevated temperatures (>250 C.), behaves like an organic aprotic solvent. Its density, dielectric constant, Hildebrand solubility parameter and hydrogen bonding structure decrease significantly. Therefore, water at high temperatures becomes more compatible for organic reactions.

(21) While only certain embodiments have been set forth, alternatives and modifications will be apparent from the foregoing to those skilled in the art. Such alternatives and modifications are considered to be equivalents and within the spirit and scope of the appended claims.