Integrated process for solvent deasphalting and gas phase oxidative desulfurization of residual oil

Abstract

The invention is an integrated process for treating residual oil of a hydrocarbon feedstock. The oil is first subjected to solvent deasphalting then gas phase oxidative desulfurization. Additional, optional steps including hydrodesulfurization, and hydrocracking, may also be incorporated into the integrated process.

Claims

1. An integrated process for removing metals and sulfur from a residual oil feedstock, consisting of: (i) deasphalting said residual oil feedstock in a first vessel, in the presence of a paraffinic solvent, to produce a gas, asphalt and deasphalted oil (residual DAO); (ii) separating said gas, asphalt and residual DAO from each other and also from said paraffinic solvent; (iii) moving said residual DAO to a second vessel containing an oxidative desulfurization (ODS) catalyst; (iv) contacting said residual DAO and ODS catalyst with a gaseous oxidizing agent at a temperature of from 300-600 C., to form SO.sub.2, a second gas, and a liquid in a gaseous ODS process to remove sulfur in said residual DAO; (v) separating the second gas and liquid produced in (iv) from each other; (vi) removing a portion of said gas of (v) from the total gas, leaving a remainder; and (vii) recycling said remainder to said second vessel.

2. The process of claim 1, wherein said ODS catalyst is in the form of a fixed, ebullated, moving or fluidized bed.

3. The process of claim 1, wherein said temperature is 400 C.-550 C.

4. The process of claim 1, wherein said gaseous oxidizing agent is contacted to said residual DAO at an O.sub.2/S atomic ratio of from 20-30.

5. The process of claim 4, wherein said ratio is 25-30.

6. The process of claim 1, wherein contacting said gaseous oxidizing agent, ODS catalyst and residual DAO is at a pressure of from 1 bar-20 bars.

7. The process of claim 6, wherein said pressure is 1-10 bars.

8. The process of claim 7, wherein said pressure is 1-5 bars.

9. The process of claim 1, wherein contacting said gaseous oxidizing agent, ODS catalyst and residual DAO is at a WHSV of 1-20 h.sup.1.

10. The process of claim 9, wherein said WHSV is 5-10 h.sup.1.

11. The process of claim 1, wherein contacting said residual DAO, ODS catalyst, and gaseous oxidizing agent is at a GHSV of 1,000-20,000 h.sup.1.

12. The process of claim 11, wherein said GHSV is 5,000-15,000 h.sup.1.

13. The process of claim 12, wherein said GHSV is 5,000-10,000 h.sup.1.

14. An integrated process for removing metals and sulfur from a residual oil feedstock, consisting of: (i) deasphalting said residual oil feedstock in a first vessel, in the presence of a paraffinic solvent, to produce a gas, asphalt and residual deasphalted oil (residual DAO); (ii) separating said gas, asphalt and residual DAO from each other and also from said paraffinic solvent; (iii) moving said residual DAO to a second vessel containing an oxidative desulfurization (ODS) catalyst; (iv) contacting said residual DAO and ODS catalyst with a gaseous oxidizing agent at a temperature of from 300-600 C., to form SO.sub.2, a second gas, and a liquid in a gaseous ODS process to remove sulfur in said residual DAO; (v) separating the second gas and liquid produced in (iv) from each other; (vi) removing a portion of said gas of (v) from total gas, leaving a remainder; (vii) recycling said remainder to said second vessel, and (viii) hydrocracking said liquid in the presence of hydrogen and hydrocracking catalyst.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows schematically, the broadest embodiment of the invention.

(2) FIG. 2 shows an embodiment of the invention in which hydrodesulfurization (HDS), follows the gas phase ODS step.

(3) FIG. 3 shows an embodiment of the invention in which ODS is followed by hydrocracking.

(4) FIG. 4 shows an embodiment of the invention where an HDS step precedes the ODS step.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) Referring now to the figures, FIG. 1 shows the invention in its broadest embodiment. Residual fuel oil, an example of a hydrocarbon feedstock 1 is added to a first vessel 2, together with a solvent 3, which is preferably a paraffinic solvent and treated under standard solvent deasphalting conditions. The result is asphalt 4, which is separated for further processing, such as gasification or road asphalt. Also produced via the solvent deasphalting are a liquid phase (DAO) and a solvent, which move to separation zone S. Solvent 6 is separated to a separate vessel 7, DAO 8 is moved to a second vessel 9 for gas phase ODS. A source of an oxidizing agent, such as oxygen gas 18 is provided to vessel 9, which contains an ODS catalyst as described infra. This liquid is subject to ODS, producing a second liquid and a second gas, which are separated from each other in separation zone 10. Gases are separated to zone 11, while the second liquid can now be used in other processes, such as being added to fuels.

(6) The gas moved to zone 11 is voluminous. A portion of it is removed (bled), while any residual oxygen is recycled to the ODS phase.

(7) FIG. 2 shows optional additional steps, which can be carried out on the second liquid of FIG. 1. To elaborate, the desulfurized oil (the second liquid) moves to a third vessel 12, for deep hydrodesulfurization. A source of hydrogen 13 is provided. Again, a liquid and a gas are formed, which are separated in separation zone 14. Again, a portion of the gas is removed after separation to zone 15, and residual hydrogen can be recycled to the ultra deep HDS process.

(8) In FIG. 3, an embodiment is shown where, rather than subjecting the product of ODS to HDS, it is hydrocracked, in the presence of hydrogen and hydrocracking catalysts. FIG. 3 shows hydrocracking vessel 16, and also illustrated as 17, is the distillate from the hydrocracked oil, previously subjected to ODS.

(9) FIG. 4 shows an embodiment of the invention, where, intermediate to solvent deasphalting, the DAO is subjected to HDS, prior to ODS. It will be seen that all steps and apparatus are in fact the same as in FIGS. 1-3, but simply have had positions changed.

(10) FIGS. 2 and 3 could logically, follow FIG. 4, as FIGS. 5 and 6, and these new figures would be unchanged.

Example

(11) In this example, the hydrocarbon feed was residual oil derived from light crude oil. This sample has a total sulfur content of about 3 wt %.

(12) The sample was introduced to a first vessel for deasphalting. The deasphalting step took place at a temperature of 70 C., pressure of 40 kg/cm.sup.2, and a solvent:oil ratio of 7:1. The solvent used was propane.

(13) Deasphalting produced deasphalted residual oil, having sulfur content of 1.8 wt %, and asphalt, with sulfur content of 4.50%. (Sulfur content was measured after the two products were separated).

(14) The resulting deasphalted residual oil was moved to a second vessel, and subjected to gas phase oxidative sulfurization. The temperature employed was 500 C., in a fixed bed reactor containing IBMoO.sub.3/CuZnAl catalyst. Other conditions were a pressure of 1 bar, WHSV of 6 h.sup.1, and an oxygen:sulfur atomic ratio of 26.

(15) The results showed that the desulphurized residual oil (the second liquid supra), had a sulfur content of 0.96 wt %a drop of 40%. The total decrease in sulfur, relative to starting material, was 68%.

(16) The liquid which resulted from the solvent deasphalting contained 1.8 wt % sulfur. Following ODS, the sulfur content was 0.96 wt %.

(17) The foregoing description and examples set forth the invention, which is an integrated process for demetallization and desulfurization of the residual oil fraction of a hydrocarbon feedstock. This is accomplished by integrating a solvent deasphalting step, and an oxidative desulfurization step. Optionally, this integrated process may include one or more hydrodesulfurization and/or hydrocracking steps. These optional steps are carried out in the presence of hydrogen and an appropriate catalyst or catalysts, as known in the art.

(18) In practice, a residual oil hydrocarbon feedstock is introduced or contacted to a first vessel, together with a paraffinic alkyl solvent, such as propane, or any pure C.sub.3-C.sub.7 solvent, as well as mixture of these under conditions which may include the addition of hydrogen, to form a demetalized liquid fraction, a gas fraction, and coke.

(19) The gas and coke fractions will be addressed infra; however, the liquid fraction, now with reduced metal and sulfur content is removed to a second vessel, where it is subjected to gas phase oxidative desulfurization, in presence of an oxidative desulfurization catalyst. The catalyst can be present in the form of, e.g., a fixed, ebullated, moving or fluidized bed. The gaseous phase ODS takes place at a temperature of from 300 C. to 600 C., preferably from 400 C. 550 C., and with an oxidative gas, such as pure oxygen, where an atomic ratio of O.sub.2 to sulfur (calculated in the liquid), is from 20-30, preferably 25-30.

(20) Additional parameters of the reaction include a pressure of 1-20 bars, preferably 1-10 bars, and most preferably, 1-5 bars. A WHSV of 1-20 h.sup.1, preferably 5-10 h.sup.1, and a GHSV of from 1,000-20,000 h.sup.1, preferably 5-15,000 h.sup.1, and even more preferably, 5-10,000 h.sup.1 are used.

(21) As noted, supra, during the solvent deasphalting phase asphalt is produced. The resulting asphalt can be removed and gasified, to produce hydrogen gas or sent to asphalt pool to be used in road asphalt. The hydrogen gas can be returned to the first vessel or when an optional HDS or cracking step is used, be channeled to the vessels in which these reactions take place.

(22) The solvent used in the solvent deasphalting step is separated, and can be recycled back to the process while make-up solvent can be added to compensate for losses during the process.

(23) Prior to, or after the ODS step, the liquid may be hydrodesulfurized, optionally via hydrodesulfurization using methods known in the art, using hydrogen and HDS catalysts. Whether this HDS step is done before or after ODS, the resulting hydrocarbon product which results at the end of the process contains very low amounts to sulfur, and de minimus quantities of metals.

(24) The product of ODS may also be hydrocracked, in the presence of hydrogen and hydrocracking catalysts, either before or after an optional HDS step, again resulting in a product with very low sulfur and metal content.

(25) As noted, supra, a gaseous oxidizing agent, such as pure O.sub.2, or air containing O.sub.2, is added to the ODS vessel. The products of ODS are a liquid and a gas. The liquid, as discussed supra, can be used, e.g., as fuel oil. The gas is separated and oxygen can be recycled to the ODS vessel, if desired.

(26) Various ODS catalysts useful in gaseous ODS are known. Preferred are catalysts which comprise oxides of copper, zinc, and aluminum, i.e.: 10-50 wt % CuO 5.fwdarw.20 wt % ZnO 20-70 wt % Al.sub.2O.sub.3 which also contain a highly dispersed spinel oxide phase. While the catalyst itself can be represented by the formula:
CuZnAlO.

(27) The aforementioned spinel phase is better represented by:
Cu.sub.xZn.sub.xAl.sub.2O.sub.4
where x is from 0 to 1, preferably 0.1 to 0.6, and most preferably from 0.2 to 0.5.

(28) The catalyst can be granular, or in forms such as a cylinder, a sphere, a trilobe, or a quatrolobe, with the granules having diameters ranging from 1 mm to 4 mm. The catalysts have a specific surface area of from 10 m.sup.2/g to 100 m.sup.2/g, more preferably 50 m.sup.2/g to 100 m.sup.2/g, pores from 8 to 12 nm, and most preferably 8 nm to 10 nm, and a total pore volume of from 0.1 cm.sup.3/g to 0.5 cm/g.

(29) In a more preferred embodiment, the composition is: 20-45 wt % CuO 10.fwdarw.20 wt % ZnO 20-70 wt % Al.sub.2O.sub.3
and even more preferably: 30-45 wt % CuO 12.fwdarw.20 wt % ZnO 20-40 wt % Al.sub.2O.sub.3.

(30) Especially preferred are catalysts of the type described supra, containing a mixed oxide promoter, such as one or more oxides of Mo, W, Si, B, or P. The example used such a catalyst, with a mixture of Mo and B oxides.

(31) The catalysts can be on a zeolite support, such as an H form zeolite, e.g., HZSM-5, HY, HX, H-mordenite, H-, or an H form of any of MF1, FAU, BEA, MOR, or FER. The H forms can be desilicated, and/or contain one or more transition metals, such as La or Y. When used, the H form zeolite is present at from 5-50 wt % of the catalyst composition, and a silicate module of from 2 to 90.

(32) Other features of the invention will be clear to the skilled artisan and need not be reiterated here.

(33) The terms and expression which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expression of excluding any equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention.