Catalytic demetallization 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 hydrodemetallization and then gas phase oxidative desulfurization. Additional, optional steps including hydrodesulfurization, and hydrocracking, may also be incorporated in to the integrated process.

Claims

1. An integrated process for removing metals and sulfur from a residual oil hydrocarbon feedstock, consisting of: (i) subjecting said hydrocarbon feedstock to hydrometallization in a first vessel, in the presence of a hydrodemetallization catalyst, under hydrodemetallization conditions, to produce a hydrodemetallized product which comprises a first gas, a top fraction, and a bottom fraction; (ii) moving said bottom fraction to a second vessel, said second vessel containing an oxidative desulphurization (ODS) catalyst; (iii) contacting said bottom fraction and ODS catalyst with a gaseous oxidizing agent, to form SO.sub.2, a liquid fraction and a second gas in a gaseous ODS process; (iv) separating said second gas and said liquid fraction produced in (iii) from each other; (v) removing a portion of said second gas, leaving a remainder; (vi) recycling said remainder to said second vessel, and; (vii) removing said liquid fraction.

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

3. The method of claim 1, wherein said bottom fraction, ODS catalyst and gaseous oxidizing agent are contacted to each other at a temperature of from 300 C. to 600 C.

4. The method of claim 3, wherein said temperature is 400 C.-550 C.

5. The method of claim 1, contacting wherein said gaseous oxidizing agent is contacted with said bottom fraction at an O.sub.2/S atomic ratio of from 20-30.

6. The method of claim 5, wherein said ratio is 25-30.

7. The method of claim 1, wherein said gaseous oxidizing agent, ODS catalyst and bottom fraction are contacted at a pressure of from 1 bar-20 bars.

8. The method of claim 7, wherein said pressure is 1-10 bars.

9. The method of claim 8, wherein said pressure is 1-5 bars.

10. The method of claim 1, wherein said bottom fraction, ODS catalyst and gaseous oxidizing agent are contacted to each other at a WHSV of 1-20 h.sup.1.

11. The method of claim 10, wherein said WHSV is 5-10 h.sup.1.

12. The method of claim 1, wherein said bottom fraction, ODS catalyst, and gaseous oxidizing agent are contacted to each other at a GHSV of 1,000-20,000 h.sup.1.

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

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

15. An integrated process for removing metals and sulfur from a residual oil hydrocarbon feedstock, consisting of: (i) subjecting said hydrocarbon feedstock to hydrometallization in a first vessel, in the presence of a hydrodemetallization catalyst, under hydrodemetallization conditions, to produce a hydrodemetallized product which comprises a first gas, a top fraction, and a bottom fraction; (ii) moving said bottom fraction to a second vessel, said second vessel containing an oxidative desulphurization (ODS) catalyst; (iii) contacting said bottom fraction and ODS catalyst with a gaseous oxidizing agent, to form SO.sub.2, a liquid fraction and a second gas in a gaseous ODS process; (iv) separating said second gas and said liquid fraction produced in (iii) from each other; (v) removing a portion of said second gas, leaving a remainder; (vi) recycling said remainder to said second vessel, and; (vii) removing said liquid fraction, and; (viii) subject said liquid fraction of (vii) to hydrocracking in the presence of hydrogen and a hydrocracking catalyst.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a broad embodiment of the invention, showing an integrated process where hydrodemetallization is followed by gas phase oxidative desulphurization (ODS).

(2) FIG. 2 shows an embodiment of the invention where a hydrodesulphurization step follows ODS.

(3) FIG. 3 shows parallels FIG. 2, but hydrocracking follows ODS.

(4) FIG. 4 shows an embodiment where hydrodemetallization is followed by hydrodesulphurization, which is followed by ODS.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) Referring now to the figures, FIG. 1, shows the invention in its broadest embodiment. A hydrocarbon feedstock or fuel, such as residual oil is a feedstream 1 to a hydrodemetallization, vessel 2, together with hydrogen 3. A hydrodemetallization catalyst, not shown and discussed infra, is present in vessel 2. Hydrodemetallization takes place at standard conditions, producing an effluent, which moves to a separation vessel 4, where gases are separated to vessel 5, and either bled from the system 6, or in the case of hydrogen, recycled 7 to the hydrodemetallization reaction.

(6) The other component of the effluent is a demetalized residual oil 8, which moves to an oxidative desulphurization vessel 9, and is combined with an oxidizing agent like oxygen gas 10. After the gas phase ODS process takes place, in the presence of a catalyst and at standard ODS conditions as described herein, the products are moved to another separation vessel 11, where desulphurized residual oil 12 is removed and used for other purposes, and gas is removed to another vessel 13, where it is bled from the system 14, or in the case of oxygen, recycled 15, to the ODS reaction.

(7) FIG. 2 shows an embodiment where the desulphurized residual oil 12 moves to a hydrodesulphurization vessel 16, together with another source of hydrogen 17. Following hydrodesulphurization, the products are separated into gases, and an ultra low desulfurized residual oil 18. Any gases are separated to a vessel 19, and hydrogen is recycled 20, and other gases bled from the system.

(8) FIG. 3 shows a further option, where the desulphurized residual oil 12 moves to a hydrocracking vessel 21. Optionally, some of the unconverted oil 22 moves to 21 and, as shown, some in the form of unconverted residual oil 22, is removed.

(9) The portion of the oil which moves to vessel 21 is mixed with hydrogen 23, and hydrocracked. Products of hydrocracking are separated in vessel 24, with residual oil distillates removed, while gas 25 is either bled from the system 26, or in the case of hydrogen, recycled 27 to the hydrocracking unit.

(10) FIG. 4 shows an embodiment where a hydrodesulphurization reaction takes place before ODS, but after hydrodemetallization. All components remain the same as in FIGS. 1-3.

EXAMPLE

(11) The hydrocarbon feed in this example was a vacuum residue from Arabian heavy crude oil. Table 6, which follows, sets forth its properties:

(12) TABLE-US-00006 TABLE 6 Properties of Arab heavy vacuum residue Property Unit Value API Gravity 1.6 Specific Gravity 1.063 Carbon wt % 83.61 Hydrogen wt % 10.15 Sulfur wt % 6.13 Nitrogen ppmw 3781 Micro Carbon Residue wt % 29.5 (MCR) 565 C.+ wt % 94.2 Ni ppmw 47 V ppmw 137

(13) It will be seen that this sample contains very high levels of Ni (47 ppmw), V (137 ppmw), and S (6.13 wt %).

(14) This sample was subjected to HDM, at 402 C., 165 bars of hydrogen partial pressure, 0.18 h.sup.1 of liquid hourly space velocity, and a hydrogen:oil ratio 702 liters of hydrogen per liter of oil. The reactor contained an ebullated bed, hydrodemetallization catalyst. The catalyst, obtained from a commercial source, contained from 5.4-6.6 wt % Mo, 2.0-2.6 wt % Ni, and had pores which ranged from 2.3-6.4 mm in length, and from 0.9-1.1 mm in diameter. (A very small fraction of the pores were outside of these ranges). (Many commercial HDM catalysts are known, and any can be used, as can any form of catalyst bed, e.g., ebullated, fixed, fluid, or moving).

(15) Table 2, which follows, shows that 91.8 wt % of Ni, and 98.1 wt % of V were removed in this step. The feed was converted, at 63.4 wt %, and total liquid yield, was 91.38 wt %. See Table 7 (infra):

(16) TABLE-US-00007 TABLE 7 Hydrodemetallization process performance Reaction Unit Value 565 C.+ Resid Conversion Vol % 63.4 HDS wt % 87.2 MCR Removal wt % 69.6 Nickel Removal wt % 91.8 Vanadium Removal wt % 98.1

(17) The products were separated in a high pressure separator, resulting in gases, a liquid top product, and a bottom product. See, Table 8:

(18) TABLE-US-00008 TABLE 8 Hydrodemetallization product yields Yield, Component wt % SG S, wt % Ni, ppmw V, ppmw H2S 5.69 NH3 + H2O 0.88 C1 0.56 C2 0.47 C3 0.66 C4 1.20 Tops.sup.1 7.45 0.761 0.120 Bottoms.sup.2 83.94 0.952 0.929 1.4 1.3 Total 100.83 .sup.1ASTM D2887 Distillation 10 W % = 92 C., 30 W % 100 C., 50 W % = 106 C., 70 W % = 221 C., 90 W % = 373 C. .sup.2ASTM D6352 Distillation 10 W % = 308 C., 30 W % 437 C., 50 W % = 532 C., 70 W % = 604 C., 90 W % = 735 C.

(19) The bottom product/fraction was then subjected to gas phase ODS, in a fixed bed reactor using catalyst 1B-MoO.sub.3/CuZnAl. The reaction temperature was 500 C., pressure was 1 bar, weight liquid hourly space velocity was 6 h.sup.1, and the oxygen:sulfur ratio was 26.

(20) Gas phase ODS reduced the sulfur content to 0.49 wt %, lower than the specifications set by the International Maritime Organization for bunker fuels.

(21) The foregoing description and examples set forth the invention, which is an integrated process for hydrodemetallization and desulfurization of a residual oil fraction of a hydrocarbon feedstock. This is accomplished by integrating a hydrodemetallization 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.

(22) The gas fraction will be addressed infra; however, the bottom 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 bed 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 a ratio of the oxidizing agent, such as, O.sub.2 to sulfur (calculated in the liquid), is from 20-30, preferably 25-30.

(23) 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.

(24) As noted, supra, during the HDM phase, gases are produced. The resulting gases can be removed and separated. 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.

(25) Prior to, or after the ODS step, the liquid may be hydrodesulfurized, using methods known in the art, using hydrogen and an 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 minimis quantities of metals.

(26) 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.

(27) 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.

(28) 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

(29) The aforementioned spinel phase is better represented by:
Cu.sub.xZn.sub.xAl.sub.2O.sub.4

(30) where x is from 0 to 1, preferably 0.1 to 0.6, and most preferably from 0.2 to 0.5.

(31) The catalysts 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.sup.3/g. HDM catalysts generally have wide pore openings and high volumes so as to accommodate metals.

(32) In a more preferred embodiment, the ODS catalyst composition is: 20-45 wt % CuO 10.fwdarw.20 wt % ZnO 20-70 wt % Al.sub.2O.sub.3

(33) and even more preferably: 30-45 wt % CuO 12.fwdarw.20 wt % ZnO 20-40 wt % Al.sub.2O.sub.3.

(34) 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.

(35) The catalysts can be on a zeolite support, such as an H form zeolite, e.g., HZSM-5, HY, HX, H-mordenite, H-, 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.

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

(37) 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.