US3494860A - Steam desulfurization process - Google Patents

Description

STEAM DESULFURIZATION PROCESS Filed March 11, 1968 DESULFURIZED LIGHT OIL WATER PARATOR n :1 S E 8 9 o m n. 3 o o 2 Q '5 n: N E E2 h. E D 8 INVENTOR. g CLYDE L. ALDRIDGE ATTORNEY United States Patent US. Cl. 208-248 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to a continuous process for the desulfurization of heavy petroleum oils in the presence of steam and a catalyst comprising a supported metal salt in which the metal is selected from the group consisting of metals of Groups I-A, III-B, V-B, VIB, VII-B, VIII-B, thorium and the Lanthanide Series of the Periodic Table.

This application is a continuation in part of my application Ser. No. 559,932, filed June 23, 1966.

The steam desulfurization process of the invention is applied to a heavy petroleum feedstock. The three major characteristics of some heavy petroleum oils, such as residuums are that they contain (1) asphaltenes and other high molecular weight aromatic structures which severely inhibit the rate of desulfurization, and cause catalyst deactivation, (2) ash forming constituents such as metalloorganic compounds which contaminate catalysts and interfere with catalyst regeneration, and (3) a relatively large quantity of sulfur which is difiicult to remove and which gives rise to objectionable quantities of S0 and S0 upon combustion when it is not removed.

The most effective method for removal of sulfur from heavy oils without substantial conversion of the oil to light hydrocarbons is catalytic hydrodesulfurization. Obviously the high cost of hydrogen places severe economic debits on this process.

For this reason, desulfurization with steam is of interest because of the relatively low cost of steam. The principal object of this invention is to provide a process for the desulfurization of heavy petroleum fractions with steam in the presence of an active catalyst. The process is centered on nondestructive desulfurization as distintinguished from destructive desulfurization, e.g. steam cracking. Thus conversion to gas and light ends is minimized. Another object of this invention is to disclose a continuous catalytic steam desulfurization process featuring a durable, regenerable catalyst. Further objects and advantages of the invention will be apparent from the following description which discloses certain nonlimiting embodiments. The drawing is a schematic representation of a preferred mode of conducting the process.

Summarizing briefly, the objects of the invention are attained by desulfurizing heavy petroleum oils at moderate conditions in the presence of steam and a catalyst comprising a metal salt in which the metal is selected from the group consisting of metals of Groups I-A, III-B, V-B, VIB, VII-B, VIII-B, thorium and the Lanthanide Series of the Periodic Table, said metal salts being supported on a durable carrier which can be regenerated, preferably by burning.

The process feedstock is a heavy petroleum oil. The oil can be a heavy oil fraction such as atmospheric gas oil or vacuum gas oil, a deasphalted oil, whole crude oil or a residual fraction such as atmospheric distillation bottoms or vacuum distillation bottoms. The feed can be Patented Feb. 10, 1970 a blend of any of the oils mentioned above as well as such refinery materials as coker distillates, cat cracked fractions, visbreaker fractions, etc. One of the most suitable feeds for the process is a petroleum fraction or a petroleum residuum containing at least 10 vol. percent of material boiling above 900 F. and having a Conradson Carbon of at least 2. The feeds will contain 0.5-l0 wt. percent sulfur, 10-2000 p.p.m. metals, and they may also contain nitrogen compounds. Another preferred feed is a gas oil boiling in the range of from about 400 F. to about 1000 F. The process can also be applied to certain fractions derived from coal, oil shale and tar sands. The feed can be oxidized by contact with an oxygen containing gas to make it more amenable to steam desulfurization. The feed can be diluted with a light oil.

The catalyst comprises a metal salt on a support. In the broad sense the metal is selected from the group consisting of metals of Groups IA, IIIB, V-B, VIB, VII-B, VIII-B, thorium and the Lanthanide Series of the Periodic Table. Appropriate salt forms include the oxides, the hydroxides, the sulfides, the sulfates, the carbonates and hydrates of these salt forms.

Salts of certain metals are more active than others and the preferred metals are thorium, yttrium, lanthanum, cerium, neodymium, samarium and rare earth mixtures containing several rare earths and in some cases yttrium, thorium and lanthanum. The rare earth mixtures are usually crude naturally occurring or semirefined mixtures.

Certain salts are more suitable to catalyst preparation and the nitrates, the oxide hydrates, the chlorides and the carbonates of the preferred group of metals are ordinarily used.

The most preferred catalysts are hydrated mixed rare earth oxides, hydrated lanthanum oxide, and thorium oxide.

The catalyst support is an important aspect of the invention. The support must be able to withstand continuous intimate contact with steam during the desulfurization reaction and frequent contact with hot gases during regeneration to remove carbonaceous deposits laid down during the reaction. Suitable support materials include alumina, silica alumina, bauxite, kieselgnhr, molecular sieves, natural and synthetic zeolites, magnesia, charcoal. Alpha alumina is the most preferred support.

The catalyst should have a surface area of at least about 1.0 m. g. The finished catalyst can be in the form of extrudates, pills, spheres or any other attrition resistant form.

As stated in my earlier application it is believed that the in situ active catalyst form is a hydrate formed by contact with the steam.

EXAMPLE I A catalyst suitable for use in steam desulfurization was prepared in the following manner. 7.15 gms. of lanthanum carbonate (City Chemical Company, New York, N.Y.) was dissolved in an excess of dilute nitric acid and added to 50 gms. of alpha alumina (Type SAHT- 99, Canborundum Company, Latrobe, Pa.). Suflicient Water was included to thoroughly wet the mixture. The mixture was stirred, blended and dried over night in an atmosphere of air at about C. 59 gms. of catalyst was recovered. The catalyst contained about 15 wt. per cent lanthanum salts and salt hydrates and the balance alumina support.

EXAMPLE II A preferred catalyst for steam desulfurization was made in a manner similar to that set forth above except that concentrated (1/ 1) acid was used and the active ingredient was 4.34 gms. of commercial mixed rare earth oxide hydrate (Trona-American Potash and Chemical Corporation). After compositing with the alumina sup port the catalyst contained about 1 wt. percent rare earth oxide hydrate and the balance alumina.

Referring to the drawing, an oil feed of the type previously mentioned is passed by line 1 through heat exchanger 2 to the upper section of reactor 3. The oil is preferably heated to a temperature near the desired temperature of the reactor. Steam enters the reactor via line 4. Air for in situ feed oxidation and/or regeneration of the catalyst is fed into the reactor via lines and 4. In this embodiment the reactants pass cocurrently down through the fixed catalyst beds. If desired the reactor can be operated with cocurrent flow of steam, air and oil upwardly through the reactor or the steam and air can be passed upwardly, countercurrent to the downwardly moving oil.

Typical steam desulfurization reaction conditions are as follows:

TABLE I.REACTION CONDITIONS, STEAM DESULFURI- ZATION In this embodiment a fixed bed of catalyst is used, however alternate means of contacting such as a fluidized bed, moving bed, slurry, ebbulating bed, etc. can be employed. The catalyst is selected from those mentioned previously and a preferred catalyst is the mixed rare earth catalyst of Example 2.

Regeneration is accomplished by cutting off the flow of oil and passing a steam-air mixture from lines 4 and 5 through the catalyst bed under combustion conditions to burn carbonaceous deposits from the catalyst surfaces. Air contents of 30( vol. percent air on steam) and bed temperatures in the range of 500 to 2000 F. are used for regeneration.

A plurality of reactors can be operated in stages so that one or more reactors are in the regeneration stage While the others are in steam desulfurization operation.

It is within the scope of the invention to pass oil and catalyst through the reactor in slurry form and to regenerate catalyst in a separate regenerator. It is also within the scope of the invention to omit regeneration and to periodically remove a portion of spent catalyst from the reactor and replace it with fresh catalyst.

Steam desulfurization effiuent is removed from reactor 3 by line 6. The efiluent comprises unreacted air, steam, hydrocarbon gases, H 8, hydrocarbon vapors, desulfurized liquid oil and partially desulfurized oil. The efiluent is passed into separator 7. In the case of a gas oil process feed a major amount, e.g. 50l00 percent of the desulfurized material will be in the vapor phase. It the feed is a vacuum residuum a major amount, i.e. 50 to 100 vol. percent will be in the liquid phase. Gases and vapors are passed overhead from the separator by line 8. Liquid material is recovered from the separator by line 10. If desired, part of the oil, e.g., from 5 to vol. percent is recycled via lines 10 and 1. Desulfurized product is recovered from line 9.

The gas and vapors products are passed by line 8 through heat exchanger 2 and pressure reduction valve 11 into separator 12. Separator 12 is operated at a temperature in the range of to 300 F. and a pressure in the range of 15 to 100 p.s.i.a. Uncondensed gases are recovered by line 13. Desulfurized light oil is recovered by line 14 and water is recovered by line 15.

The process of the invention provides a means for the desulfurization of heavy oils without the use of expensive hydrogen. Instead low cost steam is the desulfurization agent and air can be used to oxidize, e.g., activate the feed. The catalysts employed in the process are active promoters of the hydrolysis reaction and are durable in continuous operations including regentration.

I claim:

1. A process for the desulfurization of a high sulfur petroleum oil comprising continuously contacting the oil at elevated temperature with steam in the presence of a support mixture of rare earth salts and recovering desulfurized oil.

2. Process according to claim 1 in which the oil contains 0.5-10 weight percent sulfur.

3. Process according to claim 1 in which the oil contains at least 10 volume percent of material boiling above 900 F. and 102000 ppm. metals.

4.. Process according to claim 1 in which the oil is a gas oil.

5. Process according to claim 1 in which the oil is an atmospheric residuum.

6. Process according to claim 1 in which the carrier is alpha alumina.

7. Process according to claim 1 in which the feed is oxidized in situ with air.

8. Process according to claim 1 in which the catalyst is periodically regenerated with a steam-air mixture.

9. Process according to claim 1 in which the alumina support has a surface area of at least 1.0 square meters per gram.

10. Process according to claim 1 in which said oxide is hydrated.

References Cited UNITED STATES PATENTS 3,380,915 4/1968 Mattox et al. 20828 2,813,837 11/1957 Holden 252-465 2,500,146 3/1950 Fleck et al. 260-668 2,697,066 12/1954 Sieg 19650 FOREIGN PATENTS 907,770 10/1962. Great Britain.

DELBERT E. GANTZ, Primary Examiner J. NELSON, Assistant Examiner US. Cl. X.R. 208-297; 252462

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