Claims
- 1. In a process for upgrading high boiling hydrocarbon materials to valuable lower boiling materials .[.is.]. .Iadd.in .Iaddend.a hydrogenation operation including at least one expanded bed catalytic hydrogenation zone to produce an upgraded hydrogenated product, the improvement comprising:
- recovering from the upgraded hydrogenation product a recycle liquid having a 5-volume percent distillation temperature of at least 450.degree. F. with at least 25 -volume percent thereof boiling above 950.degree.F.; cooling the liquid recycle to a temperature of at least 350.degree. F. and no greater than 700.degree. F. to .[.separate.]. .Iadd.precipitate coke precursors; .Iaddend..Iadd.removing essentially only .Iaddend.coke precursors from the .Iadd.cooled .Iaddend.liquid recycle; and subsequent to .[.separation.]. .Iadd.removal .Iaddend.of said coke precursors providing the liquid recycle to an expanded bed catalytic hydrogenation zone.
- 2. The process of claim 1 wherein the cooled liquid recycle is passed through a bed of particulate solids to deposit separated coke precursors on the solids.
- 3. The process of claim 2 wherein the recycle liquid is a 600.degree. F..sup.+ fraction.
- 4. The process of claim 1 wherein the recycle liquid is a 1000.degree. F..sup.+ fraction.
- 5. The process of claim 1 wherein the recycle is cooled to a temperature of at least 400.degree. F.
- 6. The process of claim 1 wherein the recycle is cooled to a temperature of no greater than 600.degree. F. .Iadd.7. The process of claim 1 wherein the cooled liquid recycle is centrifuged to enhance separation and removal of coke precursors. .Iaddend. .Iadd.8. The process of claim 7 wherein the
- recycle liquid is a 600.degree. F..sup.+ fraction. .Iaddend. .Iadd.9. The process of claim 7 wherein the recycle is a 1000.degree. F..sup.+ fraction. .Iaddend. 10. The process of claim 7 wherein the recycle is cooled to a temperature of no greater than 600.degree. F.
Parent Case Info
This application is a .Iadd.reissue of U.S. Pat. No. 4,411,768, Ser. No. 370,416 which is a .Iaddend.continuation-in-part of U.S. application Ser. No. 272,720, filed on June 11, 1981, now abandoned, with the aforementioned application being a continuation of U.S. application Ser. No. 106,274, filed on Dec. 21, 1979, now abandoned.
This invention relates to hydrogenation, and more particularly to the hydrogenation of high boiling hydrocarbon materials to provide valuable lower boiling materials.
High boiling hydrocarbon materials, derived from either petroleum or coal sources, typically petroleum residuum or solvent refined coal, are hydrogenated in an ebullated (expanded) catalyst bed in order to produce more valuable lower boiling materials. In general, the conversion levels for such an operation are limited by a tendency to form heavy carbonaceous deposits which result in agglomeration of the catalyst. The limit is at a different conversion level for each feedstock.
As a result, there is a need for an improvement in such hydrocarbon processes in order to permit operation at higher conversion levels.
In accordance with the present invention, there is provided an improvement in a process for upgrading high boiling hydrocarbon materials to valuable lower boiling materials in an ebullated catalytic bed, wherein recycle is recovered from the upgraded product and at least 25%, by volume, of the recycle is comprised of the 950.degree. F..sup.+ components of the product. The liquid recycle is cooled to a temperature of at least 350.degree. F. (most generally at least 400.degree. F.) and no greater than 700.degree. F. (most generally no greater than 600.degree. F.) to separate coke precursors from the liquid recycle, prior to introduction thereof into the ebullated catalytic bed of the hydrogenation operation. Applicant has found that by providing recycle in this manner the operability range of the hydrogenation reaction can be extended to operate at higher levels of conversion.
As hereinabove noted, at least 25%, by volume, of the recycle boils above 950.degree. F. In most cases, the 5-volume percent distillation temperature of the recycle is at least 450.degree. F., preferably at least 550.degree. F., and most preferably at least 600.degree. F. The recycle may be conveniently provided by recovering from the product a 550.degree. F..sup.+ fraction. It is to be understood, however, that the recycle could be a higher boiling fraction; for example a 600.degree. F..sup.+ fraction (the 5-volume percent distillation temperature is at least 600.degree. F. and at least 25-volume percent boils above 950.degree. F.), or a 1000.degree. F..degree. fraction (the 5-volume percent distillation temperature is at least 1000.degree. F.). The recycle is provided as a high boiling recycle in order to minimize the ratio of the 300.degree. F.-550.degree. F. distillate to the 1000.degree. F..sup.+ residue in the liquid phase in the last hydrogenation zone.
In accordance with the present invention, the liquid recycle is treated to remove coke precursors by cooling of the liquid recycle to a preferred temperature of from 350.degree. to 600.degree. F., with such cooling separating coke precursors from the liquid recycle. Coke precursors, which are characterized as being toluene insolubles and heptane insolubles, precipitate from the liquid recycle at such temperatures, and by maintaining the liquid recycle at such temperatures for a sufficient length of time, it is possible to effectively separate and remove such coke precursors from the liquid recycle.
The removal of such coke precursors may be enhanced by a filtration or centrifugation operation; however, it is possible to separate such coke precursors from the liquid recycle without such operation.
It is also possible to enhance the removal of such coke precursors from the liquid recycle at the hereinabove specified temperatures by adding a low boiling liquid to the liquid recycle to reduce the solubility of the coke precursors.
After separating such coke precursors from the liquid recycle, the liquid recycle may be introduced into the ebullated catalytic bed of the hydrogenation reactor, along with the feed thereto, and by separating such coke precursors from the liquid recycle, it is possible to achieve higher conversions, without plugging of the catalyst bed.
In accordance with an embodiment of the invention, the liquid recycle may be cooled to temperatures as hereinabove described, and passed through a bed of particulate material which provides a surface on which the coke precursors may be deposited to thereby facilitate the separation of such coke precursors from the liquid recycle. It is to be understood, however, other surfaces may be used for depositing such coke precursors; accordingly, the scope of the embodiment is not limited to the use of particulate material.
The present invention has particular applicability to a hydrogenation process which is to operate at high conversions; i.e., conversions of greater than 60%, and in particular conversions greater than 70%; however, it is to be understood that the present invention would also be applicable to hydrogenation processes employing an ebullated catalyst bed, which are operated at lower conversions.
The upgrading of the high boiling hydrocarbon materials by hydrogenation in an expanded bed catalytic hydrogenation zone is conducted at temperatures and pressures, and with a catalyst, as generally known in the art; however, by proceeding in accordance with the present invention, it is possible to operate at conversion levels higher than previously employed in the art, without adversely affecting the overall operation. In general, the hydrogenation is conducted at a temperature in the order of from about 650.degree. to about 900.degree. F., preferably from about 750.degree. to about 850.degree. F., and at an operating pressure of from about 500 psig to about 4000 psig, with the hydrogen partial pressure generally being in the order of from about 500 to 3000 psia.
The catalyst which is employed may be any one of a wide variety of catalysts for hydrogenation of heavy materials, and as representative examples of such catalysts, there may be mentioned: cobalt-molybdate, nickel-molybdate, cobalt-nickel-molybdate, tungsten-nickel sulfide, tungsten-sulfide, etc. with such catalyst generally being supported on a suitable support such as alumina or silica-alumina. Such catalyst is maintained in the hydrogenation reactor as an expanded or ebullated bed, as known in the art. In view of the fact that hydrogenation in an ebullated bed is known in the art, no further details in this respect are deemed necessary for a complete understanding of the present invention.
The recycle provided in accordance with the invention is employed in an amount whereby the ratio of recycle to total fresh feed to the hydrogenation is from about 0.2:1 to about 10:1, preferably from about 0.4:1 to about 1.0:1. It is to be understood that each of the hydrogenation zones may or may not include an internal recycle depending on the total flow to the zone. The amount of internal recycle, if any, is adjusted in accordance with the amount of external recycle provided in accordance with the present invention.
The feed to the process, as known in the art, is one which has high boiling components, which are to be converted to more valuable low boiling components. In general, such a hydrocarbon feed has at least 25%, by volume, of material boiling above 950.degree. F. Such feed may be derived from either petroleum and/or coal sources, with the feed generally being a petroleum residuum, such as atmospheric tower bottoms, vacuum tower bottoms, heavy crudes or tars containing small amounts of material boiling below 650.degree. F., or a solvent refined coal, and the like. The selection of a suitable feedstock is deemed to be within the scope of those skilled in the art, and as a result, no further details in this respect are deemed necessary for a complete understanding of the present invention.
The expanded bed catalytic hydrogenation may be accomplished in one, two or more zones, and if there is more than one zone, the recycle, after treatment to remove coke precursors, as hereinabove described, is provided to at least the last of the two hydrogenation zones. The recycle may be provided to the at least last of the two hydrogenation zones. The recycle may be provided to the at least last zone by directly introducing the recycle into the last zone or all or a portion thereof may be introduced into a preceding zone, whereby all or a portion of the recycle to the last zone is provided with the effluent from the preceding zone or zones in the series.
US Referenced Citations (18)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 0480748 |
Jan 1952 |
CAX |
| 2001670 |
Feb 1979 |
GBX |
Continuations (1)
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Number |
Date |
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| Parent |
106274 |
Dec 1979 |
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Continuation in Parts (1)
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Number |
Date |
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| Parent |
272720 |
Jun 1981 |
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Reissues (1)
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Number |
Date |
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| Parent |
370416 |
Apr 1982 |
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Patent Grant
RE32265
