CA1209510A - Process for hydrodemetallation of hydrocarbon oils such as petroleum residua - Google Patents

Abstract

PROCESS FOR HYDRODEMETALLATION OF
HYDROCARBON OILS SUCH AS PETROLEUM RESIDUA

ABSTRACT OF THE DISCLOSURE
Hydrocarbon oils, particicularly petroleum residua, containing 50 - 2000 ppm by weight of metals and substantial amounts of sulfur are effectively cata-lytically hydrodemetallated by forming a three-phase slurry of said oil with hydrogen and a solid hydro-demetallation catalyst of 50 to 300 mesh particle size and passing the slurry through an elongated tubular reactor sized to provide a residence time of from 1.5 to 10 minutes and a liquid flow velocity of from 1 to 15 ft. per second at a temperature of 750° to 900°F and a pressure of 1500 to 2750 psig and, thereafter, isolating the treated oil from the catalyst.

Description

PROCESS FOR E~DRODEr~ETALLATION OF
H~DROCARBON OILS SUCH AS PETROLEUM RESIDUA

BACKGROUND OF THE INVENTION
. .
Field of the Invention The present invention relates to catalytic hydrodemetallation of hydrocarbon oils, particularly liquid petroleum residua or shale oils containing sub-stantial amounts of dissolved metals and sulfur.

The Prior Art The atmospheric or vacuum distillation of crude petroleum yields a residuum ~bottoms~ containing substantial proportions of asphaltenes and other hydro-carbons boiling above about 600F, sulfur and dissolved metal contaminants. Similarly, shale oiL contains high-boiling hydrocarbons and often substantial levels of dissolved metal. It is important to urther pro-cess the residuum's hydrocarbon content to convert its high-boiling materials to commercially attractive lower-boiling hydrocarbon materials. Likewise, shale ~0 oil is furt~er processed to maximize its yield of de-sired low-boiling materials. Gleim, et al, in ~nited States Patent number 3,558,474, provide a represen-tative disclosure of a process whereby vanadium sulfide is slurried in heavy residuum and heated in the pres-ence of hydrogenO In this process the catalyst effectsthree reactions - first, it reacts with or physically absorbs metals and other contaminants, second, it cata-lyzes the conversion of sulfur to hydrogen sulfide, and third, it efects the desired hydrocarbon conver~
sions. This one step process has a serious failin~, however. The metal contaminants tend to deactivate the ~2~$S~

catalyst's activity for the other two reactions and the sulfur contaminants tend to deactivate the catalyst's activity for the hydrocarbon conversion reactions. To compensate, one must raise reaction temperatures, which leads to yield losses, or use large excesses of rela-tively expensive catalyst.
It has been recognized to be of advantage to carry out these reactions separately. Hastings et al disclose in the article "Demetallization Cuts 10 Desulfurization Costs", The Oil and Gas Journal, June 30, 1975, Pages 122-130 that superior results are ob-tained when a three stage process is used including de-metallation followed by desulfurization and then hydro-carbon conversion. A similar teaching may be found in lS Maye, et als' United States Patent number 3,767,569, while Doelp's United States Patent number 3,975,2S9 discloses the simultaneous demetallation and desul-furization of residua and Jacobsen's United States Patent number 3,841,996 disc~oses a circulating loop 20 process for catalytically hydrodesulfurizing and hydro-cracking a residuum. Although the Jacobsen patent suggests using a pretreatment to remove metals, this pretreatment is optional such that the demetallation could be effected in the circulating loop reaction 25 system if desired. The above-mentioned Doelp patent and ~nited States Patent number, ~,214,997 of Ranganathan are of interest for their teaching of the use of slurries of catalyst particles, particularly slurries of colloidal catalyst particles, to effect 30 various hydroprocessing reactions. O~ course, these colloidal particles would be most difficult to remove from the reaction product.
In a decontamination reaction such as hydro-demetallation, there are particular advantages tv a ~ ? $ S

batch process or a fixed bed plug-flow process mode.
In both of these processes, the sxit product is the most completely decontaminated material in the reaction zone. In a stirred back-mixed continuous reaction 5 zone, the exit product is merely an equilibrium product "averaging" newly added contaminated feed with the decontaminated reaction product. This is, of course, less than ideal in the present situations where unre-moved metal can deactivate the catalysts for the desul~
10 furization reaction and/or the hydrocarbon conversion reaction. The batch mode is not realistic for use with the throughputs required in commercial scale refin-ing. Similarly, plug-flow through fixed catalyst beds is not efficient for use in treating crude residua as 15 the front edge of the beds tends to rapidly plug with metals, sulfur, coke, salts and like solids found in or formed from these distillation bottoms.
It is an object of this invention to provide an improvement in catalytic hydrodemetallation pro-20 cesses for metal-contaminated petroleum feedstocks including petroleum residua and shale oils which is effective in (a) removing metals to low levels, (b) permitting continuous operation, and (cj enabling the simple isolation of the demetallated product from the 25 demetallation catalyst.

STATEMENT OF THE INVENTION
_ _ In accordance with the present invention, there is provided a process for catalytic hydrode-metallation of a petroleum feedstock selected from 30 shale oils and residua containing a substantial propor-tion of materials boiling above 600F, containing from 0.5 to 10 weight percent organic sulfur and containing from 20 to 2000 parts per million by weight of " ~2~ !35~C~

metals. This process comprises mixing said feedstock with gaseous hydrogen in an amount minimally in excess of saturation and a solid demetallation catalyst char-acterized as being microporous and as having a uniform 5 50-300 mesh particle size to form a three phase slurry, passing said slurry in agitated plug flow through an elongated tubular reaction zone sized to provide a slurry velocity in the range of 1.0 to 15 ft/sec that is adequate to maintain the solid catalyst particles in 10 suspension and to provide a mean slurry residence time in the reaction zone of from 1.5 to 15 minutes at a temperature of from 750F to 900F and separating the effluent from said reaction zone into a solid-catalyst-containing phase and a solid-catalyst-free demetallated 15 product phase.
In the process of this invention, the metal content of the feedstock is reduced by a factor of at least 5 from the original value of 20 to 2000 parts per million by weight to 0 to 40 parts per million by 20 weight.

BRIEF DESCRIPTION OF THE DRAWI~G
This invention will be further described with reference being made to the appended drawings wherein:
Fig. 1 is a graphic portrayal of the activity 25 of two hydrodemeta]lation catalysts as a function of time, Fig. 2 is a flow diagram of a hydrodemetal-lation process in accordance with the present inven-tion; and Fig. 3 is a partially cut away side vie~ of an alternate reactor configuration for use in the pro-cess of this invention.

5~L~

DET~ILED DESCRIPTION OF THE INVENTION
H drocarbon Feedstocks Y
Hydrocarbon feedstocks advantageously treated by the process of this invention contain substantial 5 quantities of metal such as from 20 to 2000 parts per million by weight of metals; preferably, 75 to 1500 parts per million by weight of metals; and more prefer-ably, 100 to 1000 parts per million by weight of m tals. The~e metals are generally present as hydro-10 carbon-feedstock-soluble organometallic compounds. The metals present are generally primarily nickel and va-nadium but may also include iron, copper, and arsenic, for e~ample. The amounts and proportions of the metals present will vary depending upon the nature of the 15 hydrocarbon feedstock. When the feedstock is a petro-leum residuum, it wil] have nickel and vanadium as its primary metal contaminants and these materials will be present in amounts of from 50 to 2000 parts per million by weight or more usually 7S to 1500 parts per million 20 by weight. When the feedstock is a shale oil, arsenic is the most common contaminant and it is present in amounts of 20 to about 200 parts per million by weight and more commonly 20 to 150 parts per million by weight.
In the primary embodiment, the feeastock employed is a petroleum atmospheric or vacuum residuum;
that is, the bottoms product of atmospheric or vacuum distillation of a crude petroleum. Such materials are characterized by containing a substantial proportion of materials boiling above 600F and substantial quan-tities (such as 0.5 to 10% by weight) of organic sul-fur. These petroleum residua employed as feedstocks may optionally have been given preliminary processing such as washing to remove salts.

$5i~0 The residuum feedstocks may be subjected to prior deasphalting treatmentO Without such treatment they may contain as much as 50~ by volume asphaltines.
When the feeAstocks have been subjected to 5 prior deasphalting treatment, for example solvent de-asphalting such as propane deasphalting, their asphal-tine content will generally be lowered to substantially less than 10% by volume often to essentially 0~. De-asphalting will not lower metal contaminant levels in the deasphalted oil to suitable levels.
Illustrative suitable feedstocks include the 600F + residuums and shale oils listed in Table I.
Table I also lists representative metal contents gen-erally observed with each feedstock materials.

TABLE I
Feedstock, and Gravity, API Meta_ content ppm by _y weight Nickel plus Vanadium Other 20 Vac.Residuum of Arabian Heavy 220 Crude Oil, 4.6 Vac.Residuum of Venezuelan Crude Oil, 10.9 666 Vac.Residuum of California Crude Oil, 5.4 294 Vac.Residuum of Iranian Heavy Crude Oil, 6.3 462 Atmospheric Residuum o~ Iranian ~eavy Crude Oil, 14.4 224 Atmospheric Residuum of Arabian Heavy Crude Oil, 11.5 124 Shale Oil I, 18.8-19.7 28 Arsenic Shale Oil II, 20.2 33 Arsenic s~o The Catalyst Employed The catalyst employed in this hydrodemetal-lation reaction is a solid particulate material. The particle size should be uniform within the range of 5 from about 50 mesh to 300 mesh, that is, the catalyst particles should uniformly pass through a 50 mesh sieve and be retained by a 300 mesh sieve. Preferably the particles are uniform in the range of from 70 to 250 mesh and most preferably are 100 to 200 mesh in size.
10 Catalyst particles within this range offer advantages of being small enough to be suspended and formed into slurries in the hydrocarbon feedstock being treated while being large enough to be completely recoverable from the treated product by conventional centrifug-15 ation, filtration or the like recovery processes.~dditionally, this particle size offers advantages of being inexpensive to form by spray drying techniques, of presenting high surface to mass ratios and of per-mitting very high metal absorption levels. Levels of as 20 much as from 50 to 150~ of the origianl catalyst weight can be observed. Moreover, catalyst particles of this size have been found to be more efficient in terms of hydrogen utilization than are the larger particLes needed in fixed bed demetallation systems.
The uni~orm mesh particles preferably are microporous. With larger particles, such as say 4 to 16 mesh pellets, there is often a need for a macro-porous structure that is not required here. Advan-tageously, the catalyst has an interna] surface area of 30 at least 100 m2/g, preferably from 200-1500 m2/g, and more preferably from 300-1200 m2/g.
Two general classes of catalysts are suitably ~mployed. The first class is comprised of supported, nonprecious heavy metal, metal-sorption catalysts made s:~

up of an inert support such as an inorganic oxidic or silicious support or activated charcoal or the like with the desired metals deposited on its surface. Such supports include for example alumina, silica-alumina, silica-magnesia, silica, horia, titania, zirconia, and activated carbon. The metals employed are members of Groups VI and VIII of the Periodic Table of the Element~ an~ include nickel, tungsten, molybdenum, cobalt and the like and mixtures thereof. Iron and vanadium are also suitable metals. The metals are gen-erally present as oxides or sulfides. Conventionally known supported hydroprocessing catalysts such as NiMo, Ni~, CoMo or CoW on alumina or silica~alumina or ac-tivated charcoal can be employed. Other examples of supported metal catalysts include NiFe, ~iCo, and NiV. The amount of metal present on the catalyst need not be large. Metal loadinss of 1~ or less based on total catalyst weight give good results. While a wider range of loadings, for example loadings of up to 10 or 15% by weight or more can be employed and are included within the scope of this invention, their use is not seen to offer advantages and to, in fact, have disad-vantages of higher cost and lower ultimate demetal-lation capacity.
The second type of catalyst useful in the present process is nonmetallic high surface area sorp-tion catalysts. Very simply, these catalysts are the supports listed above without any metals intentionally deposited on their surface. These materials are ef-fective for the demetallation reactic~n. Although not understood with certainty, it is believed that these materials operate by a self-catalysis process. They initially exhibi-t low demetallatiGn activity but after they absorb small amounts of metal their activity in-5~

_ 9 _ creases. This catalyst activity-time relationship is shown graphically in Fig. 1 wherein the rate of metal absorption from a metal-containing petroleum feedstock is plotted as a unction of time for two catalysts.
The first catalyst, Catalyst A, is a supported metal-containing catalyst. As can be seen, it has an initial high activity which gradually drops off with usage, poisoning and loading of metal from the feedstock. The second catalyst, Catalyst B, is a metal-free cata-lyst. It has a lower initial activity that grows withmetal deposition. Once a substantial loading (say 1%) is attained, this material begins to act like a pre-loaded catalyst - showing a gradual drop in activity with continued use.
Preferred catalysts for use in this invention are those microporous cataly~ts based on activated charcoal, alumina or alumina-silica with or without added metals. Such catalysts based on activated char coal are most preferred. Activated charcoal ha~ sub-stantial cost advantages. It itself is inexpensive and it permits inexpensive recovery of metals therefrom by ignition. Particularly preferred catalysts comprise activated charcoal without added metal and activated charcoal bearing up to 1% by weight of CoMo, CoW, NiW
~iMo or ~iV.

The Process Flow and Process E~uipment The flow scheme for the process of this in-vention is shown in Fig. 2 where a hydrocarbon feed~
stock, here exemplified as an Arabian heavy oil re-siduum containing 250 ppm metals and 5% by weight s~l-fur, optionally previously desalted and/or deasphalted, is fed to the hydrodemetallation unit through feed line 11 and feed pump 12. Particulate fresh catalyst is ~2~Q~S~

added to the oil feedstock stream via line 14. The catalyst is a 100-200 mesh activated charcoal having a median pore diameter of about 40 A and a surface area of 500-750 m2/g. The make-up catalyst is added in the 5 amount of about 0.0025 to 0.05 and preferably about 0.005 to about 0.0025 and most preferably about 0.01 cubic feet per barrel of oil feedstock. I'he solid catalyst is supplied by catalyst hoppers 15 and 16, one of which is blocked out and being loaded via catalyst 10 Eeed conduit 17 while the other is feeding line 14.
The hopper in use is at el~vated pressure so that the feedstock does not blcw back into it. This pressure is conveniently provided by hydrogen transmitted from hydrogen feed line 19 by catalyst hopper pressurization 15 line 20. The resulting oil-catalyst slurry passes through line 21, is admixed with about 2/3 barrel per barrel of recycle catalyst slurry supplied via line 41, to form a usually two p~ase reactor feed slurry itself made up of about 1/8 to 1/2 and especially 1/6 to 2/5 20 and preferably about 1/3 by volume solid catalyst and the remainder liqui~ oilO This equals solid to liquid feedstock volume ratios of 1:7 to 1:1, especially 1:5 to 2:3, and preferably about 1:20 This mixture is pumped through slurry pump 22, admixed with additional 25 hydrogen (to a total added hydrogen of about 250 to 1500 and especiallv about 500 SCF/barrel of oil feed-stock) supplied via line 19 to yield the required three phase solid-liquid-gas slurry, and heated to about 750 to 900F prsferably about 800F to 900F and more 30 preferably to about 825F in feed heater 24. The heatea mixture is continuously charged to elongated tubular reactor 25 via line 26 at a pressure of about 1000 to 2750 psig, and preferably from 1500 to 2500 psig. The length of reactor 25 i.s sized to provide a median slurry residence time of from about 1.5 to about 15 minutes, preferably from about 2.5 to about 10 minutes. The diameter of the tubes in reactor 25 is sized to provide a moderate slurry linear velocity such 5 as from 1.0 to 15 feet per second, and preferably 2 to 10 feet per second. Such velocities are high enough to minimize particle sedimentation but low enough to min-imize reactor wall erosion and catalyst particle de-gradation to fines. The metals in the feed are ab-10 sorbed onto the catalyst in reactor 25. As will beexemplified in FigO 3, reactor 25 may contain various static or active mixing means to promote catalyst dis-persion and hydrogen dissolution in the oil feea-stock. The demetallated product is transferred from 15 reactor 25 via line 26 to knockout pot 27 where re-siclual hydrogen is removed and taken overhead via line

2~. The amount of residual hydrogen can be small since the amount originally added generally is regulated to not grossly exceed requirements. This is done for two 20 reasons. First, to minimi~e losses and, second, to assure maximum liquid fill in the reactors. The excess hydrogen may be discarded but preferably is either recycled or used in further processing. The knockout pot bottoms product, a slurry made up of demetallated 25 oil and catalyst, is passed through line 30 to catalyst separation hydroclone 31. In hydroclone 31, a light phase made up of oil and up to about 100 parts per million by weight of catalyst is taken off via line 32 to ~ilter 34 where the residual catalyst is separated 30 leaving an essentially catalyst free demetallated (less than 20 ppm metal, usually) oil product filtrate that is taken off via line 35 usually for further hydro-processing such as hydrodesulfurization or hydro-conversion as it is Xnown in the art. The heavy ~ 3s~

product formed in hydroclone 31 is a catalyst-enriched product which is taken off via line 36 and fed to secondary hydroclone 37. In hydroclone 37, the cata-lyst enriched product is separated into a hydrocarbon-rich fraction that is recycled to line 26 via line 39,and a catalyst concentrate fraction that is taken oEf via line 41 and recycled to line 21. A portion of the cataly~t concentrate fraction is removed from line ~l through line 42, combined with the catalyst recovered in filter 3~ supplied through line 44 and passed to decant vessel 45 where from about 0.0025 to about 0.05 cubic feet of catalyst per barrel of oil feedstock is removed via line 46 optionally for disposal but prefer-ably for recovery of its metals content by means not shown. The liquid phase obtained in decant vessel 45 is recycled to feed line 11 via line 47 and recycle pump 49. Those skilled in the art will recognize tha~
the 50 - 300 mesh catalyst particle siæe enables the convenient use of a range of alternative solid/li~uid separation apparatii in the catalyst recovery schemes, including simple filters, settlers, and the like.
These may be substituted without departing rom the spirit of this invention. Similarly, when other metal-contaminated feedstocks are fed appropriate changes in operating conaitions will be made. For example, when shale oil containing 20 to 100 ppm of arsenic is fed, the reaction temperature is in the some 750 to 900 - range but pressures of 100 to 2000 psig would prefer-ably be employed and residence times of 1.5 to 5 minutes would be preferred.
Fig. 3 depicts a reactor configuration that is an alternative to the configurat.ion shown in Fig. 2.
~ eactor 50, of Fig. 3 would be inserted in the process of Fig. 2 as a replacement for reactor c~s~

25. Reactor 50 i5 fed via line 51 a slurry of metal-containing hydrocarbon oil feedstock, catalyst and hydrogen. The catalyst to oil ratio is as previously described, the hydrogen to oil ratio is lower. The slurry is passed through elongated reaction tubes 52, 52a, 52b, etc., said tubes being sized to provide the velocities and residence times set forth in the description of Fig. 2. Internal mixer 54 is shown in tube 52b. This is mounted in a manner to permit its periodic replacement when it begins to load up and restrict the slurry flow. Tubes 52, etc., are hori-zontal. In Fig. 2 a verticle tube orientation was shown. Either will work although there can be a preference for the horizontal tube placement a~ it maximizes the degree of reactor liquid fill and mini-mizes gas voids. Another help in preventing gas voids can be the use of staged hydrogen addition as shown by hydrogen inlets 55 and 55a fed by hydrogen line 56.
Staged hydrogen addition can permit the liquid's de-sired saturation with hydrogen to be maintainedthroughout the reactor without adding larye excesses in early reaction stages. The tota] hydrogen to oil fed is similar to that described with Fig. 2.
~hile a preferred embodiment o~ this inven-tion has been shown, it will be apparent to those skilled in this art that modifications may be made within the spirit and scope of this disc~osure without departing from the invention as defined by the claims.

Claims (9)

What is claimed is:

1. A process for hydrodemetallation of a liquid petroleum residuum hydrocarbon feedstock containing from 20 to 2000 ppm by weight of dissolved nickel and vanadium metals which comprises:
a. admixing said feedstock with a hydrogen source consisting of gaseous hydrogen in an amount in excess of saturation and a solid demetallation catalyst that comprises inorganic oxidic or silicious materials or activated charcoal, said catalyst characterized as being microporous, as having a surface area of at least 100 m2/g and as having a 50-300 mesh particle size in a solid-to-liquid volume ratio of 1:7 to 1:1 to form a three phase slurry;
b. passing said slurry in agitated plug-flow through an elongated horizontal tubular reaction zone sized to provide a slurry velocity of from 1 to 15 ft./sec. and a mean slurry residence time in the reaction zone of from 1.5 to 10 minutes at a temperature of from 750°F to 900°F thereby causing at least a portion of said metals to deposit upon said solid demetallation catalyst to form a demetallated hydrocarbon slurry; and c. removing said demetallated hydrocarbon slurry from said slurry reaction zone and recovering from said demetallated hydrocarbon slurry a demetallated hydrocarbon free of demetallation catalyst.

2. The process of claim 1 wherein said passing through an elongated tubular reaction zone is at a hydrogen pressure of 1000 to 2750 psig.

3. The process of claim 2 wherein said catalyst additionally comprises nonprecious metal.

4. The process of claim 3 wherein said catalyst comprises a predeposited loading of up to 1%
by weight of one or a combination of metals selected from predeposited nickel, predeposited vanadium, predeposited cobalt and predeposited tungsten.

5. The process of claim 2 wherein said catalyst comprises activated charcoal of surface area of from 200 to 1500m2/g.

6. The process of claim 5 wherein said catalyst comprises a predeposited loading of up to 1%
by weight of one or a combination of metals selected from predeposited nickel, predeposited vanadium, predeposited coablt and predeposited tungsten.

7. The process of claim 2 wherein said catalyst consists essentially of activated charcoal of surface area of 200 to 1,500 m2/g.

8. The process of claim 4 wherein said hydrogen pressure is from 1500 to 2500 psig, said temperature is from 800°F to 900°F, said mean residence time is from 2.5 to 10 minutes and said slurry velocity is from 2 to 10 ft./sec.

9. The process of claim 7 wherein said hydrogen pressure is from 1000 to 2000 psig, said temperature is from 800°F to 900°F, said mean residence time is from 1.5 to 5 minutes and said slurry velocity is from 2 to 10 ft./sec.