CA1195278A

CA1195278A - Layered residua treatment catalyst process and temperature profile

Info

Publication number: CA1195278A
Application number: CA000405914A
Authority: CA
Inventors: Kirk R. Gibson; Dennis Broderick; H. Chiu Chen
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1981-09-28
Filing date: 1982-06-24
Publication date: 1985-10-15
Also published as: GB2106535A; DE3229898C2; JPS5863786A; GB2106535B; NL8203254A; BE894513A; JPH0456078B2; FR2513653B1; DE3229898A1; FR2513653A1

Abstract

ABSTRACT OF THE DISCLOSURE

LAYERED RESIDUA TREATMENT CATALYST
PROCESS AND TEMPERATURE PROFILE

A process is disclosed for the treatment of hydrocarbonaceous feedstocks having high concentrations of metals and sulfur. The feedstock is contacted with a first catalyst in a first zone and then with a second catalyst in a second zone. The average temperature of the first zone is at least 15°C more than the average tempera-ture of the second zone.

Description

01 ~1--LAYERED RESXDVA TREATMENT CATALYST
-PROCESS AND TEMPERATURE PROFILE
05 BACK~ROUND OF THE_INVENTION
This inverition relates to hydrodemetalation and hydrodesulfurization of feedstocks, particularly hydro-demetalation and hydrodesulfurization processes that use multiple beds.
The world supply of petroleum is shrinking, thereby forcing the utilization of feedstocks that are not considered to be readily refinable into lighter products.
Examples of such heavy feedstocks are Maya Crude, Arabian Heavy Crude, California San Joaquin Crude and various venezuelan Crudes. These crudes are characterized by low hydrogen to carbon ratios and high nonhydrocarbon con~ami-nant content. These contaminants include sulfur, nitrogen and metals, in particular, iron, nickel and vanadium, in the form of various soluble organometallic compounds, such as porphrins and asphaltenes.
It is preferred that sulf~r and metals be removed as early as possible in the processing of con-taminated feedstocks since both sulfur and metals tend to lessen the activity of downstream catalysts. In the case of metals, this deactivation tends to be irreversible.
Also, when burned, products that contain less contaminants tend to require less post combustion treatment to provide an environmentally acceptable exhaust.
Many processes are known to remove metals and sulfur from feedstocks. Simple distillation will remove most of the lighter hydrocarbons, and solvent extractions can remove the asphaltene fraction which contains high concentrations of sulfur and metals. ~ydroconversion processes are used extensively for desulfurization, and such processes will remove metals as well. The metals tend to deposi~ on the surface of the desulfurization catalyst, deactivating it. There has recently been great effort placed in hydrodemetalation. Catalysts have been made that remove most metals from the feedstock. Various ~ ".~

catalysts supported on alumina Eor demetalation of feedstocks are known.
United States Patent No. 3,876,523 to Rosinski et al discloses a catalyst useful for demetalation and desulfurization of residual petroleum oil, carried out with hydrogen and with an alumina base catalyst incorporating a Group VIB and a Group VIII metal. The catalyst has at least 60 percent of its pore volume in pore diameters within the range of 100 to 200 Angstroms, at least 5 percent of its pore volume is in pore diameters greater than 500 Angstroms, at least 5 percent of its pore volume is in pore diameters less than 40 Angstroms and the surface area of the catalyst is 40 to 150 meters2/gram, preferably a surface area up to abou-t 110 meters2/gram.
Ano~ther alumina demetalation catalyst is disclosed in United States Patent No. 4,257,922 to Kim et al. The catalyst support is characterized by bimodal pore distribution with the average diameter of the smaller pores ranging from about 100 to 200 Angstroms and preEerably 120 to 140 Angstroms, and average diameter of the larger pores being in excess of 1,000 Angstroms.
United States Patent No. 4,196,102 to Inooka et al discloses a catalyst for hydrotreatment of hydrocarbons comprising one or more of metals selected from the group consisting of transition metals and metals of Group IIB of the Periodic Table supported on sepiolite, a fibrous magnes:Lum silicate clay.
A variety oE multiple bed processing schemes are known to remove sulfur and metals before further processing. United States Patent No. 4,212,729 to Henslet et al discloses a two-stage catalytic process Eor hydrometalation and hydrodesulEurization of heavy hydrocarbon streams containing asphaltenes and a substantial amount of metals. The first stage o~ this process comprises contacting the feedstock in a Eirst reaction zone with hydrogen and a demetalation catalyst comprising hydrogenation metal selected from Group VIB and/or Group VIII deposed on a large-pore, ~1 -3-high surface area inorganic oxide support; the second stage of the process comprises contacting the effluent 05 from the first reaction zone with a catalyst consisting essentially of hydrogenation metal selected from Group VIB
deposited on a smaller pore, catalytically active support comprising alumina, said second stage catalyst having a surface area within the range of about 150 meters2/gram to about 300 meters2/gram, having a majority of its pore volume in pore diameters within the range of about 80 Angstroms to about 130 Angstroms, and the catalys~ has a pore volume within the range of about 0.4 cubic centimeters/gram to about 0.9 cubic centimeters/gram~
U.S. Patent No. 4,166,026 to Fukui et al dis-closes a process for hydrodesulfurization of heavy hydrocarbon oil containing asphaltenes and heavy metals.
The heavy oil is hydrotreated in a continuous two-step process. In the first step the heavy oil is subjected to hydrodemetalation and selective cracking of asphaltenes by the use of a catalyst having a unique selectivity there-for. In the second step the effluent from the flrst step is subjected to hydrodesulfurization to produce desul-furized oils of high ~rade by the use of a catalyst having a pore volume and pore size distribution particularly adapted for the hydrodesulfurization of the effluent.
It has been discovered that ln a two-stage hydrodemetalation/hydrodesulfurization catalytic process where the feedstock is first contacted with a catalyst tailored for demetalation, and then is contacted with a catalyst tailored for desulfurization, if the first catalyst zone is kept at a higher average temperature than the second zone, the product from the second zone has less contaminants and the entire system has a longer life than if both catalyst zones are kept at the same average temperature.

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~4--_ MMARY OF THE INVENTION
A process is provided for hydroconversion of hydrocarbonaceous feedstocks containing both sulfur and metals by passing the feeds-tock through multiple catalyst beds. An inverse temperature profile is maintained in the beds.
A process for removing contaminants from a feedstock containing both me-tals and sulfur is provided. The feedstock is contacted with catalysts in two zones, the first zone containing a demetalation catalyst and the second zone con-taining a desulfurization catalyst. The average temperatureof the first zone is at least 15C higher than the average temperature of the second zone.
Thus in its broadest aspect this invention provides a process for hydrotreating a hydrocarbonaceous feedstock containing both sulfur and metal comprising:
contacti.ng said feedstock with molecular hydrogen in the presence of a first catalyst having subs-tantial demetalation activity, said first catalyst being contained in a first catalytic zone, said first catalytic zone being maintained at a first average temperature and at an elevated pressure, thereby producing a first effluent;
contacting said first effluent with a molecular hydrogen quench, thereby producing a second effluent;
contacting said second effluent with a second catalyst having substantial desulfurization activity, said second catalyst being contained in a second catalytic zone, said second catalytic zone being maintained at a second average temperature, said second average temperature being at least 15C less than said first average temperature, and at an elevated pressure, thereby producing a product; and

2~78 -4a-wherein the molecular hydrogen quench produces a dif~erence in temperature between said first effluent and said second effluent which is greater than the difference between said first average temperature and said second average temperature.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphical representation of a conventional temperature profile through a reaction vessel with multiple quenches.
FIG. 2 is a graphical representation of a temperature profile of this invention.
DETAILED DESCRIPTION
The feedstocks for the present invention are hydrocarbonaceous feedstocks that contain sulfur and metal.
Frequently hydrocarbonaceous feedstocks will contain .5 percent sulfur, up to 4 percent sulfur and in extreme cases, over 6 percent sulfur, and 35 ppm metals, up to 200 ppm metals and in extreme cases, over 1,000 ppm metals. Unless specifically denoted to the contrary, as used herein, "percent sulfur," or "percent," refers to weight percent based on total elemental sulfur in the feedstock. Such feedstocks include crude oils, topped crudes, atmospheric and vacuum residua, solvent deas-phalted oil, liquids from oil shales and tar sancls and coal-derived liquids. The feedstocks of the present invention have boiling points that will frequently exceed 400F and may exceed l,000F.
The feedstock of the present invention will contact, in a first zone, a catalyst tailored for hydrodemetalation, and then will contact, in a second zone, a .;l~ ,'' 7~3 ~1 -5-catalyst tailored for desulfurization. The "first and second zonest" as used herein r refer to temperature con-05 trolled zones; that is, the first ~one will have anaverage temperature~at least 15C higher than that of the second zone~ The catalyst in the first 20ne may be the same as the catalyst in the second ~one, and each ~one may contain more than one catalyst.
The catalyst of the first zone can be any of a class of well-known and defined hydrodemetalation catalysts. Catalysts supported on alumina are known and are generally characterized by the presence of macropores, herein defined as pores larger than 1,000 Angstroms in diameter, and an average calculated micropore diamet~r of over 100 Angstroms when calculated by the formula:

Average Micropore Diameter = 4 x PV x 104 SA

where PV is micropore volume expressed in cubic centimeters/gram of catalyst where micropores are those pores of less than 1,000 Angstroms in diameter, and SA is surface area expressed in meters2/gram of catalyst.
Such catalysts may contain catalytic metals, in particular, metals from the group consisting of Group VIB
and Group VIII Transition metals of the Periodic Table of Elements, particularly, molybdenum, tungsten, nickel and cobaltO The Group VI metals may be present in quantities 3U ranging from 1.5 weight percent to 20 weight percent. The Group VIII metals may be present in quantities up to 15 percent. There may be no Group VIII metals at all on some alumina-supported hydrodemetalation catalysts.
Clay-supported demetalation catalysts may also be the catalyst of the first zone~ Such catalyst supports may be made from æepiolite, attapulgite, polygorskite, and similar fibrous magnesium silicate clays or halloysite and similar fibrous or rod-like aluminum silicate clays.

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01 ~6-These catalysts are physically characterized by large cal-culated average pore diameters, frequently over 200 05 Angstroms, and few macropores. These catalysts may con-tain catalytic meta~ls, and in particular, those selected from the group consisting of Group VI and Group VIII
Transition metals, particularly, molybdenum~ tungsten, nickel and cobalt and various combinations of these metals Any other catalyst that shows substantial hydro-demetalation activity can be used in the first zone of this invention. "Substantial hydrodemetalation activity"
- is herein defined as the ability to remove at least 25 percent of the metals content of a feedstock continuously for a period of time not less than 500 hours under hydro-processing conditions.
The catalyst of the second zone can be any cata-lyst that shows substantial hydrodesulfurization activity.
These catalysts, frequently supported on alumina or alu-mina in combination with silica, boria, titania, magnesia, or other refractory inorganic oxides, are characterized by calculated average pores diameters of greater than 50 Angstroms and few macroporesO Typical:Ly, desulfurization catalysts have more catalytic metals, giving them higher intrinsic activities. The catalytic me~als are selected from the group consisting of Group VI and ~roup VIII
Transition metals.
Any catalyst that shows substantial de~ulfuriza-tion activity can be used. "Substantial desulfurization"is herein defined as the activity required to remove at least 25 percent of the sulfur content of a feedstock for at least 500 hours under hydroprocessing conditions.
As used herein, hydroprocessing conditions are those conditions that are known to the art to give cata-lytic hydroconversion of hydrocarbonaceous feedstocks.
Typical conditions for the present invention are 355C to 450C for the first zone average temperature, and 340C to 450C for the second zone average temperature, while maintaining at least a l5~C temperature difference. Space ~ t7 Ol _7_ velocity of feedstock is between 0.1 and 1.5. Total pres-sure is between 500 and 3~000 psig, and partial pressure 05 of hydrogen is between 300 and 2,800. Recycle rate for hydrogen is between`2,000 and lO,000 SCF/BBL. Normally as the activity of the catalysts decrease, the temperature of the reaction vessels will be adjusted upward to maintain a specified quality in the product, usually a maximum toler-able amount of contaminants.
It is possible that the same catalyst might be used both` for demetalation and desulfurization. The cata-lyst charge of the first zone would tend to lose activity for desulfurization relatively rapidly, but could maintain lS demetalation activity for some time. Desulfurization reactions are believed to be reactions where sulur is hydrogenated to hydrogen sulfide and thereafter passes out of the reaction zone. Demetalation deposits metals on the outer surface or inner pore surface of the catalyst. It has been observed that a catalyst can therefore lose the property of catalytically hydrogenating sulfurl but still deposit metals.
It may be desirable to shape both the hydrode-metalation and desulfurization catalyst particles in some shape other than the conventional rouncl cylinder. ~f such shaped catalysts are used, it is preferred that the diameter of the smallest circle that can be circumscribed around the particle be 1/64 to l/2 inches~
Another embodiment of the present invention is ,having more than one catalyst in either or both of the zones. For example, a macroporous, large pore demetala-tion catalyst can be used in the first zone, at high temperature, the second zone can be charged with firstly, a large pore desulfurization catalyst that can also remove metals and then secondly, a smaller pore desulfurization catalyst that has poor metals capacity, both catalysts maintained at a temperature of at least 15C les~ than the first zone.

5~78 The present invention re~uires at least a 15C
temperature diference between the first zone and the 05 second zone. Referring to FIG. 1, the temperature profile of a conventional m~ltiple catalyst bed reaction vessel is shown. Bed 1 would be the first bed the feedstock would contact, and, in the opera~ion shown, the coolest. Three temperature zones are shown, separated by hydrogen quenches. The average temperature for each zone is de-noted by Tl ave, T2 ave and ~3 ave. At each quench point there is~a drop in temperature, for examplel Ql In this way the temperature increase of the exothermic catalytic hydrogenation reactions of each zone are controlled. In lS operation, the average temperatures of each catalyst bed tend to rise, for example, Tl ave will frequently be 10C
cooler than T2 ave. Economic operation of the reactor dictates using less quench gas than is necessary to achieve Tl ave = T2 ave. The change in temperature (~T) for any bed in commercial operation will frequently be from 10C to 20C.
FIG. 2 shows an example of the present inven-tion, a reactor containing 3 catalyst beds in which the first bed operates at ~ higher temperature than the down~
stream beds. Bed 1 is the first. catalyst bed the feed-stock contacts, but unli]ce conventionaL operation, it is the hottest bed the feedstock contacts. The change in average temperature in the operation of the present invention is at least 15C. T2 ave and T3 ave are pref-erably held closer together than typical in conventionaloperation. In FIG. 2 the first zone comprises Bed 1 and the second ~one comprises Beds 2 and 3. It will be noted that ~T ave is much greater in the operation of this invention than it is conventionally, thereby providing a second, cooler temperature zone.
The temperature profile will be observed to have several sharp drops at various points along the length of the reaction vessel. These correspond to gaseous hydrogen quenches inside the reaction vessel. For the maintenance ~5~

01 _9_ of the desired temperature profile of the present inven-tion, more hydrogen must be used at the junction of the 05 first and second bed than at any other quenching point.
It should~be appreciated that although the tem-peratures of FIG. 1 are of a single reactor, multiple temperature controlled reactors can be used. For example, guard bed reactors in separate vessels, at a temperature 15C hotter, could be substituted. The temperature of the catalyst beds generally increases during the life of the catalysts of the beds to maintain a preselected quality of productl The temperature cannot increase beyond certain limits dictated by metallurgic constraints of the reaction vessel. When the first zone, the hottest, reaches the maximum temperature which the reaction vessel can toler-ate, the temperature of that zone must be held at a constant value, allowing the temperature of the second zone to eventually equal that of the first zone. When the two zones are at the same temperature, the end of run of that catalyst charge has been reached.
Although Applicants do not wish to be bound to any particular theory of operation, it is believed that the demetalation catalyst of the first zone has contami-nation removal activity similar to the desulurizationcatalyst of the second zone, which has more metals than the demetalation catalyst, even though the demetalation catalyst has less intrinsic activity, because of the temperature differential. More metals are removed in the first zone, which does not lose activity rapidly, and the catalyst of the second zone does not lose activity for desulfuri~ation as rapidly. The total catalyst system, therefore, has longer life than otherwise would be possible.
EXAMPLE
The followiny catalysts were prepared to use in a reactor with the inverse temperature profile of the present invention. Catalyst A is prepared as follows:
Eight milliliters of 88 percent formic acid (specific gravity 1.~) was added to 300 milliliters of distilled water. This solution was added to 500 grams of Kaiser alumina at about 50°C and about 50 milliliters every minute shile mixing. The mixing continued for 20 minutes after all the solution had been added. A second solution made from 6 milliliters of 58 percent ammonium hydroxide, 45 milliliters of molydbenum solution, and 200 milliliters of distilled water was added at a rate of 50 millilters per minute while stirring. The molybdenum solution was prepared by dissolving 17.4 grams of MoO3 in 17.2 millilters of 30 percent NH4OH and 26 millilters of distilled water. The temperature during the second addi-tion was approximately 60°C. to 65°C. The doughy mixture was extruded with a trilobal fluted die and dried on a screen tray in a preheated oven at 120°C for 2 hours and then at 200°C for 2 hours. The dried extrudate was calcined at 680°C in a steam stmospher. After one hour, fresh dry air replaced the stream and the extrudate was calcined for another half an hour at 680°C.
Catalyst B is prepared according to the procedure described in U.S. Patent No. 4,113,661 issued to P. W. Tamm, September 12, 1987, entitled "Method for Preparing a Hydrodesulfurization Catalyst." An 80/20 by weight mixture of Catapal*, made by Conoco, alumina and Kaiser alumina are sized in the range below about 150 microns and treated by thoroughly admixing the mixed powders with a aqueous solution of nitric acid, were for each formula weight of the alumina (Al2O3) about 0.1 equivalent of acid is used. The treated alumina powder is in the form of a workable paste. A sample of this paste completely disperses when one part is slurried in four parts by weight of water. The pH of the slurry is in the range of about 3.8 to about 4.2, usually about 4.0 After hydroxide is thoroughy admixed into the paste in an amount equivalent to about 80 percent of the ammonium hydroxide theoretically required to completely neutralize the nitric acid; that is, about 0.08 equivalent of the hydroxide is *Trade Mark added to the paste per formula weight of the alumina present. The ammonium hydroxide used i5 desirably about an 11 percent by weight solution because the volatile material evolved during drying and cal-cination content of the treated and neutralized solids should be in the range of 50 to 70 weight percent. With the addition and thorough admixing of ammonium hydroxide, the paste changes to a free-flowing particulate solid suitable as a feed to an extruder. The extruder has a die plate that will extrude the shaped particles of -the present invention.
The extrudate precursor is freed of loosely-held water by an initial moderate drying step, for example, at a temperature in the range of 75C
to 250C. The preparation of the carrier is then completed by calcining the dried extrudate at a temperature between 250C to 800C in a dry or humi~
atmosphere, The resulting carrier has a pore volume o~ about 0.7 cubic centimeters/gram, of which at least about 85 percent is furnished by pores having a diameter in the range between about 80 and 150 Angstroms.
Less thcan about 1.0 percent of pore volume is furnished by pores larger than 1,000 Angstroms. By calcining the catalyst in a 100 percent steam atmosphere at 450C to 600C, larger pores, for example, 160 Angstroms to 190 Angstroms, may be obtained~
A ractor was charged with two layers of catalyst. The first layer and first zone was Catalyst A and the second layer and second zone was Catalyst B. An Arabian Heavy Atmospheric residue of 4.~ weight percent sulfur, 26 ppm nickel and 89 ppm vanadium was contactecl with Catalysts A and B in series. Initially, conditions were 2,200 psig, about 1,800 psig average pressure of hydrogen and about 0.35 hr 1 space velocity, with the first catalyst kept at about 1~C hotter than the second catalyst. The -temperature of the two beds was increased to maintain a constant sulfur concentration of 0.6 we:ight percent in the effluent from the second zone. At mid-run, the length oE the run possible for this system was extrapolated. End of run for this system is the metallurgical ~S2~

~1 -12-limit of the reaction vessel. The temperature difference between the first and second zone was increased to 2~C.
05 The temperature of the vessel was increased until the first zone was 427~, the metallurgical limit of the reac-tion vessel and the temperature of the first ~one was held constant as the temperature of the second zone was increased to 427C, the end of the run. The actual time of this run was about 25 percent better than the length of run estimated from mid-run extrapolations. The increase in catalyst life is believed to be a function of the larger difference in average temperature.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for hydrotreating a hydrocarbonaceous feedstock containing both sulfur and metal comprising:
contacting said feedstock with molecular hydrogen in the presence of a first catalyst having substantial demetalation activity, said first catalyst being contained in a first catalytic zone, said first catalytic zone being maintained at a first average temperature and at an elevated pressure, thereby producing a first effluent;
contacting said first effluent with a molecular hydrogen quench, thereby producing a second effluent;
contacting said second effluent with a second catalyst having substantial desulfurization activity, said second catalyst being contained in a second catalytic zone, said second catalytic zone being maintained at a second average temperature, said second average temperature being at least 15°C less than said first average temperature, and at an elevated pressure, thereby producing a product; and wherein the molecular hydrogen quench produces a difference in temperature between said first effluent and said second effluent which is greater than the difference between said first average temperature and said second average temperature.

2. The process of Claim 1 wherein said hydrodemetalation catalyst is further characterized by an alumina support having at least 5 percent of its pore volume provided by macropores and a calculated micropore diameter of at least 100 Angstroms.

3. The process of Claim 1 wherein said hydrodemetala-tion catalyst is further characterized by a support from the group consisting of fibrous magnesium silicate clays and fibrous aluminum silicate clays having at least 70 percent of its pore volume provided by pores of between 200 and 700 Angstroms.

4. The process of Claim 1 wherein said support is selected from the group consisting of sepiolite, polygorskite, attapulgite, imogolite, and halloysite.

5. The process of Claim 1 wherein said hydrodemetala-tion catalyst contains at least 1.5 weight percent Group VI
Transition metal when weight percent is determined as percent of metal to total catalyst weight.

6. The process of Claim 1 wherein said hydrodesulfuri-zation catalyst is further characterized by a support having an average calculated pore diameter of greater than 50 Angstroms, having at least 2 weight percent Group VI
Transition metal, and at least 1.5 weight percent Group VIII
Transition metal, when weight percent is calculated as percent metal to total catalyst weight.

7. The process of Claim 1 wherein said hydrodemetala-tion catalyst consists of shaped particles of between 1/64 inches and 1/2 inches in circumscribed diameter and said hydrodesulfurization catalyst consists of shaped particles between 1/64 inches and 1/2 inches in circumscribed diameter.