CA1079259A - Hydrocarbon conversion process and catalytic composite for use therein - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A catalytic composite, comprising a combination of a nickel component and a tungsten component with a silica-alumina carrier material wherein the atomic ratio of nickel to nickel plus tungsten is about 0.1 to about 0.3. The key feature of the subject composite is the criticality of the ratio of nickel to nickel plus tungsten. The principal utility of the subject composite is in the hydrocracking of hydrocarbons. A specific example of the catalyst disclosed is a combination of nickel and tungsten with a silica-alumina carrier material containing 50 wt.% alumina in amounts sufficient to result in the composite having an atomic ratio of nickel to nickel plus tungsten of 0.2.

Description

HYDROCARBON CONVERSION PROCESS AND
CATALYTIC COMPOSITE FOR USE THEREIN

The subject of the present invention is a novel catalytic composite which has exceptional activity, selectivity and resistance to deactivation when employed in a hydrocarbon conversion process. This invention also relates to the preparation of a novel catalytic composite. More particularly, the invention relates to a catalyst which is useful for per-forming destructive hydrogenation of hydrocracking of hydro-carbons.
Destructive hydrogenation by catalytic means, more commonly called hydrocracking, is old and well-known to the art. Destructive hydrogenation of the hydrocarbon oil, which is usually a coal tar or a high-boiling petroleum fraction, such as gas oils or topped crude, generally is performed at relatively high temperatures and 10'79ZS9 pressures of the order of 75ûF. or 1500 psig. and upward. Catalysts for the destructive hydrogenation of hydrocarbons are generally a com-bination of hydrogenation and cracking catalysts.
While many types of catalyst compositions have been pro-posed for destructive hydrogenation or hydrocracking, it has been fGund that catalysts comprised of silica, alumina, tungsten and nick-el are especially suitable. Such catalysts are well known in the hy-drocracking art.
From United States Patent Specification No. 3,216,922, a process is known for the preparation of hydrocracking catalysts com-prising a silica-alumina mixture as a carrier in which the carrier is obtained by first precipitating silica gel from a water glass so-lution and subsequently, after aging of the gel, precipitating alu-minum hydroxide thereon. As the aluminum salt from which the alumin-um hydroxide is formed, use is made of aluminum sulfate which is add-;~ ed in such a quantity tha-t the molar ratio of silica to alumina in - ~-the finished carrier is approximately 5:1. It was found, however, that the use of hydrocracking catalysts, of which the carrier was ob-tained in the manner described, produced less favorable results in ;,` 20 the hydrocracking of flashed distillates.
In an effort to prepare a more satisfactory hydrocracking catalyst, British Patent No. 1,183,778 teaches a process for the ` preparation of an alumina-silica-nickel-tungsten hydrocracking cata-lyst which comprises preparing a catalyst carrier by first precipita- ¦
ting from an aqueous solution comprising silicate ions, a silica gel, subjecting the gel to aging at elevated temperature, precipitating aluminum hydroxide on the aged gel by addition of an aqueous alumin-um nitrate solution and an alkaline-reacting solution, separa~ing, - . . . . . .

drying and finally calcining the resulting precipitate of aluminum hydroxide on silica gel and then supporting tungsten and nickel on the catalyst carrier and subsequently oxidizing the carrier compri-sing the metal salts.
However, because commercial scale hydrocracking of hydro-carbons is performed at low space velocities, catalyst cost is an ap-preciable factor in both the initia1 investment and operating costs~
of hydrocracking plants. For this reason, there is considerable in-cent;ve to manufacture such catalysts by the most economic method while improving the catalyst activity. We have discovered an im-proved process for the preparation of tungsten-nickel on silica-alu-mina hydrocracking catalyst.
More specifically, we have found that particular atomtc ra-tios of the nickel and tungsten components provide an exceptional catalyst for hydrogenation reaction and particularly for hydrocrack- ~ ~ ¦
ing reactions. In addition to being superior catalytically, the catalyst of the present invention is more economically produced than prior art catalysts since excessive metals levels aren't employed.
More specifically, our process is an improved process for the preparation of such catalyst wherein the atomic ratio of nickel to nickel plus tungsten is about 0.1 to about 0.3. ~he criticality of the atomic ratio is further illustrated hereinbelow.
Although any silica-alumina carrier material may suitably be used to prepare the catalyst of this invention, a particularly preferred carrier material is a co-gelled silica-alumina comprising from about 40 to about 60 percent alumina and from about 60 percent ¦~
to about 40 percent silica. It is also preferred that the carrier ¦~
material have adequate pore volume, that is, a pore volume of at 1 .

. .

lO~9Z59 least 0.5 cc/g. The co-gelled silica-alumina carrier is preferably in xerogel state, that is, it is dried sufficiently to afford the us-ual microporous structure and therefore has an appreciable available !
surface. It is also possible to use a rigid silica-alumina catalyst base which has merely been dried at a relatively low temperature, e.g. 125C., and which still contains considerable amounts of water.
In this latter case, however, the degree of drying must nevertheless be sufficient to remove essentially all water from the pores of the base.
The catalyst of the present invention can be utilized to achieve the maximum production of LPG (liquef;ed petroleum gas) in the propane/butane range from na-phtha or gasoline boiling range dis-tillates. Heavier charge stocks, including kerosenes, light gas l!
oils, heavy gas oils, full boiling range gas oils and "black oils"
may be readily converted'into lower-boiling, normally liquid prod-ucts including gasolines, kerosenes, middle-distillates, lube oils, etc.
In one embodiment, accordingly, the present invention pro- - ' vides a method of preparing catalysts having hydrocracking activity I!
comprising a method for the preparation of catalyst having hydro- ¦
cracking activity comprising impregnating a silica-alumina carrier material with an aqueous solution of a nickel salt and a tungsten salt, the concentration of the salts in the aqueous solution being selected to deposit on the carrier material an atomic ratio of nick-el to nickel plus tungsten of about 0.1 to about 0.3 In a second embodiment, the present invention relates to a process for hydrocracking hydrocarbons which process comprises re-acting said hydrocarbons with hydrogen in a reaction zone containing .
a catalytic composite prepared by a method comprising a method for the preparation of catalyst having hydrocracking activity comprising impregnating a silica-alumina carrier material with an aqueous solu- - ¦
tion of a nickel salt and a tungsten salt, the concentration of the salts in the aqueous solution being selected to deposit on the car-rier material an atomic ratio of nickel to nickel plus tungsten of about 0.1 to about 0.3.
In a specific embodiment, the hydrocracking conditions in-clude a maximum catalyst bed temperature of about 600F. to about 900F., a pressure of about 500 to about 5000 psig., a liquid houriy space velocity of about 0.1 to about 10 and a hydrogen circulation rate in the range of about l,OOO to about 50,000 scf/bbl.
In another specific embodiment, the catalytic composite is oxidized, in an atmosphere of air, at a temperature about 1000F.
i ~ lS prior to contact with the fresh feed charge stock. -Another embodiment relates to a catalytic composite, com-` prising a combination of a nickel component and a tungsten component with a silica-alumina carrier material wherein the atomic ratio of nickel to nickel plus tungsten is about 0.1 to about 0.3.
Other objects and embodiments of our invention relate to additional details regarding the preferred catalytic ingredients, .
the concentration of components within the catalytic composite, the method of catalyst preparation, preferred processing techniques and similar particulars which are hereinafter set forth.
Catalytic composites, tailored for the conversion of hydro- -carbonaceous material and particularly those intended for utiliza-tion in a hydrocracking process, have traditionally consisted of me-tallic elements chosen from Group VIII of the Periodic Table; how-.

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ever, metallic components from Group VI-B are quite Gften incorpora-ted therein. In those instances where hydrocracking is intended to be accompanied by some hydrorefining (desulfurization, denitrifica-tion, etc.) the preferred metallic components have been nickel and molybdenum, and nickel and tungsten, which components are usually combined with a porous carrier material comprising both alumina and silica, either amorphous or zeolitic in nature. Ample evidence may be found in the litera~ure which confirms the ability of nickel com-ponent to effect both cracking and hydrogenation reactions. Further-more, the prior art indicates a preference for two particular meth-ods of catalyst preparation. Predominantly preferred is an impregna-ting procedure wherein a previously calcined, preFormed carrier mate-rial, which is precipitated in a multi-step manner as hereinabove de-scribed, is contacted with suitable solu~le compounds of the nickel 1~ component and the Group VI-B component, where the latter is utilized.
Impregnation involves both subsequent drying at a temperature of about 300F., and oxidation at a temperature of about 1100F. The second preferred preparation scheme involves coprecipitating all the catalyst components, including those of the carrier material. Parti~
cularly effective silica-alumina-nickel-tungsten hydrocracking cata-lyst can be prepared when the alumina content of the co-gelled sili-ca-alumina support is maintained within the range of from about 43 percent to about 57 percent by weight alumina.
As is customary in the art of catalysis, when referring to the catalytically active metal, or metals, it is intended to encom-pass the existence of such metal in the elemental state or in some form such as an oxide, sulfide, halide, etc. Regardless of the state in which the metallic components actually exist, the concentrations _~

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lO';'9Z59 are computed as if they existed in the elemental state.
The co-gelled silica-alumina or any other form of sil;ca-alumina carrier material may be prepared and utilized as spheres, pills, pellets, extrudates, granules, etc. In a preferred ~ethod of manufacture for co-gelled silica-alumina, an aqueous water glass so-lution, diluted to a silica concentration of from about 5 to about 15 weight percent, is acidified with hydrochloric acid or other suit-able mineral acid. The resulting sol is acid aged at a pH of from about 4 to about 4.8 to form a hydrogel, and the hydrogel is further aged at a pH of from about 6.5 to about-7.5. The silica hydrogel is then thoroughly admixed with an aqueous aluminum salt solution of sufficient concentration to provide a desirable alumina content in the silica-alumina product. The silica-alumina sol is then precipi-tated at a pH of about 8 by ~he additlon of a basic precipitating agent, suitably aqueous ammonium hydroxide. The silica-alumina, ! . - . - -.c -- - I ` . : .
which exists as a hydrogel slurried in a mother liquor, is recovered by filtration, water-washed and dried at a temperature of from about 200F. to about 500F. Drying is preferably by spray-drying tech-niques whereby the co-gelled silica-alumina is recovered as micro-spheres, admixed with a suitable binding agent, such as graphite, polyvinyl alcohol, etc., and extruded or otherwise compressed into pills or pellets of uniform size and shape.
~! A particularly preferred method for preparing co-gelled ` silica-alumina support is by the well-known oil-drop method which permits the utilization of the support in the form of macrospheres.
For example, an alumina sol, utilized as an alumina source, is com-mingled with an acidified water glass solutiGn as a silica source, and the mixture further commingled with a suitable gelling agent, 1 .
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l~i for example, urea, hexamethylenetetramine, or mixt~res thereo-f. The mix-ture is discharged while still below gellation temperature, and by means of a nozzle or rotating disk, into a hot oil bath maintained at gella-tion temperature. The mixture is dispersed into the oil bath as drop-lets which form into spheroidal gel particles during passage therethrough.
The alumina sol is preferably prepared by a method wherein aluminum pel-lets are commingled with a quantity of treated or deionized water, with hydrochloric acid being added thereto in a sufficient amount to digèst a portion of the aluminum metal and form the desired sol. A suitable re-action rate is effected at about reflux-temperature of the mixture.
- The spheroidal gel particles prepared by the oil-drop method are aged, usually in the oil bath, for a period of at least 10-16 hours, and then in a suitable alkaline or basic medium for at leas~ 3 to about 10 hours, and finally water-washed. Proper gellation of the mixture in the oil bath, as well as subsequent aging of the gel sphere~, is not readily aceomplished below about 120~F., and at about 210F.~ the rapid evolution of the gases tend to rupture and otherwise weaken the spheres.
By maintaining sufficient superatmospheric pressure during the forming and aging steps in order to maintain water in the liquid phase, a higher temperature can be employed, frequently with improved results. If the - gel particles are aged at superatmospheric pressure, no alkaline aging step is required. I
The spheres are water-washed, preferably with water containing ; a small amount of ammonium hydroxide and/or ammonium nitrate. After wash-ing, the spheres are dried, at a temperature of from about 200~F. to about 600F. for a period of from about 6 to about 24 hours or more, and then calcined at a temperature of from about 800F. to about 1400F. for a period of from 2 to about 12 hours or more.
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` 1079Z59 The nickel component and the tungsten component are composed with the co-gelled silica-alumina carrier material by any suitable co- `
impregnation technique. Thus, the carrier material can be soaked, dip-ped, suspended, or otherwise immersed in an aqueous impregnating solu-tion containing a soluble nickel salt and a soluble tungsten salt. One suitable method comprises immersing the carrier material in the impreg-nating solution and evaporating the same to dryness in a rotary steam dryer, the concentration of the impregnating solution being such as to ensure a final catalyst composite comprising an atomic ratio of nickel to nickel plus tungsten of about 0.1 to about 0.3. Another suitable method comprises dipping the carrier material into the aqueous impreg-nating solution at room temperature until complete penetrat;on of car-rier by the solution is achieved. After absorption of the impregnating i solution, the carrier is drained of free surface liquid and dried in a moving belt calciner.
The catalyst composite is usally dried at a temperature of from about 200F. to abou~ 500-F. for a period of from about 1 to about 10 hours prior to calcination. In accordance with the present invention, calcination is effected in an oxidizing atmosphere at a temperature of ~
from about 700 to about 1200-F. The oxidizing atmosphere is suitably ¦~ -air, although other gases comprising molecular oxygen may be employed. -¦~
Following the high temperature oxidation procedure, the cata-lyst is usually reduced for a period of from about 1~2 to about 10 hours at a temperature in the range of from about 700~F. to about lOOO~F. in the presence of hydrogen. The catalyst may be used in a sulfide form.
Thus after reduction, the catalyst may be subjected to sulfidation by I
passing hydrogen sulfide, or other suitable sulfur containing compound, ¦¦
in contact therewith, pre~erably at an elevated temperature oi from about I, .. . .

5~0F. to about 1100F. The reduced catalyst is preferably sul-fided by contacting the catalyst with a stream of hydrogen containing from about 1 to 20 percent or more by volume of hydrogen sulfide at elevated tem-perature of from about 500F. to about 1100F. When the petroleum hy-drocarbon to be hydrocracked contains sulfur compounds, by design or `
otherwise, sulfidation may be suitably effected in situ in the initial stages of the hydrocracking process. ~
The catalyst composite, prepared in acçordance with the mèthod - ll of this invention, is preferably employed in a reaction zone as a fixed ~!
bed. The hydrocarbon charge stock after being combined with-hydrogen in an amount of from about 2000 to about 20,000 standard cubic feet per bar-rel, and preferably at least about 5000 standard cubic feet per barrel, is introduced into the reaction zone. The charge stock may be in a liq-uid, vapor, or liquid-vapor phase mixture, depending upon the tempera-t 15 ture, pressure, proportion of hydrogen and the boiling range of the charge ' stock being processed. The liquid hourly space velocity through the re- - - - i action zone will be in excess of about 0.2 and generally in the range of from about 1.0 to about 15Ø The source of hydrogen being admixed with a hydrocarbon charge stock may comprise a hydrogen-rich gas stream which is withdrawn from a high-pressure, low-temperature separation zone and recycled to supply at least a portion of such hydrogen. Ex¢ess hydrogen resulting from the various dehydrogenation reactions effected in a cata-lytic reforming unit may also be employed in admixture with the hydrocar-bon charge. The reaction zone will operate under an imposed pressure - within the range of from about 80 to about 3000 pounds per sguare inch gauge. The catalyst bed inlet temperature is maintained within the range of from about 350 to about 800~. Since the hydrocracl~ing reactions are exothermic, the outlet temperature or the temperature at the bottom of .
- . : . .

- 1~79Z59 ,~

the catalyst bed will be significantly higher than that at the inlet there- '~
to. The degree of exothermicity exhibited by the temperature rise across the catalyst bed is at least partially dependent upon the character of ¦
the charge stock passing therethrough, the rate at which the normally liq-uid hydrocarbon charge contacts the catalyst bed, the intended degree of converslon to lower-boiling-hydrocarbon products, etc. In any event, the catalyst bed inlet temperature will be such that the exothermicity o~ the reactions taking place does not cause the temperature at the outlet of the bed to exceed about 900F., and preferably 850rF. The operation may also be effected as a moving-bed type of operation in which the catalyst, hydrocarbon and hydrogen are admixed and passed as a slurry through the reaction zone.
Although the method of preparing the catalyst, and careful se-lection of operating conditions within the ranges hereinbefore set forth, -, 15 extend the effective life of the catalyst composite, regeneration thereof .
may eventually become desired due to the natural detérioration of the - - `
catalytically active metallic components. The catalytic composite is readily regenerated by treating the same in an oxidizing atmosphere, at a temperature of from about 750 to about 850F., and burning coke and other heavy hydrocarbonaceous material therefrom. The catalyst composite may then be subjected to the reducing action in hydrogen, i~ situ, at a temperature within the range of from about 1000 to about 1200F. If desirable, the catalyst may then be sulfided in the same manner as fresh ; catalyst as hereinbefore described.
Z5 The drawing included ln the ;nstant application is for the pur-pose of visually demonstrating the improvements and advantages afforded by the manufacture of silica-alumina-nickel-~ungsten hydrocracking cata-lyst according to the present invention.

L0~9Z59 The following example is presented in illustration of the cata-lyst of this invention and a method of preparation thereof, and is not intended as an undue limitation on the generally broad scope of the in- ' vention as set out in the appended claims.
EXAMPLE `
This example describes the preparation and testing of eight silica-alumina-nickel-tungsten catalysts each having an atomic ratio of nickel to nickel plus tungsten in the range from 0.1 to 0.55. The sup-port material for each catalyst was co-gelled silica-alumina prepared by the hereinabove described o;l drop method. The finished support ma terial was in the form of 1/16" spheres and contained 50% alumina., Eight batches of co-gelled support material with the herein-above described characterist;cs were,;mpregnated with an aqueous solu-tion of nickel nitrate and ammonium metatungstate. Each batch was im-pregnated with a solution prepared to yield the desired nickel-tungsten atomic ratio in the finished catalyst. The impregnated spheres were dried and then oxidized at a temperature of llO0-F. The eight batches of finished catalyst are hereinafter referred to as Catalyst 1 through 8 and are characterized by having an atomic rat;o of nickel to nickel plus tungsten of'0.55, 0.45, 0.33,,0.23, 0.21, 0.20, 0.18 and 0.10, re- I
spectively. ' Il¦
Each of the catalysts prepared in this manner were then used !
in the hydrocracking of a vacuum gas oil whose properties are summarized in Table I.
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~LI~'7 9 Z 5 9 TABLE I PROPERTIES OF VACUUM GAS OIL
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API Gravity at 60F. 19.8 Specific Gravity at 60F. 0.9352 Distillation, F.

~o 830 I
890 !1 Total Sulfur, wt.% 2.79 Total Nitrogen, wt.% 0.16 The standard relative activity test procedure is conducted by processing the hereinabove described gas oil at 1500 psig, a maximum catalyst bed 1, temperature of 775F. and in the presence of 7500 scf./Bbl. of hydrogen.
For each catalyst? three test periods of approximately eight hours dura-~ tion were effected at liquid hourly space velocities which vary from ; about 1.0 to about 4Ø The normally liquid product effluent from each of the test periods is subjected to distillation to determine the quan- ¦
tity of hydrocarbons boiling below a temperature of 650-F., and these three percen~ages are plotted against the space velocities employed.
The relative activity is determined by the ratio of the liquid hourly space velocity required to produce a product effluent of which 60X by volume is distillable at a temperature of 650F., and comparing this liq-. uid hourly space velocity with that of the standard catalyst. With re-spect to any given test catalyst, a relative activity coefficient or fac-I tor greater than 100 indicates a catalyst having greater degree of hydro-cracking activity than the standard reference catalyst.
Each of the eight batches of finished catalyst were tested ac- ' cording to the hereinbefore described standard relative activity test !!

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procedure and the data are presented in tabular form in Table II and in graphical form in the accompanying drawing. ~l TABLE II
EVALUATION FOR HYDROCRACKING ACTIVITY
ATOMIC RATIO, CATALYST Ni CATALYST
IDENTITY Ni + W ACTIVITY
~ 0.55 136

2 0 45 140

3 0 33 149 `

4 0,23 152

- 5 0.21 162

6 0.20 163

7 0.18 154

8 0.10 151 From the data presen~ed in foregoing Table I and with reference to the accompanying drawing, it will be seen that the silica-alumina-nick-el-tungsten catalysts with an atomic ratio from about 0.1 ta about 0.3 exhibit superior hydrocracking activity. Datum points 1 through 8 in the ~ 20 drawing are representative of the results obtained with catàiysts 1 through 8, respectively. These data were employed in preparing curve 9 of the drawing, which curve clearly illustrates the criticality attached to an atomic ratio within the range of about 0.1 to about 0.3, in order to maxi- -mize hydrocracking activity. The additional economic advantages afforded l through this particular result will be readily recognized by those pos- ¦-sessing skill within the art of petroleum refinery processes. i The foregoing specification and example clearly illustrate the improvements encompassed by the present invention and the benefits to be afforded a process for the production of lower boiling hydrocarbon products.

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Claims (10)

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

1. A method for the preparation of catalyst having hydrocracking activity comprising impregnating a silica-alumina carrier material with an aqueous solution of a nickel salt and a tungsten salt, the concentration of the salts in the aqueous solution being selected to deposit on the carrier material an atomic ratio of nickel to nickel plus tungsten of about 0.1 to about 0.3.

2. The method of claim 1 further characterized in that said atomic ratio is from about 0.15 to 0.25.

3. The method of claim 1 further characterized in that said nickel salt is nickel nitrate.

4. The method of claim 1 further characterized in that said tungsten salt is ammonium metatungstate.

5. The method of claim 1 further characterized in that the total elemental weight of tungsten and nickel is from about 1% to about 25 wt. % of the finished catalyst.

6. The method of claim 1 further characterized in that said silica-alumina carrier material is 1/16" diameter spherical particles.

7. A catalytic composite comprising a combination of a nickel component, and a tungsten component with a silica-alumina carrier material wherein the atomic ratio of nickel to nickel plus tungsten is about 0.1 to about 0.3.

8. A catalytic composite as defined in claim 7 wherein said composite contains, on an elemental basis, about 1 to about 25 wt. % of tungsten and nickel.

9. A catalytic composite comprising a combination of the catalyst composite of claim 7 with a sulfur component in amounts sufficient to incorporate about 0.05 to about 1 wt.%
sulfur, calculated on an elemental basis.

10. A process for the hydrocracking of a hydrocarbon oil comprising contacting the hydrocarbon oil under hydrocracking conditions at an elevated temperature and pressure with the hydrocracking catalyst as defined in claim 7, 8 or 9.