GB1584366A - Hydrotreating catalyst and method of its preparation - Google Patents

Description

(54) HY'DROTREATING CATALYST AND METHOD OF ITS PREPARATION (71) We, UOP INC, a corporation organized under the laws of the State of Delaware United States of America, of Ten UOP Plaza, Algonquin & Mt. Prospect Roads, Des Plaines, illinois, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment : - The present invention relates to the preparation of silica-alumina macrospheres utilising basic aluminium sulphate as the sole source of the alumina.

Silica-alumina macrospheres have heretofore been prepared utilising a basic aluminium sulphate as the sole source of the alumina portion thereof. In particular, the art discloses a method whereby a colloidal solution of a basic aluminium sulphate is dissolved in an acidic silica sol and passed through a water-immiscible solvent to form spheroidal hyrogel particles. The method is described in substantial detail in U.S.

Patent No. 3,183,194. In that procedure a basic aluminium sulphate with an So3/Al203 mole ration of from 16/1 to 08/1 is initially dissolved in a silica sol with PH in the 1-3 range. To obviate the occurrence of cracks in the final product, the hydrogel particles must be transferred from the water-immiscible solvent before softening occurs, and the hydrogel particle must then be extensively water-treated at conditions to hydrolyse the aluminium sulphate and remove sufficient sulphate to establish an SO3/AI203 mole ratio in the range of from 04/1 to 07/1. Further process steps include a relatively extensive treatment with an alkaline solution capable of effecting a gradual and uniform neutralisation of the hydrogel particles, and final alkaline wash before calcination.

This invention seeks to present an improved method of manufacturing slicaalumina macrospheres wherein a basic aluminium sulphate is sole source of alumina.

According to the invention there is provided a method of manufacturing spheroidal silica-alumina particles, which comprises forming a stable suspension of a basic aluminium sulphate in an acidic silica sol by commingling a basic aluminium sulphate characterised by an SOg/AI203 mole ratio of from 06/1 to 0 4/1 avid a particle size of from 1 to 10 microns with a silica sol characterised by a pH of from 1 to 3; dispersing the suspension as droplets in a water-immiscible, inert suspending medium which is hot (i.e. has a temperature of at least 50 C), and retaining the droplets therein until they set to firm hydrogel particles; aging the hydrogel particles in an aqueous alkaline solution for substantially complete hydrolysis of residual basic aluminium sulphate contained in them; and thereafter washing the aged hydrogel particles for the separation of sulphate from them; and drying and calcining the washed particles.

The method of the present invention permits use of a substantially less extensive water treatment of the hydrogel particles than was hitherto conventional, as well as of a substantially less extensive alkaline treatment.

The basic aluminium sulphate used as starting material for the process of this invention is characterised by an SO3/AI203 mole ratio of from 06/1 to 04/1. Such basic aluminium sulphate has heretofore been prepared by admixing an aqueous ammonium sulphate solution with an aqueous ammonium hydroxide solution at conditions to form a common solution with a pH of from 55 to 65. The basic aluminium sulphate which precipitates from the solution is a readily filterable material and, when air dried, has a particle size in the 1-10 micron range. It has been found that sufficient of the basic aluminium sulphate can be maintained as a stable suspension in the hereinafter described silica sol to provide a final silica-alumina product com prising up to 60 wt. % and more of alumina.

The aforementioned acidic silica sol is obtainable by several alternative procedures.

For example, suitable mineral acid such as hydrochloric acid, sulphuric acid, etc., is added to an equeous alkali metal silicate solution, generally an aqueous sodium silicate solution commonly referred to as water glass. Preferably, the order of addition is reversed, the water glass being added to the acid. The latter technique is preferred since the formation of the silica sol always occurs under acid conditions which preclude the premature gelation of the sol. When using sulphuric or hydrochloric acids, concentrations in the 10-30 wt. Ó range are satisfactory, and the sodium silicate solution, or water glass, is first diluted with water to establish a silica concentration in the range of from 5 to 16 wt. %. The water glass is admixed with the acid at a temperature of less than about 35"C and with agitation to inhibit polymerisation of the resulting silicic acid and premature gelation. At this stage, the silica sol will have a pH in the range of from 1 to 3, and the aforesaid basic aluminium sulphate may be commingled therewith to form a stable suspension.

Pursuant to the present invention, the suspension comprising a basic aluminium sulphate and an acidic silica sol is dispersed as droplets in a hot (i.e. at least at 50"C, e.g. at 50 to 105"C), water immiscible, inert suspending medium and the droplets retained therein until they set to firm hydrogel particles. The aforesaid method, commonly referred to as the oil-drop method, provides for the passage of the droplets through the water-immiscible, inert suspending medium-usually a light gas oil chosen principally for its high interfacial tension with respect to water. Passage of the droplets through the suspending medium produces two effects. First, as each droplet penetrates the surface it draws into a spherical shape. This is because the droplets are principally water at this stage and, being insoluble in the oil, they tend to draw into a shape resulting in the least surface area for their volume. The second effect is that the formed spheres are given time to gel and build an initial structure while gravitating to the bottom of the suspending media so that sufficient structural stability is established to resist the strains imposed by the transfer and subsequent treatment of the spheroidal particles.

In accordance with the method of this invention, the spherodical hydrogel particles are transferred from the water-immiscible suspending medium to an aqueous alkaline aging solution, suitably an aqueous ammoniacal solution. The spheres are retained in the aging solution for a period permitting substantially complete hydrolysis of their residual basic aluminium sulphate content, usually for a relatively brief period.

Preferably, the spheres are retained in the aging solution for a period of from t to 2 hours at a temperature of from 50 to 105"C. It will be appreciated that the relatively low SO3/Al2O:, mole ratio of the basic aluminium sulphate starting material will permit a substantially less tedious washing process for the separation of sulphate from the spherodical hydrogel product.

Thus, the aged spheres may be washed with an aqueous alkaline solution followed by a water-wash, suitably at room temperature, to reduce the sulphate content thereof, preferably to less than 0 5 wt. %. The spheres may be washed in any suitable manner. A particularly suitable method is to wash the spheres by percolation, either with an upward or downward flow of water, or aqueous alkaline solution as the case may be. After washing, the spheres may be dried at a temperature up to about 325"C, and then calcined at a temperature of from 425" to 750"C for 2 to 12 hours or more in an oxidising atmosphere and may then be utilised as such or composited with one or more other catalytic components.

This invention also provides catalytic composites particularly useful in the hydrotreating of petroleum fractions such as heavy atmospheric and light vacuum gas oils. Hydrotreating is an established and well-known process designed to treat a petroleum fraction or fractions in the presence of hydrogen at conditions to promote certain hydrogen-consuming reactions including hydrogenation, hydrodesulphurisation and destructive hydrogenation or hydrocracking. Catalytic hydrotreating is generally useful to improve the quality of a petroleum fraction otherwise unfit for use, or to convert higher boiling petroleum fractions to lower boiling products more useful in themselves or as a feed stock for other hydrocarbon conversion processes such as reforming. Catalytic hydrotreating is particularly useful for the destructive hydrogenation of higher boiling petroleum fractions to form lower boiling more useful products, with the sulphurous and nitrogeneous compounds typically present in said petroleum fractions being converted to readily separable hydrogen sulphide and ammonia in the process.

Hydrotreating is generally effected at reaction conditions including an imposed hydrogen pressure of from 7 8 to 205 atmospheres and an elevated temperature of from 95" to 425"C, although temperatures in the upper range, say from 315" to 425"C are more suitable. Also, a petroleum feed stock is suitably processed over the hydrotreating catalyst at a liquid hourly space velocity of from 0'5 to 20.

A catalytic composite particularly suitable for use in such a process comprises from 5 to 20 wt. % Group VIB metal or metal oxide and from 0 1 to 10 wt. % Group VIII metal or metal oxide on a silica-alumina carrier material, said carrier material having been prepared by a method according to the invention.

Thus, the catalytic composite may com pilse chromia, molybdenum, and/or tungsten in the reduced or oxidised form in combination with one or more metals or oxides of a metal of Group VIII, i.e., iron, nickel, cobalt, platinum, palladium, ruthenium, rhodium, osmium and iridium. Of the Group VIB metals, molybdenum and tungsten are preferred. Of the Group VIB metals, nickel, or nickel in combination with cobalt, is preferred. The Group VIB and the Group metal components may be composited with the carrier material in any suitable manner. For example, the silicaalumina carrier material can be soaked, dipped, suspended or otherwise immersed in a common solution comprising a suitable compound of a Group VIB metal and a suitable Group VIII metal compound.

Alternatively, a Group VIB metal and a Group VIII metal may be composited with the carrier material utilising individual solutions thereof and in any convenient sequence.

The resulting composite, after all of the catalytic components are present therein, is usually dried for a period of from 2 to 8 hours or more in a steam dryer, then from 100" to 460"C in a drying oven. The dried catalyst composite may thereafter be oxidised in an oxygen containing atmosphere, such as air, for a period of from 1 to 8 hours or more and at a temperature of from 370" to 650"C.

While it is not essential, it is preferred that the resultant calcined catalytic composite be treated in a reducing atmosphere prior to use in the conversion of hydrocarbons. The step is designed to ensure a uniform and finely divided dispersion of the catalytic components throughout the carrier material. Preferably, substantially pure and dry hydrogen is used as the reducing atmosphere in this step. The calcined catalyst is suitably treated in the reducing atmosphere at a temperature of from 425" to 650"C for a period of from 05 to 10 hours or more.

The catalyst may, in some cases, be beneficially subjected to a presulphiding operation designed to incorporate in the catalytic composite from 005 to 0-5 wt. % sulphur calculated on an elemental basis. Preferably, this presulphiding treatment takes place in the presence of hydrogen and a suitable sulphur-containing compound such as hydrogen sulphide, lower molecular weight mercaptans, organic sulphides, etc. Typically, this procedure compises treating the catalyst with a suphiding gas such as mixture of hydrogen and hydrogen sulphide having about 10 moles of hydrogen per mole of hydrogen sulphide at conditions sufficient to effect the desired incorporation of sulphur, generally including a temperature ranging from 25 to 600"C or more. It is generally a good practice to perform this presulphiding step under substantially water-free conditions.

EXAMPLE I This example demonstrates the preparation of the spheroidal silica-alumina particles according to this invention, said particles comprising silica and alumina in a 60/40 weight ratio. A basic aluminium sulphate was prepared by admixing about 500 cc of water with 3 cc of a 28% aqueous aluminium sulphate solution. The pH of the solution was then adjusted to about 6 by the addition thereto of a 15% aqueous ammonium hydroxide solution. Thereafter, the pH of the solution was maintained at this level by the concurrent addition of a 28% aqueous aluminium sulphate solution and a 15% aqueous ammonium hydroxide solution thereto, and addition being at a rate to provide about 1 7 volumes of aluminium sulphate solution per volume of ammonium hydroxide solution.

The resulting basic aluminium sulphate precipitate having a particle size of 1-10 microns was filtered, washed free of soluble sulphate, and reslurried to 13 6% A1203 equivalent concentration (7 2% Al, 5 6% SO,). About 300 grams of the basic aluminium sulphate slurry was added to 435 cc of an acidic silica sol at 7"C to form a stable suspension. The silica sol was prepared by the acidification of 315 cc of 16 wt.

% water-glass solution with 120 cc of a 20% hydrochloric acid solution and had a pH in the range 1-3. Silica-alumina hydrogel spheres were formed by the described oil-drop method at 95"C. The hydrogel spheres were aged for about l hour at 95"C in 750 cc of a 5% aqueous ammoniacal solution, washed for about 15 minutes at room temperature with 700 cc of an aqueous ammoniacal solution containing 50 cc of a 28% ammonium hydroxide solution, and finally water-washed. After three 15 minute water-washings with 750 cc of water each, the sulphate level was reduced to 0.3 wt. %.

The spheres were subsequently dried and calcined in air at 650"C for 2 hours. The silica-alumina product consisted of 03 cm.

spheres with an average bulk density of 0 60 grams per cc.

EXAMPLE II The silica-alumina carrier material (90-2 grams) from Example I was immersed in 100 cc of an aqueous impregnating solution containing 27 9 grams of ammonium metatungstate and 44 6 grams of nickelous nitrate. The solution was evaporated to dryness in contact with the carrier material utilising a steam-jacketed rotary evaporator.

After 1 hour of calcining in air at 595"C, the spheroidal catalyst product had a surface area of 232 square metres/gram, an average pore volume of 055 cubic centimetres/gram and an average pore diameter of 94 Angstroms, and analysed 8 wt. % nickel and 18 wt. % tungsten.

EXAMPLE III The charge stock utilised in this example is a blend of heavy atmospheric and light vacuum gas oils with a density of 084 gram/cc 15"C, an initial boiling point of about 270"C, and an end boiling point of about 465"C and contains 370 ppm nitrogen and 600 ppm sulphur. The charge stock is changed to a vertical tubular stainless steel reactor with an inside diameter of about 2 5 cm., preheated, and passed downflow through a 100 cc bed of the catalyst prepared as described in Example I and II at a liquid hourly space velocity of about 1, the reaction zone being maintained at an operating pressure of 137 atmospheres. The charge stock is charged with the reactor admixed with 1,700 cubic metres of recycled hydrogen per cubic metre of charge stock. The catalyst is sulphided in situ during the processing of the sulphurous charge stock. The reactor block temperature is adjusted to 406"C to produce a normally liquid product with a 200C pour point, 89 volume percent of which boiled in excess of 157"C.

WHAT WE CLAIM IS: 1. A method of manufacturing spheroidal silica-alumina particles, which comprises forming a stable suspension of a basic aluminium sulphate in an acidic silica sol by commingling a basic aluminium sulphate characterised by an SO: /Al2O3 mole ratio of from 6 6/1 to 04/1 and a particle size of from 1 to 10 microns with a silica sol characterised by a pH of from 1 to 3; dispersing the suspension as droplets in a water immiscible, inert suspending medium having a temperature of at least 50"C, and retaining the droplets therein until they set to firm hydrogel particles; aging the hydrogel particles in an aqueous alkaline solution for substantially complete hydrolysis of residual basic aluminium sulphate contained in them; thereafter washing the aged hydrogel particles for the separation of sulphate from them; and drying and calcining the washed particles.

2. A method as claimed in claim 1 wherein the basic aluminium sulphate is utilised in an amout to provide a silicaalumina product comprising up to 60 wt. % alumina.

3. A method as claimed in claim 1 or 2 wherein the aqueous alkaline solution is an aqueous ammoniacal solution.

4. A method as claimed in any of claims 1 to 3 wherein the suspension is dispersed as droplets in an oil bath maintained at a temperature of from 50 to 105 C.

5. A method as claimed in any of claims 1 to 4 wherein the hydrogel particles are aged in the aqueous alkaline solution at a temperature of from 50 to 105"C.

6. A method as claimed in any of claims 1 to 5 wherein the aged hydrogel particles are washed in equeous ammoniacal solution and then water-washed to reduce their sulphate content to less than 05 wt. %.

7. A method as claimed in any of claims 1 to 6 wherein the particles are calcined at a temperature of from 425" to 750"C in an oxidising atmosphere.

8. A method as claimed in claim 1 carried out substantially as described in the foregoing Example I.

9. Spherodial silica-alumina particles when manufactured by a method as claimed in any of claims 1 to 8.

10. A catalytic composite of from 5 to 20 wt. % Group VIB metal or metal oxide and from 0'l to 10 wt. % Group VIII metal or metal oxide on a silica-alumina carrier material, said carrier material having been prepared by a method as claimed in any of claims 1 to 8.

11. A catalytic composite as claimed in claim 10 wherein the Group VIB metal or metal oxide is tungsten or an oxide thereof.

12. A catalytic composite as claimed in claim 10 wherein the Group VIB metal or metal oxide is molybdenum or an oxide thereof.

13. A catalytic composite as claimed in any of claims 10 to 12 wherein the Group VIII metal or metal oxide is nickel or an oxide thereof.

14. A catalytic composite as claimed in any of claims 10 to 12 wherein the Group VIII metal or metal oxide is cobalt or an oxide thereof.

15. A catalytic composite as claimed in any of claims 10 to 14 containing from 005 to 05 wt. % sulphur calculated on an elemental basis.

16. A catalytic composite as claimed in claim 10 and prepared by a method substantially as hereinbefore described or illustrated in the foregoing Example II.

17. A petroleum hydrotreating process utilising a catalytic composite as claimed in any of claims 10 to 16.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (19)

**WARNING** start of CLMS field may overlap end of DESC **. grams) from Example I was immersed in 100 cc of an aqueous impregnating solution containing 27 9 grams of ammonium metatungstate and 44 6 grams of nickelous nitrate. The solution was evaporated to dryness in contact with the carrier material utilising a steam-jacketed rotary evaporator. After 1 hour of calcining in air at 595"C, the spheroidal catalyst product had a surface area of 232 square metres/gram, an average pore volume of 055 cubic centimetres/gram and an average pore diameter of 94 Angstroms, and analysed 8 wt. % nickel and 18 wt. % tungsten. EXAMPLE III The charge stock utilised in this example is a blend of heavy atmospheric and light vacuum gas oils with a density of 084 gram/cc 15"C, an initial boiling point of about 270"C, and an end boiling point of about 465"C and contains 370 ppm nitrogen and 600 ppm sulphur. The charge stock is changed to a vertical tubular stainless steel reactor with an inside diameter of about 2 5 cm., preheated, and passed downflow through a 100 cc bed of the catalyst prepared as described in Example I and II at a liquid hourly space velocity of about 1, the reaction zone being maintained at an operating pressure of 137 atmospheres. The charge stock is charged with the reactor admixed with 1,700 cubic metres of recycled hydrogen per cubic metre of charge stock. The catalyst is sulphided in situ during the processing of the sulphurous charge stock. The reactor block temperature is adjusted to 406"C to produce a normally liquid product with a 200C pour point, 89 volume percent of which boiled in excess of 157"C. WHAT WE CLAIM IS:

1. A method of manufacturing spheroidal silica-alumina particles, which comprises forming a stable suspension of a basic aluminium sulphate in an acidic silica sol by commingling a basic aluminium sulphate characterised by an SO: /Al2O3 mole ratio of from 6 6/1 to 04/1 and a particle size of from 1 to 10 microns with a silica sol characterised by a pH of from 1 to 3; dispersing the suspension as droplets in a water immiscible, inert suspending medium having a temperature of at least 50"C, and retaining the droplets therein until they set to firm hydrogel particles; aging the hydrogel particles in an aqueous alkaline solution for substantially complete hydrolysis of residual basic aluminium sulphate contained in them; thereafter washing the aged hydrogel particles for the separation of sulphate from them; and drying and calcining the washed particles.

2. A method as claimed in claim 1 wherein the basic aluminium sulphate is utilised in an amout to provide a silicaalumina product comprising up to 60 wt. % alumina.

3. A method as claimed in claim 1 or 2 wherein the aqueous alkaline solution is an aqueous ammoniacal solution.

4. A method as claimed in any of claims 1 to 3 wherein the suspension is dispersed as droplets in an oil bath maintained at a temperature of from 50 to 105 C.

5. A method as claimed in any of claims 1 to 4 wherein the hydrogel particles are aged in the aqueous alkaline solution at a temperature of from 50 to 105"C.

6. A method as claimed in any of claims 1 to 5 wherein the aged hydrogel particles are washed in equeous ammoniacal solution and then water-washed to reduce their sulphate content to less than 05 wt. %.

7. A method as claimed in any of claims 1 to 6 wherein the particles are calcined at a temperature of from 425" to 750"C in an oxidising atmosphere.

8. A method as claimed in claim 1 carried out substantially as described in the foregoing Example I.

9. Spherodial silica-alumina particles when manufactured by a method as claimed in any of claims 1 to 8.

10. A catalytic composite of from 5 to 20 wt. % Group VIB metal or metal oxide and from 0'l to 10 wt. % Group VIII metal or metal oxide on a silica-alumina carrier material, said carrier material having been prepared by a method as claimed in any of claims 1 to 8.

11. A catalytic composite as claimed in claim 10 wherein the Group VIB metal or metal oxide is tungsten or an oxide thereof.

12. A catalytic composite as claimed in claim 10 wherein the Group VIB metal or metal oxide is molybdenum or an oxide thereof.

13. A catalytic composite as claimed in any of claims 10 to 12 wherein the Group VIII metal or metal oxide is nickel or an oxide thereof.

14. A catalytic composite as claimed in any of claims 10 to 12 wherein the Group VIII metal or metal oxide is cobalt or an oxide thereof.

15. A catalytic composite as claimed in any of claims 10 to 14 containing from 005 to 05 wt. % sulphur calculated on an elemental basis.

16. A catalytic composite as claimed in claim 10 and prepared by a method substantially as hereinbefore described or illustrated in the foregoing Example II.

17. A petroleum hydrotreating process utilising a catalytic composite as claimed in any of claims 10 to 16.

18. A process as claimed in claim 17

carried out substantially as hereinbefore described or illustrated in the foregoing Example III.

19. A petroleum product when obtained by a process as claimed in claim 17 or 18.