US3182012A

US3182012A - Catalytic hydrocracking

Info

Publication number: US3182012A
Application number: US760646A
Authority: US
Inventors: Lewis M Browning; Carl W Streed
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1958-09-12
Filing date: 1958-09-12
Publication date: 1965-05-04
Anticipated expiration: 1982-05-04
Also published as: DE1121756B; FR1238968A

Description

i. May 4 1955 L.. M. BRowNlNG ETAL 3,132,012

v V CATALYTIC HYDROCRACKING I Filed Sept. 12, 1958 2 Sheets-Sheet 1' ol.."/ com/Saale urliy lo l o en ycA coN-u-EN'x-,w-r/o NVENTORS ATTORNEY United States Patent O 3,182,012 CATALYHC HYDRCRACKING Lewis M. Browning, Needham, Mass., and Carl W. Streed, Sewell, NJ., assignors to Socony Mobil Oil Company, Inc., a corporation of New York Filed Sept. 12, 1958, Ser. No. 760,646 8 Ciaims. (Cl. 208-111) This invention relates to an improved hydrocarbon conversion catalyst characterized by a predominant proportion of alumina and specied minor proportions of molybdena, silica, and cobalt oxide combined in a particular manner. The invention is further directed to a process wherein a high boiling hydrocarbon or hydrocarbon mixture, for example, a petroleum fraction, is subjected to cracking in the presence of hydrogen and the aforementioned catalyst.

As is Well known, cracking refers generally to operations wherein a long chain hydrocarbon or a mixture of high molecular weight hydrocarbons is converted into a shorter chain hydrocarbon or into a mixture of lower molecular weight hydrocarbons. Cracking` accomplished solely as a result of the high operational temperature employed is known as thermal cracking while cracking effected in the presence of catalyst is ordinarily known as catalytic cracking. Cracking carried out in the presence of hydrogen is referred to as hydrocracking.

Catalytic cracking lof petroleum hydrocarbons has heretofore been carried out at temperatures in the range of 800 F. to ll00 F. Such high temperatures have been ineicient from an economics standpoint and undesirable from an operational standpoint, resulting in the production of unwanted coke, relatively large amounts of dry gas, and excess quantities -of C4 hydrocarbons. The production of coke and dry gas represents a loss, thereby bringing about an overall decrease in the yield of useful cracked product.

As is well known, charge stocks heretofore employed in catalytic cracking operations have been selected petroleum stocks. Thus, heavy residual stocks, as well as cycle stocks obtained from the catalytic cracking of non-refractory petroleum cracking stocks, have not been suitable for catalytic cracking processes because of their inherent cokeforming characteristics and the excessive amounts of dry gas produced. Accordingly, the supply of available cracking stocks has been somewhat restricted.

Cracking operations carried out in the presence of hydrogen at relatively high temperatures and under high pressure, i.e. hydrocracking, do not impose the aforesaid limitation-s on the type of utilizable charge stock. Thus, cycle stocks, heavy residuals, etc. can be cracked in hydrocracking operations. Conventional operations of this type, however, have many disadvantages. Thus, in order to maintain catalyst activity at a desired level and to avoid a heavy deposition of coke on the catalyst, it has been necessary to employ excessively high hydrogen pressures of the order of at least about 3500 pounds per square inch and preferably much higher.

There is accordingly, at the present time, great interest in the petroleum industry in developing a moderate pressure hydrocracking process. This interest arises from the ability of hydrocracking to substantially increase both the quantity and quality of naphtha and fuel oil that a petroleum reiinery can produce from crude oil. These advantages have been amply demonstrated by the aforementioned high-pressure hydrocracking operations. The high cost of high-pressure hydrocracking, necessitating the use of Vexpensive high-pressure equipment, has prevented its wide spread use, hence the interest in developing a less expensive, moderate-pressure process which will retain many of the demonstrated advantages, but at acceptable cost.

In accordance with the present invention, it has been discovered that cracking of hydrocarbons in the presence of hydrogen and a particular catalyst permits the use of appreciably lower reaction temperatures and pressures. Thus, it has been found that cracking of hydrocarbons can be effected in the presence of hydrogen and in the presence of a catalyst consisting essentially of alumina, silica and the oxides of molybdenum and cobalt combined in such manner that the resulting composite is characterized by a silica content of about l5 to about 40 percent by weight, a molybdenum trioxide content of about 3 to about 20 percent by weight, a cobalt oxide content of about 1 to about 8 percent by weight and the remainder alumina. Preferably the catalyst has a composition of about l5 to about 25 weight percent silica, about 7 to about 16 weight percent molybdenum trioxide, about 2 and about 4.5 percent cobalt `oxide and the remainder alumina. Such catalyst employed in the process of the invention has been found to alord a highly favorable distribution of products of high quality. The process described herein has the further advantage of being applicable for catalytically hydrocracking a wide Variety of charge stocks, including heavy residual and refractory charge stocks.

The present invention provides a process for cracking hydrocarbons and particularly petroleum hydrocarbon fractions having an initial boiling point of at least about 400 F., a 50 percent point of at least about 500 F. and an end boiling point of at least 600 F. and boiling substantially continuously between said initial boiling point and said end boiling point by contacting said fractions with the above catalyst in the presence of hydrogen at a hydrogen partial pressure between about 700 and about 3000 pounds per square inch gauge at a liquid hourly space velocity of between about 0.1 and about l0 at a temperature between about 600 F. and about 950 F., employing a molar ratio of hydrogen to hydrocarbon charge between about 2 and about 80.

We are aware that it has heretofore been proposed to desulfurize hydrocarbon fractions in the presence of certain catalytic composites containing alumina, silica, cobalt oxide and molybdena. The hydrocracking process described herein is distinguishable from such desulfurizing processes. Thus, there are at least four diiferences between the cracking process of this invention and the aforesaid desulfurizing operations. First of all, it may be noted that the processes are carried out for two different purposes. Cracking is used to convert high boiling hydrocarbon fractions into low boiling hydrocarbon fractions, while desulturizing is carried out for the sole purpose of removing sulfur from the charge stock undergoing treatment. Secondly, the silica content of the above type catalysts useful in desulfurization is substantially lower than the silica content of the catalysts employed in the present hydrocracking process. A third diiference relates to the chemical reactions involved in the processes. In desulfurizing, it is desired to remove sulfur from a hydrocarbon by reaction of the sulfur compounds with hydrogen with resulting formation of HZS. Cracking, on the other hand, involves conversion of high boiling hydrocarbons to lower boiling hydrocarbons by selective breakage of carbon to carbon bonds. A still further distinction resides in the fact that the hydrocracking process of this invention is generally carried out at pressures outside the range specitied for desulfurization. It will accordingly be appreciated that the aforementioned desulturizing processes utilizing catalysts containing alumina, silica, molybdena and cobalt oxide are distinct from the hydrocracking process of this invention.

Catalysts proposed for hydrocracking operations have, heretofore, consisted almost entirely, of active hydrogenating components dispersed on an existing active cracking base such as platinum on silica-alumina, molybdena on silica-alumina or of supported metal oxides or suliides that have, to varying degrees, both hydrogenating and cracking activity such as nickel sulfide on alumina, tungsten disulfide on clay and the like. Neither'of the above type catalysts has proven satisfactory for moderate pressure hydrocracking. When tested these catalysts have shown a lack in one or more of the following: the ability to retain activity during use; a good balance between cracking and hydrogenating activities; or the recovery of activity when carbonaceous deposits are removed after a period of use.

Following the teachings of this invention, it has been found that highly effective catalysts for use in moderate pressure hydrocracking can be obtained by intimately compositing the oxides of aluminum, cobalt, molybdenum and silicon in particularly specified proportion. T he catalysts of this invention have been found to be capable of affording unexpected performance in hydrocracking petroleum fractions at moderate pressures, i.e. generally not in excess of a hydrogen partial pressure of about 3000 pounds per square inch.

The catalyst components of silica, alumina, cobalt oxide and molybdenum trioxide may be combined in any suitable manner. It has been discovered, however, as will be evident from data set forth hereinbelow, that it is preferable to produce the catalyst by mechanical admixture of the silica and alumina-containing components, rather than by chemical compositing of these oxides such as, for example, by cogelation. Either the silica or alumina-containing component may prior to adrnixture with the other have deposited thereon one or both of the other catalyst components, i.e. cobalt oxide and/or molybdenum trioxide. Thus, the catalyst of the invention may be produced by mechanically admixing silica with alumina which has previously been impregnated with the oxides of molyb denum and cobalt. Alternatively, the catalyst may result from mechanical admixture of alumina with silica which has previously been impregnated with the oxides of molybdenum and cobalt. Another method of combining the catalyst components involves admixture of silica impregnated with either molybdenum trioxide or cobalt oxide with alumina impregnated with the other of such metal oxides. It is also feasible, and in some aspects preferable, to initially intimately admix the silica and alumina components and thereafter to impregnate the resulting silicaalumina composite with the oxides of molybdenum and cobalt. The composite obtained, in accordance with any of the above techniques, is dried and calcined to obtain the finished catalyst.

While the alumina component is the predominating constituent of the present catalyst and has, of itself, no hydrocracking activity, its careful preparation is essential to the production of the catalyst affording the desired activity in the contemplated conversion of the hydrocarbon charge. The alumina when properly prepared exerts a synergistic effect with the other catalyst components.

The alumina component of the present catalyst is a porous alumina not adversely affected by the temperature conditions of the instant process, having a surface area greater than 100 square meters per gram and which may extend up to 500 square meters per gram or more. Catalysts prepared from alumina having a surface area of 100 square meters per gram or less have a considerably higher aging rate when employed in the instant low pressure hydrocracking process in comparison to catalysts in which the alumina component initially is characterized by a surface area in substantial excess of i() square meters per gram. The term surface area as used herein designates the surface area as determined by the adsorption of nitrogen according to the method of Brunnauer et al. Journal Americal Chemical Society 60, 309 et seq. (1938). As noted above, the alumina itself, is devoid of or exerts negligible catalytic activity under the reaction conditions at which the present hydrocracking process is carried out. The density of the alumina employed, i.e. the bulk density thereof, will usually be within the range of .2 to 2.0 grams/cc. and more particularly between about 0.4 and about 1.2 grams/ cc.

The alumina component of the present catalyst may be prepared by commingling a suitable basic compound including ammonium hydroxide, ammonium carbonate, ete. with an acidic compound of aluminum including the chloride, bromide, iodide, fluoride, sulfate, phosphate, nitrate, acetate, etc. or by the addition of a suitable acidic compound including hydrogen chloride, sulphuric acid, phosphoric acid, etc. to an alkaline compound of the metal as for example, an alkali metal aluminate such as sodium aluminate. The resultant aluminum hydroxide is usually washed to remove soluble impurities and then is dried at a temperature of from 200 F. to about 600 F. for a period of from 1 to 24 hours or more. In one method the dried alumina is formed into particles of denite size and shape in any suitable manner such as casting, pelleting, extruding, etc. and then is subjected to calcination at a temperature of from about 600 to about 1600 F. in another embodiment the alumina may be formed into particles of spherical shape by dropping a suitable alumina sol into a suitable medium which may comprise air, an inert atmosphere, as for example nitrogen, carbon monoxide, etc. or into an oil or other suitable immiscible liquid. The resultant spheroids are then washed, dried and calcined in the manner hereinbefore set forth. Alternatively, the alumina may be prepared in the form of a precipitate by controlled reaction of aluminum metal with water in the presence of a mercury compound whereby the aluminum undergoes amalgamation and the resulting amalgamated aluminum reacts with the Water to form alumina.

The silica component is initially prepared in the form of a hydogel or gelatinous precipitate. Preferably, the silica component is prepared in the form of a hydrogel by reaction between sodium silicate and an acid, such as sulfuric acid, while maintaining the pH of the reaction mixture generally below about 6 and preferably in the approximate range of 3.5 to 5. The initially formed hydrosol of silica undergoes gelation after lapse of a suitable period of time to silica hydrogel. The time of gelation can be controlled within desired limits by well known means such as adjustment in the temperature or solids concentration of the reaction mixture or hydrosol produced therefrom. The resulting hydrogel is thereafter water-washed, base-exchanged to remove zeolitic sodium and dried. if it is desired to prepare silica initially free of alkali metal ions, such may be accomplished by effecting hydrolysis of alkyl silicates, i.e. ethyl silicate. The silica hydrogel may be produced in the form of granules or in the form of a mass, which is thereafter broken up into pieces or particles of desired size. Alternatively, the silica hydrogel may be produced in the form of spheroidal bead particles by methods such as those described by Marisic in U.S. 2,384,946, or in the form of uniformly shaped particles prepared by casting or extrusion methods. It is also feasible to initially produce silica in the form of finely divided particles of requisite particle size by employing techniques used in the preparation of fiuid catalyst particles, for example, by spraying or rapid agitation of a hydrosol to form minute particles of hydrosol that set to particles of hydrogel, which, upon drying yield discrete particles of silica gel. Generally, it is preferred that the silica component before admixture with the alumina-containing component be in a finely divided state, generally of a particle size finer than 50 mesh (Tyler) and preferably of a particle size within the approximate range of 60 to 200 mesh (Tyler). The above indicated finely divided state of silica can be obtained either during initial formation of the silica or by grinding larger size pieces to the requsite particle size.

The alumina and silica, prepared as above, may be composited by mechanical admixture and thereafter impregnated with cobalt oxide and molybdenum trioxide; or either of these components, prior to admixture with the other, may be impregnated with suitable compounds of molybdenum and cobalt to effect deposition thereon of cobalt oxide and molybdenum trioxide. The base material, i.e., alumina, silica, or composite resulting from admixture of silica and alumina is contacted with an impregnating solution of a cobalt compound, such as cobalt nitrate, and of a molybdenum compound, such as ammonium molybdate. In one method, the particles of base material are initially subjected to a vacuum to remove air from the pores thereof and while maintaining the vacuum, the above-described impregnating solution is brought into contact with the particles of base material. Alternatively, the base material, for example, in the form of an Iaqueous slurry may be impregnated With the solution of molybdenum compound and cobalt compound. It is understood that any other suitable method of commingling particles of the base material With the impregnating solution may be employed.

In another embodiment, separate impregnating solutions of the molybdenum compound and of the cobalt compound are prepared and are composited sucessively with the base material either with or without intervening heating of the support. In general, using this technique, it is preferred to composite the molybdenum component rst and then the cobalt component, although the reverse procedure may be employed. After the impregnation, the base material is dried tand then calcined to convert the metal compounds to the oxides.

Other suitable cobalt compounds for effecting deposition of cobalt oxide on the base material may be employed including, for example, cobalt ammonium nitrate, cobalt ammonium chloride, cobalt ammonium sulfate, cobalt bromide, cobalt bromate, cobalt chloride, cobalt chlorate, cobalt liuoride and cobalt fluorate. In similar manner, other suitable compounds of molybdenum may be employed. Suitable soluble molybdenum compounds include molybdenum Itetrabromide, molybdenum oxydibromide, molybdenum tetrachloride, molybdenum oxydichloride, molybdenum oxypentachloride and molybdenum oxytetrauoride.

The silica-containing component preferably in finely divided form is intimately mixed with the alumina-containing component which likewise is in a finely divided state preferably having Aa particle size within the approximate range of 60 'to 200 mesh (Tyler). After thorough mixing of the components, the resulting mixture is formed by pelleting, casting, molding or other means into pieces of desired size and shape such as rods, spheres, pellets, etc. After forming into particles of desired size, the resulting particles are dried and thereafter calcined at an elevated temperature in the approximate frange of 600 to 1200 F. It is understood that either the silica and aluminacontaining components may prior to Iadmixture be impregnated with molybdenum trioxide and cobalt oxide or that the mixed composite of silica and alumina may subsequently be impregnated With the oxides of molybdenum and cobalt.

The impregnating solution ordinarily contains the cobalt and molybdenum compounds in the proportions desired in the final catalyst and the impregnation is controlled to produce a final catalyst containing these components in the desired concentrations. The concentrations of the cobalt and molybdenum oxides in the catalyst described herein may respectively range from about 1 to about 8 percent by weight and from` about 3 to about 20 percent by weight o-f the final catalyst. The preferred catalysts contain cobalt oxide (C00) in a concentration of from about 2.0 to about 4.5 percent and molybdenum trioxide (M003) in a concentration of from about 7 to 16 percent by weight of the iinal catalyst. After impregnation the final composite generally is dried at a temperature of from about 200 to about 600 F. for a period of from about 2 to 24 hours or more and thereafter calcined at a temperature of from about 600 to 1200 F. for a period of from about l to l2 hours or more.

It is an essential feature of the catalyst of this invention that the silica content thereof be at least about 15 percent by weight. Composites containing amounts of silica less than about 15 percent by weight do not possess the requisite hydrocracking activity observed in the case of the pnesent catalyst. The cobalt oxide content of the catalyst, as noted hereinabove, is preferably between about 2 and about 4.5 percent by weight. A higher cobalt oxide content increased the saturation of the fuel oil and cycle stock, but decreased the combined naphtha and fuel -oil yield and caused a slight increase in the aging rate of the catalyst. An increase in the molybdenum trioxide content of the catalyst was found to raise the heavy naphtha to fuel oil ratio and to increase the saturation of the [fuel oil and cycle stock.

The catalyst described herein desirably has a surface area Within the approximate range of 200 to 370 square meters per gram. Composites having surface areas of less than about 200 square meters per gram were found to have considerably higher aging rates in the present low pressure hydrocracking process and accordingly are less preferred than catalysts characterized by surface areas within l:the aforementioned range. Within this range, the hydrocracking activity of the catalyst was observed to increase with increasing surface area.

The process of this invention may be carried out in any suitable equipment for catalytic operations. The process may be operated batchwise. lt is preferable, however, and generally more feasible to operate continuously. Accordingly, the process is adapted to operations using a fixed bed of catalyst. Also, the process can be operated using a moving bed of catalyst wherein the hydrocarbon flow may be concurrent or countercurrent to the catalyst flow. A uid type of operation wherein the catalyst is carnied in suspension in the hydrocarbon charge may feasibly be employed using the present catalyst.

Hydrocracking, in accordance with the present process, is generally carried out at a temperature between about 600 F. and about 950 F. and preferably between about 700 F. and about 900 F. The hydrogen partial pressure in such operation is generally within the range of about 700 and about 3000 pounds per square inch gauge and preferably about 1000 and 2000 pounds per square inch gauge. The liquid hourly space velocity of fresh feed ie. the liquid volume of hydrocarbons per hour per volume of catalyst is between about 0.1 and about l0 and preferably between about 0.25 and about 4. In general, the molar ratio of hydrogen to hydrocarbon charge employed, i.e. fresh feed, is between about 2 and about and preferably between about 5 and about 40.

Hydrocarbon charge stocks undergoing cracking in accordance with this invention comprise hydrocarbons, mixtures of I .ydrocarbons, and particularly hydrocarbon fractions having an initial boiling point of at least about 400 F., a 50 percent point of at least 500 F. and an end boiling point of at least 600 F. and boiling substantially continuously between said initial boiling point 'and end boiling point. Such hydrocarbon fractions include gas oils, residual stocks, cycle stocks, whole topped crudos and heavy hydrocarbon fractions obtained by the ydestructive hydrogenation of coal, tars, pitches, asphalts and the like. As will be recognized, the distillation of higher boiling petroleum fractions (about 750 F.) must be carried out under vacuum in onder to avoid thermal cracking. The boiling temperatures utilized herein, however, are expressed for convenience in terms of the boiling point corrected to atmospheric pressure.

The term gas oil7 ias employed in the art includes a variety of petroleum stocks. As utilized herein, this term, unless fur-ther modified, .includes any fraction disfr t tilled from petroleum which has an initial boiling point of at least about 400 F., a 50 percent point of at least about 500 F. and an end boil-ing point of at least about 600 F. and boiling substantially continuously between the initial boiling point and the end boiling point. The exact boiling range of a gas oil accordingly will be determined by the initial boiling point, the 50 percent point, and by the end boiling point. ln practice, petroleum distillations have been effected under vacuum at temp-eratureis as high as l200 F. (corrected to atmospheric pressure). Accordingly, in the broad sense, a gas oil is a petroleum inaction which boils substantially continuously within an approximate range of 400 F. to 1200" F., the 50 percent point being at least about 500 F. Thus, a gas oil may boil over the entire approximate range of 400 F. to 1200 F. or over an intermediate range such as 500 F. to 900 F.

A residual stock is any fraction which is not distilled. Accordingly, any fraction, regardless of its initial boiling point, which includes heavy bottoms, such as tars, asphalts, etc., is a residual fraction. A residual stock may be the portion of the crude remaining undistilled at about 1200 F. or it may he made up of a gas oil fraction plus the portion undistilled at about 1200 F.

A whole topped crude is the entire portion of the crude remaining after the light ends; i.e., the portion boiling up to about 400 F. has been removed by distillation. Accordingly, such a fraction includes the entire gas oil fraction and the undistilled portion of the crude petroleum boiling above about l200 F. lf desired, the residual fractions and the whole topped crude may be deasphalted by any suitable well-known means. Such deasphalting treatment, however, is not considered necessary for charge stocks utilizable in the process of this invention.

The refractory cycle stocks are cuts of cracked stocks which boil above the gasoline boiling range usually between about 400 F. and about 850 F. The refractory cycle stocks can be charged to the process of this invention, together with a fresh petroleum charge stock or the refractory cycle stocks may be charged to the process alone.

The hydrocracking selectivities of the catalysts described herein are evaluated by comparing their product distributions at fixed conversion levels. The conversion is defined as 100 minus the volume percent of charge remaining in the 650 F.-|- boiling range. The products considered are dry gas (C1-C3), C4 material, light naphtha (C5-180 F.), heavy naphtha (180-390 F.), fuel oil (390-650" F.) and cycle stock (650 F.-|). An overall measure of selectivity is the total yield of C5-650 F. material at any conversion level, since this range contains the more valuable products.

The hydrocraclring activity of a catalyst, as this term is utilized herein, is deined as the temperature required to achieve a given conversion level.

The catalyst aging rate, as this term is utilized herein, is defined as the rate of temperature increase (F./ day) required to maintain constant conversion with all operating conditions except temperature held constant.

The following examples will serve to illustrate the process of this invention without limiting the same:

EXAMPLE l A composite of cobalt and molybdenum oxides on alumina in the form of Ms x 1/s pellets and prepared by impregnation of alumina gel with approximately 3 percent by weight C00 and approximately 9.5 percent by weight M003, was crushed to a particle size of less than 100 mesh (Tyler). Approximately 85 parts by weight of the crushed material were mixed with approximately 43 parts by weight of silica hydrogel, containing about 35 weight percent Si02 and 65 weight percent water, and having a particle size of less than 60 mesh (Tyler). The resulting composite was intimately mixed by ball-milling the components for about 24 hours, at which time the particles were of 14 to l5 microns average size. The ball-milled material was then pelleted to 1m" diameter by 1A6" thick pellets. The pellets, so obtained, were then tempered for 3 hours at 1000 F. in dry air. The resulting product contained, on Va Weight basis, about 2.5 percent C00, about 8 percent M003, about 15 percent Si02 and about 74.5 percent Al203 and possessed a surface area of approximately l220 square meters Per gram.

EXAMPLE 2 A catalyst was prepared following the procedure of Example 1 but by mixing approximately 95 parts by weight of the crushed component of cobalt and molybdenum oxides on alumina with approximately 14 parts by weight of the crushed silica hydrogel. The resulting product contained, on a weight basis, about 3 percent C00, about 9 percent M003, about 5 percent Si02 and about 83 percent A1203 and possessed a surface area of approximately 188 square meters per gram.

EXAMPLE 3 A catalyst was prepared following the procedure of Example 1 but by mixing approximately 75 parts by weight of the crushed component of cobalt and molybdenum oxides on alumina with approximately 72 parts by weight of the crushed silica hydrogel. The resulting product contained, on a weight basis, about 2 percent C00, about 7 percent M003, about 25 percent S102 and about 66 percent Al203 and was characterized by a surface area of approximately 263 square meters per gram.

EXAMPLE 4 This example is not illustrative of the invention but is included for purposes of comparison. In this example, no silica was combined with the composite of cobalt and molybdenum oxides on alumina but this material was ground, repelleted, and tempered under the conditions of Example l. The resulting product contained, on a weight basis, about 3 percent C00, about 9.5 percent M003, and about 87.6 percent A1203 and had a surface area of approximately square meters per gram.

Properties of the above four catalysts are shown in Table I below:

Table 1 Example 4 2 1 3 CatalystJ composition, wt percent' AlzO 87. 5 83 74. 5 6G SiO@ 0 5 15 25 Density, glee.:

aelre( 0. 02 1.10 1.03 0.89

Particle 1. 55 l. 71 1.62 1. 45

Roal 3. 72 3. 54 3. 38 3. 1G Surface area, nL/g.. 185 188 220 263 Pore volume, ca /g 0. 3T3 0. 301 0. 320 0. 374 Pore diameter, A 81 64 58 57 It will be vsen from 'the above table that an effect of increasing silica addition is to increase the surface area and to decrease the average pore diameter of the resulting catalyst.

The above catalysts of Examples l-4 were tested in hydrocracking a charge of a 650 to 920 F. boiling range Gnico gas oil. lydrocracleing was carried out under a set or standard operating conditions, which have been found by experience to attord satisfactory evaluation of catalyst performance, thereby permitting a direct comparison of each of the catalysts to be made. The standard conditions involved conversion of the gas oil charge at 0.5 liquid hourly space velocity and at 1500 pounds per square inch pressure, utilizing a hydrogen to hydrocarbon charge mol ratio of about 40 corresponding to 14,500 standard cubic feet of hydrogen per barrel of charge. Hydrogen and the charge stock were mixed together at the .above pressure, heated to reaction temperature and passed downward through a bed of the catalyst contained in a test unit. Hot effluent from the bottom of the catalyst bed was cooled and separated at the pressure utilized in the unit into gas and liquid product streams. The liquid product stream was stabilized at atmospheric pressure before being sampled for distillation and analysis. The gases recovered from the high pressure separation and from stabilizing the liquid product were sampled and analyze-d. Activity of the catalysts was evaluated by operating the catalyst bed at three temperature levels selected so as to cover 40 to 95 volume percent conversion of the gas oil charge to material boiling below 650 F.

Performance of the control catalyst containing no silica, i.e. the catalyst of Example 4, in converting the gas oil charge under the standard test conditions is shown at three conversion levels of 40, 70 and 95 volume percent in Table Il below:

Table Il Conversion (100%, yield of 650 F.+ liquid),

vol. percent 40 70 95 Reactor temperature, F 776 820 862 Product yield, based on charge Dry gas, wt. percent 2.0 3. 5 7. 5

Total C4s. vol. percent l. 0 2.0 6.0 Cs, light naphtha, vol. percent 2. 5 5.0 10. 5 Heavy naphtha, vol. percent 5. 5 17.0 37.0 Fuel oil, vol. percent 33.0 51.0 50. Cycle stock, vol. percent 60.0 30. 0 5.0

Total liquid recovery, vol. percent 102.0 105.0 108.

Hydrogen consumption, s.c.I./b 750 1,050 Performance inspections:

Propane in dry gas, wt. percent 45 45 Heavy naphtha/fuel oil volume ratio 0.17 0.33 0.74 Isomerization (Weight ratio):

i/n Crs 0.4 0.4 i/n C5s 0.5 0. 5 Product inspections: Heavy naphtha:

Paralins, vol. percent 37 43 Naphthenes, vol. percent.- 42 36 Aromatics. vol. percent 21 21 Olelius, vol. percent 0 0 Fuel oil:

Diesel index .42 51 Aromatics, vol. percent.- 38 32 Oletlns, vcl. percent 9 `3 Performance of the catalyst containing 5 Weight percent silica, i.e. the catalyst of Example 2, in converting the gas oil charge under the standard test conditions is shown at three conversion levels of 40, 70 and 95 volume percent in Table Ill below:

Table III Conversion (100%, yield of 650 F.+ liquid),

vol. percent 40 70 95 Reactor temperature, F 777 811 848 Product yield, based on charge Dry gas. wt., percent 2.0 3. 5 6.0

Total Crs, vol. percent 1. 5 3. 5 7. 5 C5s, light naphtha, vol. percent- 1. 5 5. 5 13.0 Heavy naphtha, vol. percent 7. 5 23. 0 45. 0 Fuel oil, vol. percent 32. 5 45.0 39 0 Cycle stock. vol. percent 60.0 30.0 5.0

Total liquid recovery, vol. percent 103. 0 107.0 110. 5

Hydrogen consumption, s.c.i./b 440 800 l, 150 Performance inspections:

Propane in dry gas. Wt. percent 35 45 45 Heavy naphtha/iuel oil volume ratio 0. 23 0. 51 1. 18

1. 3 1. 0 2.4 2.0 Product inspections.

Heavy naphtha:

Paratlins, vol. percent 31 37 44 Naphtlienes, vol. percent 50 46 38 Aromatics, vol. percent 18 17 18 Olens, vol. percent 1 0 0 Fuel oil:

Diesel index 43 49 58 Aromatics, vel. percent 26 26 28 Olefins, vol. percent 9 3 Cycle stock: Diesel index 76 84 79 Performance of the catalyst containing 15 weight percent silica, i.e. the catalyst of Example 1, in converting the gas oil charge under the standard test conditions is shown at three conversion levels of 40, 70 and 95 volume percent in Table lV below:

Table 1V Conversion yield ol 650 F.+ liquid),

vol. percent 40 70 95 Reactor temperature, F 757 787 815 Product yield, based on charge:

Dry gas, wt. percent 1. 5 3. 0 5. 0

Total Cis, vol. percent 1. 5 4.5 9.0 05's, light naphtha, vol. percent 2.0 6. 5 15. 5 Heavy naphtha, vol. percent 9. 0 26. 5 48. 5 Fuel oil, vol. percent 32.0 41.0 36.0 Cycle stock, vol. percent 60.0 30.0 5.0

Total liquid recovery, vol. percent 104. 5 108. 5 114. 0

Hydrogen consumption, s.c,f./b 560 860 1, 270 Performance inspections:

Propane in dry gas, wt. percent 60 65 65 Heavy naphtha/fuel oil volume rati 0. 28 0. 66 1 35 Isomerization (weight ratio):

i/n Gis 1. 4 1.1 i/n C5S. 2. 5 2.1 Product inspecti Heavy naphtha:

Parallins, vol. percent 29 38 49 Naphthenes, vol. percent 52 48 39 Aromatics, vol. percent 18 14 12 Oletlns, vol. percent l O 0 Fuel oil:

Diesel index 44 53 63 Aromatics, vol. percent 28 24 20 Oleus, vol. percent 15 10 6 Cycle stock: Diesel index 73 86 88 Performance tof the catalyst containing 25 weight percent silica, i.e. the catalyst of Example 3, in converting the gas oil charge under the standard test conditions is shown at three conversion levels of 40, 70 and 95 Volume percent in Table V below:

Table V Conversion (100%, yield of 650 F.+ liquid),

vol. percent 40 70 95 Reactor temperature, F 756 788 810 Product yield, based on charge:

Dry gas, wt. percent 1. 5 3.0 4. 0

Total Cds, vol. percent 1.0 5.0 10.0 C5s, light naphtha, vol. percent 2.0 6.5 16. 0 Heavy naphtha, vol. percent 8. 5 26.0 47. 5 Fuel oil, vol. percent 32. 5 41. 0 36. 0 Cycle stock, vol. percent 60. 0 30. 0 5. 0

Total liquid recovery, vol. percent 104.0 108. 5 114. 5

Hydrogen consumption, s.c.f./b 450 810 1, 240 Performance inspections:

Propane in dry gas, wt. percent 60 65 65 Heavy naphtha/fuel oil volume ratio 0. 26 0. 63 1. 32 Isomerization (weight ratio):

i/n C4s 1. 4 1. 1 i/n Cs 2. 5 2. 1 Product inspections:

Heavy naphtha, vol. percent:

Paramus 27 37 48 Naphthenes 51 48 38 Aromatics 21 .l5 14 Olens l 0 0 Fuel oil:

Diesel index 48 54 60 Aromatics, vol. percent 27 24 23 Oletins, vol. percent 12 0 8 6 Cycle stock: Diesel index 74 83 80 Graphical comparisons of the above four catalysts are set forth in the attached drawing wherein:

FIGURE 1 shows the relationship between reactor temperature and catalyst silica content.

FIGURE 2, shows the relationship between the dry gas yield and catalyst silica content.

FIGURE 3 shows the relationship between the yield of total C4s and catalyst silica content.

FIGURE 4 shows the relationship between the yield of C5s-light naphtha and catalyst silica content.

FIGURE 5 shows the relationship between the yield of heavy naphtha and catalyst silica content.

FIGURE 6 shows the relationship between the yield of fuel oil and catalyst silica content.

FIGURE 7 shows the relationship between diesel index of the fuel oil product (390-650 F. boiling range) and catalyst silica content.

It will be seen from reference to FEGURE 1 that the catalysts of 15 and higher' weight percent silica content were much more active than catalysts having a silica content of less than about l5 Weight percent. Activities are compared here in terms of the catalyst bed temperature required to convert the charge oil. Thus, it will be seen that the average catalyst bed temperature required to obtain 40, 70 and 95 percent conversions of the gas oil charge decreased steadily with increasing silica content of the catalyst until a silica content of about 15 weight percent was reached. Thereafter, the required temperature leveled olf with increasing silica content in the catalyst. Low catalyst bed temperatures, as will be realized, are highly desirable in commercial hydrocracking operations both from a process and mechanical design standpoint.

It will be seen from the data of Tables ll to V, as well as from FlGS. 2 to 6, that the catalysts of 15 and greater weight percent silica gave greatly superior product distributions than are obtainable with the catalyst of no silica or with the catalyst containing only 5 weight percent silica. Thus, FIGURES 2 to 6 show the product distributions obtained at 40, 70 and 95 percent conversions of the gas oil plotted against the silica content of the catalysts. The yield of total C4s, C5s-light naphtha, and heavy naphtha increase as the silica content of the catalyst increased from to about 15 Weight percent and thereafter level off with further increases in the silica content of the catalyst. The dry gas yield decreases substantially with increasing silica content from 0 t0 15 weight percent at the 95 percent conversion level. The fuel oil yield decreases as the silica content of the catalyst increases from 0 to 15 Weight percent and thereafter levels off with an increasing content of silica.

It will be noted by reference to FIG. 7 Where the diesel index of the 390-650 F. `boiling range product fuel oil is plotted against the silica content of the catalyst that the diesel index increased with increasing silica content until the catalyst contained about 15 weight percent and thereafter leveled off with increasing content ot' silica.

The following examples illustrate various methods for preparing the catalyst of the invention including cornparative evaluation of the catalyst products so obtained:

EXAMPLE 5 A catalyst using the procedure of Example 1 was prepared. The resulting product contained, on a Weight basis, 2.9 percent C00, S percent M003, 15.2 percent Si02 and 73.9 percent A1203 and was characterized by a surface area of approximately 238 square meters per gram.

EXAMPLE 6 Alumina and silica hydrogel, containing about 35 weight percent SiOz and 65 weight percent Water, Were dried separately for 16 hours at 240 F. and were then crushed to a particle size of less than 60 mesh (Tyler). A composite containing about 82 parts by weight of alumina and about 18 parts by weight of silica, on a dry basis, was formed by mixing these crushed materials. The resulting composite Was ball-milled dry for about 24 hours, at which time the particles were of 14 to 15 microns average size. The ball-milled material was then pelleted to 1/8 diameter by 1/16 thick pellets. The pellets, so obtained, were then calcined for 3 hours at 900 F. in dry air.

The pellets of silica and alumina were then pretreated with carbon dioxide and impregnated under vacuum with suflicient ammonium molybdate solution to yield a composite containing about l0 weight percent M003 on a dry basis. The impregnated pellets were dried for 8 l2 hours at 240 F. and calcined for 3 hours at 900 F. in dry air.

The pellets were again pretreated with carbon dioxide and impregnated under vacuum with suicient cobaltous nitrate solution to yield a composite containing about 3 weight percent C00 on a dry basis. The impregnated pellets were then dried for 8 hours at 240 F. and calcined for 3 hours at 900 F. in dry air, yielding the finished catalyst.

EXAMPLE 7 A cogel containing, on a dry basis, 79 Weight percent of alumina and 21 Weight percent of silica was prepared by mixing 1000 cc. of a sodium silicate solution containing 1.4 weight percent Na20, 4.5 weight percent Si02 and 94.1 Weight percent Water with 1000 cc. of 30.6 weight percent aqueous sodium aluminate solution in the presence of 800 cc. of a 34.2 Weight percent aqueous solution of citric acid. The resulting cogel was aged for about 16 hours at room temperature and was then baseexchanged with 20 weight percent aqueous ammonium sulfate solution. The cogel was then washed with water until sulfate free. The Washed cogel was dried for 24 hours at 240 F. to 250 F. in 100 percent steam and then ball-milled dry for 16 hours. The dried cogel was pelleted into Ms" diameter by 1/16 thick pellets.

The resulting pellets were pretreated with carbon dioxide and impregnated under vacuum with sufficient ammonium molybdate solution to yield a composite containing about 7.6 Weight percent M003 on a dry basis. The impregnated pellets were dried for 8 hours at 240 F. and calcined for 3 hours at 900 F. in dry air.

EXAMPLE 8 Alumina was extruded into Ms diameter particles. The extruded particles were dried at 230 F. and calcined for 3 hours at 1000 F. in dry air. The calcined particles were pretreated with carbon dioxide and impregnated under vacuum with a solution containing ammonium rnolydate and cobaltous nitrate in amounts sufcient to yield a composite containing about 10 weight percent M003 and about 3 weight percent C00, on a dry basis. The alumina particles were soaked for about 16 hours in the impregnating solution. The impregnated alumina was then dried at 230 F. and calcined for 3 hours at 1000 F. in dry air. i

The impregnated alumina was crushed to a particle size of less than 60 mesh (Tyler) and mixed with silica hydrogel, containing about 35 Weight percent SiOz and about 65 weight percent water, having a particle size of less than 60 mesh (Tyler), in such proportions that the mixture contained about weight percent impregnated alumina and about 15 weight percent silica, on a dry basis. The resulting composite was intimately mixed by dry ballmilling for about 24 hours, at which time the particles were of 14 to 15 microns average size. The ball-milled material was then pelleted to M3" diameter, by lAG" thick pellets. The pellets, so obtained, were then tempered for 3 hours at 1000 F. in dry air.

EXAMPLE 9 Alumina was mixed with Water to form a slurry containlng about 9 cc. of Water per gram of dry alumina. Aqueous solutions of ammonium molybdate and cobaltous nitrate were added to this slurry in amounts suicient to yield a composite containing about 12 weight percent M003 and 3 weight percent C00, on a dry basis. The resulting composite was aged for 16 hours at room ternperature.

Silica hydrogel, containing about 35 weight percent SiOz and 65 Weight percent water, and having a particle size of less than 60 mesh (Tyler), was added to the alumina-molybdena-cobalt oxide slurry in an amount sufficient to yield a composite containing 15 Weight percent Si02 on a dry basis. The resulting composite was intimately mixed by wet ball-milling for about 24 hours,

It will be seen from the above comparative data that the catalysts of Examples 6 and 8, despite the difference in their methods of preparation, have similar hydrocracking performance.

Comparative evaluation of the catalysts of Examples 5 and 7 at 30, 50 and 70 volume percent conversion level shown in Table VII below:

Table VII Conversion (100%, yield of 650 F.+

liquid) vol. percent 30 50 70 EX- Ex- Ex- Ex- Ex- Ex- Catalyst ample ample ample ample ample ample Reactor temperature, F 750 710 790 760 805 795 Product yield, based on charge' Dry gas, wt. percent 1. 1. 0 2.0 1. 5 6.0 2. 5

Total C4 s, vol. percent 0.5 1. 0 1. 5 1. 5 3. 5 3.5 C5, light naphtha, vol. percent 1. 0.5 3. 5 2. 5 5.0 6.5 Heavy naphtha, vol. percent 8.0 5.0 17. 0 15. 5 23. O 30. 0 Fuel oil, v01. percent 24. 0 26. 5 34. 0 38. 0 44. 5 41. 0 Cycle stock, vol. percent 70. 0 70.0 50.0 50. O 30. 0 30. 0

Total liquid recovery, vol.

percent 104. 0 103. 0 106. 0 107. 5 106. 0 111. 0

C5, fuel oil yield, vol. percent 33. 5 32.0 54. 5 56.0 72. 5 77. 5 Hydrogen consumption, s.e.f./b 750 750 1, 100 1, 100 1, 450 1, 450 Product inspections:

Heavy naphtha:

Parafns, vol. percent.-. 22 16 27 21 32 28 Olens. vol. percent 3 3 0 2 O 1 Naphthenes, vol. percent- 45 56 50 56 48 56 Aromatics, vol. percent- 25 23 21 20 15 Fuel oil: Diesel index 31 35 40 47 50 59 after which time the particles were of about 14 to 15 microns average size. The ball-milled material was then dried at 230c F., pelleted to 1/e" diameter by V16" thick pellets and calcined for 3 .hours at l000 F. dry air.

The above catalysts were tested in hydrocracking a charge of a 650 to 800? F. boiling range West Texas gas oil. The test conditions involved conversion of the gas oil charge at 1 liquid hour-ly space velocity and at 2000 pounds per square inch pressure, utilizing a hydrogen to hydrocarbon mol ratio ofk about 40, correspond-ing to 14,500 standard cubic feet of hydrogen per barrel of charge. Activity of the catalysts vvas evaluated by operating the catalyst bed at varying tempera-ture levels selected so as to cover 30 to 70 volume percent conversion of the gas oil charge to material boiling below 650 F.

Comparative evaluation of the catalysts of Examples 6 and 8 at a 5.0 and 70 volume percent conversion level is shown in Table VI below:

Table VI It will be seen from the above comparative data that the catalyst .of Example 7 wherein the preparation method involved impregnation of cogelled silica-alumina with cobalt and molybdenum oxides was less active, particularly at the lower conversions, than the catalyst of Example 5 prepared by mechanical addition of silica to a composite of alumina previously impregnated with the oxides of cobalt and molybdenum. At the higher Conversions, the product distribution employing the catalyst of Example 7 is inferior to that obtained with the catalyst of Example 5. Thus with the catalyst of Example 7, the dry gas make is higher and the naphtha and total product yields are lower than those obtained with the catalyst of Example 5. In addition, the hydrogenating activity of the Example 7 catalyst is lower than that of the Example 5 catalyst, as shown by the lower diesel indices of the fuel oil. It will accordingly be appreciated that in View of the foregoing, it is preferred to employ a catalyst wherein the alumina-containing and silica-containing components are composited by mechanical admixture thereof rather However, it is to be understood that the above description is merely illustrative of preferred embodiments of the invention, of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

1. A process for cracking hydrocarbon fractions which comprises contacting, in the presence of hydrogen, a hydrocarbon fraction having an initial boiling point of at least about 400 F., a 50 lpercent point of a-t least about 500 F. and an end point of at least about 600 F. and boiling substantially continuously between said initial boiling point and said end point with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent cobalt oxide, 3 to 20 percent by Weight molybdenum trioxide and remainder alumina prepared by impregnating the alumina component with the cobalt oxide and molybdenum trioxide components, mechanically mixing the resulting impregnated product with the silica component, drying and calcining the resulting composite at an elevated temperature, said contacting being effected i 1 conversion yield 0r 650 F.+ than b1 cogelatonliquid), vol. percent 50 70 Catal st Exam- Exam- Exam- Examy ple 8 ple 6 ple 8 ple 6 55 Reactor temperature, F 790 775 822 810 Product yield, based on charge: We chum Dry gas, wt. percent 2.0 1. 5 3. 0 2. 5

Total C4s, vol. percent 1. 5 1. 5 3. 5 3.0 60 C5. light naphtha, vol. percent.-- 3.5 3.0 8.0 6.5 Heavy naphtha, vol. percent- 18. 0 16. 5 33. 0 29. 5 Fuel oil, vol. percent 34. 0 35. 5 36. 0 40. 5 Cycle stock, vol. percent 50.0 50.0 30.0 30.0

Total liquid recovery, vol.

percent 107.0 106. 5 110. 5 109. 5 65 C5, fuel oil yield, vol. percent- 55. 5 55. 0 77. 0 76. 5 Hydrogen consumption, s.c.f./b 1, 000 900 1, 300 1, 200 Product inspections: Heavy naphtha:

Parains, vol. percent 25 26 33 34 Olens, vol. percent 1 5 2 5 Naphthenes, vol. percen 54 46 51 44 70 Aromatics, vol. percent 20 23 14 17 Fuel oil:

Diesel index 43 43 56 52 Saturates, vol. percent 64 55 70 66 Olelins, vol. percent B 22 5 14 Aromatics. vol. percent 28 23 25 20 at a temperature between about 600 F. and about 950 F., a liquid hourly space velocity between about 0.1 and anaemia about l0, a hydrogen partial pressure between about 700 and about 3000 pounds per square inch gauge employing a molar ratio of hydrogen to hydrocarbon charge between about 2 and about 80.

2. A process for cracking hydrocarbon fractions which comprises contacting, in the presence of hydrogen, a hydrocarbon fraction having an initial boiling point of at least about 400 F., a 50 percent point of at least about 500 F. and an end point of at least about 600 F. and boiling substantially continuously between said initial boiling point and said end point with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by mechanically mixing the alumina and silica components and impregnating the resulting composite with the cobalt 4oxide and molybdenum trioxide components, drying and calcining the resulting product at an elevated temperature, said contacting being effected at a temperature between about 600 F. and about 950 F., a liquid hourly space velocity between about 0.1 and about 10, a hydrogen partial pressure between about 700 and about 3000 pounds per square inch gauge employing a molar ratio of hydrogen to hydrocarbon charge between about 2 and about 80.

3. A process for cracking hydrocarbon fractions which comprises contacting, in the presence of hydrogen, a hydrocarbon fraction having an initial boiling point of at least about 400 F., a 50 percent point of at least about 500 F. and an end point of at least about 600 F. and boiling substantially continuously between said iiiitial boiling point and said end point with a catalyst characterized by a surface area in the approximate range of 200 to 370 square meters per gram and consisting essentially of 15 to 40 percent by weight of silica, 1 to 8 lpercent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by intimately mixing silica hydrogel with alumina having a surface area greater than 100 square meters per gram, impregnating the resulting composite with the cobalt oxide and molybdenum oxide components, drying arid calcining the resulting product at an elevated temperature, said contacting being effected at a temperature between about 600 F. and about 950 F., a liquid hourly space velocity between about 0.1 and `about 10, a hydrogen partial pressure between about 700 and about 3000 pounds per square inch gauge employing a molar ratio of hydrogen to hydrocarbon charge between about 2 and about 80.

4. A process for cracking hydrocarbon fractions which r comprises contacting, in the presence of hydrogen, a hydrocarbon fraction having an initial boiling point of at least about 400 F., a 50 percent point of at least about 500 F. and an end point of at least about 600 F. and boiling substantially continuously between said initial boiling point and said end point with a catalyst characterized by a surface area within the approximate range of 200 to 370 square meters pergram consisting essentially of l5 to 40 -percent by weight silica, 1 to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by impregnating alumina having a surface area greater than 100 square meters per gram with the cobalt oxide and molybdenum trioxide components, mechanically mixing the resulting impregnated product with silica hydrogel, drying and calcining the resulting composite at an elevated temperature, said contacting being effected at a temperature between a bout 600 F. and about 950 F., a liquid hourly space velocity between about 0.1 and about 10, a hydrogen partial pressure between about 700 and about 3000 pounds per square inch gauge employing a molar ratio of hydrogen to hydrocarbon charge between about 2 and about 80.

5. A catalyst, characterized by hydrocracking activity, and consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by impregnating the alumina component with the cobalt oxide and molybdenum trioxide components, mechanically mixing the resulting impregnated product with the silica component, drying and calcining the resulting composite at an elevated temperature.

6. A catalyst, characterized by hydrocracking activity and consisting essentially of 15 to 40 percent by weight silica, l to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by mechanically mixing the alumina and silica components and impregnating the resulting composite with the cobalt oxide and molybdenum trioxide components, drying and calcining the resulting product at an elevated temperature.

7. A catalyst characterized by a surface area in the approximate range of 200 to 370 square meters per gram and consisting essentially of 15 to 40 percent by weight of silica, 1 to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by intimately mixing silica hydrogel with alumina having a surface area greater than square meters per gram, impregnating the resulting composite with the cobalt oxide and molybdenum oxide components, drying and calcining the resulting product at an elevated temperature.

8. A catalyst characterized by a surface area within the approximate range of 200 to 370 square meters per gram consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina prepared by impregnating `alumina having a surface area greater than 100 square meters per gram with the cobalt oxide and molybdenum trioxide components, mechanically mixing the resulting impregnated product with silica hydrogel, drying and calcining the resulting composite at an elevated temperature.

References Cited by the Examiner UNITED STATES PATENTS 2,698,305 12/54 Plank et al 252-455 2,728,710 12/55 Hendricks 208--112 2,799,626 7/57 Johnson et al. 208-110 2,882,221 4/59 Dinwiddie et al 208-111 2,911,356 11/59 Hanson 208--110 OTHER REFERENCES Advances in Catalysts, vol. VI (1954), page 384, Academic Press Inc., New York, publishers.

Conversion of Petroleum, Sachanen, 2nd edition, page 314.

ALPHONSO D. SULLIVAN, Primary Examiner.

ALLAN M. BOETTCHER, MILTON STERMAN,

Examiners.

UNITED STATES PATENT oFFIcr; CERTIFICATE OF CORRECTION Patent No 3,l82,t`ll2 May 4, 1965 Lewis Ml Browning e1: allc It is hereby certified that error appears in the above numbered patent reqlrng correction and that the said Letters Patent should read as cozrected'below.

Column fl, lino o, for "commingllng" read comingling llne 36, for "hydogel read hydrogel Column 5, line lo, afte 1" "example" next alumina 'Y I lne 24, for Suceselvely read Successi-ely l' column 8, line 58, for "Seu from the L above Table read Seen from the above Table Column 9, ljr for "gases" read gas Slgned and sealed this 12th day of October 1965.

SEAL) Lest:

{NEST W. SW1 DER EDWARD J. BRENNER Icstin Officer Commissioner of Patents

Claims

1. A PROCESS FOR CRACKING HYDROCARBON FRACTIONS WHICH COMPRISES CONTACTING, IN THE PRESENCE OF HYDROGEN, A HYDROCARBO FRACTION HAVING AN INITIAL BOILING POINT OF AT LEAST ABOUT 400*F., A 50 PERCENT POINT OF AT LEAST ABOUT 500*F. AND AN EMD POINT OF AT LEAST ABOUT 600*F. AND BOILING SUBSTANTIALLY CONTINUOUSLY BETWEEN SAID INITIAL BOILING POINT AND SAID END POINT WITH A CATLYST CONSISTING ESSENTIALLY OF 15 TO 40 PERCENT BE WEIGHT SILICA, 1 TO 8 PERCENT COBALT OXIDE, 3 TO 20 PERCENT BY WEIGHT MOLYBDENUM TRIOXIDE AND REMAINDER ALUMINA PREPARED BY IMPREGNATING THE ALUMINA COMPONENT WITH THE COBALT OXIDE AND MOLYBDENUM TRIOXIDE AND REMAINDER ALUMINA PREPARED BY IMPREGNATING THE ALUMINA COMPONENT WITH THE COBALT OXICE AND MOLYBDENUM TRIOXIDE COMPONENTS, MECHANICALLY MIXING THE RESULTING IMPREGNATED PRODUCT WITH THE SILICA COMPONENT, DRYING AND CALCINING THE RESULTING COMPOSITE AT AN ELEVATED TEMPERATURE, SAID CONTACTING BEING EFFECTED AT A TEMPERATURE BETWEEN ABOUT 600*F. AND ABOUT 950* F., A LIQUID HOURLY SPACE VELOCITY BETWEEN ABOUT 0.1 AND ABOUT 10, A HYDROGEN PARTIAL PRESSURE BETWEEN ABOUT 700 AND ABOUT 3000 POUNDS PER SQUARE INCH GUAGE EMPLOYING A MOLAR RATIO OF HYDROGEN TO HYDROCARBON CHARGE BETWEEN ABOUT 2 AND ABOUT 80.