US 3068169 A
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United States PatentOfiice 3,068,169 Patented Dec. 11, 1962 3,068,169 CATALYTIC REFORMING WITH PLATINUM ON A SILICA-ZERCONIA BASE Syivander C. Eastwood, Woodbury, Stephen M. Oleck,
Moorestown, and Stephen J. Wantuck, West Collingswood, N.J., assignors to Soeony Mobil Gil Company, Inc., a corporation of New York No Drawing. Filed Feb. 26, 1960, Ser. No. 11,126 4 Claims. (Cl. 208-134) This invention relates to an improved catalytic reforming process for obtaining gasoline of high octane number. More particularly, the present invention is directed to catalytic reforming carried out in the presence of a catalyst consisting essentially of a particularly prepared silica-zirconia cogel having deposited thereon a small amount of a metal of the platinum series.
Reforming operations, wherein hydrocarbon fractions such as naphthas, gasolines, and kerosene are treated to improve the anti-knock characteristics thereof are well known in the petroleum industry. These fractions are composed predominately of normal and slightly branched paraffinic hydrocarbons and naphthenic hydrocarbons together with small amounts of aromatic hydrocarbons. During reforming a multitude of reactions take place including isomerization, aromatization, dehydrogenation, cyclization, etc. to yield a product having an increased content of aromatics and highly-branched paraffins. Thus, in reforming, it is desired to dehydrogenate the naphthenic hydrocarbons to produce aromatics, to cyclize the straight chain parafiinic hydrocarbons to form aromatics, to isomerize the normal and slightly branched paraffins to yield highly branched chain parafiins and to effect a controlled type of cracking which is selective both in quality and quantity. v
Normal and slightly branched chain paraifinic hydrocarbons of the type contained in the above fractions have relatively low octane ratings. Highly branched-chain parafiinic hydrocarbons, on the other hand, are characterized by high octane ratings. Accordingly, one objective of reforming is to effect isomerization of thenormal and slightly branched-chain paraflins to more highly branched-chain paraffins. Since aromatic hydrocarbons have much higher octane ratings than naphthenic hydro.- carbons, it is also an objective of reforming to simultaneously produce aromatics in good yield. The production of aromatic hydrocarbons during reforming is effected by dehydrogenation of the naphthenic hydrocarbons and dehydrocyclization of the parafiinic hydrocarbons; Aromatic hydrocarbons are also produced by isomerization of alkyl cyclopentanes to cyclohexenes which thereafter undergo dehydrogenation to form the desired aromatics,
During reforming, it is extremely important to produce as little carbon and normally gaseous product material as is possible, since such materials represent essentially an economic loss to be charged against the process. The
roperty of the catalyst which is instrumental in effecting high yields of normally liquid product is referred to as selectivity, and this property is measured as the quantity of normally liquid product, substantially free of hydrocarbons containing four or less carbon atoms, which is produced at a given octane level. Large improvements in selectivity are not very probable, since it appears that there is a limit to the quantity of normally liquid product material which can be produced, as it is unavoidable to obtain some carbon and normally gaseous product material at the elevated temperatures employed for reforming. Consequently, any increase in selectivity to the extent of at least one-half of a percent is considered significant by reason of the difficulty in obtaining such an improvement as well as the economic advantage which results therefrom. It has been found, in accordance with the present invention, that reforming may be efficiently accomplished in the presence of a platinum metal-containing silica-zirconia catalyst prepared in a particular manner which catalyst has been found to possess a significantly greater selectivity than those heretofore employed.
Broadly, the present invention provides a method for reforming hydrocarbon mixtures by contacting the same under reforming conditions with a catalyst consisting essentially of a minor proportion of a platinum metal deposited on a base of silica and zirconia, having a zirconia content of between about 2 and about 20 percent by weight, prepared by reacting a water-soluble zirconium compound and an alkali metal silicate to effect formation of a gelable sol consisting essentially of silica and zirconia characterized by a pH in excess of 6 and a Zirconia content, on a dry basis, of between about 2 and about 20, permitting said sol to set forming a silica-zirconia gel, reducing the pH of said gel to below 5 and maintaining the gel under such conditions of reduced pH while in contact with an aqueous medium at a temperature in the approximate range of 15:0 to 220 F. for a period ofat least about 1 hour, under conditions of substantially atmospheric pressure, thereafter washing the gel free of soluble matter, drying and calcining.
In another embodiment, the invention resides in a process for reforming a petroleum distillate boiling within the approximate range of 60 F. to 450 F by contacting the same at a temperature between about 700 F., and about 1000 F. at a liquid hourly space velocity between about 0.1 and about 10 inlthe presence of hydrogenunder a pressure between about and about 1000 pounds per square inch gauge and a molar ratio of hydrogen to hydrocarbon between about 1- and about 20 with the catalyst above defined.
In still another embodiment, the invention comprises a process for reforming a petroleum naphtha by bringing the same into contact with a catalyst consisting essentially of between about 0.05 and about 5 percent by weight of platinum deposited on a cogel of silica and zirconia prepared as described hereinabove at a temperature between about 800 F. and about 975 F., at a liquid hourly space velocity between about 0.5 and about 4 in the presence of hydrogen under a pressure between about 200 and about 700 pounds per square inch gauge and a molar ratio of hydrogen to hydrocarbon between about 4 and about 12. p p y We are aware that it has heretofore been proposed to convert hydrocarbon fractions in the presence: of hydro gen and certain catalytic composites comprising a platinum metal supported on an active cracking component of silica combined with alumina, zirconia, magnesia and the like. The reforming process described herein is distinguishable from such prior processes in that the silicazirconia base upon which the platinum metal is deposited is prepared in accordance with a particular procedure which has been found to result after the aforesaid im-' pregnation, in an unusually selective reforming process.
Following the teachings of this invention, it has been found that reforming can be accomplished on a highly selective basis when carried out in the presence of a catalyst obtained by impregnation of a small amount ofa platinum metal on a composite of silica and zirconia which has been prepared by reacting a water-soluble zirconium compound and an alkali metal silicate to effect formation of a gelable sol consisting essentially of silica and zirconi'a characterized by a pH in excess of 6' and a zirconia content, on a dry solids basis, of between about 2 and about 20 percent byweight, permitting the sol to set with formation of a silica-zirconia gel, reducing the pH of the gel to below 5 and activating the same by maintaining the gel under such conditions of reduced pH while in contact with an aqueous medium at a temperature in the approximate range of 150 to 220 F. for a period of at least about 1 hour under conditions of substannally atmospheric pressure, thereafter washing the gel free of soluble matter, drying and calcining. A catalyst prepared in accordance with the foregoing procedure has been found to be characterized by unusual selectivity in reforming hydrocarbon mixtures and, particularly, petroleum distillates boiling within the approximate range of 60 F. to 450 F.
In the foregoing procedure it has been discovered that the activation step of treating the silica-zirconia gel in an aqueous medium at the specified conditions and the controlof pH during gelation and such activation step are essential in achieving the unusual selectivity characterizing the described catalyst. It has been found, in accord ance with the present invention, that not only is the activation step essential but that also the conditions required during this step to obtain the above-indicated desirable catalyst property are very critical. Thus, the pH during the activation step is essentially below 5 and preferably below 3. The pH of gel formation, on the other hand, is essentially above 6 permitting the attainment of silicazirconia gels characterized by particularly favorable gel properties as well as by a short time of set, i.e. generally less than 2 hours and more particularly, less than 20 seconds. Hydrogels prepared at a pH above 6 are much more susceptible to activation than those prepared below 6 pH. The temperature of the activation treatment involving the use of an aqueous medium is above about 150 F. and preferably above 175 F. and generally does not exceed 220 F. The time required for activation is generally at least 1 hour and may extend up to 48 hours or longer. Preferably, the activation period is at least 2 hours and usually in the approximate range of 2 to 24 hours.
The intermediate hydrogel'state obtained in preparation of present catalysts is to be distinguished from a gelatinous precipitate. True all-embracing hydrogels occupy the entire volume of the solution from which they are formed and possess a definite rigid structure. When fractured, a true hydrogel shows a conchoidal fracture as compared to an irregular ragged edge fracture as obtained in the case of gelatinous precipitates. The latter occupy only a part of the volume of the solution from which they are formed and have no rigidity of structure. In addition, hydrogels can generally be more easily washed free of soluble impurities due to the tendency of gelatinous precipitates to peptize on washing. A distinct and further advantage of hydrogels is that due to their rigid structure, they can be formed into high quality spheroidal particles.
The zirconium compound employed in the present process is a water-soluble compound and suitably a watersoluble mineral acid salt of zirconium such as, for ex ample zirconium nitrate; zirconium sulfate and zirconyl chloride. Of this group, zirconium sulfate is accorded preference. Zircon sand is a suitable source of zirconium compound. The zirconia content of such sand can be converted to zirconium sulfate through caustic fusion at temperatures exceeding 1000 F. and subsequent leaching with sulfuric acid.
The silicate reactant is generally an alkali metal silicate and, particularly, sodium silicate although silicates of the other alkali metals such as for example, potassium silicate, might likewise be employed. An organic silicate ester, for example, ethyl orthosilicate may also be employed as the source of silica.
The solutions of zirconium compound and silicate reactant are intimately mixed in such proportions as to yield a gelable sol having a zirconia content, on a dry basis, of. between about 2 and about 20 and preferably between aboutS and about 15 percent by weight and a pH of above 6 and generally not exceeding about 10.
The resulting product is a hydrosol of silica and zircoma characterized by an inherent capacity to set t a hydrogel upon lapse of a suitable period of time extending from a few seconds up to several hours depending on pH, temperature and solids concentration without ad dition to or subtraction from the hydrosol of any substance. By following the above procedure the time of gelation can be very rapid, i.e. less than 20 seconds, which permits the gel to be prepared directly in the form of spheroidal particles resulting in a product of improved physical properties and in definite economic advantages in the manufacture of the catalyst. In addition to affording rapid gelation, the high pH of gel formation has been found to give rise to a more selective reforming catalyst upon impregnation with a platinum metal as described hereinbelow as compared with a comparable silicazirconia gel in which the pH of formation is below 6.
The silica-zirconia hydrogel so obtained is thereafter treated to reduce the pH thereof to below 5 and preferably less than 3 but greater than 1. To accomplish such purpose, the hydrogel is contacted with an acidic fiuid after formation. While the lapse of a brief interval of time is permissible, it is generally desirable to reduce the pH of the silica-zirconia hydrogel shortly after formation to less than 5. Maintaining the hydrogel under conditions of pH at which formation is etfected for a considerable period of time was found to be detrimental to the selectivity of the finished catalyst. Generally, the hydrogel is contacted with an aqueous solution of an acid or an acidic salt of sufficient concentration to eifectively reduce the hydrogel pH to less than 5. Usually, an
-inorganic acid and particularly a dilute solution of a mineral acid such as nitric, hydrochloric or sulfuric acid in the form of a 0.1 to 10 weight percent solution is employed for this purpose. Salts such as sulfates, nitrates or chlorides of zirconium or aluminum can similarly be used. With use of an aluminum salt, for example a mineral acid aluminum salt such as aluminum sulfate, introduction of aluminum in the hydrogel structure takes place resulting in a gel base of silica, zirconia and alumina, content of the latter component where so introduced is within the approximate range of 3 to 20 percent by weight.
The hydrogel of reduced pH is then activated by maintaining the same under the aforementioned conditions of reduced pH while in contact with an aqueous medium at a temperature in the approximate range of to 220 F. and more particularly, between about and about 220 F. at substantially atmospheric pressure for at least 1 hour and generally not exceeding about 48 hours. This step is critical in achieving the desired silica-zirconia composite upon which a platinum metal s subsequently deposited. In accordance with such step, the hydrogel is suitably covered with an acidic solution to maintain the pH of the hydrogel during activation within the approximate range of 1 to 5 and preferably 1 to 3. While the hydrogel after treatment to reduce its pH of formation as described may be transferred or conducted to an aqueous medium maintained at the elevated temperature specified hereinabove, it is generally preferred to effect activation of the hydrogel in the same solution used for reduction of pH. Thus, it is contemplated that in a preferred operation the silicazirconia hydrogel after formation at a pH in excess of 6.is conducted to an aqueous dilute solution of an acid or acid salt wherein the pH of the hydrogel is immediately brought to below 5 and the hydogel is thereafter maintained in such solution at a temperature of between 150 and 220 F. for a suflicient period to accomplish the desired activation. The pH of the hydrogel during the activation treatment is an important factor having a direct bearing on the ultimate catalyst properties and, in accordance with the process of catalyst preparation described herein, should be less than 5 and preferably below 3 in order to obtain a catalyst of high selectivity. After the activation treatment, exchangeable or zeolitic impurities, if present, are removed from the hydrogel in any feasible manner. While, as a practical matter. all or a large proportion of such zeolitic impurities may be removed during the course of the activation treatment with the aqueous medium containing an acidic compound, any remaining zeolitic matter is suitably removed by base-exchanged with aqueous solutions of mineral acids such as hydrochloric and sulfuric acids; solutions of ammonium salts which act to replace metal impurities with ammonium which is later removed by calcining; and solutions of multivalent metal salts particularly a zirconium salt which may be the same or a different zirconium salt from that employed in initial formation of the hydrogel. When base exchanging the silica-zirconia hydrogel with an acid a limited and controlled amount must obviously be used to avoid redissolving the zirconia. When exchanging with ammonium compounds any excesses will be calcined out in the final steps of catalyst manufacture and when using any zirconium or other multivalent metal salt which does not adversely affect the catalytic properties, excesses may be used and left on the composite.
After removal of zeolitic impurities the hydrogel is washed free of soluble excess ions. The resulting composite of silica and zirconia is dried in air or superheated steam at temperatures between about 200 and about 400 F. for a period of between about 4 and 24 hours and/or by calcining at a temperature between about 800 and about 1800 F. for approximately 2 to 8 hours or more.
In some instances, it may be desirable to introduce into the silica-zirconia hydrosol a quantity of solid powdered material insoluble therein having a weight mean particle diameter of between 1 and 5 microns and preferably between 2 and 4 microns. The amount of powdered material so introduced is generally between about 2 percent and about 40 percent by weight and preferably between about 15 and 40 percent by weight of the dried gel product. The powder-containing silica-zirconia sol sets to a hydrogel after lapse of a suitable period of time and the resulting hydrogel is processed as described above and then dried to a gel at a temperature below the fusion point of the incorporated powder. It has been found that a silica-zirconia gel resulting from the setting of a sol containing powdered material of the aforementioned particle size and drying of the resulting hydrogel at a temperature below the fusion point of the added material has a substantially greater resistance to attrition and improved diffusivity as compared with the corresponding silica-zirconia gels which do not contain such added powder. The powdered material may be added by dispersing in an already prepared hydrosol or as is preferable, when the hydrosol is characterized by a short time of gelation, the powder may be added to one or more of the reactants used in forming the hydrosol or may be mixed in the form of a separate stream with streams of the hydrosolforming reactants in a mixing nozzle or other means where the reactants are brought into intimate contact. In addition to having the above particle size, the powdered solid incorporated into the silica-zirconia hydrosol should necessarily be insoluble therein and should further be characterized by being infusible at the hydrogel drying temperature. The powder incorporated in the silica-zirconia sol may be catalytically active or an inert material. As indicated hereinabove, the particular powdered material to be incorporated in the hydrosol will be chosen so as to be insoluble therein and to be infusible at the drying temperature. Observing these features, suitable representative materials having a weight mean particle diameter of 1 to 5 microns include gels or gelatinous precipitates such as those of silica, alumina, magnesia, chromia, molybdena, zirconia, thoria, titania and the like including composites thereof. Thus, a particularly prepared powdered material for incorporation in the sol includes pulverized silica-zirconia fines having a weight mean particle diameter of 1 to 5 microns. Other suitable materials include zircon sand (zirconium silicate) as well as other metal silicates, metals and metal 6 oxides including aluminum oxide, chromium trioxide, molybdenum oxide, magnesium oxide, manganese oxide, zirconium oxide and silicon oxide in their various forms and modifications.
The silica-zirconia gel base may be prepared in any desired mechanical form according to the specific purpose for which it is intended. Either before or after calcination, it can be broken into lumps or granules or it can be ground to a fine powder adapted for use in the suspensoid or fluidized-solids process. Alternatively, the catalyst can be formed into pills, pellets or other suitable shapes preferably prior to the calcination step for use in the fixed bed or compact moving bed opera tions. In this case, the catalytic mixture is partially dried, ground to a powder preferably smaller than 30 mesh (Tyler), combined with a suitable lubricant such as graphite, hydrogenated coconut oil, stearic acid, rosin or the like and shaped by extrusion, molding or by other means known in the art. Particles having dimensions ranging from about Ms" x A2" to Mr" X /2 are generally satisfactory. The shaped particles can then be further dried and/or calcined as described above.
It is particularly desirable to prepare the silica-zirconia gel base in the form of spheroidal bead-like particles. For such purpose, the initially prepared hydrosol is introduced in the form of globules to a water-immiscible fluid such as into a column of water-immiscible liquid, for example an oil medium wherein the globules of hydrosol set to spheroidal bead-like particles of hydrogel. Larger size spheres are ordinarily within the range of from about 6 to about /2" in diameter, whereas smaller size spheres which are generally referred to as microspheres are within the range of from about 10 to about microns in diameter. The use of spheroidal shaped gel particles is of particular advantage in hydrocarbon conversion processes including the moving catalyst bed process, the fluidized process and other processes in which the spheroidal catalyst particles are subjected to continuous movement. As applied to the stationary bed, spheroidal catalyst particles provide effective contact between the reactants and the catalyst by avoiding channeling.
The conventional cracking activity of a catalyst is generally expressed in terms of the percent by volume of a standard hydrocarbon charge which is cracked under specific conditions in the CAT-A test. The method of this test is described in National Petroleum News 36, p. PR 537 (August 2, 1944), and the cracking activity so determined is referred to as the activity index (A.I.). Accordingly, it will be understood that the term activity index when employed herein shall refer to the cracking activity of the material under consideration determined in accordance with the CAT-A method. The activity index of the above-described silica-zirconia composites utilized herein as supports for a platinum metal is preferably within the range of about 25 to about 50.
The above prepared silica-zirconia cogel is then composited with a catalytically effective amount of a platinum metal, i.e. platinum, palladium, rhodium, osmium, iridium and ruthenium as well as alloys of these metals. Of .the foregoing, platinum and palladium and, in particular, platinum are accorded preference. The amount of platinum metal contained in the present catalyst is generally between about 0.05 and about 5 percent by weightand, more particularly, between about 0.1 and about 2 percent by weight. The platinum metal may be deposited on the silica-zirconia composite in any suitable manner. One feasible method is to admix particles of the particularly prepared silica-zirconia cogel with an aqueous solution of an acid of the metal, for example, chloroplatinic or chloropalladic acid or the ammonium salt of the acid of suitable concentration. It will be understood that any other suitable source of platinum metal may be used. Chloroplatinic acid generally is preferred because it is more readily available. Solutions of other feasible platinum containing compounds include those of platinum ammine chlorides, trimethylbenzyl ammonium platinum chloride, tetraaminoplatino chloride, platinum amine nitrate, dinitro diamrnino platinum and the like. The particles of silicazirconia impregnated with a platinum metal compound is then dried and treated with hydrogen at elevated temperatures to reduce the platinum metal compound to the metal and to activate the catalyst.
The process of this invention may be carried out in any equipment suitable for catalytic operations. The process may be operated batchwise. It 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 fiow may be concurrent or countercurrent to the catalyst flow. A fluid type of operation wherein the catalyst is carried in suspension in the hydrocarbon charge is well adapted for use with the present catalyst.
Reforming, in accordance with the present process, is generally carried out at a temperature between about 700 F. and 1000 F. and preferably at a temperature between about 800 F. and about 975 F. The pressure during reforming is generally within the range of about 100 to about 1000 pounds per square inch gauge and preferably between about 200 and about 700 pounds per square inch gauge. The liquid hourly space velocity employed, i.e. the liquid volume of hydrocarbon per hour per volume of catalyst is between about 0.1 and about and preferably between about 0.5 and about 4. In general, the molar ratio of hydrogen to hydrocarbon charge employed is between about 1 and about and preferably between about 4 and about 12.
Hydrocarbon charge stocks undergoing reforming in accordance with this invention, comprise mixtures of hydrocarbons and, particularly, petroleum distillates boiling within the approximate range of F. to 450 P. which range includes naphthas, gasolines and kerosene. The gasoline fraction may be a full boiling range gasoline. It is, however, preferred to use a selected fraction, such as naphtha having an initial boiling point of between about 150 F. and about 250 F. and an end boiling point of between about 350 F. and about 425 F.
The following examples will serve to illustrate the invention hereinabove described without limiting the same:
Example 1 demonstrates reforming with a catalyst consistent with the teachings of the invention, while Example 2 involves use of a diiferent platinum silica-zirconia catalyst. The differences relate to the method of preparing the silica-zirconia bases. In Example 1, the silicazirconia base was formed above 6 pH and activated in hot aqueous acid while in Example 2, the silica-zirconia base was prepared by forming at 3.6 pH and activated in an aqueous medium. The details of such examples are set forth below:
EXAMPLE 1 A catalyst of platinum on silica-zirconia was prepared by impregnating a silica-zirconia cogel containing 11.9 percent by weight ZrO (on a dry basis), formed at 8.2 pH and activated in 2 percent by weight aqueous solution of H 80 for 20 hours at 200 F., with chloroplatinic acid to yield 0.35 percent by weight platinum on the finished catalyst.
The silica-zirconia base in this example was prepared by mixing the reactants continuously through a nozzle in the ratio of 388 cc. per minute of an aqueous solution of zirconium sulfate [Zr(SO .4H O] containing .027 g. ZrO /cc. with 412 cc. per minute of diluted N-Brand aqueous sodium silicate solution containing .209 gram SiO /cc. to yield a silica-zirconia hydrosol having a pH of 8.2 which set to a hydrogel in 2.6 seconds at 51 F. The sol was formed into spheroidal hydrogel beads by introducing globules of the sol into an oil medium. The resulting hydrogel beads were aged in water for 4 hours at room temperature. Thereafter they were treated 20 hours at 200 F. in 2 percent aqueous H solution which reduced the hydrogel pH to 2.3. The acid-activated hydrogel was thereafter base-exchanged with a 2 Weight percent aqueous solution of ammonium sulfate solution, utilizing a total of eight 2 hour treatments. The baseexchanged hydrogel beads were then washed free of watersoluble salts and dried at 250-300 F. in steam.
A portion of the dried silica-zirconia product was then calcined for 5 hours at 1600 F. with a dry air flow through the gel of 3 volumes/volume of gel/minute. The calcined product contained 11.9 percent by weight zirconia (ZrO and remainder silica (SiO This silicazirconia cogel was characterized by an activity index of 41.
The calcined beads were vacuum impregnated with chloroplatinic acid solution, containing 0.7 percent by weight platinum to yield a catalyst containing 0.35 percent by weight platinum. The resulting impregnated catalyst was wet aged 16 hours at 240 F. in a covered container so that very little loss of water occurred. The aged particles were thereafter drier at 240 F., tempered in nitrogen to 450 F., tempered in hydrogen while heating from 450 F. to 950 F., held at 950 F. for 2 hours in hydrogen, and fin ally cooled in nitrogen.
EXAMPLE 2 The catalyst of this example was prepared by impregnating a silica-zirconia cogel containing 11.0 percent by weight ZrO (on a dry solids basis), formed at 3.6 pH and activated in water at F. with chloroplatinic acid to yield 0.55 percent by weight platinum on the finished catalyst.
The silica-zirconia base was prepared by mixing 1200 cc. aqueous zirconium sulfate solution containing 0.05 g. ZrO /cc., 248 cc. 50 percent by weight sulfuric acid, 5752 cc. of water and 2800 cc. of diluted N-brand sodium silicate solution containing 0.193 g. SiO /cc. to yield a silicazirconia hydrosol. The resulting hydrosol having a pH of 3.6 gelled in 4 to 5 hours at a room temperature of approximately 70-77 F. This hydrogel, after standing for 16 hours at the above room temperature, was cut into cubes and then activated by contacting with water for 24 hours at 175 F. The activated hydrogel was thereafter dried at 240 F. and then base-exchanged with a 2 weight percent aqueous ammonium chloride solution. The baseexchanged hydrogel was then water-washed free of chloride ion, dried for 24 hours at 275 F. in air and calcined 10 hours at 1000 F. in air. The silica-zirconia gel base so obtained was characterized by an activity index of 43, a surface area of 490 m. g. and a weight composition of 0.06 percent Na; 0.09 percent S0 11.0 percent ZrO, and remainder SiO :Platinum was deposited on the above silica-zirconia base by vacuum spray impregnating 107 grams of such base with 9.94 cc. of H PtCI solution, containing 0.096 g. Pt./cc., diluted to 87.5 cc. with Water. The resulting impregnated catalyst was wet aged 16 hours at 230 F. in a covered container so that very little loss of water occurred. The aged particles were thereafter reduced with hydrogen for 2 hours at 450 F. and 2 hours at 950 F. The finished catalyst contained 0.55 weight percent platinum and 0.17 Weight percent chlorine.
The above catalysts of Examples 1 and 2 were tested for reforming Mid-Continent type 200-380 F. ASTM boiling range naphtha utilizing a space velocity of 2 volumes per hour per volume of catalyst, a pressure of 500 p.s.i.g., a hydrogen to hydrocarbon mol ratio of 10, and a reactor inlet temperature of about 940 F. Selectivity of the catalyst was evaluated by analysis of the reforming products. The results of such testing are set forth in Table I hereinbelow. Referring to this table, the superiority of the catalyst of Example 1 over that of Example 2 is clearly evident from the respective yields of 10 RVP gasoline, C gasoline and C and lighter gas. Thus, reforming utilizing the catalyst of Example 1 aiforded 2.7 percent volume more 10 RVP gasoline than realized with the catalyst of Example 2. Further, with the catalyst of Example 1, there was obtained, 2.8 percent volume more C gasoline and 1.6 percent weight less C and lighter gas than realized from reforming with the catalyst of Example 2. Such data clearly demonstrate the advantages of high pH forming and low pH activation over low pH forming an activation of the hydrogel in water. Thus, the silica-zirconia base prepared at low pH and activated at such pH in water, after impregnation with platinum, resulted in a catalyst having a much poorer selectivity than catalyst wherein the silica-zirconia cogel base was prepared at a pH in excess of 6 and activated at a low pH.
Examples 3, 4 and 5 illustrate, for purposes of comparison, catalysts wherein the platinum is deposited on a silicaalumina base.
EXAMPLE 3 A commercial silica-alumina cogel cracking catalyst containing about 10 percent by weight alumina, having an activity index of 46 and a surface area of 432 m. g. was impregnated with 0.25 percent by weight of platinum by contacting with a 0.0305 molar chloroplatinic acid solution (200 cc. solution/ 225 cc. silica-alumina gel). Excess solution was drained oflF. The resulting impregnated catalyst was then processed as described for the catalyst of Example 1.
EXAMPLE 4 EXAMPLE 5 The catalyst of this example was a commercially available reforming catalyst containing 0.55 weight percent platinum deposited on a silica-alumina base containing 13 percent by weight alumina and remainder silica.
The catalysts of Examples 3, 4 and 5 were evaluated for reforming under the conditions noted hereinabove and the results together with those obtained for the catalysts of Examples 1 and 2 are shown in Table 1 below:
Table 1 Example 1 2 3 4 5 Activity Index of Base Platinum, Percent Wt... Charge Naphtha Properties:
Gravity, API 113? ASTM Dist Paraflins, Percent Wt Reforming Products:
10 RVP Gasoline, Percent Vol. chg 05+ Product, Percent Vol. chg Total C Percent Vol. ehg 7 Total Percent Vol. chg-- 8. (3 Lighter, Percent Wt 6 0 Product Octane Number, F-l
(+3 rnl. TEL) It will be seen from the above data that reforming with the catalyst of Example 1, illustrative of the invention resulted in a much more selective and better product distribution than achieved with the catalyst of EX- amples 3-5 wherein platinum was deposited on a silicaalurnina support. Thus, there was obtained utilizing the process of the invention, approximately 6.5 to 17.5 percent volume more 10 RV P gasoline and approximately 2 to 5 percent volume more 0 gasoline than obtainable under comparable reforming conditions with presently available platinum on silica-alumina reforming catalysts.
It will be understood that the above description is merely illustrative of preferred embodiments of the invention of which many variations may be made by those skilled in the art without departing from the spirit thereof.
1. In a process for reforming a petroleum distillate boiling within the approximate range of 60 F. to 450 F. by contacting the same under reforming conditions with a catalyst consisting essentially of between about 0.05 and about 5 percent by weight of a platinum metal deposited on a base of silica and zirconia prepared by reacting a water-soluble zirconium compound and an alkali metal silicate to effect formation of a gelable sol of silica and zirconia having a zirconia content, on a dry basis, of between about 2 and about 20, permitting said sol to set forming a silica-Zirconia gel, washing the resulting gel free of soluble matter, drying and calcining, the improvement which comprises initially forming said gel at a pH in excess of 6, subsequently reducing the pH of the gel to below 3 by contacting with an aqueous acidic solution and maintaining the gel in said aqueous solution at a temperature between about and about 220 F. for at least about 1 hour under conditions of substantially atmospheric pressure.
2. The process of claim 1 wherein said improvement comprises initially forming the silica-zirconia gel at a pH Within the range of 6 to 10, subsequently reducing the pH of the gel to below 3 by contacting with an aqueous solution of a mineral acid and maintaining the gel in said aqueous solution at a temperature between about 150 F. and about 220 F. for at least about 1 hour under conditions of substantially atmospheric pressure.
3. The process of claim 1 wherein said improvement comprises initially forming the silica-zirconia gel at a pH in excess of 6, subsequently reducing the pH of the gel to below 3 by contacting-with an aqueous acidic solution and maintaining the gel in said aqueous solution at a temperature between about and about 220 F. for a period of between about 2 and about 24 hours under conditions of substantially atmospheric pressure.
4. The process of claim 1 wherein said improvement comprises initially forming the silica-zirconia gel at a pH Within the range of 6 to 10, subsequently reducing the pH of the gel to within the range of l to 3 by contacting with an aqueous acidic solution and maintaining the gel in said aqueous solution at a temperature between about 150 and about 220 F. for a period between about 1 and about 48 hours under conditions of substantially atmospheric pressure.
Haensel et al Aug. 16, 1949 Bates et a1. Jan. 1, 1952