US2964462A - Cracking process employing a noble metal, aluminum halide and alumina catalyst - Google Patents

Description

United grates Owen H. Thomas, Chicago, Ill., and Carl D. Keith, Summit, N.J., assignors to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Filed Jan. 31, 1958, Ser. No. 712,304

4 Claims. (Cl. 208-108) This invention relates to a process for selectively cracking hydrocarbon materials using a catalyst which includes a noble metal and an aluminum halide Friedel- Crafts component supported on gamma alumina. More particularly, this invention is concerned with a process for selectively cracking hydrocarbon materials predominating in the C to C parafiinic materials in the vapor phase using the specified catalyst.

The low octane value of hydrocarbon materials predominating in C to C parafiinic materials, usch as Udex rafiinate hydrocarbons, suggests the desirability of converting this parafi'lnic material to higher octane components, particularly when considering the low octane factor along with the refractory nature of the material which makes normal reforming operations with it somewhat difficult. However, this material can be utilized in producing iso C and C hydrocarbons which are of higher octane and thus more usable in gasoline, and which may be alkylated to valuable C and C gasoline octane improver components.

In recent years automobile manufacturers have steadily increased the compression ratios of their spark-ignition engines as a means of obtaining more power and greater efiiciency. As the compression ratios of the engines increase, the hydrocarbon fuel employed must be of higher octane rating to provide efficient knock-free operation notwithstanding that fuel octane rating can be increased through the addition of tetraethyl lead, and other undesirable aspects of engine operation, for instance pre-ignition, can be overcome by the use of other additive components. Thus the problem remains for petroleum refiners to produce higher octane base hydrocarbon fuels under economically feasible conditions.

These refiners now have installed a substantial number of units for reforming straight run petroleum fractions in the presence of free hydrogen and over a platinum metal-alumina catalyst to obtainrelatively high oc Primarily, these products, frequently tane products. called reformates, are blended with other gasoline com ponents such as thermal and catalytically cracked gasolines, alkylate, etc., and additives such as tetraethyl lead in obtaining present-day motor fuels. The reforming operation has a number of disadvantages. First, as the octane requirements of the blended engine fuels rise, the octane quality of the reformate must also increase if the blends be otherwise unaltered. This increase results in a substantial reduction in yield particularly in obtaining reformates having octanes (RON neat) of the order of 90 to 95 or above. When the severity of the operation is increased the platinum metal-containing catalyst becomes fouled more often with carbonaceous deposits which requires more frequent regeneration or replacements. The platinum metal-alumina catalysts are relatively expensive, and either replacement or withdrawal from use during regeneration materially increases the atent-O ce cost of providing a given volume of reformate. These and other factors affecting the yield-octane number-cost relationship make it desirable for the refiner to consider various ways in which high octane hydrocarbon fuel components can be obtained by employing processing methods other than the platinum metal-alumina cata-- lyst reforming operation.

The selective cracking process of the present invention is a vapor phase reaction of hydrocarbon materials containing a predominant amount of C to C parafiins in' the presence of hydrogen, hydrogen halide and a catalyst including a noble metal, aluminum halide and activated.

alumina. Hydrocarbon materials suitable for treatment in our process are the highly paraflinic-containing hydrocarbon materials predominating in C to C parafiins' and include raffinates procured from the S0 extraction of reformates or fiuid gasoline; however, frequently a hydrocarbon material predominating in C to C paraffins such as a Udex rafiinate, for example, is employed. A suitable Udex raflinate is a paraffin-rich feed separated from the effluent of reforming systems through the use of a glycol-water extraction medium which is employed commercially. As commercially licensed, this general system is known as Udexing. By regulation of conditions:

percent of C to C paraffinic materials and usually at. least about weight percent of C to C paraffinic materials.

The vapor phase cracking is effected in the presence ofa noble metal-aluminum halide Friedel-Crafts-gammaalumina catalyst. This catalyst generally includes metal,

an aluminum halide Friedel-Crafts component and, at least ultimately in the cracking system, a hydrogen halide,-

The

all of which are supported on an alumina base. base is usually the major component of the catalyst, constituting about 40 to weight percent, preferably at least about 50%. gamma-alumina such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures. The catalyst base precursor most advantageously is a mixture predominating, for instance about .65 to 95 weight percent, in one or more of the alumina trihydrates bayerite I, bayerite'II (randornite) or gibbsite. and about 5 to 35 weight percent; of alumina monohydrate (boehmite), amorphous hydrous;

alumina or their mixture. The alumina base can contain small amounts of other solid oxides such as silica, mag-- nesia, boria, natural or activated clays (such as kaolinite, montmorillonite, halloysite, etc.), titania, zirconia, etc., or their mixtures.

- The catalyst generally contains about 0.01 to 2 weight percent, preferably 0.1 to 0.75 weight percent, of one or" more of the platinum metals of group VIII, that is platinum, palladium, rhodium, ruthenium, osmium or iridium. The small amount of noble metal may be present in the metallic form or as a sulfide, oxide or other combined form. The metal may interact with other constituents of the catalyst, but if during use the noble metalbe present in metallic form then it is preferred that it be so finely divided that it is not detectable by X-ray diffrac tion means, i.e. that it exists as crystals of less than 50 Patented Dec. 13, 1960 The catalyst base is an activated or- Angstrom. units. size... preferred.

The aluminum halide Friedel-Crafts component usually is about 2 to 50 weight percent, preferably about to 30 weight percent, of the catalyst and this component can be, for instance, AlCl AlF AlBr and similar metal halides where one or more of the. anions. are replaced with; another anion such as hydroxide. Mixtures. of these Friedelecrafts components can also be used; aluminum chloride is, however, the. preferred Friedel-Crafts component.

Another component of the catalyst may be a. hydrogen halide and the catalyst may advantageously contain about 0.5 to or. more of a hydrogen halide. The hydrogen halides include, for instance, hydrogen chloride, hydrogen bromide, hydrogen. fluoride and their mixtures. and preferably the amount of this component on the alumina base. is. less. than about 10% of. the catalyst- Although the. components of. the catalyst can vary, as illustrated above, the preferred catalyst employed in the cracking processv contains platinum, aluminum chloride and, at least ultimately in the cracking system, hydrogen halide deposited on activated alumina.

The. preferred base or supporting material is an activated, or gamma-alumina made by calcining a precursor predominating in alumina trihydrate. An alumina of this type is. disclosed in application Serial. No. 288,058,. filed May 15, 1952, now abandoned, and its continuation-inpart application Serial No. 489,726, filed February 21, 1,955 how U.S. Patent No. 2,838,444. The alumina base is derived from a precursor alumina hydrate composition containing about 65 to 95 weight percent of one or more, of the alumina trihydrate forms gibbsite, bayerite I and bayerite II (randomite) as defined by X-ray diffraction analysis. The substantial balance of the hydrate is amorphous hydrous or monohydrate alumina. Trihydrates are present as well-defined crystallites, that is they are crystalline in' form when examined by X-ray diffraction means. The crystallite size of the precursor alumina trihydrate is relatively large and usually is in the 100 to 1000 Angstrom unit range. The calcined alumina has a large portion of its pore volume in the pore size range of about 100 to 1000 Angstrom units generally having about 041 to about 0.5 and preferably about 0.15 to about 0.3 cc./ g. of pore volume in this range. As described in these applications the calcined catalyst can be characterized by large surface area ranging from about 350 to about 500 or more square meters/gram when in the virgin state as" determined, for example, by the BET adsorption technique. A low area catalyst prepared by treating the predominantly trihydrate base precursor is described in application Serial No. 581,250, filed April 27, 1956, now- ULS; Patent No. 2,838,445. This base when in the virgin state has substantially no pores of radius less than 10 Angstrom units and the surface area ofthe catalyst is less than 350 square meters/gram and most advantageously is in the range of about 150 to 300 square meters/gram.

The catalyst can be advantageously prepared in accordance with a process described in copending application Serial No. 712,315, filed January 31, 1958. According to this process, the aluminum halide Friedel- Crafts catalyst is added to a noble rnetal-gamma-alumina composition. The noble metal-gamma-alumina composition can be preparedby known procedures. For instance, the platinum metal component. can be deposited on. a calcined or activated alumina, but it is preferred to add the platinum metal component to the alumina hydrate base precursor. Thus platinum can be added through reaction of a halogen platinum acid, for instance, fluoro-, chloro-, bromoor iodo-platin'c acid, and hydrogen. sulfide in an aqueous slurry of the alumina hydrate. The hydrogen sulfide can be employed as a gas'oran aqueous solution. Alternatively, the platinum component can be provided by mixing an aqueous plati- Of the noble. metals, platinum. is.

num sulfide solwith. the alumina hydrate. This sol can be made by reaction in an aqueous medium of a halogen platinic acid with hydrogen sulfide. The alumina hydrate containing the platinum metal can be dried and calcined usually at a temperature from about 750 to 1200 F. or more to provide the activated or gammaalumina modifications. The addition of the Friedel- Crafts component to the high area catalyst bases of applications Serial Nos. 28.8,058 and 489,726. has been found to. decrease the surface area, for instance, directionally related to the amount of Friedel-Crafts component added. Use of the catalyst in the cracking system increases the area apparently through loss of the Friedel-Crafts component.

The aluminum halide Friedel-Crafts component can be added to the noble metal-alumina composition in vapor form in a flowing gas such as nitrogen, for example; however, we prefer to place the aluminum halide Friedel- Crafts component in vapor form on the platinum-alumina composition by placing the Friedel-Crafts component and the noble metal-alumina composition in a common vessel provided with some means for agitating the mixture of materials, applying heat and agitating. the mixture to produce the catalyst.

A hydrogen halide component can be added to the noble metal-aluminaraluminum halide composite by supplying the hyd'rogcn halide as. such or by employing an. organo-halogen compound or other substance which will produce the hydrogen halide. The hydrogen halidev can be added to. the composite by contacting the composite directly with hydrogen halide. When using the catalyst in a conversion process, however, such as the cracking of C to C paraffinic-containing hydrocarbon materials, the hydrogen halide can be added to the noble metal-aluminum halide-alumina composite after it is placed in the cracking reactor. Conveniently this is done by including in the paraffinic feed about 0.05 to 35 weight percent, advantageously about 0.5 to 5 weight percent of the hydrogen halide or of a hydrogen halide-producing material. The addition of the hydrogen halide in these concentrations based on the parafiin is continued over the processing period in order to maintain an adequate concentration of this component on the alumina base and insure the stability of the catalyst against undue aging. The hydrogen halide can be added separately to the reaction system, in the hydrogen-containing recycle gases or in the paraffin feed stock. Also, as pointed out above, the hydrogen halide on the alumina base might be added to the catalyst before charging; it to the reactor.

When using an organo-halogen compound or other substance as the hydrogen halide supplier, they can also be employed to conveniently supply the hydrogen halide to the catalyst composite under conditions to which the catalyst may be subjected. Suitable hydrogen halide precursors include. the elemental halogens, chlorine, bromine and fluorine; monoand polyhalo-alkanes such as carbon tetrachloride, chloroform and tertiary butyl chloride; or other available materials which will be converted under the conditions of the process in which the catalyst is used, for instance when under cracking conditions of free hydrogen and temperatures of about 200 to 450 F. to obtain the hydrogen halide.

The cracking reaction conditions used in the method of' the present invention include a temperature suflicient to maintain the hydrocarbon paraffiuic feed in the vapor phase under the pressure employed and the use of a low molecular weight diluent, such as isobutane may be necessary to assure this. Generally, this temperature will be from about 200 F. to 450 F, preferably from about'250 to 350 F., while the pressure Will be superatmospheric ranging from about to 1000 p.s.i.g., preferably from about 200 to 500 p.s.i.g. The catalyst can be used as a fixed, moving or fluidized bed or in any other convenient type of handling system. The rod bed system seems most advantageous at this timeand the lent to approximately 65 grams of Al O per liter. separate deionized water solution of NH OH is prepared space velocity will in most cases be from about 0.5 to :1 weights of paraflfin per weight of catalyst per hour (WHSV).

Free or molecular hydrogen must be present in our reaction system and the hydrogen to paraffin molar ratio will usually be from about 5 to 50:1 or more, preferably about 5 to :1. Conveniently, the hydrogen concentration is maintained by recycling hydrogen-rich gases from the reaction zone. These gases contain hydrogen halide at least after the initial processing period and as there is usually no substantial consumption of the halide after this period the desired concentration in the feed can be maintained merely by recycling the hydrogencontaining gases, for instance, the hydrogen halide can with advantage be introduced in a hydrogen halide to paraflin molar ratio generally of from about 0.1 to 10 and preferably from about 0.3 to 2.0.

A convenient manner in which the catalyst of the present invention can be prepared is to add the Friedel- Crafts component to the base containing the platinum metal component. It is highly desirable to keep the catalyst protected from moisture to avoid hydrolysis and deactivation of aluminum halide. Thus it is most advantageous to employ this catalyst under essentially anhydrous conditions including the provision of the hydrogen halide in anhydrous form. During regeneration of the catalyst to remove carbonaceous deposits by burning in an oxygen-containing gas, some aluminum halide may be lost. Thus, it may be necessary to add additional amounts of this halide as by sublimation before continuing the cracking.

Even though we prefer to employ our catalyst directly in the cracking system, it can be pretreated with free or molecular hydrogen or a mixture of hydrogen and hydrogen halide. For example, the catalyst can be heated to about 650 F. in a slowly flowing stream of hydrogen or hydrogen-hydrogen chloride mixture for a period of time suflicient to activate the catalyst. It may be desirable to employ lower temperatures in the pretreatment to avoid undue loss of aluminum halide by sublimation even though this may decrease the rate of activation. After the activation the pressure can be increased as desired and the parafiin feed charged to the reaction system. Generally, the activity of the catalyst increases during the initial portion of operation and then holds a high level of activity for long processing periods, thus exhibiting good life or resistance to aging. It seems possible that upon the addition of the paratfin feed the catalyst is comprised of the noble metal and a complex of the Friedel-Crafts component, the parafiin and the hydrogen halide supported on the alumina base.

The following specific example will serve to illustrate the invention but it is not to be considered limiting.

EXAMPLE I A noble metal-alumina composition of the kind described in application Serial No. 489,726, filed February 21, 1955', can be employed in the process of our invention. The catalyst of this application can be made as follows. Pure aluminum metal is dissolved in pure hydrochloric acid, and the resulting solution is mixed with deionized water to form an aqueous aluminum chloride solution and an alumina gel is prepared equivacontaining approximately 65 grams of ammonia per liter. These two reagents in approximate volume ratio of 1:1 are intimately mixed as a flowing stream at a pH of 8.0. The flowing stream is passed to a stoneware container and an aluminum hydrate is visible. The precipitated hydrate is filtered from the mother liquid and washed to O.2% chloride by successive filtrations connected from the air line.

comprised of 42% bayerite, 18% randomite, 11% gibb site, 20% boehmite, and 9% amorphous as determined by X-ray diffraction analysis. The aged hydrate is mixed with deionized water in a rubber-lined container to provide a slurry of about 7 weight percent A1 0 at a pH of about 8.0. A chloroplatinic acid solution of deionized water (0.102 gram patinum per milliliter) is stirred into the slurry and the slurry is then contacted with a deionized water solution which has been saturated with H 8 at 78 F. to precipitate the platinum. The pH of the slurry is adjusted to 6.0 to 6.5 by ammonium hydroxide addition and the solids of the slurry are dried on a horizontal drum drier to give a powder of generally less than 20 mesh. The drum dried powder is mixed in a planetary type dough beater with sufficient deionized water to indicate 26 weight percent water on a Central Scientific Company Infra-red Moisture Meter containing a watt bulb, Cat. No. 26675. The resulting mixture is forced through a die plate having holes in diameter bolted to a 3 /2" Welding Engineers screw extruder. The resulting strands are broken to particles of length varying generally between about to 1".,

The particles are dried at 230 F. and calcined by heating to 925 F. in a flow of nitrogen gas followed by a flow of air while the catalyst is maintained at a temperature in the range of 865 to 920 F. The composition thus produced analyzes about 0.6 weight percent ofplatinum which is in sufliciently divided form so as to exhibit by X-ray diflraction studies the substantial absence of crystallites or crystals of size larger than 50 Angstrom units. After the calcination the composition has an area (BET method) within the range from about 350 to 550 square meters/gram.

A platinum-alumina composition prepared essentially as described above, except that air was used for the complete calcination procedure and containing about 0.6% platinum was employed in the process of the present invention by the following procedure. A one-liter, threenecked flask was fitted with a heating mantle, thermometer and an air inlet line having a drying tower filled with Drierite. The flask was fastened to a Syntron Paper Jogger which provided agitation of the catalyst during the impregnation. The flask was swept out with dry air for about 10 minutes. grams of the platinumalumina composition and 45 grams of aluminum chloride were charged to the flask. The air was turned off, the fiask was stoppered and the drying tower was dis- Heating of the flask was begun and the temperature of the mixture was brought slowly to approximately 445 F. in about three hours. The heat was turned off and the catalyst was cooled and transferred to a moisture-tight container. The resulting catalyst contained 19.3 weight percent aluminum chloride based upon the platinum-alumina catalyst.

Hydrogen chloride is added to the platinum-aluminum halide-alumina composite using a carbon tetrachloride 1 precursor while employing the catalyst in the cracking process. This procedure is illustrated by the following. The run was made in a 1' ID. Universal stainless steel reactor. The reactor, after each charging, was placed in a bronze-block furnace controlled by Microswitch type thermostats. Bed temperatures were measured by means of Chromel-Alumel thermocouples.

A 60 gram charge of Pt-Al O -25.0% AlCl was mixed with 276 grams of tabular alumina to form a diluted bed 7 approximately 18" in length. The catalyst bed was heated to 275 F. with the reactor pressure at which time the Udex rafiinate, 'isobutane, HC1 and hydrogen were introduced at the following feed rates:

At the completion of a two hour prerun, a run of 2% hours was made. All product was collected in a series of ice and Dry Ice traps. The total hydrocarbon feed was 293 g. and the liquid recovery was 274 grams. The hydrocarbon collected in the dry gas brought the product recovery based on feed to 100%. Product was analyzed for each component through mass spectrography and vapor phase chromatography analyses. The weight percent conversion of Udex raffinate to hydrocracked product containing normal and isobutane, normal and isopentane, normal and isohexane, normal and isoheptane, and propane was 77.2%.

Both the noble metal and aluminum chloride are necessary in defining this catalytic hydrocracking system. The platinum-alumina composition alone becomes active for hydrocracking operations only at temperatures considerably higher than those employed in this process. The need for a noble metal is indicated by comparing runs 859-6 and 859-23 shown in Table l in which a 'Udex rafiinate (U.R.) comprised of the following is employed.

Udex rafiinate composition:

Weight percen Table Run No.. Gatalvst composition:

Wt. percent Pt"..- Wt. perc ent AlClz 3-05. 03-- i-Ca n-O i-C ll-G7 O4+selectlvity Total Wt. percent conversion discharging and the coke value for this catalyst was approximately 9%. The addition of platinum and hydrogen to this cracking medium removes the possibility of olefinic product under these operating conditions since thermodynamic equilibrium at these temperatures excludes olefin formation. This is apparent when comparing the Pt-AlCl -Al O catalyst with its AlCl -Al 0 counterpart. The presence of a hydrogenation metal such as platinum or palladium removes the possibility of aluminum chloride deactivation through its complexing action with olefinic hydrocarbons. These predictions are borne out through examination of the discharged Pt- AlCl -A1 O catalysts. No black discoloration of the catalyst is found and the corresponding coke values are quite low (0.5%). Thus the presence of hydrogen and the hydrogenation metal enhances both hydrocracking activity and catalyst life.

One of the more desirable properties of a cracking catalyst such as this is its ability to maintain high iso to normal isomer ratios in the butane and pentane reaction products. The Udex raffinate feed is high in branched hydrocarbons and the iso/normal C and C product distribution is above the thermodynamic equilibrium values. Thus our system is advantageous since the hydrocracking sequence produces the large amounts of iso C and C isomers directly in the reaction medium. When palladium is substituted for platinum the iso/ normal ratios for the cracked products are also higher than thermodynamic isomerization equilibrium values. These results are shown in Table 2.

Table 2 Run N0-" 859-7 8591-24 at lyst 1 flgZfiE- 7 5d; 24 o 3 a 0 1 1; Av. Temp, F 0 305 Press' re, p.s.i.g 300 300 WHSV based on Udcx raifinate (U 0.73 0. G9 H1IU.R. mole ratio. 10.4 12.6 i-Ci/U.R. mole ratio..- 3. 35 4. 3 Hill/UR. mole ratio" 0.14 0.35 l-Cs/l'l-C4 product ratio. 70. 0 117 i-C5/n-C prodct ratio- 31. 4 9. 2 i Ciltt-Oi eq ilibri"m 2.0 2.0 i-C5ln-C5 equilibri"m 5. 7 5. 7

Total Wt. percent com on of Udex raflinate 77. 2 69. 2

The catalvst of r n 859-7 is essenti lly the same as the catal st prepared in Example 1(8) above as is the catalyst of run 859-24 with the exception that palladium is substituted for platinum.

It is claimed:

1. A process for catalytically cracking a hydrocarbon material containing a predominant amount of C to C paraflinic materials, comprising the step of contacting the hydrocarbon material with a catalyst in a reaction zone under cracking conditions including the presence of free hydrogen and hydrogen halide in the reaction zone, and a temperature from about 200 F. to 450 F., said catalyst comprising about 0.01 to 2% of a noble metal, about 2 to 50% of an aluminum halide Friedel-Crafts component and about 40 to of an activated alumina.

2 The process of claim 1 in which the hydrocarbon material contains a predominant amount of C to C parafiinic hydrocarbons and the cracking conditions include a temperature from about 250 F. to 350 F., a pressure from about to 1000 p.s.i.g., a hydrogen to hydrocarbon molar ratio of about 5 to 50:1, and a hydrogen halide to hydrocarbon mole ratio of from about 0.1 to 10:1.

3. The process of claim 2 wherein the noble metal is platinum and is about 0.1 to 0.75% of the catalyst, the aluminum halide is aluminum chloride and is about 10 to 30% of the catalyst, and the alumina is derived by calcination of an alumina hydrate precursor consisting essentially of about 65 to 95 of alumina trihydrate and about 5 to 35% of a member selected from a group consisting of amorphous hydrous alumina, alumina monohydrate, and their mixture and the activated alumina has an area of about 350 to 550 square meters per gram.

9 4. The process of claim 3 wherein isobutane is em- 2,692,224 ployed as a diluent. 2,733,219 2,838,444 References Cited in the file of this patent UNITED STATES PATENTS 5 163 446 2,350,828 Schmerling June 17, 1942 1,013,024 2,596,145 Grote May 13, 1952 791,073

10 Heinemann Oct. 19, 1954 Bloch Jan. 31, 1956 Teter et a1. June 10. 1958 FOREIGN PATENTS Australia June 10, 1954 Germany Aug. 1, 1957 Great Britain Feb. 26, 1958

Claims (1)

1. A PROCESS FOR CATALYTICALLY CRACKING THE HYDROCARBON MATERIAL CONTAINING A PREDOMINANT AMOUNT OF C8 TO C12 PARAFFINIC MATERIALS, COMPRISING THE STEP OF CONTACTING THE HYDROCARBON MATERIAL WITH A CATALYST IN A REACTION ZONE UNDER CRACKING CONDITIONS INCLUDING THE PRESENCE OF FREE HYDROGEN AND HYDROGEN HALIDE IN THE REACTION ZONE, AND A TEMPERATURE FROM ABOUT 200*F. TO 450*F., SAID CATALYST COMPRISING ABOUT 0.01 TO 2* OF A NOBLE METAL, ABOUT 2 TO 5% OF AN ALUMINUM HALIDE FRIEDEL-CRAFTS COMPONENT AND ABOUT 40 TO 95% OF AN ACTIVATED ALUMINA.