US3337447A - Selective hydrocracking with a sulfur containing cadmium zeolite catalyst - Google Patents

Description

United States Patent 3,337,447 SELECTIVE HYDROCRACKING WITH A SULFUR CONTAINING CADMIUM ZEOLITE CATALYST James Arthur Rigney, Baton Rouge, Ralph Burgess Mason, Denham Springs, and Glen P. Hamper, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Sept. 13, 1965, Ser. No. 487,026 22 Claims. (Cl. 208-111) This invention relates to the removal of straight-chain hydrocarbons from petroleum-derived feedstocks by their selective conversion in the presence of hydrogen. More particularly, it relates to a selective hydrocracking process which is accomplished in the present of a crystalline metallo alumino-silicate having uniform pore openings less than about 6-Angstrom units in diameter, and preferably about 5 Angstroms.

Hydrocarbon conversion and upgrading with crystalline alumino-silicate zeolite catalysts is now well known in the art. For example, the use of these zeolites for hydrocracking has been generally directed to typical petroleumderived feedstocks, such as gas oil, etc., which are customarily converted to lower boiling products useful as gasoline. The crystalline zeolites employed for such purposes usually have uniform pore openings of about 6 to Angstroms and are therefore nonselective; that is, substantially all of the feed molecules are admitted into the zeolite pore structure. For many purpose-s selective hyd-rocracking of only certain molecular species is obviously to be desired. One such purpose, for example, is the octane improvement of naphtha fractions by selectively hydrocracking only straight-chain hydrocarbons (e.g., olefins, paraifins, etc.) which tend to be low octane producing, and thereafter removing the hydrocracked products and recovering a higher octane product. Another purpose is the selective hydrocracking of the straight-chain hydrocarbon content of lube oil and gas oil fractions for pour point reduction or dewaxing. The use of a nonselective large pore (e.g., 6 to 15 Angstroms) crystalline zeolite for such purposes is ineifectual, since desired feed molecules, e.g., aromatics, are admitted into the zeolite pores and hydrocracked along with the straight-chain hydrocarbons.

With specific regard to the upgrading of naphtha fractions for inclusion in the high quality motor gasoline necessary for modern automobiles, it is customary to improve the octane rating and cleanliness or gum-forming properties by means of such processes as thermal or catalytic reforming. The desired product is usually of about the same boiling range as the feed, with the molecules having been rearranged o-r reformed into higher octane-producing compounds. However, the extent of reforming of naphtha and naphtha-containing oils is usually limited owing to the formation of excessive coke as reaction temperature increases. For this reason, such processes as catalytic and thermal reforming and the like are usually designed to avoid excessive coke and dry gas make with, however, a corresponding limitation on the degree of naphtha improvement attainable. Upgrading of cleanliness of gum-forming properties is also quite important with certain olefinic naphthas, especially naphthas produced in thermal cracking or coking operations. In this case, upgrading is usually accomplished by either passing the naphtha over' a catalytic cracking catalyst or by hydrofining. Again the first of these alternates, i.e., catalytic cracking, results in an undesirable high gas and coke make; whereas the second, i.e., hydrofining, results in an octane number loss.

Attempts at solving the above problems have generally involved one or more hydro techniques, such as hydro- 3,337,447 Patented Aug. 22, 1967 cracking, hydroforming, hydrodealkylation, etc., which processes tend to form lesser amounts of coke and dry gas while at the same time resulting in improved octane prod uct. However, indiscriminate use of hydrocracking, for example, to upgrade naphthas, is often self-defeating, since products boiling below the range of the feed are formed, thereby lowering the naphtha yield. Hydroforming or catalytic reforming are also not practical with certain naphtha feeds, e.g., coker naphthas, which contain appreciable sulfur, nitrogen and diolefins, again because of excessive coke make and rapid catalyst deactivation. Also, catalytic hydroforming, which depends upon aromatics formation for octane improvements, is ineffective with feeds having low cycloparafiin concentration.

It Will again be realized, therefore, that a conversion process which is capable of selectively converting the low octane-producing components of the naphtha feed to lower boiling components which are readily removed, with -a minimum conversion of the high octane-producing components, is to be highly desired. Removal of the low octane components would thus result in enhancement of the naphtha octane number without appreciably altering its boiling range.

It has accordingly been discovered that highly effective selective removal of straight-chain hydrocarbons can be accomplished by the use of certain types of crystalline alumino-silicate zeolites having uniform pore openings of less than 6 Angstroms, preferably about 5 Angstroms. The essence of this invention resides in the surprising discovery that a particular sulfided cation form of these S-Angstrom zeolites is substantially superior to other forms. Specifically, it has been found that the S-Angstrom zeolite should be cadmium containing, preferably having a major portion of its cation content supplied by a cadmium cation, and most preferably having been ex changed solely with cadmium cation for replacement of alkali metal originally in the zeolite.

It has been specifically found that naphthas may be successfully upgraded by contacting them at suitable conditions of temperature and pressure in the presence of hydrogen with a sulfided cadmium-containing crystalline metallo alumino-silicate zeolite having uniform effective pore openings of less than 6 Angstroms, preferably about 5 Angstroms. By upgrading is meant any hydro technique resulting in the formation of an improved or preferred product. This would include improved octane rating and cleanliness, lower sulfur content, etc. The hydro techniques contemplated include such processes as hydrofining, 'hydrocracking, hydrodealkylation, hydrogen transfer, etc., with the preferred process being hydrocracking. These processes will usually be con-ducted at elevated temperature and pressure in the presence of hydrogen.

It is fully recognized that the prior art has taught the use of crystalline alumino-silicate zeolites for cracking of various petroleum and hydrocarbon materials. For example, US. Patents Nos. 2,971,903 and 2,971,904 disclose various hydrocarbon conversion processes employing crystalline alumino-silicates having uniform pore openings between about 6 and 15 Angstroms. As hereinbefore mentioned, the present invention employs crystalline aluminosilicates having uniform pore openings of less than 6 Angstroms, preferably about 5 Angstroms, which pore size has been found to be necessary and critical to the successful selective hydrocracking herein contemplated. The prior art has also recognized the possibility of se lectively converting normal parafiins by means of S-Angstrom molecular sieves for such purposes as dewaxing, etc. These uses derive from the ability of these crystalline zeolite materials to selectively admit certain sized molecules into their pores while rejecting others. Since these materials are now well-known adsorbents and catalysts, they provide highly efiicient and valuable tools for selectively converting specified constituents of a hydrocarbon feed. For example, US. Patent No. 3,039,953 discloses the selective conversion of normal paraffins with a S-Angstrom zeolite. Also, U.S. Patent No. 3,140,322 relates generally to selective catalytic conversion utilizing crystalline zeolites and mentions dehydration, catalytic cracking, hydrogenation, etc.

The essence of the present invention, which distinguishes it from the above prior art teachings, lies in the surprising discovery that certain unique S-Angstrom crystalline alumino-silicates are superior catalyst components for selective conversion reactions in general and selective hydrocracking in particular. The cadmium cation-containing S-Angstrom zeolite, with or without a metallic hydrogenation component, has a strikingly greater activity than similar catalysts based on other cationic forms of the zeolite.

A further distinction over these and similar teachings resides in the fact that the S-Angstrom crystalline alumino-silicate employed herein in the cadmium cationexchanged form can be free of any metallic hydrogenation catalyzing component and yet will surprisingly and uniquely exhibit selective hydrocracking activity. Reference to the aforementioned US. Patent No. 3,140,322, for example, indicates that the selective hydrogenation process therein disclosed was accomplished with a crystalline alumino-silicate zeolite catalyst having the usual metallic hydrogenation component, such as platinum or palladium combined therewith. Again, the catalyst used in the present invention need not include such metallic hydrogenation component and yet, surprisingly, is a highly effective hydroconversion catalyst.

The process of the invention should also be distinguished from the conventional adsorption-desorption processes which are well known in the art. The present process involves a selective hydrocr-acking of straight-chain hydrocarbons. In the naphtha octane improvement embodiment, certain low octane-producing molecules, such as straight-chain hydrocarbons, are selectively hydrocracked to gaseous materials, such as butane and lighter fractions, which are easily removed. The invention does not contemplate, therefore, a mechanical separation of diverse molecules, as accomplished by the conventional adsorption-desorption phenomenon, In the case of selective hydrocracking, converted products are not retained within the pores of the zeolite and a desorption step is unnecessary, thereby making the process economically attractive.

The crystalline metallo alumino-silicate zeolites having uniform pore openings of about Angstroms contemplated for use in this invention are well known and available in synthetic or natural form. For example, a suitable starting material, referred to as Zeolite A in US. Patent No. 2,882,243, has a molar formula (dehydrated form) of where M is a metal usually sodium and n is its valence. It may be prepared by heating a mixture containing Na O, A1 0 SiO and H 0 (supplied by suit-able source materials) at a temperature of about 100 C. for 15 mmutes to 90 hours or longer. Suitable ratios of these reactants are fully described in the aforementioned patent.

One suitable process for preparing such materials synthetically involves, for example, the mixing of sodium silicate, preferably sodium metasilicate, with sodium aluminate under carefully controlled conditions. The sodium silicate employed should have a ratio of soda to silica between about 0.8 to 1 and about 2 to 1, and the sodium aluminate may have a ratio of soda to alumina in the range of from about 1 to 1 to about 3 to 1. The amounts of the sodium silicate and sodium aluminate solutions employed should be such that the ratio of silica to alumina in the final mixture ranges from about 0.8 to 1 to about 3 to 1 and preferably from about 1.1

to about 2.1. Preferably, the aluminate is added to the silicate at ambient temperature with sufficient agitation to produce a homogeneous mixture. The mixture is then heated to a temperature of from about to about 215 F. and held at that temperature for a period of from about 0.5 to about 3 hours or longer. The crystals may be formed at lower temperatures but longer reaction periods will be required. At temperatures above about 250 F. a crystalline composition having the requisite uniform size pore openings is not obtained. During the crystallization step, the pH of the solution should be main tained on the alkaline side, at about 12 or higher. At lower pH levels, crystals having the desired properties are not as readily formed.

The products produced by the above procedure will have uniform pore openings of about 4 Angstroms as produced in the sodium form. They may then be converted to products having uniform pore openings of about 5 Angstroms by replacement of the sodium via conventional ionexchange techniques with various cations, such as calcium, magnesium cobalt, nickel, iron, manganese, etc., all of which are not suitable for purposes of this invention.

Natural zeolites having effective pore diameters less than 6 Angstroms, and preferably about 5 Angstroms, are also herein contemplated and will include such materials as erionite, chabazite, analcite, lebrynite, natrolite, etc. Thus, both the natural and synthetic varieties of 5-Angstrom zeolites are contemplated with the only limitation being one of pore size. As indicated, the pore size must be sufficient to substantially admit the straightchain hydrocarbons but insufficient to admit the valuable high octane-producing components, such as the aromatics, so as to avoid their hydrocracking. This capacity should, therefore, be demonstrated at the particular hydrocracking conditions contemplated, since the effective pore diameter of these zeolite materials often varies with temperature and pressure.

In accordance with the invention, it has been found that indiscriminate use of the above-mentioned cations is not suitable for the selective hydroconversion processes of the invention. More particularly, it has been found that the use of cadmium cation is critical. Thus, the catalyst used in the present invention is prepared from a crystalline alumino-silicate which, after cadmium cation exchange, has uniform effective pore openings less than 6 Angstroms, and preferably about 5 Angstroms, in diameter. The most preferred cation solution will be an aqueous solution of a cadmium salt, such as cadmium chloride or cadmium nitrate. The extent of ion exchange should be sufficient to reduce the alkali metal, e.g., sodium content of the zeolite to less than 10 wt. percent, and preferably less than 5 wt. percent. The ion exchange is prefer ably conducted to cause at least 25%, and more prefer ably greater than 50%, of the exchangeable cation content to be divalent by replacement with the cadmium cation. It will be understood that although the most preferred catalysts will be prepared by using cadmium cation as the sole exchanging cation, the presence of cadmium together with other exchanging cations will also be highly useful. Thus, in some of its broadest aspects, the present invention contemplates the use of about a S-Angstrom zeolite containing cadmium cation, Preferably, the zeolite will have a major portion of its cation content supplied by cadmium with perhaps minor portions of residual sodium, as well as minor portions of other ions which may also have been introduced via exchange for various purposes.

As a further option step in the preparation of the catalysts of the invention, the catalyst can be combined with an active metallic hydrogenation component which may be chosen from Groups V-B, VI-B, VII-B, or VIII of the Periodic Table and which is suitably exemplified by the metals cobalt, nickel, platinum, palladium, etc. The hydrogenation component may be in the form of the free metal as in the case of platinum group metals or as the oxide or sulfide as in the case of cobalt, etc., or mixtures of such metals, oxides, or sulfides. Platinum group metals (i.e., metals of the platinum and palladium series) will be preferred for purposes of the present invention with palladium being particularly preferred. Incorporation of the hydrogenation component may be accomplished by any conventional technique, such as ion exchange followed by reduction, impregnation, etc. When palladium is employed, the cadmium-exchanged alumino-silicate is preferably impregnated with an ammoniacal solution of palladium chloride sufficient to produce the desired amount of hydrogenation metal in the final product, and then dried and calcined at a temperature of 800 to 1000 F. Reduction of the metal is then accomplished either separately or in the hydrocracking reaction per se. The amount of hydrogenation component may range from about 0.1 to about 25 wt. percent, based on the weight of final product. In the case of platinum group metals, e.g., palladium, the preferred amount will be in the range of about 0.1 to 6, e.g., 0.5 to 3 wt. percent, based on dry catalyst.

As an additional essential feature of the present invention, it has been found that the activity and effectiveness of the catalysts used herein are critically dependent upon contact with sulfur prior to their exposure to high temperature conditions employed in the selective conversion processes described herein. The catalyst is sulfactivated by contact either with a sulfur-containing feed or, if the feed has a low sulfur content, with hydrogen sulfide or an added sulfur compound which is readily convertible to hydrogen sulfide at the hydroconditions employed, e.g., carbon disulfide, etc.

The extent of this sulfactivation treatment should be sufficient to incorporate 0.5 to 15 wt. percent sulfur into the catalyst. It has been further found that the temperature to which the catalyst is subjected during the sulfactivation step is also critical and must be maintained below about 1000 F., preferably 850 F., most preferably between about 450 and 750 F. The effect of sulfactivation will be demonstrated in the examples to follow.

The catalyst used in the present invention has been found to be highly effective for the upgrading of naphtha feeds, although the invention is not to be so limited. Markedly improved octane number is achieved with a very low loss of naphtha yield. Additionally, the coke make produced in the process is substantially lower than that experienced in catalytic cracking.

The feedstocks contemplated for use in the present invention may be any of the typical petroleum hydrocarbon feeds, containing straight-chain hydrocarbons which are desirably removed for the particular intended use of the end product. For naphtha octane improvement, the feeds contemplated include either low-boiling naphtha or high boiling naphtha-containing feeds, the latter typically having a boiling range of about 250 to 450, preferably 300 to 430 F. These feeds may be exemplified by virgin naphtha fractions, heavy coker naphtha, heavy steamcracked naphtha, heavy catalytic naphtha, and the like.

Typical hydrocracking conditions which are suitable for purposes of the present invention include a temperature of 400 to 950 F., preferably 650 to 850 F.; a pressure of 200 to 4000, preferably 500 to 2500 p.s.i.g.; a space velocity of 0.2 to 20, preferably 0.4 to 2 v./v./hr.; and a hydrogen rate of 1,000 to 10,000, preferably 1500 to 5000 standard cubic feet of hydrogen per barrel of feed.

The invention will be further understood by reference to the following examples which are given for illustrative purposes.

EXAMPLE 1 This example illustrates the preparation and use of a cadmium-containing crystalline alumino-silicate having uniform pore openings of about 5 Angstroms in the selective hydrocracking of a C 'to C naphtha feed derived from an Arabian crude. The cadmium crystalline alumino-silicate was prepared as follows:

A charge of 500 grams of commercial sodium Zeolite A having pore openings of about 4 Angstroms in diameter and a silica-to-alumina mole ratio of about 2 to 1 was air-exposed overnight and then stirred in 2500 ml. of distilled water containing one pound of cadmium chloride hydrate. After 18 hours the solution was replaced with a fresh portion and stirring was resumed for 24 hours. Again, the solution was replaced with a fresh portion and stirring was resumed for 24 hours. The slurry was then filtered, washed free of chloride ion, and dried at 150 C. overnight. The catalyst had a uniform pore size of about 5 Angstroms, and analyzed 1.67 wt. percent sodium and 30.60 wt. percent cadmium.

The above catalyst was presulfided prior to use in the selective hydrocracking of the C to C naphtha feed. Specifically, the catalyst was charged to a testing unit and sulfided with a mixture of'10% hydrogen sulfide in hydrogen at the rate of 1.5 c.f./hr. for each cc. of catalyst. The temperature was maintained at 200 F. for two hours, then raised at a rate of F./ hr. to 600 P. where it was held for one hour. The procedure is known to incorporate between 2.5 and 4.5 wt. percent sulfur into the catalyst.

The presulfided catalyst was then used to selectively hydrocrack a C to C naphtha feed having the following analysis at 850 F., 500 p.s.i.g., 0.5 v./v./hr. and 2000 s.c.f. H /B. The feed contained 0.25 wt. percent added CS to ensure retention of the cadmium metal by the catalyst. The results of this run are summarized below:

The necessity of sulfiding the cadmium zeolite was demonstrated in an experiment in which a 100 cc. portion of the fresh unsulfided catalyst of Example 1 was used under the conditions of Example 1 but with no added sulfur in the feed. Results obtained at 850 F., 500 p.s.i.g., 0.6 v./v./hr., 1500 c.f./B exit hydrogen rate are compared with results of Example 1 in the following tabulation:

TABLE II Product Feed None Sulfided Catalyst Preconditioning Product Distribution, wt. Percent The two-fold increase (94.1 vs. 45) in conversion demonstrates quite dramatically the effect of presulfiding the catalyst. Furthermore, it can be assumed that the effect of sulfur is more pronounced than demonstrated because the feed contained 83 ppm. sulfur which undoubtedly promoted the reaction and activated the catalyst as the run progressed.

EXAMPLE 3 The effect of sulfur activation of cadmium zeolite A Was further demonstrated. In this instance sodium zeolite A was ion exchanged at room temperature with cadmium chloride solution using concentrations disclosed in Example 1. A three-fold exchange for 21, 66 and 20 hours, respectively, was made with each exchange followed by three water washes. The product from the third wash after the third exchange was dried. A portion of the product was compacted into A -inch pellets and 170 cc. of the pellets were charged to a fixed bed testing unit. The catalyst was heated to 300 F. in a stream of nitrogen and then hydrogen at atmospheric pressure. The system was then maintained for about 64 hours at 400 F. with hydrogen flow at atmospheric pressure. T hereupon, the system was pressurized with hydrogen at 500 p.s.i.g. and upon increasing the temperature to 500 F. the C to C feed of Example 1, containing 1% carbon disulfide, was introduced. Conversion was conducted at 500 p.s.i.g., 0.5 v./v./hr., and an exit hydrogen rate of 1895 c.f./B. The temperature was varied over different time periods, as follows:

Period Run, hours Temperature, F.

A (P0. 5 500-550 B 0. 5'2. 5 550-725 2. 531. 5 725*850 3. 5-5. 5 850 C c- 5. 56. 5 850 Products from Periods B and C were segregated for analyses and a subsequent Period D was made under the same conditions as Period C, except that the feed contained 0.25 wt. percent added carbon disulfide. A decided improvement in removal of normal parafiins with continued exposure to the sulfur-containing feed was observed and clearly demonstrates increasing activation of the catalyst, as indicated below:

As demonstrated in Example 2, presulfiding of the cadmium-containing S-Angstrom zeolite catalysts is necessary and critical to their successful use. When presulfided in accordance with the invention, markedly superior cata lysts are formed, which are substantially more selective and active than another recently discovered similar selective and active than another recently discovered similar selective hydro-conversion catalyst. In copending applications Ser. Nos. 444,812 and 444,796 both filed April 1, 1965, the surprising and unexpected superiority of zinccontaining S-Angstrom crystalline zeolites is disclosed. In these applications comparison of the zinc form to such other forms as calcium, magnesium, nickel, etc., is made with the clear conclusion that Zinc is the preferred zeolite form. It is further shown therein that when the zeolite is further combined with a hydrogenation metal, such as palladium, the activity and selectivity of the catalyst increase further.

In order to compare the relative selective catalytic abilities of the recently discovered superior palladiumzinc S-Angstrom zeolite of the aforementioned application Ser. No. 444,796 with the cadmium S-Angstrom zeolite of the present invention, a palladium-zinc S-Angstrom zeolite prepared in substantial accordance with the procedure described on pages 13 and 14 of copending application Ser. No. 444,796 was utilized, after presulfiding in hydrocracking operation with a light naphtha feed containing 0.25 wt. percent carbon disulfide, at 700 to 850 F., and 500 to 1000 p.s.i.g., to selectively hydrocrack the C to C naphtha feed of Example 1. Under comparable conditions of temperature, pressure, feed rate and hydrogen rate, the following comparison with the results of Example 1 was obtained.

TABLE IV Product Feed Cadmium Palladium-omZinc 5-Angstrom Zeolite 5-Angstrom Zeolite Conversion of 1105 and 1100 As indicated, the presulfided cadmium-containing 5- Angstrom sieve showed greater selectivity at approximately the same conversion level, as particularly indicated by the higher n-pentane conversion. It is further noteworthy that the cadmium S-Angrstom zeolite exhibited this superiority even in the absence of the palladium hydrogenation component, which would ordinarily be expected to be necessary in hydrocracking reactions.

It will be understood that the above description is to be considered illustrative and that variations can be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A process for reducing the straight-chain hydrocarbon content of a hydrocarbon feedstock by selectively hydrocracking same which comprises contacting said feedstock at elevated temperature and pressure in the presence of hydrogen with a catalyst comprising a crystalline alumino-silicate zeolite containing cadmium in an amount corresponding to at least 25% of its cationic content and having uniform pore openings of about 5 Angstrom units, wherein said catalyst contains 0.5 to 15 wt. percent sulfur, and recovering a hydrocarbon product having a substantially reduced straight-chain hydrocarbon content.

2. The process of claim 1 wherein said feedstock is a naphtha fraction.

3. The process of claim 1 wherein the sodium content of said zeolite is less than about 10 wt. percent.

4. The process of claim 1 wherein a major proportion of the cation content of said zeolite is supplied by cadmium cation.

5. The process of claim 1 wherein said catalyst has been sulfactivated by treatment with a sulfur compound.

6. The process of claim 1 wherein said catalyst additionally comprises a hydrogenation component.

7. The process of claim 6 wherein said hydrogenation component is a platinum group metal.

8. The process of claim 7 wherein said platinum group metal is palladium.

9. The process of claim 6 wherein said catalyst is sulfactivated by contact with a sulfur-containing feedstock.

10. A catalyst composition comprising a metallic hydrogenation component combined with a crystalline alumino-silicate zeolite containing cadmium in an amount corresponding to at least 25% of its cationic content and having uniform pore openings of about Angstrom units, said catalyst composition additionally comprising 0.5 to 15 wt. percent sulfur.

11. The composition of claim 10 wherein said hydrogenation component comprises a platinum group metal.

12. The composition of claim 11 wherein said platinum group metal is palladium.

13. A process for improving the octane rating of naphtha fractions by selective hydrocracking of straightchain hydrocarbons contained therein which comprises contacting said naphtha fractions at elevated temperature and pressure in the presence of hydrogen with a catalyst comprising a crystalline alumino-silicate zeolite having uniform pore openings of about 5 Angrstoms, said zeolite having at least 25% of its cation content supplied by cadmium cation, said catalyst containing 0.5 to 15 wt. percent sulfur, and recovering a naphtha product having substantially reduced straight-chain hydrocarbon content and an improved octane rating.

14. The process of claim 13, wherein said zeolite has a major proportion of its cation content supplied by cadmium cation.

15. The process of claim .13, wherein said catalyst additionally comprises a hydrogenation component.

16. The process of claim 15, wherein said hydrogenation component is a platinum group metal.

17. The process of claim 13, wherein said catalyst has been sulfactivated by contact with a sulfur-containing feedstock.

18. The process of claim 13, wherein said temperature is within the range of 400 to 950 F., said pressure is within the range of 200 to 4000 p.s.i.g., and wherein the hydrogen feed rate is 1000 to 10,000 s.c.f./B. of naphtha feed.

19. The process of claim 13, wherein said temperature is within the range of 650 to 850 F., said pressure is within the range of 500 to 2500 p.s.i.g., and wherein the hydrogen feed rate is 1500 to 5000 s.c.f./B. of feed.

20. A process for selectively hydrocracking naphtha fractions containing straight-chain hydrocarbons and nonstraight-chain hydrocarbons, which comprises contacting said fractions in a catalyst zone maintained at elevated temperature and pressure, flowing a substantial amount of hydrogen gas into said pressurized catalyst zone, and recovering naphtha product having a substantially reduced straight-chain hydrocarbon content and a substantially improved motor octane rating, wherein. the catalyst in said zone comprises a sulfactivated crystalline alumino-silicate zeolite having uniform pore openings of about 5 Angstrom units and containing cadmium in an amount corresponding to at least 25% of its cationic content and further containing 0.5 to 15 wt. percent sulfur.

21. The process of claim 20, wherein said catalyst additionally comprises a metallic hydrogenation component.

22. The process of claim 20, wherein said temperature is within the range of 650 to 850 F., and said pressure is Within the range of 500 to 2500 p.s.i.g.

References Cited UNITED STATES PATENTS 2,971,904 2/1961 Gladrow et al. 208-135 3,013,983 12/1961 Breck et al. 252455 3,039,953 6/1962 Eng 20826 3,175,967 3/1965 Miale et al. 208 3,243,366 3/1966 Kimberlin et al. 20828 DELBERT E. GANTZ, Primary Examiner. HERBERT LEVIN, Examiner.

Claims (1)

1. A PROCESS FOR REDUCING THE STRAIGHT-CHAIN HYDROCARBON CONTENT OF A HYDROCARBON FEEDSTOCK BY SELECTIVELY HYDROCRACKING SAME WHICH COMPRISES CONTACTING SAID FEEDSTOCK AT ELEVATED TEMPERATURE AND PRESSURE IN THE PRESENCE OF HYDROGEN WITH A CATALYST COMPRISING A CRYSTALLINE ALUMINO-SILICATE ZEOLITE CONTAINING CADMIUM IN AN AMOUNT CORRESPONDING TO AT LEAST 25% OF ITS CATIONIC CONTENT AND HAVING UNIFORM PORE OPENINGS OF ABOUT 5 ANGSTROM UNITS, WHEREIN SAID CATALYST CONTAINS 0.5 TO 15 WT. PERCENT SUFLUR, AND RECOVERING A HYDROCARBON PRODUCT HAVING A SUBSTANTIALLY REDUCED STRAIGHT-CHAIN HYDROCARBON CONTENT.

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