WO1997013826A1

WO1997013826A1 - Hydrocracking over a mordenite zeolite catalyst

Info

Publication number: WO1997013826A1
Application number: PCT/US1996/014612
Authority: WO
Inventors: Michael M. Olken; Juan M. Garces; Guo-Shuh John Lee
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1995-10-12
Filing date: 1996-09-13
Publication date: 1997-04-17
Anticipated expiration: 1998-04-12
Also published as: AU6974596A

Abstract

A hydrocracking process for the conversion of high boiling hydrocarbon feedstocks, particularly paraffin-base petroleums, into lower boiling hydrocarbon mixtures enriched in C5, C6 and C7 high octane isoalkanes. The process involves contacting a high boiling hydrocarbon feedstock with hydrogen under reaction conditions in the presence of a hydrocracking catalyst containing a hydrogenation metal and an acidic mordenite zeolite. The high octane hydrocarbon products are useful in transportation fuels.

Description

HYDROCRACKING OVER A MORDENITE ZEOLITE CATALYST

This invention pertains to a process of hydrocracking hydrocarbons, particularly high boiling petroleum feedstocks, over a zeolite catalyst. Modern hydrocracking is a flexible process for converting low value, high boiling petroleum feedstocks into high value transportation products and petrochemical feedstocks. Hydrocracking is generally accomplished by contacting in an appropriate reactor, a vacuum gas oil (VGO) or other high boiling hydrocarbon feedstock with a hydrocracking catalyst under reactive conditions, including elevated temperature and pressure and in the presence of o hydrogen, sufficient to produce a hydrocarbon produα, a substantial portion of which has a lower average molecular weight and a lower boiling range than the feedstock. Hydrocracking technology has developed for over twenty years driven by an increasing demand for transportation fuels, including gasoline, turbine and diesel fuels, and driven by demands for higher quality petrochemical feedstocks. In addition, environmental considerations have 5 motivated changes in hydrocracking processes. For a discussion of the subjeα see

"Hydrocracking Processes and Catalysts," by John W. Ward in Fuel Processing Technology, 35 (1993), pp.55-85.

Hydrocracking catalysts contain two components, a metallic component for hydrogenation and an acid component for cracking. Traditionally, the hydrogenation 0 component is seleαed from Group 8 and Group 6 metals, particularly the Group 8 noble metals, such as platinum and palladium. The cracking component can be seieαed from amorphous oxides, such as amorphous silica-aluminas, or from crystalline porous aluminosilicates, such as large pore zeolites, or from mixtures of amorphous oxides and zeolites. According to J. Ward {op. cit, p. 71) ultrastable zeolite Y dominates the market for broad range hydrocracking. 5 Mordenite zeolite has also been disclosed as a cracking component in hydrocracking catalysts, as found in U.S. patent 4,430,200; U.S. patent 3,953,320; U.S. patent 3,847,792; and U.S. patent 3,668, 13. The silica/alumina molar ratio of the mordenite zeolite is taught to range from as low as 12 to as high as 100. Feedstocks for these mordenite catalyzed processes are taught to range from naphthas through heavy gas oils, or alternatively, to 0 contain liquid hydrocarbon fraαions boiling from as low as 30°C (86°F ) to as high as 650°C (1202°F). The patents largely teach the formation of C3.5 hydrocarbon fraαions with lesser amounts of higher boiling fraαions. Typically, the references are silent with respeα to the isomeric distribution of any C₅ and higher boiling fraαions.

In view of the above, hydrocracking catalysts containing mordenite zeolite as the 5 cracking component are not competitive when the objeαive is to produce environmentally acceptable, high oαane transportation fuels. Disadvantageously, mordenite appears to produce too many C3-C4 hydrocarbons. C3 hydrocarbons are too volatile for use in transportation fuels. Of the C₄ hydrocarbons, only isobutane has a high oαane number, but it is also too volatile. None of the aforementioned processes appear to produce large quantities of environmentally acceptable, high oαane C₅, C₆ and C₇ isoalkanes, such as, 2-methyibutane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2,2-dimethylpentane, and 2,3-dimethylpentane. Accordingly, hydrocracking produα mixtures from the aforementioned prior art processes must be further subjeαed to costly isomerization or reforming treatments, if high oαane fuels are the desired end-produα.

It would be advantageous to discover a simple hydrocracking process which employs a catalyst comprising a hydrogenation component and, as a cracking component, an acid mordenite zeolite, and which catalyst also exhibits high seleαivity for high oαane C₅, Cξ o and C₇ isoalkanes. Mixtures containing these high oαane components could be advantageously added to transportation fuels to improve their efficiency, while maintaining acceptable environmental standards. Summary of the Invention

This invention is a process of hydrocracking a hydrocarbon feedstock. The process 5 comprises contaαing a hydrocarbon feedstock having an initial boiling point in the range from 250°F (121°C) to 950°F (510°C) with hydrogen in the presence of a catalytic amount of a hydro¬ cracking catalyst, described hereinafter, under reaαive process conditions. The produα of the hydrocracking process of this invention comprises a mixture of hydrocarbons having an initial boiling point which is lower than that of the feedstock, in addition, the produα mixture is 0 enriched in C₅, Cβ and C₇ isoalkanes having oαane numbers greater than 80.

The hydrocracking catalyst which is employed in the process of this invention contains a hydrogenation component and a cracking component, the latter comprising an acidic mordenite zeolite having a silica/alumina molar ratio of greater than 30: 1 and a Symmetry Index, as determined by X-ray diffraαion, of at least 1.0. In a preferred embodiment 5 the acid mordenite component is prepared by a method comprising: (A) heating an acidic mordenite having a silica/alumina molar ratio of less than 30: 1 and a Symmetry Index of between 0.5 and 1.3, and thereafter (B) contaαing the heated acidic mordenite with a strong acid to remove an amount of alumina sufficient to provide a silica/alumina molar ratio of at least 30: 1 , and optionally (C) repeating at least once the steps of (A) heating and (B) contaαing 0 with strong acid to remove additional alumina.

Experimental tests demonstrate that the above-identified catalyst exhibits good aαivityfor hydrocracking high boiling hydrocarbon feedstocks when compared with a commercial catalyst based on zeolite Y. More significantly, the hydrocracking catalyst of this invention exhibits a surprising seleαivity to some of the highest oαane hydrocarbons, 5 including 2,2-dimethylbutane and 2,3-dimethylbutane. Accordingly, the hydrocracking process of this invention is useful for producing high octane fuels and fuel additives direαly from petroleum feedstocks. Detailed Description of the Invention

The present invention is direαed to a hydrocracking process which is conduαed in the presence of a heterogeneous catalyst comprising a cracking component and a hydrogenation component. The process comprises contaαing under reaαion conditions a hydrocarbon feedstock having an initial boiling point within the range from 250°F (121°C) to 950°F (510°C) with hydrogen in the presence of a catalytic amount of the catalyst. The hydrogenation component of the catalyst comprises a metal seleαed from Group 6 or Group 8, preferably Group 8, of the Periodic Table. The cracking component comprises an acid mordenite zeolite, preferably prepared by the method described in detail hereinafter. The hydrocarbon feedstock which can be subjeαed to the hydrocracking method of this invention comprises mixtures of hydrocarbons, specifically paraffins, aromatic ring compounds, and/or naphthenes (saturated rings with five of six carbon atoms in the ring). Examples of such mixtures include petroleum mineral oils and refinery oils and fraαions thereof. Suitable petroleum feedstocks include heavy naphthas, atmospheric gas oils, light gas oils, heavy gas oils, heavy distillates, atmospheric residuals, and vacuum residuals, as well as oils derived from light tar sands, shale and coal. Suitable refinery feedstocks include coker gas oils, such as kerosene and jet fuel stocks, as well as catcracker distillates. The typical hydrocarbon feedstock possesses an initial boiling point in the range from 250°F (121°C) to 950°F (510°C). The "initial boiling point", defined by James G. Speight in The Chemistry and Technology of Petroleum, 2^nd edition, Marcel-Dekker, 1991, is the temperature at which a first drop of distillate leaves the tip of a condenser at atmospheric pressure, or at a specified lower pressure for feedstocks at the high boiling end of the range.

Preferably, the hydrocarbon feedstock is a paraffin-base petroleum feedstock, meaning that it contains a significant concentration of paraffins, which may be linear or branched. More preferably, the feedstock is enriched in linear or branched paraffins having greater than 12 carbon atoms, and more preferably, having from 15 to 25 carbon atoms. The term "enriched" means that the aforementioned paraffins comprise greater than 15 weight percent of the feedstock, preferably, greater than 20 weight percent of the feedstock, and more preferably, greater than 30 weight percent of the feedstock. Normally the feedstock will be substantially free of saturated, straight and branched chain hydrocarbons containing between 1 and 10 carbon atoms. The single ring compounds (both aromatic and naphthenic) may be alkylated and usually are so in the lighter-boiling fraαions.

Hydrogen is required for the process of this invention. Any source of hydrogen is suitable, including hydrogen obtained from natural gas or petroleum refinery processes, or from the gasification of coal and coke, or from eleαrolytic processes. Mixtures of hydrogen with an inert gas, that is, a gas which is unreaαive under the process conditions, may be used. Suitable inert gases include nitrogen and helium. Preferably, hydrogen is employed without an inert gas. The quantity of hydrogen used can vary depending upon the specific process conditions and feedstock, but generally ranges rom 3 moles to 10 moles of hydrogen per mole of hydrocarbon feedstock, based on the average molecular weight of the feedstock.

As noted hereinbefore, the hydrocracking catalyst comprises a mordenite zeolite cracking component and a hydrogenation component. The mordenite zeolite and its preferred preparation have been described elsewhere, specifically in U.S. patent 4,891 ,448; U.S. patent 5,198,595; and U.S. patent 5,243,116. The mordenite is charaαerized as having a silica/alumina molar ratio of at least 30: 1 , a Symmetry Index defined hereinafter of at least 1.0, and preferably, a porosity such that the total pore volume is in the range from 0.18 cc/g to 0.45 cc/g, and the ratio of the combined mesopore and macropore volumes to the total pore volume is in the range from 0.25 to 0.75. For the purposes of this invention, a micropore has a radius in the range of 3 Angstrom (A) units to 10 A; a mesopore has a radius in the range of from 10 A to 100 A; and a macropore has a radius in the range of from 100 A to 1000 A.

The preparation of the preferred acid mordenite zeolite, as described in the above-cited U.S. patents, involves first selecting a starting acid mordenite having a silica/alumina molar ratio of less than 30: 1 and a Symmetry Index, as determined by X-ray diff raαion, of between 0.5 and 1.3, preferably between 0.7 and 1.3. The Symmetry Index is a dimensionless number obtained from the X-ray diff raαion pattern of sodium or acid mordenite, as measured in the hydrated form. The Symmetry Index is defined as the sum of the peak heights of the [111] (13.45, 20) and [241] (23.17 2Θ) refleαions divided by the peak height of the [3501 (26.25 2Θ) ref leαion.

The starting acid mordenite may be obtained commercially, or alternatively, it can be prepared by slurrying a sodium mordenite having the required initial silica/alumina molar ratio and Symmetry Index with an inorganic or organic acid under conditions such that the sodium ions are exchanged for hydrogen ions. Preferred acids for this exchange include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, and oxalic acid, with the inorganic acids being more preferred. Typically, the acid concentration ranges from 0.01 N to 6.0N, preferably from 0.5N to 3. ON. Preferably, the ratio of acid to mordenite ranges from 5 cc to 10 cc acid solution per gram mordenite. The slurrying treatment is conduαed at a temperature between 10"C and 100°C for 5 to 60 minutes. After the initial acid treatment, the resulting acid mordenite is washed with water and dried at a temperature between 20°C and 150°C.

Following the exchange with acid and drying in air, the acidic mordenite zeolite is heated, preferably by calcining in air or heating in an inert atmosphere, such as nitrogen. Preferably, the temperature ofthe heating is in the range from 300°C to 800°C, more preferably, from 400°C to 750°C, most preferably, from 500°C to 700^CC.

After heating, the mordenite is preferably subjeαed to an additional acid treatment for the purpose of dealumination. The second acid treatment comprises contaαing the heated mordenite with a strong acid under conditions sufficient to produce the preferred acidic mordenite zeolite used in this invention. The strong acid is typically an inorganic acid, such as nitric acid, hydrochloric acid, or sulfuric acid. The concentration of the aqueous acid solution preferably ranges from 2N to 15N, more preferably, from 4N to 12N, and most preferably from 6N to 8N. The ratio of aqueous acid solution to mordenite is in the range from

5 3 cc to 10 cc, preferably 5 cc, acid solution per gram mordenite. The mordenite is contaαed with the strong acid at a temperature between 22°C and 220°C for 1 to 6 hours. The heating and strong acid treatment can be repeated more than once, if desired, to remove additional alumina. The acid-treated mordenite is thereafter washed with water, dried for several hours at 100°C to 150°C, and may be calcined or heated one last time at a temperature from 300°C to

10 700°C.

After the initial acid mordenite is heated and then treated with strong acid according to the aforementioned preparation, a preferred acid mordenite zeolite is obtained which is beneficially employed in the hydrocracking process of this invention. The mordenite exhibits certain chararteristics by which it can be identified, specifically, its silica/alumina molar

15 ratio, Symmetry Index, and porosity.

As a result of the acid extrartions, the silica/alumina molar ratio of the mordenite is increased to a value of at least 30: 1. Preferably, the silica/-alumina molar ratio is at least 50: 1 , more preferably, at least 150: 1. Generally, the silica/alumina molar ratio is not higher than 800: 1, more preferably, not higher than 400:1.

20 As a further result of the calcination and acid extrartions, the Symmetry Index of the mordenite catalyst is often increased over that of the original mordenite. A Symmetry Index of at least 1.0 results in catalysts showing minimal deartivation. Preferably, the Symmetry Index ranges from 1.0 to 2.0. In addition, the total pore volume preferably lies in the range from 0.18 cc/g to 0.45 cc/g, and the ratio of the combined mesopore and macropore

25 volumes to total pore volume lies in the range from 0.25 to 0.75. The measurement of porosity is described in detail in U.S. patent 4,891 ,448, cited hereinabove.

In an alternative embodiment of the invention, the zeolite mordenite may be composited with an inorganic refractory oxide which serves as a binder or support. Suitable binders or supports include silicas, aluminas, silica-aluminas, clays, and mixtures thereof. In

30 addition, the zeolite can be extruded with or without binders by methods known in the art. if a binder or support is employed, it comprises from 5 to 75 weight percent of the catalyst composition, preferably, from 10 to 50 weight percent of the catalyst composition.

In addition to the above-described mordenite zeolite and optional binder or support, the hydrocracking catalyst should also contain at least one hydrogenation

35 component. Any hydrogenation component can be employed provided that it is capable of catalyzing the hydrogenation of aromatic and unsaturated aliphatic hydrocarbons with hydrogen. Typically, the hydrogenation component comprises a Group 6 or Group 8 metal of the Periodic Table, or mixtures thereof, preferably, a Group 8 noble metal. Such components are typically in the form of the free metals or their respertive oxides. The Group 8 noble metals which are preferably used include ruthenium, rhodium, palladium, osmium, iridium, and platinum. The Group 6 metals include chromium, molybdenum, and tungsten. More preferably, the hydrogenation component is platinum or palladium, with platinum in the form of the free metal being most preferred.

The hydrogenation component can be incorporated into the zeolite in any manner known in the art for combining metallic compounds with zeolites. One suitable method is to ion-exchange the metal component direαly into the mordenite zeolite either prior to or after combining the zeolite with any optional binder or support. The ion-exchange is typically accomplished by stirring the mordenite zeolite with an aqueous solution of a soluble salt, coordination compound, or organometallic complex of the desired metal. Suitable salts include soluble metal nitrates, sulfates, acetates, and chlorides. Suitable coordination compounds include soluble inorganic amino and halo compounds, such as dichlorotetra- aminoplatinum (II) and dichlorotetraaminopalladium (II). Another suitable method of incorporating the hydrogenation component into the mordenite zeolite is to impregnate the zeolite with a solution containing the desired metal or metals in dissolved form. The impregnation technique is described by Charles N. Satterf ield in Heterogeneous Catalysis in Practice, McGraw-Hill, 1980, pp. 82-84.

The ion-exchange or impregnation procedure is normally conduαed such that at least 0.1 weight percent and up to 5.0 weight percent metal, calculated as the elemental metal, is loaded onto the zeolite. Preferably, from 0.2 to 1.0 weight percent metal is incorporated onto the zeolite. The ion-exchanged or impregnated zeolite is thereafter calcined in air at a temperature between 250°C and 600°C to remove any ligands or counter ions and to produce, at least in part, the corresponding metal oxide. Prior to use, the metal-mordenite composite is treated to reduce the metallic component(s) to their artive elemental form. This redurtion comprises contaαing the metal-mordenite composite with hydrogen at a temperature ranging from 150°C to 400°C for a time sufficient to reduce the metal substantially to its elemental form.

The hydrocracking process of this invention can be conduαed in any reaαor designed for such a purpose, including preferably fixed-bed reartors. Those skilled in the art will recognize that hydrocracking processes can be conduαed according to any of four basic schemes: (1) single stage hydrocracking, (2) two stage hydrocracking, (3) once through hydrocracking, and (4) separate hydrotreating hydrocracking. Any of these schemes is suitable for the process of this invention. Ward et al., op. cit, p. 57-65, describe the four schemes in detail. Typically, in single stage hydrocracking the feedstock is pretreated with a hydrotreating catalyst to remove organic nitrogen and sulfur-containing compounds, and thereafter, the pre¬ treated feedstock and any unconverted recycle oil are passed downward through a bed of the hydrocracking catalyst. Difficult to process feedstocks, e.g., those containing high nitrogen content, are processed more efficiently in two stages wherein the unconverted oil from the first stage is f raαionated and passed to a second stage hydrocracking reartor. The process conditions of the first and second stage reartors may or may not be similar. In once through hydrocracking a single stage reaαor is employed, but with no recycle. Accordingly, only partial

5 conversion of the feedstock is obtained, but it is upgraded in value nevertheless. Finally, in the separate hydrotreating hydrocracking operation, a hydrotreated produα is fraαionated into produαs and unconverted oil. The latter is passed to a hydrocracking reaαor and converted under recycle conditions.

Any operable process conditions of temperature, pressure, and weight hourly

1 o space velocity can be employed in the process of this invention provided that a hydrocarbon mixture enriched in Cs- high oαane isoalkanes is produced. The exaα process conditions required in any given situation will depend upon the nature of the feedstock, the specific form of the catalyst, and the desired degree of conversion. Typically, the temperature ranges from 100°C (212°F) to 454°C (850°F). Typically, the total pressure ranges from 0.51 MPa (5 atm) to

15 20.3 MPa (200 atm). The total pressure is substantially comprised of the hydrogen partial pressure, since the vapor pressure of the hydrocarbon feedstock usually does not exceed more than a few atmospheres. The weight hourly space velocity (WHSV) of the hydrocarbon feedstock normally ranges from 0.1 gram feedstock per gram catalyst per hour, or simply hr¹, to 100 hr-¹, and preferably, ranges from 0.5 hr¹ to 5.0 hr¹. 0 When the hydrocarbon feedstock is contaαed with hydrogen under reaαion conditions and in the presence of the hydrocracking catalyst described hereinabove, a hydrocarbon produα mixture is obtained which has an initial boiling point which is lower than that of the feedstock. More significantly, the produα mixture is enriched in C₅, Cg and C isoalkanes, that is, branched alkanes. Preferably, the produα mixture is enriched in C_5-7 5 isoalkanes having oαane numbers greater than 80. Preferred high oαane isoalkanes include 2- methylbutane (isopentane), 2,2-dimethylbutane, 2,3-dimethyibutane, 2,2-dimethylpentane, and 2,3-dimethylpentane.

A description of oαane numbers is given by Charles N. Satterf ield in Heterogeneous Catalysis in Practice, op. cit, p. 240. As described therein, the oαane number of 0 a fuel measures the maximum compression ratio at which a particular fuel can be used in an internal combustion engine without some of the fuel-air mixture undergoing premature self- ignition. Self-ignition causes an excessive rate of pressure increase, termed "knocking," which reduces engine power and may cause engine damage. The oαane number of a fuel is measured by comparing its knocking properties with various blends of isooαane (2,2,4- 5 trimethylpentane) and n-heptane. Isooαane is arbitrarily assigned an oαane number of 100, whereas n-heptane is assigned an oαane number of 0. For example, a fuel which matches the knocking charaαeristics of a mixture of 90 parts isooαane and 10 parts n-heptane by volume will have an oαane number of 90. Oαane numbers are measured in a standard single-cylinder variable compression ratio engine. One form of measurement under mild conditions is referred to as the research oαane number (RON). Another form of measurement under high-speed, high load conditions is referred to as the motor oαane number (MON). Oαane numbers for a variety of C4.₇ hydrocarbons are set forth in Table I. It is seen that branched alkanes (isoalkanes) have a significantly higher oαane number than linear alkanes. Also, the more branching, the higher the oαane number.

TABLE I - Octane Numbers for C₄.₇ Hydrocarbons

HYDROCARBON RON MON

Isobutane 100 99 n-Butane 94 89

Isopentane 92 90 n-Pentane 62 62

2,2-Dimethylbutane 92 93

2,3-Dimethylbutane 101 94

2-Methylpentane 73 74

3-Methylpentane 75 74 n- Hexane 25 26

2,2-Dimethylpentane 93 93

2,3-Dimethylpentane 83 82

2-Methylhexane 42 45

3-Methylhexane 52 56 n-Heptane 0 0

RON = research octane number; MON = motor octane number.

The process of this invention produces hydrocarbon mixtures enriched in C5, Cβ and C isoalkanes, preferably, having oαane numbers greater than 80, as measured by either the RON or MON methods. More preferably, the process of this invention produces hydrocarbon mixtures enriched in C5, Cβ and C₇ isoalkanes having oαane numbers greater than 90. The term "enriched" is illustrated in the yields cited hereinbelow. Generally, in the process of this invention the conversion of a specific hydrocarbon component or f raαion of the feedstock is greater than 70 weight percent, and preferably, is greater than 75 weight percent. "Conversion" is defined as the weight percentage of a specified hydrocarbon component of the feedstock which reaαs to form produ s. For example, a "70 percent conversion of the ₇ component of the feedstock" means that 70 weight percent of the Cι₇ component of the feedstock reaαs to form produαs. Conversion can be varied depending upon the specific feedstock employed, the specific form of the catalyst, and the specific process conditions. At constant pressure and space velocities, conversion typically increases with increasing temperature. At constant temperature and pressure, conversion typically decreases with increasing space velocity.

As a particular advantage, in the process of this invention the combined yield of C₅, Cβ and C isoalkanes is generally greater than 0.9 weight percent, preferably greater than

10 10 weight percent, and more preferably, greaterthan 20 weight percent. "Yield" is defined as the weight percentage of the hydrocarbon produα stream which exists as a specific produα or produαs, such as Cs-₇ isoalkanes. Like conversion, yields vary depending upon the specific feedstock, the specific form of the catalyst, and the specific process conditions.

More advantageously, in the process of this invention the combined yield of 2,2-

15 and 2,3-dimethylbutane is generally greaterthan 0.2 weight percent, and preferably, greater than 1.0 weight percent. In the Cβ f raαion alone, the combined percentage of 2,2- and 2,3- dimethylbutanes is typically greaterthan 14 weight percent.

Likewise, in the process of this invention the yield of isoheptanes is generally greater than 0.8 weight percent, and preferably, greater than 2.5 weight percent. Isoheptanes 0 include 2,2-, 2,3-, and 2,4-dimethylpentanes, 2,2,3-trimethylbutane, 2- and 3-methylhexanes, and 3-ethy I pentane. In the C₇ fraαion alone, the combined percentage of 2,2-, 2,3-, and 2,4- dimethylpentanes and 2,2,3-trimethylbutane is typically greater than 20 weight percent. All of the aforementioned yields compare favorably with the yields obtained from a commercial hydrocracking catalyst based on zeolite Y. 5 The following examples illustrate the process of this invention in various forms, including the best embodiment of the invention currently known to the inventors. The specific embodiments set forth herein should not, however, be construed to limit the invention thereto. Unless otherwise noted, all percentages are given as weight percents. Preparation of Pt-Exchanqed Dealuminated Mordenite Catalysts 0 Catalyst A

A starting mordenite powder (500 g, Tosoh HSZ-620, sodium form) having a silica/alumina molar ratio of 14.2 and a Symmetry Index 0.97 is mixed with 6M hydrochloric acid (5 I) and stirred at room temperature for 1 hr. After settling, the solid is decanted and filtered, and then washed with 5 1 of distilled water by stirring for 1 hr at room temperature. 5 Afterwards, the zeolite is allowed to settle; the water washings are decanted; and the resulting slurry is filtered. The zeolite is washed twice more using the same procedure, but only stirred for 30 min each time. After the third wash, the wet zeolite is calcined at 700°C for 2 hr in air and cooled to room temperature. The calcined acid mordenite (350 g) is slurried with 6M nitric acid (3.5 I), refluxed for 2 hr, and then filtered. The acid-treated mordenite is washed with distilled water (3.5 I) with stirring for 30 min at room temperature. The slurry is filtered, and the wet zeolite is washed twice more using the same washing procedure. Then the wet zeolite is filtered and dried at 85^βC overnight. The dried zeolite is calcined for 2 hr at 700^CC in air to yield a dealuminated mordenite zeolite, sample "3DDM-1," having a silica/alumina molar ratio of 216 and a Symmetry Index of 1.17.

The 3DDM-1 mordenite is slurried in sufficient water to cover the sample. Then a 0.01 M aqueous solution of dichlorotetraaminoplatinum (II). Pt(NH₃)₄CI₂, is added to the slurry o in sufficient quantity to give a final loading of 0.5 percent platinum metal on the zeolite. The platinum-exchanged mordenite is then heated at 350°C for 1 hr in an oxygen/helium stream containing 10 volume percent oxygen. Thereafter, the heated Pt-mordenite composite is reduced at 300°Cfor 1 hr in a hydrogen/helium stream containing 20 volume percent hydrogen to yield Catalyst A. 5 Catalyst B

The mordenite sample designated 3DDM-1 (250 g), prepared hereinabove, is slurried with 6M nitric acid (2.5 I) and then refluxed for 2 hr. The acid-treated zeolite is filtered and then washed three times with distilled water (2.5 I each wash), stirring each time at room temperature for 30 min. The zeolite is then filtered and dried at 85°C overnight. The dried 0 zeolite is calcined at 700°C for 2 hr in air to yield a dealuminated mordenite, sample "3DDM- 2," having a silica/alumina molar ratio of 302 and a Symmetry Index of 1.60. The sample is ion- exchanged according to the procedure described hereinabove with an aqueous solution of dichlorotetraaminoplatinum (II) to a platinum loading of 0.5 percent. The platinum-loaded mordenite is heated with oxygen and reduced with hydrogen as noted hereinbefore to yield 5 Catalyst B. Catalyst C

The mordenite sample designated 3DDM-2 (150 g) is slurried with 6M nitric acid (1.5 I) and then refluxed for 2 hr. The acid-treated mordenite is filtered and washed three times with distilled water (1.5 I each wash), stirring for 30 min at room temperature each time. The 0 washed sample is then filtered and dried at 85°C ovemight. Then, the sample is calcined at 700°C for 2 hr in air to yield a dealuminated mordenite sample "3DDM-3" having a silica/- alumina molar ratio of 382 and a Symmetry Index of 1.94. The sample is ion-exchanged according to the procedure described hereinabove with an aqueous solution of dichlorotetra¬ aminoplatinum (II) to a platinum loading of 0.5 percent. The platinum-loaded mordenite is 5 heated with oxygen and reduced with hydrogen as noted hereinbefore to yield Catalyst C. Examples 1-3

Each of the catalysts (A-C) prepared hereinabove is tested in a hydrocracking process as follows: A fixed-bed stainless-steel reaαor (1 /4 inch I.D. x 13 inches length) is loaded with catalyst (5 g). A hydrocarbon feedstock comprising 10 percent n-heptadecane (C17), 30 percent n-tetradecane (C14), 30 percent n-undecane (Cl l), and 30 percent n-oαane (C8) is contaαed with the catalyst in the presence of hydrogen at a temperature of 240°C, a pressure of 1.0 MPa (10 bars), a ratio of partial pressure of hydrogen to partial pressure of feedstock of 7, and at the feedstock weight hourly space velocity shown in Table II. Results are set forth in Table II as Experiments 1, 2, and 3.

J UoJ Ul o

TABLE II-HYDROCRACKING RESULTS ©

WT % YIELDS AND YIELD RATIOS

EXPT/ SV Conv CAT FEED WH (hr-1) (wt %)

C1+C2 C3 iC4 nC4 iC4/nC4 iC5 nC5

1/A 1 9.0 80% C17 0.01 0.10 0.72 0.16 4.50 1.16 0.16

3.0 82% C14 0.02 0.33 2.75 0.55 5.00 4.28 0.52

1.0 78% Cll 0.03 0.94 8.00 1.50 5.33 11.85 1.30

2/B 1 5.0 80% C17 0.01 0.05 0.21 0.37 0.57 0.33 0.09

1.5 80% C14 0.04 0.23 1.31 1.16 1.13 2.12 0.36

NJ 0.5 78% Cll 0.07 0.72 4.93 1.16 4.25 7.57 1.04

3/C 1 3.4 80% C17 0.00 0.05 0.35 0.07 5.00 0.57 0.07

1.4 80% C14 0.01 0.19 1.44 0.30 4.80 2.24 0.28

0.4 79% Cll 0.01 0.68 5.44 1.02 5.33 8.13 0.94

CE-l/Y 1 85.0 80% C17 0.02 0.92 3.51 1.25 2.81 5.01 1.19

44.0 80% C14 0.01 1.48 5.65 1.95 2.90 7.72 1.76

21.0 80% Cll 0.01 2.36 8.74 2.89 3.02 11.02 2.33

4/A 2 5.0 82% C17 0.00 0.23 1.93 0.34 5.68 2.58 0.32

2.6 80% C14 0.00 0.31 2.79 0.52 5.37 4.21 0.46

2.3 81% Cll 0.00 0.70 5.73 1.07 5.36 8.14 0.96

CE-2/Y 2 12.0 84% C17 0.00 0.43 1.98 0.61 3.25 2.23 0.46

9.0 78% C14 0.01 0.55 2.64 0.78 3.38 3.63 0.68

6.3 81% Cll 0.01 0.90 4.36 1.29 3.38 6.03 1.23

®Feed 1 : 10% n-Cl7, 30% n-C14, 30% n-Cll, 30% n-C8; Feed 2: 8% n-C17, 23% n-C14, 23% n-Cll, 23 % n-C8 , 23% ethylbenzene; Reactor conditions: 240°C, 1.0 MPa (10 bars), p(H2) /p(Feed) =7.

l NJ NJ wπ o

TABLE II continued - HYDROCRACKING RESULTS^®

^®Feed 1: 10% n-Cl7, 30% n-C14, 30% n-Cll, 30% n-C8; Feed !: 8% n-C17, 23% n-C14 23% n-Cll, 23% n-C8, 23% ethylbenzene; Reactor conditions 240°C, 1.0 MPa (10 bars), p(H2) /p(Feed) =7, HSV as shown in first section of table.

^®DMB is the combined yield of 2 , 2-dimethylbutane and 2, 3-dimethylbutane

The results of Experiments 1-3 show that insignificant quantities of C s and C₂'s and only low levels of C3's are produced by the process of this invention. Significantly, the quantities of Cs_-7 high octane isoalkanes produced are greater than the quantities of linear alkanes produced. Accordingly, the ratios of isoalkanes to the corresponding n-alkanes are typically greaterthan 1, and frequently, as high as 6 or 7. The isomeric composition of the C₆ and C₇ fractions are set forth in Tables III and IV, respectively.

Comparative Experiment CE-1

A commercial zeolite Y (Union Carbide Y82) is ion-exchanged with an aqueous solution of dichlorotetaaminoplatinum (II), then activated under oxygen and reduced under hydrogen, as described in the preparation of Catalyst A hereinabove, to yield Comparative Catalyst Y. The platinum loading is 0.5 percent. The comparative material is evaluated as a hydrocracking catalyst in a manner identical to that of Examples 1-3 with the results set forth in

Tables ll-IV.

When the results of CE-1 are compared with Examples 1-3, it is seen that the Pt- exchanged mordenite catalyst of the invention exhibits comparable activity to the Pt- o exchanged zeolite Y catalyst which is used in commercial hydrocracking processes. Moreover, the mordenite catalyst of the invention produces significantly greater yields of high octane C_ξ- isoalkanes when compared with the commercial hydrocracking catalyst.

Example 4

Catalyst A, prepared hereinabove, is tested in the hydrocracking process, with the 5 exception that the hydrocarbon feedstock comprises 8 percent n-heptadecane, 23 percent n- tetradecane, 23 percent n-undecane, 23 percent n-octane, and 23 percent ethylbenzene.

Results are set forth in Tables ll-IV.

Comparative Experiment CE-2

A hydrocracking process is conducted in accordance with the procedure of 0 Example 4, with the exception that Comparative Catalyst Y is used in place of Catalyst A.

Results are set forth in Tables ll-IV. When Comparative Experiment CE-2 is compared with

Example 4, it is seen that the Pt-mordenite catalyst of the invention exhibits comparable hydrocracking activity to the commercial Pt-zeolite Y catalyst. Moreover, the mordenite catalyst of the invention produces significantly greater yields of high octane isoalkanes as 5 compared with the commercial hydrocracking catalyst.

5

Claims

CLAIMS:

1. A process of hydrocracking a hydrocarbon feedstock comprising contacting a hydrocarbon feedstock having an initial boiling point in the range from 250°F (121°C) to 950°F (510°C) with hydrogen in the presence of a catalytic amount of a hydrocracking catalyst under reactive process conditions sufficient to produce a product mixture of hydrocarbons having an initial boiling point which is lower than that of the feedstock and which is enriched in C₅, Cβ and C isoalkanes having octane numbers greater than 80; the hydrocracking catalyst containing a hydrogenation component and a cracking component comprising an acidic mordenite zeolite having a silica/alumina molar ratio of greater than 30: 1 and a Symmetry Index of at least 1.0, as determined by X-ray diffraction, the mordenite being prepared by a method comprising:

(A) heating a starting acid mordenite having a silica/alumina molar ratio of less than 30: 1 and a Symmetry Index of between 0.5 and 1.3, and thereafter

(B) contacting the heated acidic mordenite with a strong acid to remove an amount of alumina sufficient to provide a silica/alumina molar ratio of at least 30: 1 , and optionally

(C) repeating at least once the steps of (A) heating and (B) contacting with strong acid to remove additional alumina.

2. The process of Claim 1 wherein the hydrocarbon feedstock contains greater than 15 weight percent paraffins having greaterthan 12 carbon atoms.

3. The process of Claim 2 wherein the hydrocarbon feedstock contains greater than 20 weight percent linear and/or branched paraffins having between 15 and 25 carbon atoms.

4. The process of Claim 1 wherein from 3 moles to 10 moles of hydrogen are used per mole of hydrocarbon feedstock, based on the average molecular weight of the feedstock.

5. The process of Claim 1 wherein the mordenite cracking component has a porosity such that the total pore volume is in the range from 0.18 cc/g to 0.45 cc/g, and wherein the ratio of the combined mesopore and macropore volumes to total pore volume is in the range from 0.25 to 0.75.

6. The process of Claim 1 wherein in Step (A) of the mordenite preparation the heating is conducted at a temperature between 300°C and 800°C.

7. The process of Claim 1 wherein in Step (A) of the mordenite preparation the starting acid mordenite is obtained by treating a sodium mordenite with an acid having a concentration between 0.01N and 6.0N at a temperature between 10°C and 100^CC.

8. The process of Claim 1 wherein in Step (B) of the mordenite preparation the acid is nitric, hydrochloric, or sulfuric acid in a concentration ranging from 4N to 12N, and the contacting of mordenite with acid is conducted at a temperature between 22°C and 220°C.

9 The process of Claim 1 wherein the silica/alumina molar ratio of the acid mordenite is at least 150.1 but less than 800: 1

10. The process of Claim 1 wherein the mordenite is composited with an inorganic refractory oxide selected from silicas, aluminas, silica-aluminas, clays, and mixtures thereof

11 The process of Claim 1 wherein the hydrogenation component is a Group 6 or Group 8 metal

12. The process of CLaim 1 wherein the hydrogenation component is palladium or platinum

13. The process of Claim 1 wherein the loading of the hydrogenation component is between 0.1 and 5.0 weight percent metal.

14 The process of Claim 1 wherein the hydrocracking process is conducted at a temperature ranging from 100°C to 454°C

15 The process of Claim 1 wherein the total pressure ranges from 0 51 MPa (5 atm) to 20.3 MPa (200 atm)

16. The process of Claim 1 wherein the weight hourly space velocity of the hydrocarbon feedstock ranges from 0.1 hr¹ to 100 hM

17 The process of Claim 1 wherein the combined yield in the product stream of 2,2- and 2,3-dιmethylbutanes is greater than 0.2 weight percent, and the weight percentage of 2,2- and 2,3-dιmethylbutanes in the Cβ fraction is greaterthan 14 weight percent.

18. The process of Claim 1 wherein the combined yield of isoheptanes in the product stream is greater than 0.8 weight percent, and the weight percentage of isoheptanes in the C₇ f raction is greater than 20 weight percent. 19 The process of Claim 1 wherein the combined yield of C₅, Cβ and C isoalkanes is greater than 10 weight percent.

20 A process of hydrocracking a hydrocarbon feedstock comprising contacting a hydrocarbon feedstock having an initial boiling point in the range from 250°F (121°C) to 950^βF (510°C) with hydrogen in the presence of a catalytic amount of a hydrocracking catalyst at a temperature between 100°C (212°F) and 454°C (850°F), a total pressure between 0.51 MPA (5 atm) and 20.3 MPa (200 atm), and a feedstock weight hourly space velocity of between 0.1 hr¹ and about 100 hr¹ so as to produce a product mixture of hydrocarbons having an initial boiling point which is lower than that of the feedstock and which is enriched in C₅, Z₆ and C₇ isoalkanes having octane numbers greaterthan 80; the hydrocracking catalyst containing a hydrogenation component of platinum or palladium and a cracking component comprising an acidic mordenite zeolite having a silica/alumina molar ratio of greaterthan 50: 1 and a Symmetry Index, as determined by X-ray diffraction, of between 1.0 and 2 0, being prepared by a process comprising: (A) heating an acidic mordenite having a silica/alumina molar ratio of less than 30: 1 and a Symmetry Index of between 0.5 and 1.3, and thereafter

(B) contacting the heated acidic mordenite with a strong acid to remove an amount of alumina sufficient to provide a silica/alumina molar ratio of at least 50: 1 , and optionally