CA1146921A - Hydrocarbon conversion process - Google Patents

Abstract

Abstract:
In a process for converting a high boiling hydrocarbon charge fraction to liquid products of lower boiling range which comprises contacting said charge fraction with a crystalline zeolite characterized by a silica/alumina ratio greater than 12, a constraint index between about 1 and about 12 and an acid activity measured by the alpha scale less than 10, said contacting being conducted at 650 to 850°F., space velocity of 0.1 to 5.0 LHSV and a pressure not less than about 200 psi, the improvement which comprises utilizing, as catalyst, a zeolite of the above character that is prepared by steaming followed by base exchange to substantially eliminate its activity for cracking n-hexane.

Description

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Hydrocarbon conversion process The invention is concerned with conversion of relatively heavy hydrocarbon streams to produce lower molecular weight materials from a portion or all of the charge. In a very broad sense of the term, such processes involve a "cracking"
reaction in -the sense that hydrocarbon or substituted hydro-carbon molecules are converted to reaction produc-t of lower molecular weigh-t.
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The cracking may be of a general nature in that molecules of varied nature are converted, i.e.j branched and straight chain aliphatics, naphthenes, aromatics, e-tc. The compounds so converted may also include other atoms in the mo:Lecule:
metals, oxygen, sulfur and/or nitrogen. In par-ticular processes, the intent may be to convert a certain class of - 15 compounds in order to modify a charac-teristic of the whole.
Exemplary of the latter type of conversion is shape selective ~t conversion of straigh-t and slightly branched aliphatic --~ compounds of 12 or more carbon atoms to reduce pour point, pumpability and/or viscosity of heavy fractions which contain these waxy constituents. The long carbon chain compounds tend to crystallize on cooling of the oil to an extent such that the-oil wi~l not flow, hence may not be pumped or -transported by pipelines. The temperature at which such mix~ure will not flow is designated the "pour point", as determined by standarized test procedures.

The pour point problem can be o~ercome by techniques known in the art for removal of waxes or conversion of those compounds to other hydrocarbons which do not crystallize at ambient temperatures. An important method for so converting waxy hydrocarbons is shape selective cracking or hydrocracking utilizing principles described in US Patent 3,140,322 dated July 7, 1964. Zeolitic catalysts for selective conversions ~' ' .,' - ' ~
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~ Z ~ 2 of wax described in the literature include such species as mordenite, with or without added metal to function as a hydrogenation catalyst.

Particularly effective catalysts for catalytic dewaxing include zeolite ZSM-5 and related porous crystalline alumino~
silicates as described in U.S. Reissue Patent 28,398 (Chen et al.) dated April 22l 1975. As described in that patent, drastic reductions in pour point are achieved by catalytic lO shape selective conversion of the wax content of~heavy stocks wi-th hydrogen in the presence of a dual-functional catalyst of a metal plus the hydrogen form of ZSM-5. The conversion of waxes is by scission of carbon to carbon bonds (cracking) and production of products of lower boiling ~oint 15~than the waxes. However, only minor con~ersion occurs in dewaxing. For example, Chen et al. describe hydrodewaxing of a ull range shale oil having a pour point o~ .80F. to y.ield a pumpable product of pour point at -15F. The shift of materials from the fraction heavier than light fuel oil 20 to lighter components was in the neighborhood of 9~ conversion.
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Among the less speciali~ed techniques for producing products of lower molecular weight than the hydrocarbon charge stock are catalytic cracking and catalytic hydrocracking. Catalytic 25 cracking invoLves contacting the heavy hydrocarbon charge ~; with a porous acidic solid catalyst at elevated temperatures in the range af~850 to 1000F. to yield the desired lower boiling liquid product of greater value than the liquid charge (e.g. motor gasoline) together with normally gaseous hydrocarbons and coke as by-products. Hydrocracking employs a porous acidic catalyst similar to that used in the catalytic cracking but associated with a hydrogenation component such as metals of Groups ~I and VIII of the Periodic Table. An excess o~ hydrogen is supplied to the hydrocracking reactor under superatmospheric pressure at lower temperature than those characteristic of catalytic cracking, say about 650F.

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2~ 3 Since the introduction of zeolite catalysts as exemplified by patent 3,140,249, a large proportion of the capacity for catalytic cracking and hydrocracking has been converted to use of such highly active catalysts. The high activity zeolite catalysts are characterized by very low content of alkali metal. Sodium, for example, is present as a cation in synthetic faujasites by reason of their manufacture.
Expensive ion exchange operations are carried out in the preparation of cracking and hydrocracking catalysts from synthetic faujasite to replace the sodium or other alkali metal by protons or poly-valent metal cations.

It has been recognized that such ~eolites can function as catalysts when containing a moderate percentage of sodium~
Thus Kimberline and Gladrow ~eissue patent 26,188 exhibits data showing cracking activity of a faujasite from which only one-third of the sodium has been removed by ion exchange.
The extremely high activity o~ such catalysts as zeolite ZSM-5 bas been moderated for specialized purposes by using the zeolite in the partially sodium form. See, ~or example, patent 3,899,544.

Zeolite ZSM-5 preparation is described in patent 3,702,886 which also describes several processes in which the zeolite is an effective catalyst, including cracking and h;ydrocracking.
That zeolite is shown to be prepared from a forming solution which contains organic cations, namely alkyl substituted ammonium cations. Those large organic cations then occupy cationic sites of the 2eolite and block pores at least partially. The conventional method ~or removin~ the organic cations is to burn them out with air at elevated temperature, leaving a proton at the site previously occupied by the organic cation. Sodium, or other alkali metal, at other cationic sites may then be ion exchanged to provide protons or multivalent metals as desired to prepare catalysts for cracking, hydrocracking and other purposes.

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' ' -~ f~6~ 4 Regardless of the type of catalyst used, the principalproducts desired in cracking, hydrocracking and like processes for reducing molecular weight of hydrocarbon fxactions are relatively low-boiling liquids such as motor gasoline, diesel fuel, jet fuel, No. 2 fuel oil and the like. Gaseous products such as hydrogen, me.thane, ethane, propane, etc.
represent degradation of a portion of the charge to less valuable fuels than the desired premium products. In addition to being less valuable fuelsj these gases require high proportions of hydrogen which can only deprive premium liquid products of hydrogen needed for their constitution.

In accordance with this invention the proportion of charge converted to gaseous by-products is reduced by employing a catalyst in which the active cracking ingredients is a low acidity form o~ a zeolite having a silica/alumina ratio above 12 and preferably also having a constraint inclex between about 1 and 12, such as r~.eolite ZSM-5. In preferred embodiments, the low acidity is achieved by using the sodium form of a zeolite typified by zeolite ZSM-5.

In another particular embodiment of this invention, the active cracking ingredients is the low acidity form of a zeolite such as ZSM-5 or ZsM~lI having a silica/alumina ratio above 12 and a constraint index between about~l and . 12, and in which the low acidity is imparted by steaming, as more fully described hereinbelow, followed by base exchange with an alkali or alkaline earth metal cation under conditions to substantially eliminate hexane cracking activity. This 30 ~ embodiment i9 particularly suited to dewaxing crude oils or other waxy stocks, and the process may be conducted in the presence or absence of hydrogen.

These advantageous results are accomplished by use of conversion apparatus lllustrated diagramatically in the~annexed drawings '' '.
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~ 6~ 5 wherein Figure 1 is a typical flow diagram of the process as adapted for use in an oil field and Figure 2 represents a modification in which hydrogen is circulated through the reactor. Figure 3 illustrates the Dewaxing of Taching Crude with Methane Circulation. Figure 4 illustrates the Dewaxing of Tachiny Crude Without Gas Recycle.

As shown in the drawing, one preferred use of the invention is for conversion of waxy crude petroleum in the field to provide a product suitable for transmission by pipeline.
Crudes of high pour poin-t are not suited to pipeline trans-portation because they cannot be pumped and will not flow in pipes at temperatures below the pour point, ~hich may be 50F. or higher.

Although the concept of reducing pour point o waxy crude oil is not new, the utilization of the newly discovered characteristics of alkali metal exchanged ZSM-S in a simple on site catalytic processing unit provides advantages not previously avallable.

Waxy crude oils are ound in Utah, Indonesia, Australia, ibya and China. The production of waxy crude oil in China alone exceeds 1 million barrels a day. Transportation of waxy crude oils requires special considerations including - the use of heated tank cars and heavily insulated and heated pipelines. The present invention provides an alternate means of solvin~ the transportation problem by installing on the production site simple catalytic processing units which convert the waxy crude oil to a pipelineable oil. The system is made feasible by~the discovery of novel catalyst compositions which do not require elabora~e and expensive ; equipment to operate. It's estimated that for an average well producing 500 barrels a day, the catalytic reactor required mea~ures only 3 ft. in diameter by 15 ft. long.
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~ z ~ 6 Thus it would be economically feasible to install, fox example 2000 such units in the field to process a million barrels a day of waxy crude oil. Alternatively, larger units may be built for a cluster of wells. It is also contemplated that these crude processing units be built on a portable stand so that they could be prefabricated and moved to the produc-tion site.

Waxy crude oils are generally high in hydrogen, low in sulfur and metal contaminants. However, these desirable characteristics are at present counterbalanced by their transporta-tion problems associated with their high pour point. The invention solves the transportation problem at a reasonably low cost and therefore ~eads to wider distribut:ion of waxy crude oils around the world.
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The embodiment shown in the drawing utilizes alkali metal exchanged ZSM-5, including NaZSM-5, in a simple reactor system to be installed near the producing well to convert heavy waxy crude oil to pieplineable crude.
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The catalyst is unique in its resistance to metals, nitrogen and sulfur, and can be used in the absence of hydrogen without experiencing rapid deactivation problems. Unlike H-ZSM-5 with or without hydrogenation metal funtion, alkali metal exchanged ZSM-5's reduce pour point and viscosity of waxy crude oils without forming any appreciable C3 gaseous products, so that the liquid recovery of the crude processed is 98% or betker. In this embodiment, the process is carried 30 out preferably in the liquid phase a~ 750 psig pressure and at temperatures below about 800F.
'~: ' , ' Referring now to Figure l of the annexed~drawings, waxy petroleum from producing well passes at formation temperature 35 by line 1 to a pump 2 which discharges to the tubes of a : .

92~ 7 heat exchanger 3 to be preheated by exchange against the product of the process. The preheated waxy crude passes from heat exchanger 3 to furnace 4 where it is heated further to a temperature suitable for the desired conversion. The heated charge is introduced to reactor 5 for conversion in the presence of the low acidity zeolite catalyst under conditions presently to be described. It will be noted that the conversion in this embodiment takes place without added hydrogen, a material difficult to provide at field installations.
Products of the reaction, constituted by low pour point ; crude with a small amount of gaseous hydrocarbons, are transferred to a high pressure separator 6 from which gaseous hydrocarbons of 1-4 carbon atoms are withdrawn and supplied 15 by line 7 as fuel to the furnace 4 The low pour point liquid product of the conversion in reactor 5 is txansferred by line 8 to the shell side of heat exchanger 3 where it is cooled by ~supplying preheat to the incoming charge as above describedO The cooled product flowing by line 9 from the 20 shell side of heat exchanger 3 is a low pour point li~uid petroleum suited to transport by pipeline.
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- The flow according to the diagram of Figure 2 is very similar, but with appropriate modification for circulation of hydrogen with~the crude in reactor 5. Crude petroleum from the - producing well or wells is passed by line 1 to a field separator 10 from which dissolved gases are taken off by line 11 and supplied as fuel to furnace 4. The liquid oil phase from separator 10 is then propelled by pump 2 through heat exchanger 3 and furnace 4 to reactor 5. Hydrogen gas is added to the heated crude petroleum strelm from recycle line 12 between furnaces 4 and reactor 5~ As before, the reaction product from reactor 5 is transferred to high pressure separator 6 from which low pour point waxy crude ; 35 oil passes by line 8 through heat exchanger 3 for cooling by .~ .

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giving up sensible heat to the incoming charge. The cooled low pour point crude then passes by line 9 to a suitable pipeline. The vapor phase from high pressure separator 6 is constituted primarily by elemental hydrogen for recycle by line 12 following compression in pump 13. Make-up hydrogen as needed is supplied by line 14.

The catalyst used in -the present invention is a low acidity form of a class of zeolites which have been found to be extremely acti~e in the acid form. In that form the cationic sites are occupied by protons introduced by ion exchange with an acid or an ammonium (including substituted ammonium) cation which is then decomposed by heat to a proton. Alter-natively, at least a portion of the cationic sites may be occupied by polyvalent metals. For use in the present invention, these very high acidities inherent in zeolites such as zeolite ZSM-5 are drastically reduced. Preferably, the acidity is reduced by extensive ion exchange with sodium or otKer alkali metal. The invention may also be practiced with such zeolites of very high silica/alumina ratio or by steamin~ of the active form of the zeolite. It will be recognized by those skilled in the art of zeolite catalysis that substitution of sodium or like cation and steaming are generally reco~nized as means to ~Ipoison~ a zeolite catalyst be severely impairing its activity. These agencies are generally avoided in preparation and use of zeolite catalysts in cracking or hydrocracking ;' ' - The acid activity of zeolite catalyst is con~eniently defined by the alpha scale described in an article published in Journal of Catalysis, Vol. ~I, pp 278-287 (1966). In this test, the zeolite catalyst is contacted with hexane under conditions prescribed in the publication and the amount of hexane which is cracked is ~easured. Yrom this measurement is computed an "alpha!' value which characterizes the catalyst . .

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for its cracking activity for hexane. The entire article above referred to is incorporated herein by reference. The alpha scale so described will be used herein to define activity levels for cracking n-hexane. And, in particularr for purposes of this invent.ion, a catalyst with an alpha value of not greater than about 1.0 and preferably not greater than about 0.5 will be considered to have substantially no activity for cracking n-hexane.

In a particular embodiment of this invention, a zeolite having the above described characteristics and an alpha value greater than about 20 is convert~d to a low acid.ity catalyst by contact with steam at a temperature of about 700 to about 1200F for a pexiod of kime effeckive to reduce its alpha value to not less than about 5. In general, it is contemplated to reduce the alpha value by steam treatment by a-t least about 10 alpha units. Contacting with steam may be conducted at atmospheric pressure with saturated steam, but superheated steam, sub-atmospheric pressure, or pressure up to 500 pounds of steam per square lnch may be used. The zeolite steamed in accordance with the foregoing procedure is khen base exchanged with alkali or alkaline earth metal cations to an extent effective to reduce its alpha value to not greater than about 1. a, and preferably to not greater than about 0.5. In essence, base exchange is conducted under conditions which substantially eliminate the activity of the zeolite ~or cracking n-hexane. As will be noted in Table 2 below, a catalyst with an alpha value even below 0.1 can ha~e some residual activity for n-hexane cracking. But, this residual activity is so small compared with the more highly acidic forms of the same catalyst as to warrant the characterization-"substantially eliminated." Alkali metal cation, preferably lithium and sodium, are particularly effective for t}liS purpose. Catalysts prepared by the particular procedure just described are highly efficient for - \
~ 6~ o dewaxing, and especially for dewaxing crude oils. In such service, the ca-talyst is effective at start-of-run temperatures of about 640F or even less, and exhibit excellent aging behavior and, as a consequence, long cycle life.

In general, the catalyst used in accordance with this invention are crystalline zeolites haviny a silica/alumina ratio greater than 12. Preferably the zeolite catalyst has a Constraint Index (C.I.) between about 1 and about 12.
Zeolites characterized by such cons-traint indices induce profound transformations of aliphatic hydrocarbons to aromatic hydrocarbons in commercially desirable yields and are generally highly ef~ective in conversion reactions involving aromatic hydrocarbons. These zeolites retain a degree of crys~allinity for long periods in spite of the presence oE steam at high temperature which induces irreversible collapse of the framework or other zeolites, e.g. of the X
and A type. Furthermore, carbonacous deposits when formed, may be removed by burning at higher than usual temperatures ;~ to restore activity In many environments the zeolites of this class exhibit very low coke forming capability, conducive to very long times on stream between burning regenerations.
-An important characteristic of the crystal structure of this ;~ ; class of zeolites is that it provides constrained access to, and egress from the intracrystalline free space by virtue of having a pore ~imension greater than about 5 Angstroms and pore windows of about a size such as would be provided by 10-membered rings of exygen atoms. It is to be understood, of course, that these rings are those formed by the regular disposition of the tetrahedra making up the anionic framework of the crystalline alluminosilicate, the oxygen atoms them-selves being bonded to the silicon or aluminum atoms at the ; 35 centers of the tetrahedra. Briefly, the preferred type .
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: ' '' . ; ' ~eoli-tes useful in this in~ention possess a silica to alumina mole ratio of at least about 12 preferably in combination with a structure providing constrained access to the crystal-line free space.

The zeolite will have a silica/alumina ratio greater than 12. In one embodiment, the desired low acid activity of the ca-talyst is achieved by unusually high silica/alumina ratio, greater than 1000, prefera~ly upwards of about 1500.

The silica to alumina ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid anionic framework of the zeolite crystal and to exclude aluminum in the binder or in cationic or other form within the channels. Such zeolites, after activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that for water, i.e. they exhibit "hydrophobic" properties.
~- It is believed that this hydrophobic character is advantageous in the present invention.
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The type zeolites described freely sorb normal hexane and have a pore dimensions yreater than about 5 Angstroms. In addition, the structure will preferably provide constrained access to Iarger molecules. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formed by 8-membered rings of oxygen atoms, then access by molecules of lar~er cross-section than normal hexane is excluded and the zeolite is not of the constrained type. Windows of 10-membered rings are preferred, althou~h, in some instances, excessive puckering or pore blockage may render these zeolites ineffective. Twelve-membered rings do not generally appear to offer sufficient constraint to produce the advantageous conversions, although puckered .; , . .
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:- -~6~ 12 structures exist such as TMA offretite which is a known effective zeolite. Also, structures can be concei~ed, due to pore blockage or other cause, that may be operative.

Rather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained access, a simple determination of the "constraint index" may be made by passing continuously a mixture of an equal weight of normal hexane and 3-methylpentane over a sample of zeolite at atmospheric pressure according to the following procedure.
: A sample of the zeolite, in.the form of pellets or extrudate,is crushed to a particle size about that of coarse sand and mounted in a glass tube. Prior to testing, the zeolite is ~; treated with a stream of air at 1000F. ~or at least 15 minutes. The zeolite is then 1ushed with helium and the temperature adjusted between 550E'. and 950F. to give an overall. conversion between 10% and 60%. The mixture of hydrocarbons is passed at 1 liquid houxly space velocity (i.e., 1 volume of liquid hydrocarbon per volume of zeolite per hour).over the zeolite with a helium diluation to give a helium to total hydrocarbon mole ratio of 4:1. A.fter 20 minutes on stream a sample of the effluent is taken and ~ : analyzed, most conveniently by gas chromatography; to determine '~ the fraction remaining unchanged for each of the two hydro-~ 25 carbons.
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The "constraint index" is calcula~ed as follows:
. log10 (fraction of n-hexane remaining~
' Constraint Inde~ =
~ 30 log10 (fraction of 3-methyl pentane . remaining) The constraint index approximates the ratio of the cracking : rate constants for the two hydrocarbons. Preferred zeolites 7, for the present invention are those having a constraint ~ 35 index in the approximate range of 1 to 12. Constraint Index .. (CI) ~alues for some typical zeolites are:

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ZEOLITE C
ZSM-5 8 . 3 ZSM-ll 8 . 7 ZS~1-38 2 TMA Offretite 3 . 7 Beta 0.6 Z SM-4 0 . 5 Ff-Zeolon oO 4 Amorphous Silica-Alumina . 0.6 Erionite 38 ~-~ . It is to be realized that the above constraint index valuestypically~characterize the specified zeolites but that such :~ are the cumulative result of several variables used in ' ~ ' determination and calculation thereof. Thus, for a given ' zeolite depending on the temperatures employed within the aforenoted range of SS0F. to 950F~, with accompanying : c,onversion between 10~ and 60~-the constraint index may vary within the indicat.ed approximate range of 1 to 12. Likewise, : other variables such as the crystal size of the zeolite, the presence of possible occluded contaminants and binders ~; intimately combined with the zeo].ite may a,ffect the constraint index. I~ will accordingly be understood by those skilled ~: ' in the art that the constraint index, as utilized herein, :~ while affording a highly useful means for characterizing the ~: 25 zeolites of interest is approximate, taking into consideration the manner of its determination, with probability, in some instances, of compounding variables extremes.
, While the above experimental procedure will enable one to achieve the desired overall conversion of 10 to 60~ for most . catalyst samples and represents preferred conditions, it may~ .

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- ' - : '' 2~ 14 occasionally be necessary to use somewhat more severe conditions for samples of very low acid activity, such as those having a very high silica to alumina ratio. In those instances, a temperature o~ up to about 1000F. and a liquid hourly space velocity of less than one, such as 0.1 or less, can be employed in order to achieve a minimum total conversion of about 10%.

The preferred class of zeolites defined herein exemplified by ZSM-5, ZSM-ll, ZSM-12, ZSM-35, ZSM-38 and other similar materials. U.S. Patent, 3,702,886 describes and claims ZSM-5. ZSM-ll is more particularly described in U.S.
Patent 3,709,979, while ZSM-12 is more particularly described in U.S. Patent 3r832,449. ZSM-35 iS more particularly described in U.S. Patent No. 4,016,245 and ZSM-38 is more particularly described in U.S. Patent 4,046,859.
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In addition to those zeolites, the invention in its broader aspects o~ zeolites having a silica/alumina ratio above 12 also contemplates such zeolites as Beta, described in U.S.
reissue patent Re 28,341.

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~ 15 The specific zeolites descrihed, when prepared in the presence of organic ca-tionsl are catalytically inactive possibly because the intracrystalline free space is occupied by : organic cations from the forming solution. They may be activated by heating in an inert atmosphere at 1000F. for one hour, for example followed by base exchange with ammonium salts followed by calcination at 1000F. in air. The presence of organic cations in the forming solution may not be ab-solutely essential to the formation of this type zeolite;
however, the presence of these cations does appear to favor the formation of this special type of zeolite. More generally in most applications it is desirable to activate this type catalyst by base exchange with ammonium salts followed by calcination in air at about 1000F. for from about 15 minutes to about 24 hours.

: Natural zeolites may sometimes be converted to this type zeolite catalyst by various activation procedures and other treatments such as base ~xchanye~ alumina extraction and calcination, in combinations~ N.atural minerals which may be so treated include ferrierite, brewsterite, stilbite, dachi-. ardite, epistilbite, heulandite, and clinoptilolite. The .~ preEerred crystalline aluminosilicate are ZSM-5, ZSM-ll, ZSM-12, ZSM-35, and ZSM-38, with ZSM-5 particularly preferred.
In a preferred aspect of this invention, the zeolites hereof are selected as those having a crystal framework density, in the dry hydrogen form, of not substantially below about 1.6 : grams per cubic centimeter. It has been found that zeolites w~ich satisfy all three of these criteria are most desired.
Therefore, the preferred zeolites of this invention are those having a constraint index as defined above of about 1 to about 12, a silica to alumina ratio of at least about 12 and a dried crystal density of not less than about 1.6 grams per cubic centimeter. The dry density for known structures . ' .
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-~6~ 16 may be calculated from the number of silicon plus aluminum atoms per 1000 c~bic Angstroms, as given, e.g., on page 19 of the article on Zeolite Structure by W.M. Meier.
This paper is included in "Proceedings of the Conference on Molecular Sieves, London, April 1967", published by the Society of Chemical Industry, London, 1968. When the crystal structure is unknownt the crystal framework density may be determined by classical pykometer techniques. For example, it may be determined by immersing the dry hydrogen form of the zeolite in an organic solvent which is not sorbed by the - crystal. It is possible that the unusual sustained activity and stability of this class of zeolites is associated with its high crystal anionic framework density of not less than about 1.6 grams per cubic centimeter. This high density, of course, must be associated with a relatively small amount of free space within the crystal, which might be expected to result in ~ore stable structures. This free space, however, is important as the locus of catalytic activity.

Crystal framework densities of some typical zeolites are:

Void Framework Zeolite Volume Density ,~ .
Ferrierite 0.28 cc/cc 1.76 g/cc Mordenite .28 1.7 ZSM-5, -11 .29 1.79 Dacchiardite .32 1.72 25 L .32 1.61 Clinoptilolite .34 1.71 Laumontite .34 1.77 ZSM-4 (Omega) .38 - 1.65 Heulandite .39 1.69 :
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~ 17 P .41 1.57 Offretite .40 1.55 Levynite .40 1.54 Erionite .35 1.51 5 Gmelinite .44 1.46 Chabazite .47 1.45 A .5 1.3 Y .48 1.27 ~hen synthesized in the alkali metal form, the zeolite of low acid activity by reason of ~ery high silica/alumina ratio or steaming is conveniently converted to the hydrogen form, generally by intermediate formation of the ammonium form as a result of ammonium ion exchange and calcination of the ammonium :Eorm to yield the hydrogen form. In addition to the hydrogen form, other foxms of the zeolite wherein the ori~inal alkali metal has been reduced to less than about 1.5 percent by weiyht may be used. Thus, the original alkali metal of the zeolite may be replaced by ion exchange with other suitable ions o~ Groups IB to VIII of the Periodic Table, including, by way of example, calcium or rare earth metals.
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The zeolites used according to the invention have low alpha values, less than about 10. Preferably, -the alpha value is substantially lower than unity. As noted, the low acid activity may be achieved by using zeolites of very high silica/alumlna ratio or by severe high temperature steaming~
oE zeolites having lower silica/alumina ratio, for example zeolite ZSM-5 of ratio 40 may be treated with 100% steam at 1200F. for a period of time ~several hours) adequate to reduce the acid a¢tivity to the necessary level.
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Preferably, the low acidity if achieved by extensive ion e~change of the zeolite with sodium or other alkali metal ~ ' :

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~6~ 18 cation. Silica/alumina ratios in the range of 12 to aluminum free wlll generally characterize the zeolites preferred in this form of the invention. Particularly preferrecl zeolites may be in the range of 20-2000. It is found that the sodium forms of the zeolites usually are less efficient for dewaxing than are the acid forms but give better overall results measured as conversion, parti.cularly s:ince the conversion products are low in gaseous hydrocarbons. In the embodiment o this invention wherein steaming is combined with base exchange t i.e. by steaming to reduce the alpha value by at least 10 units but not below an alpha value of 5 followed by base exchange with an alkali metal under conditions effective to substantially eliminate hexane cracking activity, the zeolite catalyst has high activity for dewa~ing as measured : 15 by its effectiveness at temperatures in the range of about 650 to about 800F.

Sodium content of the zeolit.es will vary inversely with the .~ silica/alumina ratio since it is the aluminum atoms which provide cationic sites suitable for acceptance of the alkali metal ion. Depending on that ratio, sodium content may very between 0.4 and 5.2 weight percent of the metal, with preferred sodium contents ranging between 0.75 and 3.4 weight % sodium as metal. Content of the o~her alkali metals will vary from those numbers on a weight basis in proportion to atomic weights~ The alkali metal content generally can be expressed as 0.17 to 2.26, preferably 0.33 to 1.50 milliequivalents per gram. .Sodium content in excess of satisfying cationic sites is considered desirable. The reason is not clearly understood. For example, ZSM-5 containing about 40 ppm of Al and 1~ Na is a very good catalyst. These remarks apply in the absence of steam treatment. In the embodiment in which steaming is followed by base exchange, the lattice alumina content will to some extent have been modified and :~
the final sodium content may be somewhat reduced.
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In preferred forms of the inven-tion, the zeolike contains no hydrogenation metal component, although hydrogen is preferably mixed with the charye when the mixed phase trickle mode of con-tact is employed. However, the invention contemplates catalyst blends in which the zeolite serves as a matrix for finely divided hydrotreating catalyst o~ conventional nature.
Such hyclrotreating catalyst are hydrogenation metal catalyst such as cobalt-molybdenum or n.ickel-tungsten on a porous alumina support~ These composites are prepared by thorough .mixing of a major proportion of sodium zeolite and a minor proportion of hydrotreating catalyst followed by pelleting of the blend.

The low acidity alkali metal zeolites are prepared by .ion e~change of the ~eolite with an aqueous so.lution of an alkali metal salt or hydroxide at high pEI values. In the following example, care was taken to assure complete ion exchange. r~hus the observed ac-tivity appears truly re-presenta-tive of a non-acidic zeolite.
~ Example 1 - Sodium ZSM-5 was prepared by the addition of 3.0 gms of 14-~ 30 mesh NH4ZSM-5 at room temperature to 150 ml of 0.2N NaCl ~ solution having a pH of 10.0 (pH adjusted with 0.lN NaOH~.
The mixture was maintained at room temperature for 48 hours with occasional agitation by swirling to avoid particle . breakage. The pH of the solution was monitored frequently and adjusted to 10.0 with 0.lN NaOH as required. Before overnight con-tact, the pH was adjusted to 11Ø After 48 hours~ the liquid was decanted and replaced with 150 ml of

3~ fresh NaCl/NaOH solution. The exchange was completed by 53 hours as judged by the constancy of the pH. The catalyst was washed with 150 ml of dilute NaOH (pH=10) solution and dried at 130C.

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Example 2A further batch of NaZSM-5 was prepared in the same manner as in Example l, except that 30 gms of powdered sample of a large crystal ZSM-5 was used. The sample was added to 1500 ml of 0.3N alkaline NaCl solution and a magnetic s-tirrer was used to assure good mixing. As in the previous example the pM was used to monitor the exchange and adjustment was necessary every few hours with sodium hydroxide to maintain an alkaline pH in the range of 10~ The contancy of pH
over a 24-48 hours period was used as the criterion to terminate the exchange. Using this approach, large crystal ZSM-5 was prepared with total exchange time of one week.
The finished sample was fully exchanged as indicated by the atomic ratio o~ Na/Al shown in Table 1.

Cesium ZSM-5 was prepared by ion exchanging 15 ~ms of 14/30 mesh NII~ZSM-5 with 430 ml lM CsCl at room temperature. I'wo exchanges were made with pH in ~he range 10-11 adjusted with a dilute solution of CsOH. As in the case o~ Example 1, the finished catalyst was washed only once after the seco~d exchange with aqueous CsOH solution of pH=10-11 and dried at 130C. The finished sample was fully exchanged as indicated by the elemental analysis shown in Table 1.
Table 1 Compositlonal Analyses of Alkali Metal Exchanged zS~-5 NaZSM-5 (Example 21 CsZSM-5 (Example 3 Composition, wt%
M(Na or Cs) 1.02 12.0 30 SiO2 87.75 74.85 A1203 2.05 3.58 A~h 96.36 94.15 SiO2/A1203 73 36 ~; M /Al 1.1 1.3 '~ , ' . ' ~

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The residual acid ac-tivity of the alkali metal zeolite was measured in two ways: 1) the standard alpha test and 2) hexene-l isomeriza-tion test. The latter test is partieularly useful for rating low acid activity catalysts with alpha values below 1. The tes-t was carried out at 800F using a 5.3 mol ratio oE He and hexene-l, flowing at 20-300 ce/min over 2 to 100 mg oE ca-talyst mixed wi-th 1 ec 30/60 mesh Vyeor (HF treated and air ealeined) depending OIl activity.
For a catalyst of 1 alpha, the corresponding rating based on the hexene-l test would be 1300.
Table 2 Residual Acid Aetivity of Alkali Metal Exchanged ZSM-5 Catalyst Alpha Hexene-l ;Ex. 1 NaZSM-5 0.05 --~
Ex. 2 NaZSM-5 0.06 ~x. 2 NaZSM-5 9xlO 3 16 Ex. 3 CsZSM~5 0.05 -------20 Ex. 3 CsZSM-5 4xlO
Vyeor 3xlO 5 0.05 *calculated value 1=1800 khexene-l ~he combination of zeolites described above with hydrotreating catalysts offers unique processing advantages. It is shown below that low aeidity ZSM-5 sueh as NaZSM-5 is an effeetive hydrocarbon conversion catalyst which is non-aging, resistant to nitrogen and sulfux eompounds in the feedstoek. Furthermore, NaZSM-5 was found to have no demetalation activity at all, i.e., niekel and vanadium eompounds present in resids and heavy oils do not reaet over NaZSM-5 and pass through the eatalyst bed unaltered. Thus it is an idealsupport matrix for the mieron size demetalation/hydrotreating eataIyst by providing open ehannels ~or the resid molecules to reach the ; hydrotreating demetalation sites throughout a catalyst .

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~' ~65~ 22 partlcle and at the same time provide shape selective con-version capabill-tles -to upgrade heavy oils to naph-tha and low pour point dlstlllates.

Because of the upgrading capability and the fine dispersion of the demetalation/hydrotreating component, the catalyst is effective at a lower hydrogen pressure than that ls required by conventional resid hydrotreating catalysts. Instead of opera-tiny at 2000-3500 psig, as do most resid hydrotreating processes, the operating pressure can be reducPd to below 1500 psig with the composite catalyst.

The novel catalyst compositions can therefore reduce the cost of upgrading resids and heavy oils~ Significant savings in capital investment and operating cost can be realized by ~; virtue of -the low pressure requirement, long operat:Lng cycles and the regenerability of the catalyst. Add:itional benefits in the uplift of product value are also contemplated.
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~he alkali metal zeolites of this in~ention are utilized under conditions similar to those employed in aonventional hydrocracking although the zeolite catalyst does not contain - ~ a hydrogenation component as do true hydrocracking catalyst.
The conversion with the present catalyst is generally similar to that seen in hydrocracking with one very important dif-ference~ namely a highly advantageous low yield of gaseous hydrocarbons. That advantaye is enhanced by a characteristically - long onstream life of the catalyst.
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Sulfur appears to activate these catalysts for conversion of gas oils, whole crudes, residual stocks, lubricating oil fractions, shale oils, bitumens and heavy hydrocarbon charge stocks generally. Such mixtures generally contain sulfur ;~,~, , :
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~ 23 and an induction period is generally observed in the range of about 2~ to 48 hours to reach full activi-ty of the catalyst.
Alternatively, the catalyst may be presulfided by treatmen-t with hydrogen sulfide at about reaction temperature to avoid the induction periocl. Not wishing to be bound by theoxy, it is thought that sulfur in the feedstock provides an added beneficial effect for the operation of this class of catalysts.
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For installations having hydrogen available, it is preferred to operate the process under hydrogen pressure by the trickle technique with hydrogen flowing concurrently downward with mixed vapor and liquid phase hydrocarbons. In the absence of hydrogen, the process is preferably operated with a llquid-full reactor under sufficient pressure to maintain the hydrocarbons in the liquid phase.

Temperature o~ the reaction is between 650F. and 850E'., preferably between 700F. and 800F. Activity of -the catalyst drops off below about 700F., making it advisable to operate at a temperature above that level. However, in that particular embodimen-t of this invention in which the catalyst used is prepared by steaming to an alpha value of n.~t less than 5 followed by base exchange with alkali, satisfactory activity has been found at temperatues less than 700F. Many charge stocks will undergo some thermal cracking at temperatures above about 800F. with resultant production of undesired gaseous hydrocarbons thereby losing one advantage of the . .
~ invention to the extent that thermal crac]cing takes place.
.
Pressures employed will vary according to the technique ; being used. For liquid full reactor operation, the minimum~
pressure will be that necessary to maintain the charge in liquid phase at the temperature of reaction. In any event, the pressure will be above about 200 psi. There appears to be no maximum pressure limit imposed by effectiveness of the , .~; .
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catalyst, but costs for capital installation and operation of compressors and the like rise rapidly for pressures in excess of 2000 psi. It is preferred to operate below that level for economic reasons.
Space velocity will vary somewha~ with sulfur con-tent of the charge, permitting higher space velocity as sulfur increases above 0.5 wt.% to upwards of about 5.0 wt.%. In ge~eral, space velocity will range from about 0.1 liquid volume of hydrocarbon charge per volume of catalyst per hour tLHSV) up -to 5:0 LHSV. For most charge stocks, preferably LHSV will range from about 0.3 to 1Ø -.'. ~ .
15Conversion of heavy vacuum gas oil.

- ~Ieavy vacuum gas oil from Arab light crude (boiling range 800-1070F.) was converted at 750 psig over sodium ZSM-5 prepared in the manner described above. During the operation , hydrogen was introduced to the reactor with the charge at a rate corresponding to about 4000 standard cubic feet of hydrogen per barrel of feed. For purposes of comparison a run was made at the same pressure and hydrogen circulation, using a zinc palladium ZSM-5 which had an alpha rating above 150 as compared with alpha of less than 0.1 for the sodium zeolite. Conversion and product distribution data are shown in Table 3.
Table 3 30 ~ y~ NaZSM-5 ZnPdZSM-5 TempF 740 795 LHSV 0.5 0.5 Conversion, wt% 48.1 51.0 Products, wt.%
Cl-~C2,s 0.1 2.2 C3~C4 2.6 15.7 ; C -420F. - 21.0 14.5 ~ 5 -j 420-800F. 24.4 18.6 ~ 800F 51.9 49.0 :, :

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~ 25 NaZSM-5 is unexpec-tedly more ac-tive than ZnPdZSM-5 as indicated by the 45F lower reaction temperature required to achieve similar conversion. Also noted was that C4 products represent 5.6% and 35.1% for the low acidi-ty ca~alyst and ZnPd7.SM-5 respectively. The major shift in C4 yield was most unexpected.
The NaZSM-5 catalyst was run for one month without increase in temperature. The run was terminated while the catalyst was still active.
Example 5 Conversion of atmospheric resid.

Atmospheric residuum from Arab light crude was converted over cesium ZSM-5 and a comparable run was conducted over palladium ZSM-5. The latter catalyst was extrudate of 35 wt% alumina binder with 65wt ~ ZSM-5 of 70 sllica/alumlna ratio containing 0.5 wt.% of Pd. Inspection data of the charge are shown in Table 4.
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Properties of Arab light atmospheric resid Analysis, ~lemental,~
Arsenlc .oog Carbon 84.88 Hydrogen 11.24 Nlckel, ppm 11 Nitrogen .17 Sulfur 3.17 ; Vanadlum, ppm 36 . .
Ash from Petroleum, % 0.1 -30 Carbon Resid, Conradson, % 7;84 Dlstillation, F5% 68Q
10% 720 ggo ~35 Gravity, API 16.9 " ,Specific,60~F .9S35 Molecular Weight, vp lowering 523 .

, ~6~ 26 Table 4 Pour Point, F 50 Viscosity, KV 130F 152.9 " , ~V 212F 22.52 Conditions of reaction and conversion products are set out in Table 5.
Table 5 Conversion of Arab light atmospheric resid ;10 Catalyst CsZSM-5 PdZSM-5 Pressure 750 1250 Temperature 77$ 776 LHSV 0 5 0~5 Reactor EffLuent Composition,wt%
Cl 0.3 0.5 C2 0.3 1.2 C3 0.6 6.2 ; C4 0.9 5.4 20 c5~420 420-650 ~ 9.1. 6.2 ~ j 650-800 27.3 23.8 800-1000 - 22.5 16.9 25 1000~ il.2 34.2 Again the most striking dif~erence between these two catalysts is in the yields of C4 produc~s. Compared to PdZSM-5, CsZSM-5 produced less C4 and more naphtha and low pour point distillate ~rom the resid.

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Example 6 Conversion of waxy raffinate. Sodium ZSM-5 as above defined was compared with the hydrogen form of a 70 silica/alumina ZSM-5 as extrudate wit~ 35 wt.% alumina binder. Charge in the comparative runs was a fur~ural raffinate from Arab light boiling above 650F. Inspection data on that charge are shown in Table 6.
Table 6 Inspection data on Arab light waxy raffinate.
10 Gravity, API 29.1 Gravity, Specific 60F 0.8000 Pour Point, F 115 - KV 130F Centistokes . 38.47 KV 210F 9.91 SUS 130F Seconds 181.1 SUS 210F " . 58.9 ; Color, ASTM
Carbon Residue, ~wt (RCR) 0.13 Hydro~en, %w-t 13.78 :~ 20 Sulfur, ~wt 0.80 ~ Nitrogen, %wt 0.0053 :~. Refractive Index 70C 1.46466 :~; Aniline Point, F 239.4 :~ Distillation : 25 - IBP F
67~
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~70 90 . 925 ~ 960 : : 35 Reaction conditions and results obtained in the comparable runs are shown in Table 7.

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4 ~.8 9.1 C5 4.0 1.8 C6-650F 34.6 3.3 650F 51.0 73.3 Pour Point, F. 35 5 ~ ~ Viscosi-ty 100F 48.9 110.3 . ~ 210F 6.7 11 . 20 ~I 99 4 9O ~
- The Examples which follow serve to illustrate the particular embodiment of this invention in which a low acidity catalyst : is prepared, as descxibed above, by steaming ~ollowed by , ~ base exchange.

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5 hydrogen form by calcining in air at 1000F for 3 hrs. 15 grams o HZSM-5 so prepared was contacted with 100% steam at 800F for 44 hrs. The steam treated product was ~ound to have an alpha value of 34.

10 The steam treated product was added to an 1800 ml~of .6N
LiCl solution having a pH of 8.5 (pH is adjusted with .5N
LioH~. The mixture was maintained at room temperature for 48 hours with occasional agitation by swirling or stirring.
The pH of the solution was monitored fre~uently and ad~usted to 8-9 with 0.5N LioH as required. After 48 hours, the liquid was decanted and replaced with 1000 ml oE fresh L.iCl/LiOEI solution. The exchange was complete by 90 hours as judged by the constancy of the pH. The catalyst was washed with 1000 ml of dilute I,iO~I (pH - a to 9) solution and dried at 130C.

- Example 8 . Another batch of the alkali ZSM-5 was prepared starting with extrudate that had not been calcined. It was precalcined in : . air and then ammonium exchanged. The resulting ammonium .
~ orm of ZSM~5 was calclned in air for 2-3 hours at 1000F.

: 7 gm of the HZSM-5 so prepared was contacted with steam at 790F. The steamed product was found to ha~e an alpha value o 30. The final product was ion exchanged as in Example 7.

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Example 9 Another batch of NaZSM~5 was prepared in the same manner as in Example 7, except no calcination step was used. NH4ZSM-5 was contacted with 100~ steam at 800~F for 23 hours. The steam treated produc-t was found to have an alpha ~alue of 71. As in Example l, the steam treatecL product was exchanged with alkaline NaCl solution and a magnetic stirrer was used to assure good mi~ing.
.

The residual acid activity of the alkall metal zeolites prepared in Examples 7, 8 and 9 was measured by: l) the standard alpha test and 2) hexene-l isomerization tes-t.
(See Example 3 for test description~. The results are summarized in Table 8.
Table 8 RESlDUAL ACID ACTIVITY OF ALKALI METAI, Catalyst Alpha Hexene-l 20 Ex. 7 LiZSM-5 C 0.1 0.01 Ex. 8 LiZSM~5 ~ 0.1 , 0.09 ~Ex. 9 NaZSM-5 ~0.1 0.05 - Vycor ~ 0.1 0.003 25Example 10 Conversion Of Shengli Gas Oil and Taching ~hole Crude A continuous run of 46 days was used to process Shengli gas 30 oil (for 23 days) followed by Taching whole crude (for 23 days) over the catalyst of Example 7. The catalyst was not regenerated when the feed was changed. The system was maintained at 530 psig with hydrogen circulated at about 1500-2500 SCF/bbl.

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~6~ 31 Shengli gas oil ~boiling range 420-870F, 0.04~ Ni-trogen, 0.44~ sulfur, 70F pour point~ was passed over the catalyst at temperatures or from 371-~113C at L~ISV of 1.11-1.77. A
reaction product having high distillate yield with low pour 5 pOiIlt was obtained. The gasoline product, which has an unleaded research oct:ane n~nber greater than 90, could be used as blendiny stock. Whole Taching crude (boiling range Cl-1000F , 95Fpour point~ was dewaxed over the catalyst at 371C and LHSV of .68-1.38.
The LiZSM-5 catalyst was run for 46 days with ~ery little aging or deactivation. The run was terminated while the catalyst was still active.

Example 11 Conversion of Nigerian Gas Oil and Shengli Gas Oll A continuous run of 25 days was used to process Nigerian gas oil ~8 days) followed by Shengli gas oil (17 days) over the catalyst of Example 8. The catalyst was not regenerated when the feed was changed. Nigerian gas oil (IB 540-870F, .08% nitrogen, 0.23% sulfur, 95F pour point) was passed over the catalyst at temperatures from 371-399~C at LHSV of 0.77 to 2.4. Shengli gas oil (70F pour point) was passed over the catalyst at temperatues from 4-10-416~C at LHSV of 1 3-l.5. The conditions ~nd re~u1ts a-e shown in Tdb1e 9.

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Ln o : Ln o ~ g 2 ~ 33 The ammonium form of ZSM-5 extrudate of the same kind as used in Example 7 was contacted with 100~ steam at 800F for 24.5 hours. The steam treated product was found to have an alpha value of 78. The stearned extrudate was lithium-exchanged to an alpha of less than 0.3.

Example 13 Whole Taching crude was processed over the catalyst of Example 12 at 650-760F, 1.0~125 LHSV and methane circulation rate of 1000-1500 SCF/BBL. The results are shown in Table lO and Figure 3.

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35 ~L69~1 Exam~e 14 The ammonium form of ZSM-5 extrudate was calcined in a s-tatic air environment. The calcined product was contacted ~ith 100% s-team at 300F for 89 hours. The steam treated product was added to lN Nl14NO3 solution having a pH of 4.5.
The mixture was maintained at 200F for 4 hours with continuous stirring, -then the liquid was decanted and the catalyst was washed with de-ionized water. The resulting catalyst was then Na-exchanged (pH of exchange 8-9) to an alpha value of 1Ø The resulting material was further exchanged with 0.5N
NaNO3 aqueous solution of pH 9.0 at 200F for 1 hour. The final catalyst was washed with dilute NaOH aqueous solution (pH = 8.9) as in Example 4 and dried at 120C. The final catalyst had an alpha value of~0.4.

,..~, - Taching whole crude was passed over the catalyst of Example 14 a-t 650-700F, 1 LHSV, 300 psig, and gas circulation rate of zero SCF~BBL. The results are shown in Figure 4.

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Claims (23)

WHAT IS CLAIMED IS:

1. A process for converting a high boiling hydrocarbon charge fraction to liquid products of lower boiling range which comprises contacting said charge fraction with a steamed crystalline zeolite characterized by a silica/alumina ratio greater than 12, a constraint index between about 1 and about 12, and substantially no activity for cracking n-hexane, said activity having been substantially eliminated by base-exchange of said steamed zeolite with an alkali metal cation, said contacting being conducted at about 650 to 850°F, and a space velocity of 0.1 to 5.0 LHSV.

2. A process according to Claim 1 wherein said alkali metal is sodium.

3. A process according to Claim 1 wherein said alkali metal is lithium.

4. A process according to Claim 1 wherein hydrogen is supplied with said charge to said contacting.

5. A process according to Claims 1, 2 or 3 conducted at a temperature of about 700 to 800°F.

6. A process according to Claims 1, 2 or 3 wherein said zeolite is zeolite ZSM-5.

7. A process for reducing the pour point of a wax-containing hydrocarbon oil which comprises contacting said oil at 650 to 850°F, a space velocity of 0.1 to 5.0 LHSV and a pressure not less than about 200 psig, with a catalyst having an alpha value not greater than about 1.0, said catalyst being prepared from a composition comprising a precursor crystalline zeolite characterized by a silica/alumina ratio greater than 12, a constraint index between about 1 and about 12, and an alpha value greater than about 20, said preparation including steaming said precursor to reduce its alpha value to not less than about 5 and ion-exchanging said steamed precursor with an alkali metal cation under conditions effective to reduce its alpha value to not greater than about 1Ø

8. The process described in Claim 7 wherein said catalyst comprises a crystalline zeolite having the X-ray diffraction pattern of ZSM-5.

9. The process described in Claim 7 or 8 wherein said steamed precursor is contacted with aqueous ammonium nitrate for about 0 25 to 10 hours at a temperature of 70° to 212°F
prior to said ion-exchange.

10. The process described in Claim 7 or 8 wherein said catalyst has an alpha value not greater than about 0.5.

11. The process described in Claim 7 or 8 wherein said alkali metal cation is lithium or sodium.

12. The process described in Claim 7 or 8 wherein said contacting is conducted in the presence of hydrogen.

13. The process described in Claim 7 or 8 wherein said wax-containing hydrocarbon oil is selected from the group consisting of a whole crude oil, a residual fraction of a whole crude oil, and a distillate oil.

14. The process described in Claim 7 or 8 wherein said contacting is conducted in the presence of gaseous hydrogen.

15. The process described in Claim 7 or 8 wherein said contacting is conducted in the presence of methane.

16. A catalyst composition comprising an inorganic matrix and from 10 to 90 wt.% of the alkali metal form of a steamed crystalline zeolite having a silica/alumina ratio above 12, a constraint index between about 1 and about 12, and an alpha value not less than about 5, said catalyst having substantially no activity for cracking n-hexane.

17. The catalyst composition described in Claim 16 wherein said alkali metal is lithium or sodium.

18. The catalyst composition described in Claim 16 or 17 wherein said inorganic matrix is alumina.

19. The catalyst composition described in Claim 16 or 17 including a hydrogenation metal.

20. The catalyst composition described in Claim 16 wherein said crystalline zeolite is ZSM-5.

21. The catalyst composition described in Claim 20 wherein said inorganic matrix is alumina.

22. The catalyst composition described in Claim 20 wherein said alkali metal is lithium or sodium.

23. The catalyst composition described in Claim 20, 21 or 22 including a hydrogenation metal.