CA1187827A - Method for enhancing catalytic activity - Google Patents

Method for enhancing catalytic activity

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Publication number
CA1187827A
CA1187827A CA000394238A CA394238A CA1187827A CA 1187827 A CA1187827 A CA 1187827A CA 000394238 A CA000394238 A CA 000394238A CA 394238 A CA394238 A CA 394238A CA 1187827 A CA1187827 A CA 1187827A
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Canada
Prior art keywords
zsm
dewaxing
raffinate
zeolite
oil
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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CA000394238A
Other languages
French (fr)
Inventor
Robert E. Holland
Samuel A. Tabak
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ExxonMobil Oil Corp
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Mobil Oil Corp
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Classifications

    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G67/00Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only
    • C10G67/02Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only
    • C10G67/06Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only including a sorption process as the refining step in the absence of hydrogen
    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2400/00Products obtained by processes covered by groups C10G9/00 - C10G69/14
    • C10G2400/10Lubricating oil

Abstract

METHOD FOR ENHANCING CATALYTIC ACTIVITY

ABSTRACT

Catalytically dewaxed lubricating base stock oils that have improved resistance to oxidation are produced by pretreating the waxy furfural raffinate with a zeolite sorbent prior to dewaxing with a zeolite catalyst such as ZSM-5, and conducting the dewaxing at a reduced temperature not to exceed about 357°C to 371°C (675° to 700°F).

Description

7&~

F-0787 l-MET~D FOR ENHANCING CATALYTIC ACTIVITY

This invention relates to processes that employ crystalline molecular sieve zeolites as catalysts by pretreatment of the feed to make it more readily converted by the catalyst. This invention is 5 advantageous for the catalytic dewaxing of petroleum fuels and lubricants at reduced dewaxing temperatures to produce high quality lube base stock oil having a predetermined pour point and higher oxidation stability.
The present invention provides a process for preparing a high lO quality lube base stock oil having a predetermined pour point in the range of from -32C to -1C (-25 to ~30F) from waxy crude oil by extracting a distillate fraction that boils within the range of 232C
to 593C (450 to 1100F) or a deasphalted vacuum residuum fraction of the waxy crude with a solvent selective for aromatic hydrocarbons to 15 yield a raffinate from which undesirable compounds have been removed, contacting the raffinate and hydrogen gas with a dewaxing catalyst under dewaxing conditions effective to impart the predetermined pour point, the catalyst comprising a first crystalline zeolite having a dry crystal framework density of not less than about 1.6 grams per 20 cubic centimeter and a constraint index of from l to 12t thereby converting wax contained in the raffinate to lower boiling hydrocarbons and, topping the dewaxed raffinate to remove therefrom components of a low molecular weight, characterized by pretreating the raffinate, prior to dewaxing, with a sorbent comprising a second 25 crystalline zeolite having an effective pore diameter equal to or larger than the first crystalline zeolite under a combination of conditions selected ~rom a temperature of from 2C to 177C (35 to 350F), a pressure of lOl to 20786 kPa (O to 3000 psig), and a contact time equivalent to a LHSV of 0.1 to lOO hr. 1, the combination being 30 effective to provide a pretreated raffinate characterized by an initial e~uilibrium temperature not exceeding from 357C to 371C
(675 to 700F) and at least 14C (25F) lower than that obtained with the raffinate without pretreatment when dewaxed at about 1 LHSV and t~

F~0787 2-dewaxing the raffinate at a temperature not to exceed the lesser of the equilibrium te~perature of the raffinate without pretreatment minus 14C (25F), or 371C (700F).
Modern petroleum refining is heavily dependent on catalytic 5 processes which chemically change the naturally occurring constituents of petroleum. Such processes include hydrocracking, catalytic cracking, reforming and hydrotreating. Historically, the processes all depended on the discovery that chemical change could be induced by con~acting a suitable petroleum fraction with a suitable porous inorganic solid at elevated temperature. If hydrogen under pressure is essential to the desired conversion, such as in hydrocracking, a hydrogenation metal is included with the porous catalyst to make the hydrcgen effective.
The porous inorganic solids that were originally found useful for catalytic processes included certain clays, aluminas, silica-aluminas and other silicas coprecipitated with magnesia, for example, and such solids are still extensively used in the industry.
In general, all of these solids had pores that were not of uniform si~e, and most of the pore volume was in pores having diameters larger than about 3û Angstroms, with some of the pores as large or larger tnan lO0 Angstroms. As will become evident from the following discussion, a large Fraction of the molecules present in a hydrocarbon feed, such as a gas oil, is capable of entering the pores of the typical porous solids described above.
In recent years, much attention has been given to the synthesis and properties of a class of porous solids known as "molecular sieves." rhese are porous crystalline solids usually composed of silica and alumina and, because the pore structure is defined by the crystal lattice, the pores of any particular molecular sieve have a uniquely determined, uniform pore diameter. The pores of these crystals are further distinguished from those in the earlier used solids by being smaller, i.e., by having effective pore diameters not greater than about 13 Angstroms. These solids, when dehydrated~
act as sorbents that discriminate among molecules of different shape, and for that reason were first called "molecular sieves" by J. W.

, ~7~

Mc~ain. The term "effective pore diameter" as used herein means the diameter of the most constricted part of the channels of the dehydrated crystal as estimated from the diameter o~ the largest molecule that the crystal is capable of sorbing. Zeolite molecular sieves are available that have effective pore diameters ranging from aoout 3 Angs-troms, which is too small to allow occlùsion of any hydrocarbon in the pores, to about 13 ~ngstrcms, which allows occlusion of molecules as large as 1,395-triethylbenzene. The structures and uses of these solids are described in "Zeolite Molecular Sieves," by Donald W. Breck, John Wiley and Sons, New York (1974). As indicated by Breck, the zeolite molecular sieves are useful as adsorbents ~ibid7 page 3), and in catalysts (ibid, page 2).
In spite of the small pores which are characteristic of zeolite molecular sieves, certain of these materials have been found to be highly effective as hydrocarbon conversion catalysts. The conversion of gas oil to gasoline and distillate by catalytic cracking, the alkylation of benzene to ethylbenzene, the isomerization of xylenes and the disproportionation of toluene all involve molecules which are smaller in critical diameter than 1,3,5-triethylbenzene, and such molecules are occluded and acted upon by zeolite molecular sieves having an effective pore diameter of about 10 Angstroms. A
particularly interesting catalytic transformation which requires a molecular sieve catalyst is the reduction of the pour point of waxy distillates and residual hydrocarbon fractions. Effective pour point reduction depends on the selective conversion of normal, high melting point paraffin molecules that have an effective critical diameter of about 5 Angstroms to substances of lower moIecular weight that are easily separated from the low-pour point product. Effective catalytic dewaxing depends at least in part on the regularity of the pore size of the crystalline zeolites, which allows selective conversion of unwanted constituents.
The developments briefly described above are only indicative of the commercial importance of the molecular sieve zeolites and of the academic interest in these materials, which is more accurately reflected by the thousands of patents and publications on the F-0787 ~4~

subject. By far the major part of thls importance stems from the catalytic properties that may be found in appropriate circumstances within the relatively small pores, together with the regularity in the shape o~ the pores which permits the molecular sieve catalyst to act selectively on molecules having a particular shape. This latter phenomenon has come to be known as "shape-selective catalysis." A
review of the state of the catalytic art is found in "Zeolite Chemistry and Catalysis~ by Jule A. Rabo, ACS Monograph 171, American Chemical Society, Washington, D.C. (1976). See particularly Chaoter 12 titled "Shape Selective Catalysis."
The dewaxing of oils by shape selective cracking and hydrocracking over zeolites of the ZSM-5 type is discussed and claimed in U.S. Reissue Patent No. 28,398. U. S. Patent No. 3,956,102 discloses a particular method for dewaxing a petroleum distillate with a ZSM-5 type catalyst. Typical aging curves are shown in sheet 2 of the drawing of this patent. U. S. Patent No. 3,894,~38 discloses that the cycle life of a ZSM~5 dewaxing catalyst is longer with a virgin feed stream than it is with the same feedstream after it has been hydrotreated. Catalytic dewaxing of petroleum stocks in which a mordenite type of molecular sieve catalyst is used is deæribed in the Gil and Gas Journal, January 6, 1975 issue at pages 69-73. See also U. S. Patent No. 3,668,113.
It has now been found that, in general, a dewaxing process in which a zeolite molecular sieve dewaxing catalyst is used becomes more effective when the feed, prior to dewaxing, is contacted under sorption conditio~s, as more fully desoribed hereinbelow, with a zeolite molecular sieve having an effective pore diameter at least as large as the dewaxing catalyst. The terms "more effective~ as used herein means that the dewaxing catalyst behaves as if it were catalytically more active or more resistant to aging when the feed stream is pretreated as disclosed. Thus7 the refiner, when using the improved method of this invention to reduce the pour point of a waxy feed to some predetermined temperature9 may elect to take advantage of the increased catalyst activity by reducing the inventory of dewaxing catalyst or by reducing the operating temperature of the zeolite ~7~7 F 07~7 -5-dewaxing catalyst from the temperature required by the prior art; or, he may elect to increase the space velocity of the feed and obtain more product with the same pour point reduction as was obtained by the prior art method; or, he may extend the cycle life of the dewaxing catalyst by ru ming the process with a lo~2r initial equilibrium temperature and finishing with the same end of cycle temperature as in the prior art.
It is not known precisely why pretreating the feed with a zeolite molecular sieve maintained under sorption con~itions serves to increase the effectiveness of the dewaxing catalyst. While not wishing to be bound by theory, it may be postulated that the feed contains minute amounts of catalytically deleterious impurities which, in the prior art, were sorbed by the catalyst and served as catalyst poisons. It is further speculated that the content of these poisons is reduced by the pretreatment method of this invention with the effect that the catalytic activity of the dewaxing catalyst appears to be increased or that the reactivity of the feed has been increased.
It seems appropriate to consider the pretreatment deæribed herein as a method for refining the feed, and that term will be used herein in the context and spirit of this paragraph. The precise nature or composition of the catalyst poisons is not known, but again one may speculate that basic nitrogen compounds, and oxygen and sulfur compounds, may be involved.
It should be noted that the zeolite molecular sieve sorbent, as will be illustrated further oelow, is unusually effective in increasing the apparent activity of the dewaxing catalyst.
Substitution of a clay or other sorbent for the zeolite also may produce some increase, but of much lesser magnitude, even though the clay may remove a greater fraction of nitrogen compounds than is removed by the zeolite. And, although it may prove useful in some instances to measure basic nitrogen level, for example, as an index for degree of refinement of the feed, an example later presented herein suggests that such a measurement by itself may be misleading.
In brief, it is conceivable that the zeolite sorbent selectively removes and effectively ret~ins those poisons that have a shape sufficiently small to enter the catalyst pores, leaving only the 7~3~'7 F-0787 -6~

larger poisons available for contact with the catalyst. Since these can act only on non-selective surface sites, they may in some cases serve to increase the shape selectivity of the dewaxing catalyst, or at worst to do little harm.
Contemplated as within the scope of this invention is to regenerate the zeolite molecular sieve sorbent at intervals, as needed.
Figure 1 illustrates one embodiment of the dewaxing process of this invention.
The feed to be dewaxed by the process of this invention may be any waxy hydrocarbon oil that has a pour point which is undesirably high. Petroleum distillates such as atmospheric tower gas oils, kerosenes, jet fuels, vacuum gas oils, whole crudes, reduced crudes and propane deasphalted residual oils are contemplated as suitable feeds. Also contemplated are oils derived from tar sands, shale, and coal. for purposes of this invention, all of the above deæribed feeds may be considered suitable and all of these feeds are expected to benefit when dewaxed by the method of this invention.
The first step of the process of this invention requires that the feed be treated by contact with a sorbent under sorption ~ 20 conditions effective to remove at least some of the deleterious ; impurity. These conditions may cover a fairly wide range of time, temperature and pressure, and may be conducted in the absence or presence of hydrogen. The conditions, both broad and preferred, for ; this step of the process are indicated in Table I.
The impurities deleterious to the catalysts, or poisons, will be referred to herein as "contaminants" regardless of whether these occur naturally associated with the feeo or are acquired by the feed from some known or unknown source during transportation, processing, etc.

7~

TABLE I. S~RPTION CONDITIONS
Broad Preferred Temperature, Pressure psig n!/3ooo 25/1500 kPa 101/20786 274/10443 LHSV, hr 0.1/100 0.2/20 In general, although it is preferred to conduct the treating step in a flow system, wherein the sorbent particles are in the form of a fixed bed of 0.16 cm (1/16 inch) to 0.64 cm (1/4 inch) extrudate or pellets, other modes of contact may be employed such as slurrying the feed oil with a finely powdered sorbent followed by centrifugation and recycle of the sorbent. The precise conditions selected for the sorption step will be determined by various considerations, including the nature oF the feed and the desired degree of refinement, the latter being judged from the observed catalytic consequences of the treatment.
For purposes of this invention, the sorbent consists of a molecular sieve zeolite having pores with an effective diameter of` at least about 5 Angstroms. Illustrative of zeolites with pores of 5 Angstroms are zeolite A in the calcium salt form, chabazite and erionite, which sorb normal paraffins but exclude all other molecules of larger crltical diameter. Other zeolites which may be used which have larger pore diameters include zeolite X, zeolite Y, offretite and mordenite. The last group of zeolites sorb molecules having critical diameters up to about 13 Angstroms, and all of them sorb cyclohexane freely.
In addition to the zeolites already enumerated, any of the zeolites described more fully hereinbelow which are useful as dewaxing catalysts also may be used as sorbentsO In fact, in a preferred embodiment of this invention, the zeolite utilized as sorbent and as dewaxing catalyst have the same crystal structure~ Since the dewaxing catalyst will be more fully described hereinbelow, it is unnecessary at this point to repeat the description.

~7~

In general, the pretreated feed is separated from the sorbent and passed to the catalytic dewaxing step where its pour point is reduced, usually by selective conversion of the high molecular weight waxes to more volatile hydrocarbon fragments.
Various emtodiments of the present invention are contemplated. In one of these, the feed is contacted with a dewaxing catalyst under sorption conditions, after which a pretreated feed is recovered and passed to storage. The material used as sorbent is now treated9 for example with steam at elevated temperature, to remove the sorbed deleterious impurity, and the stored treated hydrocarbon is passed over the regenerated sorbent now maintained at dewaxing conditions. In general, however, it is more effective to employ at least one separate bed of molecular sieve zeolite as sorbent, as will now be illustrated by reference to Figure 1 of the drawing~
Figure 1 of the drawing illustrates one embodiment of the present lnvention. A hydrocarbon oil feed, such as a gas oil with a pour point of 24~C (75F), is passed via line 1 to sorption tower 2 which is filled with a molecular sieve zeolite such as ZSM-5 cnntaining a small amount of nickel. Valve 3 is of course open in this stage of the operation, and valve 4 is maintained closed. The treated oil passes out of sorption tower 2 via line 5 and is heated to dewaxing temperature in furnace 6. Valve 7 is maintained open during this phase of the operation and valve 8 is maintained closed. The heated oil is passed from the furnace via lines 9 and lû along with hydrogen introduced via line 11 to the catalytic dewaxing reactor 12 filled with ZSM-5 dewaxing catalyst that contains a small amount of nickel. The dewaxed oil and cracked fragments together with excess hydrogen a~e passed from the dewaxing reactor 12 via line 13 to hiyh pressure separator 1~. The excess hydrogen passes from high pressure separator 14 via lines 15 and 11 and is recycled to the dewaxing reactor. Fresh make-up hydrogen is added via line 16. A bleed stream of gas is removed via line 19. The dewaxed oil and light ends are removed from the high pressure separator via line 17 and are passed to downstream facilities for recovering a dewaxed oil having a pour point of -7C (20F), for example, and the separated light fraction.

37i~

After a cel:tain period of operation, the sorbent contained in vessel 2 becomes ineffective and needs to be regenerated. This may be done by shutting valves 3 and 7 and introducing st:ripping steam via line 18 and valve 4 into vessel 1 and removing the excess steam and 5 deleterious impurities via valve 8 and line 20. Various stripping gases may be used in place of steam such as heated air, nitrogen or hydrogen gas. The sorbent also may be regenerated by burning in air at elevated temperature. The preferred methods of regeneration are to use steam at about 177C (35û~F) or hydrogen gas at about 482C
(900F).
It will of course be evident to one skilled in the art that instead of the single sorption tower shown in Figure 1, two such towers may be used such that one of them is being regenerated while the other is on stream to permit continuous rather than irttermittant 15 dewaxing.
The step of catalytically dewaxing the pretreated feed is illustrated for different hydrocarbon oils in U.S. Reissue Patent No.
28,398 and in U.S. Patent Nos. 3,956,102 and U.S. 4,137,148, for e)sample. It will be understood that the reaction conditions will be 20 milder, in general, when adapting the dewaxing step to the pretreated t`eed as describcd herein. The dewaxing step may be conducted with or without hydrogen, although use of hydrogen is preferred. It is contemplated to conduct the dewaxing step at the dewaxing conditions shown in Table II.

TABLE II. ~ AXING STEP
Wit~out~
Broad Preferred Temperature F 400~1000 500/800 C 204~538 260~427 LHSV, hr~l O.3~20 0.5~10 Pressure psig 0~3000 25J1500 kPa 101~20786 274~10443 '~ith Hydrogen Temperature F 400~1000 500/800 LHSV7 hr~l 0.1/lo 0.5/4.0 H2/HC mol ratio 1~20 2~10 Pressure Psi9 0~3000 200~1500 kPa 101~20786 274~10443 A particularly preferred embodiment of the dewaxing pracess of this invention is provided when the molecular sieve zeolite of the dewaxing catalyst is selected from a member of a novel class of zeolitic materials which exhibit unusual properties. Although these zeolites have unusually low alumina contents, i.e. high silica to alumina mole ratios9 they are very active even when the silica to alumina mole ratio exceeds 30. The activity is surprising since catalytic activity is generally attributed to framework aluminum atoms and/or cations associated with these aluminum atcms. These zeolites retain their crystallinity for long periods in spite of the presence of steam at high t~oerature which induces irreversible collapse of the framework of other ~eolites, e.g. of the X and A type.
Furthermore, carbonaceous deposits9 when formed, may be removed by burning at higher than usual temperatures to restore activity. These zeolites, used as catalysts, generally have low coke-forming activity and therefore are corducive to long times on stream between regenerations.
2~

F-0787 -ll-An important characteristic oF the crystal structure of this novel class of zeolites is that it provides a selective constrained access to and egress from the intracrystalline free spæ e by virtue of having an effective pore size intermediate between the small pore Linde A and the large pore Linde X, i.e. the pore windows of the structure are of about a size such as would be provided by 10-membered rings of silicon atoms interconnected by oxygen atoms. It is to be understood, of couxse, that these rings are those formed by the regular disposition of the tetrahedra making up the anionic framework of the crystalline zeolite, the oxygen atoms themselves being bonded to the silicon (or aluminum, etc.? atoms at the centers of the tetrahedra.
The silica to alumina mole ratio referred to may be determined by convertional 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. Although zeolites with silica to alumina mole ratios of at least 12 are useful, it is preferred to use zeolites having higher ratios than about 30. In addition, zeolites as otherwise characterized herein but which are substantially free of aluminum, that is zeolites having silica to alumina mole ratios of up to infinity, are found to be useful and even preferable in some instances. Such "high silica" or '1highly siliceous" zeolites are interded to be included within this description. Also included within this definition are substantially pure silica analogs of the useful zeolites described herein, that is to say those zeolites having no measurable amount of aluminum (silica to alumina mole ratio of infinity) but which otherwise embody the chracteristics disclosed.
The novel class of zeolites, after activation, acquire an intracxystalline sorption capacity for normal hexane which is greater than that ~or water, i.e. they exhibit "hydrophobic" properties. This hydrophobic character can be used to advantage in some applications.
The novel class of zeolites useful herein have an effective pore size such as to freely sorb normal hexane. In addition, the structure must provide constrained access to larger molecules. It is '7~

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 formzd by ~-membered rings of silicon and aluminum atoms, then access by molecules of larger cross-section than normal hexane is excluded and the zeolite is not of the desired type.
~in~ows of 10-membered rings are preferred, although in some instances excessive puckering of the rings or pore blockage may render these zeolites inefFective.
Although 12-membered rings in theory generally would not offer sufficient constraint to praduce advantageous conversions, it is noted that the puckered 12-ring structure of TMA offretite does show some constrained access. Other 12-ring structures may exist which may be operative for other reasons such as the presence of cations which may restrict the pore diameter. Therefore, it is not the present lS intention to entirely judge the usefulness of a particular zeolite solely from theoretical structural considerations.
Rather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained access to molecules of larger cross-section than normal paraffins, a simple determination of the 'IConstraint Index" as herein defined 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 acoording 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 540C for at least 15 minutes. The zeolite is then flushed with helium and the temperature is adjusted between 290C and 510~C to give an overall conversion of between 10% and 60%. The mixture of hydrocarbons is passed at 1 liquid hourly space velocity (i.e., 1 volume of liquid hydrocarbon per volume of zeolite per hour) over the zeolite with a helium dilution to give a helium to (total) hydrocarbon mole ratio of 4:1. After 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 hydrocarbons.

While the above experimental procedure will enable one to achieve the desired overall conversion of 10 to 609' for most zeolite samples and represents preferred corditions, it may occaslonally be necessary to use somewhat more severe conditions for samples of very low activity, such as those having an exceptionally high silica to alumina mole ratio. In those instances, a temperature of up to about 540C 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 lo%.
The "Constraint Index" is calculated as follows:
Constraint Index =
log10 (fraction of hexane remaining) The Constraint Index approximates the ratio of the cracking rate cunstants for the two hydrocarbonsO Zeolites suitable for the present invention are those having a Constraint Index of 1 to 12.
Constraint Index (CI) values for some kypical materials areo C.I.
ZSM-~4 0 5 ZSM-5 8.3 ZSM-ll 8.7 ZSM-23 9.1 ZSM 35 4~5 TMA Offretite 3.7 Clinoptilolite 3.~
H-Zeolon (mordenite) 0 4 Qmorphous Silica-Alumina 0.6 Erionite 38 The above-described Constraint Index is an important and even critical definition of those zeolites which are useful in the instant invention. The very nature of this parameter and the recited technique by which it is determined7 however, admit of the possibility that a given zeolite can be tested under somewhat different conditions and thereby exhibit different Constraint Indices. Constraint Index ~7l~

seems to vary somewhat with severity of operation (conversion) and the pre ænce or absence of binders. Like~iset other variables such as crystal size of the zeolite, the presence of occluded contaminants, etc., may affect the constraint index. Therefore, it will be appreciated that it may be possible to so select test conditions as to establish more than one value in the range of 1 to 12 for the Constraint Index of a particular zeolite. Such a zeolite exhitits the constrained access as herein defined and is to be regarded as having a Constraint Index in the range of 1 to 12. Also contemplated herein as having a Constraint Index in the range of 1 to 12 and therefore within the scope of the defined novel class of highly siliceous zeolites are those zeolites which, ~hen tested under t~o or more se~s of conditions within tne above-specified ranges of temperature and conversion, produce a value of the Constraint Index slightly less than 1, e.g.
û.9, or somewhat greater than 12, e.g. 14 or 15, with at least one other value within the range of 1 to 12. Thus, it should be understood that the Cûnstraint Index value as used herein is an inclusive rather than an exclusive value. That is, a cr~stalline zeolite when identified by any combination of conditions within the testing definition set forth herein as having a Constraint Index in the range o~ 1 to 12 is intended to be included in the instant novel zeolite definition whether or not the same identical zeolite, when tested urder other of the defined conditions, may give a Constraint Index value outside of the range of 1 to 12.
The novel class of zeolites defined herein is exemplified by ZSM-5, ZSM-ll, ZSM-12t ZSM-23, ZSM-35, ZSM-38, ZSM-48, and other si~llar materials.
ZSM-5 is descrited in greater detail in U.S. Patents No.
3,702,886 and Reissue 29,948, ZSM-ll in U.S. Patent No. 3,709,979, ZSM-12 in U.S. Patent No. 3,832,449, ZSM-23 in U.S. Patent No.
4,076,842, ZSM-35 in U.S. Patent No. 4,016,245, ZSM-38 in U.S. Patent No. 4,046,859 and ZSM-48 in EP-A-23089, published January 28, 1981 and EP-A-15132, published September 3, 1980.

i i /

The specific zeolites described, when prepared in the presence of organic cations, are substantially catalytically inactive, possibly because the intra-crystalline free space is occupied by organic cations from the forming solution. They may be activated by heating in an inert atmosphere at 5~0C for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 540C in air. The presence of organic cations in the forming solution may not be absolutely essential to the formation of this type zeolite; however, the presence of these cations does appear to favor the formation of this special class of zeolite. More generally, it is desirable to activate this type catalyst by base exchange with ammonium salts followed by calcination in air at about 54ûC for from about 15 minutes to about 24 hours.
Natural zeolites may sometimes be converted to zeolite structures of the class herein identified by various activation procedures and other treatments such as base exchange, steaming9 alumina extraction and calcination, alone or in combinations. Natural minerals which may be so treated include ferrierite, brewsterite~
stilbite, dachiardite, epistilbite, heulandite, and clinoptilolite.
The preferred crystalline zeolites for utilization herein include ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48, with ZSM-5 and ZSM-ll being particularly preferred.
In a preferred aspect of this invention, the zeolites hereof are selected as those providing among other things a crystal framework density, in the dry hydrogen form, of not less than about 1.6 grams per cubic centimeter. It has been found that zeolites which satisfy all three of the discussed criteria are most desired for several reasons. When hydrocarbon products or by-products are catalytically formed, for example, such zeolites tend to maximize the production of gasoline boiling range hydrocarbon products. Therefore, the preferred zeolites useful with respect to this invention are those having a Constraint Ir,dex as defined above of about 1 to about 12, a silica to alumina mole 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 may be calculated from the number of silicon plus ~17~2~

aluminum atcms per 1000 cublc Angstroms, as given, e.g., on Page 19 of the article ZEOLITE STRUCTURE by W. M. Meier, PROCEEDINGS OF THE
CONFERENCE ON MOLECJLPR SIEVES, (Lor~on, April 1567) published by the Society of Chemical Industry, London, 1968.
When the crystal structure is unknown, the crystal framework density may be determined by classical pycnometer techniques. For exarnple, it may be determined by immersing the dry hydrogen form of the zeolite in an organic solvent which is not sorbed by the crystal.
Or, the crystal density may be determined by mercury porosimetry, since mercury will fill the interstices between crystals but will not penetrate the intracrystalline free space.
It is possible that the unusual sustained activity and stability of this special class of zeolites is associated with its high crystal anionic framework density of not less than about 1.6 grams per cubic centirneter. This high density must necessarily be associated with a relatively small amount of free space within the crystal, which might be expected to result in more stable structures.
This free spæ e, hawever, is important as the locus of catalytic activity.
Crystal framework densities of some typical zeolites, including some which are not within the purview of this invention, are:
Void Frarnework Volume ~ y___ __ Ferrierite 0.28 cc/cc 1.76 g/cc Mordenite .28 1.7 ZSM-5, -11 .29 1.79 ZSM-12 - 1.8 ZSM-2} - 2.0 Dachiardite .3~ 1.72 L .32 1.61 Clinoptilolite .34 1.71 Laurnontite .34 1.77 ZSM~4 (Omega) .38 1.65 Heulandite .39 1.69 P .41 1.57 Offretite .40 1.55 Levynite .40 1.54 Erionite .35 1.51 Gmelinite .44 1.46 Chabazite .47 1.45 A .5 1.3 Y .48 1.27 F-07~7 -17-~ hen synthesized in the alkali metal form, the zeolite 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 form to yield the hydrogen form. In addition to the hydrogen form, other forms of the zeolite wherein the original alkali metal has been reduced to less than a~out 1.5 percent by weight may be used. Thus, the ori~inal alkali metal of the zeolite may be replaced by ion exchange with other suitable metal cations of Groups I through VIII of the Periodic Table, including, by way of example, nickel, copper, zinc, palladium, calcium or rare earth metals.
In practicing a particularly desired chemical conversion process9 it may be useful to incorporate the a~ove-described crystalline zeolite with a matrix comprising another material resistant to the temperature and other conditions employed in the process.
Useful matrix materials include both synthetic and naturally occurring substances, as ~ell as inorganic materials such as clay, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be composited with the zeolite include those of the montmorillonite and kaolin families, which families include the sub-bentonites and the kaolins commonly krown as ~ixie, McNamee-Georgia and Florida clays or others in which the main mineral 2s constituent is halloysite, kaolinite, dickite, nacrite or anauKite.
Such clays can be used in the raw state as originally mined or initially subjected to calcination, æid treatment or chemical modi~ication.
In addition to the foregoing materials, the zeolites employed herein may be composited with a porous matrix material, such as alumina, silica-alumina, silica-magnesia, silica-zirconia, si.lica-thoria, silica-beryllia, and silica-titania9 as well as ternary compositions, such as silica-alumina-thoria, silica alumina-zirconia, silica-alumina magnesia and silica~magnesia-~irconia. The matrix may be in the form of a cogel. The relative proportions of zeolite 37~7 component and inorganic oxide gel matrix, on an anhydrous basis, may vary widely with the zeolite content ranging from between about 1 to aoout 99 percent by weight and more usually in the range of about 5 to about 80 percent by weight of the dry composite.
The process of this invention has been described up to this point in terms of removal of wax from any hydrocarbon oil, including jet fuels9 gas oils and whole crudes. A particular embodiment of this invention is applicable to lube oil stocks, and this embodiment may be used to prepare low pour point lube oil stccks with superior oxidation resistance compared with such stocks catalytically dewaxed without benefit of this invention.
Refining suitable petroleum crude oils to obtain a variety of lubricating oils which function effectively in diverse environments has become a highly developed and comolex art. Qlthough the broad principles involved in refining are qualitatively understood, the art is encumbered by quantitative uncertainties which require considerable resort to empiricism in practical refining. Underlying these quantitative uncertainties is the ccmplexity of the molecular constitution of lubricating oils. Because lubricating oils for the most part are based on petroleum fractions boiling above about 232C
; (450F), the molecular weight of the hydrocarbon constituents is high and these constituents display almost all conceivable structures and struct~re types. This complexity and its consequences are referred to in "Petroleum Refinery Engineering", by W. L. Nelson, McGraw Hill Book Company, Inc.~ New York, N.Y., 1958 (Fourth Edition).
In general, the basic notion in lubricant refining is that a suitable crude oil, as-shown by experience or by assay, contains a quantity of lubricant stock having a predetermined set of properties such as, fo~ example, appropriate viscosity, oxidation stability and maintenance of fluidity at low temperatures. The process of refining to isolate that lubricant stbck consists of a set of subtr ætive unit operations which removes the unwanted components. The most important of these unit operations include distillation, solvent refining, and dewaxing, which basically are physical separation processes in the sense that if all the separated fractions were recombined one would reconstitute the crude oil.

~71~

A refined lubricant stock may be used as such as a lubricant, or it may be blended with another refined lubricant stock having somewhat different properties. Or the refined lubricant stock, prior to use as a lubricant~ may be compoun~ed with one or more additives which function, for example, as antioxidants, extreme pressure additives, and V.I. improvers. As used herein, the term "stock", regardless whether or not the term is further qualified~ will refer only to a hydrocarton oil without additives. The term '~raw stock"
will be used herein to refer to a viscous distillate fraction of crude petroleum oil isolated by vacuum distillation of a reduced crude from atmospheric distillation, and before further processing, or its equivalent. The term "raffinate~ will refer to an oil that has been solvent refined, for example with furfural. The term "dewaxed stock"
or "dewaxed raffinate" will refer to an oil which has been treated by 1~ any method to remove or otherwise convert the wax contained therein and thereby reduce its pour point. The term "waxy", as used herein will refer to an oil of sufficient wax content to result in a pour point greater than 1C (~30F). The term "stock", when unqualified, will be used herein generically to refer to the viscous fraction in any stage of refining9 but in all cases free of additives.
Briefly, for the preparation of a high grade distillate lubricating oil stock, the current practice is to vacuum distill an atmospheric tower residuum from an appropriate crude oil as the first step. This step provides one or more raw stocks within the boiling range of from 232C to 566C (450 to 1050F). After preparation of a raw stock of suitable boiling range, it is extracted with a solvent~
e.g., furfural, phenol, or chlorex, which is selective for aromatic hydrocarbons, and which removes undesirable components. The raffinate from solvent refining is then dewaxed, for example, by admixing with a solvent such as a blend of methyl ethyl ketone and toluene. The mixture is chilled to induce crystallization of the paraffin waxes which are then separated from the dewaxed dissolved raffinate in quantity sufficient to provide the desired pour point for the subsequently recovered raffinate.

Other processes such as hydrofinishing or clay percola~ion may be used if needed to reduce the nitrogen and sulfur content or improve the color of the lubricating oil stock, and to improve oxidation resistance.
Viscosity index (V.I.) is a quality parameter of considerable importance for distillate lubricating oils to be used in automotive engines and aircraft engines which are subject ~ wide variations in temperature. This Index is a series of numbers ranging from O to 100 ~hich indicate the rate of change of viscosity with te~perature. A
viscosity index of 100 indicates an oil that does not tend to become viscous at low temperature or become thin at high temperatures.
Measurement of the Saybolt Universal Viscosity of an oil at 30C and 99C (100 and 210F), and referral to correlations, provides a measure of the V.I. of the oil. For purposes of the present invention, whenever V.I. is referred to, it is meant the V.I. as noted in the Viscosity Index tabulation of the ASTM (D567), published by ASTM, 191~ Race Street, Philadelphia 3, Pa., or equivalent.
To prepare high V.I. automotive and aircraft oils, the ref`iner usually selects a crude oil relatively rich in paraffinic hydrocarbons since experience has shown that crudes poor in paraffins such as those commonly termed "naphthene-base" crudes yield little or no refined stock having a V.I. above about 40. (See Nelson, supra, pages 80-81 for classifications of crude oils). Suitable stccks ~or high V.I. oils, however, also contain substantial quantities of waxes which result in solvent-refined lubricating oil stocks of high pour point, i.e~, a pour point substantially greater than -1C (+30F).
Thus7 in general, the refining of crude oil to prepare acceptable high V.I. distillate stocks ordinarily includes dewaxing to reduce the pour point to not greater than -1C (+30F~. The refiner, in this step, often produces saleable paraffin wax by-product7 thus in part defraying the high cost of the dewaxing stsp.
Raw distillate lubricating oil stocks usually do not have a particularly high V.I. However7 solvent~refining, as with furfural for example, in addition to removing unstable and sludge-forming components from the crude distillate, also removes co~oonents which 7~

adversely affect the V.I. Thus, a solvent refined stock prior to dewaxing usually has a V.I. ~ll in excess of specifications.
Dewaxing, on the other hand, removes paraffins which have a \/.I. of about 2007 and thus reduces the V.I. of the dewaxed stock.
In recent years, cataly-tic techniques ha~e become available for dewaxing of petroleum stocks. A process of that nature developed by British Petroleum is described in The Oil and Gas Journal dated Jan. 6, 1975~ pages 69-73. See also U.S. Patent No. 3,668,113.
In U. S. Patent Reissue No. 28,398 (of U.S. Patent No.
3,700,585) is described a process for catalytic dewaxing with a catalyst comprising zeolite ZSM-5. Such processes combined with catalytic hydrofinishing are described in U.S. Patent No. 3,894,938.
In U. S. Patent No. 3,755,13~ is described a process for mild solvent dewaxing to remove high quality wax from a lube stock, which is then catalytically dewaxed to specification pour point.
Tt is interesting to note that catalytic dewaxing, unlike prior art dewaxing processes, although subtractive, is not a physical process but rather depends on transforming the straight chain and other waxy paraffins to non-wax materials. The process, however, is more economical and thùs of industrial interest, even though at least some loss of saleable wax is inherent. Commercial interest in catalytic dewaxing is evidence of the need for more efficient refinery processes to produce low pour point lubricants.
Poor resistance to oxidation, which forms corrosive products, sludge, or both, is highly undesirable in a quality lubricant. In general, improved resistance to oxidation is imparted by hydrotreating the lube base stock to the point at which it passes an industry accepted oxidation resistance test.
It has been observed in some instances that catalytic dewaxing in the presence of hydrogen gas with a catalyst such as ZSM-5 tends to produce lube base stock oils with increased bromine number and degraded resistance to oxidation when the dewaxing is conducted at a temperature higher than about 357C to 371C (675F to 700F) and under moderate pressure, such as less than 6996 kPa (lOOO psig). This deficiency becomes difficult to correct by ordinary mild hydrotreating. Because of this effect, it is preferred to dewax lube base stock oils at as low a temperature as is practical with the temperature not to exceed 371C (700F), and most preferably not to exceed 357C (675F). TbUS, the particular conditions sbown in Table IX are preferred for dewaxing lube base stock oils, and at least in some cases, become mandatory if very good resistance to oxidation is to be achieved.
TABLE IXo _DE~AXING S~ AS~STOCKS

Most Preferred Preferred Temperature LHSV, hr O.3~20 0.5-10 Pressure psig 0-3000 25-1500 kPa 101-20786 274-10443 : 20 Temperature LHSV, hr 1 0.1-10 0.5-40 H2/HC mol ratio 1-20 2-10 Pressure psig - O 3000 200-2000 kPa 101-20786 274-10443 Certain waxy lube base stock raffinates exhibit an initial equilibrium temperature above 357~C to 371C (675 to 700F) when dewaxed at about 1 LHSV. Dewaxing such sto~ks catalytically to an end~of-run temperature not to exceed 357C to 371C (675 to 700F) requires such frequent regeneration of the catalysts as to become excessively costly. However, by pretreating the raffinate with a sorbent, as described hereinabove, the initial equilibrium temperature is reduced to ~71C (700F) or less, and the dewaxing operation with production of low pour point oil of very good oxidation resistance becomes feasible.
Since, in general, the oxidation resistance of a catalytically dewaxed lube base stock reffinate is improved by reduction of the dewaxing tem~erature, any waxy raffinate that contains a catalytically deleterious impurity will benefit in oxidation stability if pretreated with a sorbent, as described hereinabove, followed by dewaxing at a temperature at least 1~C
(25F) lower than would be required to produce the same pour point reduction without pretreatment and under otherwise the same process conditions.
In order for a lube base stock raffinate to be suitable for the process of this invention, it must contain a contaminant, i.e. a catalytically deleterious impurity, or at least exhibit behavior consistent with such contamination. When it is not known whether or not the rafFinate does contain such contaminant, a relatively simple test which is conducted as follows will resolve the question. About two parts of the raffinate is mixed with one part of dewaxing catalyst at room temperature, or at a higher temperature in the range of from -7C to 100C (20F to 212F) if needed to make the hydrocarbon feed fluid enough for effective mixing and contact with the catalyst~ The mixture is allowed ta stand for about one hour, after which the treated oil is separated from the catalyst. A test is now made comparing the treated feed with the raw feed under practical catalytic dewaxing conditions or a realistic variant thereof, using, of course, fresh ca~alyst. If the initial equilibrium temperature of the raffinate and the pretreated raffinate are substantially the same, then the raffinate may be regarded as substantially free of contaminant and unsuitable for purposes of this invention. If, however, the initial equilibrium temperature of the raffinate is reduced from a temperature above 371C (70ûF) to 357-371C
~675-7û0F) or less, the raffinate is suitable for purposes of this invention. Also, if the initial equilibrium temperature of the un~reated raffinate is below 357C ( 675F) but is red ced by at least 14C (25F) in this pretreatment testy the untreated raffinate is deemed suitable.
The preferred crystalline zeolites are ZSM-5, ZSM-ll, intergrowths of ZSM-5 and ZSM-119 ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48. As is known to those skilled in the art, any of these zeolites may be recognized from its x-ray diffraction pattern which results essentially from its crystal structure, the alumina and cation content of the crystal having but little effect on the pattern. Thus, as illustrated previously, the crystalline zeolite used to refine the feed and that used as catalyst may have the same crystal structure and either the same or a different chemical compositions. Also within the scope of this invention is to refine the feed with a crystalline zeolite having a crystal structure different from that of the zeolite used in the catalyst. The particularly preferred crystalline zeolites are ZSM-5, ZSM 11 and intergrowths thereof.
The term ~contaminant," as used herein, refers to whatever substance beha~/es in a deleterious way in catalytic dewaxing, and the chemical composition of the contaminant need not be ascertained.
Furthermore, the term "contaminant," or the phrase "catalytically deleterious impurity," is intended to include deleterious organic substances which occur in natural association with the hydrocarbon oil or its precursor, such as a crude petroleum, as well as materials which may be formed during processing of the oil. The term also include, of course, contaminants of well defined and known chemical structure such as furfural, sulfolane and the like which are used for extraction or separation of fractions.
Certain aspects of the present invention will now be illustrated by reference to examples which are not to be construed as limiting the scope of this invention, which scope is determined by this entire specification including the claims thereof.
EXPMPLES

A Nigerian gas oil having a nominal boiling range of 329C to 413~ (625-775F) was taken as one example of a contaminated feed.
The raw gas oil had the properties shown in Table III.

API 29.2 Pour Point, C(F) 24(75) ~t % S (Sul~ur) 0.18 Wt % N (Nitrogen) 0.03 ppm Basic N 262 Portions of the raw gas oil were mixed with varying amounts of crystall;ne zeolite ZSM-5 that had been incorporated in a matrix and extruded to form 1/16 inch extrudate that contained about 65 wt.%
zeolite. The particular ZSM-5 used as sorbent was H-ZSM-5 with a SiO /A1203 ratin of 7û:1 and an "alpha" value of 175. The dried, calcined extrudate had the properties shown in Table IV. After the mixtures of oil and extrudate had been allowed to stand overnight at 93C (20ûF)~ the oil was decanted and analyzed with the results shown in Table VO

T~bl IV Z5~ 5 E~ t Oensity, GM/CC
` Packed .59 Particle .89 Real 2.66 Sur~ace Area, M2/GM 365.

Pore Vol., CC/GM .748 .~
Ave. Pore Dia., A 92.

~YL
Extrudate/Oil (WtJWt) PPM Basic N Wt % N Wt % S
0 262 .0340 0.18 .034 235 .0300 0.17 .068 192 .0260 0.16 .136 166 .023~ 0.14 F-07a7 -26-Examole 1 illustrates the method of this invention for refining a waxy hydrocarbon oil feed. rhe permitted contact time was dictated by convenience, it being indicated by other experiments that equivalent results would be obtained with about one hour contact.

A ZSM-5 extrudate was placed in a fixed-bed catalytic reactor.
The particular ZSM-5 used as catalyst had been activated by calcination, and had a silica to alumina ratio of about 160, an "alpha" activity of 114, and contained 0.54 wt.% nickel and about 0.02 wt.% sodium. The raw gas oil having the properties shown in Table III
and hydrogen were passed over the catalyst under dewaxing conditions, in this instance at 2859 kPa (400 psig), 1 LHSV with a hydrogen circulation rate of 445 Nl/1 (2500 SCF/Bbl). The temperature was adjusted periodically to give a 166C+ (330F+) product having a pour point of about ~18C (0F). The temperature required for the first seventeen days of operation are given in Table VI.
Table VI

C F

Example 2 illustrates a typical prior art dewaxing run. It will be noted that a relatively rapid increase in temperature is required for about the first eleven days to maintain product quality, a~ter which a relatively steady te~perature may be maintained, in this instance at about 399C (750F). The temperature at which this steady operation sets in is re~erred to herein as the "initial equilibrium temperature." It will be recognized that this temperature may slowly 3s increase with catalyst age until some prescribed limit is reached, ~ 7~?7 necessitating regeneration of the catalyst. In any case, the initial equilibrium temperature is determined predominantly by the nature of the feed, all else beiny equal. The equilibrium tem~oerature observed af`ter the initial equilibrium temperature is equal to it or higher in normal, steady operation.
EXoMPLE 3 -, A batch of refined Nigerian gas oil was prepared from the raw gas oil described in Table III by the method deæribed in Example 1 except that a sorbent to oil weight ratio of 0.071 was used and the oil was treated for 16 hours at 93C (200F). The refined oil had 215 ppm basic nitrogen.
The prior art catalytic dewaxing run described in Example 2 was terminated at 17 days by switching from the raw gas oil feed to the above-described refined feed, without changing the catalyst.
The temperature required to maintain a 18C (0F) pour point, 166C+ (330F~) product was observed to decrease over the next ~our days to 346C (655F), with an indication that a new initial equilibrium temperature would set in at about 343C (650F) or lower.
This example illustrates one embodiment of the dewaxing process of the present invention wherein a refined feed, although still containing a substantial amount of basic nitrogen, is dew~xed at an equilibrium temperature substantially below that required for the raw feed.

This example is provided to show the effect of pretreatment of the raw gas oil with a clay sorbent compared with refining according to the present invention. A commercial clay sorbent known as "Attagel 40" was prepared as extrudate with the properties shown in Table VII.

Table VII

Density, GM/CC
Packed .47 Particle .82 Real 2.55 Surface Area, M2/G~ 139.

Pore Vol., CC/GM .828 Ave~ Pore Dia., A 238.

A portion of the raw gas oil described in Table III was treated in the same manner as described in Example 3 exoept that the clay sorbent was substituted for the crystalline zeolite sorbent. The treated oil was found to have a basic nitrogen content of 230 ppm.

The catalytic dewaxing run described in Example 3 was terminated after the catalyst had been on stream for a total of 21 days, by switching from the refined gas oil feed to the pretreated feed of Example 4, without changing the catalyst.
The temperature required to maintain -18C (0F) pour point, 166C+ (330~F~) product was observed to increase from about 352~C
(665F)to about 40~C (755F) over four days o~ operation, at which point the run was terminated.
Example 5 illustrates that removal of basic nitrogen does not necessarily provide a feed which is more readily dewaxed. Thus, for purposes of the present invention, the terms "refine" and "refined,"
as used herein, refer to treatment with a crystalline zeolite sorbent as described herein and to a product that evidences a demonstrable catalytic advantage, such as a reduced initial equilibrium temperature, an increased rate of conversion, or the like.
., , '7 This examples illustrates the process of this invention applied to a hydrotreated Occidental Shale Oil. The raw feed had the properties shown in Table VIII.
Table VIII. Properties of Hydrotreated Shale Oil API 36.1 Basic N, ppm 340 Pour Point C(F) 13(55) B.P. C F
IBP/5% 67/146 153/295 20/5o% 227/305 441/581 70/95% 366/485 690/905 E.P. 553 1027 The oil was refined by contacting 5 parts by weight of oil with 1 part by weight of ZSM-5 extrudate as sorbent. The ZSM-5 content of the extrudate was about 65 wt~%, -the balance being an alumina matrix, and the ZSM-5 had a SiO2/A120~ ratio of 70. The refined oil contained less than 5 ppm of basic nitrogen.
Both the untreated oil and the oil refined as described were dewaxed at -18C (ûF~ pour point for the 193C+ (380 F+) fraction and the initial equilibrium temperature was determined in each case. The dewaxing conditions were the same as those described in Example 2, and the catalyst was similar to that used in the Example except that it had a slightly lower "alpha" value of 101.
The initial equilibrium temperature determined for the raw oil was 413C (775F). The refined oil treated under the same conditions gave an initial equilibrium temperature oF 343C (650F)9 i.e., 70C (125F) lower than for the raw oil.

~ - 30 -. . .

Examele 7 A comparison was made to determine the effect on aging of the lube dewaxing catalyst using both treated and untreated charge stock.
A charge stock (having the characteristics set out in Table IX
below) was treated over steamed Ni-~SM-5 (having the properties set out in Table X below) at 2859 kPa (400 psig), 218C (425F) and 16 volurnes oil/volume adsorbent to obtain a product having 62 ppm nitrogen.
The thus-treated nitrogen reduced stock was subjected to dewaxing using a fresh sample of the same zeolite preparation at 218C
(425F), 2859 kPa (400 psig), one volume oil/volume catalyst/hour and 445 Nl hydrogen/l charge (2500 scf hydrogen/bbl charge. Untreated stock was also subjected to dewaxing using the same conditions and a fresh sample of the same catalyst.
In the following Figure 2, the graph on the left shows the correlation between temperature and days on stream using the untreated stock having lO0 ppm nitrogen. -The graph on the right shows the same correlation using the treated stock having 62 ppm nitrogen. As shown in Figure 2, treating reduced the aging rate of the lube dewaxing catalyst from from 6.9C (12.4F)/day for untreated oil to 3.9C (7F)/day for the treated oil.

Table IX

Characteristics of Furfural Extracted Lube Stock .

API 27.8 Basic N~ ppm lO0 Pour Point C(F) 49(120) B.P. C F
IBP/5% 391/443 735/830 20/50% 464/481 867/897 70/95% 494/529 922/985 .
:, .

7~2'~

Table X

Proeerties of Ni-ZSM-5B

Ni, wt.% 1.2 SiO2/A1203 70 Ni-zs~5B/Al2/o3 65/35 Packed Density, g/cc 0.59 Surface Area, m /g 348 Alpha Activity 68 - ;,. . ~ . -'~'' .:', . --...... :, ., :

Claims (8)

WHAT IS CLAIMED IS:
1. A process for preparing a high quality lube base stock oil having a predetermined pour point in the range of from -32°C to -1°C (-25° to +30°F) from waxy crude oil by extracting a distillate fraction that boils within the range of 232°C to 593°C (450° to 1100°F) or a deasphalted vacuum residuum fraction of the waxy crude with a solvent selective for aromatic hydrocarbons to yield a raffinate from which undesirable compounds have been removed, contacting the raffinate and hydrogen gas with a dewaxing catalyst under dewaxing conditions effective to impart the predetermined pour point, the catalyst comprising a first crystalline zeolite having a dry crystal framework density of not less than about 1.6 grams per cubic centimeter and a constraint index of from 1 to 12, thereby converting wax contained in the raffinate to lower boiling hydrocarbons and, topping the dewaxed raffinate to remove therefrom components of a low molecular weight, characterized by pretreating the raffinate, prior to dewaxing, with a sorbent comprising a second crystalline zeolite having an effective pore diameter equal to or larger than the first crystalline zeolite under a combination of conditions selected from a temperature of from 2°C to 177°C (35° to about 350°F), a pressure of 101 to 20786 kPa (0 to 3000 psig), and a contact time equivalent to a LHSV of 0.1 to 100 hr.-1, the combination being effective to provide a pretreated raffinate characterized by an initial equilibrium temperature not exceeding about 357°C to 371°C (675° to 700°F) and at least 14°C (25°F) lower than that obtained with the raffinate without pretreatment when dewaxed at about 1 LHSV and dewaxing the raffinate at a temperature not to exceed the lesser of the equilibrium temperature of the raffinate without pretreatment minus 14°C (25°F), or 371°C (700°F).
2. The process of Claim 1 wherein the first crystalline zeolite is ZSM-5, ZSM-11, intergrowths of ZSM-5 and ZSM-11, ZSM-12, ZSM-23, ZSM-38 or ZSM-48.
3. The process of Claim 1 wherein the first and the second crystalline zeolite are each individually selected from ZSM-5, ZSM-11, intergrowths of ZSM-5 and ZSM-11, ZSM-12, ZSM-23, ZSM-38 and ZSM-48.
4. The process of Claim 3 wherein the first and the second crystalline zeolite have the same crystal structure.
5. The process of Claim 3 or 4 wherein the first and the second zeolite have the same crystal structure and the same chemical compositions.
6. The process of Claim 2, 3 or 4 wherein the crystalline zeolites are selected from ZSM-5, ZSM-11 and intergrowths thereof.
7. The process of Claim 2 wherein the second crystalline zeolite is hydrogen mordenite.
8. The process of Claim 7 wherein the first crystalline zeolite is of ZSM-5, ZSM-11 or intergrowths thereof.
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US4357232A (en) 1982-11-02
DE3267722D1 (en) 1986-01-16
JPS57139183A (en) 1982-08-27
EP0057980B1 (en) 1985-12-04
AU7956182A (en) 1982-07-22
AU547537B2 (en) 1985-10-24
EP0057980A1 (en) 1982-08-18
JPH023839B2 (en) 1990-01-25

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