Process for selective wax hydrocracking

A process for hydrocracking heavy hydrocarbon feeds using a catalyst composition containing a hydrogenation/dehydrogenation component, such as a noble metal, and an acidic solid component including a Group IVB metal oxide modified with an oxyanion of a Group VIB metal. The hydrocracking product has high isoparaffin to normal paraffin ratios and with minimal ethane and methane byproducts at high conversions. The hydrocracking step is useful in processes for producing high quality lubricating oil basestocks, along with naphtha and distillate products.

FIELD OF THE INVENTION
 This invention relates to a process for the hydrocracking of hydrocarbon
 feedstocks to produce primarily fuels using a catalyst comprising a
 hydrogenation/dehydrogenation component, such as a noble metal, and an
 acidic solid component comprising a Group IVB metal oxide modified with an
 oxyanion of a Group VIB metal. The invention further relates to a process
 for co-producing high quality lubricants via hydrocracking wax-containing
 feeds.
 BACKGROUND OF THE INVENTION
 Hydrocracking is a process which has achieved widespread use in petroleum
 refining for converting various petroleum fractions to lighter and more
 valuable products, especially distillates such as jet fuels, diesel oils
 and heating oils. Hydrocracking is generally carried out in conjunction
 with an initial hydrotreating step in which the heteroatom-containing
 impurities in the feed are hydrogenated without a significant degree of
 bulk conversion. During this initial step, the heteroatoms, principally
 nitrogen and sulfur, are converted to inorganic form (ammonia,
 hydrogen-sulfide) and these gases may be removed prior to the subsequent
 hydrocracking step although the two stages may be combined in cascade
 without interstage separation as, for example, in the Unicracking-JHC
 process and in the moderate pressure hydrocracking process described in
 U.S. Pat. No. 4,435,275.
 In the second stage of the operation, the hydrotreated feedstock is
 contacted with a bifunctional catalyst which possesses both acidic and
 hydrogenation/dehydrogenation functionality. In this step, the
 characteristic hydrocracking reactions occur in the presence of the
 catalyst. Polycyclic aromatics in the feed are hydrogenated, and ring
 opening of aromatic and naphthenic rings takes place together with
 dealkylation. Further hydrogenation may take place upon opening of the
 aromatic rings. Depending upon the severity of the reaction conditions,
 the polycyclic aromatics in the feed will be hydrocracked to paraffinic
 materials or, under less severe conditions, to monocylic aromatics as well
 as paraffins. Naphthenic and aromatic rings may be present in the product,
 for example, as substituted naphthenes and substituted polycyclic
 aromatics in the higher boiling products, depending upon the degree of
 operational severity.
 The bifunctional catalyst used in the hydrocracking process typically
 comprises a metal component which provides the
 hydrogenation/dehydrogenation functionality and a porous, inorganic oxide
 support provides the acidic function. The metal component typically
 comprises a combination of metals from Groups IVA, VIA and VIIIA of the
 Periodic Table (IU Table) although single metals may also be
 encountered. Combinations of metals from Groups VIA and VIIIA are
 especially preferred, such as nickel-molybdenum, cobalt-molybdenum,
 nickel-tungsten, cobalt-nickel- molybdenum and nickel-tungsten-titanium.
 Noble metals of Group VIIIA especially platinum or palladium may be
 encountered but are not typically used for treating high boiling feeds
 which tend to contain significant quantities of heteroatoms which function
 as poisons for these metals.
 The porous support which provides the acidic functionality in the catalyst
 may comprise either an amorphous or a crystalline material or both.
 Amorphous materials have significant advantages for processing very high
 boiling feeds which contain significant quantities of bulky polycyclic
 materials (aromatics as well as polynapthenes) since the amorphous
 materials usually possesses pores extending over a wide range of sizes and
 the larger pores, frequently in the size range of 100 to 400 Angstroms
 (.ANG.) are large enough to provide entry of the bulky components of the
 feed into the interior structure of the material where the acid-catalyzed
 reactions may take place. Typical amorphous materials of this kind include
 alumina and silica-alumina and mixtures of the two, possibly modified with
 other inorganic oxides such as silica, magnesia or titania.
 Zeolitic crystalline materials, especially the large pore size zeolites
 such as zeolites X and Y, have been found to be useful for a number of
 hydrocracking applications since they have the advantage, as compared to
 the non-zeolitic materials, of possessing a greater degree of activity,
 which enables the hydrocracking to be carried out at lower temperatures at
 which the accompanying hydrogenation reactions are thermodynamically
 favored. In addition, the zeolitic crystalline catalysts tend to be more
 stable in operation than the non-zeolitic materials such as alumina. The
 zeolitic crystalline materials may, however, not be suitable for all
 applications since even the largest pore sizes in these materials,
 typically about 7.4 .ANG. in the X and Y zeolites, are too small to permit
 access by various bulky species in the feed. For this reason,
 hydrocracking of residuals fractions and high boiling feeds has generally
 required a non-zeolitic catalyst of rather lower activity. Although it
 would be desirable, if possible, to integrate the advantages of the
 non-zeolitic and the zeolitic crystalline material in hydrocracking
 catalysts and although the possibility of using active supports for
 zeolitic crystalline materials has been proposed, the difference in
 activity and selectivity between the non-zeolitic and zeolitic crystalline
 materials has not favored the utilization of such catalysts.
 The crystalline hydrocracking catalysts based on zeolites such as zeolites
 X and Y generally tend to produce significant quantities of gasoline
 boiling range materials (approximately 330.degree. F.-, 165.degree. C.-)
 materials as product. Since hydrocracked gasolines tend to be of
 relatively low octane and require further treatment as by reforming before
 the product can be blended into the refinery gasoline pool, hydrocracking
 is usually not an attractive route for the production of gasoline. On the
 other hand, it is favorable to the production of distillate fractions,
 especially jet fuels, heating oils and diesel fuels since the
 hydrocracking process reduces the heteroatom impurities characteristically
 present in these fractions to the low level desirable for these products.
 The selectivity of crystalline aluminosilicate catalysts for distillate
 production may be improved by the use of highly siliceous zeolites, for
 example, the zeolites possessing a silica: alumina ratio of 50:1 or more,
 as described in U.S. Pat. No. 4,820,402 (Partridge et al), but even with
 this advance in the technology, it would still be desirable to integrate
 the characteristics of the amorphous materials with their large pore sizes
 capable of accommodating the bulky components of typical hydrocracking
 feeds, with the activity of the zeolite catalysts.
 While the considerations set out above apply mostly to fuels hydrocracking
 processes, they will also be relevant in greater or lesser measure to lube
 hydrocracking. In the lube hydrocracking process, which is well
 established in the petroleum refining industry, an initial hydrocracking
 step is carried out under high pressure in the presence of a bifunctional
 catalyst which effects partial saturation and ring opening of the aromatic
 components which are present in the feed. The hydrocracked product is then
 subjected to dewaxing in order to reach the target pour point since the
 products from the initial hydrocracking step which are paraffinic in
 character include components with a relatively high pour point which need
 to be removed in the dewaxing step.
 In theory, as well as in practice, lubricants should be highly paraffinic
 in nature since paraffins possess the desirable combination of low
 viscosity and high viscosity index. Normal paraffins and slightly branched
 paraffins e.g. n-methyl paraffins, are waxy materials which confer an
 unacceptably high pour point on the lube stock and are therefore removed
 during the dewaxing operations in the conventional refining process
 described above. It is, however, possible to process waxy feeds in order
 to retain many of the benefits of their paraffinic character while
 overcoming the undesirable pour point characteristic. A severe
 hydrotreating process for manufacturing lube oils of high viscosity index
 is disclosed in Developments in Lubrication PD 19(2), 221-228, S. Bull et
 al, and in this process, waxy feeds such as waxy distillates, deasphalted
 oils and slack waxes are subjected to a two-stage hydroprocessing
 operation in which an initial hydrotreating unit processes the feeds in
 blocked operation with the first stage operating under higher temperature
 conditions to effect selective removal of the undesirable aromatic
 compounds by hydrocracking and hydrogenation. The second stage operates
 under relatively milder conditions of reduced temperature at which
 hydrogenation predominates, to adjust the total aromatic content and
 influence the distribution of aromatic types in the final product. The
 viscosity and flash point of the base oil are then controlled by topping
 in a subsequent redistillation step after which the pour point of the
 final base oil is controlled by dewaxing in a solvent dewaxing
 (MEK-toluene) unit. The slack waxes removed from the dewaxer may be
 reprocessed to produce a base oil of high viscosity index. Processes of
 this type, employing a waxy feed which is subjected to hydrocracking over
 an amorphous bifunctional catalyst such as nickel-tungsten on alumina or
 silica-alumina are disclosed, for example, in British Patents Nos.
 1,429,494, 1,429,291 and 1,493,620 and U.S. Pat. Nos. 3,830,273,
 3,776,839, 3,794,580, and 3,682,813.
 In lube processes of this kind, the catalyst is, like the fuels
 hydrocracking catalyst, typically a bifunctional catalyst containing a
 metal hydrogenation component on an amorphous acidic support. The metal
 component is usually a combination of base metals, with one metal selected
 from the iron group (Group VIIIA) and one metal from Group VIA of the
 Periodic Table, for example, nickel in combination with molybdenum or
 tungsten. The activity of the catalyst may be increased by the use of
 fluorine, either by incorporation into the catalyst during its preparation
 in the form of a suitable fluorine compound or by in situ fluoriding
 during the operation of the process, as disclosed in GB 1,390,359.
 Although the lube hydrocracking processes using an amorphous catalyst for
 the treatment of the waxy feeds has shown itself to be capable of
 producing high V.I. lubricants, it is not without its limitations. The
 major process objective in lube hydrocracking (LHDC) is to saturate the
 aromatic components in the feed to produce saturated cyclic compounds
 (naphthenes) or, by ring opening of the naphthenes, paraffinic materials
 of improved lubricating properties. This requires the hydrogenation
 activity of the catalyst to be high. There is no corresponding requirement
 for a high level of cracking activity since no major change in boiling
 range is required or even desirable: the amount of material in the lube
 boiling range, typically 650.degree. F.+, should be maintained at the
 maximum level consistent with the degree of ring opening required to
 furnish a lube product of the desired quality. This combination of
 requirements has typically led to the use of LHDC catalysts with high
 metals loadings, particularly for base metal combinations with Group VIA
 metals such as tungsten: commercial LHDC catalysts currently available
 have typical nickel loadings of about 5 percent but the tungsten loading
 may be in the range of 10 to 25 percent.
 We have now found that a solid acid catalyst comprising a Group IVB metal
 oxide modified with an oxyanion of a Group VIB metal may be used as the
 basis for hydrocracking catalysts. It is an object of the present
 invention to provide a hydrocracking process using a high activity
 catalyst. It is a further object of the present invention to provide a
 hydrocracking process using such a catalyst with products having high
 isoparaffin/normal paraffin ratios and a low C.sub.1 -C.sub.2 yield.
 SUMMARY OF THE INVENTION
 There is described herein a catalytic process for hydrocracking hydrocarbon
 feedstocks generally having an initial boiling point above about
 390.degree. F. Catalysts comprising a Group IVB metal oxide modified with
 an oxyanion of a Group VIB metal have been found to be selective for
 hydrocracking of waxy feeds with products having high isoparaffin/normal
 paraffin ratios and with minimal C.sub.1 -C.sub.2 byproducts at high
 conversions. The catalyst of the present invention shows good potential
 for high selectivity hydrocracking of waxy feeds with small amounts of
 light gas.
 The invention therefore includes a process for hydrocracking a hydrocarbon
 feedstock having an initial boiling point above about 390.degree. F.
 comprising hydrocracking the hydrocarbon feedstock in the presence of
 hydrogen at a pressure of at least about 500 psig in the presence of a
 catalyst composition comprising a hydrogenation/dehydrogenation component
 and an acidic solid component comprising a Group IVB metal oxide modified
 with an oxyanion of a Group VIB metal, which results in a conversion to
 650.degree. F.- products of at least about 10%.
 The invention further includes a process for co-producing a lubricating oil
 base stock which comprises:
 (a) hydrocracking a hydrocarbon feedstock in the presence of hydrogen at a
 pressure of at least about 500 psig in the presence of a catalyst
 composition comprising a hydrogenation/dehydrogenation component and an
 acidic solid component comprising a Group IVB metal oxide modified with an
 oxyanion of a Group VIB metal; and
 (b) processing the hydrocracked product to provide a lubricating oil base
 stock.
 Conducting the hydrocracking step in the presence of a catalyst containing
 a noble metal and an acidic solid component comprising a Group IVB metal
 oxide modified with an oxyanion of a Group VIB metal results in a
 hydrocracking product having a high isoparaffin/normal paraffin ratio of
 generally at least about 2.0 and preferably at least about 3.0. C.sub.1
 and C.sub.2 byproducts are also minimized with generally less than about
 0.5% and preferably less than about 0.2% C.sub.1 and C.sub.2 formed. High
 conversion, generally about 80 to about 100%, to 650.degree. F.- products
 can be achieved, if desired, through the process of the present invention.
 DETAILED DESCRIPTION OF THE INVENTION
 Feedstocks
 The hydrocarbon feed materials suitable for use in the hydrocracking step
 of the present invention include crude petroleum, reduced crudes, vacuum
 tower residua, vacuum gas oils, deasphalted residua and other heavy oils.
 These feedstocks contain a substantial amount of components boiling above
 about 260.degree. C. (about 500.degree. F.) and normally have an initial
 boiling point of about 290.degree. C. (about 550.degree. F.) and more
 usually about 340.degree. C. (about 650.degree. F.). Typical boiling
 ranges will be from about 340.degree. C. to 565.degree. C. (from about
 650.degree. F. to about 1050.degree. F.) or from about 340.degree. C. to
 about 510.degree. C. (from about 650.degree. F. to about 950.degree. F.)
 but oils with a narrower boiling range can, of course, also be processed,
 for example, those with a boiling range of from about 340.degree. C. to
 about 455.degree. C. (from about 650.degree. F. to about 850.degree. F.).
 Heavy gas oils are often of this kind as are heavy cycle oils and other
 non-residual materials. Oils obtained from coal, shale or tar sands can
 also be treated in this way. It is possible to process or co-process
 materials boiling below about 260.degree. C. (about 500.degree. F.).
 Feedstocks containing lighter ends of this kind will normally have an
 initial boiling point above about 200.degree. C. (about 390.degree. F.).
 Thus, light cycle oils are also suitable for use in the hydrocracking step
 of the present invention.
 When a high quality lube base stock co-product is desired, the selected
 feedstock will contain a significant amount of waxy components, e.g., at
 least about 20 weight percent, and preferably at least about 50 weight
 percent, paraffins. Petroleum waxes, that is, waxes of paraffinic
 character are derived from the refining of petroleum and other liquids by
 physical separation from a wax-containing refinery stream, usually by
 chilling the stream to a temperature at which the wax separates, usually
 by solvent dewaxing, e.g., MEK/toluene dewaxing or by means of an
 autorefrigerant process such as propane dewaxing. These waxes have high
 initial boiling points above about 650.degree. F. (about 345.degree. C.)
 which render them extremely useful for processing into lubricants which
 also require an initial boiling point of at least 650.degree. F. (about
 345.degree. C.). The presence of lower boiling components is not to be
 excluded since they will be removed together with products of similar
 boiling range produced during the processing during the separation steps
 which follow the characteristic processing steps. Since these components
 will, however, load up the process units they are preferably excluded by
 suitable choice of feed cut point. The end point of wax feeds derived from
 the solvent dewaxing of neutral oils, i.e. distillate fractions produced
 by the vacuum distillation of long or atmospheric resids will usually be
 not more than about 1100.degree. F. (about 595.degree. C.) so that they
 may normally be classified as distillate rather than residual streams but
 high boiling wax feeds such as petrolatum waxes i.e. the waxes separated
 from bright stock dewaxing, which may typically have an end point of up to
 about 1300.degree. F. (about 705.degree. F.), may also be employed.
 Feeds also include slack waxes, that is, the waxy product obtained directly
 from a solvent dewaxing process, e.g. an MEK or propane dewaxing process.
 The slack wax, which is a solid to semi-solid product, comprising mostly
 highly waxy paraffins (mostly n- and mono-methyl paraffins) together with
 occluded oil. The suitable feeds, as defined above, will have
 .gtoreq..about.95% of their composition boiling point above that of
 naphtha boiling range materials, e.g., above about 200.degree. C. (about
 390.degree. F.) and more generally the boiling point will be above about
 300.degree. C. (about 570.degree. F.).
 The hydrocarbon feedstock can be treated prior to hydrocracking in order to
 reduce or substantially eliminate its heteroatom content. As necessary or
 desired, the feedstock can be hydrotreated under mild or moderate
 hydroprocessing conditions to reduce its sulfur, nitrogen, oxygen and
 metal content. Generally, a hydrocarbon feedstock used in hydrocracking
 should have a low metals content, e.g., less than about 200 ppm, in order
 to avoid obstruction of the catalyst and plugging of the catalyst bed. The
 mild to moderate hydrotreating conditions employed include pressures of
 from about 2 to about 21 MPa and H.sub.2 consumptions of from about 20 to
 about 280 m.sup.3 /m.sup.3. Conventional hydrotreating process conditions
 and catalysts can be employed, e.g., those described in U.S. Pat. No.
 4,283,272, the contents of which are incorporated by reference herein.
 Catalyst
 The catalyst used in the process of the present invention comprises an
 oxide of a Group IVB metal, preferably zirconia or titania. This Group IVB
 metal oxide is modified in two ways. According to one modification, the
 Group IVB metal oxide is modified with an oxyanion of a Group VIB metal,
 such as an oxyanion of tungsten, such as tungstate. The modification of
 the Group IVB metal oxide with the oxyanion of the Group VIB metal imparts
 acid functionality to the material. The modification of a Group IVB metal
 oxide, particularly, zirconia, with a Group VIB metal oxyanion,
 particularly tungstate, is described in U.S. Pat. No. 5,113,034; in
 Japanese Kokai Patent Application No. Hei 1 [1989]-288339; and in an
 article by K. Arata and M. Hino in Proceedings 9th International Congress
 on Catalysis, 4, 1727-1735 (1988), the entire disclosures of these
 publications are expressly incorporated herein by reference.
 According to another modification of the Group IVB metal oxide described
 herein, a hydrogenation/dehydrogenation component is combined with the
 Group IV metal oxide. This hydrogenation/dehydrogenation component imparts
 the ability of the material to catalyze the addition of hydrogen to or the
 removal of hydrogen from organic compounds, such as hydrocarbons,
 optionally substituted with one or more heteroatoms, such as oxygen,
 nitrogen, metals or sulfur, when the organic compounds are contacted with
 the modified material under sufficient hydrogenation or dehydrogenation
 conditions.
 Examples of hydrogenation/dehydrogenation components include the oxide,
 hydroxide or free metal (i.e., zero valent) forms of Group VIII metals
 (i.e., Pt, Pd, Ir, Rh, Os, Ru, Ni, Co and Fe), Group IVA metals (i.e., Sn
 and Pb), Group VB metals (i.e., Sb and Bi) and Group VIIB metals (i.e.,
 Mn, Tc and Re). The present catalyst comprises one or more catalytic forms
 of one or more noble metals (i.e., Pt, Pd, Ir, Rh, Os or Ru). Combinations
 of catalytic forms of such noble or non-noble metals, such as combinations
 of Pt with Sn, may be used. The valence state of the metal of the
 hydrogenation/dehydrogenation component is preferably in a reduced valance
 state, e.g., when this component is in the form of an oxide or hydroxide.
 The reduced valence state of this metal may be attained, in situ, during
 the course of a reaction, when a reducing agent, such as hydrogen, is
 included in the feed to the reaction.
 For the purposes of the present disclosure, the expression, Group IVB metal
 oxide modified with an oxyanion of a Group VIB metal, is intended to
 connote a material comprising, by elemental analysis, a Group IVB metal, a
 Group VIB metal and oxygen, with more acidity than a simple mixture of
 separately formed Group IVB metal oxide mixed with a separately formed
 Group VIB metal oxide or oxyanion. The present Group IVB metal, e.g.,
 zirconium, oxide modified with an oxyanion of a Group VIB metal, e.g.,
 tungsten, is believed to result from an actual chemical interaction
 between a source of a Group IVB metal oxide and a source of a Group VIB
 metal oxide or oxyanion.
 This chemical interaction is discussed in the aforementioned article by K.
 Arata and M. Hino in Proceedings 9th International Congress on Catalysis,
 4, 1727-1735 (1988). In this article, it is suggested that solid
 superacids are formed when sulfates are reacted with hydroxides or oxides
 of certain metals, e.g., Zr. These superacids are said to have the
 structure of a bidentate sulfate ion coordinated to the metal, e.g., Zr.
 In this article, it is further suggested that a superacid can also be
 formed when tungstates are reacted with hydroxides or oxides of Zr. The
 resulting tungstate modified zirconia materials are theorized to have an
 analogous structure to the aforementioned superacids comprising sulfate
 and zirconium, wherein tungsten atoms replace sulfur atoms in the
 bidentate structure.
 Although it is believed that the present catalysts may comprise the
 bidentate structure suggested in the aforementioned article by Arata and
 Hino, the particular structure of the catalytically active site in the
 present Group IVB metal oxide modified with an oxyanion of a Group VIB
 metal has not yet been confirmed, and it is not intended that this
 catalyst component should be limited to any particular structure.
 Other elements, such as alkali (Group IA) or alkaline earth (Group IIA)
 compounds may optionally be added to the present catalyst to alter
 catalytic properties. The addition of such alkali or alkaline earth
 compounds to the present catalyst may enhance the catalytic properties of
 components thereof, e.g., Pt or W, in terms of their ability to function
 as a hydrogenation/dehydrogenation component or an acid component.
 The Group IVB metal (i.e., Ti, Zr or Hf) and the Group VIB metal (i.e., Cr,
 Mo or W) species of the present catalyst are not limited to any particular
 valence state for these species. These species may be present in this
 catalyst in any possible positive oxidation value for these species.
 Subjecting the catalyst, e.g., when the catalyst comprises tungsten, to
 reducing conditions, e.g., believed to be sufficient to reduce the valence
 state of the tungsten, may enhance the overall catalytic ability of the
 catalyst to catalyze certain reactions, e.g., the hydrocracking of waxy
 feeds.
 Suitable sources of the Group IVB metal oxide, used for preparing the
 present catalyst, include compounds capable of generating such oxides,
 such as oxychlorides, chlorides, nitrates, etc., particularly of zirconium
 or titanium. Alkoxides of such metals may also be used as precursors or
 sources of the Group IVB metal oxide. Examples of such alkoxides include
 zirconium n-propoxide and titanium i-propoxide. Preferred sources of a
 Group IVB metal oxide are zirconium hydroxide, i.e., Zr(OH).sub.4, and
 hydrated zirconia. The expression, hydrated zirconia, is intended to
 connote materials comprising zirconium atoms covalently linked to other
 zirconium atoms via bridging oxygen atoms, i.e., Zr-O-Zr, further
 comprising available surface hydroxy groups. These available surface
 hydroxyl groups are believed to react with the source of an anion of a
 Group IVB metal, such as tungsten, to form the present acidic catalyst
 component. As suggested in the aformentioned article by K. Arata and M.
 Hino in Proceedings 9th International Congress on Catalysis, 4, 1727-1735
 (1988), precalcination of Zr(OH).sub.4 at a temperature of from about
 100.degree. C. to about 400.degree. C. results in a species which
 interacts more favorably with tungstate. This precalcination is believed
 to result in the condensation of ZrOH groups to form a polymeric zirconia
 species with surface hydroxyl groups. This polymeric species is referred
 to herein as a form of a hydrated zirconia.
 Treatment of hydrated zirconia with a base solution prior to contact with a
 source of tungstate may be preferable. More particularly, as demonstrated
 in Examples recited hereinafter, especially in Examples 16-25, refluxing
 hydrated zirconia in an NH.sub.4 OH solution having a pH of greater than 7
 was beneficial. Without wishing to be bound by any theory, it is theorized
 that the base-treated, hydrated zirconia is better because it has higher
 surface area. It is also theoretically possible that the base treatment
 alters surface hydroxyl groups on the hydrated zirconia, possibly in a
 manner which promotes a more desirable interaction with the source of
 tungstate later used.
 Suitable sources for the oxyanion of the Group VIB metal, preferably
 molybdenum or tungsten, include, but are not limited to, ammonium
 metatungstate or metamolybdate, tungsten or molybdenum chloride, tungsten
 or molybdenum carbonyl, tungstic or molybdic acid and sodium tungstate or
 molybdate.
 The hydrogenation/dehydrogenation component of the present catalyst may be
 derived from Group VIII metals, such as platinum, iridium, osmium,
 palladium, rhodium, ruthenium, nickel, cobalt, iron and mixtures of two or
 more thereof. These components may optionally be mixed with components
 derived from Group IVA metals, preferably Sn, and/or components derived
 from Group VIIB metals, preferably rhenium and manganese. These components
 may be added to the catalyst by methods known in the art, such as ion
 exchange, impregnation or physical admixture. For example, salt solutions
 of these metals may be contacted with the remaining catalyst components
 under conditions sufficient to combine the respective components. The
 metal containing salt is preferably water soluble. Examples of such salts
 include chloroplatinic acid, tetraammineplatinum complexes, platinum
 chloride, tin sulfate and tin chloride.
 The present catalyst may be prepared, for example, by impregnating the
 hydroxide or oxide, particularly the hydrated oxide, of the Group IVB
 metal with an aqueous solution containing an anion of the Group VIB metal,
 preferably tungstate or molybdate, followed by drying. Calcination of the
 resulting material may be carried out, preferably in an oxidizing
 atmosphere, at temperatures from about 500.degree. C. to about 900.degree.
 C., preferably from about 700.degree. C. to about 850.degree. C., and more
 preferably from about 750.degree. C. to about 825.degree. C. The
 calcination time may be up to 48 hours, preferably for about 0.5-24 hours,
 and more preferably for about 1.0-10 hours. In a most preferred
 embodiment, calcination is carried out at about 800.degree. C. for about 1
 to about 3 hours. The hydrogenation/dehydrogenation component of the
 catalyst (e.g., Group VIII metal, Group VIIB metal, etc.) may be added
 after or before the calcination step by techniques known in the art, such
 as impregnation, coimpregnation, coprecipitation, physical admixture, etc.
 The hydrogenation/dehydrogenation component may also be combined with the
 remaining catalyst components before or after these remaining components
 are combined with a binder or matrix material as described hereinafter.
 When a source of the hydroxide or hydrated oxide of zirconium is used,
 calcination, e.g., at temperatures greater than 500.degree. C., of the
 combination of this material with a source of an oxyanion of tungsten may
 be needed to induce the theorized chemical reaction which imparts the
 desired degree of acidity to the overall material. However, when more
 reactive sources of zirconia are used, it is possible that such high
 calcination temperatures may not be needed.
 In the present catalyst, of the Group IVB oxides, zirconium oxide is
 preferred; of the Group VIB anions, tungstate is preferred; and of the
 hydrogenation/dehydrogenation components, platinum and/or platinum-tin are
 preferred.
 Qualitatively speaking, elemental analysis of the present catalyst will
 reveal the presence of Group IVB metal, Group VIB metal and oxygen. The
 amount of oxygen measured in such an analysis will depend on a number of
 factors, such as the valence state of the Group IVB and Group VIB metals,
 the form of the hydrogenation/dehydrogenation component, moisture content,
 etc. Accordingly, in characterizing the composition of the present
 catalyst, it is best not to be restricted by any particular quantities of
 oxygen. In functional terms, the amount of Group VIB oxyanion in the
 present catalyst may be expressed as that amount which increases the
 acidity of the Group IVB oxide. This amount is referred to herein as an
 acidity increasing amount. Elemental analysis of the present catalyst may
 be used to determine the relative amounts of Group IVB metal and Group VIB
 metal in the catalyst. From these amounts, mole ratios in the form of
 XO.sub.2 /YO.sub.3 may be calculated, where X is said Group IVB metal,
 assumed to be in the form XO.sub.2, and Y is said Group VIB metal, assumed
 to be in the form of YO.sub.3. It will be appreciated, however, that these
 forms of oxides, i.e., XO.sub.2 and YO.sub.3, may not actually exist, and
 are referred to herein simply for the purposes of calculating relative
 quantities of X and Y in the present catalyst. The present catalysts may
 have calculated mole ratios, expressed in the form of XO.sub.2 /YO.sub.3,
 where X is at least one Group IVB metal (i.e., Ti, Zr, and Hf) and Y is at
 least one Group VIB metal (i.e., Cr, Mo, or W), of up to 1000, e.g., up to
 300, e.g., from 2 to 100, e.g., from 4 to 30.
 The amount of hydrogenation/dehydrogenation component may be that amount
 which imparts or increases the catalytic ability of the overall material
 to catalytically hydrogenate or dehydrogenate a hydrogenatable or
 dehydrogenatable organic compound under sufficient hydrogenation or
 dehydrogenation conditions. This amount is referred to herein as a
 catalytic amount. Quantitatively speaking, the present catalyst may
 comprise, for example, from about 0.001 to about 5 wt. %, e.g., from about
 0.1 to about 2 wt. %, of the hydrogenation/dehydrogenation component,
 especially when this component is a noble metal.
 It may be desirable to incorporate the present catalyst with another
 material to improve its properties. Such materials include active and
 inactive materials and synthetic or naturally occurring zeolites as well
 as inorganic materials such as clays, silica, and/or metal oxides. The
 latter may be either naturally occurring or in the form of gelatinous
 precipitates, sols, or gels including mixtures of silica and metal oxides.
 It is noted that the present catalyst need not contain any sulfate ion
 (U.S. Pat. No. 4,918,041), and therefore is expected to be more stable and
 also to be much easier to regenerate than sulfated catalysts, such as the
 superacid sulfated catalysts referred to in the aforementioned article by
 K. Arata and M. Hino in Proceedings 9th International Congress on
 Catalysis, 4, 1727-1735 (1988).
 The present catalyst includes a hydrogenation-dehydrogenation component to
 the catalyst. Metals having a strong hydrogenation function are preferred,
 especially platinum and the other noble metals such as palladium, rhodium,
 iridium, rhenium, although other metals capable of acting as a
 hydrogenation component may also be used, for example, nickel, tungsten or
 other metals of Group VIIIA of the Periodic Table (IU Table), either
 singly, in mixtures or in combination with other metals. The amount of the
 noble metal component may be in the range 0.001 to 5 wt. % of the total
 catalyst, e.g., from 0.1 to 2 wt. %. Base metal hydrogenation components
 may be added in somewhat greater amounts. The hydrogenation component can
 be exchanged onto the support material, impregnated into it or physically
 admixed with it. If the metal is to be impregnated into or exchanged onto
 the support, it may be done, for example, by treating the support with a
 platinum metal-containing ion. Suitable platinum compounds include
 chloroplatinic acid, platinous chloride and various compounds containing
 the platinum ammine complex. The metal compounds may be either compounds
 in which the metal is present in the cation or anion of the compound; both
 types of compounds can be used. Platinum compounds in which the metal is
 in the form of a cation of cationic complex, e.g., Pt(NH.sub.3).sub.4
 Cl.sub.2 are particularly useful, as are anionic complexes such as the
 vanadate and metatungstate ions. Cationic forms of other metals are also
 useful since they may be exchanged onto the support or impregnated into
 it.
 The catalyst may be subjected to a final calcination under conventional
 conditions in order to convert the metal component to the oxide form and
 to confer the required mechanical strength on the catalyst. Prior to use
 the catalyst may be subjected to presulfiding.
 When a source of hydrogenation metal, such as H.sub.2 PtCl.sub.6, is used
 as a source of a hydrogenation-dehydrogenation component in the present
 catalyst, it may be desirable to subject the present catalyst to extended
 reducing conditions, e.g., lasting more than 4 hours.
 The present catalyst can be shaped into a wide variety of particle sizes.
 Generally speaking, the particles can be in the form of a powder, a
 granule, or a molded product, such as an extrudate having particle size
 sufficient to pass through a 2 mesh (Tyler) screen and be retained on a
 400 mesh (Tyler) screen. In cases where the catalyst is molded, such as by
 extrusion, the catalyst can be extruded before drying or partially dried
 and then extruded. The present catalyst may be composited with a matrix
 material to form the finished form of the catalyst and for this purpose
 conventional matrix materials such as alumina, silica-alumina and silica
 are suitable with preference given to silica as a non-acidic binder. Other
 binder materials may be used, for example, titania, zirconia and other
 metal oxides or clays. The active catalyst may be composited with the
 matrix in amounts from 80:20 to 20:80 by weight, e.g., from 80:20 to 50:50
 active catalyst:matrix. Compositing may be done by conventional means
 including mulling the materials together followed by extrusion of
 pelletizing into the desired finished catalyst particles.
 The catalyst may be treated by conventional pre-sulfiding treatments, e.g.,
 by heating in the presence of hydrogen sulfide, to convert oxide forms of
 the metal components to their corresponding sulfides. The catalyst may
 also be treated with gases, such as H.sub.2 and N.sub.2, at elevated
 temperatures prior to contacting with feed to improve catalyst activity.
 Hydrocracking Conditions
 In the hydrocracking step of the present process, the feedstock is
 contacted with the aforedescribed catalyst in the presence of hydrogen
 under hydrocracking conditions of elevated temperature and pressure.
 Conditions of temperature, pressure, space velocity, hydrogen:feedstock
 ratio and hydrogen partial pressure which are similar to those used in
 conventional hydrocracking operations can conveniently be employed herein.
 Process temperatures of from about 175.degree. C. to about 500.degree. C.
 (from about 350.degree. F. to about 930.degree. F.) can conveniently be
 used although temperatures above about 425.degree. C. (about 800.degree.
 F.) will normally not be employed. Generally, temperatures of from about
 200.degree. C. to about 425.degree. C. (from about 400.degree. F. to about
 800.degree. F.) will be employed. Total pressure is usually in the range
 of from about 500 to about 20,000 kPa (from about 38 to about 2,886 psig)
 with pressures above about 7,000 kPa (about 986 psig) normally being
 preferred. The process is operated in the presence of hydrogen with
 hydrogen partial pressures normally being from about 600 to about 16,000
 kPa (from about 72 to about 2,305 psig). The hydrogen:feedstock ratio
 (hydrogen circulation rate) will normally be from about 10 to about 3,500
 n.l.l-1 (from about 56 to about 19,660 SCF/bbl.). The space velocity of
 the feedstock will normally be from about 0.1 to about 20 LHSV and
 preferably from about 0.1 to about 5.0 LHSV. Employing the foregoing
 hydrocracking conditions, conversion of feedstock to hydrocrackate product
 can be made to come within the range of from about 10 to about 99 weight
 percent. The hydrocracking conditions are advantageously selected so as to
 provide a conversion of from about 15 to about 80, and preferably from
 about 20 to about 70, weight percent.
 The conversion can be conducted by contacting the feedstock with a fixed
 stationary bed of catalyst, a fixed fluidized bed or with a transport bed.
 A simple configuration is a trickle-bed operation in which the feed is
 allowed to trickle through a stationary fixed bed. With such a
 configuration, it is desirable to initiate the hydrocracking reaction with
 fresh catalyst at a moderate temperature which is, of course, raised as
 the catalyst ages in order to maintain catalytic activity.
 Processing the Hydrocrackate Product to Provide a Lubricating Oil Base
 Stock Co-Product
 When operating at low to moderate conversion, the hydrocrackate product
 herein can be further processed by one or more downstream operations,
 themselves known in the art, to provide a high quality lubricating oil
 base stock co-product. For example, the hydrocrackate can be fractionated
 by distillation to provide a 650.degree. F.+ fraction which is then
 subjected to solvent refining (solvent extraction). The details of solvent
 refining are well known to those skilled in the art and, accordingly, need
 not be described in detail herein. It is sufficient to note that solvent
 refining generally consists of contacting, usually in a counter-current
 fashion, the material to be fractionated with a solvent which has a
 greater affinity for one of the fractions than the other. Many solvents
 are available for separating aromatic fractions from paraffinic fractions
 and the use of all such solvents is considered to be within the scope of
 the present invention. Although it is believed that solvents such as
 phenol, furfural, ethylene glycol, liquid sulfur dioxide, dimethyl
 sulfoxide, dimethylformamide, n-methyl pyrrolidone and n-vinyl pyrrolidone
 are all acceptable for use as solvents, furfural, phenol and n-methyl
 pyrrolidone are generally preferred. Further processing of the raffinate
 stream preferably comprises dewaxing the raffinate employing any of the
 known dewaxing operations such as, for example, "pressing and sweating",
 centrifugation, solvent dewaxing and catalytic dewaxing using shape
 selective zeolites.
 Alternatively, a heavy fraction of the hydrocrackate product, e.g., a
 650.degree. F.+ fraction, can be directly subjected to solvent dewaxing or
 catalytic dewaxing in accordance with known procedures to provide a high
 quality lubricating oil base stock.