A wide-cut lubricant base stock is made by hydroisomerizing and then catalytically dewaxing a waxy Fischer-Tropsch synthesized hydrocarbon fraction feed and comprises the entire dewaxate having an initial boiling point in the 650-75O.degree. F.+ range. Formulated lubricating oils made by admixing the base stock with a commercial automotive additive package meet all specifications, including low temperature properties, for multigrade internal combustion engine crankcase oils. The waxy feed has an initial boiling point in the 650-750.degree. F. range and continuously boils to an end point of at least 1050.degree. F.+. Lower boiling hydrocarbons produced by the process are separated from the base stock by simple flash distillation. The base stock comprises the entire dewaxate having an initial boiling point in the 650-750.degree. F. range.

BACKGROUND OF THE DISCLOSURE
 1. Field of the Invention
 The invention relates to a wide-cut, synthetic lubricant base stock
 synthesized from waxy hydrocarbons produced by a Fischer-Tropsch
 hydrocarbon synthesis process. More particularly the invention relates to
 a wide-cut lubricant base stock and formulated lubricating oil having a
 high VI, low pour point and wide boiling range, produced by
 hydroisomerizing a waxy Fischer-Tropsch synthesized hydrocarbon fraction,
 which is then catalytically dewaxed to produce the base stock.
 2. Background of the Invention
 Internal combustion engine crankcase and transmission oils, as well as some
 industrial oils, must maintain their lubricating quality over a wide range
 of temperature without solidifying or volatilizing. The industry is moving
 toward lighter viscosity grades (e.g., SAE 5W and 10W oils) for fuel
 economy reasons. However, the oils must also meet volatility
 specifications. In addition, heavier base stocks, from which fully
 formulated oils are made, are still utilized in many applications,
 including industrial oils. With conventional oils, the dewaxed raffinate
 is typically vacuum fractionated into a plurality of fractions of
 different viscosities and boiling ranges. The final lubricating oil is
 made by adding an additive package containing one or more additives such
 as a VI improver, an antioxidant, a detergent dispersant, antiwear
 additive, pour point depressant and the like, to the base stock. Lower
 viscosity base stocks have a higher concentration of lighter and lower
 boiling hydrocarbons, which tend to volatilize at higher temperatures.
 Conversely, higher boiling fractions, besides increasing the viscosity,
 can adversely affect low temperature properties, such as pour point. To
 use a wide cut derived from a conventional oil, will yield a base stock
 which will not meet either volatility or pour point requirements.
 Synthetic base stocks, such as polyalphaolefins (PAO's), are commercially
 available and have a combination of high viscosity index and low pour
 point. However, these oils are very expensive, tend to shrink seals and
 have a narrow boiling range. To be able to use a single, wide-cut oil
 fraction of lubricating quality as a base stock for a premium lubricating
 oil, where two or more fractions are now used, would simplify the
 production, transportation and cost of the oil.
 SUMMARY OF THE INVENTION
 The invention relates to a wide-cut lubricant base stock having a low pour
 point and high viscosity index (VI), and to a lubricant formed from the
 base stock, wherein the base stock is produced from a waxy, paraffinic
 Fischer-Tropsch synthesized hydrocarbon fraction having an initial boiling
 point in the range of 650-750.degree. F. (650-750.degree. F.+), by
 hydroisomerizing the waxy fraction to form a hydroisomerate, which is then
 catalytically dewaxed to reduce its pour point. Both the
 hydroisomerization and the catalytic dewaxing convert some of the
 650-750.degree. F.+ hydrocarbons into lower boiling hydrocarbons. These
 light hydrocarbons or lower boiling hydrocarbons, which boil below
 650-750.degree. F. (650-750.degree. F.-), are removed from the resulting
 650-750.degree. F.+ dewaxate which comprises the base stock. By wide-cut
 base stock is meant the entire 650-750.degree. F.+ dewaxate. This is in
 contrast to conventional base stocks, in which the 650-750.degree. F.+
 dewaxate is vacuum fractionated into a plurality of fractions of different
 viscosity and boiling range. By 650-750.degree. F.+ is meant that fraction
 of the hydrocarbons synthesized by the Fischer-Tropsch process having an
 initial boiling point in the range of from 650-750.degree. F. and
 continuously boiling up to an end point of at least, and preferably above,
 1050.degree. F. A Fischer-Tropsch synthesized hydrocarbon feed comprising
 this 650-750.degree. F.+ material, will hereinafter be referred to as a
 "waxy feed". By waxy is meant containing hydrocarbons which solidify at
 standard room temperature conditions of temperature and pressure. The waxy
 feed has negligible amounts of aromatics, sulfur and nitrogen compound
 impurities. The waxy feed also preferably has a T.sub.90 -T.sub.10
 temperature spread of at least 350.degree. F. The temperature spread
 refers to the temperature difference in .degree.F., between the 90 wt. %
 and 10 wt. % boiling points of the waxy feed. The wide-cut base stock is
 essentially isoparaffinic, in comprising at least 95 wt. % of non-cyclic
 isoparaffins, has a VI of at least 120, a pour point no higher than
 -10.degree. C. and is useful as a base stock for various lubricants,
 including lubricating oils (lube oils), greases and the like. Lube oils
 comprise an admixture of the base stock and lubricant additives, and
 include, for example, multi-grade internal combustion engine crankcase
 oils, automatic transmission oils, industrial oils and the like.
 The lower boiling hydrocarbons, known as light ends, are removed from the
 650-750.degree. F.+ dewaxate in order for the wide-cut base stock to meet
 volatility requirements. These light ends may simply be flashed off, to
 produce the wide-cut base stock. The use of simple flashing to remove the
 light ends (650-750.degree. F.-) in the process of the invention is
 significant, in that it eliminates the need for more costly vacuum
 distillation commonly used with conventional, petroleum oil raffinates.
 The superior properties of the base stock of the invention, compared to
 conventional base stocks derived from petroleum oil or slack wax, results
 from the combination of the relatively pure and essentially paraffinic
 Fischer-Tropsch waxy feed, and preferably a waxy feed produced by a slurry
 Fischer-Tropsch process in the presence of a catalyst having a cobalt
 catalytic component, the hydroisomerization, catalytic dewaxing and
 removal of the light ends from the dewaxate.
 In the practice of the invention, the hydroisomerization is accomplished by
 reacting the waxy feed with hydrogen in the presence of a suitable
 hydroisomerization and preferably a dual function hydroisomerization
 catalyst comprising at least one catalytic metal component to give the
 catalyst a hydrogenation/dehydrogenation function and an acidic metal
 oxide component to give the catalyst an acid hydroisomerization function.
 The hydroisomerization converts a portion of the waxy feed
 (650-750.degree. F.+) to lower boiling material (650-750.degree. F.-)
 which, while useful for fuels, is not useful as base stock material. The
 hydroisomerate may be dewaxed with or without prior removal of the lower
 boiling material. Dewaxing is accomplished by reacting the hydroisomerate
 with hydrogen in the presence of a dewaxing catalyst to form a dewaxate,
 from which the light ends are removed.

DETAILED DESCRIPTION
 The waxy feed preferably comprises the entire 650-750.degree. F.+ fraction
 formed by the hydrocarbon synthesis process, with the exact cut point
 between 650.degree. F. and 750.degree. F. being determined by the
 practitioner, and the exact end point preferably above 1050.degree. F.
 determined by the catalyst and process variables used for the synthesis.
 The waxy feed may also contain lower boiling material (650-750.degree.
 F.-), if desired. While this lower boiling material is not useful for a
 lubricant base stock, when processed according to the process of the
 invention it is useful for fuels. The waxy feed also comprises more than
 90 %, typically more than 95 % and preferably more than 98 wt. %
 paraffinic hydrocarbons, most of which are normal paraffins, and this is
 what is meant by "paraffinic" in the context of the invention. It has
 negligible amounts of sulfur and nitrogen compounds (e.g., less than 1
 wppm), with less than 2,000 wppm, preferably less than 1,000 wppm and more
 preferably less than 500 wppm of oxygen, in the form of oxygenates. The
 aromatics content, if any, is less than 0.5, more preferably less than 0.3
 and still more preferably less than 0.1 wt. %. Waxy feeds having these
 properties and useful in the process of the invention have been made using
 a slurry Fischer-Tropsch process with a catalyst having a catalytic cobalt
 component. In the practice of the invention, it is preferred that a slurry
 Fischer-Tropsch hydrocarbon synthesis process be used for synthesizing the
 waxy feed and particularly one employing a Fischer-Tropsch catalyst
 comprising a catalytic cobalt component to provide a high alpha for
 producing the more desirable higher molecular weight paraffins.
 The (T.sub.90 -T.sub.10) temperature spread of the waxy feed, while
 preferably being at least 350.degree. F., is more preferably at least
 400.degree. F. and still more preferably at least 450.degree. F., and may
 range between 350.degree. F. to 700.degree. F. or more. Waxy feeds
 obtained from a slurry Fischer-Tropsch process employing a catalyst
 comprising a composite of a catalytic cobalt component and a titania have
 been made meeting the above degrees of paraffinicity, purity and boiling
 point range, having T.sub.10 and T.sub.90 temperature spreads of as much
 as 490.degree. F. and 600.degree. F., having more than 10 wt. % of
 1050.degree. F.+ material and more than 15 wt. % of 1050.degree. F.+
 material with respective initial and end boiling points of500.degree.
 F.-1245.degree. F. and 350.degree. F.-1220.degree. F. Both of these
 samples continuously boiled over their entire boiling range. The lower
 boiling point of 350.degree. F. was obtained by adding some of the
 condensed hydrocarbon overhead vapors from the reactor to the hydrocarbon
 liquid filtrate removed from the reactor. Both of these waxy feeds were
 suitable for use in the process of the invention, in that they contained
 material having an initial boiling point in the range of 650-750.degree.
 F., which continuously boiled to and end point of above 1050.degree. F.,
 and a T.sub.90 -T.sub.10 temperature spread of more than 350.degree. F.
 Both the waxy feed and the lubricant base stock produced from the waxy feed
 by the process of the invention contain less heteroatom, oxygenate,
 naphthenic and aromatic compounds than lubricant base stocks derived from
 petroleum oil and slack wax. Unlike base stocks derived from petroleum oil
 and slack wax, which contain appreciable amounts (e.g., at least 10 wt. %)
 of cyclic hydrocarbons, such as naphthenes and aromatics, the base stocks
 produced by the process of the invention comprise at least 95 wt. %
 non-cyclic isoparaffins, with the remainder normal paraffins. The base
 stocks of the invention differ from PAO base stocks in that the aliphatic,
 non-ring isoparaffins contain primarily methyl branches, with very little
 (e.g., less than 1 wt. %) branches having more than five carbon atoms.
 Thus, the composition of the base stock of the invention is different from
 one derived from a conventional petroleum oil or slack wax, or a PAO. The
 base stock of the invention comprises essentially (.gtoreq.99+wt. %) all
 saturated, paraffinic and non-cyclic hydrocarbons. Sulfur, nitrogen and
 metals are present in amounts of less than 1 wppm and are not detectable
 by x-ray or Antek Nitrogen tests. While very small amounts of saturated
 and unsaturated ring structures may be present, they are not identifiable
 in the base stock by presently known analytical methods, because the
 concentrations are so small. While the base stock of the invention is a
 mixture of various molecular weight hydrocarbons, the residual normal
 paraffin content remaining after hydroisomerization and dewaxing will
 preferably be less than 5 wt. % and more preferably less than 1 wt. %,
 with at least 50% of the oil molecules containing at least one branch, at
 least half of which are methyl branches. At least half and more preferably
 at least 75% of the remaining branches are ethyl, with less than 25% and
 preferably less than 15% of the total number of branches having three or
 more carbon atoms. The total number of branch carbon atoms is typically
 less than 25%, preferably less than 20% and more preferably no more than
 15% (e.g., 10-15%) of the total number of carbon atoms comprising the
 hydrocarbon molecules. PAO oils are a reaction product of alphaolefins,
 typically 1-decene and also comprise a mixture of molecules. However, in
 contrast to the molecules of the base stock of the invention, which have a
 more linear structure comprising a relatively long back bone with short
 branches, the classic textbook description of a PAO base stock is a
 star-shaped molecule, and particularly tridecane typically illustrated as
 three decane molecules attached at a central point. PAO molecules have
 fewer and longer branches than the hydrocarbon molecules that make up the
 base stock of the invention. Thus, the molecular make up of a base stock
 of the invention comprises at least 95 wt. % non-cyclic isoparaffins
 having a relatively linear molecular structure, with less than half the
 branches having two or more carbon atoms and less than 25 % of the total
 number of carbon atoms present in the branches. Because the base stocks of
 the invention and lubricating oils based on these base stocks are
 different, and most often superior to, lubricants formed from other base
 stocks, it will be obvious to the practitioner that a blend of another
 base stock with at least 20, preferably at least 40 and more preferably at
 least 60 wt. % of the base stock of the invention, will still provide
 superior properties in many most cases, although to a lesser degree than
 only if the base stock of the invention is used. Such additional base
 stocks may be selected from the group consisting of (i) a
 hydrocarbonaceous base stock, (ii) a synthetic base stock and mixture
 thereof. By hydrocarbonaceous is meant a primarily hydrocarbon type base
 stock derived from a conventional mineral oil, shale oil, tar, coal
 liquefaction, mineral oil derived slack wax, while a synthetic base stock
 will include a PAO, polyester types and other synthetics.
 As those skilled in the art know, a lubricant base stock is an oil
 possessing lubricating qualities boiling in the general lubricating oil
 range and is useful for preparing various lubricants such as lubricating
 oils and greases. Lubricating or lube oils are prepared by combining the
 base stock with an effective amount of at least one additive or, more
 typically, an additive package containing more than one additive, wherein
 the additive is at least one of a detergent, a dispersant, an antioxidant,
 an antiwear additive, a pour point depressant, a VI improver, a friction
 modifier, a demulsifier, an antifoamant, a corrosion inhibitor, and a seal
 swell control additive. Of these, those additives common to most
 formulated lubricating oils include a detergent, a dispersant, an
 antioxidant, an antiwear additive and a VI improver, with the others being
 optional, depending on the intended use of the oil. An effective amount of
 one or more additives or an additive package containing one or more such
 additives is admixed with, added to or blended into the base stock, to
 meet one or more specifications, such as those relating to a lube oil for
 an internal combustion engine crankcase, an automatic transmission, a
 turbine or jet, hydraulic oil, industrial oil, etc., as is known. Various
 manufacturers sell such additive packages for adding to a base stock or to
 a blend of base stocks to form fully formulated lube oils for meeting
 performance specifications required for different applications or intended
 uses, and the exact identity of the various additives present in an
 additive pack is typically maintained as a trade secret by the
 manufacturer. However, the chemical nature of the various additives is
 known to those skilled in the art. For example, alkali metal sulfonates
 and phenates are well known detergents, with PIBSA (polyisobutylene
 succinic anhydride) and PIBSA-PAM (polyisobutylene succinic anhydride
 amine) with or without being borated, being well known and used
 dispersants. VI improvers and pour point depressants include acrylic
 polymers and copolymers such as polymethacrylates, polyalkylmethacrylates,
 as well as olefin copolymers, copolymers of vinyl acetate and ethylene,
 dialkyl fumarate and vinyl acetate, and others which are known. The most
 widely used antiwear additives are metal dialkyldithiophosphates such as
 ZDDP in which the metal is zinc, metal carbamates and dithiocarbamates,
 ashless types which include ethoxylated amine dialkyldithiophosphates and
 dithiobenzoates. Friction modifiers include glycol esters and ether
 amines. Benzotriazole is a widely used corrosion inhibitor, while
 silicones are well known antifoamants. Antioxidants include hindered
 phenols and hindered aromatic amines such as 2, 6-di-tert-butyl-4-n-butyl
 phenol and diphenyl amine, with copper compounds such as copper oleates
 and copper-PIBSA being well known. This is meant to be an illustrative,
 but nonlimiting list of the various additives used in lube oils. That the
 performance of a lube oil of the invention differs from that of
 conventional and PAO oils with the same level of the same additives,
 demonstrates that the chemistry of the base stock of the invention is
 different from that of the prior art base stocks.
 During hydroisomerization of the waxy feed, conversion of the
 650-750.degree. F.+ fraction to material boiling below this range (lower
 boiling material, 650-750.degree. F.-) will range from about 20-80 wt. %,
 preferably 30-70 % and more preferably from about 30-60 %, based on a once
 through pass of the feed through the reaction zone. The waxy feed will
 typically contain 650-750.degree. F.- material prior to the
 hydroisomerization and at least a portion of this lower boiling material
 will also be converted into lower boiling components. Any olefins and
 oxygenates present in the feed are hydrogenated during the
 hydroisomerization. The temperature and pressure in the hydroisomerization
 reactor will typically range from 300-900.degree. F. (149-482.degree. C.)
 and 300-2500 psig, with preferred ranges of 550-750.degree. F.
 (288-400.degree. C.) and 300-1200 psig, respectively. Hydrogen treat rates
 may range from 500 to 5000 SCF/B, with a preferred range of 2000-4000
 SCF/B. The hydroisomerization catalyst comprises one or more Group VIII
 metal catalytic components, and preferably non-noble metal catalytic
 component(s), and an acidic metal oxide component to give the catalyst
 both a hydrogenation/dehydrogenation function and an acid hydrocracking
 function for hydroisomerizing the hydrocarbons. The catalyst may also have
 one or more Group VIB metal oxide promoters and one or more Group IB metal
 components as a hydrocracking suppressant. In a preferred embodiment the
 catalytically active metal comprises cobalt and molybdenum. In a more
 preferred embodiment the catalyst will also contain a copper component to
 reduce hydrogenolysis. The acidic oxide component or carrier may include,
 alumina, silica-alumina, silica-alumina-phosphates, titania, zirconia,
 vanadia, and other Group II IV, V or VI oxides, as well as various
 molecular sieves, such as X, Y and Beta sieves. It is preferred that the
 acidic metal oxide component include silica-alumina and particularly
 amorphous silica-alumina in which the silica concentration in the bulk
 support (as opposed to surface silica) is less than about 50 wt. % and
 preferably less than 35 wt. %. A particularly preferred acidic oxide
 component comprises amorphous silica-alumina in which the silica content
 ranges from 10-30 wt. %. Additional components such as silica, clays and
 other materials as binders may also be used. The surface area of the
 catalyst is in the range of from about 180-400 m.sup.2 /g, preferably
 230-350 m.sup.2 /g, with a respective pore volume, bulk density and side
 crushing strength in the ranges of 0.3 to 1.0 mL/g and preferably
 0.35-0.75 mL/g; 0.5-1.0 g/mL, and 0.8-3.5 kg/mm. A particularly preferred
 hydroisomerization catalyst comprises cobalt, molybdenum and, optionally,
 copper components, together with an amorphous silica-alumina component
 containing about 20-30 wt. % silica. The preparation of such catalysts is
 well known and documented. Illustrative, but non-limiting examples of the
 preparation and use of catalysts of this type may be found, for example,
 in U.S. Pat. Nos. 5,370,788 and 5,378,348. The hydroisomerization catalyst
 is most preferably one that is resistant to deactivation and to changes in
 its selectivity to isoparaffin formation. It has been found that the
 selectivity of many otherwise useful hydroisomerization catalysts will be
 changed and that the catalysts will also deactivate too quickly in the
 presence of sulfur and nitrogen compounds, and also oxygenates, even at
 the levels of these materials in the waxy feed. One such example comprises
 platinum or other noble metal on halogenated alumina, such as fluorided
 alumina, from which the fluorine is stripped by the presence of oxygenates
 in the waxy feed. A hydroisomerization catalyst that is particularly
 preferred in the practice of the invention comprises a composite of both
 cobalt and molybdenum catalytic components and an amorphous alumina-silica
 component, and most preferably one in which the cobalt component is
 deposited on the amorphous silica-alumina and calcined before the
 molybdenum component is added. This catalyst will contain from 10-20 wt. %
 MoO.sub.3 and 2-5 wt. % CoO on an amorphous alumina-silica support
 component in which the silica content ranges from 10-30 wt. % and
 preferably 20-30 wt. % of this support component. This catalyst has been
 found to have good selectivity retention and resistance to deactivation by
 oxygenates, sulfur and nitrogen compounds found in the Fischer-Tropsch
 produced waxy feeds. The preparation of this catalyst is disclosed in U.S.
 Pat. Nos. 5,756,420 and 5,750,819, the disclosures of which are
 incorporated herein by reference. It is still further preferred that this
 catalyst also contain a Group IB metal component for reducing
 hydrogenolysis. The entire hydroisomerate formed by hydroisomerizing the
 waxy feed may be dewaxed, or the lower boiling, 650-750.degree. F.-
 components may be removed by rough flashing or by fractionation prior to
 the dewaxing, so that only the 650-750.degree. F.+ components are dewaxed.
 The choice is determined by the practitioner. The lower boiling components
 may be used for fuels. Employing a rough flash and not fractionating the
 resulting dewaxate base stock into a plurality of fractions, represents a
 considerable savings in equipment and energy consumption, which is not
 possible with a conventional, petroleum derived raffinate.
 The practice of the invention is not limited to the use of any particular
 dewaxing catalyst, but may be practiced with any dewaxing catalyst which
 will reduce the pour point of the hydroisomerate and preferably those
 which provide a reasonably large yield of lube oil base stock from the
 hydroisomerate. These include shape selective molecular sieves which, when
 combined with at least one catalytic metal component, have been
 demonstrated as useful for dewaxing petroleum oil fractions and slack wax
 and include, for example, ferrierite, mordenite, ZSM-5, ZSM-11, ZSM-23,
 ZSM-35, ZSM-22 also known as theta one or TON, and the
 silicoaluminophosphates known as SAPO's (5,135,638). The dewaxing may be
 accomplished with the catalyst in a fixed, fluid or slurry bed. Typical
 dewaxing conditions include a temperature in the range of from about
 400-600.degree. F., a pressure of 500-900 psig, H.sub.2 treat rate of
 1500-3500 SCF/B for flow-through reactors and LHSV of 0.1-10, preferably
 0.2-2.0. The dewaxing is typically conducted to convert no more than 40
 wt. % and preferably no more than 30 wt. % of the 650-750.degree. F.+
 hydroisomerate to lower boiling material. A dewaxing catalyst comprising a
 catalytic platinum component and a hydrogen form of mordenite component
 (Pt/H-mordenite) is preferred.
 It has been found that not all dewaxing catalysts and conditions are
 equivalent when used to dewax the very pure and highly paraffinic
 hydroisomerate produced by the invention, due to cracking which produces
 C.sub.3 -C.sub.4 gas and light naphtha For example, U.S. Pat. No.
 3,539,498 discloses that by using 0.5 wt. % platinum on H-mordenite for
 dewaxing a light lube oil distillate feed (600-700.degree. F.) down to a
 pour point of -10.degree. F., the product yield was only 68 volume %. U.S.
 Pat. No. 4,057,488 discloses a 65.5 volume % yield from using platinum on
 H-mordenite to dewax a de-nitrogenated raffinate boiling between
 740-950.degree. F. It has been surprisingly and unexpectedly found that by
 using Pt/H-mordenite to dewax a hydroisomerized Fischer-Tropsch waxy feed
 boiling in the lube oil range, these high conversion levels and low yields
 do not occur, and the resulting wide-cut base stock has a lower pour point
 and higher VI than expected. The base stock comprises at least 99 wt. % of
 a mixture of paraffins and isoparaffins, boils continuously over its
 boiling range, from its initial boiling point in the range of
 650-750.degree. F., through to its end boiling point of at least
 1050.degree. F., with at least 95 wt. % being non-cyclic isoparaffins. The
 initial boiling point is preferably at least 700.degree. F., and still
 more preferably at least 750.degree. F., with at least 5 wt. % boiling
 above 1050.degree. F. The VI of the base stock is at least 120, preferably
 at least 130 and more preferably at least 140. The pour point of the base
 stock is no higher than -10.degree. C. and preferably less than
 -15.degree. C.
 Referring to the FIGURE, a slurry hydrocarbon synthesis reactor 10 is shown
 as comprising a cylindrical vessel with a gas line 12 through which a
 synthesis gas comprising a mixture of H.sub.2 and CO is introduced into a
 plenum space 14 at the bottom of the vessel and then injected up through a
 gas injection means briefly illustrated by dashed line 16 and into a
 slurry (not shown) comprising bubbles of the uprising synthesis gas and
 solid particles of a Fischer-Tropsch catalyst in a hydrocarbon slurry
 liquid, which comprises synthesized hydrocarbons which are liquid at the
 temperature and pressure in the reactor. Suitable gas injection means
 comprises an otherwise gas and liquid impermeable, horizontal tray or
 plate containing a plurality of gas injectors horizontally arrayed across
 and extending through the tray. The H.sub.2 and CO in the slurry react in
 the presence of the particulate catalyst to form predominantly paraffinic
 hydrocarbons, most of which are liquid at the reaction conditions,
 particularly when the catalyst includes a catalytic cobalt component. A
 filter means immersed in the slurry, which is simply indicated by box 18,
 separates the hydrocarbon liquids in the reactor from the catalyst
 particles and passes the hydrocarbon liquids out of the reactor via line
 20. Unreacted synthesis gas and gas products of the hydrocarbon synthesis
 reaction pass up and out the top 22 of the slurry and into a gas
 collection space 24 over the slurry, from where they are removed from the
 hydrocarbon synthesis reactor as tail gas via line 26. The tail gas is
 then passed through a first heat exchanger 28, which cools the hot gas
 from the hydrocarbon synthesis reactor to condense some of the hydrocarbon
 synthesis reaction water and the heavier hydrocarbon vapors (e.g.,
 .about.500-700.degree. F. boiling range) to liquid, with the cooled gas
 and liquid mixture then passed via line 30 into a hot separation vessel
 32, which may be a simple knock-out drum. The condensed hydrocarbon
 liquids are removed via line 34 and passed into the hydroisomerization
 reactor 36, along with the hydrocarbon liquids removed from the
 hydrocarbon synthesis reactor from line 20. The hydrocarbon liquids
 removed from the hydrocarbon synthesis reactor via line 20 comprise mostly
 650-750.degree. F.+ boiling paraffinic hydrocarbons. The water is removed
 from the separator (not shown), and the water and hydrocarbon-reduced gas
 is removed via line 38 and passed through a second heat exchanger 40 which
 cools it down further (e.g., 50-150.degree. F.), to condense out more
 water and lighter C.sub.5+ (e.g., C.sub.5+ up to about 500.degree. F.
 boiling range) hydrocarbon vapors as liquid, with the gas and liquid
 mixture passed into a cold separator 44, via line 42, to separate the gas
 from the water and hydrocarbon liquid layers. The gas is removed from the
 separator via line 64 and the hydrocarbon liquids via line 46. In the
 hydroisomerization reactor 36, the mixture of heavy 700.degree. F.+
 boiling hydrocarbon liquids removed from the hydrocarbon synthesis reactor
 and those recovered from the hot separator, react with hydrogen passed
 into the reactor via line 37, in the presence of a hydroisomerization
 catalyst, to hydroisomerize the paraffins to branched or isoparaffins as
 hydroisomerate. The hydroisomerate is removed from reactor 36 and passed,
 via line 48, into a fractionator 50, in which the lighter hydrocarbons are
 separated from the 650-750.degree. F.+ fraction as naphtha and diesel
 fractions via lives 51 and 53, respectively. The lighter hydrocarbon
 liquid recovered from cold separator 44 are passed, via line 46 into line
 48, where they are mixed with the hydroisomerate entering the
 fractionator. The 650-750.degree. F.+ hydroisomerate is removed from the
 fractionator via line 32 and passed into a catalytic dewaxing reactor 54,
 via line 56, in which it reacts with hydrogen entering the reactor via
 line 55, in the presence of a dewaxing catalyst to further reduce the pour
 point of the hydroisomerate and produce the base stock. The dewaxing
 catalyst is preferably platinum on mordenite. The catalytic dewaxing
 cracks a portion (e.g., .about.20 volume %) of the 650-750.degree. F.+
 material to mostly gas and naphtha hydrocarbon fractions and lowers the
 pour point of the remaining 650-750.degree.F.+ base stock, with the
 mixture of gas and the liquid 650-750.degree. F.+ base stock leaving the
 catalytic dewaxer via line 56 and passing into a separator 58, in which
 the hydrocarbons boiling below the desired initial boiling point of at
 least 650.degree. F., preferably at least 700.degree. F. and more
 preferably at least 750.degree. F. are simply flashed off and removed with
 the gas products of the dewaxing. The separator is a simple drum separator
 in which the gas products and light fraction are separated from the base
 stock and removed via line 62. The resulting wide cut base stock is
 removed from the separator via line 60.
 In a Fischer-Tropsch hydrocarbon synthesis process, liquid and gaseous
 hydrocarbon products are formed by contacting a synthesis gas comprising a
 mixture of H.sub.2 and CO with a Fischer-Tropsch catalyst, in which the
 H.sub.2 and CO react to form hydrocarbons under shifting or non-shifting
 conditions and preferably under non-shifting conditions in which little or
 no water gas shift reaction occurs, particularly when the catalytic metal
 comprises Co, Ru or mixture thereof. Suitable Fischer-Tropsch reaction
 types of catalyst comprise, for example, one or more Group VIII catalytic
 metals such as Fe, Ni, Co, Ru and Re. In one embodiment the catalyst
 comprises catalytically effective amounts of Co and one or more of Re, Ru,
 Fe, Ni, Th, Zr, Hf, U, Mg and La on a suitable inorganic support material
 preferably one which comprises one or more refractory metal oxides.
 Preferred supports for Co containing catalysts comprise titania,
 particularly when employing a slurry HCS process in which higher molecular
 weight, primarily paraffinic liquid hydrocarbon products are desired.
 Useful catalysts and their preparation are known and illustrative, but
 nonlimiting examples may be found, for example, in U.S. Pat Nos.
 4,568,663; 4,663,305; 4,542,122; 4,621,072 and 5,545,674. Fixed bed, fluid
 bed and slurry hydrocarbon synthesis processes are well known and
 documented in the literature. In all of these processes the synthesis gas
 is reacted in the presence of a suitable Fischer-Tropsch type of
 hydrocarbon synthesis catalyst, at reaction conditions effective to form
 hydrocarbons. Some of these hydrocarbons will be liquid, some solid (e.g.,
 wax) and some gas at standard room temperature conditions of temperature
 and pressure of 25.degree. C. and one atmosphere, particularly if a
 catalyst having a catalytic cobalt component is used. Slurry
 Fischer-Tropsch hydrocarbon synthesis processes are often preferred
 because they are able to produce relatively high molecular weight,
 paraffinic hydrocarbons when using a cobalt catalyst. In a slurry
 hydrocarbon synthesis process, which is a preferred process in the
 practice of the invention, a synthesis gas comprising a mixture of H.sub.2
 and CO is bubbled up as a third phase through a slurry in a reactor which
 comprises a particulate Fischer-Tropsch type hydrocarbon synthesis
 catalyst dispersed and suspended in a slurry liquid comprising hydrocarbon
 products of the synthesis reaction which are liquid at the reaction
 conditions. The mole ratio of the hydrogen to the carbon monoxide may
 broadly range from about 0.5 to 4, but is more typically within the range
 of from about 0.7 to 2.75 and preferably from about 0.7 to 2.5. The
 stoichiometric mole ratio for a Fischer-Tropsch reaction is 2.0, but in
 the practice of the present invention it may be increased to obtain the
 amount of hydrogen desired from the synthesis gas for other than the
 hydrocarbon synthesis reaction. In the slurry process, the mole ratio of
 the H.sub.2 to CO is typically about 2.1/1. Slurry hydrocarbon synthesis
 process conditions vary somewhat depending on the catalyst and desired
 products. Typical conditions effective to form hydrocarbons comprising
 mostly C.sub.5+ paraffins, (e.g., C.sub.5+ -C.sub.200) and preferably
 C.sub.10+ paraffins in a slurry process employing a catalyst comprising a
 supported cobalt component include, for example, temperatures, pressures
 and hourly gas space velocities in the range of from about 320-600.degree.
 F., 80-600 psi and 100-40,000 V/hr/V, expressed as standard volumes of the
 gaseous CO and H.sub.2 mixture (60.degree. F., 1 atm) per hour per volume
 of catalyst, respectively. The hydrocarbons which are liquid at the
 reaction conditions and are removed from the reactor (using filtration
 means and, optionally a hot separator to recover C.sub.10+ from the HCS
 gas) in a slurry process) comprise mostly (e.g.,&gt;50 wt. % and typically
 60 wt. % or more) hydrocarbons boiling over 650-750.degree. F. The Table
 below shows the fractional make-up (.+-.10 wt. % for each fraction) of
 hydrocarbons synthesized in a slurry hydrocarbon synthesis reactor using a
 catalyst comprising cobalt and rhenium on a titania support.