CA2198213A1 - Wax hydroisomerization process - Google Patents

Abstract

Petroleum waxes are converted to high Viscosity Index lubricants by a synergistic process which employs two catalysts. Viscosity Index and yield are greater for product of the integrated catalyst process than they are for the product of either of the catalysts alone. The wax feed which may be pretreated by mild hydrocracking, is first subjected to isomerization in the presence of hydrogen over a low acidity zeolite isomerization catalyst which effects a preferential isomerization of the paraffin components in the feed to less waxy, high V.I. isoparaffins. The isomerization is operated at a pressure of at least 5617 kPaabs hydrogen partial pressure (reactor inlet). The catalyst is preferably a noble metal containing zeolite beta catalyst which contains boron as a framework component of the zeolite in order to give a low alpha value, typically below 20. The isomerization is carried out a a temperature of 345 ~C with conversion in the range of 10 to 40 wt.% of the feed. The product of the isomerization process is then contacted with a shape-selective catalyst in order to further reduce the pour point. Preferably ZSM-22, ZSM-23 or ZSM-35 is used. The shape-selective catalyst preferably contains noble metals such as Pd or Pt.

Description

WO9610rl~5 2 t ~ g 2 t ~ PCT/USg5/11036 ~ 1 HYDROlC~ hKI~A~ION PROCESS

CROSS-P~T'~NCE TO RT'TA~ED APPLICATIONS
This application i8 related to co-pending application Serial No. 08/01i,949 (continuation of S.N. 07/548,702) entitled Production of High Viscosity Index Lubricants, which describes a two-step process for producing high Viscosity Index lubricants by hydrocracking and hydroisomerization of petroleum-wax feeds using a low acidity zeolite beta hydroisomerization catalyst. Serial No. 08/017,955, also entitled Production of High Viscosity Index Lubricants, describes a wax hydroisomerization process using zeolite catalysts of controlled low acidity at high pressures. The instant application is a continuation-in-part of Serial No. 08/017,955. The instant application is also a continuation-in-part of Serial No.
08/017,949. Serial No. 08/017,955 is incorporated by reference in the instant application. CoLL~ ollrl;ng European Patent No. 464,547Al, (a patent which specifies the use of low acidity zeolite beta for wax isomerization) is also incoL~L~ted by reference.

FITTn OF T~E TNV~NTION
This invention relates to the production of high Viscosity Index lubricants by employing a process in which two dewaxing catalysts operate synergistically. The feed may be hyd.u~L-cked prior to the catalytic dewaxing process. The effluent of the dew~YlnrJ process may also be 11YdL ~ LL ~ated.

1INI, OF ~R~ INV~NTION~
Mineral oil based lubricants are conventionally p~uduced by a separative sequence carried out in the petroleum refinery which comprises fractionation of a paraffinic crude oil under ai ~ ric pressure followed by fractionation under vacuum to produce distillate fractions (neutral oils) and a residual fraction which, after W096~7715 2 ~ 982 ~ 3 - PC~US9~11036 .
~P~ph~lting and severe solvent ~L_ai L may also be used as a lubricant basestock. This refined residual fraction i8 usually referred to as bright stock. Neutral oils, after solvent extraction to remove low viscosity index IV.I.) ~ntS, are conventionally subjected to do _Ying~ either by solvent or catalytic ~ - ng p-~e~ses, to achieve the desired pour~point. The dewaxed lube stock may be hydrofinished to improve stability and remove color bodies. Viscosity Index (V.I.) is a reflection of the amount of viscosity decrease a lubricant undergoes with an increase in temperature. The products of solvent dewaxing are dewaxed lube oil and slack wax. Slack wax typically contains 60% to 90% wax with the balance being entrained oil. In some instances it is desirable to purify the slack wax of entrained oil by subjecting the slack wax to a deoiling step in which the slack wax is dlluted with dewaxing solvents and filtered at a t a~uL~ higher than that used in the filtering step used to produce the slack wax. The purified wax is termed deoiled wax, and contains greater than ~5% wax. The byproduct of the second filtration typically contains 50%
wax and is termed foots oil.
Catalytic ~ Ying of lube stocks is a~ hP~ by converting waxy molecules to light products by cracking, or by isomerizing waxy molecules to form species which remain in the dewaxed lube. Dewaxing catalysts ~ese,v~ high yield primarily by having pore structures which inhibit cracking of~cyclic and highly branched species, those generally associated with dewaxed lube, while permitting easier access to catalytically active sites to near-linear molecules, of which wax is generally ~ * e~.~'. Cataiysts which significantly reduce the acces6ibility of species on the basis of molecular size are termed shape selective.
Increasing the shape selectivity of a dewaxing catalyst will frequently increase the yield of dewaxed oil.
The shape selectivity of a dewaxing catalyst is limited practically by its ability to convert waxy molecules which have a slightly branched structure. These .

21~'2~
WO96/07715 1'CTIUS95/11036 types of species are more commonly associated with hoavier lube stocks, such as bright stocks. Highly shape selective dewaxing catalysts may be unable to convert heavy, branched wax species leadlng to a hazy lube appearance at ambient temperature and high cloud point relative to pour point.
~ Conventional lube refining te~hn~ c rely upon the proper 6election and use of crude stocks, usually of a paraffinlc character, which produce lube fractions with desired quallties ln adequate amounts. The range of p~r~icFihle crude sources may, however, be extended by the lube hydLoe-~cking process which is capable of utilizing crude stocks of marginal or poor quality, usually with a higher aromatic content than the best paraffinic crudes.
The lube hydrocracking process, which is well established in the petroleum refining industry, generally comprises an initial l,~lLue~cking step carried out under high pressure, at high temperature, and in the presence of a bifunctional catalyst which effects partial saturation and ring opening of the aromatic ~ ~ which are present in the feed.
The L~lLv~L~cked product is then subjected to dewaxing in order to reach the target pour point since the hydLvvL~cked product usually contains species with relatively high pour points. Fr~uell~ly the liquid product from the dewaxing step is subjected to a low temperature, high ~esDuLe I.ydLvLLeating step to reduce the aromatic content of the lube to the desired level.
Current trends in the design of automotive engines are associated with higher operating t~ ~LuLe8 as the efficiency of the engines increases. These higher operating t~ UL~C require successively higher quality lubricants. One of the requirements is for higher visco6ity indices (V.I.) in order to reduce the effects of the higher operating t~ ~tules on the viscosity of the engine lubricants. High V.I. values have conventionally been attained by the use of V.I. ; _~ve~ e.g.
polyacrylates and poly~yLe..es. V.I. improvers tend to undergo de~dation due to high t~ LuLes and high shear rates encountered in the engine. The more stressing 2 1 9~2 1-3 Wo96~M15 PCT~S95/11036 conditions encountered in high~efficiency engines result in ~ven faster deyLadaLion of oils which employ significant amounts of V.I. improvers. Thus, there is a continuing need for automotive lubricants which are based on fluids of high Viscosity Index and which are resistant to the high t~ ~tUL~, high shear rate conditions encountered in modern engines.
6ynthetic lubricants ~L~duced by the polymerization of olefins in the presence of certain catalysts have been shown to possess excellent V.I.~values, but they are relatively expensive to produce. There is therefore a need for the production of high V.I. lubricants from minerai oil stocks which may be ~l~duced by techniques comparable to those presently employed in petroleum refineries.
U.S. Patent No. 4,975,177 discloses a tw0-3tage d- ~-ng process for producing lube stocks of high V.I.
from waxy feedstocks. In the first stage of this process, the waxy feed is catalytically dewaxed by isome=rization over zeolite beta. The product of the isomerization step still contains waxy species and requires further d Y;ng to meet target pour point. The second-stage ~ ~qYi ng;
employs either solvent dewqY;n~, in which case the rejected wax may be recycled to the isomerization stage to r-Y;~mi 7e yield, or catalytic d - Ying. Catalysts which may be used in the second stage are ZSM-5, ZSN-22, ZSM-23, and ZSM-35.
To pL~se1v~ yield and V.I., the second stage d - ng catalyst should have selectivity similar to solvent d~ Y;ng. U.S. Patent 4,919,788 also teaches a two-stage dewaxing process in which a waxy feed is partially dewaxed by isomerization over a 5;1 iceon~ Y or beta catalyst with the product ~hse~ ly dewaxed to desired pour point using either solvent dewaxing or catalytic ~ ;ng.
Dewaxing catalysts with high shape selectivity, such as ZSM-22 and ZSM-23, are preferred catalysts. These examples, however, do not teach synergi3tic effects involving more than one dewaxing catalyst.
Serial No. 08/017,949 d;~cln5~ a two stage ~yd~ cking and hydroisomerlzation proc s. The first Wos6~7715 2 ~ PCT~S9~1103 stage employs a bih-n~t~onAl catalyst comprising a metal hydLuu~d~lon L on an amorphous acidic support.
The second stage, the hydroisomerization step, is carried out over zeolite beta. Snh~e~lrnt dewaxing is optional but L~ '-'. Either solvent dewaxing or catalytic dewaxing maybe used sulsr~ ly in order to obtain target V.I. and pour point. There is no tearh; ng of catalytic synergism in this invention.
In S.N. 08/017,955, petroleum wax feed i5 subjected to hydroisomerization over a noble metal-containing zeolite catalyst of low acidity. The paraffins present in the feed are selectively converted to iso-paraffins of high V.I. but lower pour point so that a final lube product of good V i ~ L iC properties is produced with a minimal degree of 15 5nh~1rnt fl nq. The process, which operates under high pL~ UL~, is well suited for upgrading waxy feeds such as slack wax with aromatic contents greater than 15 wt.% to high Viscosity Index lubricating oils with high single pass yields and limited requirement for product flrWA~i ng .
Related cases primarily emphasize solvent d~ i ng with Catalytic dewaxing as a posgible alternative or E~onnflAry step. The advantage of solvent dewaxing the product of the isomerization stage in that wax is rejected and can be recycled to the isomerization catalyst to improve the yield of high V.I. lube. However, operational costs for solvent dewaxing are higher than for catalytic dewaxing. Additionally, the pour point of the solvent dewaxed lube stock is restricted by solvent refrigeration capability to approximately -21 to -18-C. Catalytic 30 ' .. _ ' ng enables production of high V.I. lubes having pour points significantly lower than those possihlr for solvent dewaxing. An unexpected devrl~ L of the total catalytic dewaxing process is that it can produce lubricants with equivalent or higher V.I. at equivalent or lower pour points than lubricants ~Lu~uced by solvent ~r~: ~ing.

WO96~7715 2 1 9 8 2 t 3 ~ PCT~S95/11036 8nMMARY OF T~ INVENTION
The instant application involves the proco~sing of a waxy hydrocarbon feedstock using an integrated catalyst ~ystem for the production of high Viscosity Index (V.I.) low aromatic content lubricant stocks with low pour point.
The feedstock is initially contacted under high plesOu-~(hydr ~tg~n partial p~SoUL~ of at least 5617 kPa~ with low acidity large pore zeolite catalyst into which a metal, preferably a noble metal such as Pt, has been incorporated.
A substantial fraction of the waxy material in the feed is selectively isomerized over this catalyst. The reaction product is subsequently contacted with a constrained intermediate pore crystalline material, also containing a noble metal, which provides further isomerization and dewaxing. The final product is a lubricant which has a high Viscosity Index and a low pour point. A snhso~lont ~ydl~L~ating step may be included to reduce lube oil aromatic content to the desired target point.
The catalysts used in the instant invention behave synergistically. The yield and Viscosity Index (V.I.) of the product of the integrated catalyst system excced the yield and V.I. of the product from either of the two catalysts operating alone. This synergism requires the reactor containing the large pore zeolite to be operated so as to convert 40 to 90~ of the wax species in the feed.
The conversion of the residual wax is AC ~ hotl in the second d~ ; ng step. Both V.I. and yield are inversely related to pour point below a pour point of approximately 27-C. The synergy of the process is illustrated by the reduction in yield and V.I. with decreasing pour point being ~igniflcAntly less than for either ~Au~ing catalyst operating alone. The 1 ~v. ~ of yield and V.I. is not predictable by the study of each catalyst individually.
Additionally, product appearance and cloud point are 1 _~v~d by the t~ age dewaxing system over those from the selective dewaxing catalyst operating alone.
The proceOs of the instant invention can be used to upgrade feeds having low wax content, such as those .

.

WO96107715 2 1 ~ 8 2 t ~ j PCT~11~6 _ -7-obtained by solvent extracting or l.yd~L~cking vacuum distillates. ~owever, the synergy i8 most evident with feedstocks which have a wax content of over 50~.
The synergy of the integrated low-acidity large pore zeolite catalyst and the into ~ te pore catalyst permits ~ the pro~n~tion of high quality base stocks by an all-catalytic route. Such base stocks generally have a Viscosity Index greater than 120, more preferably greater than 130, and contain less than 10% aromatics, more preferably less than 1% aromatics.

CRIPTION OF ~ DRAWINGS
Figures 1, 2, 3 and 4 are plots which illustrate the synergistic relationship of the catalysts of this invention. Viscosity Indexes and yields obtained by using the catalysts together and individually are plotted against pour point. The figures are ~ ccllcced in more detail in the Examples, infra.

nF:TATT.~n DEsQl?lpTIQ~
In the present process, ~eeds with a relatively high wax content, such as slack wax, are converted to high V.I.
lubricants in an integrated process employing two catalysts with synergistic properties. A hydroisomerization process using a noble metal containing low acidity zeolite hydroi- ization catalyst is employed first. The int~ te product of this process is then contacted with a noble metal containing int~ te pore crystalline material to accomplish further del~Y;ng. Product V.I. will vary with pour point, wax content of the feed, and whether the feed was subjected to a pretreatment step. For heavy neutral slack waxes which have been hydrorefined to remove nitrogen and sulfur containing species, product VI is typically at least 140 at -18-C pour point and usually in the range 143 to 147. The production of base stocks with V.I. greater than that obtained from the synergistic catalyst system is not possible with either catalyst operating alone to effect complete d~ _ ' ng.

-Wo96/07715 2 ~ 9 ~ ~ 1 3 PCT~S95111036 ~ The present plocebses are capable of operating with a wide range of feeds of mineral oil origin to produce a range of lubricant ~Ludu~LL with good performance characteristics. Such characteristics include low pour point, low cloud point, and high Viscosity Index. The quality of the product and the yield in which it is obtained i8 dep~n~nt upon the quality of the feed and its amenability to processing by the catalysts of the instant invention. Produsts of the highest V.I. are obtained by using preferred wax feeds such as slack wax, foots oil, deoiled wax or vacuum distillates derived from waxy crudes.
Waxes produced by Fischer-~Lu~us~1- processing of synthesis gas may also be used as feedstocks. Products with lower V.I. values may also be obtained ~rom other feeds which contain a lower initial qyantity of waxy ~_ - ~ntS.
The feeds which may be used should have an initial boiling point which is no lower than the initial boiling point of the desired lubricant. A typical initial boiling point of the feed exceeds 345 C. Feeds of this type which ~may be used include vacuum gas oils as well as other high boiling fractions such as distillates from the vacuum distillation of a' ~'~ric resids, raffinates from the solvent extraction of such distillate fractions, hydLu~L~cked vacuum distillates and waxes from the solvent ~ ng of raffinates and hydLu~L~ckates.
The feed may require preparation in order to be treated satisfactorily in the hydroisomerization step. The preparation steps which are generally ~c~cc~ry are those which remove low V.I. ~ L~ such as aromatics and~
polycyclic naphthenes. Removal of these materials will result in a feed for the hydroisomerization step which contains higher quantities of waxy paraffins which are then converted to high V.I., low pour point iso-paraffins.
Catalytic synergy is most dramatically illustrated for feedstocks having a wax content of over 50~, although feeds with lower wax contents may be used effectively.
, ' wos6l077ls 2 ~ 3 ~ ~ PCT~Sg~11~6 ~ g Suitable pre-LL~ai L steps for preparing feed~ for the hydrni r ization are those which remove the aromatics and other low V.I. ~ Ls from the initial feed.
HYdLU~L~a1 ~ is an effective pL~LLeai L step, particularly at high hydrogen pLes ULeS which are effective - for ~romatics saturation e.g. 5617 kPa~ or higher. ~ild hydrocracking may also be employed as pretreatment and is preferred in the instant invention, if p.~LL~ai L is required. Example 3, infra, ~ircl-csP~ the hydLù~Lacking conditions employed in the instant invention in order to prepare a feed for the dewaxing process. Pressures over 6996 kPa,~ are preferred for l,ydLu~Lacking treatment.
~ydrocracking removes nitrogen containing and sulfur-containing species and reduces aromatics content as Table 6 below illustrates. Hydrocracking, in this example, has also slightly altered the boiling range of the feed, causing it to boil in a lower range. Commercially available catalysts such as fluoride nickel-tungsten on alumina (NiWF/Al20,) may be employed for the hydrocracking pretreatment.
The preferred gas oil and vacuum distillate feeds are those which have a high wax content, as determined by ASTM
D-3235, preferably over 50 weight percent. Feeds of this type include certain South-East Asian and r-inl~n~ China oils. Minas Gas Oil, from Tn~nPriA, is such a feed.
These feeds usually have a high paraffin content, as det~rm;nP~ by a conventional analysis for paraffins, naphthenes, and aromatics. The properties of typical feeds of this type are set out in S.N. 07/017,955.
As stated previously, the wax content of the preferred feeds is high, generally at least 50 wt% (as detprm;npd by ASTM Test D-3235) prior to pretreatment. The wax content before ~L~LL~al - L is more usually at least 60 to 80 weight percent with the balance being occluded oil comprising iso-paraffins, aromatics and naphthenics. These waxy, highly paraffinic wax stocks usually have low viscosities because of their relatively low content of aromatics and naphthenes although the high content of waxy W096~7715 2 1 9 8 ~ 1 3 rcT~S95111036 . ~ , - -lo-par~f~ins gives them melting points and pour points which render them unacceptable as lubricants without further proc~CC;ng. Wax feeds are A;ccllcc~d further in S.N.
07/017,955.
The most preferred type of wax feeds are the slack waxes, (see Table 2, infra). These are the waxy ~1UdU~L
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 primarily highly waxy paraffins (mostly n- and mono-methyl paraffins) together with occluded oil, may be used as such or it may be subjected to an initial ~oil ing step of a conventional character in order to remove the occluded oil.~ Removal of the oil results in a harder, more highly paraffinic wax which may then be used as the ~eed. The byproduct of the A~oi 1 i ng step is termed foots oil and may also be used as feed to the process. The Foots Oil contains most of the aromatics present in the original slack wax and with these aromatics, most of the heteroatoms. Slack wax and foots oil typically require ~L~L~a~lent prior to catalytic ~t Ying. The oil content of deoiled waxes may be quite low and for this purpose, mea~u~ ~ of the oil content by the t~hni ~1~ of AST~ D721 may be required for l_~Luducibility, since the D-3235 test referred to above tends to be less reliable at oil contents below 15 weight percent. At oil contents below 10 percent, however, the advantage of the present catalysts may not be as marked as with oil contents of from 10 to 50 weight percent and for this reason, wax feeds conforming to this requirement will normally be employed.
The compositions of some typical waxes are given in Table 1 below.
'~ :

.

W096~77l5 2 1 9 8 2 t ~ PCT~S9YIl036 " Table 1 "9~ C9mposition - A~ab Liqht Crude A B C
Paraffins, wt. pct. 94.2 81.8 70.551.4 Mono-naphthenes, wt. pct. 2.6 11.0 6.316.5 Poly-naphthenes, wt. pct. 2.2 3.2 7.9 9.9 Aromatics, wt. pct. 1.0 4.0 15.322.2 A typical slack wax feed has the composition shown in Table 2 below. This slack wax is obtained from the solvent ('.~EK) dewaxing of 65 cSt at 40 C neutral oil obtained from an Arab Light crude.

WO9610771S 2 1 9 8 ~ 1 3 PCT~S9S/11036 ' - 2- =

= Table 2 Slar~ WaY P~o~erties Hydrogen, wt. pct. 15.14 Sulfur, wt. pct. 0.18 Nitrogen, ppmw 11 ~elting point, ~C 57 KV at lOO-C, cSt 5.168 PNA, wt pct:
Paraffins 70.3 Naphthenes 13.6 Aromatics 16.3 Simulated Distillation:

~: C = ~

Another slack wax suitable for use in the present proceSs has the properties set out in Table 6 infra as part of Example 3. This wax is prepared by the solvent ~ew IYi ng of a heavy neutral furfural raffinate. As discussed previously, llydLu~cking may be employed to prepare the slack wax for hydroisomerization.

Hvflrocrar~;na Proce8s (O~tiûnal~
If hydLo~L~cking is employed as a pretreatment step an amorphous bifunctional catalyst i5 preferably used to promote the saturation and ring opening of the low quality aromatic ~ ~ Ls in the feed to produce hydLuuL~cked pludu~Ls which are relatively more paraffinic.
Hydrocracking i5 carried out under high pressure to favor aromatics saturation but the boiling range conversion is maintained at a relatively low level in order to minimize cracking of the saturated components of the feed and of the pIudu~Ls obtained from the saturation and ring opening of the aromatic materials. Consistent with these process objectives, the hydlug~ L~5~UL~ in the hydLuuL~cking W096107715 2 1 ~ PCT/USgSJII036 ~ --13--~tage i8 at least 5617 kPa.~ and usually is in the range of 6696 to 20786 kPa~. Normally, hydrogen partial p~=s~u~e5 of at least 10444 kPa~ are best in order to obtain a high level of aromatic saturation. Hydrogen circulation rates of at least 180 n.l.l , preferably in the range of 900 to 1800 n.l.l' are suitable.
In the hydLv~acking process, the conversion of the feed to products boiling below the lube boiling range, typically to 345'C- products is limited to no more than 50 weight percent of the feed and will usually be not more than 30 weight percent of the feed in order to maintain the desired high single pass yields which are characteristic of the process. The actual conversion is dependent on the quality of the feed with slack wax feeds requiring a lower conversion than petrolatum where it is np~c~lry to remove more low quality polycyclic ~nts. For slack wax feeds derived from the dewaxing of neutral stocks, the conversion to 345-C- products will, for all practical purposes not be greater than 10 to 20 weight percent, with 5-15 weight percent being typical for most slack waxes.
Higher conversions may be encountered with petrolatum feeds because they typically contain more low quality ~ ---nts.
With petrolatum feeds, the hydrocracking conversion will typically be in the range of 15 to 25 weight percent to produce high VI products. ~he conversion may be maintained at the desired value by control of the temperature in the hyd~ cking stage which will normally be in the range 315' to 430-C and more usually in the range of 345- to 400-C). Space velocity variations may also be used to control severity although this will be less common in practice in view of mechanical constraints on the system.
Generally, the space velocity will be in the range of 0.25 to 2 LHSV, hr. and usually in the range of 0.5 to 1.5 LHSV.
A characteristic feature of the hydl~Lacking operation is the use of a bifunctional catalyst. In general terms, these catalysts include a metal ---nt for promoting the desired aromatics saturation reactions and usually a _ _ _ _ _ , . , . , .. _ _ _ W096/07715 2 1 q 8 2 PCT~S95/11036 combination of base metals i5 used, with one metal from the iron group tGroup VIII) in combination with a metal of Group VIB. Thus, the base metal such as nickel or cobalt i5 used in combination with molybdenum or tungsten. The preferred combination i6 nickel/tungsten since it has been found to be highly effective for promoting the desired aromatics i-yd~L~cking reaction. Noble metals such as platinum or palladium may be used since they have good l~ydL~yellation activity in the absence of sulfur but they will normally not be preferred. The amounts of the metals present on the catalyst are conventional for lube hydrocracking catalysts o~ this type and generally will range from l to l0 weight percent of the Group VIII metal and l0 to 30 weigh~ percent of the Group VI metal, based on the totàl weight of the catalyst. If~a noble metal ~nt such as platinum or palladium is used instead of a base metal such as nickel or cobalt, relatively lower amounts are in order in view of the higher hydrogenation activities of these noble metals, typically from 0.5 to 5 weight percent being sufficient. The metals may be in~oL~La~ed by any suitable method including ; ~--ation onto the porous support after it is formed into particles of the desired size or by addition to a gel of the support materials prior to calcination. Addition to the gel is a preferred technigue when relatively high amounts of the metal ~ ~5 are to be added e.g. above l0 weight percent of the Group VIII metal and above 20 weight percent of the Group VI metal. These techniques are conventional in character and are employed for the production of lube hydLo~L~cking catalysts.
The metal c -~t of the catalyst is generally supported on a poroùs, amorphous metal oxide support and alumina is preferred for this purpose although silica-alumina may also be employed. Other metal oxide - ~nts may also be present in the support although their presence is less desirable. Consistent with the requirements of a lube hydL~L _king catalyst, the support should have a pore size and distribution which is adequate to permit the 2 1 9~2 1 3 WO96107715 P~/US9~11036 --lS--relatively bulky r - of the high boiling feeds to enter the interior pore sLLu~Lur~ of the catalyst where the desired l-ydLv~L~cking reactions occur. To this extent, the catalyst will normally have a minimum pore size of 50 A i . e with no less than 5 percent of the pores having a pore size less than 50 A pore size, with the majority of the pores having a pore size in the range of 50-400 A (no more than 5 percent having a pore size above 400 A), preferably with no more than 30 percent having pore sizes in the range of 200-400 A. Preferred catalysts for the first stage have atleast 60 percent of the pores in the 50-200 A range. The pore size distribution and other properties of some typical lube hydLu~L~cking (LHDC) catalysts suitable for use in the l.ydLuv.~cking are shown in Table 3 below:

Table 3 T.~nr Ca~Alvst Pro~erties Form 1.5mm cyl. 1.5 mm. tri. 1.5 mm.cyl.
Pore Volume, cc~gm0.331 0.453 0.426 Surface Area, m /gm 131 170 116 Nickel, wt. pct. 4.8 4.6 5.6 Tungsten, wt. pct. 22.3 23.8 17.25 Fluorine, wt. pct. - - 3.35 siO~Al,0, binder - - 62.3 Real Density, gm/cc4.229 4.238 4.023 Particle Density, gm/cc 1.744 1.451 1.483 Packing Density, gm/cc1.2 0.85 0.94 If n~c~aaAry in order to obtain the desired conversion, the catalyst may be promoted with fluorine, either by inaor~vLating fluorine into the catalyst during its preparation or by operating the hydLvu~cking in the pL6e_nce of a fluorine _ __ ' which is added to the feed.
Fluorine c~n~in;ng ' may be incoL~uL~Led into the catalyst by i -sy-.ation during its preparation with a suitable fluorine r __ -' such as ill~ fluoride (NH4F) or ammonium bifluoride (NH4F-HF~ of which the latter is preferred. The amount of fluorine used in catalysts which contain this element is preferably from 1 to 10 weight percent, based on the total weight of the catalyst, usually from 2 to 6 weight percent. The fluorine may be SUBSTITUTE St1EET (RULE 26) WO96/07715 2 ~ PCT~S95111036 -i6- ;
incu, uu~ ated by adding the fluorine , _ ' to a gel of the metal oxide support during the preparation of the catalyst or by im.pregnation after the particles of the catalyst have been formed by drying or ~Alcining the gel.
If the catalyst contains a relatively high amount of fluorlne as well as high amounts of the metals, as noted above, it is preferred to in~u~uLate the metals and the fluorine , JUlid lnto the metal oxide gel prior to drying and calcining the gel to form the finished catalyst particles.
The catalyst activity may also be maintained at the desired level by Ln situ fluoriding in which a fluorine compound is added to the stream which passes over the catalyst in this stage of the operation. The fluorine ~ ' may be added continuously or intermittently to the feed or, alternatively, an initial activation step may be carried out in which the fluorine ' is passed over the catalyst in the absence of the feed e.g. in a stream of hydLuy~ in order to increase the fluorine content of the catalyst prior to initiation of the actual hyd~u~acking.
situ fluoriding of the catalyst in this way is preferably carried out to induce a fluorine content of l to lO percent fluorine prior to operation, after which the fluorine can be reduced to maintenance levels sufficlent to maintain the desired activity. Suitable c -c for ir 9i~g fluoriding are orthofluorotoluene and difluoroethane.
The metals p~resent on the catalyst are preferably used in their sulfide form and to this purpose pre-sulfiding of the catalyst should be carried out prior to initiation of the 1-yd-uu.acking. Sulfiding is an established ti-i~hni~li~
and it is typically carried out by contàcting the catalyst with a sulfur-c~ntAining gas, usualiy in~the p~sence of hyd-uge-l. The mixture of 11y~Luy~n and 1~yd~uyel~ sulfide, carbon c.isulfide or a ~a~all such as bùtol mercaptan is conventional for this purpose. Presulfiding may also be carried out by contacting the catalyst with hydLuy~1 and a sulfuL--ull~aining hydrocarbon oil such as a sour kerosene or gas oil.

SU~STITUTE Sll.'ET (RULE 26) ~ , . .

WO9~07715 2 1 ~ 8 2 1 3 PCT~S95/11~36 Svner~istic Catnlvst Process The paraf~inic c _ present in the original wax feed possess good V.I. characteristics but have relatively high pour points as a result of their paraffinic nature.
The objective of the synergistic catalyst process of the lnvention is, therefore, to effect a selective conversion Or waxy species while minimi 7ing conversion of more branched species characteristic of lube components. The conversion of wax occurs preferentially by isomerization to form more br~nched species which have lower pour points and cloud points. Some degree of cracking a~ ~n i ~
isomerization and cracking is re~uired to produce very low pour point lube oils. The selectivity of the process is ~Yimi 7~ by the use of a two-catalyst system in which the first catalyst selectively converts waxy species by isomerization and the second catalyst converts the residual wax by isomerization and cracking. The pore ~LLu~LuLe of the first catalyst is significantly less restricted than that of the second allowing for the conversion of bulky wax molecules and reducing cloud point and hazy appearance below that which would be achieved with the use of the second dewaxing catalyst alone.

Hv~ro; r 7~tion Cat~lvst The catalyst used in the hydroisomerization step is one which has a high selectivity for the isomerization of waxy, linear or near linear paraffins to less waxy, isoparaffinic products. Catalysts of this type are bifunctional in character, comprising a metal ~ ~t on a large pore size, porous support of relatively low acidity. The acidity is maintained at a low level in order to reduce conversion to ~- ud~L- boiling outside the lube boiling range during this stage of the operation. In general terms, the catalyst should have an alpha value below 30 prior to metals addition, with ~efe,Led values below 20.
(See Example l) Thê alpha value is an approximate indication of the catalytic cracking activity of the catalyst compared to a SUBSTITUTE SHET iRULE 26) , _ _ _ _ _ ~ _ _ . . . . . , . _ _ _ _ _ _ _ _ WO96/07715 2 1 ~ ~ 2 ~ 3 PCT~S9~l1036 ~tandard catalyst. The alpha test gives the relative rate constant (rate of normal hexane converslon per volume Or catalyst per unit time) of the test catalyst relative to the standard catalyst which is taken as an alpha of l (Rate Constant ~ 0.016 sec l). The alpha test is described in U.S. Patent 3,354,078 and in J. Catalvsis, 4, 527 (1965);
5, 278 (1966); and 61, 395 (1980), to which reference is made for a description of the test. The experimentai conditions of the test used to determine the alpha values referred to in this specification include a constant temperature of 538-C and a variable flow rate as described in detail in J. Cat~lysis 61, 395 (1980).
The hydroisomerization catalyst comprises a large pore zeolite metal. The large pore zeolite is supported by a porous binder. Large pore zeolites usually have at least one pore channel consisting of twelve - ~red oxygen rings. Large pore zeolites usually have at least one pore channel with a major di -i~n greater than 7A. Zeolites beta, Y and mordenites are examples of large pore zeolites.
The preferred hydroisomerlzation catalyst~employs zeolite beta since this zeolite has been shown to pos6ess outstanding activity for paraffin isomerization in the presence of aromatics, as disclosed in U.S. 4,419,220. The low acidity forms of zeolite beta may be obtained by synthesis of a highly siliceous form of the zeolite e.g with a silica-alumina ratio above 500:1 or, more readily, by steaming zeolites of lower silica-alumina ratio to the requisite acidity level. They may also be obtained by extraction with acids such as dir~rh~ylic acid, as disclosed in U.S. Patent No. 5,200,168. U.S. Patent No.
5,164,169 discloses the preparation of highly siliceous zeolite beta employing a chelating agent such as tertiary alkenolamines in the synthesis mixture.
The most preferred zeolites are severely steamed and possess a fL_ ~Lk silica-alumina ratio above 200:1.
Preferably the silica-alumina ratio is above 400:1 and more preferably the silica-alumina ratio is greater than 600:1.

SU8STtTUTE SHEET (RULE 26) WO96l0771s 2 1 982 1 3 PCT~s9~/11036 The steaming conditions should be adjusted in order to attain the desired alpha value in the final catalyst and typically utilize ai - ,'~res of 100 percent steam, at t~ ~I~LULeS of from 427- to 595-C. Normally, the steaming will be carried out at t~ _ ~LUL~S above 538-C, for 12 to 120 hours, typically 96 hours, in order to obtain the desired r~dnr~ inn in acidity.
Another method is by r~pl ~r L of a portion of the r1 ..JLk aluminum of the zeolite with another trivalent element such as boron which results in a lower intrinsic level of acid activity in the zeolite. The preferred zeolites of this type are those which contain framework boron. Boron is usually added to the zeolite framework prior to the addition of other metals. In zeolites of this type, the framework consists prinrir~lly of silicon tetrahedral coordinated and inteL~ le~Led with oxygen bridges. The minor amount of an element (alumina in the case of alumino-silicate zeolite beta) is also coordinated and forms part of the LL JLk. The zeolite also contains material in the pores of the ~LLU~LU1~ although these do not form part of the LL JLh constituting the characteristic ~LLu~LuL~ of the zeolite. The term ~rL ~Lk~l boron is used here to distinguish between material in the rL JL~ of the zeolite which is evidenced by contributing ion ~Yrh~nge capacity to the zeolite, from material which is present in the pores and which has no effect on the total ion exchange capacity of the zeolite.
Zeolite beta po~s~c~ a constraint index between 0.60 and 2.0 at t- _ ~LUL_S between 316-C and 399-C although Constraint Indexes less than 1 are preferred.
Methods for preparing high silica content zeolites containing rL .L~ boron are known and are described, for example, in U.S. Patents Nos. 4,269,813. A method for preparing zeolite beta containing rL JLk boron is ~i~rlos~d in U.S. Patent No. 4,672,049. As noted there, the amount of boron contained in the zeolite may be varied by in~uL~uL~Ling different amounts of borate ion in the zeolite forming solution e.g. by the use of varying amounts SU8ST~TUTE SHEET (RULE 26) Or boric acid relative to the forces of silica and alumina.
Reference is made to these ~ lo~l~nes for a description of the methods by which these zeolites may be made.
The low acidity zeolite beta catalyst should contain at least 0.1 weight percent LL ..~L~ boron, preferably at least 0.5 weight percent boron. Boron may be added to the ~L. JL~ prior to the addition of other metals. Normally, the maximum amount of boron will be 5 weight percent of the zeolite and in most cases not more than 2 weight percent of the zeolite. The framework will normally include some alumina. The silica:alumina ratio will usually be at least 30:1, in the conditions of the zeolite as synthesized. A
preferred buLu~ b~Lituted zeolite beta catalyst is made by steaming an initial boron-containing zeolite containing at least 1 weight percent boron (as B203) to result in an ultimate alpha value no greater than 20 and preferably no greater than 10. -Pro~erties Acidity may be reduced by the introduction of nitrogen '-, e.g. NH, or organic nitrogen ~ '-, with the feed to the hydroisomerization catalyst. However, the total nitrogen content of the feed should not exceed 100 ppm and should be preferably less than 20 ppm. me catalyst may also contain metals which reduce the number of strong acid sites of the catalyst and improve the ~electivity of isomerization rPA~ti~n~ to cracking reactions. Netals which are preferred for this purpose are those belong to the class of Group IIA metals such as calcium and magnesium.
The zeolite will be composites with a matrix material to form the finished catalyst and for this purpose conventional very low-acidity matrix materials such as alumina, silica-alumina and silica are suitable although ~7n~n~o such as alpha boehmite (alpha alumina - -~ydL~te) may also be used, provided that they do not confer any ~uL~L~rlLial degree of acidic activity on the matrixed catalyst. The zeolite is usually composites with the SUBSTITUTE SHET (PsULE 26~

..

WO96/0771~ t ~ PCT~S9i~11036 -2l-matrix in amounts from 80:20 to 20:80 by weight, typically from 80:20 to 50:50 zeolite:matrix. Compositing may be done by conventional means including mulling the materials together followed by extrusion into the desired finished catalyst particles. A preferred method for extruding the zeolite with silica as a binder is disclosed in U.S.
4,582,815. If the catalyst is to be steamed in order to achieve the desired low acidity, it is performed after the catalyst has been formulated with the binder, as is conventional. The preferred binder for the steamed catalyst is alumina.
The hydroisomerization catalyst also includes a metal _, An~ in order to promote the desired hydroisomerization reactions which, proceP~irj through unsaturated transitional species, require mediation by a 1-ydLuge.,ation-dehydLugenation ~nPnt. In order to ~-Yim;~e the isomerization activity of the catalyst, metals having a strong hydLugenation function are preferred and for this reason, platinum and the other noble metals such as rhenium, gold, and palladium are given a preference.
The amount of the noble metal hydLogenation -nt is typically in the range O.l to 5 weight percent of the total catalyst, usually from O.l to 2 weight percent. The platinum may be in~uL~uLated into the catalyst by conventional terhn; Ciupq including ion exchange with complex platinum cations such as platinum tetraamine or by impregnation with solutions of soluble platinum for example, with platinum tetraammine salts such as platinum tetrAi- ;ne~hlnride. The catalyst may be subjected to a final calcination under conventional conditions in order to convert the noble metal to its reduced form and to confer the required -- An;cAl strength on the catalyst. Prior to use the catalyst may be subjected to presulfiding as described above for the hy~Luc~cking pretreatment catalyst.

SU8SlITlJTE SHEET (RULE 26) W096/07715 2 1 ~ ~ 2 ~ 3 PCT~S95/11036 -2i-Hy~roir 7~tion Conditions The conditions for the hydroisomerization step (also cnlled the isomerization step) are adjusted to achieve tne objective of isomerizing the waxy, linear and near-linear paraffinic - in the waxy feed to less waxy but high V.I. isoparaffinic materials of relatively lower pour point. This end is achieved while minimizing conversion to non-lube boiling range products (usually 345 C- materials).
Since the catalyst used for the hydroisomerization has a low acidity, conversion to lower boiling products is usually at a relatively low level;and by appropriate selection of severity, the operation of the process may be optimized for isomerization over cracking. At conventional space velocities of 1, using a Pt/zeolite beta catalyst with an alpha value below 20, temperatures for the hydroisomerization will typically be in the range of 300-to 415-C with conversion to 3is-c- typically being from 5 to 30 weight percent, more usually 10 to 25 weight percent, of the waxy feed. Approximately 40 to 90 percent of the wax in the feed is converted in the isomerization step;
However, t~ --aLuL~s may be used outside this range, for example, as low as 260-C and up to 425-C although the higher temperatures will usually not be preferred since they wili be associated with a lower isomerization selectivity and the production of less stable lube p, uduuLs as a result of the hydLu~ ation reactions being ~h- :Y~ A11Y less favored at ~uuL_ssively higher operating t~ ~LUL~S. Space velocities~will typically be in the range of 0.5 to 2 LHSV (hr. ). The pour point of the effluent from the hydroisomerization step is in the range from -1 to 43-C, preferably in the range from 5 to 39-C.
The hydroisomerization is operated at hYdLUU,~II partial PIe~-IL~S (reactor inlet) of at least 5516 KPa~., usually 5167 to 20786 kP~ and in most cases 5517 to 17339 kPaA~.
H~dLUgeII circulation rates are usually in the range of 90 to 900 n.l.l. . Since some saturation of aromatic _ Ls present in the original feed takes place in the ..

SU8STITUTE SHET (RUI F 26~

~, ~ . .

W096~7715 2 1 9 8 2 1 3 PcT~s9~11036 sencê of the noble metal hyd~uy~llation _1~ L on the catalyst, h~d~uyên i6 ~U.~ ' in the hydroisomerization even though the desired isomerization reactions are in hydLuyel- balance; for this reason, hYdLVgén circulation rates may need to be ad~usted in accuLdal-ce with the aromatic content of the feed and also with the temperature used in the hydroisomerization since higher t~ ~LuLes will be associated with a higher level of cracking and, rnnce~l~ntly~ with a higher level of olefin production, some of which will be in the lube boiling range so that product stability will need to be as6ured by saturation.
~ydrogen circulation rates of at least 180 n.l.l. will normally provide sufficient hydLugell to -ncate for the expected hydrogen ~vn~l Lion as well as lS to ensure a low rate of catalyst aging.
An interbed quench is desirable to maintain temperature in the process. Cold h~dLVY~II is generally used as the quench, but a liquid quench, usually recycled product, may also be used.

Sha~e-selective Catalvtic r~ n~ Phase The effluent from the isomerization phase still contains quantities of the more waxy straight chain, n-paraffins, together with the higher melting no1. noL~
paraffins. Because these contribute to unfavorable pour points, and because the effluent will have a pour point which is above the target pour point for the product, it is n~r~c~Ary to remove these waxy L~. To do this wlthout removing the desirable isoparaffinic - -which contribute to high V.I. in the product, a shape-selective ~ Ying catalyst is employed. This catalystremoves the n-paraffins toge~h~r with the waxy, slightly branched chain paraffins, while leaving the more branched chain iso-paraffins in the process stream. Shape-selective catalytic dewaxing processes employ catalysts which are more highly selective for removal of n-paraffins and slightly branched chain paraffins than is the isomerization catalyst, zeolite beta. This phase of the synergistic SUBSrlTUTE SHEET (RULE 26~

. .

W09~0771~ t '3 ~CT~S9~11036 -2~-process is therefore carried out as described in U.S.
Patent No. 4,919,788, to which reference is made for a description of this phase. The catalytic d _- ng step in the present process is carried out with a constrained, shape selective d~ ng catalyst based on a constrained int~ Ate pore crysfAlline~ material, such as an alumino ~l,GD~ e. A constrained int~ -'iAte crystalline material has at least one channel of 10-membered oxygen rings with any intersecting channel having 8-membered rings. ZSN-23 is the preferred zeolite for this purpose although other highly shape-selective zeolites such as ZSM-22 or the synthetic ferrierite ZSM-35 may also be used, especially with lighter stocks. Silicoaluminophosphates such as SAP0-11 and SAP0-41 maybe used as selective dewaxing catalysts.
The preferred catalysts for use as the dewlY;ng catalysts are the relatively constrained int~ -';Ate pore size zeolites. Such preferred zeolites have a Constraint Index in the range of 1-12, as det~rm i n~ by the method described in U.S. Patent No. 4,016,218. These preferred zeolites are also characterized by specific sorption properties related to their relatively constrained diffusion characteristics. These sorption characteristics are those which are set out in U.S. Patent No. 4,810,357 for the zeolites such as zeolite ZSM-22, ZSM-23, ZSM-35 and ferrierite. These zeolites have pore op~n;ngs which result in a specific combination of sorption properties, namely, (1) a ratio of sorption of n-hexane to o-xylene, on a volume percent basis, of greater than 3, wherein sorption is determin~d at a P/PO of 0.1 and at a temperature of 50-C
for n-hexane and 80-C for o-xylene and (2) by the ability of selectively cracking 3-methylpentane (3MP) in preference to the doubly branched 2,3-dimethylbutane (DN~3) at 538-C
and 1 ~ re pressure from a 1/1/1 weight ratio mixture of n-hexane/3-methyl-pentane/2,3-dimethylbutane, with the ratio of rate C~I~DLan~S k,~k~ ~t~rm;nr~ at a t~ ~tUL~
of 538-C being in excess of 2.

SUBSrITUTE SHEET (flULE 26 WO96/07715 2 1 q 8 2 1 3 PCT~S95111036 The expression, "P/PO", i8 accorded its ufiual ~ignifi~n~e as described in the literature, for example, in "The Dynamical Character of Adsorption" by J.H. deBoer, 2nd Edition, Oxford University Press (1968) and i8 the relative pL~_nULe defined as the ratio of the partial ~L~nnUL~ of sorbate to the vapor ~L~snuL~ of sorbate at the t~ tUL~ of sorption. The ratio of the rate constants, k3~/k=~, is det~mmin~d from 1st order kinetics, in the usual manner, by the following equation:
k r (l/Tc) ln (1/1-~) where k is the rate constant for each ~nt, T~ is the contact time and ~ is the fractional conversion of each component.
Zeolites conforming to these sorption requirements include the naturally occurring zeolite ferrierite as well as the synthetic zeolites ZSM-22, ZSM-23 and ZSM-35. These zeolites are at least partly in the acid or hydLu~en form when they are used in the present process.
The preparation and properties of zeolite ZSM-22 are described in U.S. Patent No. 4,810,357 (Chester) to which reference is made for such a description.
The synthetic zeolite ZSM-23 is described in U.S.
Patent Nos. 4,076,842 and 4,104,151 to which reference is made for a description of this zeolite, its preparation and properties.
The int~ ';Ate pore-size synthetic crystalline material designated ZSM-35 ("zeolite ZSM-35" or simply "ZSM-35"), is described in U.S. patent No. 4,~16,245, to which LefeL~ e is made for a description of this zeolite and its ~Le~aL~Lion. The synthesis of SAPO-ll is described in U.S. Patent Nos. 4,943,424 and 4,440,871. The synthesis of SAPO-41 is described in U.S. Patent No. 4,440,871.
Ferrierite is a naturally-o~uuLLing mineral, described in the literature, see, e.g., D.W. Breck, ZEOLITE MOLECULAR
SIEVES, John Wiley and Sons (1974), pages 125-127, 146, 219 and 625, to which reference is made for a description of this zeolite.

SU8STITUTE SHEET (flULE 26 Wos~077~s PCT~S95/11036 2 ~ q8~ t 3 The dewaxing catalysts used in the shape-seleCtive catalytic ' Yin~ include a metal hydL~yc--ation-dehyd~yenation - L. Although it may not be strictly ~PcD~Ary to promote the selective cracking reactions, the presence of this : _ L has been found to be desirable to promote certain isomerization reactions which contribute to the synergy of the two catalyst dewaxing system. The esellce of the metal _ - L leads to product 1 ~v. L, P~p~ciAlly VI, and stability as well as helping to retard catalyst aging. The shape-selective, catalytic d~; Yi ng is normally carried out in the presence of hydrogen under ~~s~uLe. The metal will be preferably platinum or palladium. The amount of the metal '~ nt will typically be 0.1 to 10 percent by weight. Matrix materials and binders may be employed as n~c~qry. Table 5 illustrates the properties of a ZSM-23 catalyst containing Pt.
Shape selective ~--qY;ng using the highly constrained, highly shape-selective catalysts may be carried out in the same general manner as other catalytic dewaxing processes, such as those described above for the initial isomerization phase. Conditions will therefore be of elevated t~ ~~a~u~c and p~cs~uLe with hydluyelll typically at temperatures from 250- to 500-C, more usually 300- to 450-C
and in most cases not higher than 370-C. Pressures extend up to 20786 kPa~, and more usually up to 17339 kPa~
Space velocities extend from 0.1 to 10 hr~l (1HSV), more usually 0.2 to 5 hr~'. Hydrogen circulation rates range from 500 to 1000 n.l.l.~l, and more usually 200 to 400 n.1.1.~~. Reference is made to U.S. Patent 4,919,788 for a more eytDn~d discussion of the shape-selective catalytic dewaxing step. As indicated previously, hydr ogcll may be used as an interbed quench in o=rder to provide maximum t- aLuL~ control in the reactor. Example 6 and Figure 4, infra illustrate the effectiveness of employing ZSM-23 in combination with zeolite beta in an integrated catalyst system. Pt/ZSM-23, although primarily a shape selective catalyst, adds in~r~ tal isomerization capability.
~ .
SU8STITUTE SHET (RULE 26) W096107715 2 I q 8 2 1 3 PCT~S95/11036 The degree of conversion to lower boiling species in the d ' ng stage will vary àccording to the extent of ~ - ng desired at this point, i.e. on the difference between the target pour point and the pour point of the effluent from the isomerization stage. It will also depend upon the selectivity of the shape-selective catalyst which i8 used. At lower product pour points, and with relatively less selective ~ ' ng catalysts, higher conversions and coL~ ;ngly higher hydL~ge~ u.ll~tions will be encountered. In general terms conversion to products boiling outside the lube range, e.g. 315-C-, more typically 345-C-, will be at least 5 weight percent, and in most cases at least 10 weight percent, with conversions of up to 30 weight percent being n~r~ccAry only to achieve the lowest pour points with catalysts of the re~uired selectivity. Boiling range conversion on a 345 C basis will usually be in the range of 10-25 weight percent.
After the pour point of the oil has been reduced to the desired value by selective ~ ~ing, the dewaxed oil may be subjected to LL~ai - Ls such as l-ydLuLL=ating, in order to remove color bodies and produce a lube product of the desired characteristics. Fractionation may be employed to remove light ends and to meet volatility specifications.
It is ~yaL~IL that the highly advantageous results achieved with the present process in terms of lube yield, V.I., and other product properties can be ascribed to the synergistic functioning of the two catalytic phases. In the first phase the large pore zeolite acts more preferentially than conventional dewaxing catalysts on the high le~ Ar weight waxy species in the feed, i.e. the back end of the feed, isomerizing them with minimal cracking. These high molecular weight waxy species, if not removed nearly completely in the ~ -~Ying process, contribute to high cloud point and a hazy appearance at near-ambient t~ LUL~8. Because access to the pore ~LLu~LuLe of the large pore zeolite is less restricted than the pore ~LLUCLULeS of conventional dewaxing catalysts, a large pore zeolite is not able to dewax the feed to low SU8STITUTE SHET (RULE 26~

W09Cl0171S 2 1 9 8 ~ 1 3 PCT~S9~11036 -2~-pour point (less than -12-C) without incurring eignificAnt yield and V.I. losses due to cracking of branched species.
However, zeolite beta is effective for selectively converting bulky WaY molecules when operated to convert 40 to 90%, more preferably 50% to 80%, of the wax in the feed to the L~J ~ La~ ' ng proces5. The pour point of the product exiting the isomPrization step, on an approximate 345-C+ basis, will depend on thç nature of the feedstock but is typically between 5-C anq 32 C. The int~ ~;Ate pore size catalysts arç, by contrast, more effective at removing the waxes in the front end (low boiling - ~nts) of the feed. As Example 6 and Figure 4 infra illustrate, intP 'iAte pore size molecular sieves such as Pt/Z5M-23 possPqep~ in~L~ Lal isomerization capabilities in addition to shape-selective dewaxing capabilities.
Thus, by applying these properties of the intP 'iAte pore size molecular sieves in combination with the properties of a large pore zeolites as described above, it has become possible to evolve a synergistic catalytic dewaxing process which makes the most effective use of the two types of zeolites. A large pore zeolite is used in an initial stage to convert waxy paraffins to less waxy iso-paraffins by isomerization, acting preferentially on the waxy ~ .~nts in the back end of the feed. The partly dewaxed feed is then p~u~-e~sed over an int~ -';Ate pore size zeolite to convert the residual waxy _ LS SO that the final product has a low pour point and low cloud point.

Products The products from the process are high V.I., low pour point, and low cloud point materials which are obtained in ~Y~ pnt yield. Besides having excellent vie~ LL1C
properties they are also highly stable, both oxidatively and ~hPrr-lly. They are also stable when eYposed to ultraviolet light. V.I. values in the range of 130 to 150 are typically obtained with the preferred wax feeds to the process. Values of at least 140 at-18-C pour point, are readily achievable, with product yields at -18-C pour point SUBSTITUTE SHET (RULE 26) WO96/0771~ 3 PCT~S9~ 036 -2g-of at least 50 weight percent, usually at least 60 weight percent, based on the original wax feed. The isomerization of the paraffins to iso-paraffins with high VI values at low pour points permits the production of lube products with a unique combination of low pour point and VI.
Typically the current ~Ludu~Ls have a VI in the range of 130-150 at -18-C pour and a VI of l20-145 at --40-C pour point.

FYAmnleS
The following examples are given in order to illustrate various aspects of the present process and are not to be considered limiting. Examples 1 and 2, directly following, illustrate the preparation of a low acidity Pt/zeolite beta catalyst and Pt/ZSM-23 catalyst, respectively.

r le l Zeolite beta with a bulk siOJAl2O3 ratio of 40 was bound in a 65% zeolite formulation using Hisil 233 precipitated silica and LUDOX HS-40 sodium-stabilized colloidal silica. The mixture was extruded using a 3~ NaOH
solution to form l/16" quadrulobe ~LLudates. The catalyst was calcined in a nitrogen ai '-re at 482 C for 3 hours and then in air at 538-C for an additional 6 hours.
Following calcination, the extrudates were treated with 2M
oxalic acid for 6 hours at 71-C. After acid extraction, the catalyst was c~lr;n~d in air at 538-C Platinum was added to the catalyst by ion exchange using Pt(NH3)~Cl2.
Following platinum addition, the catalyst was dried and c~lr-in~d in air at 349-C for 3 hours. Properties of the catalyst are given in Table 4.

SU8STITUTE SHEET (RULE 26) W096t077~5 2-1 9 8 2 1 3 PCT~S95111036 T~ble 4 Pro~erties of Low-Acidity Zeolite Beta Platinum, wt% 0.6 Sodium, ppm 245 Al20" wt~ 0-4 Surface Area, m2/g 316 Pore volume, cc/g 0.978 Alpha (before Pt addition) 8 ~~~~ le 2 A ZSM-23 zeolite with a bulk SiO2/Al20~ ratio of 120 was extruded with Versal alumina into 1/16" cylindrical extrudates. Following extrusion~the material was calcined in a nitrogen atmosphere at 538 C for 3 hours, then cooled to ambient temperature. It was then ; -n;nm exchanged to lS reduce the sodium level, air calcined at 538-C for 6 hours, then steamed at 482-C for 4 hours. After steaming, the catalyst was cooled down to ambient temperature and then platinum was added to the catalyst by ion ~Yrh~nqe with Pt(NH3)~Clz. Following Pt addition, the catalyst was dried and c~lr;n~d in air at 349-C for 3 hours. Properties of the catalyst are given by Table 5.

-~ TabLe 5 Properties of Pt/ZSM-23 Platinum, wt~ 0.2 Sodium, ppm 92 Surface Area, m2/g 242 Pore Volume, cc/g 1.119 ~lpha (before Pt addition) 31 ~Y~le 3 A slack wax obtained by solvent dewaxing a heavy neutral furfural raffinate (HNSW) was pletL~ated by LydLo~L~cking at low boiling range conversion (9%

SU~STITUTE S!1EET (RULE 26) 2 1 982 t 3 WO96/07715 PCT~Ss~11036 conversion to 345-C or below) using a commercially available ~luorided-NiW/Al2O~ catalyst. HydLu~L~king slack waxes serves to lower the nitrogen content of the wax and to upgrade the occluded oil in the wax to higher V.I.
, Ls. Conditions for the 1.ydLo~L~cking were: 1 LHSV, 393~C, 8375 kPa~, 712 n.l.l.~l circulation. Properties of the slack wax and mildly 1.ydL~L~cked slack wax are given by Table 6.

SUBSTITUTE Sl IEET (RULE 26) WO96/07715 2 1 q 8 2 1 3 PCT~S95111036 Table 6 Properties of Hcavy Neutral Slack wax and Mildly HydL~r~cked Slack Wax Hydrocracked Slack pT Iy ,~1 A~k Wax API Gravity 36.0 37.2 Nitrogen, ppm 20 <5 Sulfur, ppm 1000 <5 XV at lOO-C, cSt 7.1 Wax Content, % 66 55 (on 345-C+ basis) Com~osition. %
Paraffins 55 MnTln~Aphthenes 13 Polynaphthenes 20 Aromatics 12 S,i Tn Dist. ~C

5% Off 429 314 10% 442 391 50% 491 477 90% 544 535 r le 4 Approximately 70 cc of the Pt/zeolite beta catalyst of Example 1 and the Pt/ZSM-23 catalyst of Example 2 were loaded into two separate reactors. Zeolite beta was loaded into the first reactor and ZS~-23 was loaded in to the second reactor. The mildly hydLu~L~cked slack wax of Example 3 was fed to the first reactor containing zeolite beta with hydl~yen in c~n~uLL~IlL downward flow. The total effluent from the first reactor was bypassed around the second reactor. Conditions for the experiment were:

~HSV, hr~l: 1.0 H~, n.l.l.~l: 712 n.l.l.~
Pressure: 13891 kPa~

The total liquid product from the reaction process was analyzed by simulated distillation and then distilled to a nominal 345-C+ cutpoint. The distilled boltoms were analyzed for viscosity, pour point. Figure 1 illustrates how VI varies with pour point for Pt/zeolite beta, if used SUB~ITUTE SHET ~RUI~ 26~

_ _ _ _ _ , _ =: _ _ _ _ = _ _ _ W096/07715 21 98 21 3 PCT~S95/11036 alone. Figures 3 shows how V.I. yield varies, respectively, with decreasing pour point of the distilled bottoms. Lube yield is based on the HNSW (heavy neutral slack wax) feed to the mild hydLu~L~cking pleLL~ai 5 step.
Several of the liquid products produced from these experiments were solvent dewaxed to -18-C pour. The relation~hir between solvent dewaxed lube yield and wax conversion is shown by Figure 4. Wax conversion i6 defined by:

Wax Content of Feed - Wax Content of Reaction Product Wax Conversion =
Wax Content of ~eed Low acidity Pt/zeolite beta is an effective isomerization catalyst converting wax to lube with mineral cracking to light products up to a wax conversion of 55-60%. When wax conversion increases above 80%, isomerized paraffins, which have ready access to the Pt/zeolite beta pore structure crack more rapidly than they can be formed by isomerizing the I~ ininq wax. The result is that yield decreases rapidly with further increases in conversion.

Exa~mE~ e 5 The mildly hydLu~Lacked slack wax of Example 3 was bypassed around the first reactor and fed to the second reactor containing Pt/ZSM-23. Process conditions were identical to those of Example 4. The total liquid product was treated as in Example 4. Variation of V.I. and yield with bottoms pour point are shown by Figures 1 and 3 respectively.
Flgure 1 shows that for isomerization/dewaxing over either Pt/zeolite beta or Pt/ZSM-23, V.I. drops sharply with decreasing pour point. The slopes of the curves depicting the variation of V.I. with pour point are similar at a given pour point when the reaction occurs over SU8STITUTE SHEET (RULE 26~

_ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ W0961077l5 2 1 9 8 2 ~ i PCT~S95/11036 Pt/zeolite beta or Pt/ZSM-23 alone. Despite V.I. being approximately 5-6 numbers higher for Pt/ZSM-23 than for Pt/zeolite beta at a given pour point, it is not poc~;h~e to produce a lubricant stock having a V.I. greater than 135 with the use of either Pt/zeolite beta or Pt/ZSM-23 alone to dewax the lube to a -12-C pour point. The production of 135+ V.I. base stocks with either of these catalysts operating alone requires operation of the catalyst to achieve wax conversion typically less than 85~ with the residual wax being removed from the product by solvent Y; ng.

~1le 6 The mildly hydrocracked slack wax of Example 3 was fed to the Pt/zeolite beta reactor and the effluent from the Pt/zeolite beta passed over the Pt/ZSM-23. Both reactors operated at the conditions of Example 4 (1 L~SV over each reactor~. The zeolite beta was operated at 322-c to convert approximately 70% of the wax in the mildly hydLu~L~cked waxy feed where wax conversion is defined by the equation in Example 4.
A sample of the product from the first reactor was distilled with the 345-C bottoms found to have a pour point of 30-C. The total effluent from the first reactor was rA~r~d to the Pt/ZSM-23 reactor and t~ ~ ~LUL~ varied in the second reactor to effect changes in product pour point.
Variation of V.I. and yield with bottoms pour point are compared to the variations obtained by operating the catalysts individually by Figures 2 and 3 respectively.
Operating the Pt/zeolite beta to a distilled bottoms pour point of 30-C and removing the residual wax with Pt/ZSM-23 results in a lubricant having a VI which is less sensitive to pour point variation than a lubricant pLuduced by either catalyst operating alone, as shown by Figure 2.
The inteqrated, synergistic catalyst system allows production of 135+ V.I. lubricants at -12-C pour for which either catalyst operating alone does not.
. . . :

SU8STITUTE SliEET (RULE 2~) ,i W096/07715 2 1 9 8 2 1 3 PCT~S9S/11036 The relatively shallow slope also implies that very low pour points can be achieved without incurring a ~Dt~l~tial V.I. penalty.
The integrated catalyst system also offers ~iqn;f~c~nt yield benefit over either catalyst operating alone (Figure 3). The shallow slopes of the branch emanating from the Pt/zeolite beta curve where Pt/zeolite beta is operating at 322-C, implies that very low pour points can be achieved without substantial yield penalty by the synergistic catalyst system.
The synergy of the system reflects the difference in shape selectivities of the two catalysts, and their ability to isomerize waxes. The incremental isomerization capability of Pt/ZSM-23 is illustrated by Figure 4 which shows solvent dewaxed oil lube as a function of wax conversion for products generated by these experiments having a pour point above -12-C. Above 75% wax conversion, dewaxed oil yield decreases for Pt/zeolite beta operating alone. However, using Pt/ZSM-23 to dewax the Pt/zeolite beta effluent results in an increase in solvent dewaxed lube yield implying that Pt/ZSM-23 adds ir.~L~
isomerization ability. In addition to converting some waxy species to lube, Pt/ZSM-23 has sufficient shape selectivity to prevent most of the isoparaffins formed over Pt/zeolite beta from cracking and reducing lube yield.

Example 7 The mildly l.ydL~L~cked slack wax of Example 3 was fed to the Pt/zeolite beta reactor at the conditions of Example 4. The Pt/zeolite beta reactor was operated at 329-C to achieve approximately 88% wax conversion with wax conversion being defined in Example 4. A sample of the product from the first reactor was distilled and the 345-C
bottoms found to have a pour point of 16-C. The total effluent from the first reactor was fed to the Pt/ZSM-23 reactor and temperature varied in the second reactor to effect changes in product pour point. Variation of V.I.
and yield with bottoms pour point are shown by Figures 2 SU8STITUTE SHEET (flULE 26) WOsC/o77l5 ~ 3 PCT~S95/11036 and 3 respectively. Lube yield is based on heavy neutral slack wax fed to the 1Iyd~ cking reactor.
Similar to Example 6, the slopes of the VI and lube yield curves with pour point are ~ign;f;c~ntly shallower than for either catalyst operating alone. This ~uyy~
that the synergy of the dual catalyst system exists for a range of Pt~zeolite beta operating conditions. Figure 3 shows that yield at low pour point, e.g. less than -12-C, is highest for the two-catalyst system. Neither catalyst operating alone gives a yield PY~ ;ng 55% while the two examples of the two-catalyst system each gave ylelds at -12-C pour of at least 60%.
Table 7 shows a yield and V.I. co~parison for Examples 4 through 7 for a lubricant of lO-F PouF point.

Table 7 Comparison of Synergistic Catalyst System Selectivity with Stand-alone Catalystss~

Conditions: 1 LHSV Over Each Reactor, 1389 kPa~, 712 n.l.l.~l 2 o At -12~C Pour Point - PVzeolite// PVzeolite/
PVzeolite j beta beta /betaPt/ZSM-23 Pt/ZSM-23 P~ZSM-23 Exarnple 4 5 6 7 PV,~ Temp,~C 3i1 - 322 329 PVZSM-23 Temp,CC - 350 329 a32 345 ~C+ Product V.l. 121 133 142 135 Yield, ~/O HNSW 38 53 iO 60 (1)1~ uldl~1 and e~dlc4~oldteld from Figures 1 and 2 SUBSTITUTE SHEET (RULE 26) WO96/0771~ 21 98?~3 PCT~59~11036 E le 8 The mildly h~1LU~L _hed slack wax o~ Example 3 was plucessed over Pt/zeolite beta at the conditions of Example 4 to achieve approximately 82% wax conversion. The total reactor e~fluent was ~u~essed over Pt/ZS~-23 at a te~mperature o~ 346-C. The reaction product was distilled to a normal 345-C cutpoint. The distilled bottoms had the following properties:
' SUBSTITUTE SHEET (RULE 26) W096/07~15 2 1 9 ~ 2 t ~ PCT~S95/11036 Table 8 Pro~erties of Distilled Bottoms Viscosity, Rinematic at lOO-C, cSt 5.20 V.I., Viscosity Index 132 Pour Point, ~C ~37 Cloud Point, ~C -24 Simul~ted Di5tillation C
Initial Boiling Point 304 5~ Off 334 10% 356 50% 447 90% 516 Final 80iling Point 564 Aromatics (by W), % <1 This example shows that the integrated Pt/zeolite beta/Pt/ZSM-23 catalyst system i5 capable of producing base stocks with viscosity indices ~Y~e~;ng 135 at very low pour points. The superior cloud point of -24 C reflects the benefit of proc~ccing the feed over zeolite beta prior to ZSM-23. Zeolite beta, because of its less constrained pore nature, has the ability to convert large waxy molecules which often lead to high pour/cloud differentials. Int~ te pore zeolites, such as ZSM-23, have more difficulty converting high moLecular weight waxes fre~uently leading to low pour point base stocks with relatively high cloud points.
W absorptivity meaauL~ Ls show the benefit of high ~LeS~ULe for producing high V.I., low aromatics base stocks.

SURSTITUTE SHEET (RULE 26) WO96/07715 2 1 982 1 ~ pCT~S95111036 r le 9 A heavy ~ L~L~ d vacuum distillate having the properties below was dewaxed by Pt/ZSN-23 operating alone and by the Pt/zeolite beta // Pt/ZSM-23 catalytic d Y; ng gystem.
API Gravity 30.3 Viscosity, KV at lOO-C, cSt 9.90 Pour Point, ~C 49 Sulfur, ppm <20 Nitrogen, ppm 2 Wax Content, ~ 15 Sim Distillation, ~C

5~ Off 385 10% 399 50~ 485 90% 564 The data, tabulated below, show a slight synergy for the combination catalyst system for low wax content feeds in that yield is at least equivalent and sometimes slightly higher at constant pour point. The less restrictive nature of the Pt/zeolite beta catalyst enables some incremental conversion of high boiling waxes leading to lower cloud points for the combination catalyst system. This is an SUBSTITUTE SltEEI (RULE 26) W096/0771~ 2 1 98~ 1 ~ PCTN89~11036 -io- ~
~r~ri~lly critic~l benefit since highly shape selective d - ' ng catalysts cAn give hazy products with high cloud points when d-. Y; ng heavy feeds.

Catalvst PTIZSM-23 PVzeolite beta//

Pour Point d 345~C+ Fraction A1tor Pt/zeolite beta Dewaxin~,~C 18 345 C+ Frartion Pour Point, ~C -21 -26 -37 -15 -23 -29-37 Cloud Point, ~C 3 -2 -9 1 -8 -9 -14 Dmorence Cloud/Pour, C~ 24 24 28 16 15 20 23 Yield, wt% 94 92 88 94 92 91 90 Vl 107 104 103 -104 104 103 r le lO
A 650 SUS heavy neutral slack wax was hydLu~-~cked and stripped to remove ammonia and HzS. A material having the following properties was pl~du~ed.
API Gravity 37.4 Sulfur, ppm 2 Nitrogen, ppm <2 Oil Content on 650 F+ Fraction, ~C >49 Sim Dist, ~C
IBP/5% 125/255 10%/20% 330/434 50%/80% 497/S27 90%/FBP 538/S66 This LydLo~L~cked material was dewaxed to very low pour point over the Pt/ZSN-23 catalyst of Example 2. It was also dewaxed to very low pour point with the Pt/zeolite beta // Pt/ZSN-23 catalyst ~ystem where the Pt/zeolite beta temperature was maintained to convert 6S% of the wax in the l.ydL~L~cked feed. Wax conversion is defined in Example 4.

SUBSTITIJTE SHEET (RULE 2~) WO96/07715 PCT~S95111036 2 1 q~t ~

The Pt/ZSN-23 catalyst used in the dual catalyst system was the same as that used in Fxample 2.
The Pt/zeolite beta was prepared by extruding beta zeolite with Versal 250 psel~Ar'-o-~ ite alumina to form 1/16" ~LLudate. The extrudate was dried and cAlc;nPd in nitrogen for 3 hours at 482-C, then cAl~inpd in air at 1000 for 6 hours. Following calcination, the extrudate was steamed in 100% steam at 549-C for 96 hours. Platinum was incoL~oL~ted on the extrudate by ion PY~hAn~e with an aqueous solution of platinum tetraamine chloride to achieve a loading of 0.6 wt%. ~he cataiyst was then calcined in air at 349-C for 3 hours.
The dewaxed products were distilled to a nominal 345-C+
cutpoint and the pour point and cloud points were measured to be:

SU8STITUTE SHET (flULE 26~

W096/0771~ 2 I q 8 2 1 3 PCTNS95/11036 -~2-- Pt/zeolite beta//
C~ ~-V;aa Catalvsts Pt/~SM-23 PtlZSM-23 Wa~ Conversion Over PVB, ~/0 - 65 Pour Point of 650~F+
Fraction After Pt/B
Dewaxing, ~C - 29 Dewaxed Lube Pour Point, ~C -37 -43 Cloud Point, ~C -7 -34 o Sim Dist., ~C
IBP/5%/10% 300/300/353 313/341/361 This example shows that the incre~ental conversion of high pour point waxes over Pt/zeolite beta leads to low product cloud point. Pt/ZSM-23~ because of its less accessible ~Lru~Lu~ is not as effective at converting waxy species thLuu~h~uL the feed boiling range thus leading to a relatively high cloud points.

SU~STITUTE SHET (RllLE 26)

Claims (38)

WHAT IS CLAIMED IS:

1. A process for producing a high Viscosity Index (VI) lubricant having a VI of at least 120 from a waxy hydrocarbon feed having a wax content of at least 30 wt%, the process employing two catalysts operating synergistically, and comprising the following steps:
(a) catalytically dewaxing waxy paraffins present in the feed primarily by isomerization, in the presence of hydrogen and in the presence of a low acidity large pore zeolite isomerization catalyst, the catalyst having an alpha value of not more than 30 and containing a noble metal hydrogenation component;
(b) subjecting the effluent of the initial catalytic dewaxing step to a second catalytic dewaxing step in which the effluent is contacted with a constrained intermediate pore crystalline material, which contains a metal hydrogenation dehydrogenation component.

2. The process of claim 1 wherein the large pore zeolite of step (a) possesses at least one pore channel of 12-membered oxygen rings.

3. The process of claim 1, wherein the large pore zeolite of step (a) possesses a Constraint Index less than 1.

4. The process of claim 1, wherein the large pore zeolite of step (a) is zeolite beta.

5. A process of claim 1 in which the isomerization catalyst is a zeolite beta isomerization catalyst having an alpha value of not greater than 20.

6. The process of claim 5, wherein in which the isomerization catalyst is a low acidity zeolite beta which has been severely steamed, having a framework silica:alumina ratio of at least 200:1.

7. The process of claim 6, in which the isomerization catalyst comprises from 0.3 to 2 wt% Pt on a support comprising zeolite beta.

8. A process of claim 1, wherein the constrained intermediate pore crystalline material of step (b) possesses one channel of 10-membered oxygen rings, with any channel intersecting the channel of 10-membered oxygen rings being composed of 8 membered oxygen rings.

9. The process of claim 1 in which the catalyst of the second catalytic dewaxing step is selected from the group consisting of ZSM-22, ZSM-23, ZSM-35, SAPO-11 and SAPO-41.

10. The process of claim 1 in which the catalyst of the second catalytic dewaxing step is an intermediate pore crystalline material having specific characteristics defined by:
(1) a ratio of sorption of n-hexane to o-xylene, on a volume percent basis, of greater than 3, which sorption is determined at a P/Po of 0.1 and at a temperature of 50°C
for n-hexane and 80°C for o-xylene and (2) by the ability of selectively cracking 3-methylpentane in preference to 2,3-dimethylbutane at 538°C and 1 atmosphere pressure from a 1/1/1 weight ratio mixture of n-hexane/3-methylpentane/2,3-dimethylbutane mixture with the ratio of rate constants k3MP/kDMS being in excess of 2.

11. The process of claim 1, in which the metal hydrogenation-dehydrogenation component of the catalyst of the second dewaxing step is either Pt or Pd.

12. A process of claim 1 in which the feed comprises a waxy hydrocarbon feed having a wax content of at least 50 wt% and an aromatic content of less than 25 wt%.

13. The process of claim 1 wherein the feedstock is selected from the group consisting of a slack wax, deoiled wax, wax from Fischer-Tropsch processes, foots oils, petrolatum, vacuum gas oil, or a raffinate from solvent extraction of a vacuum distillate.

14. The process of claim 1, in which the isomerization step is carried out in the presence of dydrogen to convert from 40 to 90 wt% of the wax contained in the feed to the isomerization step.

15. The process of claim 14, in which the wax conversion during the isomerization step is from 50 to 80 wt% based on the feed to the isomerization step.

16. The process of claim 1, wherein the effluent from the isomerization step has a pour point which ranges from -1°C
to 43°C.

17. The process of claim 1 in which the isomerization step is carried out at hydrogen partial pressure ranging from a temperature from 288° to 427°C.

18. A process of claim 1, wherein the preferred range of VI is from 130 to 150.

19. The process of claim 1, in which the dewaxed effluent of step (b) is hydrotreated by contacting it with a catalyst comprising a metal hydrogenation component on an amorphous, porous support material at a pressure in the range from 3549 kPabs to 20786 kPaabs, a reaction temperature in the range from 260°C to 427°C, a space velocity which is in a range from 0.1 to 10 LHSV, and a once-through hydrogen circulation rate which extends from 178 n.l.l.-1 to 1780 n.l.l.-1, in order to improve the thermal and oxidative stability of the lubricant.

20. A process for producing a high Viscosity Index (VI) lubricant having a VI of at least 120 from a waxy hydrocarbon feed having a wax content of at least 30 wt%, the process employing two catalysts operating synergistically, and comprising the following steps:
(a) hydrocracking of the feed in order to reduce its nitrogen content as well as to remove naphthenic and aromatic components, thereby improving VI, the hydrocracking process comprising contacting the feed with a catalyst composed of a metal hydrogenation component on an acidic support;
(b) catalytically dewaxing waxy paraffins present in the feed primarily by isomerization, in the presence of hydrogen and in the presence of a low acidity large pore zeolite isomerization catalyst, the catalyst having an alpha value of not more than 30 and containing a noble metal hydrogenation component;
(c) subjecting the effluent of the initial catalytic dewaxing step to a second catalytic dewaxing step in which the effluent is contacted with a constrained intermediate pore crystalline material, which contains a metal hydrogenation dehydrogenation component.

21. The process of claim 20 wherein the large pore zeolite of step (a) possesses at least one pore channel of 12-membered oxygen rings.

22. The process of claim 20, wherein the large pore zeolite of step (a) possesses a Constraint Index less than 1.

23. The process of claim 20, wherein the large pore zeolite of step (a) is zeolite beta.

24. A process of claim 20 in which the isomerization catalyst is a zeolite beta isomerization catalyst having an alpha value of not greater than 20.

25. The process of claim 24, wherein in which the isomerization catalyst is a low acidity zeolite beta which has been severely steamed, having a framework silica:alumina ratio of at least 200:1.

26. The process of claim 20, in which the isomerization catalyst comprises from 0.3 to 2 wt% Pt on a support comprising zeolite beta.

27. A process of claim 20, wherein the constrained intermediate pore crystalline material of step (b) possesses one channel of 10-membered oxygen rings, with any channel intersecting the channel of 10-membered oxygen rings being composed of 8 membered oxygen rings.

28. The process of claim 20 in which the catalyst of the second catalytic dewaxing step is selected from the group consisting of ZSM-22, ZSM-23, ZSM-35, SAPO-11 and SAPO-41.

29. The process of claim 20 in which the catalyst of the second catalytic dewaxing step is an intermediate pore crystalline material having specific characteristics defined by:
(1) a ratio of sorption of n-hexane to o-xylene, on a volume percent basis, of greater than 3, which sorption is determined at a P/Po of 0.1 and at a temperature of 50°C
for n-hexane and 80°C for o-xylene and (2) by the ability of selectively cracking 3-methylpentane in preference to 2,3-dime-thylbutane at 1000°F and 1 atmosphere pressure from a 1/1/1 weight ratio mixture of n-hexane/3-methylpentane/2,3-dimethylbutane mixture with the ratio of rate constants k3MP/kDMB being in excess of 2.

30. The process of claim 20, in which the metal hydrogenation-dehydrogenation component of the catalyst of the second dewaxing step is either Pt or Pd.

31. A process of claim 20 in which the feed comprises a waxy hydrocarbon feed having a wax content of at least 50 wt% and an aromatic content of less than 25 wt%.

32. The process of claim 20, in which the isomerization step is carried out in the presence of hydrogen to convert from 40 to 90 wt% of the wax contained in the feed to the isomerization step.

33. The process of claim 20 wherein the feedstock is selected from the group consisting of a slack wax, deoiled wax, wax from Fischer-Tropsch processes, foots oils, petrolatum, vacuum gas oil, or a raffinate from solvent extraction of a vacuum distillate.

34. The process of claim 32, in which the wax conversion during the isomerization step is from 50 to 80 wt% based on the feed to the isomerization step.

35. The process of claim 20, wherein the effluent from the isomerization step has a pour point which ranges from -1 to 43°C.

36. The process of claim 20 in which the isomerization step is carried out at hydrogen partial pressure ranging from 5617 to 17,339 kPaabs and at a temperature from 288°C
to 427°C.

37. A process of claim 20, wherein the preferred range of VI is from 130 to 150.

38. The process of claim 20, in which the dewaxed effluent of step (b) is hydrotreated by contacting it with a catalyst comprising a metal hydrogenation component on an, amorphous, porous support material at a pressure in the range from 3549 kPaabs to 20786 kPaabs, a reaction temperature in the range from 500°F to 427°C, a space velocity which is in a range from 0.1 to 10 LHSV, and a once-through circulation rate which extends from 178 n.1.1.-1 to 1780 n.1.1.-1, in order to improve the thermal and oxidative stability of the lubricant.