EP2087076B1

EP2087076B1 - Formulated lubricants meeting 0w and 5w low temperature performance specifications made from a mixture of base stocks obtained by different final wax processing routes

Info

Publication number: EP2087076B1
Application number: EP07861516.8A
Authority: EP
Inventors: Charles L. Baker; James W. Gleeson; Lisa I. Yeh; Kim Elizabeth Fyfe
Original assignee: ExxonMobil Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 2006-10-27
Filing date: 2007-10-26
Publication date: 2016-07-20
Anticipated expiration: 2027-10-26
Also published as: WO2008057250A2; JP2010507720A; WO2008057250A3; KR20090074269A; CA2667224A1; EP2087076A2; US20080110797A1

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to a method for formulating lubricant oils meeting SAE 0W-X and/or 5W-X specifications, made from a base oil comprising a mixture of base stocks.

DESCRIPTION OF THE RELATED ART

Formulated lubricants comprise a mixture of a base stock or a base oil and at least one performance additive. Usually, the base stock is a single oil secured from a single crude source and subjected to a single processing scheme and meeting a particular specification. Mixtures of base stocks of different specifications produce a base oil. Crude oil is typically subjected initially to a dewatering/demetalling step followed by atmospheric distillation to yield various fractions, the heavier fraction being subjected typically to vacuum distillation with the heavier fractions from such vacuum pipe still being subjected to extraction to remove aromatics, hydrocracking, hydrofinishing and dewaxing to produce a suitable fraction boiling in the desirable lubricating oil boiling range. The oil boiling in the lubricating oil (hereinafter lube oil) boiling range is subsequently separated into various fractions of different viscosity for use as base stocks. The dewaxing can take the form of solvent dewaxing wherein the waxy lube oil is subjected to cooling using various solvents such as methylethyl ketone/methylisobutyl ketone, (MEK/MIBK), MEK/toluene, liquefied propane or butane, etc., to decrease the wax content of the oil and by so doing lower the pour point of the oil. Solvent dewaxing constitutes the physical removal of the wax using a solvent such as methyl ethyl ketone/methyl isobutyl ketone or an autorefrigerative solvent resulting in the recovery of a reduced wax content stream and a separate wax stream known as slack wax. Dewaxing can also be accomplished catalytically. In catalytic dewaxing the waxy feed is contacted with a dewaxing catalyst in the presence of hydrogen at elevated temperature. The wax content of the oil is reduced either by conversion of the wax molecules, which are typically long chain normal or long chain slightly branched paraffin, into short chain paraffin, or by the rearrangement of the atoms in the wax molecule, i.e., conversion of n-paraffin or slightly branched paraffin into more heavily branched paraffin, a process known as isomerization. Catalytic dewaxing changes the nature of the molecules present in the oil either by cracking or rearrangement and clearly results in the production of a dewaxed oil which is compositionally different than that obtained by solvent dewaxing.
For the sake of convenience lube oil base oil, produced by blending different base stock, usually employ different base stocks produced in a single plant. Thus, a lube oil blending plant will use as its base stock slate the base stock secured from its associated refinery and, therefore, all of the base stocks or base stock mixtures, i.e., base oils used to produce formulated oil in the lube oil blending plant will have been treated in generally the same manner including crude pretreatment, distillation, hydroprocessing (if any) and dewaxing, be it solvent dewaxing or catalytic dewaxing. Refineries rarely house two different dewaxing schemes. Thus, a refinery which practices solvent dewaxing does not usually also practice catalytic dewaxing, and vise versa. In general, solvent and catalytic dewaxed stocks of the same or of very similar viscosity have not been mixed to produce a blended base stock.
For instance, WO 2004/081157 discloses a lubricant composition that meets the 0W-X specifications, comprising a base oil obtained by means of a catalytic dewaxing process.
US 2004/0043910 discloses a process for preparing a Fischer-Tropsch derived lubricant bsae oil by blending at least two Fischer-Tropsch derived fractions dewaxed by (hydro)isomerization, optionally combined with solvent dewaxing.
USP 4,259,170 teaches a method for manufacturing a slate of lubricant base stocks from a paraffin base stock or a mixed crude source. The heavy, high viscosity bright stock raffinate is catalytically dewaxed while the lighter lower viscosity neutral oil raffinates are solvent dewaxed. The combined use of solvent and catalytic dewaxing is described as a highly efficient method of manufacture without loss of product quality. The catalytically dewaxed bright stock can be used for blending automotive lubricating oils. As is apparent, however, the catalytically dewaxed bright stock and the solvent dewaxed lighter neutral oils are not of the same or similar viscosity.
USP 6,773,578 is directed to lube oil base stocks made by a process that involves obtaining feedstocks that have a 95% off point (T₉₅) below 621 °C (1150°F) and feed stocks that have a 95% off point (T₉₅) above 621°C (1150°F). The feed stocks that have a 95% off point below 621°C (1150°F) are catalytically dewaxed and the feed stocks that have a 95% off point above 621°C (1150°F) are solvent dewaxed. The resulting products can optionally be blended and the base stocks can be combined with various additives to form lube oil compositions. No examples are presented of any such blends, which even if they had been produced would have constituted mixtures of base stocks or base oils of different viscosities, not of the same or substantially similar viscosities.
U.S. published application 2005/0098476 is directed to a method for improving the lubricating properties of a distillate base oil characterized by a pour point of 0°C or less and a boiling range having the 10% off point (T₁₀) falling 329°C (625°F) and 421°C (790°F) and the 90% off point (T₉₀) falling between 385°C (725°F) and 510°C(950°F), the method comprising blending with said distillate base stock or base oil a sufficient amount of a pour point depressing base oil blending component to reduce the pour point of the resulting base oil blend at least 3°C below the pour point of the distillate base stock, wherein the pour point depressing base oil blending component is an isomerized Fischer-Tropsch derived base stock bottoms product having a pour point that is at least 3°C higher than the pour point of the distillate base stock.
USP 6,475,960 is directed to premium synthetic lubricants comprising a synthetic isoparaffinic hydrocarbon base stock and an effective amount of at least one performance additive. The base stock is derived from a waxy paraffinic Fischer-Tropsch (hereinafter also referred to as F-T) synthesized hydrocarbon feed. The lubricant may also contain hydrocarbonaceous and synthetic base stock materials such as mineral oils, mineral oil slack wax isomerate, PAO, and mixtures thereof. No examples of mixtures of Fischer-Tropsch wax isomerate with any mineral oil, synthetic oil or PAO are presented.
USP 5,149,452 is directed to wax isomerate oil having a reduced pour point, by using a combination of low molecular weight and high molecular weight polyalkymethacrylate pour point depressant. The preferred wax isomerate is hydroisomerized slack wax.
USP 6,332,974 is directed to wide-cut synthetic isoparaffinic lubricating oils made by hydroisomerization and then catalytic dewaxing of a waxy F-T synthesized hydrocarbon fraction feed. Formulated 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 wide cut synthetic isoparaffinic lubricating oil base stock can be used as such or mixed with other base stocks including hydrocarbonaceous base stock, synthetic base stock and mixtures thereof, hydrocarbonaceous base stocks including conventional mineral oil, shale oil tar and coal liquefaction oils, mineral oil derived slack wax, while synthetic base stocks include PAO, polyester types and other synthetics. No examples are given of the wide cut synthetic isoparaffinic lube oil mixed with any other base stock (see also USP 6,475,960 , WO 00/14187 ).
USP 6,090,758 is directed to a method for reducing foaming in lubricating oils derived from wax isomerization. In an Example a conventional SAE 10W40 multigrade oil is formulated from an isomerized slack wax base stock (EXXSYN base stock), 150 N base stock, an additive package, VI improver and 12500 cSt silicone oil.
WO 03/064570 is directed to mixed Total Base Number (TBN) detergent additive compositions for lubricating oils. In the text, examples are given of such detergent mixtures in combination with various base stocks and base oil mixtures of base stocks including hydrotreated base stocks mixed with PAO and hydrocarbyl aromatics. Examples are present only of formulations containing various combinations of hydrotreated base stock, PAO and hydrocarbyl aromatics for the production of SAE 5W30 multi-grade engine oils.
US published application 2004/0094453 is directed to a process for producing a lubricating base oil blend which comprises (a) recovering a F-T derived distillate fraction characterized by a kinematic viscosity (KV) at 100°C of about 2 cSt or greater but less than 3 cSt and (b) blending the F-T derived distillate fraction with a petroleum derived base oil selected from the group consisting of a Group I, a Group II a Group III base stock or mixture of two or more thereof to produce a lube base oil blend having a KV at 100°C of about 3 cSt or greater. The Examples are directed to 10W-X and 15W-X engine oils.
U.S. published application 2004/053030 is directed to functional fluids having low Brookfield viscosity using high viscosity-index base stocks/base oils.
It is desirable to produce multi grade engine oil composition meeting the SAE 0W-X and 5W-X multi-grade lubricating oil low temperature MRV (ASTM D4684) and CCS viscosity (ASTM D 5293) specification requirements for such 0W-X and 5W-X lube oils without the addition to such compositions of viscosity modifiers and pour point depressants or only low concentrations of viscosity modifiers and pour point depressants.

DESCRIPTION OF THE FIGURE

Figure 1 presents the results in terms of Mini Rotary Viscometric Test (ASTM D 4684) (MRV) at -35°C and Cold Crank Simulation Viscosity Text (CCS) at -30°C (ASTM D 5293) for various oils and oil blends showing that the combination of 2 base oils of similar viscosities but made by different final wax treatment process techniques (base oils A solvent dewaxed plus B catalytically dewaxed) exhibited CCS and MRV values for the blend unexpectedly superior to the CCS and MRV values exhibited for blends of base oils made using the same final wax treatment process technique (base oil A, solvent dewaxed) plus E (solvent dewaxed), or base oil D (solvent dewaxed) plus E or base oil C (solvent dewaxed) plus E).

DESCRIPTION OF THE INVENTION

The present invention is directed to a method for producing a base oil for use as the base oil in the formulation of 0W-X or 5W-X multigrade engine oils, said multi grade engine oils meeting, when formulated: a NOACK volatility of 15% or less;
according to Society of Automotive Engineers (SAE) Surface Vehicle Standard J300, a 0W-X specification of cold cranking simulator (CCS) viscosity at -35°C of 6200 cP or less and of minirotary viscometer test (MRV) at -40°C of 60,000 cP or less, or a 5W-X specification of CCS viscosity at -30°C of 6600 cP or less and of MRV at -35°C of 60,000 cP or less; and
a yield stress of less than 35 pascals;
said method comprising mixing at least two base oils wherein one base oil is solvent dewaxed using a single solvent dewaxing process technique and the second base oil is catalytically dewaxed using a single catalytic dewaxing process technique,
wherein each base oil individually making up the mixture has a kinematic viscosity at 100°C in the range of 3.5 to 7.0 mrn²/s, the mixture itself, without additive, having a kinematic viscosity at 100°C in the range of 4 to 6 mm²/s,
wherein the pour point of each base oil in the mixture without additives is -30°C or higher, preferably -20°C or higher, provided that as compared to the temperature at which the MRV is measured for each engine oil grade the difference between the pour point of the oil mixture and the temperature of measurement of the MRV of the formulated oil is at least 10°C, and
wherein the amount of catalytically dewaxed oil combined with the solvent dewaxed oil ranges from 5 to 35 wt%.
Very low ambient temperatures during the winter occur in most of northern North America and parts of Europe and Asia. Adequate lubrication of key engine parts during cold start is critical if engine damage or failure is to be avoided. An engine oil's viscosity at low temperature is critical for determining how readily the engine can be cranked, and the speed with which the oil flows from the pan to the oil pump and from there to other parts of the engine.
When an oil is used in engines operating at low ambient temperatures, the oil must have enough low temperature fluidity to allow the engine to crank and to lubricate the moving parts very quickly. Older vehicles relied upon a certain cranking speed to generate air flow through the carburetor which misted the fuel and allowed the engine to start. If the engine could not crank quickly enough, then it would not start. Fuel injection engines were introduced in the mid 1970s and by 1990, virtually all gasoline passenger car vehicles were fuel injected. Fuel injection coupled with computer controls will allow the engine to start even when the oil is too viscous to allow the engine to crank. The situation raised concerns that engine failure could occur when the engine started but the lubricant was too viscous to pump to the now-moving parts. ASTM has two tests which measure the low temperature performance of the lubricant. The cold cranking simulator viscosity (CCS) (ASTMD 5293) evaluates the lubricant's capability to allow the engine to crank at low temperature. Once the engine has cranked and started, then the oil must be able to flow rapidly to the oil pump. The test for measuring low temperature pumping ability is the mini rotary viscometer test (MRV) (ASTM D 4684). The MRV test is designed to predict the ability of the oil to reach critical moving components under low temperature starting conditions. Both good low temperature cranking viscosity and good mini rotary viscosity are required to protect engine components from damage due to lack of lubrication during low temperature starting. The SAE viscosity grade system is used to determine the low temperature usefulness of multigraded engine oils. Both the CCS viscosity and the MRV must meet the limits of the particular SAE grade designated.
The CCS viscosity and the MRV test measure different low temperature properties of the lubricant and therefore good performance in the CCS viscosity test does not necessarily predict good performance in the MRV test. The MRV performance is usually improved by the addition of low temperature flow improver. The choice of flow improver is highly dependent upon the base stock and can be very sensitive to changes in base stock wax structure. Situations arise where no consistently capable low temperature flow improver is available.
High performance specifically processed API Group II+ and Group III mineral oil base stocks set the performance standard for non-synthetic engine oils. Key to that performance is the low temperature properties enabled by the base stock as seen in the formulated lubricant MRV and CCS. The MRV and CCS viscosity are measured well below the pour point of the base oils and take advantage of the various additive chemistries used, including pour point depressants (PPD's).
Solvent dewaxed stocks are known to generally have debits in regard to low temperature properties and are defensive relative to stocks which have been catalytically dewaxed (cat dewaxed). Formulations based on cat dewaxed stocks have lower overall formulated cost than those from solvent dewaxed stocks. Different base stocks of the same final wax processing type from the same plant are generally blended to make an engine base oil and one of the base stocks usually will have superior volatility characteristics and thus bears a price premium. It has been found that cat dewaxed stocks of the same or substantially similar viscosity as the solvent dewaxed stocks (i.e., stocks having KV @ 100°C in the range of 3.5 to 7 mm²/s, preferably 4 to 7 mm²/s, more preferably 4 to 6.5 mm²/s) can be combined with solvent dewaxed base stock to replace part of the solvent dewaxed stock to yield a base oil which either itself meets the MRV and CCS viscosity target requirements for SAE 0W-X and/or 5W-X multi grade lubricating oil or which with the addition of a minor amount of pour point depressant, i.e., zero to 0.1 wt% (as received) amounts much lower than have heretofore been employed, can result in a formulated lube oil meeting the SAE 0W-X and/or 5W-X low temperature viscometric properties as measured by MRV and CCS viscosity.
Wax hydrodewaxate, hydroisomerate/cat (and/or solvent) dewaxate, and GTL stocks, defined in detail below, offer yet additional choices for base stocks made by methods which differ from either solvent dewaxing or catalytic dewaxing. Wax hydrodewaxate or hydroisomerate/cat (and/or solvent) dewaxate stocks and Gas-to-Liquids (GTL) stocks made from GTL materials are base stocks characterized by the rearrangement of the carbon atoms making up the structure of the hydrocarbon molecule. Whereas solvent dewaxing physically removes wax from oil without changing the structure of the oil and traditional catalytic dewaxing physically destroys the wax by converting it from heavy molecules to light molecule, hydrodewaxing, or hydroisomerization/cat (or solvent) dewaxing predominantly rearranges the carbon atoms in the waxy molecule converting it from a normal straight-chain or slightly branch chain structure into a branched or more branched chain structure (iso-paraffin) of the same or similar carbon number accompanied by minimal but selective catalytic dewaxing (i.e., minimal cracking/fragmentation) or minimal solvent dewaxing, producing an oil material of significantly reduced pour point.
While mixtures of solvent and catalytically dewaxed stocks have been used to produce mixed base stock useful for engine oil, such mixed stocks have not been employed to produce SAE 0W-X or 5W-X multi grade lubricating oil compositions. In the past base oils constituting mixtures of solvent dewaxed and catalytically dewaxed stock have constituted mixtures of such stocks which did not have similar kinematic viscosities at 100°C in the 3.5 to 7 mm²/s range.
It has now been discovered, however, that base stocks or base oils having KV @ 100°C in the range of 3.5 to 7 mm²/s made by different wax removal (solvent or catalytic dewaxing) techniques can be blended to produce formulated lubricating oil compositions meeting the low temperature viscometries and rheological property targets of SAE 0W-X and 5W-X multi-grade engine oils without need to resort to deeply dewaxed base oils or base oils of very low pour point, or to viscosity modifiers or pour point depressants, or with the use of very low quantities of viscosity modifiers and pour point depressants (PPD).
This is different from the expectations of those who are skilled in this art. Most low temperature properties of lubricating oils are set by the base stocks or base oils in combination with various additives. Specific additives, such as PPD's, are then selected to match the nature and amount of residual wax in order to most effectively improve low temperature properties. Different types of waxes usually mandate a change in the nature or amount of PPD, increasing cost or decreasing blending flexibility. There have been numerous examples where a base stock changes and a formulation can no longer use the same pour point depressant that was previously successful in adjusting low temperature properties. This is especially true for changes in wax processing route.
It has now been found that combining base stocks and/or base oils made employing different wax processing routes shows an unexpected improvement in low temperature properties for lower viscosity multi-grade engine oils in the SAE 0W-X and 5W-X multi grade lubricating oil range. It is believed that this is due to a synergistic behavior in the different residual waxes present in the different stocks that either eliminates the need for PPD or greatly improves the low temperature response to PPD permitting the use of less PPD.
This improvement is seen when the pour point of the mixture of base stocks and/or base oils used is well above the MRV temperatures of evaluation for the fully formulated engine oils of the different SAE grades. For example, most base oils have pour points in the range of -18°C to -30°C. The temperature of evaluation for 5W and 0W engine oils is -30°C and -35°C respectively for CCS viscosity high shear viscosity and -35°C and -40°C respectively for Mini Rotary Viscometer Test (MRV) low shear viscosity.
A difference between the pour point of the mixture of base stock(s) and or base oil(s) and the temperature of MRV evaluation for the 0W-X or 5W-X formulated oil of at least 10°C is required to take advantage of the improvement brought about by the use of such mixed base stocks produced by different final wax (removal and/or molecular rearrangement) processing routes in terms of the unexpected positive effect on low temperature viscometric and rheological properties. The stocks from different dewaxing processes will have differing kinds, and in all probability different amounts, of residual wax. It has been found that it is the mixing of these different residual wax oils that give the unexpected benefit that is the subject of the present invention, that is, the ability to produce base oils suitable for sue in the production of 0W-X and 5W-X lubricating oils from stocks which individually cannot be so employed. If instead of mixing two stocks having individual pour points at last 10°C higher than the temperature of measurement for the MRV of the different oil grades (-35°C for 5W- or -40°C for 0W-) use was made of oils having pour points meeting the MRV measurement temperature there would be too little residual wax remaining for the interaction seen in the present invention to occur. There would be too little wax remaining to make a difference. Further, the present invention discovery of unexpected suitability of higher pour point oils to make lubricating oil formulations meeting the 0W-X and 5W-X specification enlarges the pool of oils useful to produce premium formulations without the need for recourse to severe dewaxing to produce very low pour point base stock.
The base stocks and/or base oils which are combined to achieve this advantageous result are base stocks or base oils characterized each individually as having kinematic viscosities (KV) at 100°C (by ASTM D445) in the range of 3.5 to 7 mm²/s, preferably 4 to 7 mm²/s, more preferably 4.0 to 6.5 mm²/s, wherein each base stock or base oil in the blend is derived from the same or different feed stock source but processed by different final wax processing techniques or different oil synthesis techniques. The final mixture of base stocks and/or base oils, without additives, is characterized by a kinematic viscosity at 100°C in the range of 4 to 6 mm²/s.
Base stocks useful as blending components in the present invention are the API Group II, Group III, base stocks developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org). Group II base stocks are hydrocarbon base stocks which have a viscosity index of between 80 to 120, and contain less than or equal to 0.03 wt% sulfur and greater than or equal to 90 wt% saturates. Group III stocks are hydrocarbon base stocks which have a viscosity index greater than 120 and contain less than or equal to 0.03 wt% sulfur and greater than 90 wt% saturates.
Wax hydroisomerate/catalytic (and/or solvent) dewaxate, or hydrodewaxate or GTL base stocks/base oils can also be used in combination with the aforesaid dewaxed Group II and/or Group III base stocks/base oils.
A characteristic which marks each oil used before blending, however, is that each oil has a kinematic viscosity at 100°C in the range of 3.5 to 7 mm²/s, preferably 4 to 7 mn²/s, more preferably 4.0 to 6.5 mm²/s, and each base oil and the mixture of base oils has a pour point at least 10°C higher than the temperature of measurement of the MRV specification for the 0W-X or 5W-X oil formulation (MRV specification for 0W-X oil measured at -40°C, for 5W-X oil measured at - 35°C).
The oils which are blended may come from the same or different feed sources, that is, each oil can trace their origin back to the same or to different crude oil or synthesis process but each oil has been subjected to different wax processing procedures (i.e., solvent dewaxing, or catalytic dewaxing ).
Thus, a base oil pair can be derived from some particular crude oil provided each oil has been subjected to a different wax processing scheme. Each base stock or base oil in a base oil pair can further constitute a mixture of base stocks or base oil from the same or different feed source subjected to the same wax processing scheme. As used herein and in the appended claims the terms "base stock" or "base oil" is to be understood as embracing a single base stock or base oil or mixture of more than one base stock or base oil from the same or different feed source subject to the same final wax processing scheme unless indicated otherwise.
The Group II and/or Group III base oils/base stocks can be combined with non-conventional base stocks/base oils as the second oil produced by a different wax processing procedure.
Thus, the present invention embraces mixtures of base stocks or mixtures of mixtures of base stocks having KV's @ 100°C in the range of 3.5 to 7 mm²/s, preferably 4 to 7 mm²/s, more preferably 4.0 to 6.5 mm²/s as previously described, wherein one base stock or base oil or mixture of base stocks or base oils is/are solvent dewaxed using a single solvent dewaxing process technique and the second base stock or base oil or mixture of base stocks or base oils is/are catalytically dewaxed using a single catalytic dewaxing process technique.
In the present invention the amount of catalytic dewaxed oil added to solvent dewaxed oil of the same or substantially similar viscosity ranges from 5 to 35 wt%, preferably 10 to 25 wt%.
Non-conventional or unconventional base stocks and/or base oils include one or more of a mixture of base stock(s) and/or base oil(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oils derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks and/or base oils.
As used herein, the following terms have the indicated meanings:

a) "wax" - hydrocarbonaceous material having a high pour point, typically existing as a solid at room temperature, i.e., at a temperature in the range from about 15°C to 25°C, and consisting predominantly of paraffinic materials;
b) "paraffinic" material: any saturated hydrocarbons, such as alkanes. Paraffinic materials may include linear alkanes, branched alkanes (iso-paraffins), cycloalkanes (cycloparaffins; mono-ring and/or multi-ring), and branched cycloalkanes;
c) "hydroprocessing": a refining process in which a feedstock is heated with hydrogen at high temperature and under pressure, commonly in the presence of a catalyst, to remove and/or convert less desirable components and to produce an improved product;
d) "hydrotreating": a catalytic hydrogenation process that converts sulfur-and/or nitrogen-containing hydrocarbons into hydrocarbon products with reduced sulfur and/or nitrogen content, and which generates hydrogen sulfide and/or ammonia (respectively) as byproducts; similarly, oxygen containing hydrocarbons can also be reduced to hydrocarbons and water;
e) "catalytic dewaxing": a conventional catalytic process in which normal paraffins (wax) and/or waxy hydrocarbons, e.g., slightly branched iso-paraffins, are converted by cracking/fragmentation into lower molecular weight species to insure that the final oil product (base stock or base oil) has the desired product pour point;
f) "solvent dewaxing": a process whereby wax is physically removed from oil by use of a chilled solvent or an autorefrigerative solvent to solidify the wax which can then be removed from the oil;
g) "hydroisomerization" (or isomerization): a catalytic process in which normal paraffins (wax) and/or slightly branched iso-paraffins are converted by rearrangement/isomerization into branched or more branched iso-paraffins (the isomerate from such a process possibly requiring a subsequent additional wax removal step to ensure that the final oil product (base stock or base oil) has the desired product pour point);
h) "hydrocracking": a catalytic process in which hydrogenation accompanies the cracking/fragmentation of hydrocarbons, e.g., converting heavier hydrocarbons into lighter hydrocarbons, or converting aromatics and/or cycloparaffins (naphthenes) into non-cyclic branched paraffins.
i) "hydrodewaxing": (e.g., ISODEWAXING® of Chevron or MSDW™ of Exxon Mobil corporation) a very selective catalytic process which in a single step or by use of a single catalyst or catalyst mixture effects conversion of wax by isomerization/rearrangement of the n-paraffins and slightly branched isoparaffins into more heavily branched isoparaffins, the resulting product not requiring a separate conventional catalytic or solvent dewaxing step to meet the desired product pour point;
j) the terms "hydroisomerate", "isomerate", "catalytic dewaxate", and "hydrodewaxate" refer to the products produced by the respective processes, unless otherwise specifically indicated;
k) "base stock" is a single oil secured from a single feed stock source and subjected to a single processing scheme and meeting a particular specification;
l) "base oil" comprises one or more base stock(s).

Thus the term "hydroisomerization/cat dewaxing" is used to refer to catalytic processes which have the combined effect of converting normal paraffins and/or waxy hydrocarbons by rearrangement/isomerization, into more branched iso-paraffins, followed by (1) catalytic dewaxing to reduce the amount of any residual n-paraffins or slightly branched iso-paraffins present in the isomerate by cracking/fragmentation or by (2) hydrodewaxing to effect further isomerization and very selective catalytic dewaxing of the isomerate, to reduce the product pour point. When the term "(and/or solvent)", is included in the recitation, the process described involves hydroisomerization followed by solvent dewaxing (or a combination of solvent dewaxing and catalytic dewaxing) which effects the physical separation of wax from the hydroisomerate so as to reduce the product pour point.
GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds, and/or elements as feedstocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons, for example waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feedstocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range separated/fractionated from synthesized GTL materials such as for example, by distillation and subsequently subjected to a final wax processing step which is either or both of the well-known catalytic dewaxing process, or solvent dewaxing process, to produce lube oils of reduced/low pour point; synthesized wax isomerates, comprising, for example, hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed synthesized waxy hydrocarbons; hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed F-T hydrocarbons, or hydrodewaxed or hydroisomerized/cat (or solvent) dewaxed, F-T waxes, hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed synthesized waxes, or mixtures thereof.
GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed F-T material derived base stock(s) and/or base oil(s), and other hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed wax derived base stock(s) and/or base oil(s) are characterized typically as having kinematic viscosities at 100°C of from about 2 mm²/s to about 50 mm²/s, preferably from about 3 mm²/s to about 50 mm²/s, more preferably from about 3.5 mm²/s to about 30 mm²/s, as exemplified by a GTL base stock derived by the hydrodewaxing or hydroisomerization/catalytic (or solvent dewaxing) of F-T wax, which has a kinematic viscosity of about 4 mm²/s at 100°C and a viscosity index of about 130 or greater, but the GTL base stock(s) and/or base oil(s) and or other hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed wax derived base stock(s) and/or base oil(s) used in the present invention have kinematic viscosities in the range of about 3.5 mm²/s to 7 mm²/s, preferably about 4 mm²/s to about 7 mm²/s, more preferably about 4.5 mm²/s to about 6.5 mm²/ at 100°C. Preferably the wax treatment process is hydrodewaxing carried out in a process using a single hydrodewaxing catalyst. Reference herein to Kinematic viscosity refers to a measurement made by ASTM method D445.
GTL base stock(s) and/or base oil(s) derived from GTL materials, especially hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed F-T material derived base stock(s) and/or base oil(s), and other hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed wax-derived base stock(s) and/or base oil(s), which can be used as base stock and/or base oil components of this invention are further characterized typically as having pour points of about -5°C or lower, preferably about -10°C or lower, more preferably about -15°C or lower, still more preferably about -20°C or lower, and under some conditions may have advantageous pour points of about -25°C or lower, with useful pour points of -30°C to -40°C or lower. If necessary, a separate dewaxing step may be practiced to achieve the desired pour point. In the present invention, however, the GTL or other hydrodewaxed or hydroisomerized/cat (and/or solvent) dewaxed wax-derived base stock(s) and/or base oil(s) used are those having pour points of -30°C or higher, preferably -25°C or higher, more preferably -20°C or higher. References herein to pour point refer to measurement made by ASTM D97 and similar automated versions. An isomerate secured from a single hydroisomerization process technique, if divided into two fractions with one fraction being solvent dewaxed and the second fraction being catalytically dewaxed or hydrodewaxed, would be considered to be two fractions produced by different wax processing techniques.
The GTL base stock(s) and/or base oil(s) derived from GTL materials, especially hydrodewaxed or hydroisomerizedlcat (or solvent) dewaxed F-T material derived base stock(s) and/or base oil(s), and other such wax-derived base stock(s) and/or base oil(s) which can be used in this invention are also characterized typically as having viscosity indices of 80 or greater, preferably 100 or greater, and more preferably 120 or greater. Additionally, in certain particular instances, the viscosity index of these base stocks and/or base oil(s) may be preferably 130 or greater, more preferably 135 or greater, and even more preferably 140 or greater. For example, GTL base stock(s) and/or base oil(s) that derive from GTL materials preferably F-T materials especially F-T wax generally have a viscosity index of 130 or greater. References herein to viscosity index refer to ASTM method D2270.
In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained by the hydroisomerization/isodewaxing of F-T material, especially F-T wax, is essentially nil.
In a preferred embodiment, the GTL base stock(s) and/or base oil(s) comprises paraffinic materials that consist predominantly of non-cyclic isoparaffins and only minor amounts of cycloparaffins. These GTL base stock(s) and/or base oil(s) typically comprise paraffinic materials that consist of greater than 60 wt% non-cyclic isoparaffins, preferably greater than 80 wt% non-cyclic isoparaffins, more preferably greater than 85 wt% non-cyclic isoparaffins, and most preferably greater than 90 wt% non-cyclic isoparaffins.
Useful compositions of GTL base stock(s) and/or base oil(s), hydrodewaxed or hydroisomerized/cat (and/or solvent) dewaxed F-T material derived base stock(s), and wax-derived hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s), such as wax isomerates or hydrodewaxates, are recited in U.S. Pat. Nos. 6,080,301 ; 6,090,989 , and 6,165,949 for example.
Base stock(s) and/or base oil(s) derived from waxy feeds, which are also suitable for use in this invention, are paraffinic fluids of lubricating viscosity derived from hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed waxy feedstocks of mineral oil, non-mineral oil, non-petroleum, or natural source origin, e.g., feedstocks such as one or more of gas oils, slack wax, waxy fuels hydrocracker bottoms, hydrocarbon raffinates, natural waxes, hyrocrackates, thermal crackates, foots oil, wax from coal liquefaction or from shale oil, or other suitable mineral oil, non-mineral oil, non-petroleum, or natural source derived waxy materials, linear or branched hydrocarbyl compounds with carbon number of about 20 or greater, preferably about 30 or greater, and mixtures of such isomerate/isodewaxate base stock(s) and/or base oil(s).
Slack wax is the wax recovered from any waxy hydrocarbon oil including synthetic oil such as F-T waxy oil or petroleum oils by solvent or autorefrigerative dewaxing. Solvent dewaxing employs chilled solvent such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), mixtures of MEK/MIBK, mixtures of MEK and toluene, while autorefrigerative dewaxing employs pressurized, liquefied low boiling hydrocarbons such as propane or butane.
Slack wax(es) secured from synthetic waxy oils such as F-T waxy oil will usually have zero or nil sulfur and/or nitrogen containing compound content. Slack wax(es) secured from petroleum oils, may contain sulfur and nitrogen containing compounds. Such heteroatom compounds must be removed by hydrotreating (and not hydrocracking), as for example by hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) so as to avoid subsequent poisoning/deactivation of the hydroisomerization catalyst.
The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil as used herein and in the claims is to be understood as embracing individual fractions of GTL base stock and/or base oil and/or of wax-derived hydrodewaxed or hydroisomerized/cat (and/or solvent) dewaxed base stock and/or base oil as recovered in the production process, mixtures of two or more GTL base stock and/or base oil fractions and/or wax-derived hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stocks and/or base oil fractions, as well as mixtures of one or two or more low viscosity GTL base stock and/or base oil fraction(s) and/or wax-derived hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock and/or base oil fraction(s) with one, two or more higher viscosity GTL base stock and/or base oil fraction(s) and/or wax-derived hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock and/or base oil fraction(s) to produce a dumbbell blend wherein the blend exhibits a kinematic viscosity within the aforesaid recited range and meets the 15% or less Noack volatility limit and each such blend individually constituted one or the other, or both, of the first and second base stock(s) and/or base oil(s) of the present mixture.
In a preferred embodiment, the GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax). A slurry F-T synthesis process may be beneficially used for synthesizing the feed from CO and hydrogen and particularly one employing an F-T catalyst comprising a catalytic cobalt component to provide a high Schultz-Flory kinetic alpha for producing the more desirable higher molecular weight paraffins. This process is also well known to those skilled in the art.
In an F-T synthesis process, a synthesis gas comprising a mixture of H₂ and CO is catalytically converted into hydrocarbons and preferably liquid hydrocarbons. 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. As is well known, F-T synthesis processes include processes in which the catalyst is in the form of a fixed bed, a fluidized bed or as a slurry of catalyst particles in a hydrocarbon slurry liquid. The stoichiometric mole ratio for a F-T synthesis reaction is 2.0, but there are many reasons for using other than a stoichiometric ratio as those skilled in the art know. In cobalt slurry hydrocarbon synthesis process the feed mole ratio of the H₂ to CO is typically about 2.1/1. The synthesis gas comprising a mixture of H₂ and CO is bubbled up into the bottom of the slurry and reacts in the presence of the particulate F-T synthesis catalyst in the slurry liquid at conditions effective to form hydrocarbons, a portion of which are liquid at the reaction conditions and which comprise the hydrocarbon slurry liquid. The synthesized hydrocarbon liquid is separated from the catalyst particles as filtrate by means such as filtration, although other separation means such as centrifugation can be used. Some of the synthesized hydrocarbons pass out the top of the hydrocarbon synthesis reactor as vapor, along with unreacted synthesis gas and other gaseous reaction products. Some of these overhead hydrocarbon vapors are typically condensed to liquid and combined with the hydrocarbon liquid filtrate. Thus, the initial boiling point of the filtrate may vary depending on whether or not some of the condensed hydrocarbon vapors have been combined with it. Slurry hydrocarbon synthesis process conditions vary somewhat depending on the catalyst and desired products. Typical conditions effective to form hydrocarbons comprising mostly C₅₊ paraffins, (e.g., C₅₊-C₂₀₀) and preferably C₁₀₊ paraffins, in a slurry hydrocarbon synthesis process employing a catalyst comprising a supported cobalt component include, for example, temperatures, pressures and hourly gas space velocities in the range of from 160-454°C (320-850°F), 80-600 psi and 100-40,000 V/hr/V, expressed as standard volumes of the gaseous CO and H₂ mixture (0°C, 1 atm) per hour per volume of catalyst, respectively. The term "C₅₊" is used herein to refer to hydrocarbons with a carbon number of greater than 4, but does not imply that material with carbon number 5 has to be present. Similarly other ranges quoted for carbon number do not imply that hydrocarbons having the limit values of the carbon number range have to be present, or that every carbon number in the quoted range is present. It is preferred that the hydrocarbon synthesis reaction be conducted under conditions in which limited or no water gas shift reaction occurs and more preferably with no water gas shift reaction occurring during the hydrocarbon synthesis. It is also preferred to conduct the reaction under conditions to achieve an alpha of at least 0.85, preferably at least 0.9 and more preferably at least 0.92, so as to synthesize more of the more desirable higher molecular weight hydrocarbons. This has been achieved in a slurry process using a catalyst containing a catalytic cobalt component. Those skilled in the art know that by alpha is meant the Schultz-Flory kinetic alpha. While suitable F-T reaction types of catalyst comprise, for example, one or more Group VIII catalytic metals such as Fe, Ni, Co, Ru and Re, it is preferred that the catalyst comprise a cobalt catalytic component. 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. 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 .
As set forth above, the waxy feed from which the base stock(s) and/or base oil(s) is/are derived is a wax or waxy feed from mineral oil, non-mineral oil, non-petroleum, or other natural source, especially slack wax, or GTL material, preferably F-T material, referred to as F-T wax. F-T wax preferably has an initial boiling point in the range of from 343-399°C (650-750°F) and preferably continuously boils up to an end point of at least 566°C (1050°F). A narrower cut waxy feed may also be used during the hydroisomerization. A portion of the n-paraffin waxy feed is converted to lower boiling isoparaffinic material. Hence, there must be sufficient heavy n-paraffin material to yield an isoparaffin containing isomerate boiling in the lube oil range. If catalytic dewaxing is also practiced after isomerization/isodewaxing, some of the isomerate/isodewaxate will also be hydrocracked to lower boiling material during the conventional catalytic dewaxing. Hence, it is preferred that the end boiling point of the waxy feed be above 566°C (566°C+) [1050°F (1050°F+)].
When a boiling range is quoted herein it defines the lower and/or upper distillation temperature used to separate the fraction. Unless specifically stated (for example, by specifying that the fraction boils continuously or constitutes the entire range) the specification of a boiling range does not require that any material at the specified limit has to be present, rather it excludes material boiling outside that range.
The waxy feed preferably comprises the entire 343-399°C+ (650-750°F+) fraction formed by the hydrocarbon synthesis process, having an initial cut point between 343°C (650°F) and 399°C (750°F) determined by the practitioner and an end point, preferably above 566°C (1050°F), determined by the catalyst and process variables employed by the practitioner for the synthesis. Such fractions are referred to herein as "343-399°C+ (650-750°F+) fractions". By contrast, "343-399°C- (650-750°F-) fractions" refers to a fraction with an unspecified initial cut point and an end point somewhere between 343°C (650°F) and 399°C (750°F). Waxy feeds may be processed as the entire fraction or as subsets of the entire fraction prepared by distillation or other separation techniques. The waxy feed also typically comprises more than 90%, generally more than 95% and preferably more than 98 wt% paraffinic hydrocarbons, most of which are normal paraffins. It has negligible amounts of sulfur and nitrogen compounds (e.g., less than 1 wppm of each), 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. Waxy feeds having these properties and useful in the process of the invention have been made using a slurry F-T process with a catalyst having a catalytic cobalt component, as previously indicated.
The process of making the lubricant oil base stocks from waxy stocks, e.g., slack wax or F-T wax, may be characterized as an isomerization process. If slack waxes are used as the feed, they may need to be subjected to a preliminary hydrotreating step under conditions already well known to those skilled in the art to reduce (to levels that would effectively avoid catalyst poisoning or deactivation) or to remove sulfur- and nitrogen-containing compounds which would otherwise deactivate the hydroisomerization or hydrodewaxing catalyst used in subsequent steps. If F-T waxes are used, such preliminary treatment is not required because, as indicated above, such waxes have only trace amounts (less than 10 ppm, or more typically less than 5 ppm to nil) of sulfur or nitrogen compound content. However, some hydrodewaxing catalyst fed F-T waxes may benefit from prehydrotreatment for the removal of oxygenates while others may benefit from oxygenates treatment. The hydroisomerization or hydrodewaxing process may be conducted over a combination of catalysts, or over a single catalyst. Conversion temperatures range from 150°C to 500°C at pressures ranging from 500 to 20,000 kPa. This process may be operated in the presence of hydrogen, and hydrogen partial pressures range from 600 to 6000 kPa. The ratio of hydrogen to the hydrocarbon feedstock (hydrogen circulation rate) typically range from 10 to 3500 n.1.1.^-1 (56 to 19,660 SCF/bbl) and the space velocity of the feedstock typically ranges from 0.1 to 20 LHSV, preferably 0.1 to 10 LHSV.
Following any needed hydrodenitrogenation or hydrodesulfurization, the hydroprocessing used for the production of base stocks from such waxy feeds may use an amorphous hydrocracking/hydroisomerization catalyst, such as a lube hydrocracking (LHDC) catalysts, for example catalysts containing Co, Mo, Ni, W, Mo, etc., on oxide supports, e.g., alumina, silica, silica/alumina, or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst.
Other isomerization catalysts and processes for hydrocracking, hydrodewaxing, or hydroisomerizing GTL materials and/or waxy materials to base stock or base oil are described, for example, in U.S. Pat. Nos. 2,817,693 ; 4,900,407 ; 4,937,399 ; 4,975,177 ; 4,921,594 ; 5,200,382 ; 5,516,740 ; 5,182,248 ; 5,290,426 ; 5,580,442 ; 5,976,351 ; 5,935,417 ; 5,885,438 ; 5,965,475 ; 6,190,532 ; 6,375,830 ; 6,332,974 ; 6,103,099 ; 6,025,305 ; 6,080,301 ; 6,096,940 ; 6,620,312 ; 6,676,827 ; 6,383,366 ; 6,475,960 ; 5,059,299 ; 5,977,425 ; 5,935,416 ; 4,923,588 ; 5,158,671 ; and 4,897,178 ; EP 0324528 (B1 ), EP 0532116 (B1 ), EP 0532118 (B1 ), EP 0537815 (B1 ), EP 0583836 (B2 ), EP 0666894 (B2 ), EP 0668342 (B1 ), EP 0776959 (A3 ), WO 97/031693 (A1 ), WO 02/064710 (A2 ), WO 02/064711 (A1 ), WO 02/070627 (A2 ), WO 02/070629 (A1 ), WO 03/033320 (A1 ) as well as in British Patents 1,429,494 ; 1,350,257 ; 1,440,230 ; 1,390,359 ; WO 99/45085 and WO 99/20720 . Particularly favorable processes are described in European Patent Applications 464546 and 464547 . Processes using F-T wax feeds are described in U.S. Pat. Nos. 4,594,172 ; 4,943,672 ; 6,046,940 ; 6,475,960 ; 6,103,099 ; 6,332,974 ; and 6,375,830 .
Hydrocarbon conversion catalysts useful in the conversion of the n-paraffin waxy feedstocks disclosed herein to form the isoparaffinic hydrocarbon base oil are zeolite catalysts, such as ZSM-5, ZSM-11, ZSM-23, ZSM-35, ZSM-12, ZSM-38, ZSM-48, offretite, ferrierite, zeolite beta, zeolite theta, and zeolite alpha, as disclosed in USP 4,906,350 . These catalysts are used in combination with Group VIII metals, in particular palladium or platinum. The Group VIII metals may be incorporated into the zeolite catalysts by conventional techniques, such as ion exchange.
In one embodiment, conversion of the waxy feedstock may be conducted over a combination of Pt/zeolite beta and Pt/ZSM-23 catalysts in the presence of hydrogen. In another embodiment, the process of producing the lubricant oil base stocks comprises hydroisomerization and dewaxing over a single catalyst, such as Pt/ZSM-35. In yet another embodiment, the waxy feed can be fed over a catalyst comprising Group VIII metal loaded ZSM-48, preferably Group VIII noble metal loaded ZSM-48, more preferably Pt/ZSM-48 in either one stage or two stages. In any case, useful hydrocarbon base oil products may be obtained. Catalyst ZSM-48 is described in USP 5,075,269 . The use of the Group VIII metal loaded ZSM-48 family of catalysts, e.g., platinum on ZSM-48, in the hydroisomerization of the waxy feedstock eliminates the need for any subsequent, separate dewaxing step.
A dewaxing step, when needed, may be accomplished using one or more of solvent dewaxing, catalytic dewaxing or hydrodewaxing processes and either the entire hydroisomerate or the 343-399°C+ (650-750°F+) fraction may be dewaxed, depending on the intended use of the 343-399°C- (650-750°F-) material present, if it has not been separated from the higher boiling material prior to the dewaxing. In solvent dewaxing, the hydroisomerate may be contacted with chilled solvents such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), mixtures of MEK/MIBK, or mixtures of MEK/toluene and the like, and further chilled to precipitate out the higher pour point material as a waxy solid which is then separated from the solvent-containing lube oil fraction which is the raffinate. The raffinate is typically further chilled in scraped surface chillers to remove more wax solids. Autorefrigerative dewaxing using low molecular weight hydrocarbons, such as propane, can also be used in which the hydroisomerate is mixed with, e.g., liquid propane, a least a portion of which is flashed off to chill down the hydroisomerate to precipitate out the wax. The wax is separated from the raffinate by filtration, membrane separation or centrifugation. The solvent is then stripped out of the raffinate, which is then fractionated to produce the preferred base stocks useful in the present invention. Also well known is catalytic dewaxing, in which the hydroisomerate is reacted with hydrogen in the presence of a suitable dewaxing catalyst at conditions effective to lower the pour point of the hydroisomerate. Catalytic dewaxing also converts a portion of the hydroisomerate to lower boiling materials, in the boiling range, for example, 343-399°C- (650-750°F-), which are separated from the heavier 343-399°C+ (650-750°F+) base stock fraction and the base stock fraction fractionated into two or more base stocks. Separation of the lower boiling material may be accomplished either prior to or during fractionation of the 343-399°C+ (650-750°F+) material into the desired base stocks.
Any dewaxing catalyst which will reduce the pour point of the hydroisomerate and preferably those which provide a large yield of lube oil base stock from the hydroisomerate may be used. 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 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. A dewaxing catalyst which has been found to be unexpectedly particularly effective comprises a noble metal, preferably Pt, composited with H-mordenite. 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 204-316°C (400-600°F), a pressure of 500-900 psig, H₂ 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 hydroisomerate having an initial boiling point in the range of 343-399°C (650-750°F) to material boiling below its initial boiling point.
GTL base stock(s) and/or base oil(s), hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed wax-derived base stock(s) and/or base oil(s), have a beneficial kinematic viscosity advantage over conventional API Group II and Group III base stock(s) and/or base oil(s), and so may be very advantageously used with the instant invention. Such GTL base stock(s) and/or base oil(s) can have significantly higher kinematic viscosities, up to 20-50 mm²/s at 100°C, whereas by comparison commercial Group II base oils can have kinematic viscosities up to 15 mm²/s at 100°C, and commercial Group III base oils can have kinematic viscosities up to 10 mm²/s at 100°C. The higher kinematic viscosity range of GTL base stock(s) and/or base oil(s), compared to the more limited kinematic viscosity range of Group II and Group III base stock(s) and/or base oil(s), in combination with the instant invention can provide additional beneficial advantages in formulating lubricant compositions.
In the present invention mixtures of hydrodewaxate, or hydroisomerate/cat or solvent) dewaxate base stock(s) and/or base oil(s), mixtures of the GTL base stock(s) and/or base oil(s), or mixtures thereof, preferably mixtures of GTL base stock(s) and/or base oil(s), provided each component in the mixture has been subjected to a different wax processing technique, can constitute all or part of the base oil.
The preferred base stock(s) and/or base oil(s) derived from GTL materials and/or from waxy feeds are characterized as having predominantly paraffinic compositions and are further characterized as having high saturates levels, low-to-nil sulfur, low-to-nil nitrogen, low-to-nil aromatics, and are essentially water-white in color.
A preferred GTL liquid hydrocarbon composition is one comprising paraffinic hydrocarbon components in which the extent of branching, as measured by the percentage of methyl hydrogens (BI), and the proximity of branching, as measured by the percentage of recurring methylene carbons which are four or more carbons removed from an end group or branch (CH₂ ≥ 4), are such that: (a) BI-0.5(CH₂ ≥ 4) >15; and (b) BI+0.85 (CH₂ ≥ 4) <45 as measured over said liquid hydrocarbon composition as a whole.
The preferred GTL base stock and/or base oil can be further characterized, if necessary, as having less than 0.1 wt% aromatic hydrocarbons, less than 20 wppm nitrogen containing compounds, less than 20 wppm sulfur containing compounds, a pour point of less than -18°C, preferably less than - 30°C, a preferred BI ≧ 25.4 and (CH₂ ≥ 4) ≤ 22.5. They have a nominal boiling point of 370°C⁺, on average they average fewer than 10 hexyl or longer branches per 100 carbon atoms and on average have more than 16 methyl branches per 100 carbon atoms. They also can be characterized by a combination of dynamic viscosity, as measured by CCS at -40°C, and kinematic viscosity, as measured at 100°C represented by the formula: DV (at -40°C) < 2900 (KV at 100°C) - 7000.
The preferred GTL base stock and/or base oil is also characterized as comprising a mixture of branched paraffins characterized in that the lubricant base oil contains at least 90% of a mixture of branched paraffins, wherein said branched paraffins are paraffins having a carbon chain length of C₂₀ to C₄₀, a molecular weight of 280 to 562, a boiling range of 343°C (650°F) to 566°C (1050°F), and wherein said branched paraffins contain up to four alkyl branches and wherein the free carbon index of said branched paraffins is at least 3.
In the above the Branching Index (BI), Branching Proximity (CH₂ ≥ 4), and Free Carbon Index (FCI) are determined as follows:

Branching Index

A 359.88 MHz 1 H solution NMR spectrum is obtained on a Bruker 360 MHz AMX spectrometer using 10% solutions in CDCl₃. TMS is the internal chemical shift reference. CDCl₃ solvent gives a peak located at 7.28. All spectra are obtained under quantitative conditions using 90 degree pulse (10.9 µs), a pulse delay time of 30 s, which is at least five times the longest hydrogen spin-lattice relaxation time (T₁), and 120 scans to ensure good signal-to-noise ratios.
H atom types are defined according to the following regions:

9.2-6.2 ppm hydrogens on aromatic rings;
6.2-4.0 ppm hydrogens on olefinic carbon atoms;
4.0-2.1 ppm benzylic hydrogens at the α-position to aromatic rings;
2.1-1.4 ppm paraffinic CH methine hydrogens;
1.4-1.05 ppm paraffinic CH₂ methylene hydrogens;
1.05-0.5 ppm paraffinic CH₃ methyl hydrogens.

The branching index (BI) is calculated as the ratio in percent of non-benzylic methyl hydrogens in the range of 0.5 to 1.05 ppm, to the total non-benzylic aliphatic hydrogens in the range of 0.5 to 2.1 ppm.

Branching Proximity (CH₂ ≧ 4)

A 90.5 MHz³CMR single pulse and 135 Distortionless Enhancement by Polarization Transfer (DEPT) NMR spectra are obtained on a Brucker 360 MHzAMX spectrometer using 10% solutions in CDCL₃. TMS is the internal chemical shift reference. CDCL₃ solvent gives a triplet located at 77.23 ppm in the ¹³C spectrum. All single pulse spectra are obtained under quantitative conditions using 45 degree pulses (6.3 µs), a pulse delay time of 60 s, which is at least five times the longest carbon spin-lattice relaxation time (T₁), to ensure complete relaxation of the sample, 200 scans to ensure good signal-to-noise ratios, and WALTZ-16 proton decoupling.
The C atom types CH₃, CH₂, and CH are identified from the 135 DEPT ¹³C NMR experiment. A major CH₂ resonance in all ¹³C NMR spectra at ≈29.8 ppm is due to equivalent recurring methylene carbons which are four or more removed from an end group or branch (CH2 > 4). The types of branches are determined based primarily on the ¹³C chemical shifts for the methyl carbon at the end of the branch or the methylene carbon one removed from the methyl on the branch.
Free Carbon Index (FCI). The FCI is expressed in units of carbons, and is a measure of the number of carbons in an isoparaffin that are located at least 5 carbons from a terminal carbon and 4 carbons way from a side chain. Counting the terminal methyl or branch carbon as "one" the carbons in the FCI are the fifth or greater carbons from either a straight chain terminal methyl or from a branch methane carbon. These carbons appear between 29.9 ppm and 29.6 ppm in the carbon-13 spectrum. They are measured as follows:

a) calculate the average carbon number of the molecules in the sample which is accomplished with sufficient accuracy for lubricating oil materials by simply dividing the molecular weight of the sample oil by 14 (the formula weight of CH₂);
b) divide the total carbon-13 integral area (chart divisions or area counts) by the average carbon number from step a. to obtain the integral area per carbon in the sample;
c) measure the area between 29.9 ppm and 29.6 ppm in the sample; and
d) divide by the integral area per carbon from step b. to obtain FCI.

Branching measurements can be performed using any Fourier Transform NMR spectrometer. Preferably, the measurements are performed using a spectrometer having a magnet of 7.0T or greater. In all cases, after verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons were absent, the spectral width was limited to the saturated carbon region, about 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 15-25 percent by weight in chloroform-d1 were excited by 45 degrees pulses followed by a 0.8 sec acquisition time. In order to minimize non-uniform intensity data, the proton decoupler was gated off during a 10 sec delay prior to the excitation pulse and on during acquisition. Total experiment times ranged from 11-80 minutes. The DEPT and APT sequences were carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals.
DEPT is Distortionless Enhancement by Polarization Transfer. DEPT does not show quaternaries. The DEPT 45 sequence gives a signal for all carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows CH and CH₃ up and CH₂ 180 degrees out of phase (down). APT is Attached Proton Test. It allows all carbons to be seen, but if CH and CH₃ are up, then quaternaries and CH₂ are down. The sequences are useful in that every branch methyl should have a corresponding CH and the methyls are clearly identified by chemical shift and phase. The branching properties of each sample are determined by C-13 NMR using the assumption in the calculations that the entire sample is isoparaffinic. Corrections are not made for n-paraffins or cycloparaffins, which may be present in the oil samples in varying amounts. The cycloparaffins content is measured using Field Ionization Mass Spectroscopy (FIMS).
GTL base stock(s) and/or base oil(s), and hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed wax base stock(s) and/or base oil(s), for example, hydrodewaxed or hydroisomerized/catalytic (and/or solvent) dewaxed waxy synthesized hydrocarbon, e.g., Fischer-Tropsch waxy hydrocarbon base stock(s) and/or base oil(s) are of low or zero sulfur and phosphorus content. There is a movement among original equipment manufacturers and oil formulators to produce formulated oils of ever increasingly reduced sulfated ash, phosphorus and sulfur content to meet ever increasingly restrictive environmental regulations. Such oils, known as low SAPS oils, would rely on the use of base oils which themselves, inherently, are of low or zero initial sulfur and phosphorus content. Such oils when used as base oils can be formulated with additives. Even if the additive or additives included in the formulation contain sulfur and/or phosphorus the resulting formulated lubricating oils will be lower or low SAPS oils as compared to lubricating oils formulated using conventional mineral oil base stock(s) and/or base oil(s).
For example, low SAPS formulated oils for vehicle engines (both spark ignited and compression ignited) will have a sulfur content of 0.7 wt% or less, preferably 0.6 wt% or less, more preferably 0.5 wt% or less, most preferably 0.4 wt% or less, an ash content of 1.2 wt% or less, preferably 0.8 wt% or less, more preferably 0.4 wt% or less, and a phosphorus content of 0.18% or less, preferably 0.1 wt% or less, more preferably 0.09 wt% or less, most preferably 0.08 wt% or less, and in certain instances, even preferably 0.05 wt% or less.
The combination base stock is formulated with typical automotive engine lubricating additives, but can omit or significantly reduce the amount of viscosity modifier and pour point depressants heretofore conventionally utilized to meet SAE 0W-X and 5W-X multi-grade engine oil low temperature viscometric and rheological properties.
Examples of typical additives include, but are not limited to, oxidation inhibitors, antioxidants, dispersants, detergents, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents, extreme pressure additives, anti-seizure agents, wax modifiers, other viscosity index improvers, other viscosity modifiers, fluid-loss additives, seal compatibility agents, friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, FL; ISBN 0-89573-177-0. Reference is also made to "Lubricant Additives" by M. W. Ranney, published by Noyes Data Corporation of Parkridge, NJ (1973).
Finished lubricants comprise the lubricant base stock or base oil, plus at least one performance additive.
The types and quantities of performance additives used in combination with the instant invention in lubricant compositions are not limited by the examples shown herein as illustrations.

Antiwear and EP Additives

Many lubricating oils require the presence of antiwear and/or extreme pressure (EP) additives in order to provide adequate antiwear protection. Increasingly specifications for, e.g., engine oil performance have exhibited a. trend for improved antiwear properties of the oil. Antiwear and extreme EP additives perform this role by reducing friction and wear of metal parts.
While there are many different types of antiwear additives, for several decades the principal antiwear additive for internal combustion engine crankcase oils is a metal alkylthiophosphate and more particularly a metal dialkyldithiophosphate in which the primary metal constituent is zinc, or zinc dialkyldithiophosphate (ZDDP). ZDDP compounds generally are of the formula Zn[SP(S)(OR¹)(OR²)]₂ where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. The ZDDP is typically used in amounts of from about 0.4 to 1.4 wt% of the total lube oil composition, although more or less can often be used advantageously.
However, it is found that the phosphorus from these additives has a deleterious effect on the catalyst in catalytic converters and also on oxygen sensors in automobiles. One way to minimize this effect is to replace some or all of the ZDDP with phosphorus-free antiwear additives.
A variety of non-phosphorous additives are also used as antiwear additives. Sulfurized olefins are useful as antiwear and EP additives. Sulfur-containing olefins can be prepared by sulfurization or various organic materials including aliphatic, arylaliphatic or alicyclic olefinic hydrocarbons containing from about 3 to 30 carbon atoms, preferably 3-20 carbon atoms. The olefinic compounds contain at least one non-aromatic double bond. Such compounds are defined by the formula

R³R⁴C=CR⁵R⁶

where each of R³-R⁶ are independently hydrogen or a hydrocarbon radical. Preferred hydrocarbon radicals are alkyl or alkenyl radicals. Any two of R³-R⁶ may be connected so as to form a cyclic ring. Additional information concerning sulfurized olefins and their preparation can be found in USP 4,941,984 , incorporated by reference herein in its entirety.
The use of polysulfides of thiophosphorus acids and thiophosphorus acid esters as lubricant additives is disclosed in U.S. Patents 2,443,264 ; 2,471,115 ; 2,526,497 ; and 2,591,577 . Addition of phosphorothionyl disulfides as an antiwear, antioxidant, and EP additive is disclosed in USP 3,770,854 . Use of alkylthiocarbamoyl compounds (bis(dibutyl)thiocarbamoyl, for example) in combination with a molybdenum compound (oxymolybdenum diisopropylphosphorodithioate sulfide, for example) and a phosphorous ester (dibutyl hydrogen phosphite, for example) as antiwear additives in lubricants is disclosed in USP 4,501,678 . USP 4,758,362 discloses use of a carbamate additive to provide improved antiwear and extreme pressure properties. The use of thiocarbamate as an antiwear additive is disclosed in USP 5,693,598 . Thiocarbamate/molybdenum complexes such as moly-sulfur alkyl dithiocarbamate trimer complex (R=C₈-C₁₈ alkyl) are also useful antiwear agents. The use or addition of such materials should be kept to a minimum if the object is to produce low SAP formulations.
Esters of glycerol may be used as antiwear agents. For example, mono-, di-, and tri-oleates, mono-palmitates and mono-myristates may be used.
ZDDP is combined with other compositions that provide antiwear properties. USP 5,034,141 discloses that a combination of a thiodixanthogen compound (octylthiodixanthogen, for example) and a metal thiophosphate (ZDDP, for example) can improve antiwear properties. USP 5,034,142 discloses that use of a metal alkyoxyalkylxanthate (nickel ethoxyethylxanthate, for example) and a dixanthogen (diethoxyethyl dixanthogen, for example) in combination with ZDDP improves antiwear properties.
Preferred antiwear additives include phosphorus and sulfur compounds such as zinc dithiophosphates and/or sulfur, nitrogen, boron, molybdenum phosphorodithioates, molybdenum dithiocarbamates and various organo-molybdenum derivatives including heterocyclics, for example dimercaptothiadiazoles, mercaptobenzothiadiazoles, triazines, and the like, alicyclics, amines, alcohols, esters, diols, triols, fatty amides and the like can also be used. Such additives may be used in an amount of about 0.01 to 6 wt%, preferably about 0.01 to 4 wt%. ZDDP-like compounds provide limited hydroperoxide decomposition capability, significantly below that exhibited by compounds disclosed and claimed in this patent and can therefore be eliminated from the formulation or, if retained, kept at a minimal concentration to facilitate production of low SAPS formulations.

Viscosity Improvers

Viscosity improvers (also known as Viscosity Index modifiers, and VI improvers) provide lubricants with high and low temperature operability. These additives increase the viscosity of the oil composition at elevated temperatures which increases film thickness, while having limited effect on viscosity at low temperatures.
Suitable viscosity improvers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,000,000, more typically about 20,000 to 500,000, and even more typically between about 50,000 and 200,000.
Examples of suitable viscosity improvers are polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity index improver. Another suitable viscosity index improver is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity index improvers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.
The amount of viscosity modifier may range from zero to 8 wt%, preferably zero to 4 wt%, more preferably zero to 2 wt% based on active ingredient and depending on the specific viscosity modifier used.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Patents 4,798,684 and 5,084,197 , for example.
Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant invention. Examples of ortho-coupled phenols include: 2,2'-bis(4-heptyl-6-t-butyl-phenol); 2,2'-bis(4-octyl-6-t-butyl-phenol); and 2,2'-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4'-bis(2,6-di-t-butyl phenol) and 4,4'-methylene-bis(2,6-di-t-butyl phenol).
Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_XR¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to about 20 carbon atoms, and preferably contains from about 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.
Typical aromatic amines antioxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than about 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present invention include: p,p'-dioctyldiphenylamine; t-octylphenyl-alphanaphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alphanaphthylamine.
Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.
Another class of antioxidant used in lubricating oil compositions is oil-soluble copper compounds. Any oil-soluble suitable copper compound may be blended into the lubricating oil. Examples of suitable copper antioxidants include copper dihydrocarbyl thio- or dithio-phosphates and copper salts of carboxylic acid (naturally occurring or synthetic). Other suitable copper salts include copper dithiacarbamates, sulphonates, phenates, and acetylacetonates. Basic, neutral, or acidic copper Cu(I) and or Cu(II) salts derived from alkenyl succinic acids or anhydrides are know to be particularly useful.
Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of about 0.01 to 5 wt%, preferably about 0.01 to 1.5 wt%, more preferably zero to less than 1.5 wt%, most preferably zero.

Detergents

Detergents are commonly used in lubricating compositions. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur acid, carboxylic acid, phosphorous acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal.
Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased.
It is desirable for at least some detergent to be overbased. Overbased detergents help neutralize acidic impurities produced by the combustion process and become entrapped in the oil. Typically, the overbased material has a ratio of metallic ion to anionic portion of the detergent of about 1.05:1 to 50:1 on an equivalent basis. More preferably, the ratio is from about 4:1 to about 25:1. The resulting detergent is an overbased detergent that will typically have a TBN of about 150 or higher, often about 250 to 450 or more. Preferably, the overbasing cation is sodium, calcium, or magnesium. A mixture of detergents of differing TBN can be used in the present invention.
Preferred detergents include the alkali or alkaline earth metal salts of sulfonates, phenates, carboxylates, phosphates, and salicylates.
Sulfonates may be prepared from sulfonic acids that are typically obtained by sulfonation of alkyl substituted aromatic hydrocarbons. Hydrocarbon examples include those obtained by alkylating benzene, toluene, xylene, naphthalene, biphenyl and their halogenated derivatives (chlorobenzene, chlorotoluene, and chloronaphthalene, for example). The alkylating agents typically have about 3 to 70 carbon atoms. The alkaryl sulfonates typically contain about 9 to about 80 carbon or more carbon atoms, more typically from about 16 to 60 carbon atoms.
Klamann in Lubricants and Related Products, op cit discloses a number of overbased metal salts of various sulfonic acids which are useful as detergents and dispersants in lubricants. The book entitled "Lubricant Additives", C. V. Smallheer and R. K. Smith, published by the Lezius-Hiles Co. of Cleveland, Ohio (1967), similarly discloses a number of overbased sulfonates that are useful as dispersants/detergents.
Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.
Metal salts of carboxylic acids are also useful as detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula
where R is a hydrogen atom or an alkyl group having 1 to about 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, or barium. More preferably, M is calcium.
Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction. See USP 3,595,791 , which is incorporated herein by reference in its entirety, for additional information on synthesis of these compounds. The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.
Alkaline earth metal phosphates are also used as detergents.
Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See USP 6,034,039 for example.
Preferred detergents include calcium phenates, calcium sulfonates, calcium salicylates, magnesium phenates, magnesium sulfonates, magnesium salicylates and other related components (including borated detergents). Typically, the total detergent concentration is about 0.01 to about 6.0 wt%, preferably, about 0.1 to 0.4 wt%.

Dispersant

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.
Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.
Chemically, many dispersants may be characterized as phenates, sulfonates, sulfurized phenates, salicylates, naphthenates, stearates, carbamates, thiocarbamates, phosphorus derivatives. A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain substituted alkenyl succinic compound, usually a substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are 3,172,892 ; 3,2145,707 ; 3,219,666 ; 3,316,177 ; 3,341,542 ; 3,444,170 ; 3,454,607 ; 3,541,012 ; 3,630,904 ; 3,632,511 ; 3,787,374 and 4,234,435 . Other types of dispersant are described in U.S. Pat. Nos. 3,036,003 ; 3,200,107 ; 3,254,025 ; 3,275,554 ; 3,438,757 ; 3,454,555 ; 3,565,804 ; 3,413,347 ; 3,697,574 ; 3,725,277 ; 3,725,480 ; 3,726,882 ; 4,454,059 ; 3,329,658 ; 3,449,250 ; 3,519,565 ; 3,666,730 ; 3,687,849 ; 3,702,300 ; 4,100,082 ; 5,705,458 . A further description of dispersants may be found, for example, in European Patent Application No. 471 071 , to which reference is made for this purpose.
Hydrocarbyl-substituted succinic acid compounds are popular dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.
Succinimides are formed by the condensation reaction between alkenyl succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of alkenyl succinic anhydride to TEPA can vary from about 1:1 to about 5:1. Representative examples are shown in U.S. Patents 3,087,936 ; 3,172,892 ; 3,219,666 ; 3,272,746 ; 3,322,670 ; and 3,652,616 , 3,948,800 ; and Canada Pat. No. 1,094,044 .
Succinate esters are formed by the condensation reaction between alkenyl succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of an alkenyl succinic anhydride and pentaerythritol is a useful dispersant.
Succinate ester amides are formed by condensation reaction between alkenyl succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpoly-amines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in USP 4,426,305 .
The molecular weight of the alkenyl succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid, and boron compounds such as borate esters or highly borated dispersants. The dispersants can be borated with from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.
Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See USP 4,767,551 , which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Patents 3,697,574 ; 3,703,536 ; 3,704,308 ; 3,751,365 ; 3,756,953 ; 3,798,165 ; and 3,803,039 .
Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this invention can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HN(R)₂ group-containing reactants.
Examples of high molecular weight alkyl-substituted hydroxyaromatic compounds are polypropylphenol, polybutylphenol, and other polyalkylphenols. These polyalkylphenols can be obtained by the alkylation, in the presence of an alkylating catalyst, such as BF₃, of phenol with high molecular weight polypropylene, polybutylene, and other polyalkylene compounds to give alkyl substituents on the benzene ring of phenol having an average 600-100,000 molecular weight.
Examples of HN(R)₂ group-containing reactants are alkylene polyamines, principally polyethylene polyamines. Other representative organic compounds containing at least one HN(R)₂ group suitable for use in the preparation of Mannich condensation products are well known and include the mono-and di-amino alkanes and their substituted analogs, e.g., ethylamine and diethanol amine; aromatic diamines, e.g., phenylene diamine, diamino naphthalenes; heterocyclic amines, e.g., morpholine, pyrrole, pyrrolidine, imidazole, imidazolidine, and piperidine; melamine and their substituted analogs.
Examples of alkylene polyamide reactants include ethylenediamine, diethylene triamine, triethylene tetraamine, tetraethylene pentaamine, pentaethylene hexamine, hexaethylene heptaamine, heptaethylene octaamine, octaethylene nonaamine, nonaethylene decamine, and decaethylene undecamine and mixture of such amines having nitrogen contents corresponding to the alkylene polyamines, in the formula H₂N-(Z-NH-)_nH, mentioned before, Z is a divalent ethylene and n is 1 to 10 of the foregoing formula. Corresponding propylene polyamines such as propylene diamine and di-, tri-, tetra-, penta-propylene tri-, tetra-, penta- and hexaamines are also suitable reactants. The alkylene polyamines are usually obtained by the reaction of ammonia and dihalo alkanes, such as dichloro alkanes. Thus the alkylene polyamines obtained from the reaction of 2 to 11 moles of ammonia with 1 to 10 moles of dichloroalkanes having 2 to 6 carbon atoms and the chlorines on different carbons are suitable alkylene polyamine reactants.
Aldehyde reactants useful in the preparation of the high molecular products useful in this invention include the aliphatic aldehydes such as formaldehyde (also as paraformaldehyde and formalin), acetaldehyde and aldol (β-hydroxybutyraldehyde). Formaldehyde or a formaldehyde-yielding reactant is preferred.
Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Patents 3,275,554 ; 3,438,757 ; 3,565,804 ; 3,755,433 , 3,822,209 , and 5,084,197 , which are incorporated herein in their entirety by reference.
Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000 or a mixture of such hydrocarbylene groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. Such additives may be used in an amount of about 0.1 to 20 wt%, preferably about 0.1 to 8 wt%.

Optional Pour Point Depressants

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present invention if desired to help meet MRV and/or yield stress targets. These pour point depressant may be added to lubricating compositions of the present invention to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include alkylated naphthalenes polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. USP Nos. 1,815,022 ; 2,015,748 ; 2,191,498 ; 2,387,501 ; 2,655, 479 ; 2,666,746 ; 2,721,877 ; 2.721,878 ; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be omitted totally or may be used in a minor amount of about 0.001 to 0.1 wt% on an as-received basis.

Corrosion Inhibitors

Corrosion inhibitors are used to reduce the degradation of metallic parts that are in contact with the lubricating oil composition. Suitable corrosion inhibitors include thiadiazoles. See, for example, USP Nos. 2,719,125 ; 2,719,126 ; and 3,087,932 , which are incorporated herein by reference in their entirety. Such additives may be used in an amount of about 0.01 to 5 wt%, preferably about 0.01 to 1.5 wt%.

Seal Compatibility Additives

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of about 0.01 to 3 wt%, preferably about 0.01 to 2 wt%.

Anti-Foam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 percent and often less than 0.1 percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available; they are referred to in Klamann in Lubricants and Related Products, op cit.
One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of about 0.01 to 5 wt%, preferably about 0.01 to 1.5 wt%.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present invention if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this invention. Friction modifiers may include metal-containing compounds or materials as well as ashless compounds or materials, or mixtures thereof. Metal-containing friction modifiers may include metal salts or metal-ligand complexes where the metals may include alkali, alkaline earth, or transition group metals. Such metal-containing friction modifiers may also have low-ash characteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn, and others. Ligands may include hydrocarbyl derivative of alcohols, polyols, glycerols, partial ester glycerols, thiols, carboxylates, carbamates, thiocarbamates, dithiocarbamates, phosphates, thiophosphates, dithiophosphates, amides, imides, amines, thiazoles, thiadiazoles, dithiazoles, diazoles, triazoles, and other polar molecular functional groups containing effective amounts of O, N, S, or P, individually or in combination. In particular, Mo-containing compounds can be particularly effective such as for example Mo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines, Mo (Am), Mo-alcoholates, Mo-alcohol-amides, etc. See USP 5,824,627 ; USP 6,232,276 ; USP 6,153,564 ; USP 6,143,701 ; USP 6,110,878 ; USP 5,837,657 ; USP 6,010,987 ; USP 5,906,968 ; USP 6,734,150 ; USP 6,730,638 ; USP 6,689,725 ; USP 6,569,820 ; WO 99/66013 ; WO 99/47629 ; WO 98/26030 .
Ashless friction modifiers may have also include lubricant materials that contain effective amounts of polar groups, for example, hydroxyl-containing hydrocarbyl base oils, glycerides, partial glycerides, glyceride derivatives, and the like. Polar groups in friction modifiers may include hydrocarbyl groups containing effective amounts of O, N, S, or P, individually or in combination. Other friction modifiers that may be particularly effective include, for example, salts (both ash-containing and ashless derivatives) of fatty acids, fatty alcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates, and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides, esters, hydroxy carboxylates, and the like. In some instances fatty organic acids, fatty amines, and sulfurized fatty acids may be used as suitable friction modifiers.
Useful concentrations of friction modifiers may range from about 0.01 wt% to 10-15 wt% or more, often with a preferred range of about 0.1 wt% to 5 wt%. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from about 10 ppm to 3000 ppm or more, and often with a preferred range of about 20-2000 ppm, and in some instances a more preferred range of about 30-1000 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this invention. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

Typical Additive Amounts

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present invention are shown in Table 1 below.

Note that many of the additives are shipped from the manufacturer and used with a certain amount of base oil solvent in the formulation. Accordingly, the weight amounts in the table below, as well as other amounts mentioned in this text unless otherwise indicated, are directed to the amount of active ingredient (that is the non-solvent portion of the ingredient). The wt% indicated below are based on the total weight of the lubricating oil composition.

TABLE 1

Typical Amounts of Various Lubricant Oil Components
	Approximate	Approximate
Compound	Wt% (Useful)	Wt% (Preferred)
Detergent	0.01-6	0.01 - 4
Dispersant	0.1-20	0.1 - 8
Friction Reducer	0.01-5	0.01 - 1.5
Viscosity Improver	0.0-8	0.0 to 4, more preferably 0.0 to 2
Antioxidant	0.0-5	0.0 - 1.5
Corrosion Inhibitor	0.01-5	0.01 - 1.5
Anti-wear Additive	0.01-6	0.01 - 4
Optional Pour Point Depressant	0 - 0.1 (as received)	0 - 0.05 (as received)
Anti-foam Agent	0.001-3	0.001 - 0.15
Base Oil	Balance	Balance

EXAMPLES

In the following Examples, MRV was determined by ASTM D 4684, CCS viscosity by ASTM D 5293, KV by ASTM D 445, pour point by ASTM D 97, and viscosity index by ASTM D 2270.

EXAMPLE 1

A solvent dewaxed base stock (A) was blended with varying amounts (5 wt%, 15 wt% and 25 wt%) of a catalytically dewaxed base stock (B) and formulated to a 5W-30 multi-grade lube oil composition using 10 wt% of a commercially available GF-4 additive package. Base Stock A: a solvent dewaxed base oil having a pour point of -18°C, a KV at 40°C of 20.76 mm²/s, a KV at 100°C of 4.31 mm²/s. Base Stock B: a catalytically dewaxed base oil having a pour point of -18°C, a KV at 40°C of 31.99 mm²/s, a KV at 100°C of 5.58 mm²/s.
The MRV at -35°C and CCS viscosity at -30°C of the formulated 5W-30 oils were measured.
For comparison a variety of solvent dewaxed base stocks of different pour points and viscosities (base stocks A, C and D) were combined with 15 wt% of a second solvent dewaxed base stock (base stock E). The base stocks are characterized as follows: Base Stock C: a solvent dewaxed base oil having a pour point of -21°C, a KV at 40°C of 22.83 mm²/s, a KV at 100°C of 4.57 mm²/s; Base Stock D: a solvent dewaxed base oil characterized by a pour point of -21°C, a KV at 40°C of 23.32 mm²/s, a KV at 100°C of 4.64 mm²/s; Base Stock E: a solvent dewaxed base oil having a pour point of -18°C, a KV at 40°C of 34.87 mm²/s, a KV at 100°C of 5.91 mm²/s, all oil mixtures being formulated with 10 wt% of the same commercially available GF-4 additive package.
Base stock B (catalytically dewaxed) and Base stock E (solvent dewaxed) are analytically similar in terms of pour point (-18°C) and KV at 40°C (31.9 mm²/s vs. 34.9 mm²/s) and KV at 100°C (5.58 mm²/s vs. 5.91 mm²/s).
Solvent dewaxed base stock E was added in an amount of about 15 wt% to each of solvent dewaxed base stocks A, C and D, while 5 wt%, 15 wt% and 25 wt% of base stock B was added to Base stock A. The MRV and CCS viscosity of all the above formulations results are plotted on Figure 1.
Only the combination of Base stock A (solvent dewaxed) plus Base stock B (catalytically dewaxed) exhibited a superior MRV/CCS viscosity relationship (MRV went down as CCS viscosity went up but stayed below the 5W-X CCS viscosity ceiling limit of 6600 cp @ -30°C) whereas the other combinations (solvent dewaxed base oils plus solvent dewaxed base oil E) exhibited significantly inferior MRV/CCS relationship (both MRV and CCS viscosity went up).
Thus even addition of as little as 15% of catalytically dewaxed Base stock (Base stock B) significantly and unexpectedly improved the MRV/CCS viscosity relationship.
Some of the mixtures identified above (containing GF-4 additive package) are reported in Table 2 which show that blending higher quantities of catalytically dewaxed Base Stock B with solvent dewaxed Base Stock A resulted in an increase in CCS viscosity (but still below maximum ceiling limit) but resulted in further lowering of the MRV viscosity. TABLE 2

Amount of Base Stock B in Base Stock A (wt%) 5 15 25

MRV viscosity, cP at -35°C 24627 21268 19841

CCS viscosity, cP at -30°C 4720 4990 5240

Reference to Table 3 shows that when a commercial oil formulation utilizing a single base oil having a KV at 100°C of 4.64 mm²/s is compared against a formulated oil of the present invention made utilizing a mixture of solvent dewaxed base oil (Base oil A) plus a catalytically dewaxed base oil (Base oil B) blended to a KV at 100°C of 4.58 mm²/s (similar to the KV of the commercial oil) both the MRV and the CCS viscosity are significantly improved. While the high temperature viscometrics and VI are substantially similar the formulated oil MRV and CCS viscosity are strikingly different.

TABLE 3

Component or base stock inspections	Commercial (single base oil)	Invention *	Base stock A per se	Base stock B per se
KV at 40°C	23.31	22.94	20.76	28.94
KV at 100°C	4.64	4.58	4.3	5.28
VI	115	115	115	116
CCS at -25°C	1630	1550	N/A	N/A
5W-30 MRV at -35°C, cP	29,075	19,841	N/A	N/A
5W-30 CCS at -30°C, cP	5,650	5,240	N/A	N/A
Pour point	-22	-18	-18	-18
Noack	15	15	16	14

* 25 wt% Base Stock B in Base Stock A (+ 10 wt% GF4 adpack)

EXAMPLE 2

In the absence of flow or pour point improver, preparing a base oil from a mixture of base stocks produced by different final wax processing routes or one processed by a final wax processing route and a second produced by a separate synthesis route (i.e., PAO) results in a decrease in MRV, while blends made to the same nominal high temperature viscosity targets but using two base stocks made by the same final wax processing route failed to demonstrate this improvement (see Table 4).

TABLE 4

Blend ID	I	II	III	IV	V	VI	VII	VIII	IX
Component (wt% additive package) (in PAO diluent oil)	21.56	22.78	22.93	22.79	21.56	22.49	22.54	22.49	22.63
GTL 4 pour point -27°C (3.66 mm²/s)	33.73	48.65	40.85	42.47	--	--	--	--	--
GTL 6 pour point -18°C (5.97 mm²/s)	44.71	--	--	--	--	--	--	--	--
NEXBASE 3060, pour point -15°C (5.97 mm²/s)	--	28.57	--	--	--	23.25	--	--	--
NEXBASE 3050 (5.08 mm²/s), pour point-12°C	--	--	36.22	--	--	--	34.08	--	--
PAO 6, pour point <-50	--	--	--	34.74	--	--	--	28.68	22.44
PAO 4, pour point <-50	--	--	--	--	--	--	--	--	54.93
Hydroisomerized slack wax, pour point -18°C (4.01 mm²/s)	--	--	--	--	47.85	54.26	43.38	48.83	--
Hydroisomerized slack wax ibid, pour point -18°C (6.62 mm²/s)	--	--	--	--	30.59	--	--	--	--
Kinematic viscosity at 100°C (ASTM D445) mm²/s	10.6	10.6	10.6	10.7	10.88	10.81	10.80	10.85	10.80
CCS viscosity at -30°C (ASTM D5293)cP	3448	3708	3649:	3179	4160 (calculated)	3970 (calculated)	4170 (calculated)	3390 (calculated)	3210 (calculated)
MRV at -35°C	37,706	22,962	23,629	9,234	--	--	--	--	--
(ASTM D4684) yield stress pascals	< 175	NYS	<70	NYS	--	--	--	--	--
CCS viscosity at -35°C (ASTM D5293)cP	5760 (calculated)	6260 (calculated)	6140 (calculated)	5264 (calculated)	7082	6724	7099	5637	5319
MRV at -40°C (ASTM.D4684) yield stress (pascals)	199,600 < 70	81,612 < 140	71,476 < 105	20,238 NYS	386,000 90	64,900 40	46,300 20	25,800 NYS	17,500 NYS
NOACK	11	12	12	12	12	12	12	12	12

Table 4 shows the results for GTL base stocks and slack wax hydrodewaxate base stocks as well as for Group III base stock (NEXBASE which are hydrodewaxed waxy oil stock made via a process which employs a different catalyst than that used to make the GTL base stock or slack wax hydrodewaxate base stocks). All oils in Table 4 are formulated oils containing substantially the same amounts of an additive package but no flow improver or pour point depressant.
Formulated oils I-IV met the same KV at 100°C target of about 10.7 mm²/s, and exhibited similar CCS viscosities at -30°C within the limits of the repeatability of the test.
At -35°C, in the absence of low temperature flow improver/pour point depressant, a mixture of 2 GTL stocks each made by the same hydrodewaxing technique, Formulation 1, passed MRV with respect to viscosity, but failed with very high yield stress. Replacing the GTL 6 with Nexbase 3060 (hydrodewaxed waxy oil made by a hydrodewaxing process which employs a different catalyst than that used to make the GTL stocks (Formulation II)) reduced MRV at -35°C to 22,962 cP (about 15,000 cP lower than in Formulation I), and also reduced the yield stress to the point of NYS (no yield stress), indicating that the formulation would meet the target properties for a 5W-30 oil. Replacement of GTL 6 with Nexbase 3050 (Formulation III) also reduced the MRV at -35°C as well as significantly reducing yield stress resulting in an oil formulation which would meet 5W-30 specifications with the addition of minimal pour point depressant (to address yield stress).
At -40°C, in the absence of low temperature flow improver/pour point depressant, Formulation 1 failed both MRV and yield stress. Replacing GTL 6 with Nexbase 3060 or 3050 (Formulations II and III) reduces the MRV by more than half, but yield stress remains high for a 0W-X grade formulation.
Formulated oils V to IX met the same KV at 100°C target of about 10.8 mm²/s.
At -40°C, Formulation V (mixture of two hydrodewaxed slack wax base oils produced by the same hydrodewaxing process (but of different viscosities)) failed MRV and yield stress by such wide margins that it would not be expected that the formulation could be made to meet MRV or yield stress target specification by the additive of any amount of a PPD. Replacing the heavier hydrodewaxed slack wax base oil with Nexbase 3060 (oil made by a hydrodewaxing process which employs a different catalyst than that used to make the hydrodewaxed slack wax base oil) (Formulation VI) significantly reduces MRV and yield stress which while just missing the 0W target specification for MRV and yield stress would be expected to be brought into specification by the addition of a minimal amount of pour point depressant. Formulation VI would be expected to meet the less severe 5W specification for MRV and yield stress without the addition of any pour point depressant. Substituting Nexbase 3050 for Nexbase 3060 (Formulation VII) further reduces MRV and yield stress, yielding a formulation easily meeting 0W and implicitly also the less demanding 5W specifications.
Formulations utilizing mixtures of base oils produced by different final wax processing routes exhibit MRV, CCS and yield stress characteristics approaching those exhibited by pure PAO based formulations (Formulation IX) or those containing PAO as a component (Formulation IV and VIII).
Thus it is seen that formulated oils meeting the MRV and CCS viscosity targets of SAE 0W-X or 5W-X multi grade engine oils can be produced by using two oils of the same or similar viscosity produced by different final wax producing techniques (Formulations II, III, VI, VII) without the addition of a PPD or which came close enough to the target MRV and CCS viscosity targets of SAE 0W-X or 5W-X multi grade engine oils (evidenced by a significant reduction in MRV and almost passing the yield stress target), that the addition of a minimal amount of PPD would bring the formulation into specification. Such formulation approach the performance of formulations containing PAO (pour point < -50°C) (formulations IV, VIII and IX) without resort to such synthetic oils.

These results are unexpected in view of the calculated base oil physical properties for the mixtures of base stocks used in the above blends but in the absence of additives, Table 5.

TABLE 5

Blends	I	II	III	IV	V	VI	VII	VIII	IX
KV at 100°C (mm²/s)	4.82	4.34	4.25	4.45	4.83	4.49	4.44	4.57	4.46
CCS at -35°C	2340	2340	2320	2340	2580	2400	2530	2390	2020
Noack (%)	11	12	12	12	12.4	12.4	12.4	12.4	12.4

Claims

A method for producing a base oil, for use as the base oil in the formulation of 0W-X or 5W-X multi-grade engine oils, meeting, when formulated:
- a NOACK volatility of 15% or less,

- according to Society of Automotive Engineers (SAE) Surface Vehicle Standard J300,
o a 0W-X specification of cold cranking simulator (CCS) viscosity at -35°C of 6200 cP or less and of mini rotary viscometer test (MRV) at -40°C of 60,000 cP or less, or

o a 5W-X specification of CCS viscosity at -30°C of 6600 cP or less and of MRV at -35°C of 60,000 cP or less, and

- a yield stress of less than 35 pascals
said method comprising mixing at least two base oils wherein:
- one base oil is solvent dewaxed using a single solvent dewaxing process technique and the second base oil is catalytically dewaxed using a single catalytic dewaxing process technique,

- each base oil individually making up the mixture has a kinematic viscosity at 100°C in the range of 3.5 to 7.0 mm²/s, the mixture itself, without additives, having a kinematic viscosity at 100°C in the range of 4 to 6 mm²/s and

- the pour point of each base oil in the mixture, without additive, is -30°C or higher, provided that as compared to the temperature at which the MRV is measured for each engine oil grade the difference between the pour point of the oil mixture and the temperature of measurement of the MRV of the formulated oil is at least 10°C, and

- the amount of catalytically dewaxed oil combined with the solvent dewaxed oil ranges from 5 to 35 wt%.
The method of claim 1 wherein each base oil individually has a kinematic viscosity at 100°C in the range of 4 to 7 mm²/s.
The method claim 1 wherein the pour point of each base oil in the mixture is -25°C or higher.
The method of claim 1 wherein the amount of catalytically dewaxed oil combined with the solvent dewaxed oil ranges from 10 to 25 wt%.