TURBINE OIL COMPOSITION METHOD FOR MAKING THEREOF

Abstract

Provided are formulations, methods of making, and methods of using one or more isomerized base oils in a turbine oil composition to enhance thermal and oxidative stability of the oil, as well as to improve the performance of an industrial turbine housing the turbine oil composition. The isomerized base oil having consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M. The turbine oil composition has a viscosity index of greater than about 150.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 11/316,311, filed Dec. 21, 2005. This application claims priority to and benefits from the foregoing, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a turbine oil composition. More specifically, the present invention relates to a turbine oil composition comprising a major amount of one or more Fischer-Tropsch derived-base oils (FTBOs”). That composition has a viscosity index (“VI”) of greater than 150, improved oxidation stability, reduced varnish- and sludge-forming tendencies, improved ability to release entrained air, and reduced tendency to catch fire over corresponding turbine oil compositions comprising the same additives but only non-FTBO.

BACKGROUND

Industrial turbines are used to convert kinetic energy into power. The most common industrial turbines are steam turbines, gas turbines and hydraulic turbines. Though varying considerably in complexity, their basic designs are essentially the same across the turbine types. Accordingly, suitable turbine oils are typically not specifically formulated for a single type of turbine, but rather are generally formulated for multiple types. The turbine oils thus share certain features, such as, for example, the basic capacity to provide reliable lubrication and performance under high operating temperatures for sustained periods of time.

Steam turbines are among the most efficient of heat engines. They are typically used to drive machines such as electric generators, compressors and pumps, by converting the heat of steam to velocity or kinetic energy and then to mechanical energy. Aside from the major components, such as nozzles, valves, turbine blades, exhausts, and bearings, steam turbines also typically comprise a number of auxiliary systems that insure their safe and efficient operation. One of those auxiliary systems is the lubricating oil system, which provides clean, cool lubricating oil to the steam turbine bearings at the correct pressure, temperature, and flow rate. Certain of the steam turbines are equipped with mechanical-hydraulic control systems wherein the lubricating oil systems also lubricate the hydraulics. The exceedingly high operating temperatures and the otherwise harsh conditions in steam turbines place certain taxing demands on the oils, requiring, for example, sufficiently unvaried viscosity throughout the operating temperatures; resistance to fire, oxidation, sludge/varnish formation, and foaming; and anticorrosion properties.

Gas turbines are commonly used in the electrical power industry to drive generators, compressors and pumps by converting part of a fuel's chemical energy into useable mechanical energy. A gas turbine, like a steam turbine, comprises major components and auxiliary systems, with the latter comprising a lubricating oil system in addition to others. In a small number of gas turbines the lubricant oils are insulated from heat, but in a majority of gas turbines, bearings and other major components are exposed to high operating temperatures, and in localized areas, these temperatures can be higher than those found in typical steam turbines. The capabilities of gas turbine oils to rapidly cool the surfaces without catching fire and retaining performance under extreme heat are thus put to the test. Even in the small number of gas turbines where the lubricant oils are not heated, however, oxidative stress remains because turbines typically undergo long periods of operation without oil service. Accordingly, a suitable gas turbine oil, just like a suitable steam turbine oil, should not only provide clean and cool lubrication to the components, but also be fire resistant and impervious or nearly impervious to oxidation, rusting and/or corrosion.

Hydraulic turbines are typically found in hydroelectric power plants, wherein they convert the energy of falling water into mechanical work. In hydraulic turbines, the main parts requiring lubrication are the shaft bearings, the wicket gates, and the inlet valves. The lubricating oil is typically not subject to high temperatures, but its capacity to separate water from oil takes on added importance because of the ever presence of water in the operating environment. Accordingly, a suitable hydraulic turbine oil will have superior water separating capacity as well as the capacity to maintain adequate fluidity at low temperatures. It will also have sufficient capacity to resist rust and corrosion, as well as the capacity to settle harmful water rapidly. Because of the large amounts of water in the environment, a suitable hydraulic turbine oil will have minimum tendency to foam, retain air, and/or form sludge.

Therefore a suitable general-application turbine oil will have a series of desirable properties to accommodate various operating conditions across multiple types of modern industrial turbines. These properties include, for example, sufficiently high VI, adequate oxidation stability (and relatedly, long life), low varnish/sludge formation, high fire resistance, good water-separation capacity, improved rust and/or corrosion resistance, and improved air release and foaming properties.

A turbine oil, like other types of industrial lubricant oils, typically comprises an additive part and a base stock part. Accordingly, satisfactory performance may be conferred by suitable choices of either additives or base stocks. Many known additives have been developed and applied by persons skilled in the lubricant art to individually confer the desired properties listed above, including, for example, viscosity index improvers, corrosion inhibitors, pour point depressants, antioxidants, antifoamants, detergents, and demulsifiers. In the context of turbine oils, however, the extent to which these properties can be improved upon by additives is often limited.

For example, VI improvers, which are typically high molecular weight polymers, are widely used by persons skilled in the art to increase the VI of a lubricating oil. The extent to which the VI can be improved upon using one or more VI improvers is however limited, at least in the context of a turbine oil. This is because large amounts of VI improvers can be prohibitively expensive. Moreover, VI improvers are known to degrade rapidly under the operating conditions of a turbine so that the service life of a turbine oil containing a significant amount of one or more conventional VI improvers may be detrimentally reduced. Consequently, these potential difficulties have prompted some turbine manufacturers to prohibit the use of VI improvers in oils used to lubricate their turbines.

Moreover, various known antioxidants are often blended into lubricant oils to improve the oxidative stability and prolong the service life of the oil. One of the mostly commonly used antioxidants is zinc dihydrocarbyl diphiophospate, a multi-functional additive that possesses not only the antioxidation properties but also antiwear/extreme pressure functionalities. However, these conventional antioxidants are known to be problematic when added to turbine oils because they have a tendency to hydrolyze when exposed to moisture and the hydrolysis products (e.g., zinc oxide and hydroxide) can precipitate. This problem is so severe that many turbine manufacturers place strict limits on the content of zinc in turbine oils, prompting the use of ashless antioxidants in their place. One of the most widely used replacement ashless antioxidants is 2,6-ditertiarybutyl-p-cresol (DBPC or BHT). But BHT is known to have high volatility and it is typically made in solid form, causing difficulties in blending. Aromatic amines tend to be more effective antioxidants at high temperatures than high-molecular-weight hindered phenols, but they can be costly and tend to color the base stock in which they are used, forming deposits if improperly formulated. These antioxidants are also known to be suitable and satisfactory only when used in a limited concentration range and a limited number of base stocks. Other antioxidants, such as phosphites, are known to be sensitive to moisture, resulting in the formation of corrosive acids, and are thus avoided in turbine oils. Accordingly, just like VI improvers can only be used to enhance the performance of a turbine oil somewhat, antioxidants can only enhance its oxidative stability and service life to a limited extent.

To enhance the oxidative stability, metal deactivators are also sometimes used in conjunction to or instead of antioxidants in the art to counteract the catalytic effects from contaminating iron, copper, and/or other transition metals. But as stated in, for example, EP Publication No. 0 316 610 A1, the addition of metal deactivators may decrease the anti-seizure and antiwear properties of the antiwear/extreme pressure agents that can be used in turbine oils. Accordingly, metal deactivators are again only of limited value.

In a further example, to inhibit foam and assist the release of entrained air, persons skilled in the lubricant art typically use one or more antifoamants, which include silicone fluids such as polydimethylsiloxanes. The most active antifoamants are those that are not soluble but dispersible in the oil or fluid because soluble siloxanes do not have the same activity at the air/fluid interface. The resulting difficulties in obtaining a homogenous dispersion can not be ignored, especially when more than a minute amount of siloxanes is used. The polymers tend to accumulate at the surface and then deposit on the walls of the tanks so that overtime the efficiency of the additive is lost. It is also known that, at high concentrations, these antifoamants tend to have an adverse effect on air release properties.

Accordingly, the approach of using additives as the sole means to achieve the desired properties in a turbine oil is inherently limited. Moreover, certain desired properties such as fire resistance cannot be achieved by including additives in an oil. On the other hand, careful selections of base stocks may provide performance improvements in areas where additives cannot.

Prior to the 1980's, solvent-refined hydrocarbon oils were extensively used for both steam and industrial gas turbine applications. In this type of base stock, about 35 to 60% of the hydrocarbons are in the form of saturated straight- or branched-chain paraffins and monocycloparaffins, but there still is a significant amount of unsaturated ring structures. The refining process removes wax (mainly high molecular weight paraffinic compounds), most of the aromatic hydrocarbons, and some of the polar compounds containing oxygen and nitrogen, products that would otherwise significantly reduce stability of the oil. But small amounts of sulfur-containing compounds typically remain, which are known to increase the stability of the base stock. These base stocks are classified as Group I according to the API Classification of Base Oils. An oil in this group typically has a VI of between about 80 to about 120. As operating conditions of industrial turbines became more severe, attention was turned to processes that can remove yet more of the aromatic content and the residual impurities. Since the mid-1980s, oils produced by hydrotreating, hydrocracking or hydro-refining processes have resulted in the availability of much purer base stocks, such as those falling within API Group II (mildly hydrocracked) and/or Group III (severely hydrocracked or hydrotreated). An oil in Group II typically has a VI of about 80 to about 120, while an oil in Group III typically has a VI of above 120 but lower than about 140. These highly refined oils may, however, be less oxidatively stable compared to solvent-refined oils such as those in Group I, because of the removal of sulfur and aromatic compounds during the refining process that otherwise act as naturally occurring stabilizers. The loss of aromatics also results in reduced additive solvency. The loss of sulfur further reduces the anti-wear/extreme pressure properties of these oils although these properties may be improved by incorporating suitable additives. Importantly, any further refinement beyond the extent to which a Group I oil is refined invariably increases the costs associated with production, thus preventing the use of Groups II and III oils in large volumes.

On the other hand, polyalphaolefins (PAOs) are synthetic fluids that have many of the desired properties to be a turbine oil base stock. These oils are manufactured by the oligomerization of alpha-olefins, particularly α-decene, but also by α-octene and α-dodecene. PAOs are free of aromatic hydrocarbons, sulfur, oxygen, and nitrogen compounds, and show excellent response to antioxidants. These oils have higher VIs than Groups I to III base oils. PAOs also have relatively high flash points, typically in the range of 230-235° C., as measured by ASTM D92-05a. They are also known to have good low temperature viscosities, as measured by ASTM D445-06, having a viscosity of 7830 mm²/s at −40° C., a temperature at which other types of base oils would have long since solidified. These oils are further known to have good pour points, and a wide operating temperature range. Despite these advantages, additives can encounter solubility problems when being dissolved into PAOs because of the lack of aromaticity in those base oils. PAOs also have limited dispersency and do not penetrate rubber seals to cause swelling, making it necessary to always blend small amounts of a seal swelling agent to prevent seal leakage. Various viscosity grades of PAOs are available, but even at their lowest viscosity grades, PAOs can be dramatically more expensive than base oils of Groups I to III, and the high costs associated with producing PAOs is one of the most important obstacles that has so far prevented these oils from being widely used as base stocks for turbine oils. Indeed, in a modern industrial turbine, the sump capacity may range from 1,000 gallons to 20,000 gallons, making it prohibitively expensive to fill even 5% of that volume, which is the typical annual makeup rate for replenishing the degradation loss.

Thus it would be advantageous to identify other sources of non-PAO base oils that have similar if not better performance but without the attendant high costs for use in a turbine oil. FTBOs, which have already found use in a divergent array of non-turbine industrial lubricants, may suitably serve this purpose.

For example, a lubricating oil having a kinematic viscosity at 40° C. of from 18 to 60 mm²/s, a VI of from 130 to 150, and a density at 15° C. of from 0.80 to 0.84, was said to be a suitable hydraulic fluid with demonstrated improved efficiency in a hydraulic energy transmission in published U.S. Patent Application 2004/0224860 A1. That lubricating oil composition was said to suppress the formation of sludge and have excellent storage stability, low friction properties, small pressure transmission loss, low supply pressure loss in pipe-work, and low flammability.

In another example, a wide-cut lubricant base stock prepared from hydroisomerizing and catalytically dewaxing a waxy Fischer-Tropsch synthesized hydrocarbon fraction feed was combined with a commercial automotive additive package, yielding a multigrade internal combustion engine crankcase oil in U.S. Pat. No. 6,332,974. That oil had an exemplary VI of as high as 148 and a low pour point. Relatedly, in U.S. Pat. No. 6,610,636, another premium synthetic lubricant was demonstrated to have antiwear properties that are desirable for internal combustion engine oils. That oil comprised a FTBO having an exemplary VI of as high as 138, and at least one antiwear additive.

In U.S. Pat. No. 6,090,758, yet another crankcase oil for internal combustion engines was disclosed to comprise liquid wax isomerate as a base stock, such as one that is synthesized from the Fischer-Tropsch processes. That crankcase oil was again said to have an exemplary VI of as high as 138, a significantly greater VI as compared to an oil prepared from conventional, petroleum derived base stocks, and have improved antifoaming properties.

However, the harsh operating conditions to which a turbine oil is subjected and the large sump volumes place demands on the oil that are very different from those placed on a non-turbine lubricant oil. Various blended oils comprising one or more PAOs in addition to one or more FTBOs have been prepared to achieve VIs as high as greater than 150. For example, in published U.S. Applications 2006/0196807 A1 and 2006/0199743 A1, blended base oils comprising an FTBO and a PAO lubricant base oil were used to achieve superior wear protection, oxygen stability, low pour point, low volatility, and a VI of greater than 140, and more preferably greater than 165. This approach, however, is not favored in view of the potentially dramatic cost increase associated with using even a small amount of PAOs in an oil.

Accordingly, in its broadest embodiment, the present invention pertains to a turbine oil composition comprising a major amount of an FTBO or a blend of more than one FTBOs, and one or more standard turbine oil additive packages, wherein the finished turbine oil composition has a VI of greater than about 150. The present invention also pertains to the method of making and using such a composition. The turbine oil composition provides an economically acceptable and effective means to lubricate a wide spectrum of modern industrial turbines. The VIs of the these turbine oil compositions are typically above about 150, or above about 153, or above about 155, or above about 158, or even above about 160, rendering them suitable for use with steam turbines and gas turbines wherein the bearings are exposed to wide range of temperatures. Compared to turbine oils that comprise only non-FTBOs, the composition also demonstrates improved oxidative stability, which will in turn enhance its service life, making it feasible to change oil less frequently. The composition has an improved flash point, typically above about 236° C., or above about 238° C., or above about 240° C., or above about 245° C., or even above about 250° C., thus rendering a relatively low tendency to catch fire under high temperatures. The oil further possesses improved capacity to release entrained air, thus reducing harmful foaming and sludge formation when water is present as a contaminant in the operation environment, especially when used to lubricate a hydraulic turbine.

SUMMARY

In a first aspect, the present turbine oil composition comprises: a major amount of one or more isomerized base oils; a minor amount of a standard turbine oil additive; wherein the turbine oil composition has a VI of greater than 150.

The turbine oil composition of this aspect may optionally comprise one or more other base oils, so long as those other base oils do not negatively affect the VI, oxidative stability, sludge formation tendency, flash point, and capacity to release entrained air of the turbine oil composition. By “negatively affect,” it is meant that the above-stated properties is to any extent impaired, as measured by art-accepted turbine compressor or bench tests indicating such properties and designed to mimic the conditions under which industrial turbines typically operate.

In a second aspect, the application provides a method of preparing a turbine oil composition of the first aspect.

In a third aspect, the application provides a method of operating an industrial turbine, which method comprises lubricating the bearings and parts of said turbine with a lubricating composition of the first aspect.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.

“Fischer-Tropsch derived” means that the product, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. As used herein, “Fischer-Tropsch base oil” may be used interchangeably with “FT base oil,” “FTBO,” “GTL base oil” (GTL: gas-to-liquid), or “Fischer-Tropsch derived base oil.”

As used herein, “isomerized base oil” refers to a base oil made by isomerization of a waxy feed. In one embodiment, the isomerized base oil is a Fischer-Tropsch derived base oil.

As used herein, a “waxy feed” comprises at least 40 wt % n-paraffins. In one embodiment, the waxy feed comprises greater than 50 wt % n-paraffins. In another embodiment, greater than 75 wt % n-paraffins. In one embodiment, the waxy feed also has very low levels of nitrogen and sulphur, e.g., less than 25 ppm total combined nitrogen and sulfur, or in other embodiments less than 20 ppm. Examples of waxy feeds include slack waxes, deoiled slack waxes, refined foots oils, waxy lubricant raffinates, n-paraffin waxes, NAO waxes, waxes produced in chemical plant processes, deoiled petroleum derived waxes, microcrystalline waxes, Fischer-Tropsch waxes, and mixtures thereof. In one embodiment, the waxy feeds have a pour point of greater than 50° C. In another embodiment, greater than 60° C.

“Kinematic viscosity” is a measurement in mm²/s of the resistance to flow of a fluid under gravity, determined by ASTM D445-06.

“Viscosity index” (VI) is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of the oil. The higher the VI of an oil, the lower its tendency to change viscosity with temperature. Viscosity index is measured according to ASTM D 2270-04.

Cold-cranking simulator apparent viscosity (CCS VIS) is a measurement in millipascal seconds, mPa·s to measure the viscometric properties of lubricating base oils under low temperature and low shear. CCS VIS is determined by ASTM D 5293-04.

The boiling range distribution of base oil, by wt %, is determined by simulated distillation (SIMDIS) according to ASTM D 6352-04, “Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700° C. by Gas Chromatography.”

“Noack volatility” is defined as the mass of oil, expressed in weight %, which is lost when the oil is heated at 250° C. with a constant flow of air drawn through it for 60 min., measured according to ASTM D5800-05, Procedure B.

Brookfield viscosity is used to determine the internal fluid-friction of a lubricant during cold temperature operation, which can be measured by ASTM D 2983-04.

“Pour point” is a measurement of the temperature at which a sample of base oil will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D 5950-02.

“Auto ignition temperature” is the temperature at which a fluid will ignite spontaneously in contact with air, which can be determined according to ASTM E 659 (Rev. 2005).

“Ln” refers to natural logarithm with base “e.”

“Traction coefficient” is an indicator of intrinsic lubricant properties, expressed as the dimensionless ratio of the friction force F and the normal force N, where friction is the mechanical force which resists movement or hinders movement between sliding or rolling surfaces. Traction coefficient can be measured with an MTM Traction Measurement System from PCS Instruments, Ltd., configured with a polished 19 mm diameter ball (SAE AISI 52100 steel) angled at 220 to a flat 46 mm diameter polished disk (SAE AISI 52100 steel). The steel ball and disk are independently measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. The roll ratio is defined as the difference in sliding speed between the ball and disk divided by the mean speed of the ball and disk, i.e. roll ratio=(Speed1−Speed2)/((Speed1+Speed2)−/2).

As used herein, “consecutive numbers of carbon atoms” means that the base oil has a distribution of hydrocarbon molecules over a range of carbon numbers, with every number of carbon numbers in-between. For example, the base oil may have hydrocarbon molecules ranging from C22 to C36 or from C30 to C60 with every carbon number in-between. The hydrocarbon molecules of the base oil differ from each other by consecutive numbers of carbon atoms, as a consequence of the waxy feed also having consecutive numbers of carbon atoms. For example, in the Fischer-Tropsch hydrocarbon synthesis reaction, the source of carbon atoms is CO and the hydrocarbon molecules are built up one carbon atom at a time. Petroleum-derived waxy feeds have consecutive numbers of carbon atoms. In contrast to an oil based on poly-alpha-olefin (“PAO”), the molecules of an isomerized base oil have a more linear structure, comprising a relatively long backbone with short branches. The classic textbook description of a PAO is a star-shaped molecule, and in particular tridecane, which is illustrated as three decane molecules attached at a central point. While a star-shaped molecules is theoretical, nevertheless PAO molecules have fewer and longer branches that the hydrocarbon molecules that make up the isomerized base oil disclosed herein.

“Molecules with cycloparaffinic functionality” mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused multicyclic saturated hydrocarbon group.

“Molecules with monocycloparaffinic functionality” mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons.

“Molecules with multicycloparaffinic functionality” mean any molecule that is a fused multicyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused multicyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons.

Molecules with cycloparaffinic functionality, molecules with monocycloparaffinic functionality, and molecules with multicycloparaffinic functionality are reported as weight percent and are determined by a combination of Field Ionization Mass Spectroscopy (FIMS), HPLC-UV for aromatics, and Proton NMR for olefins, further fully described herein.

Oxidator BN measures the response of a lubricating oil in a simulated application. High values, or long times to adsorb one liter of oxygen, indicate good stability. Oxidator BN can be measured via a Dornte-type oxygen absorption apparatus (R. W. Domte “Oxidation of White Oils,” Industrial and Engineering Chemistry, Vol. 28, page 26, 1936), under 1 atmosphere of pure oxygen at 340° F., time to absorb 1000 ml of O₂ by 100 g. of oil is reported. In the Oxidator BN test, 0.8 ml of catalyst is used per 100 grams of oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oil. The additive package is 80 millimoles of zinc bispolypropylenephenyldithiophosphate per 100 grams of oil.

Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FIMS) and n-d-M analysis (ASTM D 3238-95 (Re-approved 2005) with normalization). In FIMS, the base oil is characterized as alkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations. When olefins are present in significant amounts, they would be identified as 1-unsaturations. The total of the 1-unsaturations, 2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and 6-unsaturations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycloparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycloparaffinic functionality. The total weight percent of molecules with cycloparaffinic functionality is the sum of the weight percent of molecules with monocyclopraffinic functionality and the weight percent of molecules with multicycloparaffinic functionality.

Molecular weights are determined by ASTM D2503-92(Reapproved 2002). The method uses thermoelectric measurement of vapour pressure (VPO). In circumstances where there is insufficient sample volume, an alternative method of ASTM D2502-04 may be used; and where this has been used it is indicated.

Density is determined by ASTM D4052-96 (Reapproved 2002). The sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample. Weight percent olefins can be determined by proton-NMR according to the steps specified herein. In most tests, the olefins are conventional olefins, i.e. a distributed mixture of those olefin types having hydrogens attached to the double bond carbons such as: alpha, vinylidene, cis, trans, and tri-substituted, with a detectable allylic to olefin integral ratio between 1 and 2.5. When this ratio exceeds 3, it indicates a higher percentage of tri or tetra substituted olefins being present, thus other assumptions known in the analytical art can be made to calculate the number of double bonds in the sample. The steps are as follows: A) Prepare a solution of 5-10% of the test hydrocarbon in deuterochloroform. B) Acquire a normal proton spectrum of at least 12 ppm spectral width and accurately reference the chemical shift (ppm) axis, with the instrument having sufficient gain range to acquire a signal without overloading the receiver/ADC, e.g., when a 30 degree pulse is applied, the instrument having a minimum signal digitization dynamic range of 65,000. In one embodiment, the instrument has a dynamic range of at least 260,000. C) Measure the integral intensities between: 6.0-4.5 ppm (olefin); 2.2-1.9 ppm (allylic); and 1.9-0.5 ppm (saturate). D) Using the molecular weight of the test substance determined by ASTM D 2503-92 (Reapproved 2002), calculate: 1. The average molecular formula of the saturated hydrocarbons; 2. The average molecular formula of the olefins; 3. The total integral intensity (=sum of all integral intensities); 4. The integral intensity per sample hydrogen (=total integral/number of hydrogens in formula); 5. The number of olefin hydrogens (=Olefin integral/integral per hydrogen); 6. The number of double bonds (=Olefin hydrogen times hydrogens in olefin formula/2); and 7. The wt % olefins by proton NMR=100 times the number of double bonds times the number of hydrogens in a typical olefin molecule divided by the number of hydrogens in a typical test substance molecule. In this test, the wt % olefins by proton NMR calculation procedure, D, works particularly well when the percent olefins result is low, less than 15 wt %.

Weight percent aromatics in one embodiment can be measured by HPLC-UV. In one embodiment, the test is conducted using a Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid Chromatography (HPLC) system, coupled with a HP 1050 Diode-Array UV-Vis detector interfaced to an HP Chem-station. Identification of the individual aromatic classes in the highly saturated base oil can be made on the basis of the UV spectral pattern and the elution time. The amino column used for this analysis differentiates aromatic molecules largely on the basis of their ring-number (or double-bond number). Thus, the single ring aromatic containing molecules elute first, followed by the polycyclic aromatics in order of increasing double bond number per molecule. For aromatics with similar double bond character, those with only alkyl substitution on the ring elute sooner than those with naphthenic substitution. Unequivocal identification of the various base oil aromatic hydrocarbons from their UV absorbance spectra can be accomplished recognizing that their peak electronic transitions are all red-shifted relative to the pure model compound analogs to a degree dependent on the amount of alkyl and naphthenic substitution on the ring system. Quantification of the eluting aromatic compounds can be made by integrating chromatograms made from wavelengths optimized for each general class of compounds over the appropriate retention time window for that aromatic. Retention time window limits for each aromatic class can be determined by manually evaluating the individual absorbance spectra of eluting compounds at different times and assigning them to the appropriate aromatic class based on their qualitative similarity to model compound absorption spectra. Weight percent aromatic carbon (“Ca”), weight percent naphthenic carbon (“Cn”) and weight percent paraffinic carbon (“Cp”) in one embodiment can be measured by ASTM D3238-95 (Reapproved 2005) with normalization. ASTM D3238-95 (Reapproved 2005) is the Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method. This method is for “olefin free” feedstocks which are assumed in this application to mean that that olefin content is 2 wt % or less. The normalization process consists of the following: A) If the Ca value is less than zero, Ca is set to zero, and Cn and Cp are increased proportionally so that the sum is 100%. B) If the Cn value is less than zero, Cn is set to zero, and Ca and Cp are increased proportionally so that the sum is 100%; and C) If both Cn and Ca are less than zero, Cn and Ca are set to zero, and Cp is set to 100%.

HPLC-UV Calibration. In one embodiment, HPLC-UV can be used for identifying classes of aromatic compounds even at very low levels, e.g., multi-ring aromatics typically absorb 10 to 200 times more strongly than single-ring aromatics. Alkyl-substitution affects absorption by 20%. Integration limits for the co-eluting 1-ring and 2-ring aromatics at 272 nm can be made by the perpendicular drop method. Wavelength dependent response factors for each general aromatic class can be first determined by constructing Beer's Law plots from pure model compound mixtures based on the nearest spectral peak absorbances to the substituted aromatic analogs. Weight percent concentrations of aromatics can be calculated by assuming that the average molecular weight for each aromatic class was approximately equal to the average molecular weight for the whole base oil sample.NMR analysis. In one embodiment, the weight percent of all molecules with at least one aromatic function in the purified mono-aromatic standard can be confirmed via long-duration carbon 13 NMR analysis. The NMR results can be translated from % aromatic carbon to % aromatic molecules (to be consistent with HPLC-UV and D 2007) knowing that 95-99% of the aromatics in highly saturated base oils are single-ring aromatics. In another test to accurately measure low levels of all molecules with at least one aromatic function by NMR, the standard D 5292-99 (Reapproved 2004) method can be modified to give a minimum carbon sensitivity of 500:1 (by ASTM standard practice E 386) with a 15-hour duration run on a 400-500 MHz NMR with a 10-12 mm Nalorac probe. Acorn PC integration software can be used to define the shape of the baseline and consistently integrate.

Extent of branching refers to the number of alkyl branches in hydrocarbons. Branching and branching position can be determined using carbon-13 (¹³C) NMR according to the following nine-step process: 1) Identify the CH branch centers and the CH₃ branch termination points using the DEPT Pulse sequence (Doddrell, D. T.; D. T. Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48, 323ff.). 2) Verify the absence of carbons initiating multiple branches (quaternary carbons) using the APT pulse sequence (Patt, S. L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46, 535ff.). 3) Assign the various branch carbon resonances to specific branch positions and lengths using tabulated and calculated values known in the art (Lindeman, L. P., Journal of Qualitative Analytical Chemistry 43, 1971 1245ff; Netzel, D. A., et.al., Fuel, 60, 1981, 307ff). 4) Estimate relative branching density at different carbon positions by comparing the integrated intensity of the specific carbon of the methyl/alkyl group to the intensity of a single carbon (which is equal to total integral/number of carbons per molecule in the mixture). For the 2-methyl branch, where both the terminal and the branch methyl occur at the same resonance position, the intensity is divided by two before estimating the branching density. If the 4−methyl branch fraction is calculated and tabulated, its contribution to the 4+methyls is subtracted to avoid double counting. 5) Calculate the average carbon number. The average carbon number is determined by dividing the molecular weight of the sample by 14 (the formula weight of CH₂). 6) The number of branches per molecule is the sum of the branches found in step 4. 7) The number of alkyl branches per 100 carbon atoms is calculated from the number of branches per molecule (step 6) times 100/average carbon number. 8) Estimate Branching Index (BI) by ¹H NMR Analysis, which is presented as percentage of methyl hydrogen (chemical shift range 0.6-1.05 ppm) among total hydrogen as estimated by NMR in the liquid hydrocarbon composition. 9) Estimate Branching proximity (BP) by ¹³C NMR, which is presented as percentage of recurring methylene carbons—which are four or more carbons away from the end group or a branch (represented by a NMR signal at 29.9 ppm) among total carbons as estimated by NMR in the liquid hydrocarbon composition. The measurements can be performed using any Fourier Transform NMR spectrometer, e.g., one having a magnet of 7.0 T or greater. After verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons are absent, the spectral width for the ¹³C NMR studies can be limited to the saturated carbon region, 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 25-50 wt. % in chloroform-dl are excited by 30 degrees pulses followed by a 1.3 seconds (sec.) acquisition time. In order to minimize non-uniform intensity data, the broadband proton inverse-gated decoupling is used during a 6 sec. delay prior to the excitation pulse and on during acquisition. Samples are doped with 0.03 to 0.05 M Cr (acac)₃ (tris (acetylacetonato)-chromium (III)) as a relaxation agent to ensure full intensities are observed. The DEPT and APT sequences can be carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals. DEPT is Distortionless Enhancement by Polarization Transfer. The DEPT 45 sequence gives a signal 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, known in the art. It allows all carbons to be seen, but if CH and CH₃ are up, then quaternaries and CH₂ are down. The branching properties of the sample can be determined by ¹³C NMR using the assumption in the calculations that the entire sample was iso-paraffinic.

Oil of Lubricating viscosity. In one embodiment, the turbine oil composition comprises a major amount of one or more base oils. Generally, the total amount of one or more base oils constitutes greater than about 60 wt. %, 70 wt. %, 80 wt. %, 90 wt. %, or 95 wt. % of the finished turbine oil composition (“a major amount”). In one embodiment when a single base oil is present in the turbine oil, that single base oil is an isomerized base oil. When more than one base oils are present, at least one of these base oils is an isomerized base oil.

Isomerized Base Oil Component. In one embodiment, the base oil or blend thereof comprises at least an isomerized base oil which the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”). In another embodiment, the base oil comprises at least an isomerized base oil made from a substantially paraffinic wax feed (“waxy feed”). In a third embodiment, the isomerized base oil comprises mixtures of products made from a substantially paraffinic wax feed as well as products made from a waxy feed from a Fischer-Tropsch process.

Fischer-Tropsch derived base oils are disclosed in a number of patent publications, including for example U.S. Pat. Nos. 6,080,301, 6,090,989, and 6165949, and US Patent Publication No. US2004/0079678A1, US20050133409, US20060289337. The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms including a light reaction product and a waxy reaction product, with both being substantially paraffinic.

In one embodiment the isomerized base oil has consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M with normalization. In another embodiment, the amount of naphthenic carbon is less than 10 wt. %. In yet another embodiment the isomerized base oil made from a waxy feed has a kinematic viscosity at 100° C. between 1.5 and 3.5 mm²/s.

In one embodiment, the isomerized base oil is made by a process in which the hydroisomerization dewaxing is performed at conditions sufficient for the base oil to have: a) a weight percent of all molecules with at least one aromatic functionality less than 0.30; b) a weight percent of all molecules with at least one cycloparaffinic functionality greater than 10; c) a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 20 and d) a viscosity index greater than 28×Ln (Kinematic viscosity at 100° C.)+80.

In another embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of 600-750° F. (315-399° C.) In the process, the conditions for hydroisomerization are controlled such that the conversion of the compounds boiling above 700° F. (371° C.) in the wax feed to compounds boiling below 700° F. (371° C.) is maintained between 10 wt % and 50 wt %. A resulting isomerized base oil has a kinematic viscosity of between 1.0 and 3.5 mm²/s at 100° C. and a Noack volatility of less than 50 weight %. The base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.

In one embodiment the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 1000×(Kinematic Viscosity at 100° C.)^−2.7. In another embodiment, the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 900×(Kinematic Viscosity at 100° C.)^−2.8. In a third embodiment, the isomerized base oil has a Kinematic Viscosity at 100° C. of >1.808 mm²/s and a Noack volatility less than an amount calculated by the following equation: 1.286+20 (kv100)^−1.5+551.8 e^−kv100, where kv100 is the kinematic viscosity at 100° C. In a fourth embodiment, the isomerized base oil has a kinematic viscosity at 100° C. of less than 4.0 mm²/s, and a wt % Noack volatility between 0 and 100. In a fifth embodiment, the isomerized base oil has a kinematic viscosity between 1.5 and 4.0 mm²/s and a Noack volatility less than the Noack volatility calculated by the following equation: 160-40 (Kinematic Viscosity at 100° C.).

In one embodiment, the isomerized base oil has a kinematic viscosity at 100° C. in the range of 2.4 and 3.8 mm²/s and a Noack volatility less than an amount defined by the equation: 900×(Kinematic Viscosity at 100° C.)^−2.8−15). For kinematic viscosities in the range of 2.4 and 3.8 mm²/s, the equation: 900×(Kinematic Viscosity at 100° C.)^−2.8−15) provides a lower Noack volatility than the equation: 160-40 (Kinematic Viscosity at 100° C.)

In one embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized under conditions for the base oil to have a kinematic viscosity at 100° C. of 3.6 to 4.2 mm²/s, a viscosity index of greater than 130, a wt % Noack volatility less than 12, a pour point of less than −9° C.

In one embodiment, the isomerized base oil has an aniline point, in degrees F., greater than 200 and less than or equal to an amount defined by the equation: 36×Ln(Kinematic Viscosity at 100° C., in mm²/s)+200.

In one embodiment, the isomerized base oil has an auto-ignition temperature (AIT) greater than the AIT defined by the equation: AIT in ° C.=1.6×(Kinematic Viscosity at 40° C., in mm²/s)+300. In a second embodiment, the base oil as an AIT of greater than 329° C. and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C., in mm²/s)+100.

In one embodiment, the isomerized base oil has a relatively low traction coefficient, specifically, its traction coefficient is less than an amount calculated by the equation: traction coefficient=0.009×Ln (kinematic viscosity in mm²/s)−0.001, wherein the kinematic viscosity in the equation is the kinematic viscosity during the traction coefficient measurement and is between 2 and 50 mm²/s. In one embodiment, the isomerized base oil has a traction coefficient of less than 0.023 (or less than 0.021) when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a traction coefficient of less than 0.017 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a viscosity index greater than 150 and a traction coefficient less than 0.015 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40 percent.

In some embodiments, the isomerized base oil having low traction coefficients also displays a higher kinematic viscosity and higher boiling points. In one embodiment, the base oil has a traction coefficient less than 0.015, and a 50 wt % boiling point greater than 565° C. (1050° F.). In another embodiment, the base oil has a traction coefficient less than 0.011 and a 50 wt % boiling point by ASTM D 6352-04 greater than 582° C. (1080° F.).

In some embodiments, the isomerized base oil having low traction coefficients also displays unique branching properties by NMR, including a branching index less than or equal to 23.4, a branching proximity greater than or equal to 22.0, and a Free Carbon Index between 9 and 30. In one embodiment, the base oil has at least 4 wt % naphthenic carbon, in another embodiment, at least 5 wt % naphthenic carbon by n-d-M analysis by ASTM D 3238-95 (Reapproved 2005) with normalization.

In one embodiment, the isomerized base oil is produced in a process wherein the intermediate oil isomerate comprises paraffinic hydrocarbon components, and in which the extent of branching is less than 7 alkyl branches per 100 carbons, and wherein the base oil comprises paraffinic hydrocarbon components in which the extent of branching is less than 8 alkyl branches per 100 carbons and less than 20 wt % of the alkyl branches are at the 2 position. In one embodiment, the FT base oil has a pour point of less than −8° C.; a kinematic viscosity at 100° C. of at least 3.2 mm²/s; and a viscosity index greater than a viscosity index calculated by the equation of =22×Ln (kinematic viscosity at 100° C.)+132.

In one embodiment, the base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. In another embodiment, the isomerized base oil has a kinematic viscosity between about 8 and about 25 mm²/s and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.

In one embodiment, the isomerized base oil is obtained from a process in which the highly paraffinic wax is hydroisomerized at a hydrogen to feed ratio from 712.4 to 3562 liter H₂/liter oil, for the base oil to have a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15. In another embodiment, the base oil has a viscosity index greater than an amount defined by the equation: 28×Ln (Kinematic viscosity at 100° C.)+95. In a third embodiment, the base oil comprises a weight percent aromatics less than 0.30; a weight percent of molecules with cycloparaffinic functionality greater than 10; a ratio of weight percent of molecules with monocycloparaffinic functionality to weight percent of molecules with multicycloparaffinic functionality greater than 20; and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+110. In a fourth embodiment, the base oil further has a kinematic viscosity at 100° C. greater than 6 mm²/s. In a fifth embodiment, the base oil has a weight percent aromatics less than 0.05 and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+95. In a sixth embodiment, the base oil has a weight percent aromatics less than 0.30, a weight percent molecules with cycloparaffinic functionality greater than the kinematic viscosity at 100° C., in mm²/s, multiplied by three, and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil contains between 2 and 10 wt % naphthenic carbon as measured by n-d-M. In one embodiment, the base oil has a kinematic viscosity of 1.5-3.0 mm²/s at 100° C. and 2-3 wt % naphthenic carbon. In another embodiment, a kinematic viscosity of 1.8-3.5 mm²/s at 100° C. and 2.5-4 wt % naphthenic carbon. In a third embodiment, a kinematic viscosity of 3-6 mm²/s at 100° C. and 2.7-5 wt % naphthenic carbon. In a fourth embodiment, a kinematic viscosity of 10-30 mm²/s at 100° C. and between greater than 5.2% and less than 25 wt % naphthenic carbon.

In one embodiment, the isomerized base oil has an average molecular weight greater than 475; a viscosity index greater than 140, and a weight percent olefins less than 10. The base oil improves the air release and low foaming characteristics of the mixture when incorporated into the turbine oil composition.

In one embodiment, the isomerized base oil is a white oil as disclosed in U.S. Pat. No. 7,214,307 and US Patent Publication US20060016724. In one embodiment, the isomerized base oil is a white oil having a kinematic viscosity at 100° C. between about 1.5 cSt and 36 mm²/s, a viscosity index greater than an amount calculated by the equation: Viscosity Index=28×Ln(the Kinematic Viscosity at 100° C.)+95, between 5 and less than 18 weight percent molecules with cycloparaffinic functionality, less than 1.2 weight percent molecules with multicycloparaffinic functionality, a pour point less than 0° C. and a Saybolt color of +20 or greater.

In one embodiment, the composition comprises at least an isomerized base oil in a major amount (i.e., an amount greater than about 50 wt. %). Generally, the total amount of isomerized base oils is greater than about 60 wt. %, or greater than about 70 wt. %, or greater than about 80 wt. % of the turbine oil composition. In yet another embodiment, the turbine oil composition comprises about 79 wt. % of a base oil mixture, which in turn comprises two different isomerized base oils.

If two or more isomerized base oils are blended into one base oil mixture, the amounts of each isomerized base oil can be in any proportion so that the finished oil has the desired viscosity and VI, as described herein. When two isomerized base oils are blended into one base oil mixture, for example, that proportion may be from 10:90 to 90:10, or from 20:80 to 80:20, such as from 30:70 to 70:30. An exemplary composition comprises two isomerized base oils blended in a proportion of about 35:65, yielding a kinematic viscosity of about 30 mm²/s at 40° C., and a VI of about 160.

In one embodiment, the turbine oil composition comprises two isomerized base oils, the first having a pour point of about −18° C., and the second having a pour point of about −13° C. In yet another embodiment, the composition comprises two isomerized base oils, with the first having a cloud point of about −12° C., and the second having a cloud point of about 5° C.

In one embodiment for general application in a non-turbine equipment, it is desired that the Oxidator BN of a lubricant base oil be greater than about 7 hours. In another embodiment for a turbine oil, it is often desired that the Oxidator BN of the base oil be at or above about 30 hours. In one embodiment, the composition comprises an isomerized base oil having Oxidator BN of about 44 hours. Another exemplary isomerized base oil in yet another embodiment has an Oxidator BN of about 45.4 hours.

Other Non-Isomerized Base Oil Components (“Non-FTBO”). In one embodiment, the composition employs a base oil that consists of at least one of the isomerized base oils described above. In another embodiment, the composition consists essentially of at least a Fischer-Tropsch base oil. In yet another embodiment, the composition employs at least a Fischer-Tropsch base oil and one or more additional base oils selected from: natural oils, synthetic oils, and mixtures thereof, provided that the finished turbine oil has a VI of greater than 150. Moreover, if one or more additional base oils (i.e., other than the isomerized base oils) are present, these additional base oils do not negatively affect the improvements conferred by the isomerized base oils in VI, oxidative stability, fire resistance, air release capacity, and foam- and sludge-forming tendencies.

The natural oils that are suitable include animal oils and vegetable oils (e.g., castor oil, lard oil). The natural oils may also include mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types. Oils derived from coal or shale are also useful.

Synthetic non-FTBOs include alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by a process such as esterification or etherification. Examples of these synthetic oils include polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol ether having a molecular weight of 1000 Daltons or diphenyl ether of poly-ethylene glycol having a molecular weight of 1000 to 1500 Daltons); and mono- and polycarboxylic esters thereof (e.g., acetic acid esters, mixed C₃-C₈ fatty acid esters, and C₁₃ Oxo acid diester of tetraethylene glycol). Other suitable synthetic oils include polyisobutenes, and alkylated aromatics such as alkylated naphthalenes.

Another suitable class of synthetic lubricating oils are the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Specific examples of such esters includes dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid and the like. Esters useful as synthetic oils also include those made from C₅ to C₁₂ monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.

The synthetic oil can also be a poly-alpha-olefin (PAO) when used in a very small amount. Typically, the PAOs are derived from monomers having from 4 to 30, or from 4 to 20, or from 6 to 16 carbon atoms. Examples of useful PAOs include those derived from α-octene, α-decene, mixtures thereof, and the like. Mixtures of mineral oil with one or more of the foregoing PAOs may also be used. Regardless whether a single PAO or a mixture of PAOs is used, however, the total amount should be kept relatively low, such as less than about 10 wt. %, or less than about 5 wt. %, or less than about 2 wt. %, or even less than about 1 wt. %, such as less than about 0.1 wt. %, so as to provide a turbine oil of low cost.

Unrefined, refined and rerefined oils, either natural or synthetic (as well as mixtures of two or more) of the types of oils disclosed above can be used in the lubricating compositions. Unrefined (or raw) oils are those obtained directly from a natural or synthetic source without further purification treatment. Refined oils are similar-to the unrefined oils except they have been further treated in one or more purification steps. Many such purification techniques are known to those skilled in the art such as solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, and the like. Rerefined oils are oils that have been used in service but are subsequently treated so that they may be re-applied in service. Because the used oils almost always contain spent additives and breakdown products, in addition to the standard oil refining steps, steps that would remove the spent additives and breakdown products must be taken. Such rerefined oils are also known as reclaimed or reprocessed oils.

Standard Turbine Oil Additive Packages The turbine oil composition may further comprise an effective amount of one or more standard turbine oil additive packages in an amount of 5-40 wt. % of the finished turbine oil composition (“a minor amount”). Many of those packages are known and commercially available. Each of these packages typically comprise one or more antioxidants, one or more rust/corrosion inhibitors, and one or more antifoamants, and one or more other additives including, for example, viscosity index improvers, wear inhibitors, and/or demulsifiers.

Antioxidants Antioxidants are chemicals that reduce the tendency of mineral oils to deteriorate in service. They extend the life of the lubricant fluid by interrupting the oxidation process, e.g., by decomposing hydroperoxide intermediates (ROOH, where R is an alkyl chain) and scavenging free radicals. One known type of antioxidants are alkaline earth metal salts of alkylphenolthioesters having preferably C₅ to C₁₂ alkyl side chains, calcium nonylphenol sulfide, oil soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons or esters, phosphorous esters, metal thiocarbamates, oil soluble copper compounds as described in, for example, U.S. Pat. No. 4,867,890.

Different types of zinc dialkyldithiophosphates or zinc diaryldithiophosphates are available depending on the alcohol or phenol used in their manufacture, and the hydrocarbyl group present strongly influences their activity: the greater the thermal stability of the product, the lower the antioxidant activity. But as stated above, there has been a move away from using this type of antioxidants at least in turbine oils because they are sensitive to moisture and the hydrolysis products and can precipitate in the presence of water. Another type of common antioxidants is 2,6-ditertiarybutyl p-cresol (also known as DBPC or BHT), but because of its high volatility and solid form, it is included in only a limited number of additive packages.

Higher molecular weight products, such as aromatic amines and hindered phenols, have been introduced to replace the BHT, with the former generally being more active than the latter. In particular, the alkylated derivatives of aromatic amines are known to be effective at high temperatures. Typical oil soluble aromatic amines having at least two aromatic groups attached directly to one amine nitrogen contain from 6 to 16 carbon atoms. The amines may contain more than two aromatic groups. The aromatic rings are often substituted by one or more substituents selected from, for example, alkyl, cycloalkyl, alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups. In addition to their capacity to reduce fluid viscosity and acidity, which are the two most common indicators of oxidation, they are able to control deposit formation on hot surfaces, thus reducing the risk of an engine failure as a result of deposits. Aromatic amines are sometimes used with phenothaizine derivatives (e.g., a sulfur-containing antioxidant) in aviation turbine oils. Certain amines or synergistic mixtures of amines and phenols are known to be highly cost effective antioxidants, but large amounts of these materials are known to form deposits during oxidation and color the finished lubricant. These mixtures are thus typically used in small amounts if they are included in an additive package.

Rust and Corrosion Inhibitors Rust is a continuing problem in turbines where carbon steel is present because water contamination can be difficult to avoid, especially in steam turbines and hydraulic turbines. Acid is also almost always present in degraded oils and can attack metals. In order to avoid rusting and corrosion, certain chemicals have been found to protect the metal surfaces. For steel, for example, such inhibitors are usually highly polar materials such as organic acids, esters or amides, which form an adsorbed film on the surface of the metal that physically hinders the transfer of water to the surface. Because of this mode of action, careful formulation is called for to avoid interaction with other surface-active materials such as antiwear additives, and to minimize the impact on foaming/air release properties. Moreover, some if not most of the industrial turbines operate in saline environments. Rust protection is often necessary against salt water, which is a substantially more severe requirement than the mere protection against distilled water.

In addition to steel, other metals are susceptible to attack from degraded oils or other additives, such as sulfur-containing antiwear/extreme-pressure additives. Of these other metals, copper is the most important, not only because of its common use in constructing industrial turbines but also because it may catalyze the breakdown of oils and fluids when present in soluble salt forms at very low concentrations. This can result in the formation of sulfide-containing deposits. Certain chemicals called “metal passivators” are known to prevent this type of copper corrosion. Metal passivators are typically of the triazole family.

Rust inhibitor or anticorrosion agents may be a nonionic polyoxyethylene surface active agent. Nonionic polyoxyethylene surface active agents include, but are not limited to, polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and polyethylene glycol monooleate. Rust inhibitors or anticorrosion agents may also be other compounds, which include, for example, stearic acid and other fatty acids, dicarboxylic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohols, and phosphoric esters.

Antifoamants The inhibition of foaming is of particular importance when lubricating industrial turbines, especially in hydraulic turbines wherein the turbine oils not only serve to lubricate the system and but also to transmit power in the presence of a great deal of water. It is also known that the stability of foam increases when more additives are added to an oil. Although turbine oils are typically not heavily additized for this very reason, a small amount of one or more antifoamants is typically included in turbine additive packages. Various known foam inhibitors can service this purpose, including, for example, dimethylsiloxane polymers, alkylmethacrylate copolymers, alkylacrylate copolymers and others. Typically these compounds have borderline solubility in lubricating oils, and function by reducing the surface tension at the interface of the air bubble, thus allowing the bubble to burst more easily. To function effectively they are usually present at very low levels, such as at or below about 30 ppm, or about 25 ppm, or about 20 ppm, or even about 10 ppm, because at higher levels the solubility becomes an issue, manifested by an increase in the cloudiness of the lubricant, and in more extreme cases, by the formation of floating debris or precipitation. The effectiveness of an antifoamant can be determined according to the ASTM D892-06, which uses air flowing through a porous ball to create foam in the test oil sample. The amount of foam and its stability are measured at 24° C. and 94° C. A variation of this test, ASTM D6082-06, can also be used to measure foaming at 150° C.

Detergents/Dispersants Compared to other industrial oils, turbine oils tend not to be heavily additized with detergents or dispersants because of the need to allow solid particles to settle rather than suspend so that they may be removed through sump drain or kidney loop filtration systems that are typically present in industrial turbines. This however does not mean that the turbine oil cannot comprise metal-containing detergents or ashless dispersants. If present, the amount of detergents and/or dispersants in the turbine oil should be sufficiently low so that the capacity of the oil to settle solid particles and/or contaminants and other properties of the oil is not negatively affected. Metal-containing or ash-forming detergents function both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear and corrosion and extending engine life. Detergents generally comprise a polar head with long hydrophobic tail, with the polar head comprising a metal salt, and especially an overbased salt, of an acid organic compound. Overbased salts, or overbased materials, are single phase, homogeneous Newtonian systems characterized by a metal content in excess of that which would be present according to the stoichiometry of the metal and the particular acidic organic compound reacted with the metal. The overbased materials are prepared by reacting an acidic material (typically an inorganic acid or lower carboxylic acid, preferably carbon dioxide) with a mixture comprising an acidic organic compound, in a reaction medium comprising at least one inert, organic solvent (such as mineral oil, naphtha, toluene, xylene) in the presence of a stoichiometric excess of a metal base and a promoter. Methods of preparing various detergents, such as the carboxylates, the phenates, and the sulfonates, are known in the art. Suitable detergents may also be sulfurized, the processes of which are known also to those skilled in the art. Since steam turbine oils are likely to interact with water, having good water separability is desirable. In some embodiments, excess usage detergents may destroy water separability, thus water separability property should be balanced with the desirable properties obtained with the use of dispersant and detergents.

Other Additives Other additives may be incorporated into the compositions to satisfy particular performance requirements. Examples of such other additives include, for example, seal fixes or seal pacifiers, VI improvers, friction modifiers. Detergents/dispersants are rarely if ever employed in turbine oils, and even when employed, the amounts of such additives are kept sufficiently low so that the capacity of the oil to settle solid particles and/or contaminants and other properties of the oils, such as water separability, are not negatively affected.

In one embodiment, standard turbine oil additive packages may also comprise antiwear/extreme pressure additives and demulsifiers. Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and antioxidant agents. The metal may be an alkali or alkaline earth metal, or aluminum, lead, tin, molybdenum, manganese, nickel or copper. The zinc salts are the most commonly used in non-turbine lubricating oil. In turbine oils, however, this amount of such salts may be substantially reduced because of their tendency to hydrolyze when exposed to moisture, and the hydrolysis products (e.g., zinc oxide and hydroxide) can precipitate.

These salts may be prepared in accordance with known techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA), usually by reaction of one or more alcohol or a phenol with P₂S₅, and then neutralizing the formed DDPA with a zinc compound. Specifically, oil-soluble zinc dialkyldithiophosphates may be produced from dialkykyldithiophosphoric acids of the formula:
The hydroxyl alkyl compounds from which the dialkyldithiophosphoric acids are derived can be represented generically by the formula ROH or R′OH, wherein R or R′ is alkyl or substituted alkyl, preferably branched or non-branched alkyl containing 3 to 30 carbon atoms. More preferably, R or R′ is a branched or non-branched alkyl containing 3 to 8 carbon atoms. Mixtures of hydroxyl alkyl compounds may also be used. These hydroxyl alkyl compounds need not be monohydroxy alkyl compounds. The dialkyldithiophosphoric acids may thus be prepared from mono-, di-, tri-, tetra-, and other polyhydroxy alkyl compounds, or mixtures of two or more of the foregoing. The phosphorus pentasulfide reactant used in the dialkyldithiophosphoric acid formation step may contain minor amounts of any one or more of P₂S₃, P₄S₃, P₄S₇, or P₄S₉. Compositions as such may also contain minor amounts of free sulfur.

A small amount of one or more VI improvers may also be included in the additive packages. Generally, polymeric materials useful as VI improvers are those having number average molecular weights (Mn) of from about 5,000 to about 250,000, preferably from about 15,000 to about 200,000, more preferably from about 20,000 to 150,000 Daltons. The oil temperature controls coiling of the polymer molecules, which in turn controls the degree to which the polymers increase viscosity. The higher the temperature, the less the coiling and the greater the “thickening” effect of the polymer. Thus, as temperature increases, there is less thinning of the lubricant compared to VI improver-containing oils. These VI improvers can optionally be grafted with grafting materials such as, for example, maleic anhydride, and the grafted material can be reacted with, for example, amines, amides, nitrogen-containing heterocyclic compounds or alcohol, to form multifunctional viscosity improvers (dispersant-viscosity modifiers).

Because of the high costs of known viscosity index improvers, and because of their sensitivity to high temperature or otherwise harsh conditions, the amount of these materials that may be included in a turbine oil is heavily limited. For example, the amount of the viscosity index modifiers in the turbine oils may be below about 5 wt. %, or below about 3 wt. %, or below about 1 wt. %, or even below about 0.1 wt. %, based on the total weight of the finished turbine oil.

The additive packages may further comprise a sulfur-containing molybdenum compound. Certain sulfur-containing organo-molybdenum compounds are known to function as friction modifiers in lubricating oil compositions, while also providing antioxidant and antiwear credits to a lubricating oil composition. Examples of such oil soluble organo-molybdenum compounds include dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates, sulfides, and the like, and mixtures thereof. Methods of preparing these compounds are known in the art.

Seal fixes are also termed seal swelling agents or seal pacifiers. They are often employed in lubricant or additive compositions to insure proper elastomer sealing, and prevent premature seal failures and leakages. Seal swell agents may be, for example, oil-soluble, saturated, aliphatic, or aromatic hydrocarbon esters such as di-2-ethylhexylphthalate, mineral oils with aliphatic alcohols such as tridecyl alcohol, triphosphite ester in combination with a hydrocarbonyl-substituted phenol, and di-2-ethylhexylsebacate.

Some of the above-mentioned additives can provide a multiplicity of effects; thus for example, a single additive may act as a dispersant as well as an oxidation inhibitor. These multifunctional additives are well known.

Various turbine additive packages are known and/or commercially available. Those include, for example, certain of the HITEC™ additive packages manufactured by AFTON®.

Properties To monitor the in-service turbine oils and to warn of substantial losses in oxidation resistance, a standard rotating pressure vessel oxidation test, RPVOT or ASTM D 2272-02, has been developed. For example, a RPVOT decrease or “drop” of 75% (or a 25% retention) from the new oil RPVOT value with a concurrent increase in acid number (AN) has been used as a warning limit for loss of oxidative stability. A 100-minute limit for a 75% reduction in RPVOT value is often used as an alternative indicator of loss of that stability in a Group I finished turbine oil. In one embodiment, the turbine oil composition has an RPVOT value of at least 1500 minutes. In a second embodiment, RPVOT value of at least 1700 minutes. In a third embodiment, an RPVOT value of at least 1900 minutes. In a fourth embodiment, an RPVOT value of at least 2000 minutes. In a fifth embodiment, at least 2500 minutes.

In all turbines, and especially in turbines with small sumps and minimal residence time, entrained air mixtures could be sent to bearings and critical hydraulic control elements, causing failure in lubricant film strength, loss of system control, and increased rate of oxidation. Accordingly, most steam and gas turbine OEMs specify air-release speed limits in their oil specification requirements, which can range from as low as 4 minutes (defined as the time for the air entrained in the oil during the test procedure to detrain to 0.2% by volume). Persons skilled in the art may use standard test method ASTM D3427-06 to measure the time it takes to release air from a formulated turbine oil. The turbine oil composition comprising a major amount of one or more FTBOs has improved capacity to release entrained air as compared to a corresponding turbine oil formulated with the same additives but with only non-FTBOs.

In one embodiment, the turbine oil composition also has a reduced tendency to catch fire as compared to a corresponding turbine oil composition comprising the same additive but only non-FTBOs. A standard test, ASTM D92-05a, can be used to measure the flash point of a finished turbine oil. In one embodiment, the composition has an improved flash point, typically above about 236° C., or above about 238° C., or above about 240° C., or above about 245° C., or even above about 250° C., thus rendering a relatively low tendency to catch fire under high temperatures. Another standard test, ASTM E659-78 (Rev. 2005), can be used to measure the autoignition temperature of a finished turbine oil, which is another indicator of the volatility of the oil. In one embodiment, the turbine composition has an autoignition temperature of greater than about 360° C. In a second embodiment, greater than about 362° C. In a third embodiment, greater than about 365° C. In a fourth embodiment, greater than about 370° C.

In one embodiment, the turbine oil composition further has improved water separability, a characteristic that is especially desirable when the industrial turbine housing the composition is operated in the presence of water. A standard test method, ASTM D1401-02 can be used to demonstrate this improvement in water separability. In this test 40 mL of oil is mixed with 40 ml of water at 54° C. and the time taken for the resulting emulsion to reduce to 3 mL or less (considered to be complete separation) is recorded. If complete separation does not occur, then the volume of oil, water and emulsion present is recorded. In one embodiment, the turbine oil composition separates from water in less than 30 minutes as measured according to ASTM D-1401-2002. In a second embodiment, the composition separates from water in less than 15 minutes. In a third embodiment, less than 10 minutes.

In one embodiment, the turbine oil composition also has a reduced tendency to form sludge and/or varnish. A standard test method, ASTM D4310-06b, can be used to demonstrate this improvement by measuring the amount of sludge formed during a specified time period and comparing it with the amount obtained from a corresponding turbine oil comprising only non-FTBOs.

It should be further noted that the turbine oil composition meets at least one of DIN 51515-1 and DIN 51515-2 specifications for turbine oils. In a second embodiment, the turbine composition further meets major industry specifications for gas and turbine oils, including those of GE, Alstom, Mitsubishi Heavy Industries and Siemens. This invention will be further understood by reference to the following examples.

EXAMPLES The following examples are provided to illustrate the present invention without limiting it. While the present invention has been described with reference to specific embodiments, this application is intended to encompass those various changes and substitutions that may be made by those skilled in the art without departing from the scope of the appended claims.

The Fischer-Tropsch derived base oils (FTBOs) used in some of the examples were produced by hydroisomerization dewaxing a 50/50 mix of Luxco 160 petroleum-based wax and Moore & Munger C80 Fe-based FT wax. The hydroisomerized product was hydrofinished and fractionated by vacuum distillation. The distillate fractions were selected having the properties described in Table 4. FTBO A is an example of a base oil made from a waxy feed having a VI greater than an amount defined by the equation: VI=28×Ln(Kinematic Viscosity at 100° C.)+105. It also has a very low traction coefficient.

1. Performance Comparison: Base Oils in Turbine Oil Compositions

Each of Base Oil Mixtures A to E was prepared by blending two base stocks in accordance with Table 1. Specifically, Base Oil Mixture A was prepared by blending two API group I base stocks of different viscosity, Base Oil Mixture B was prepared by blending two API Group II base stocks of different viscosity, Base Oil Mixture C was prepared by blending two API Group III base stocks of different viscosity, Base Oil Mixture D was prepared by blending two PAO base stocks of different viscosity, and Base Oil Mixture E was prepared by blending the two FTBOs of different viscosity described above, so that the final viscosity of each Base Oil Mixture was about 30.4 mm²/s. at 40° C. These Base Oil Mixtures were further blended with six different turbine additive packages, including a commercially available rust and oxidation inhibited additive package for turbine oils (“AD Package”) and five different additive packages (“PAPs”), i.e., PAP1 to PAP5, so that the finished oils, i.e., A1 to A6, B1 to B6, C1 to C6, D1 to D6, and E1 to E6, comprised greater than about 95 wt. % of a Base Oil Mixture and less than about 5 wt. % of an additive package.

A standard method, ASTM D2270-04, was used to measure the VIs of these finished oils.

These finished oils were also tested for oxidative stability in a standard Rotating Pressure Vessel Oxidation Test (RPVOT) or ASTM D2272-02. In that test, an oil sample, water and a copper catalyst coil were placed in a pressurized vessel. The vessel was then charged with oxygen, placed in a temperature-controlled bath and rotated. The time it took to reach a decrease in pressure of 25 psi in the vessel was reported. Improvements in performance can be correlated with increases in the reported time.

These finished oils were further evaluated for evaporation weight loss in a standard bench test ASTM D972-02. In that test, a weighed oil sample was placed in an evaporation cell in an oil bath at the desired test temperature of 149° C. Heated air at a specified flow rate was then passed over the sample surface for 22 hours, after which the loss in sample mass was determined. Improvements in performance can be correlated with decreases in the evaporation weight loss.

Moreover, the flash points of these finished oils were determined using a standard bench test, the Cleveland Open Cup ASTM D92-05a. In that test, the oil samples were placed in test cups individually. A mechanical swinging arm then moved a small test flame across the top of each cup. The temperatures at which the test oils caught fire were reported. Improvements in performance, i.e., reductions in the tendency to catch fire, can be correlated with increases in the flash point temperature. In conjunction, the autoignition temperatures of these oils were measured using a standard method, ASTM E 659 (Rev. 2005). In that test, a sample oil was injected into a test beaker or container filled with heated air. The temperature of the air at which the oil sample spontaneously ignited was reported as the autoignition temperature. Improvements in performance, i.e., reductions in the tendency to catch fire, can be correlated with increases in the autoignition temperature.

Furthermore, the water separability of each of these finished oils was determined using a standard test, ASTM D1401-02. In that test, a sample oil was stirred at 40° C. with an equal volume (40 ml) of water, and the time it took to separate the resulting emulsion (if formed) was reported. Improvements in performance can be correlated with decreases in the time it takes to separate the water phases from the oil phases.

Their capacities to release entrained air were further compared using ASTM D3427-06. In that test, individual test oil was saturated with air bubbles at about 50° C., and the time (minutes) it took for the fluid to return to an air content of 0.2% was reported. Improvements in performance can be correlated with decreases in the reported time.

TABLE 1
Comparison of Performance Characteristics in Bench Tests
	Base			D2272	D92		E659	D1401	D3427
#	Oil Mix	Additive	VI	(min)	(° C.)	D972	(° C.)	O/W/E/T(min)	(min)
A1	Gp. I	AD Package	92	702	204	10.72	374	40/40/0/15	1.33
A2		PAP 1	92	952.7	210	10.95	332	40/40/0/25	1.8
A3		PAP 2	91	1023	217	10.97	358	40/40/0/15	1.42
A4		PAP 3	93	320	—	10.46	—	40/40/0/15	—
A5		PAP 4	99	252	—	—	351	41/39/0/5	4.6
A6		PAP 5	91	454	—	9.87	—	40/40/0/14	—
B1	Gp. II	R&O	97	1229	206	7.87	368	40/40/0/15	0.9
B2		PAP 1	98	1912	208	10.28	338	40/40/0/15	1.25
B3		PAP 2	96	1596	215	7.99	358	40/40/0/10	0.92
B4		PAP 3	105	476	—	7.59	—	40/40/0/15	—
B5		PAP 4	95	287	—	—	342	40/40/0/5.5	3.43
B6		PAP 5	96	1468	—	7.72	—	40/40/0/13	—
C	Gp. III	AD Package	135	1738	232	2.61	369	40/40/0/15	0.8
C		PAP 1	127	1824	232	2.95	380	40/40/0/15	1.1
C		PAP 2	125	2859	242	2.68	363	40/40/0/10	0.68
C		PAP 3	126	638	—	3.21	—	40/40/0/14	—
C		PAP 4	125	371	—	—	338	40/40/0/7	1.02
C		PAP 5	125	2572	—	2.54	—	40/40/0/11	—
D	PAO	AD Package	129	1935	236	1.53	366	40/40/0/15	<0.17
D		PAP 1	128	1834	236	1.46	363	40/40/0/15	<0.17
D		PAP 2	127	3124	240	1.36	375	40/40/0/10	0.43
D		PAP 3	127	698	—	1.99	—	40/40/0/12	—
D		PAP 4	127	431	—	—	343	40/40/0/7	<0.50
D		PAP 5	127	2058	—	1.38	—	40/40/0/11.5	—
E1	FTBO	AD Package	160	1965	240	2.12	370	40/40/0/10	1
E2		PAP 1	152	1991	252	1.84	362	40/40/0/10	0.4
E3		PAP 2	150	3480	241	5.61	360	40/40/0/10	0.6
E4		PAP 3	150	661	—	2.65	—	40/40/0/6	—
E5		PAP 4	151	438	—	—	370	40/40/0/6	0.9
E6		PAP 5	151	2811	—	1.61	—	40/40/0/10	—

2. Other Indications of Improvements Conferred by Turbine Oils Comprising FTBOs

The improvements in oxidative stability, thermal stability, and sludge forming tendencies were further verified with a second set of turbine oil compositions, which are prepared in accordance with Table 2. Each of the base oil mixtures F to J were prepared by blending two base stocks of different viscosity so that the final viscosity in each base oil mixture was again about 30.4 mm²/s at 40° C. These base oil mixtures were subsequently blended with the same set of turbine additives, a commercially available rust and oxidation inhibited additive package for turbine oils (“AD Package”), and PAP1 to PAP5, forming finished turbine oil samples F1 to F6, G1 to G6, H1 to H5, I1 to I6 and J1 to J6.

The VIs and RPVOT oxidative stabilities of these oils were measured using standard methods ASTM D2270-04 and ASTM D2272-02, respectively. The thermal stability of each was tested using the Cincinnati Machine Thermal Stability Test A. In that test, steel and copper rods were placed in the sample oils for 168 hours at 135° C., and the viscosity change and sludge levels were reported. Improvements in thermal stability can be correlated with decreases in either or both the amount of sludge and/or the % viscosity change at either 40 or 100° C.

A Ramsbottom Carbon Residue test, ASTM D524-04, was used to evaluate the oils' tendencies to form carbon residues. In that test, each of the oil samples, after being weighed into a special glass bulb, was placed in a metal furnace, heated to 550° C. quickly and maintained at that temperature for 20 minutes, evaporating all volatile materials. After the test, the bulb was cooled and weighed, and the residues remaining was reported in wt. % of the original sample. Improvements in performance can be correlated with decreases in the wt. % of the residues.

TABLE 2
Results of Cincinnati Machine Thermal Test A, Ramsbottom
carbon ASTM D524-04, and Modified RPVOT Sludge Test.
	CM Thermal A
	Base			Sludge	% vis. change	D524 %
#	Oil Mix	Add.	VI	(mg/100 ml)	@40/100° C.	residue
F1	Gp. I	AD	—	—	—	—
		Package
F2		PAP1	—	—	—	—
F3		PAP2	102	28.9	3.2	0.08
F4		PAP3	100	22.9	3.5	0.07
F5		PAP4	101	24.4	4.6	0.07
F6		PAP5	103	40.3	3.9	0.05
G1	Gp. II	AD	108	6.55	2	0.04
		Package
G2		PAP1	107	9.4	1.7	0.03
G3		PAP2	107	19.7	1.4	0.06
G4		PAP3	107	6.65	1	0.04
G5		PAP4	106	11.4	1.3	0.04
G6		PAP5	108	8.6	1.3	0.03
H1	Gp. III	AD	131	4.65	6.3	0.03
		Package
H2		PAP1	131	12.4	3.6	0.03
H3		PAP2	135	14.75	0.7	0.06
H4		PAP3	135	7.65	0.7	0.03
H5		PAP4	135	7.4	1.0	0.04
H6		PAP5	136	5.8	0.3	0.03
I1	PAO	AD	137	5.95	1.7	0.02
		Package
I2		PAP1	137	7.8	0.3	0.03
I3		PAP2	136	11.25	0.3	0.05
I4		PAP3	137	5.9	0	0.03
I5		PAP4	137	11.6	1.0	0.04
I6		PAP5	137	6.7	−3.5	0.02
J1	FTBO	AD	162	5.45	2.7	0.02
		Package
J2		PAP1	162	5.3	2.3	0.02
J3		PAP2	152	9.65	0.7	0.05
J4		PAP3	151	5.9	1	0.03
J5		PAP4	155	7.0	2.0	0.04
J6		PAP5	153	6.55	0	0.02

3. Comparisons of Performance Characteristics of Turbine Oils In Compressor Tests

Five additional turbine oil compositions were prepared, each comprising base oils from a different source but the same commercially available rust and oxidation inhibited additive package for turbine oils (“AD Package”). These compositions were prepared in accordance with Table 3.

A standard test, ASTM D2270-04, was used to determine the VI of each of these oils. The RPVOT as described Example 1 above was used to determine the time it took to reach a drop in pressure of 25 psi as the result of oxidation.

To evaluate the sample oils in their capacities to deactivate copper and iron elements and prevent oxidation catalyzed by those metals, a CIGRE test was also employed. In that test, oxygen was passed through a glass tube filled with 40 grams of a sample oil at 120° C. and at a flow rate of 1 liter per hour. Each test was conducted for 168 hours, and the amount oxidation products trapped in the water phase were measured and reported as volatile acidity. Improvements in oxidative stability can be correlated with decreases in total sludge, soluble acidity, the amount of total oxidation product or increases in the ratio of sludge on top.

Moreover, compressor tests ROCOT and PNEUROP were used to further demonstrate the improvements in performance imparted by the FTBOs. Specifically, the PNEUROP test was conducted using 40 grams of each oil sample in the absence of catalysts, in a vessel heated to 200° C. and with air flowing through at a speed of 15 liters per hour for 12 hours. The amount of evaporated oil as well as the amount of carbon formation were reported. Improvements can be correlated with either decreases in evaporation loss or decreases in the amount of carbon formation. The ROCOT test, on the other hand, was conducted using 40 grams of each oil sample in the presence of an iron naphthenate catalyst, in a vessel heated to 140° C. and with air flowing through at a speed of 15 liters per hour for 168 hours. The amount of evaporation loss, viscosity increase, TAN increase and sludge formation were reported. Improvements in performance can be correlated with one or more of the following: (1) decreases in evaporation loss; (2) reductions in the extent of change in kinematic viscosity; (3) reductions in the amount of TAN; (4) reductions in sludge formation.

Furthermore, a standard sludge test, ASTM D4310-06b, was used to compare the turbine oil composition comprising a major amount of FTBO with a turbine oil composition comprising the same amount of Group III base oil and a turbine oil composition comprising the same amount of Group I base oil. Improvements in performance can be correlated with decreases in the amount of sludge formed during the test.

TABLE 3
CIGRE and Compressor Tests:
	Gp I + AD	Gp II + AD	Gp III + AD	PAO + AD	FTBO + AD
Properties	Package	Package	Package	Package	Package
VI	103	—	127	138	162
RPVOT (min)	579.4	1124	1322	1242	1620
CIGRE
Volatility acidity	0.055	0.10	0.025	0.075	0.06
Total Sludge	0.11	0.05	0.045	0.07	0.055
Soluble acidity	0.41	0.335	0.86	0.16	0.175
Total Oxidation Product	0.26	0.19	0.325	0.14	0.125
Ratio of Sludge on Top	0.265	0.265	0.185	0.495	0.44
PNEUROP
Evaporation loss	4.14	10.76	7.185	3.96	8.82
CCT	0.172	0.950	0.662	0.119	0.321
ROCOT
Evaporation Loss %	3.88	4.5	1.34	1.36	1.58
Kin. Vis. Increase %	8.88	5.5	1.91	2.15	3.8
TAN increase mg	0.12	0.09	0.085	0.09	0.08
KOH/g	0.14	0.028	0.045	0.06	0.065
Heptane sludge %
Sludge ASTM D4310-06b	215.5	—	88.5	—	170
Amount of sludge, mg

TABLE 4
FTBO Properties
	FTBO A	FTBO B
Viscosity at 100° C., cSt	7.597	4.45
Viscosity Index	162	146
Pour Point, ° C.	−13	−18
Total Wt % Aromatics	0.0168	0.0129
Wt % Olefins	0.0	0.0
FIMS, Wt %
Alkanes	58.3	65.2
1-Unsaturations	34.4	27.5
2- to 6- Unsaturations	7.3	7.3
Total	100.0	100.0
Total wt % Molecules with Cycloparaffinic	41.7	34.8
Functionality
Ratio of Monocycloparaffins to	4.7	3.8
Multicycloparaffins
Oxidator BN, hours	45.42	44.09
X in the equation: VI = 28 ×	105.2	104.1
Ln(VIS100) + X
Traction Coefficient at 15 cSt	<0.021	0.0235
Noack Volatility, wt %	3.92	8.52
N-d-M Carbon Types, wt %
Paraffinic Carbon	92.46	93.97
Naphthenic Carbon	7.54	6.03
Aromatic Carbon	0.00	8.52

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained and/or the precision of an instrument for measuring the value. Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred herein are expressly incorporated herein by reference.

Claims

1. A turbine oil composition comprising an admixture of:

(a) a major amount of at least an isomerized base oil having consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M; and

(b) a minor amount of one or more standard turbine oil additive packages;

wherein the turbine oil composition has a viscosity index of greater than about 150.

2. The composition of claim 1, wherein isomerized base oil has consecutive numbers of carbon atoms and has less than 10 wt % naphthenic carbon by n-d-M.

3. The composition of claim 1, wherein isomerized base oil is a Fischer-Tropsch derived base oil made from a waxy feed.

4. The composition of claim 1, wherein isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.

5. The composition of claim 1, wherein the isomerized base oil has a wt % Noack volatility between 0 and 100.

6. The composition of claim 1, wherein the isomerized base oil has a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15.

7. The composition of claim 1, wherein the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of about 600° F. to 750° F. and wherein the isomerized base oil has a Noack volatility of less than 50 weight %.

8. The composition of claim 1, wherein the at least an isomerized base oil is greater than about 60 wt. %, based on the total weight of the turbine oil composition.

9. The composition of claim 8, wherein the at least an isomerized base oil is greater than about 80 wt. %, based on the total weight of the turbine oil composition.

10. The composition of claim 9, wherein the at least an isomerized base oil is greater than about 90 wt. %, based on the total weight of the turbine oil composition.

11. The composition of claim 10, wherein the at least an isomerized base oil is greater than about 90 wt. %, based on the total weight of the turbine oil composition.

12. The composition of claim 1 having a viscosity index of greater than about 153.

13. The composition of claim 12, having a viscosity index of greater than about 160.

14. The composition of claim 1, having a flash point of greater than about 236° C., as measured using ASTM D92.

15. The composition of claim 14, having a flash point of greater than about 245° C., as measured using ASTM D92.

16. The composition of claim 1, having an autoignition temperature of greater than about 360° C., as measured using ASTM E 659 (Rev. 2005).

17. The composition of claim 16, having an autoignition temperature of greater than about 370° C., as measured using ASTM E 659 (Rev. 2005).

18. The composition of claim 1, wherein the one or more standard turbine oil additive packages comprise one or more materials selected from: antioxidants, wear inhibitors, demulsifiers, antifoamants, and rust/corrosion inhibitors.

19. The composition of claim 20, wherein the one or more standard turbine oil additive packages further comprise one or more materials selected from: detergents, ashless dispersants, viscosity index improvers, friction modifiers, seal fixes, and multifunctional additives.

20. The composition of claim 1, wherein the at least an isomerized base oil has a viscosity index of no less than about 140.

21. The composition of claim 1, wherein the at least an isomerized base oil has a kinematic viscosity of greater than about 2 mm2/s at 100° C.

22. The composition of claim 1, wherein the at least an isomerized base oil has a pour point of below about −8° C.

23. The composition of claim 1, wherein the at least an isomerized base oil has a cloud point of below about 5° C.

24. The composition of claim 1, wherein the at least an isomerized base oil has an Oxidator BN of greater than about 40 hours.

25. A method of improving the performance and service life of an industrial turbine, said method comprising operating the turbine in the presence of a turbine oil composition comprising an admixture of:

a major amount of at least an isomerized base oil having consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M; and

a minor amount of one or more standard turbine oil additive packages;

wherein the turbine oil composition has a viscosity index of greater than about 150.