Patent Application
20100216678
The present disclosure relates to a lubricant useful in engine oils and in general lubricant applications. The present disclosure further relates to a lubricant composition containing highly non-polar base stocks, that has improved solvency for polar additives.
Poly-α-olefins (PAOs) are important non-polar lube base stocks with many excellent lubricant properties, including high viscosity index (VI) and low volatility and are available in a wide viscosity range, i.e., a Kv100 of about 2 to about 600 centistokes (cSt)). PAOs are disclosed as lube base stocks, for example, in U.S. Published Patent Application No. 20080177121 A1.
Other important lube base stocks are those derived from one or more Gas-to-Liquids materials (GTLs) that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds. GTLs are disclosed as lube base stocks, for example, in U.S. Published Application No. 2007/0265178, which is incorporated herein by reference.
Other important lube base stocks are the Groups I, II, III and VI base stocks, which are discussed in “Synthetics, Mineral Oils and Bio-Based Lubricants, Chemistry and Technology” Edited by L. R. Rudnick, published by CRC Press, Taylor & Francis, 2006, which is incorporated herein by reference.
Base stocks of PAOs, GTLs, and Groups I-III and VI exhibit relatively low polarity. This low polarity leads to low solubility and dispersancy for polar additives or sludge generated in lubricants containing these base stocks.
To compensate for the low polarity of base stocks of PAOs, GTLs, and Groups I-III and VI, lubricant manufacturers commonly incorporate one or more polar co-base stocks. Commonly used co-base stocks are esters or alkylated naphthalenes, which are typically present in the lube base stock at about 1 wt % to about 50 wt % based on the total weight of the base and co-base stocks. Esters and alkylated naphthalenes are disclosed, for example, in U.S. Pat. Nos. 6,627,779 B2 and 6,833,065 B2 as well as WO 03/035585. Other co-base stocks include various dicarboxylic acid esters, which are disclosed, for example, in U.S. Pat. Nos. 2,936,320; 3,251,771; 3,409,553; 4,464,277; and 6,667,285.
U.S. Pat. No.3,701,730 discloses extreme pressure additives for lubricant compositions which are synthetic esters, such as (a) dibrominated neopentyl glycol esters, (b) phosphate esters, polycarboxylic acids having 2-54 carbon atoms, or (d) combinations of (a), (b) and (c).
U.S. Pat. No. 4,683,069 discloses lubricating oil compositions exhibiting improved fuel economy which contain 0.05 to 0.2 wt % of a glycerol partial ester of a C16-C18 fatty acid as a fuel economy additive.
U.S. Pat. No. 5,034,144 discloses lubricating oil compositions used for food processing machines, which exhibit highly improved oxidation stability, wear resistance and rust prevention, comprising as the base oil a saturated fatty acid glyceride and as an essential component, a fatty acid in an amount of 0.001 to 5% by weight, based on the total composition.
U.S. Pat. No. 5,262,076 discloses synthetic lubricating oils having as a base oil at least one carbonic acid ester of various disclosed polyols.
U.S. Pat. No. 5,503,762 discloses base oils with high viscosity indices and low pour points which are mixtures of a complex ester formed from aliphatic, cycloaliphatic or aromatic dicarboxylic acids, aliphatic polyols containing 2 to 6 hydroxyl groups and aliphatic monocarboxylic acids containing 6 to 22 carbon atoms and adipic acid esters of unbranched aliphatic monohydric alcohols.
U.S. Pat. No. 5,538,654 discloses a food grade lubricant composition for equipment in the food service industry, comprising (A) a major amount of a genetically modified vegetable oil and (B) a minor amount of a performance additive.
U.S. Pat. No. 5,658,864 discloses the use of biodegradable polyalphaolefins (“PAOs”) to treat biodegradable industrial fluids, such as lubricants, hydraulic fluids, fuel oils, and the like, to: (a) reduce their pour point; (b) improve their oxidation stability performance; and/or, (c) improve their hydrolytic stability performance. A preferred industrial fluid is mixture of vegetable oil and branched alkane where the average molecular weight of the alkane is about 200-400, and the alkane additionally has a sufficient degree of branching to have a pour point of about −25° C. or lower.
U.S. Pat. No. 6,833,065 discloses methods for preparing a blended lube base oils comprising at least one highly paraffinic Fischer-Tropsch lube base stocks and at least one base stock composed of alkylaromatics, alkylcycloparaffins, or mixtures thereof. The use of base stocks composed of alkylaromatics, alkylcycloparaffins, or mixtures thereof improves the yield of lube base oils from Fischer-Tropsch facilities, as well as provides moderate improvements in physical properties including additive solubility. The disclosure provides processes for obtaining such blended lube base oils using the products of Fischer-Tropsch processes.
WO 97/22572 discloses a dielectric fluid or coolant comprising relatively pure blends of compounds selected from the group consisting of aromatic hydrocarbons, polyalphaolefins, polyol esters, glycerol tri-esters and natural vegetable oils, along with additives to improve pour point, increase stability and reduce oxidation rate.
WO 2004/108866 discloses an improved food grade lubricant comprising at least one vegetable oil, at least one polyalphaolefin, and at least one antioxidant.
However, despite recent advances, there remains an unmet need in the art to formulate highly non-polar lubricant base stocks with inexpensive polar co-solvents to improve the solubility of various lube oil additives in the non-polar base stock. Unfortunately, conventional polar co-base stocks can be quite expensive, and when present in large amounts in a lubricant formulation, can raise the cost of the overall composition significantly.
In a first embodiment, the present disclosure is directed to a lubricant composition comprising a Group I-IV or poly-internal-olefin (PIO or Group VI) lube base stock and a glycerol tri-ester of the formula:
wherein R1, R2 and R3 are independently selected from linear or branched C4 to C14 alkyl groups.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the Group I-IV or VI lube base stock is present in an amount of 50 wt % to 99 wt %.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the lube base stock is a liquid polyalphaolefin having a Kv100 of from greater than 3 cSt to 10,000 cSt.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein R1, R2 and R3 are the same or different.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein R1, R2 and R3 are linear alkyl groups.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein R1, R2 and R3 are branched alkyl groups.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein R1, R2 and R3 are a combination of linear and branched alkyl groups.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester is glycerol trioctanoate.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester is glycerol trinonanoate.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester is glycerol tridecanoate.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester has a Kv100 of less than 20 cSt.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester has a VI greater than 90.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the liquid polyalphaolefin has a Kv100 of from greater than 3 cSt to 300 cSt.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the glycerol tri-ester has a pour point of less than 0° C.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, further comprising at least one additive selected from the group consisting of detergents, dispersants, antioxidants, antiwear additives, pour point depressants, viscosity index modifiers, friction modifiers, defoaming agents, corrosion inhibitors, wetting agents, densifiers, fluid-loss additives and rust inhibitors.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the Group I-IV or VI lube base stock is derived from a gas-to-liquid hydrocarbon material.
In another embodiment, the disclosure is directed to a lubricant composition as disclosed above, wherein the Group I-IV or VI lube base stock is a Group III lube base stock.
In another embodiment, the disclosure is directed to a lubricant composition comprising greater than 50 wt % of a metallocene-catalyzed PAO lube base stock, having a Kv100 from 3 cSt to 300 cSt, and less than 50 wt % of a glycerol tri-ester of the formula:
wherein R1, R2 and R3 are independently selected from linear or branched C4 to C14 alkyl groups.
In another embodiment, the disclosure is directed to a lubricant composition comprising greater than 50 wt % of a Group III lube base stock, and less than 50 wt % of a glycerol tri-ester of the formula:
wherein R1, R2 and R3 are independently selected from linear or branched C4 to C14 alkyl groups.
All numerical values in this disclosure are understood as being modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
Glycerol tri-esters of the formula:
wherein R1, R2 and R3 are independently selected from linear or branched C4 to C14 alkyl groups, which can be the same or different, or can be combinations of linear and branched alkyl groups, are very effective as polar co-base lube stocks, particularly for PAO and GTL lube base stocks and can be blended therewith to obtain clear and bright liquids from very low to very high concentrations. The tri-esters are amorphous, have low glass transition temperature (Tg) and are cost-competitive with other polar co-bases. The tri-esters have advantageous lubrication properties, such as low volatility and low viscosity.
The blends of the present disclosure have a first lube base stock of one or more glycerol tri-esters from 1 wt % to 50 wt % and a second lube base stock selected from a Group I to Group IV or Group VI lube base stock, preferably of one or more poly-α-olefin and/or a GTL base stock at 99 wt % to 50 wt % based on the total weight of the blend. Preferred blends have 1 wt % to 50 wt % of the first base stock and 99 wt % to 50 wt % of the second base stock. More preferred blends have the first base stock at 2 wt % to 25 wt % and the second base stock at 98 wt % to 75 wt %.
The glycerol tri-esters useful as co-basestocks can be selected based on physical properties desired. Kinematic viscosity can vary from 2 cSt to 20 cSt, even from 2.5 cSt to 10 cSt, and even from 3 to 7 cSt. Noack volatility can vary from 2 wt % to 30 wt %, even from 3 wt % to 15 wt %. Glass transition temperature, Tg, can vary from 0° C. to −90° C., and even from −10° C. to −80° C. Viscosity index, VI, can vary from 50 to 300, even from 70 to 250 and even from 90 to 250. Pour points are generally less than 0° C., even less than −15° C., even less than −20° C., or even less than −30° C. Kinematic viscosities at 100° C. (Kv100) and 40° C. (Kv40) are measured according to ASTM method D445. Viscosity index is measured according to ASTM method D2270. Noack volatility is measured according to ASTM D5800. The pour points are measured according to ASTM D97.
Particularly useful glycerol tri-esters are those having C4 to C14 alkyl substituents at the ester linkages, with average carbon length of 6 to 10, even between 7 to 9 carbon atoms, from a single acid or a mixture of acids, especially the C8 and C9 tri-esters exhibiting a Kv100 of less than 4 cSt. These glycerol tri-esters are “green” additive solubilizers because they do not contain N, S, or aromatic rings and because they also exhibit superior oxidative and cleanliness attributes.
The glycerol tri-esters can be synthesized by reacting glycerol with either C4 to C14 alkyl acids, or with C4 to C14 alkyl acid chlorides with average carbon length of 6 to 10, even between 7 to 9 carbon atoms, from a single acid or a mixture of acids. The esterification procedure is carried out in the presence of a catalyst. While the selection of the particular alkyl acids or alkyl acid chlorides is not critical, it is important that the reactant acids or acid chlorides be fully saturated compounds, i.e. having no unsaturated sites within the carbon chains thereof. We have found that glycerol tri-esters of unsaturated organic acids will tend to degrade under the high temperature conditions typically encountered by engine lubricating oils, forming unwanted contaminants in the lubricating oil.
The reactants may be contacted in the presence of a heterogeneous or a homogenous acid catalyst. The acid catalyst is used to increase the rate of reaction. The amount of catalyst is not critical, but at least enough catalyst must be used to provide a reasonable rate of esterification.
A conventional heterogeneous esterification catalyst may be used. One preferred heterogeneous catalyst that may be used is a sulfonic acid cation exchange resin having a macro-reticular structure. These catalysts, their properties, and method of preparation are shown in U.S. Pat. No. 3,037,052, which is incorporated herein by reference. Such catalysts are available commercially and are sold under the trade name Amberlyst by Rohm & Haas of Philadelphia, Pa. Acidic zeolite catalysts may also be used.
Alternatively, a conventional homogenous esterification acid catalyst may be utilized in the reaction. Useful catalysts include sulfuric acid, phosphoric acid, p-toluene sulfonic acid, sodium bisulfate, potassium bisulfate, related catalysts, and the like. Other catalysts that may be used include esters of titanium or zirconium, such as tetraalkyl titanates or zirconates (e.g. tetraethyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetra-n-propyl zirconate). Also, metal oxides such as zinc oxide, alumina, and the like can be used. A preferred homogenous catalyst is 4-toluene sulfonic acid monohydrate. A preferred catalyst is titanium isopropoxide.
The esterification is carried out at a temperature, pressure, and for a period of time sufficient to affect the desired level of conversion. The reaction temperature is usually from 25 to 300° C., even from 50 to 250° C., and even from 100 to 220° C. The reaction is carried out for a time preferably from 1 to 48 hours, even from 2 to 36 hours, and even from 4 to 24 hours. Completion of reaction may be determined by gas chromatography analysis of the product composition.
PAOs are a class of hydrocarbons that can be manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear α-olefin (LAO) monomers. These typically range from 1-hexene to 1-tetradecene, with 1-decene being an advantageous material, although oligomeric copolymers with lower olefins such as ethylene and propylene may also be used, including copolymers of ethylene with higher olefins as described in U.S. Pat. No. 4,956,122 and the patents referred to therein. PAO products have achieved importance in the lubricating oil market. Typically there are two classes of synthetic hydrocarbon fluids (SHF) produced from linear alpha-olefins, the two classes of SHF being denoted as PAO and HVI-PAO (high viscosity index PAO's). PAO's of different viscosity grades are typically produced using promoted BF3 or AlCl3 catalysts.
Specifically, PAOs may be produced by the polymerization of olefin feed in the presence of a catalyst such as AlCl3, BF3, or promoted AlCl3 or BF3. Processes for the production of PAOs are disclosed, for example, in the following patents: U.S. Pat. Nos. 3,149,178; 3,382,291; 3,742,082; 3,769,363; 3,780,128; 4,172,855 and 4,956,122, which are fully incorporated by reference. PAOs are also discussed in the following: Will, J. G. Lubrication Fundamentals, Marcel Dekker: New York, 1980. Subsequent to polymerization, the PAO lubricant range products are typically hydrogenated in order to reduce residual unsaturation, generally to a level of greater than 90% of hydrogenation. HVI-PAOs may be conveniently made by the polymerization of an alpha-olefin in the presence of a polymerization catalyst such as Friedel-Crafts catalysts. These include, for example, boron trifluoride, aluminum trichloride, or boron trifluoride, promoted with water, with alcohols such as ethanol, propanol, or butanol, with carboxylic acids, or with esters such as ethyl acetate or ethyl propionate or ether such as diethyl ether, and diisopropyl ether. (See for example, the methods disclosed by U.S. Pat. Nos. 4,149,178 and 3,382,291.) Other descriptions of PAO synthesis are found in the following: U.S. Pat. No. 3,742,082; U.S. Pat. No. 3,769,363; U.S. Pat. No. 3,876,720; U.S. Pat. No. 4,239,930; U.S. Pat. No. 4,367,352; U.S. Pat. No. 4,413,156; U.S. Pat. No. 4,434,408; U.S. Pat. No. 4,910,355; U.S. Pat. No. 4,956,122; and U.S. Pat. No. 5,068,487.
Another class of HVI-PAOs may be prepared by the action of a supported, reduced chromium catalyst with an alpha-olefin monomer. Such PAOs are described in U.S. Pat. No. 4,827,073; U.S. Pat. No. 4,827,064; U.S. Pat. No. 4,967,032; U.S. Pat. No. 4,926,004; and U.S. Pat. No. 4,914,254. Commercially available PAOs include SpectraSyn™ 2, 4, 5, 6, 8, 10, 40, 100 and SpectraSyn Ultra™ 150, SpectraSyn Ultra™ 300, SpectraSyn Ultra™ 1000, etc. (ExxonMobil Chemical Company, Houston, Tex.). Also included are PAOs prepared in the presence of an activated metallocene catalyst with a non-coordinating anion activator or a methyaluminoxane activator, and optionally in the presence of hydrogen as discussed in U.S. Published Patent Application No. 2008/0177121 or EP1910432A1, which can have Kv100 values from 2 cSt to as much as 10,000 cSt, even between 3 cSt to 10,000 cSt, even between 3.5 cSt to 1000 cSt, or between 4 cSt to 600 cSt, or between 4 cSt to 300 cSt, or between 4 cSt to 150 cSt, or between 4 cSt to 100 cSt, or between 20 cSt and 300 cSt.
Polyinternalolefin (PIO) or Group VI base stocks are long-chain hydrocarbons, typically a linear backbone with some branching randomly attached; they are obtained by oligomerization of internal n-olefins. The details about these base stocks are discussed in “Synthetics, Mineral Oils and Bio-Based Lubricants, Chemistry and Technology” Edited by L. R. Rudnick, published by CRC Press, Taylor & Francis, 2006, which is incorporated herein by reference.
Gas-to-liquid (GTL) base oils comprise base stocks obtained from GTL materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds. Preferably, the GTL base stocks are derived from the Fischer-Tropsch (F-T) synthesis process wherein a synthesis gas comprising a mixture of H2 and CO is catalytically converted to lower boiling materials by hydroisomerisation and/or dewaxing. The process is described, for example, in U.S. Pat. Nos. 5,348,982 and 5,545,674, and examples of suitable catalysts are described in U.S. Pat. No. 4,568,663, each of which is incorporated herein by reference.
GTL base stocks are characterized typically as having Kv100 of from 2 cSt to 50 cSt, even from 3 cSt to 50 cSt, and even from 3.5 cSt to 30 cSt. The GTL base stock and/or other hydrodewaxed, or hydroisomerized/catalytically (or solvent) dewaxed wax derived base stocks useful in the present disclosure have Kv100 in the range of 3.5 cSt to 7 cSt, even 4 cSt to 7 cSt, and even 4.5 cSt to 6.5 cSt, and pour points of −5° C. or lower, even −10° C. or lower, and even −15° C. or lower.
The GTL base stocks derived from GTL materials, especially hydrodewaxed or hydroisomerized/catalytically (or solvent) dewaxed F-T material derived base stocks, and other such wax-derived base stocks which are base stock components which can be used in this disclosure are also characterized typically as having viscosity indices of 80 or greater, even 100 or greater, and even 120 or greater. Additionally, in certain particular instances, the viscosity index of these base stocks may be 130 or greater, even 135 or greater, and even 140 or greater. For example, GTL base stocks that derive from GTL materials preferably F-T materials especially F-T wax generally have a viscosity index of 130 or greater.
Examples of useful compositions of GTL base stocks are recited in U.S. Pat. Nos. 6,080,301; 6,090,989; and 6,165,949, for example, which are herein incorporated by reference.
Base stock(s), derived from waxy feeds, which are also suitable for use in this disclosure, are paraffinic fluids of lubricating viscosity derived from hydrodewaxed, or hydroisomerized/catalytically (or solvent) dewaxed waxy feedstocks of mineral oil, non-mineral oil, non-petroleum, or natural source origin, e.g., feedstocks such as one or more of gas oils, slack wax, waxy fuels hydrocracker bottoms, hydrocarbon raffinates, natural waxes, hyrocrackates, thermal crackates, foots oil, wax from coal liquefaction or from shale oil, or other suitable mineral oil, non-mineral oil, non-petroleum, or natural source derived waxy materials, linear or branched hydrocarbyl compounds with carbon number of 20 or greater, even 30 or greater, and mixtures of such isomerate/isodewaxate base stocks and base oils.
Slack waxes are waxes recovered from any waxy hydrocarbon oils, including synthetic oils such as F-T waxy oil or petroleum oils by solvent or autorefrigerative dewaxing. Solvent dewaxing employs chilled solvent such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), mixtures of MEK/MIBK, mixtures of MEK and toluene, while autorefrigerative dewaxing employs pressurized, liquefied low boiling hydrocarbons such as propane or butane.
Slack waxes secured from synthetic waxy oils such as F-T waxy oil will usually have zero or nil sulfur and/or nitrogen containing compound content. Slack waxes secured from petroleum oils, may contain sulfur and nitrogen containing compounds. Such heteroatom compounds must be removed by hydrotreating (and not hydrocracking), as for example by hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) so as to avoid subsequent poisoning/deactivation of the hydroisomerization catalyst.
Preferred base stocks or base oils derived from GTL materials and/or from waxy feeds are characterized as having predominantly paraffinic compositions and are further characterized as having high saturates levels, low-to-nil sulfur, low-to-nil nitrogen, low-to-nil aromatics, and are essentially water-white in color.
The lubricant of the present disclosure can have API Group I-III oils as second base stocks. Useful Group I-III base stocks have a Kv100 of greater than 3 cSt to 5 cSt. API Groups I, II, and III represent base stocks typically refined from crude oil and are differentiated by viscosity index (VI), saturation content, and sulfur content.
The specifications for the lube base oils are defined in the API Interchange Guidelines (API Publication 1509) using sulfur content, saturates content, and viscosity index, as follows:
Manufacturing plants that make Group I base oils typically use solvents to extract the lower viscosity index (VI) components and increase the VI of the crude to the specifications desired. These solvents are typically phenol or furfural. Solvent extraction gives a product with less than 90% saturates and more than 300 ppm sulfur. The majority of the lube production in the world is in the Group I category.
Manufacturing plants that make Group II base oils typically employ hydroprocessing such as hydrocracking or severe hydrotreating to increase the VI of the crude oil to the specifications value. The use of hydroprocessing typically increases the saturate content above 90 and reduced the sulfur below 300 ppm. Approximately 10% of the lube base oil production in the world is in the Group II category, and 30% of U.S. production is Group II.
Manufacturing plants that make Group III base oils typically employ wax isomerization technology to make very high VI products. Since the starting feed is waxy vacuum gas oil (VGO) or wax which contains all saturates and little sulfur, the Group III products have saturate content above 90 and sulfur content below 300 ppm.
The lubricant of the present disclosure may optionally include lube base oil additives such as detergents, dispersants, antioxidants, antiwear additives, pour point depressants, viscosity index modifiers, friction modifiers, defoaming agents, corrosion inhibitors, wetting agents, densifiers, fluid-loss additives, rust inhibitors, and the like. The additives are incorporated into the blend to make a finished lubricant that has desired viscosity and physical properties. Typically, additives will make up 10 wt % or less of the lubricant. Typical description of additives used in different lubricant product formulation can be found in “Lubricant Additives, Chemistry and Applications” Ed. L. Rudnick, published by Marcel Dekker, Inc. New York, N.Y., 2003.
The lubricant can be employed in a variety of end uses, such as automotive crank case lubricant, automotive engine lubricants, automotive driveline lubricants, automotive gear oils, automotive transmission lubricants, general industrial lubricants, gear and circulation oils, hydraulic lubricants, grease, etc.
We found that glycerol tri-esters are very effective polar co-base stocks for PAO of all viscosity ranges, GTL fluids and other hydrocarbon base stocks such as Group I-III or Group VI, and can be blended with these non-polar base stocks to improve their polarity, solvency and unexpectedly, their low temperature properties. These blends were clear and bright liquids from very low to very high concentrations.
We have synthesized several glycerol tri-esters using glycerol (derived from plant oils and a by-product in bio-diesel process) as feed and studied their lube properties. Base stocks with wide viscosity ranges, high VI (>80) and low pour points and excellent low temperature properties can be prepared.
We discovered that some of the glycerol tri-esters have unique lube properties, such as low Kv100 viscosity and high VI. For example, C9 tri-ester has a Kv100 of 3.84 cSt (<4 cSt) and VI of 124. These types of polar base stocks are “green” additive solubilizers, since they can be derived from renewable or sustainable sources, and also have superior oxidative and cleanliness features.
Four glycerol tri-esters were synthesized by reaction of glycerol and various (C6-C10) acids or acid chlorides. The lube properties and product performance of these esters were evaluated to develop structure-property-performance knowledge for these Group V base stocks. Other compositions can be synthesized to optimize lube properties (linear vs. branched and using various carbon length acids, i.e. C7, C8, C9, etc).
Kinematic viscosities (Kv), viscosity index (VI), and pour point (PP) temperature of the products were evaluated using following techniques. Kinematic viscosity was measured according to ASTM method D445. Viscosity index was measured according to ASTM method D2270. The pour points are measured according to ASTM D97.
Glycerol (1.430 g, FW. 92.09) and octanoyl chloride (7.65 g, FW. 162.7) were weighed in a 50 ml flask and cooled down in an ice bath. Pyridine (4.0 g, FW. 79.1) was slowly added drop-wise while stirring. The reaction mixture turned slightly yellow. After 10 minutes, the mixture was filtered to remove pyridine HCl salt that had formed in the reaction mixture. The solution was diluted with 100 ml t-butyl methyl ether and any unreacted pyridine was removed by washing with dilute HCl solution (1N, 50 ml×2). The solution was further washed with brine and dried by MgSO4. The t-butyl methyl ether solvent was removed by rotary evaporation. 8.6 g of a viscous, slightly yellow product was obtained. Yield: 95.5%. The product was analyzed using IR spectroscopy.
Glycerol (1.03 g, FW. 92.09) and nonanoyl chloride (5.94 g, FW. 176.7) were weighed in a 50 ml flask and cooled down in an ice bath. Pyridine (3.0 g, FW. 79.1) was slowly added drop-wise to the flask while stirring. The reaction mixture turned slightly yellow. After 10 minutes the mixture was filtered to remove pyridine HCl salt that had formed in the reaction mixture. The solution was diluted with 100 ml t-butyl methyl ether and any unreacted pyridine was removed by washing with dilute HCl solution (1N, 50 ml×2). The solution was further washed with brine and dried by MgSO4. The t-butyl methyl ether solvent was removed by rotary evaporation. 3.85 g of a viscous, slightly yellow product was obtained. Yield: 57%. The product was analyzed using IR spectroscopy.
Glycerol (0.953 g, FW. 92.09) and decanoyl chloride (5.933 g, FW. 190.71) were weighed in a 50 ml flask and cooled down in an ice bath. Pyridine (3.0 g, FW. 79.1) was slowly added drop-wise to the flask while stirring. The reaction mixture turned slightly yellow. After 10 minutes the mixture was filtered to remove pyridine HCl salt that had formed in the reaction mixture. The solution was diluted with 100 ml t-butyl methyl ether and any unreacted pyridine was removed by washing with dilute HCl solution (1N, 50 ml×2). The solution was further washed with brine and dried by MgSO4. The t-butyl methyl ether solvent was removed by rotary evaporation. 4.63 g of a viscous, slightly yellow product was obtained. Yield: 68%. The product was analyzed using IR spectroscopy.
Glycerol (10 g, FW. 92.09), octanoyl chloride (35.32 g) and hexanoyl chloride (14.61) were weighed in a 500 ml flask and cooled down in an ice bath. Pyridine (31.6 g, FW. 79) was added slowly drop-wise to the flask while stirring. The reaction mixture turned slightly yellow. The reaction mixture was stirred for 16 hours at room temperature. The solution was diluted with 200 ml t-butyl methyl ether and stirred for 18 hours. The mixture was filtered to remove pyridine HCl salt that had formed in the reaction mixture. Any unreacted pyridine was removed by washing with dilute HCl solution (1N, 150 ml×2). The solution was further washed with brine (1×150 ml) and dried by MgSO4. The t-butyl methyl ether solvent was removed by rotary evaporation and the product was dried at 160° C. for 3 hours. 4.63 g of a viscous, slightly yellow product was obtained. Yield: 68%. The product was analyzed using IR spectroscopy. The pour point of the product was −45° C.
The physical and chemical properties of these products are shown in Table 1.
The viscosities of the neat glycerol esters are generally low. For example, the polar C8-ester has a Kv100 of 3.29 cSt and a high viscosity index of 108. The C9-ester has a Kv100 of 3.84 cSt (<4 cSt) and a VI of 124.
Glycerol tri-esters were prepared by reacting glycerol and various saturated organic acids (Example 4: Cekanoic C7 acid, Example 5: LION C7 acid, Example 6: Cekanoic C8 acid and Example 7: Cekanoic C9 acid) in the presence of titanium tetra-isopropoxide as the catalyst. These organic acids have slight branching in their compositions. The physical and chemical properties of these products are shown in Table 2.
The glycerol tri-esters showed high VI and very low pour points.
Other compositions can be synthesized to optimize lube properties (linear vs. branched) and using various carbon length acids, i.e. C7, C8, C9, etc. or mixed acids.
Blend properties of various hydrocarbon base stocks like PAO, Group III, and glycerol esters are shown in Table 3 below. The glycerol esters were blended with hydrocarbon fluids in the wt % ratio of 20:80. All the blend samples were clear and bright, which suggests that these two types of base stocks are miscible in each other. The viscosities, viscosity index (VI), and pour point temperatures are shown in the tables. The test methods for Kv100 and Kv40 was ASTM D445, for viscosity index (VI) was ASTM D2270 and for pour point (PP) was ASTM D97.
1PAO-6 is low viscosity SpectraSyn ™ 6 polyalpholefin (PAO) commercially available from ExxonMobil Chemical.
2PAO 150 is prepared according to U.S. Published Patent Application No. 2008/0177121.
The viscosity indices (VI) of the blends are high. The viscosity of high-VI fluids changes less dramatically with changes in temperature compared with the viscosity change of low-VI fluids. A practical consequence of this property is that a high-VI fluid may not need a viscosity index improver (VII) in some applications. The presence of a VII is often undesirable because many tend to be unstable toward shear. Once the VII begins to break down, the fully formulated fluid goes “out of grade” (i.e., fails to retain the original viscosity grade).
All products have very low pour points. The property of low pour point makes the fluid very attractive in the cold-climate applications.
While the present disclosure has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the disclosure lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present disclosure.
