Title of Invention

A PROCESS FOR THE PREPARATION OF LUBRICANTS BASED ON HYDROGENATED VEGETABLE OILS

Abstract

The present invention is related to a process for the preparation of lubricants based on hydrogenated vegetable oils. The lubricant base oils, prepared from modified vegetable oils derived entirely from plants, useful for making lubricant composition for automotive and industrial application. More specifically, this invention relates to the esters of hydrogenated non-edible oils such as neem oil, rice bran oil, linseed oil and castor oil as lubricant base oils which not only provide acceptable biodegradability but also provide improved lubricity and viscosity index and process of preparing the same.

Full Text

The present invention is related to a process for the preparation of lubricants based on hydrogenated vegetable oils. This invention is particularly concerned with the lubricant base oils, prepared from modified vegetable oils derived entirely from plants, useful for making lubricant composition for automotive and industrial application. More specifically, this invention relates to the esters of hydrogenated non-edible oils such as neem oil, rice bran oil, linseed oil and castor oil as lubricant base oils which not only provide acceptable biodegradability but also provide improved lubricity and viscosity index and process of preparing the same. Traditionally, the petroleum-derived mineral oils have been the basic sources of industrial and automotive lubricants. The petroleum base lubricating oils are hydrocarbons consisting of naphthenes, paraffins and aromatics. Various additives, which are primarily chemicals of defined composition or structure are added to the mineral base oils to improve the physico-chemical properties and performance for specific applications. Mineral oil based lubricants, generally suffer from many disadvantages such as high toxicity to the environment, poor biodegradability. The other types of lubricants known as synthetic lubricants, are designed for use in extreme conditions of temperature, pressure, radiation or chemical and have excellent lubricity and thermal stability. The synthetic lubricants are relatively costly. Polyglycols, polybutenes, dibasic acid esters, fluoropolymers, polyol esters, phosphate esters, silicones, polyalpha olefins etc. are commonly used synthetic lubricants for various applications. Synthetics are also toxic to environment and are not readily biodegradable. Keeping in view the environmental concerns and improved performance, there is a need to develop alternative lubricants, which are biodegradable and non-toxic and at least show equivalent performance to mineral oil based or synthetic lubricants. The use of vegetable oils as lubricants is known for a long time. Vegetable oils are, by their chemical nature, long chain fatty acids triesters of glycerol and are capable of providing the desirable lubricant properties such as good boundary layer lubrication, high viscosity index, high flash point and low volatility. The major limitations of vegetable oils which restrict their use as lubricant are their thermoxidative stability and low temperature behaviour. European patent EP0714974, describes food grade lubricant composition, useful as hydraulic oil, gear oil and compressor oil for food service industry, comprising of major amount of a genetically modified vegetable oil and minor amounts of a performance additive phosphorous compound or a non-generically modified vegetable oil. In the patents assigned to Agro Management Group Inc. (Patent No. US 5888947 PCT/US96/9509) formulation for lubricants, for use in four stroke internal combustion engines. Comprising of a base oil such as soyabean, canola, rapeseed, crambe, safflower and sunflower, oil containing hydroxy fatty acids derived from castor, less querella etc and an oil source containing vegetable oil or animal wax. Patent WO9207051 assigned to Int. Lubricants Inc. discloses the process for preparing lubricant additives based on the telomerised vegetable oils such as rape seed, crambe, meadow foam, soya bean, peanut, corn, safflower, sunflower, cottonseed, olive, coconut, palm, linseed and combination thereof. In another patent (EP05567995 assigned to Castrol Ltd. GB) satisfactory lubricants for industrial and automotive requirements based on palm oil are described. Vegetable based lubricants prepared using base oils derived from plants which are members of the genus Brassica and Cruciferea (mustard) family, e.g. rapeseed, crambe and canola are described in another patent (WO 96/39476). In view of the growing concern about the environment, there is a need for biodegradable, non-toxic lubricants for automotive and industrial applications, which are derived from renewable resources. The lubricant should be readily biodegradable, preferably by microbes naturally present in the environment and be cost effective. In the prior art for producing lubricants from vegetable oil vegetable oils used are edible oils or genetically modified vegetable oils. The oils generally used include soya bean, canola, rape seed, crambe, safflower, sunflower, castor, animal wax, jojoba oil etc. The focus have been on the use of such vegetable oil based lubricants as additives in petroleum based lubricants to enhance lubricity. Unlike the lubricants of the prior art, the vegetable based lubricant base oils of the present invention are derived from renewable resources are non-toxic and readily biodegradable by natural micro organisms. The lubricant base oils of the present invention has applicability in formulations suitable as lubricants in a variety of applications including two-stroke engine oil, hydraulic oil, refrigeration oil, metal working lubricant, industrial gear oil as well as general purpose lubricants. The main object of the present invention is to provide a process for the preparation of lubricants based on hydrogenated vegetable oils which obviates the drawbacks as detailed above. Another object of the present invention to provide vegetable oil based non-toxic and biodegradable lubricant base oil. Still another object of the present invention is to provide a non-edible vegetable oil based lubricant base oil for use in metal working operations, compressor lubricants, hydraulic fluids, transformer oil, greases and internal combustion engines. Yet another object of the present invention to provide lubricant base oil form modified vegetable oils selected from castor, rice bran, linseed and neem oils that exhibit improved lubrication, viscosity index, thermal stability and pour point. Yet another objective of the present invention is to provide the method preparation of vegetable oil derivatives suitable for use as lubricants base stock. The present invention relates to the modification of unsaturated vegetable oils to prepare liquid products suitable for use as lubricant base stocks. More particularly the present invention is concerned with modification of specific vegetable oils selected from non-edible oils such as neem, ricebran, linseed, pongamia, jatropha curcas, castor and the like by transesterification with a monohydric alcohol having 5-10 carbon atoms and hydrogenating the ester thus formed to enhance the lubricant characteristics e.g. viscosity index and oxidation stability. In a broader sense the invention may be utilized to produce vegetable oil based lubricants which possesses excellent lubricating properties and are environment friendly and biodegradable. Vegetable oils which are long chain fatty acid trimesters of glycerol (triacyl glycerols) possesses most of the desirable lubricant properties such as high viscosity index, high flash point, low volatility and good boundary lubrication. The major limitations of vegetable oils when applied to their lubricant behaviour include poor oxidative stability, low temperature behavior and compatibility with additives. Oxidation of vegetable oils is one of the major concerns that limits the use of vegetable oils as lubricant. Oxidation leads to deterioration of oil due to polymerization and degradation of oil. Polymerisation increases the molecular weight leading to increase in viscosity, gelling and loss of functionality which reduces the lubrication characteristics of the vegetable oil. Vegetable oils such as rice bran oi! for use as lubricant exhibit good viscosity and viscosity index and high flash point and provides good boundary lubrication and is biodegradable. Its poor low temperature behaviours, measured as pour point, higher acidity and high unsaturation measured. Iodine value, which relates to its poor stability limit its use as lubricant. Typical characteristics of rice bran oil : viscosity at 40°C = 23.75 cSt, at 100°C 6.06 cSt; viscosity index = 222; pour point (°C) = 9; acid number (mg KOH/g) 85; Iodine value = 102. Typical characteristics of linseed oil are = viscosity at 40°C = 25.15 cSt; viscosity index = 248; pour point (°C) Table -1 Typical Characteristics of Vegetable Oils (Table Removed) Accordingly the present invention provides a process for the preparation of lubricants based on hydrogenated vegetable oil which comprises degumming and refining the vegetable oil selected from the group consisting of rice bran oil, castor oil, linseed oil, pongamia oil, jatropha curcas oil, and combination thereof using a saturated hydrocarbon solvent having 5-8 carbon atoms preferably n-hexane, n-heptane, n-octane or isooctane mixture of saturated hydrocarbon solvent with monohydric alcohol having 1-4 carbon atoms preferably ethanol or isopropanol, reacting the degummed purified vegetable oil with monohydric alcohol having 5-10 carbon atoms in presence of a catalyst to produce ester of vegetable oil and at least partially hydrogenating the ester of vegetable oil with hydrogen in presence of a hydrogenation catalyst and solvent to produce esterified hydrogenated vegetable oil having an iodine value no more than 160 and purifying the resultant liquid lubricant hydrogenated vegetable oil ester by removing the catalyst and solvent. In an embodiment of the present invention degumming and purification step comprises of mixing the vegetable oil with solvent or mixture of solvent and alcohol in the ratio of 1-5 wt/wt at 10-15°C, filtering the solution and removing the solvent and alcohol by distillation. In another embodiment of the present invention the ratio of hydrocarbon to monohydric alcohol is in the range of 2-8 wt./wt. In yet another embodiment of the present invention the degummed refined vegetable oil is reacted with a monohydric alcohol having 5-10 carbon atoms to form ester of vegetable oil. In still another embodiment of the present invention A process as claimed in claims 1 to 4 wherein the ester of vegetable oil is reacted with hydrogen in presence of a hydrogenating catalyst at 5-20 bar pressure at 30-200°C to produce hydrogenated vegetable oil ester having an iodine value of no more than 160. In still another embodiment of the present invention a modified unsaturated triacylglycerol oil comprising triacylglycerol which include at least one unsaturated fatty acyl chain modified by trans esterification with C5-C10 monohydric alcohol and atleast partially hydrogenated, wherein the unsaturated triacylglycerol oil (hydrogenated vegetable oil ester) has an iodine value of less than 160. In still another embodiment of the present invention hydrogenated vegetable oil ester prepared are suitable as lubricant base stock. In still another embodiment of the present invention lubricating base stock is suitable for preparing lubricant formulations for automotive and industrial applications such as gear oil, metal working lubricants, hydraulic oil, refrigeration oil, turbine oil and general purpose lubricants. In accordance with the present invention the rice bran oil and linseed oil are degummed and refined by dissolving them in n-heptane and cooling the solution to 10-15°C. The ratio of oil to n-heptane is in the range of 1-5 wt/wt. The gummy mass is filtered and the remaining clear solution containing oil and solvent is distilled to remove the solvent. The purified vegetable oil is obtained as residue after distillation. For purification of castor oil, isopropanol is used in place of n-heptane. Neem oil is purified by dissolving in a mixture of n-heptane and ethanol; the ratio of n-heptane to ethanol is in the range of 2-8. Other operating conditions remaining similar as that used in purification of rice bran oil. During the investigations it was found that esterification of vegetable oil improves the low temperature behaviour of lubricant base oil produced from vegetable oils by reducing the pour point. It will be apparent from the foregoing discussion that the present invention provides a modified vegetable oil and process for the preparation of the same. The present invention also provides a lubricant base oil, prepared from vegetable oil, suitable for preparing lubricant formulations for automotive and industrial applications such as gear oil, metal working fluids, hydraulic oil, turbine oil and general purpose lubricants. The following examples are illustrative of the present invention but are not intented to limit the scope of the invention. Example -1 Rice bran oil (1 kg) was mixed with 3 liter of n-heptane and the solution was kept at 15°C for 6h. The solution was then filtered to remove the suspended matter and gum. From the clear solution thus obtained n-heptane was distilled of. The purified rice bran oil was used to prepare the lubricant base stock by transesterification with ethyl hexanol. For transesterification 430 g of ethyl hexanol was heated with 7g of sodium at 120°C until a clear solution was obtained. 400 g of refined rice bran oil was added to the reaction mixture and refluxed at 180-190°C for 30h. Excess ethyl hexanol was removed by vacuum distillation, steam was passed through the contents at 120°C to hydrolyse the sodium ethyl hexanoate the contents from two layers. The lower layer was acidified with HC1 to pH-7. The upper layer was dissolved in toluene and water was distilled as toluene water azeotrope. The vegetable oil ester thus obtained was dried under vacuum at 130°C to remove unreacted ethyl hexanol and toluene. The dried ester was taken in stainless steel autoclave fitted with a stirrer and cooling arrangement. To this 8g of Raney Nickel and 400 g of n-heptane was added. The autoclave was closed and hydrogen was bubbled for 2h maintaining hydrogen pressure of 200 psi at 120°C. After depressurizing the solution was taken off filtered to remove the catalyst and distilled to remove n-heptane. The partially hydrogenated ethyl hexyl ester of rice bran oil thus obtained was treated with fullers earth to remove any acidity physico-chemical characteristics of partially hydrogenated ethyl hexyl ester of rice bran oil were estimated to be as follows: Viscosity index > 300 Pour point -2.0 Acid No. mg/KOH/g Iodine value 71 Oxidation stability at 95°C, 120 h : Viscosity at 100°C, (cSt) before and after test was 5.21 and 6.15 respectively. Example - 2 The procedure of example 1 was repeated except that rice bran oil was replaced with linseed oil. The characteristics of partially hydrogenated ethyl hexyl ester of linseed oil obtained were estimated and given below: Viscosity Index 186 Pour Point, °C -21 Acid No.,mg KOH/g 12.59 Iodine value 115 Example - 3 The procedure of example - 1 was repeated except that rice bran oil was replaced with neem oil. The characteristics of partially hydrogenated ethyl hexyl ester of neem oil thus obtained were estimated and are given below: Viscosity Index 170 Pour point, °C -9 Acid No. mg KOH/g Iodine value 23 Oxidation stability at 95°C, 120 h : Viscosity at 100°C before and after test was 5.18 and 6.02 respectively. Example - 4 The procedure of example-1 was repeated except that rice bran oil was replaced with castor oil and hydrogen was bubbled for 1 h. The physico-chemical characteristics of partially hydrogenated ethyl hexyl ester of castor oil were estimated and are given below: Viscosity Index 188 Pour point, °C -18 Acid No., mg KOH/g Iodine value 5 We Claim: 1. A process for the preparation of lubricants based on hydrogenated vegetable oil which comprises degumming and refining the vegetable oil selected from the group consisting of rice bran oil, castor oil, linseed oil, pongamia oil, jatropha curcas oil, and combination thereof using a saturated hydrocarbon solvent having 5-8 carbon atoms preferably n-hexane, n-heptane, n-octane or isooctane mixture of saturated hydrocarbon solvent with monohydric alcohol having 1-4 carbon atoms preferably ethanol or isopropanol at a temperature of 10-15°C, reacting the degummed purified vegetable oil with monohydric alcohol having 5-10 carbon atoms in presence of a catalyst to produce ester of vegetable oil and at least partially hydrogenating the ester of vegetable oil with hydrogen in presence of a hydrogenation catalyst and solvent at 5-20 bar pressure and at 30-200°C to produce esterified hydrogenated vegetable oil having an iodine value no more than 160 and purifying the resultant liquid lubricant hydrogenated vegetable oil ester by removing the catalyst and solvent. 2. A process as claimed in claim 1, wherein degumming and purification step comprises of mixing the vegetable oil with solvent or mixture of solvent and alcohol in the ratio of 1-5 wt/wt, filtering the solution and removing the solvent and alcohol by distillation. 3. A process as claimed in claims 1 and 2, wherein the ratio of hydrocarbon to monohydric alcohol is in the range of 2-8 wt./wt. 4. A process as claimed in claims 1 to 3 wherein the degummed refined vegetable oil is reacted with a monohydric alcohol having 5-10 carbon atoms to form ester of vegetable oil. 5. A process as claimed in claims 1 to 4, wherein a modified unsaturated triacylglycerol oil comprising triacylglycerol which include at least one unsaturated fatty acyl chain modified by trans esterification with C5-C10 monohydric alcohol and atleast partially hydrogenated, wherein the unsaturated triacylglycerol oil (hydrogenated vegetable oil ester) has an iodine value of less than 160. 6. A process as claimed in claims 1 to 6 wherein hydrogenated vegetable oil ester prepared are suitable as lubricant base stock. 7. A process as claimed in claim 1 to 7 wherein lubricating base stock is suitable for preparing lubricant formulations for automotive and industrial applications such as gear oil, metal working lubricants, hydraulic oil, refrigeration oil, turbine oil and general purpose lubricants. 8. A process for the preparation of lubricants based on hydrogenated vegetable oils substantially as herein described with references to the examples.

Documents:

361-DEL-2004-Abstract-(11-08-2011).pdf

361-del-2004-abstract.pdf

361-DEL-2004-Claims-(11-08-2011).pdf

361-del-2004-claims.pdf

361-del-2004-Correspondence Others-(04-09-2012).pdf

361-DEL-2004-Correspondence Others-(11-08-2011).pdf

361-del-2004-correspondence-others.pdf

361-del-2004-correspondence-po.pdf

361-del-2004-Corrospondence Others-(16-12-2011).pdf

361-del-2004-description (complete).pdf

361-del-2004-form-1.pdf

361-del-2004-form-18.pdf

361-del-2004-form-2.pdf

361-DEL-2004-Form-3-(11-08-2011).pdf

361-del-2004-form-3.pdf

361-del-2004-form-5.pdf

361-del-2004-GPA-(04-09-2012).pdf

361-del-2004-PA(16-12-2011).pdf