Lubricant base oil and method for preparing the same

Abstract

The present invention relates to a lubricant base oil containing an aromatic ester lubricant represented by Chemical Formula 1 and to a method for preparing the aromatic ester lubricant. By containing an aromatic ester lubricant, the lubricant base oil exhibits an excellent dispersibility and fluidity and is ecofriendly due to a high biodegradability. In addition, the method for preparing the aromatic ester lubricant does not generate such toxic substances as S, N, aromatic compounds and heavy metals and enables an easy control of the physical properties of a desired lubricant base oil by selecting a suitable alcohol compound to be introduced for an esterification reaction. ##STR00001##

Claims

1. A method for preparing a lubricant based oil comprising 1 wt % or more and less than 40 wt % of an aromatic ester lubricant of Chemical Formula 1 below, the method comprising: converting biomass fat to fatty acids; separating C16-C19 saturated fatty acids and unsaturated fatty acids from the fatty acids; esterifying the separated C16-C19 saturated fatty acids and unsaturated fatty acids with aromatic alcohol-based compounds selected from phenol, phenol substituted with a C1-C4 alkyl or C6-C10 aryl, naphthol, naphthol substituted with a C1-C4 alkyl or C6-C10 aryl, anthracene, and anthracene substituted with a C1-C4 alkyl or C6-C10 aryl, to obtain the aromatic ester lubricant of Chemical Formula 1, ##STR00007## and mixing the aromatic ester lubricant with a conventional lubricant based oil, where in the above Chemical Formula 1, R represents a C15-C18 alkyl group or alkenyl group, and Ar represents a phenyl group, a phenyl group substituted with a C1-C4 alkyl or C6-C10 aryl, a naphthyl group, a naphthyl group substituted with a C1-C4 alkyl or C6-C10 aryl, an anthracene group, or an anthracene group substituted with a C1-C4 alkyl or C6-C10 aryl wherein the lubricant based oil has a pour point of 40 to 5 C., viscosity at 100 C. of 3.5 to 6.5 cSt, and a cloud point of 40 to 5 C.

2. The method of claim 1, where the esterifying refers to an esterification reaction between carboxylic groups of the fatty acids and hydroxyl groups of the aromatic alcohol-based compounds.

3. The method of claim 1, wherein each of the aromatic alcohol-based compounds includes phenol, phenol substituted with a C1-C4 alkyl or C6-C10 aryl, naphthol, naphthol substituted with a C1-C4 alkyl or C6-C10 aryl, anthracene or anthracene substituted with a C1-C4 alkyl or C6-C10 aryl.

4. The method of claim 1, wherein the esterifying is carried out in a presence of an acid catalyst or base catalyst at a reaction temperature of about 30 to about 120 C., the acid catalyst is sulfuric acid (H.sub.2SO.sub.4), perchloric acid (HClO.sub.4), nitric acid (HNO.sub.3), or hydrochloric acid (HCl), having a purity of about 95% or more, and the base catalyst is potassium hydroxide (KOH), sodium hydroxide (NaOH), or sodium methoxide (CH.sub.3ONa), having a purity of about 95% or more.

5. The method of claim 1, wherein the fatty acids and acid catalyst are mixed in a weight ratio of about 1:about 0.01 to about 1:about 20 for the esterifying.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates an esterification reaction mechanism in a method for preparing a lubricant base oil according to a specific example of the present invention.

(2) FIG. 2 is a graph illustrating the analyzed result of an example of separating fatty acids from a palm fatty acid distillate specimen at various room temperatures.

DETAILED DESCRIPTION OF THE INVENTION

(3) Hereinafter, embodiments of the present invention will be described in more detail.

(4) Lubricant Base Oil Containing Aromatic Ester Lubricant

(5) A lubricant (lube) base oil according to a specific example of the present invention may contain an aromatic ester lubricant represented by the following Chemical Formula 1. In the present invention, a lubricant base oil is defined as an aromatic ester lubricant itself or a lubricating oil constituent containing an aromatic ester lubricant.

(6) ##STR00005##

(7) In the above Chemical Formula 1, R represents a C15-C18 alkyl group or alkenyl group, and Ar represents a phenyl group, a phenyl group substituted with a C1-C4 alkyl or C6-C10 aryl, a naphthyl group, a naphthyl group substituted with a C1-C4 alkyl or C6-C10 aryl, an anthracene group, or an anthracene group substituted with a C1-C4 alkyl or C6-C10 aryl.

(8) The aromatic ester lubricant represented by the above Chemical Formula 1 is derived from biomass, and it can serve as both a dispersant (which can make the base oil more mixable with additives) and a pour point depressant (which can improve the fluidity by reducing the pour point) in a lubricant base oil.

(9) As described above, the composition of a lubricant base oil of the present invention may contain an aromatic ester lubricant represented by the above Chemical Formula 1, or it may be prepared by mixing an aromatic ester lubricant represented by the above Chemical Formula 1 in a certain ratio with a conventional lubricant base oil.

(10) Specifically, the content of an aromatic ester lubricant represented by the above Chemical Formula 1 may be about 1 to about 40 wt % with respect to the total weight of the lubricating oil composition. When the content of the aromatic ester lubricant falls in the above range, the lube base oil can be expected to have properties that meet lubricating oil property standards. When the content is higher than about 40 wt %, the viscosity and viscosity index become insufficiently low, making the lubricant base oil difficult to be used as a lubricating oil, whereas the lubrication properties and mixing properties that are unique to an aromatic ester lubricant cannot be expected with the content of less than about 1 wt %.

(11) Specifically, the aromatic ester lubricant represented by the above Chemical Formula 1 may be an aromatic ester compound represented by the following Chemical Formula 2 or an aromatic ester compound represented by the following Chemical Formula 3. When R in the Chemical Formula 1 is such an alkyl group, a better oxidation stability can be secured.

(12) ##STR00006##

(13) The lubricant base oil according to a specific example of the present invention may have a pour point of about 40 to about 5 C., viscosity (at about 100 C.) of about 3.5 to about 6.5 cSt and a cloud point of about 40 to about 5 C. When the properties fall in the above mentioned ranges, the lubricant base oil can be used as a viscosity index improver, pour point depressant or additive that improves mixing between the base oil and additives.

(14) Method for Preparing Aromatic Ester Lubricant

(15) The method for preparing an aromatic ester lubricant according to a specific example of the present invention may include a conversion S10 of biomass fat to fatty acids, a separation S20 of C16-C19 saturated fatty acids and unsaturated fatty acids from the above fatty acids, and an esterification S30 of the above separated C16-C19 saturated fatty acids and unsaturated fatty acids with aromatic alcohols.

(16) During the conversion S10 of biomass fat to a fatty acid, as is generally known, triglycerides can be extracted from biomass by using a strong acid, a strong base, high temperature steam, etc., and the ester bonds of the above triglycerides can be hydrolyzed to be converted to fatty acids.

(17) The separation S20 of C16-C19 saturated fatty acids and unsaturated fatty acids from the above fatty acids is required because the above biomass-derived fatty acids include a variety of saturated fatty acids and unsaturated fatty acids. For example, palm oil-derived fatty acids may include myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, monoglycerides, and diglycerides. Such various kinds of fatty acids have boiling points different from one another, and thus, the fatty acids of interest can be selectively separated by extraction by fractional distillation.

(18) Therefore, C16-C19 unsaturated fatty acids may be separated by extraction from biomass-derived fatty acids through fractional distillation.

(19) The esterification S30 of the separated saturated fatty acids and unsaturated fatty acids with aromatic alcohols converts the molecular structure of the fatty acids into esters through the esterification reaction between carboxylic groups of the separated fatty acids and hydroxyl groups of aromatic alcohol-based compounds.

(20) When an ester lubricant contains a carboxylic functional group, it may cause corrosion in an engine. Therefore, stabilization of the chemical structure of the carboxylic functional group by forming an ester through an esterification reaction with an alcohol is required.

(21) FIG. 1 illustrates the reaction mechanism of the aromatic ester lubricant according to a specific example of the present invention. Referring to FIG. 1, an example in which an aromatic ester compound is prepared by reacting each of phenol and naphthol (both of which are aromatic alcohol-based compounds) with palmitic acid (which is a C16 saturated fatty acid) is provided.

(22) There is no limitation to the aromatic alcohol-based compound to be used in an esterification reaction, as long as it is an aromatic alcohol-based compound having a hydroxyl group. Examples of such a compound include phenol, phenol substituted with a C1-C4 alkyl or C6-C10 aryl, naphthol, naphthol substituted with a C1-C4 alkyl or C6-C10 aryl, anthracene, anthracene substituted with a C1-C4 alkyl or C6-C10 aryl, and so on.

(23) However, it may be beneficial to use low-price aromatic substances such as phenol, naphthol, etc. that are less expensive than the final product so that a volume gain effect can be expected through a preparation of esters with the use of such substances.

(24) The above esterification reaction is carried out in the presence of an acid catalyst or base catalyst at a reaction temperature of about 30 to about 120 C., where the above acid catalyst may be sulfuric acid (H.sub.2SO.sub.4), perchloric acid (HClO.sub.4), nitric acid (HNO.sub.3), or hydrochloric acid (HCl), all of which have a purity of about 95% or more, and the above base catalyst may be potassium hydroxide (KOH), sodium hydroxide (NaOH), or sodium methoxide (CH.sub.3ONa), all of which have a purity of about 95% or more, but they are not limited thereto.

(25) In the above esterification reaction, the fatty acids and acid/base catalyst may be mixed in a weight ratio of about 1:about 0.01 to about 1:about 20, specifically, about 1:about 0.03 to about 1:about 20 for an esterification reaction.

(26) Hereinafter, the present invention will be described in more detail with reference to examples, but such examples are merely for illustrative purposes and should not be construed as limiting the present invention.

Example

(27) A. Separation of Fatty Acids

(28) Fatty acids were separated from a 2 kg-palm fatty acid distillate (PFAD) specimen by a TBP cutting device at various reaction temperatures. The analyzed result of the above PFAD specimen is shown in FIG. 2, and, from the result, it was found that the PFAD specimen had a composition shown in the following Table 1. The PFAD specimen underwent cutting at 300 C., 355 C., 380 C., and each fatty acid was acquired in the amount shown in the following Table 2.

(29) TABLE-US-00001 TABLE 1 Type of fatty acids PFAD composition (wt %) Myristic acid (C14:0) 3 Palmitic acid (C16:0) 43 Oleic acid (C18:1), 38 Linoleic acid (C18:2), Linolenic acid (C18:3) Monoglyceride, diglyceride 16 Total 100

(30) B. Esterification Reaction

(31) 500 g of the PFAD separated and acquired in the composition shown in the above Table 1, as well as 292 g of 2-naphthol and 42 g of a 99% pure sulfuric acid, was introduced to a 2 L-flask, the reaction temperature was raised to 60 C., then the mixture was stirred at a speed of 200 rpm for 12 hours. Later, the above reactants were added to a 2 L-beaker and then quenched with a mixed solution of KOH/Ethanol/DI-water (38 g/100 cc/900 cc) while being stirred. The pH was measured to confirm that no residual acid was present in the above mixed solution, and then the mixed solution was set aside to wait for the temperature to decrease, added to a separatory funnel and maintained, and then, when the water layer and organic layer were separated from each other, the water layer was selectively removed. The separated organic layer was again added to the fractional distillation equipment (Spaltrohr HMS 300C by Fischer Technology, Inc.) and underwent cutting at 450 C. for a selective removal of unconsumed fatty acids and naphthol. 117 g of separated, unconsumed reactants and 629 g of the aromatic ester lubricant were acquired.

(32) Lubricating oil properties of the above aromatic ester compound were measured, and the result is shown in the following Table 2.

(33) TABLE-US-00002 TABLE 2 Viscosity Viscosity Cloud Pour TAN (40 C.) (100 C.) point point (PP) (mgKOH/kg) 48 cSt 7.9 cSt 36 C. 37 C. 0.04

(34) As seen in the Table 2 above, an aromatic ester compound prepared through an example of the present invention was found to have viscosity properties and a cloud point at the levels equivalent to those of conventional dispersants such as an alkyl naphthalene and can effectively lower the pour point. In addition, the result of TAN analysis in accordance with ASTM D664 standards was 0.04 mgKOH/kg, which could be interpreted as indicating that the reactants were mostly converted to esters.

(35) So far, examples of the present invention have been described, and it should be understood that the present invention is not limited by the above examples but can be prepared in various different forms and implemented in other specific forms by an ordinary person skilled in the art, without changing the technical scope or essential features of the present invention. Therefore, the examples described above should be understood as exemplary and non-limiting in every aspect.