阅读说明：本技术 一种双酯衍生物型润滑油基础油及其制备方法 (Diester derivative type lubricating oil base oil and preparation method thereof ) 是由 向硕 卢鹏 何燕 杨鑫 苏鹏 李学彬 陈浩 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种双酯衍生物型润滑油基础油及其制备方法,属于润滑油技术领域。该制备方法包括取环氧脂肪酸甲酯与短链脂肪醇在磷酸催化下,反应温度为80～110℃下反应15～25h,制得双酯衍生物,且双酯衍生物的结构式如下式I所示：其中,上述式I中R取自,正丙基、正丁基、正戊基、异戊基、正己基中任意一种。本发明设计的双酯衍生物在润滑油基础油中具备较好的应用。(The invention discloses diester derivative type lubricating oil base oil and a preparation method thereof, belonging to the technical field of lubricating oil. The preparation method comprises the following steps of reacting epoxy fatty acid methyl ester with short-chain fatty alcohol at the temperature of 80-110 ℃ for 15-25 h under the catalysis of phosphoric acid to obtain diester derivatives, wherein the structural formula of the diester derivatives is shown as the following formula I: wherein R in the formula I is selected from any one of n-propyl, n-butyl, n-pentyl, isopentyl and n-hexyl. The diester derivative designed by the invention has better application in the base oil of lubricating oil.)

1. A diester derivative, characterized in that it has the following chemical formula:

wherein, R in the formula I is selected from any one of n-propyl, n-butyl, n-pentyl, isopentyl or n-hexyl.

2. The diester derivative according to claim 1 wherein R is isoamyl.

3. The preparation method of the diester derivative of claim 1, wherein the diester derivative is prepared by reacting epoxy fatty acid methyl ester with short-chain fatty alcohol at 80-110 ℃ for 15-25 h under the catalysis of phosphoric acid.

4. The preparation method of the diester derivative as claimed in claim 3, wherein the molar ratio of the epoxy fatty acid methyl ester to the short-chain fatty alcohol is (3-5): 1.

5. The method for preparing the diester derivative as claimed in claim 4, wherein the molar ratio of the epoxidized fatty acid methyl ester to the short-chain fatty alcohol is 4: 1.

6. The method for preparing the diester derivative according to any one of claims 3 to 5, wherein the amount of the phosphoric acid is 1.5 to 3.0% of the total mass of the epoxidized fatty acid methyl ester and the short-chain fatty alcohol.

7. A diester derivative type lubricant base oil is characterized by comprising one or two or more than two of the structural formulas shown as the following formula I:

wherein R in the formula I is selected from n-propyl, n-butyl, n-pentyl, isopentyl or n-hexyl.

8. The diester derivative type lubricant base oil of claim 8, wherein R in formula I is isopentyl.

9. Use of the diester derivative of claim 1 or 2 in a lubricant base oil.

Technical Field

The invention relates to novel base oil, belongs to the technical field of lubricating oil, and particularly relates to diester derivative type lubricating oil base oil and a preparation method thereof.

Background

In recent years, there has been increasing interest in developing and developing eco-friendly lubricants as alternatives to traditional mineral-based lubricants that will play an important role in future industrial and traffic developments. The traditional mineral-based lubricant has the defects of poor biodegradability and high toxicity, so that the traditional mineral-based lubricant is poor in environmental friendliness and can cause huge ecological disasters once leaked into the environment. Therefore, it would be of great ecological significance to reduce the use of traditional mineral-based lubricants or to find alternatives thereto.

The waste cooking oil is waste of animal and vegetable oil after repeated high-temperature heating, and contains a certain amount of toxic and harmful substances such as phenols and ketones and carcinogenic substances such as polycyclic aromatic hydrocarbon and benzopyrene. Once introduced into the environment or ingested by the human body, these toxic and harmful substances cause serious environmental disasters and pose serious threats to the human life health. Under the situation that global energy crisis and environmental protection are increasingly rising, the resource utilization is carried out on the waste cooking oil, mineral oil is replaced to be used as raw materials of production auxiliaries, surfactants, chemical raw materials, biodiesel, lubricating oil and the like, the waste is turned into wealth, the ecological environment can be improved, the energy crisis can be relieved, considerable economic benefits can be created, economic sustainable development is promoted, and the method has very important theoretical significance and practical significance. However, the triglyceride molecule structure of the basic component of the animal and vegetable oil contains C ═ C unsaturated double bond beta-CH active sites, and the triglyceride molecules are easy to generate the stacking effect at low temperature to form large crystals, so that the thermal oxidation stability, the hydrolysis stability and the low-temperature flow property of the animal and vegetable oil are not ideal, and the large-scale production and the wide application of the triglyceride as the lubricating oil base oil are limited. At present, the modification methods of animal and vegetable oils include biological modification, chemical modification, additive modification and the like, wherein the chemical modification includes hydrogenation, esterification, epoxidation, substitution, acylation, Friedel-Crafts alkoxylation, or a combination of the above modification methods.

The Chinese invention patent application (application publication date: CN109055019A, application publication number: 2018-12-21) discloses a method for preparing lubricating oil base oil by chemically modifying waste cooking oil, belonging to the technical field of chemical engineering. Firstly, carrying out ester exchange reaction on pretreated waste cooking oil and methanol under the action of a catalyst to obtain fatty acid methyl ester, carrying out in-situ epoxidation reaction on the fatty acid methyl ester and formic acid in the presence of the catalyst to obtain epoxy fatty acid methyl ester, and finally carrying out epoxy bond ring-opening reaction on the epoxy fatty acid methyl ester and acid anhydride in the presence of the catalyst and under the protection of nitrogen to prepare the triester derivative lubricating oil base oil. The invention develops a new method for resource utilization of the waste cooking oil, the prepared triester derivative improves the low-temperature fluidity and the thermal oxidation stability of the waste cooking oil, and the triester derivative is used as a substitute of the base oil of the traditional mineral-based lubricating oil, thereby changing waste into valuable, improving the ecological environment, relieving the energy crisis and having stronger popularization and application values.

CN 109055019A: the method uses waste cooking oil as a raw material, and obtains epoxy fatty acid methyl ester after modification through ester exchange reaction and epoxidation reaction in sequence, and a series of triester derivatives are obtained by ring-opening modification of the epoxy fatty acid methyl ester by adopting (C1-C6) anhydride and are used as lubricating oil base oil. On the basis of the application, the invention adopts (C1-C6) short-chain fatty alcohol to carry out ring-opening modification on epoxy fatty acid methyl ester to obtain a series of diester derivatives as the lubricating oil base oil. Therefore, the application is different from CN109055019A in technical scheme and is a novel epoxy fatty acid methyl ester ring-opening modification method, the obtained diester derivative is also different from the triester derivative obtained in CN109055019A, and the diester derivative and the triester derivative belong to different types of ester lubricating oil base oil.

Disclosure of Invention

In order to solve the technical problems, the invention provides diester derivative type lubricating oil base oil and a preparation method thereof. The invention researches the influence of the carbon chain length of the short-chain fatty alcohol on the friction properties such as extreme pressure property, friction reducing property, wear resistance and the like of the diester derivative, and the result shows that the extreme pressure properties of all products are greatly improved compared with the raw materials, but the extreme pressure properties are not greatly related to the carbon chain length; as the carbon chain of the alcohol increases, the friction coefficient of the diester derivative tends to decrease and then increase; with the increase of the carbon chain of the alcohol, the abrasion spot diameter of the alcohol is correspondingly reduced, and the abrasion resistance is enhanced; in addition, the diester derivative has better sensitivity to ZDDP, and the tribological performance of the diester derivative is better improved.

In order to achieve the purpose, the invention discloses a diester derivative which has the following chemical structural formula:

wherein R in the formula I is selected from any one, any two, any three, any four or more of n-propyl, n-butyl, n-pentyl, isopentyl and n-hexyl.

Further, R is isopentyl.

In order to better achieve the technical purpose of the invention, the invention also discloses a preparation method of the diester derivative, wherein the diester derivative is prepared by reacting epoxy fatty acid methyl ester with short-chain fatty alcohol at the reaction temperature of 80-110 ℃ for 15-25 h under the catalysis of phosphoric acid.

Further, the molar ratio of the epoxy fatty acid methyl ester to the short-chain fatty alcohol is (3-5): 1.

Further, the molar ratio of the epoxy fatty acid methyl ester to the short-chain fatty alcohol is 4: 1.

Further, the using amount of the phosphoric acid is 1.5-3.0% of the total mass of the epoxy fatty acid methyl ester and the short-chain fatty alcohol.

The invention also discloses diester derivative type lubricating oil base oil which comprises one or two or more than two of the structural formulas shown in the following formula I:

wherein R in the formula I is selected from n-propyl, n-butyl, n-pentyl, isopentyl or n-hexyl.

Further, in the formula I, R is isoamyl.

In addition, the invention also discloses application of the diester derivative in the lubricating oil base oil.

The beneficial effects of the invention are mainly embodied as follows:

the invention investigates the influence of the carbon chain length of the short-chain fatty alcohol on the friction properties such as extreme pressure property, friction reducing property, wear resistance and the like of the diester derivative, and the result shows that the extreme pressure property of all products is greatly improved compared with the raw materials, particularly i-WAD, the maximum non-seizure load of the i-WAD reaches 1020N, and the i-WAD is not greatly related to the carbon chain length; as the carbon chain of the alcohol increases, the coefficient of friction of the diester derivative tends to decrease and then increase. The friction coefficient is correspondingly increased along with the increase of the load, but the friction coefficient of part of products is reduced under the load of 200N to 400N; with the increase of carbon chain of alcohol, the wear-resisting performance is enhanced and the wear-resisting performance is correspondingly reduced, so that the diester derivative designed by the invention can be used as the base oil of lubricating oil.

Drawings

FIG. 1 is a graph of the linear dependence of the effect of reaction temperature on the epoxy value of the product;

FIG. 2 is a graph of the linear dependence of reaction time on the effect of product epoxy value;

FIG. 3 is a graph of the linear dependence of catalyst loading on the product epoxy value;

FIG. 4 is an infrared spectrum of epoxidized fatty acid methyl ester;

FIG. 5 is a nuclear magnetic hydrogen spectrum of epoxidized fatty acid methyl ester;

FIG. 6 is an infrared spectrum of a ring-opened derivative of n-hexanol;

FIG. 7 is a nuclear magnetic hydrogen spectrum of the product of FIG. 6;

FIG. 8 is a graph comparing the oxidation stability of the products of FIG. 6;

FIG. 9 is a graphical representation of the PB values of the products of FIG. 6;

FIG. 10 is a graph of the change in coefficient of friction of the product of FIG. 6;

FIG. 11 is a plot of the change in the wear scar diameter of the product of FIG. 6;

FIG. 12 is a graph of the morphology of the product of FIG. 6 and a 150N steel ball bump.

Detailed Description

In order to better explain the invention, the following further illustrate the main content of the invention in connection with specific examples, but the content of the invention is not limited to the following examples.

The experimental reagents and instruments used in the designed examples of the present invention are shown in tables 1 and 2 below;

TABLE 1 major reagents and drugs and their manufacturers

TABLE 2 Main instruments and their manufacturers

Example 1

This example discloses the preparation of diester derivatives by ring-opening reaction of epoxidized fatty acid methyl esters:

taking 50mL of epoxy fatty acid methyl ester, measuring 74mL of n-hexanol according to the molar ratio of alcohol to oil of 4:1, mixing the epoxy fatty acid methyl ester and the hexanol, adding the epoxy fatty acid methyl ester and the hexanol into a three-neck flask, measuring a certain amount of phosphoric acid into a reactant, heating the reactant by using an electromagnetic heating sleeve, opening a stirrer for stirring, and carrying out reflux reaction for 25 hours, wherein the reaction principle is as follows:

the epoxy value of the diester derivative prepared above was measured as follows:

(1) 0.1mol/L and 0.01mol/L sodium hydroxide solution are prepared.

(2) Preparing a hydrochloric acid-acetone solution: according to the volume, 1 part of hydrochloric acid and 40 parts of acetone are mixed and are hermetically stored in a glass bottle for use.

(3) Preparing mixed indicating liquid: firstly, preparing 0.1% cresol red solution, then taking 10mL of 0.1% cresol red solution, adding 30mL of 0.1% thymol blue solution, and uniformly mixing. The solution is adjusted to be neutral by 0.1mol/L sodium hydroxide and 0.1mol/L hydrochloric acid solution.

(4) Accurately weighing 0.5-1 g of diester derivative, placing the diester derivative in a 250mL ground triangular conical flask, accurately adding 20mL of hydrochloric acid-acetone solution, sealing the flask, shaking uniformly, placing the flask in a dark place, and standing for 30 min. 5 drops of the mixed indicator solution were added and titrated to violet blue with 0.15mol/L sodium hydroxide standard solution while performing a blank test.

(5) And (3) calculating: the number of grams of oxygen in the oxirane group per 100g of sample is referred to as the epoxide number, and the epoxide number X is calculated according to the following mathematical relationship:

v-volume of sodium hydroxide standard solution consumed in the blank (mL);

V₁-volume (mL) of sodium hydroxide standard solution consumed for the sample test;

V₂-determining the volume (mL) of acid value-depleted sodium hydroxide standard solution in the sample;

n-concentration of sodium hydroxide standard solution (mol/L);

w-weight of sample (g);

g-weight (G) of sample at the time of measuring acid value;

0.016-milliequivalent of oxygen.

The allowable error of the above measurement results is shown in table 3;

TABLE 3 determination of tolerance for epoxy value

(6) And (3) post-treatment of the product:

removal of catalyst phosphoric acid

Phosphoric acid is readily soluble in water, the product is added to 50mL of distilled water and poured into a separating funnel, the shaking and shaking are carried out, the gas is simultaneously released, the lower water layer is discharged after standing for a period of time, and the experiment is repeated for 3 times.

Removing excess alcohol from the product

And installing and connecting a rotary evaporator and a circulating water vacuum pump, and introducing condensed water. And (3) turning on a circulating water vacuum pump power supply and a rotary evaporator power supply, adjusting the vacuum pressure to be 0.2MPa, wherein the boiling point corresponding to n-hexanol is 103 ℃, and adjusting the heating temperature of the rotary evaporator to be 103 ℃. And opening a sample injection switch. The sample was loaded into a spinner flask and heated in an oil bath until no further increase in the flask was obtained in which the evaporation product, n-hexanol, was collected. After the evaporation is finished, the power switch, the circulating pump switch and the vacuum pump air exhaust switch are turned off, the sample is collected, the sample collecting bottle is cleaned, and the bottle is rotated.

Dry moisture content

And pouring the product into a beaker, adding anhydrous magnesium sulfate, then placing the product into a vacuum drying oven, standing for 24 hours, filtering to remove the anhydrous magnesium sulfate serving as a drying agent, and obtaining oily liquid, namely the diester derivative.

Example 2

Exploring various factors influencing the ring-opening modification of epoxy fatty acid methyl ester

(1) Influence of reaction temperature

Taking 50mL of epoxy fatty acid methyl ester, measuring 74mL of n-hexanol according to the molar ratio of alcohol to oil of 4:1, mixing the epoxy fatty acid methyl ester and the hexanol, adding the epoxy fatty acid methyl ester and the hexanol into a three-neck flask, measuring 1.0g of phosphoric acid as a catalyst, adding the phosphoric acid and the catalyst into a reactant, respectively adjusting the reaction temperature to 80 ℃, 90 ℃, 100 ℃ and 110 ℃, starting a stirrer for stirring, and carrying out reflux reaction for 25 hours. After the reaction was completed, the epoxy values of the products were measured, respectively, and the results are shown in FIG. 1.

As can be seen from FIG. 1, as the reaction temperature increases, the epoxy value of the product decreases first and then increases, the reaction is the lowest around 100 ℃, the reaction is relatively more complete, so we choose the reaction temperature to be 100 ℃. Since the selected alcohols all have boiling points between 110 and 160 c, except for the boiling point of n-propanol of 97c, it was found that the ring opening efficiency at 90 c is high, probably because 100 c exceeds its boiling point, causing partial volatilization, and thus the reaction temperature for n-propanol was maintained at 90 c and the remaining alcohol reaction temperature was 100 c.

(2) Influence of reaction time

Taking 50mL of epoxy fatty acid methyl ester, measuring 74mL of n-hexanol according to the molar ratio of alcohol to oil of 4:1, mixing the two, adding the two into a three-neck flask, measuring 1.0g of phosphoric acid as a catalyst, adding the mixture into a reactant, adjusting the reaction temperature to be 100 ℃, starting a stirrer for stirring, respectively standing for 15h, 20h, 25h and 30h, and respectively measuring the epoxy value of the product after reaction, thus obtaining the result shown in the following figure 2.

As can be seen from FIG. 2, the epoxy value decreases with increasing reaction time, and the epoxy value does not change much from 25h to 30h, indicating that the degree of ring opening does not change much, so we chose the most suitable reaction time to be 25h for time saving.

(3) Influence of the amount of catalyst

Taking 50mL of epoxy fatty acid methyl ester, measuring 74mL of n-hexanol according to the molar ratio of alcohol to oil of 4:1, mixing the epoxy fatty acid methyl ester and the hexanol, adding the epoxy fatty acid methyl ester and the hexanol into a three-neck flask, respectively measuring 1.5 wt.% of phosphoric acid, 2.0 wt.% of phosphoric acid, 2.5 wt.% of phosphoric acid and 3.0 wt.% of phosphoric acid as catalysts, adding the catalysts into the reactants, adjusting the reaction temperature to be 100 ℃, opening a stirrer for stirring, and standing for 25 hours. The epoxy values of the products after the reactions were measured, respectively, to obtain the following FIG. 3.

As can be seen from fig. 3, as the amount of catalyst used increases, the epoxy value tends to decrease first and then increase, and when the amount of catalyst used is 2.5 wt.%, the epoxy value is the smallest, which indicates the highest ring opening efficiency, so we choose the amount of catalyst used to be 2.5 wt.%.

From the above one-factor experiment, the optimal reaction conditions can be found as follows: the reaction temperature was 100 ℃, the reaction time was 25h, and the catalyst amount was 2.5 wt.%.

Example 3

This example performs structural characterization on the diester derivatives prepared in the above examples:

wherein, the structural representation of the epoxidized fatty acid methyl ester is shown in figure 4 and figure 5.

Wherein, FIG. 4 is an infrared spectrum of epoxidized fatty acid methyl ester. The following results can be obtained by analyzing the characteristic peaks: 723cm^-1(CH₂Out-of-plane bending vibration), 1113cm^-1(symmetrical stretching vibration of ether group C-O-C), 1169, 1246 and 1196cm^-1(ester group-COO-stretching vibration), 1362cm^-1(CH₃Symmetric bending vibration), 1462cm^-1(CH₂Bending vibration), 1739cm^-1(CH₂Carbonyl C ═ O stretching vibration), 2922cm^-1And 2853cm^-1(CH₃Bending vibration).

FIG. 5 is a nuclear magnetic hydrogen spectrum of epoxidized fatty acid methyl ester. Analysis of this we can get: 0.9ppm (3H, -CH)₃),1.3ppm(20H,-CH₂)，1.5ppm(4H,-CH₂CH(O)CHCH₂-),1.6ppm(2H,-CH₂CH₂CO₂CH₃),2.3ppm(2H，-CH₂CO₂CH₃)，2.9ppm(2H,-CH(O)CH-)。

The structural characterization of the n-hexanol ring-opening diester derivative is shown in fig. 6 and 7.

As can be seen from fig. 6, the following results were obtained by analyzing the characteristic peaks: 724.36cm^-1(CH₂Out-of-plane bending vibration), 1057.19cm^-1(C-OH Primary alcohol), 1245.85cm^-1,1174.63cm^-1(ester group-COO-stretching vibration) 1378.16cm^-1(CH₃Symmetric bending vibration), 1464.97cm^-1(CH₂Bending vibration), 1737.56cm^-1(CH₂Carbonyl C ═ O stretching vibration), 2924.53cm^-1And 2855.15cm^-1(CH₂Carbonyl C ═ O stretching vibration), 3355.19cm^-1(-OH). From a comparison of the two, we can see that the ring opening is followed by 3355cm^-1An OH peak, 1057.19cm^-1A primary alcohol peak at 1737.56cm was observed^-1CH of (A)₂The formation of the ring-opened product was judged based on the significant decrease in carbonyl C ═ O.

As can be seen from fig. 7, we can obtain: 0.9ppm (-CH)₃-OH dilute solution), 1.3ppm (, -CH)₂)，1.5ppm(-CH₂CH(O)CHCH₂-),1.6ppm(-CH₂CH₂CO₂CH₃),2.3ppm(-CH₂CO₂CH₃) 2.9ppm (-CH (O) CH-),4.1ppm (-OH, concentrated solution). From FIG. 7, it can be seen that the peak at 0.9ppm is significantly increased due to the ring-opening reaction to produce-OH and-CH₃And a peak of a concentrated-OH solution appears at 4.1 ppm.

Example 5

Taking epoxy fatty acid methyl ester and n-butanol according to a molar ratio of 4:1 and reaction conditions: the reaction temperature is 100 ℃, the reaction time is 25h, the catalyst dosage is 2.5 wt.%, and the target product is prepared by reaction.

Example 6

Taking epoxy fatty acid methyl ester and n-amyl alcohol according to a molar ratio of 4:1, and reaction conditions: the reaction temperature is 100 ℃, the reaction time is 25h, the catalyst dosage is 2.5 wt.%, and the target product is prepared by reaction.

Example 7

Taking epoxy fatty acid methyl ester and isoamylol according to a molar ratio of 4:1 and reaction conditions: the reaction temperature is 100 ℃, the reaction time is 25h, the catalyst dosage is 2.5 wt.%, and the target product is prepared by reaction.

Example 8

Taking epoxy fatty acid methyl ester and n-propanol according to a molar ratio of 4:1 and reaction conditions: the reaction temperature is 90 ℃, the reaction time is 25h, the catalyst dosage is 2.5 wt.%, and the target product is prepared by reaction.

Example 9

In this example, the physical and chemical properties of diester derivatives such as viscosity, acid value, low-temperature fluidity, and thermal oxidation stability were examined.

The epoxy fatty acid methyl ester is called EFAME for short, the N-propanol ring-opening product is called BAD for short, the N-butanol ring-opening product is called DAD for short, the N-pentanol ring-opening product is called WAD for short, the isoamyl alcohol ring-opening product is called i-WAD for short, the N-hexanol ring-opening product is called JAD for short, and in addition, 150N base oil is selected for comparison. 150N base oil is hydrogenated, belongs to group III base oil, is prepared by a full hydrogenation process, belongs to hydrogenated base oil with high viscosity index, and is also called unconventional base oil. It features high viscosity index and low volatility, and is mainly used in cosmetics, rubber and plastic products, lubricating grease and other fields.

(1) Viscosity Properties

The viscosity properties of the diester derivatives are shown in table 4;

TABLE 4 viscosity Properties of diester derivatives

As can be seen from table 4, the viscosity of the diester derivative is higher than that of the raw material EFAME at 100 ℃ and 40 ℃, and the viscosity of the product decreases with the increase of the carbon chain length, but the viscosity increases with the introduction of the branched chain, which is caused by the increase of the molecular weight and the introduction of the branched chain to change the original molecular structure; on the other hand, 150N group III base oil with high viscosity index has viscosity index of 107, i-WAD also has viscosity index of 107, and other diester derivatives have viscosity index of 85-95 and have higher viscosity index.

(2) Acid value

The acid value and the base value of GB/T1668-2008 petroleum products and lubricants are mainly used for measurement. The measurement results are shown in Table 5.

TABLE 5 acid value of diester derivatives

As can be seen from Table 5, both EFAME and the diester derivative had lower acid values than the experimental spent cooking oil (acid value 114.16 mgKOH/g); as the carbon chain increases, the acid value of the diester derivative decreases, and the lowest acid value is JAD (acid value 0.26mgKOH/g), which is close to 150N.

(3) Low temperature flow properties

Pour points were determined according to the national standard GB/T3535-2006. The measurement results are shown in Table 6.

TABLE 6 pour points of diester derivatives

As can be seen from Table 6, EFAME has a pour point of 8.5 deg.C, and the diester derivative thereof has a pour point which decreases with increasing carbon chain length, while the presence of a branched chain lowers the pour point even further, because the introduction of an alkyl group having an appropriate carbon chain length around the epoxy bond can reduce the unsaturation of the molecule, effectively preventing the accumulation of the molecule and thus forming crystalline macromolecules. On the other hand, the low temperature fluidity of i-WAD and JAD is already better than 150N, and it is believed that the low temperature performance of the diester derivatives will be better improved by adding the additives such as pour point depressant, etc., which improve the low temperature fluidity.

(4) Thermal oxidation stability

The method for measuring thermal oxidation stability of oil product mainly adopts pressure differential scanning calorimetry, and its principle is that a certain quantity of oil product is oxidized for a certain time at constant temp. in the presence of air (or oxygen) and metal catalyst, then the acid value, viscosity and formation condition of deposit are measured, so that it possesses the advantages of trace quantity, quick and accurate measurement. The test mainly measures the initial oxidation temperature (OT for short) and the fastest oxidation temperature (SM for short), and the higher OT and SM are, the better the thermal oxidation performance of the oil product is. The test conditions of the test were: the initial temperature is 40 ℃, the heating rate is 10 ℃/min, and the maximum temperature is 250 ℃. The test results are shown in fig. 8. As can be seen from fig. 8, most base oils have better oxidation stability than EFAME, and as the carbon chain grows, the oxidation stability tends to decrease first and then increase, and the side chain decreases the oxidation stability, probably because the longer side chain is vulnerable to thermal decomposition. It can also be found that the oxidation stability of JAD is better, equivalent to 150N, and the oxidation stability of other base oils is slightly lower than 150N, and the specific experimental data are shown in Table 7.

TABLE 7 Oxidation stability Properties of diester derivatives

(5) Extreme pressure performance

Maximum no-seizing load P_BThe maximum load at which seizure of the steel ball does not occur under the predetermined conditions when the extreme pressure performance of the lubricant is measured by a four-ball machine is shown. P_BThe magnitude of the value represents the oil film strength. The conditions for the measurement were: the rotation speed is 1450rpm, the oil temperature is room temperature, the time is 10s, and the load is changed according to the performance of the test oil. Experimentally determined P_BThe values are shown in fig. 9.

As can be seen from FIG. 9, the maximum non-seizure load of EFAME is 667N, the maximum non-seizure load of base oil 150N is 883N, while the maximum non-seizure load of diester derivatives synthesized by ring-opening modification of EFAME is 834 to 1020N, all the extreme pressure properties of the products are greatly improved compared with the raw materials, and most of the extreme pressure properties of the products are better than 150N, especially i-WAD, the maximum non-seizure load of which reaches 1020N, which is high without adding additives. The data in figure 9 also shows that extreme pressure performance is not too strongly correlated with the carbon chain length of the alcohol, but the presence of a branch improves extreme pressure performance, as shown in table 8.

TABLE 8 extreme pressure Properties of diester derivatives

Diester derivatives	PBvalue/N
		EFAME	667
BAD	932
		DAD	883
WAD	932
		i-WAD	1020
JAD	834
		150N	883

(6) Antifriction property

The test conditions were: the rotation speed is 1200rpm, the oil temperature is room temperature, the time is 30min, the load is 100-:

it can be seen from FIG. 10 that the coefficient of friction of the diester derivative was reduced from that of EFAME under 100N, 200N and 400N loads, indicating that the ring-opening modification has a certain effect on improving the antifriction properties. Compared with 150N mineral base oil, 150N has the smallest friction coefficient under the load of 100N, but the friction reducing effect of part of diester derivative exceeds 150N along with the increase of the load, for example, JAD has a friction coefficient smaller than 150N under the load of 200N, WAD, i-WAD has a friction coefficient smaller than 150N under the load of 400N, which shows that the friction reducing performance of the diester derivative is equivalent to 150N under the high load condition. On the other hand, as the carbon chain of the alcohol increases, the friction coefficient of the diester derivative tends to decrease and then increase. The friction coefficient is correspondingly increased with the increase of the load, but in fig. 10, it can be seen that the friction coefficient of part of the sample is reduced when the load is increased from 200N to 400N, probably because the molecular film generating the friction reducing effect is easy to be damaged as the temperature is increased with the increase of the load, but the forming speed is also increased, when the damage and the generation of the molecular film form a dynamic balance, more molecular films are used for reducing the friction, so that the friction reducing efficiency is increased, and the friction coefficient is reduced, and the specific data are shown in table 9.

TABLE 9 change in coefficient of friction of diester derivatives under different loads

(7) Abrasion resistance

The test conditions were: the rotating speed is 1200rpm, the oil temperature is room temperature, the time is 30min, the load is 400N, and the test result is shown in FIG. 11:

as can be seen from fig. 11, as the pressure increases, the wear-leveling diameter increases accordingly, and as the carbon chain of the alcohol increases, the wear-leveling diameter decreases accordingly, which may be due to the increase in the oil film thickness caused by the increase in the molecular weight, so that the anti-wear performance is enhanced. It can be found that at low load, the antiwear performance of 150N is better than that of the diester derivative, but at a certain increased load, the antiwear performance of the diester derivative exceeds 150N, which indicates that the diester derivative is more suitable for use under a larger load, and the specific data are shown in table 10.

TABLE 10 change in the scrub spot diameter of diester derivatives under different loads

(8) Surface topography analysis of steel ball grinding spots

The diester derivative and 150N were analyzed for the apparent wear marks using a scanning electron microscope, as shown in FIG. 12, at a magnification of 1000. The measurement conditions for obtaining the abrasion stains were: the rotation speed is 1200rpm, the oil temperature is room temperature, the time is 30min, and the load is 400N.

As can be seen from fig. 12, when the surface of the abrasion mark is enlarged 1000 times, the abrasion mark of EFAME is more obvious and also relatively deep, the abrasion mark of diester derivative and 150N is relatively shallow, and the abrasion mark of BAD is relatively gentle although the diameter of the abrasion mark is larger; the scratch of the i-WAD is not much different from the 150N depth profile, but the local abrasion of 150N is more serious; WAD and JAD scratched deeper than BAD, indicating that as the carbon chain length increased, the boundary lubrication performance did not increase, probably due to the absence of polar groups.

Example 10

This example uses zinc dialkyldithiophosphate (ZDDP) as an antiwear additive to examine the tribological properties of diester derivatives. Taking a diester derivative JAD as base oil, respectively dissolving 0 wt.%, 0.5 wt.%, 1 wt.% and 1.5 wt.% of T202 in the JAD, and inspecting the tribological properties by using an MM-W1A vertical universal friction wear tester. The extreme pressure performance is evaluated by the maximum non-seizing load PB, the friction reducing performance is evaluated by the friction coefficient, and the anti-friction performance is evaluated by the wear scar diameter.

(1) Extreme pressure performance: p of JAD after addition of 0.5 wt.% ZDDP_BThe value is obviously improved, which indicates that JAD has good sensitivity to ZDDP. The effect of the friction reducing agent is not as pronounced with increasing concentration, so extreme pressure effects are best at 1.0 wt.% additive.

(2) Antifriction performance: with increasing load, the friction coefficient of JAD under different concentrations of ZDDP increases; the friction coefficient of JAD decreased first and then increased with increasing additive concentration under the same load, indicating that the increase in JAD friction reducing effect at a concentration of 1.0 wt.% ZDDP is more pronounced.

(3) Abrasion resistance: as the load increases, the scrub spot diameter of the JAD increases; and at the same load, the JAD wear scar diameter decreases as the ZDDP concentration increases. The i-WAD wear scar diameter at a concentration of 1.5 wt.% ZDDP is the smallest, and the magnitude of the increase is smaller as the load increases, indicating that the JAD antiwear effect is better at a concentration of 1.5 wt.% ZDDP.

In conclusion, the carbon chain length of the short-chain fatty alcohol designed by the application has influence on the friction performances such as extreme pressure performance, antifriction performance, wear resistance and the like of the diester derivative. The result shows that the extreme pressure performance of all products is greatly improved compared with the raw materials, particularly the i-WAD has the maximum non-seizure load of 1020N and is not greatly related to the length of a carbon chain; as the carbon chain of the alcohol increases, the coefficient of friction of the diester derivative tends to decrease and then increase. The friction coefficient is correspondingly increased along with the increase of the load, but the friction coefficient of part of products is reduced under the load of 200N to 400N; as the carbon chain of the alcohol increases, the abrasion-resistant performance is enhanced due to the corresponding reduction of the diameter of the abrasion marks.

Meanwhile, ZDDP with different concentrations as a diester derivative JAD additive has influence on the tribological properties of extreme pressure, friction reduction, wear resistance and the like. The results show that the diester derivative JAD has better sensitivity to ZDDP, and the tribological performance of the diester derivative JAD can be better improved.

In addition, the present invention also tested the following experimental data; tables 11 to 13 show the data on the influence of the reaction temperature, the reaction time and the amount of catalyst used on the epoxy value,

TABLE 11 Effect of reaction temperature on the epoxy number of the product

TABLE 12 Effect of reaction time on product epoxy number

Time/h	Epoxide number/%)
		15	2.5
20	1.5
		25	0.7
30	0.5

TABLE 13 Effect of catalyst amount on the epoxy number of the product

Catalyst dosage/wt%	Epoxide number/%)
		1.5	0.76
2.0	0.67
		2.5	0.60
3.0	0.68

The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention. In addition to the above embodiments, the present invention has other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.