Use of an ionic liquid in the preparation of synthetic ester lubricating oil, synthetic ester lubricating oil and method for the preparation thereof

Abstract

The application provides application of an ionic liquid in preparation of synthetic ester lubricating oil, the synthetic ester lubricating oil and a preparation method thereof, and belongs to the technical field of synthetic ester lubricating oil.In the application, the ionic liquid can be used as a catalyst and can also play the role of a lubricating oil additive; after the reaction of catalytically synthesizing ester lubricating oil is completed, the ionic liquid does not need to be separated, which not only helps to significantly improve the performance of the ester lubricating oil, makes the synergistic lubricating effect of the synthetic ester lubricating oil and the ionic liquid reach the extreme effect, solves the scientific and technical problem of the negative influence of the residual catalyst on the synthetic ester base oil which exists widely at present, but also omits the catalyst separation step, shortens the preparation procedure of the synthetic ester, is favorable for industrialized mass production and promotes wide application; the application of one thing for two purposes provides a new idea for green synthesis of the synthetic ester lubricating oil.

Description

Technical Field

[0001] This invention relates to the field of synthetic ester lubricating oil technology, and in particular to the application of an ionic liquid in the preparation of synthetic ester lubricating oil, synthetic ester lubricating oil and its preparation method. Background Technology

[0002] With the advancement of science and technology, the requirements for lubricating oils are becoming increasingly stringent, leading to growing attention on the research and application of polyol ester lubricating oils with excellent tribological properties. Ester oils are the most widely used synthetic oils besides synthetic hydrocarbon oils, and among ester oils, polyol ester lubricating oils exhibit the best performance. Polyol esters are obtained by esterifying polyols such as neopentyl glycol, pentaerythritol, and trimethylolpropane with long-chain carboxylic acids (generally C8-C12 or oleic acid). They possess excellent heat resistance, oxidation resistance, lubricity, viscosity-temperature characteristics, and good volatility, and have been widely applied in the lubrication field.

[0003] In industrial production, the synthesis of polyol ester lubricating oils is currently generally carried out using concentrated sulfuric acid and p-toluenesulfonic acid as catalysts, employing traditional high-temperature heating methods. Because the catalysts used simultaneously perform oxidation, sulfonation, dehydration, and isomerization, a series of side reactions occur; the reaction products are complex, subsequent treatment is cumbersome, and a large amount of waste liquid is generated, polluting the environment; at the same time, the concentrated sulfuric acid catalyst severely corrodes equipment. These factors directly result in synthesized polyol esters with a darker color and lower purity, failing to yield high-quality products and directly affecting their application in industries with high product quality requirements. With increasing environmental awareness, the search for new, efficient, and environmentally friendly catalysts to replace traditional concentrated sulfuric acid and the research and development of new environmentally friendly synthesis methods have been hot topics in esterification reaction research. Research on the synthesis of polyol esters mainly focuses on the synthesis and selection of catalysts, including solid acid catalysts, functional carbon nanotube catalysts, ionic liquid catalysts, enzyme catalysts, and traditional catalysts such as sodium bisulfate. Currently, when using ionic liquid catalysts for ester oil synthesis, the catalysts need to be separated from the ester oil after the synthesis reaction, which causes significant inconvenience to industrial production. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an application of ionic liquids in the preparation of synthetic ester lubricating oils, synthetic ester lubricating oils, and a method for preparing the same. In this invention, the ionic liquid can be used as both a catalyst and a lubricating oil additive, and there is no need to separate the ionic liquid after the catalytic synthesis of ester lubricating oils is completed.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides an application of an ionic liquid in synthetic ester lubricating oil, wherein the ionic liquid is 1-butyl-3-methylimidazolium phosphate dibutyl ester salt or 1,3-dibutylimidazolium phosphate dibutyl ester salt.

[0007] The present invention also provides a synthetic ester lubricating oil, which is prepared by esterification reaction of raw materials including: organic alcohols, organic acids, dehydrating agents and catalysts, wherein the catalyst is 1-butyl-3-methylimidazolium phosphate dibutyl ester salt or 1,3-dibutylimidazolium phosphate dibutyl ester salt.

[0008] Preferably, the organic alcohol includes pentaerythritol, the organic acid includes hexanoic acid, and the dehydrating agent includes petroleum ether.

[0009] Preferably, the boiling range of the petroleum ether is 90–120°C.

[0010] Preferably, the molar ratio of the hydroxyl group in the organic alcohol to the carboxyl group in the organic acid is 1:1.

[0011] Preferably, the molar ratio of the hydroxyl group in the organic alcohol to the catalyst is 40 to 200:1.

[0012] Preferably, the esterification reaction is carried out at a temperature of 150–180°C for 5–10 hours.

[0013] Preferably, the esterification reaction is carried out at a temperature of 160–170°C for 6–7 hours.

[0014] This invention also provides a method for preparing the synthetic ester lubricating oil described in the above technical solution, comprising the following steps:

[0015] The synthetic ester lubricating oil is obtained by mixing organic alcohols, organic acids, a water-removing agent, and a catalyst and carrying out an esterification reaction.

[0016] Preferably, catalyst separation is not required after the esterification reaction is completed to obtain the synthetic ester lubricating oil.

[0017] This invention provides an application of an ionic liquid in synthetic ester lubricating oil, wherein the ionic liquid is 1-butyl-3-methylimidazolium phosphate dibutyl ester salt or 1,3-dibutylimidazolium phosphate dibutyl ester salt.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] In this invention, the ionic liquid can be used as both a catalyst and a lubricant additive. After the catalytic synthesis of ester-based lubricating oils, there is no need to separate the ionic liquid. This not only significantly improves the performance of ester-based lubricating oils and maximizes the synergistic lubrication effect between the synthesized ester-based lubricating oil and the ionic liquid, but also solves the scientific and technological problem of the negative impact of residual catalysts on synthetic ester base oils. Furthermore, it eliminates the catalyst separation step, shortens the ester synthesis process, and facilitates industrial-scale mass production and its widespread application. This invention offers a dual-purpose solution, providing a new approach to the green synthesis of ester-based lubricating oils. Attached Figure Description

[0020] Figure 1 Thermogravimetric curve of the ionic liquid BMP;

[0021] Figure 2 Thermogravimetric curve of ionic liquid BBP;

[0022] Figure 3 A microscopic photograph of the wear scar diameter of the upper sample under PETH lubrication;

[0023] Figure 4 An optical micrograph of the wear scar diameter of the upper sample under PETH+BMP lubrication;

[0024] Figure 5 An optical micrograph of the wear scar diameter of the upper sample under PETH+BBP lubrication. Detailed Implementation

[0025] This invention provides an application of an ionic liquid in synthetic ester lubricating oil, wherein the ionic liquid is 1-butyl-3-methylimidazolium dibutyl phosphate (BMP) or 1,3-dibutylimidazolium dibutyl phosphate (BBP).

[0026] The present invention does not have any special limitation on the source of the BMP and BBP, and they can be obtained by commercially available products or well-known preparation methods known to those skilled in the art.

[0027] In a specific embodiment of the present invention, the BMP is preferably a commercially available product, and the BBP is preferably prepared according to the method disclosed in "Tribological performance of phosphate ionic liquids as lubricants for steel-on-aluminum contact" (Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology, Qiao D et al. 2013, 227(11):1261-1271. DOI:10.1177 / 1350650113490146).

[0028] In this invention, the ionic liquid can be used as both a catalyst and a lubricant additive. After the catalytic synthesis of ester lubricating oil is completed, there is no need to separate the ionic liquid. This not only helps to significantly improve the performance of ester lubricating oil and maximizes the synergistic lubrication effect of the synthesized ester lubricating oil and the ionic liquid, but also solves the scientific and technological problem of the negative impact of residual catalyst on the synthesized ester base oil. Furthermore, it eliminates the catalyst separation step, shortens the synthesis ester preparation process, and is conducive to industrial mass production and promotes its widespread application.

[0029] The present invention also provides a synthetic ester lubricating oil, which is prepared by esterification reaction of raw materials including: organic alcohols, organic acids, dehydrating agents and catalysts, wherein the catalyst is 1-butyl-3-methylimidazolium phosphate dibutyl ester salt or 1,3-dibutylimidazolium phosphate dibutyl ester salt.

[0030] In this invention, the organic alcohol preferably includes pentaerythritol, the organic acid preferably includes hexanoic acid, and the dehydrating agent preferably includes petroleum ether.

[0031] In this invention, the boiling range of the petroleum ether is preferably 90-120°C.

[0032] In this invention, the molar ratio of the hydroxyl group in the organic alcohol to the carboxyl group in the organic acid is preferably 1:1.

[0033] In this invention, the molar ratio of the hydroxyl group in the organic alcohol to the catalyst is preferably 40 to 200:1, and when the organic alcohol is preferably pentaerythritol, the molar ratio of pentaerythritol to the catalyst is preferably 10 to 50:1.

[0034] In this invention, the temperature of the esterification reaction is preferably 150-180°C, more preferably 160-170°C, and the time is preferably 5-10 hours, more preferably 6-7 hours.

[0035] This invention also provides a method for preparing the synthetic ester lubricating oil described in the above technical solution, comprising the following steps:

[0036] The organic alcohols, organic acids, dehydrating agents, and catalysts are mixed and subjected to an esterification reaction to obtain the synthetic ester lubricating oil.

[0037] In this invention, the organic alcohol and organic acid are placed in a three-necked flask, and then the catalyst and dehydrating agent are added to carry out the esterification reaction.

[0038] Preferably, catalyst separation is not required after the esterification reaction is completed, to obtain the synthetic ester lubricating oil.

[0039] After the esterification reaction is completed, the present invention preferably involves rotary evaporation of the obtained esterification product to obtain the synthetic ester lubricating oil.

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] Example 1

[0042] Using the esterification reaction of pentaerythritol and hexanoic acid to obtain pentaerythritol tetrahexanoate (PETH) as a model reaction, pentaerythritol and hexanoic acid were weighed into a three-necked flask, and an ionic liquid (BMP or BBP) and petroleum ether (boiling range: 90-120℃, dehydrating agent) were added to carry out the esterification reaction. The product was then rotary evaporated to obtain pentaerythritol tetrahexanoate (PETH+BMP or PETH+BBP) containing the ionic liquid [BMP or BBP].

[0043] The acid value of the product was measured according to the national standard GB / T4945-2002, and the degree of esterification of the product was analyzed by the acid value. The formula for calculating the esterification rate is as follows:

[0044] Esterification rate (%) = [(1 - product acid value / initial acid value) × acid-alcohol molar ratio ÷ 4] × 100%

[0045] The catalytic performance results of the ionic liquids are shown in Table 1. Table 1 provides the screening data for the catalytic reaction conditions. It can be seen from Table 1 that both ionic liquids BMP and BBP have good catalytic activity, and the esterification reaction can reach an esterification rate of 97% or higher in 6 hours.

[0046] Table 1 Catalytic performance of bifunctional ionic liquids

[0047]

[0048] Thermal stability evaluation: Thermal stability was determined using a STA 449C Jupiter simultaneous TG-DSC. 10 mg of the bifunctionalized ionic liquid [(BHT-1)MIM][DEPH] was placed in the sample cell, and the test temperature ranged from 25 to 600 °C, with a temperature increase rate of 10 °C / min, under a nitrogen atmosphere.

[0049] Figure 1 This is the thermogravimetric curve of the ionic liquid BMP. Figure 2 Thermogravimetric curve of the ionic liquid BBP is shown below. Figures 1-2 It can be seen that neither of the two ionic liquids exhibited mass loss below 200℃. The thermal decomposition temperature of BMP was 259.1℃, and that of BBP was 266.3℃, indicating that these two ionic liquids have very good stability as catalysts in the catalytic esterification reaction system.

[0050] Tribological property evaluation of the product:

[0051] The friction coefficient f of pentaerythritol tetrahexanoate and the pentaerythritol tetrahexanoate containing ionic liquids BMP or BBP prepared in this example were tested using an SRV-IV micro-vibration friction and wear testing machine manufactured by Optimol Grease GmbH, Germany, under the conditions of 100℃, 25Hz frequency, 1mm amplitude, and 50N load for 30 minutes. The steel balls used in the test were GCr15 bearing steel with F=10mm, and the test specimens were GCr15 steel blocks with F24×7.9mm. The results are shown in Table 2. It can be seen that under the same experimental conditions, ionic liquids as additives to PETH can effectively lubricate steel-steel friction pairs, reduce the friction coefficient, and have a significant friction-reducing effect.

[0052] The wear scar diameters of the GCr15 steel block sample on pentaerythritol tetrahexanoate (Bailingwei) and the pentaerythritol tetrahexanoate SRV-IV product containing ionic liquid prepared in this example were measured using an OLYMPUS X41 metallurgical microscope manufactured by PredICT, USA. The results are shown in [Figure number missing]. Figures 3-5 And Table 2, Figure 3 An optical micrograph of the wear scar diameter of the upper sample under PETH lubrication. Figure 4An optical micrograph of the wear scar diameter of the upper sample under PETH+BMP lubrication. Figure 5 A microscopic image of the wear scar diameter of the upper sample under PETH+BBP lubrication. Figures 3-5 As can be seen from the results, under the same experimental conditions, pentaerythritol tetrahexanoate containing ionic liquid can effectively lubricate steel-steel friction pairs, reduce the wear scar diameter, and improve friction reduction performance.

[0053] Table 2. Friction coefficients and wear scar diameters of PETH and PETH lubricated with bifunctional ionic liquid [(BHT-1)MIM][DEPH].

[0054] Sample Name f (average coefficient of friction) d (wear scar diameter) / mm PETH 0.180 0.49 PETH+BMP 0.093 0.27 PETH+BBP 0.089 0.26

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a synthetic ester lubricating oil, characterized in that, Includes the following steps: An esterification reaction is carried out by mixing organic alcohols, organic acids, a dehydrating agent, and a catalyst to obtain the synthetic ester lubricating oil. The catalyst is 1-butyl-3-methylimidazolium phosphate dibutyl ester salt or 1,3-dibutylimidazolium phosphate dibutyl ester salt. The esterification reaction is carried out at a temperature of 160°C for 6-7 hours. The organic alcohol is pentaerythritol, the organic acid is hexanoic acid, and the dehydrating agent is petroleum ether. The molar ratio of hydroxyl groups in the organic alcohol to the catalyst is 40:1; After the esterification reaction is completed, no catalyst separation is required to obtain the synthetic ester lubricating oil.

2. The preparation method according to claim 1, characterized in that, The boiling range of the petroleum ether is 90~120℃.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the hydroxyl groups in the organic alcohols to the carboxyl groups in the organic acids is 1:1.

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