A nitrogen-doped carbon quantum dot containing a nitrogen-containing heterocycle, and a preparation method and application thereof

Abstract

The application discloses nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots and a preparation method and application thereof, belongs to the field of lubricating materials, and relates to the following steps: dissolving a nitrogen-containing compound in an aldehyde compound, reacting in an alkaline solution, purifying and drying to obtain nitrogen-doped carbon quantum dots, connecting the nitrogen-doped carbon quantum dots with SOCl2 and a fatty diamine to obtain fatty diamine modified nitrogen-doped carbon quantum dots, adding the fatty diamine modified nitrogen-doped carbon quantum dots into nitrogen-containing heterocyclic acyl chloride, heating and reacting, and purifying and drying the product to obtain the nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots. The composite lubricating liquid provided by the application has excellent tribological properties, has corrosion resistance and thermal stability in an acid environment, and can be applied to many industries such as steel, chemical industry, petroleum, electric power, papermaking, oil refining, shipbuilding, storage and transportation.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lubricating materials, and particularly relates to nitrogen-doped carbon quantum dots with nitrogen-containing heterocycle modification as well as a preparation method and application thereof. BACKGROUND

[0002] In recent years, friction and wear has become one of the main factors causing material and energy consumption. Reducing the friction coefficient and wear rate is of great significance to improve the efficiency of metal processing technology and prolong the service life of mechanical equipment. Nanoparticles have become a research hotspot due to their unique physical and chemical properties and excellent tribological properties. However, due to the high specific surface area and surface energy of nanoparticles, they are prone to agglomeration in fluids. Therefore, developing stable nanolubricating oil with excellent lubricating properties is a permanent topic today.

[0003] Carbon dots (CDs) are a new type of graphene-based material, which has a shape similar to spherical particles with a diameter of about <10 nm. The small size of the graphene structure of CDs enables them to be stably dispersed in water and have lubricating effect. Shuangwang Ji et al. proved that CDs as lubricating oil additives have a lower friction coefficient and good wear resistance. Some researchers pointed out that CDs can be used as effective corrosion inhibitors to inhibit the corrosion of metals. Here, CDs have the potential to become a nanometer additive for water-based lubricants.

[0004] Generally, the synthesis methods of CDs can be divided into "top-down" and "bottom-up" methods. After nearly 20 years of rapid development, by selecting appropriate precursors, functional reagents and synthesis methods, the composition, structure, morphology and particle size of carbon quantum dots CQDs can be artificially designed and controlled. Surface functionalization and element doping of CQDs and their application in the field of lubrication are important development directions in the future. Nitrogen atoms, as an active atom, have strong affinity with metals through hydrogen bonds, van der Waals forces and other ways. Nitrogen-containing heterocycles are a kind of lubricating additive with good tribological properties. Using them as a nitrogen source can further improve the tribological properties of nitrogen-doped carbon quantum dots (N-CQDs) lubricating oil additives.

[0005] The existing preparation method of nitrogen-doped carbon quantum dots (N-CQDs) is complex, not easy to realize industrial production, has poor stability, is easy to agglomerate and precipitate, and affects the lubricating effect. SUMMARY

[0006] The purpose of the present application is to provide nitrogen-doped carbon quantum dots with nitrogen-containing heterocycle modification as well as a preparation method and application thereof, so as to solve the problems existing in the prior art.

[0007] One of the technical solutions provided by the present application is:

[0008] A preparation method of nitrogen heterocycle modified nitrogen-doped carbon quantum dots, the method comprises the following steps: dissolving a nitrogen-containing compound in an aldehyde compound, and reacting in an alkaline solution; purifying and drying to obtain nitrogen-doped carbon quantum dots; connecting the nitrogen-doped carbon quantum dots with SOCl2 and a fatty diamine to obtain fatty diamine modified nitrogen-doped carbon quantum dots; adding the fatty diamine modified nitrogen-doped carbon quantum dots into a nitrogen heterocycle acetyl chloride, and heating to react; purifying and drying the product to obtain the nitrogen heterocycle modified nitrogen-doped carbon quantum dots.

[0009] Preferably, the amount ratio of the nitrogen-containing compound to the aldehyde compound is (2-8) g:(40-45) mL.

[0010] Preferably, the nitrogen-containing compound is one or more of urea, benzotriazole acetic acid, benzimidazole acetic acid, tetrazole acetic acid and mercaptobenzothiazole acetic acid, and more preferably, the nitrogen-containing compound is urea.

[0011] Preferably, the aldehyde compound is acetaldehyde.

[0012] Preferably, the fatty diamine is one or more of ethylenediamine, propylenediamine and butylenediamine, and more preferably, the fatty diamine is ethylenediamine.

[0013] Preferably, the stirring time is 1-2 days.

[0014] Preferably, the solution purification method comprises filtering the reacted solution, and dialyzing the supernatant.

[0015] Preferably, the nitrogen heterocycle acetyl chloride is prepared from a nitrogen heterocycle derivative and SOCl2, and the nitrogen heterocycle derivative is one or more of benzotriazole acetic acid, benzimidazole acetic acid, tetrazole acetic acid and mercaptobenzothiazole acetic acid.

[0016] Preferably, the method for connecting the nitrogen-doped carbon quantum dots with SOCl2 and the fatty diamine comprises the following steps: mixing the obtained nitrogen-doped carbon quantum dots with SOCl2, heating to reflux at 80℃ for 1-3 hours, then adding the fatty diamine, reacting, removing the excess fatty diamine, washing with ethanol for multiple times, and drying for 18-26 hours to obtain the fatty diamine modified nitrogen-doped carbon quantum dots.

[0017] Preferably, the nitrogen heterocycle acetyl chloride is prepared from a nitrogen heterocycle acetic acid and SOCl2.

[0018] The second technical solution provided by the present application is as follows:

[0019] The nitrogen heterocycle modified nitrogen-doped carbon quantum dots prepared by the above preparation method, wherein the particle size of the nitrogen heterocycle modified nitrogen-doped carbon quantum dots is 1-50 nm, and preferably, the particle size is 2-20 nm.

[0020] The third technical solution of the present application provides:

[0021] The nitrogen-containing heterocyclic ring modified nitrogen-doped carbon quantum dots are applied to preparation of a composite lubricating liquid.

[0022] The fourth technical solution of the present application provides:

[0023] A preparation method of a composite lubricating liquid is provided, in which the nitrogen-containing heterocyclic ring modified nitrogen-doped carbon quantum dots are added into a glycol solution under a nitrogen atmosphere, an imidazoline compound is added under heating and stirring, and the stirring is stopped after the temperature is reduced to room temperature, so that the composite lubricating liquid is obtained.

[0024] Preferably, the mass ratio of the nitrogen-containing heterocyclic ring derivative modified carbon quantum dots and the imidazoline compound is (20-50):(15-20).

[0025] Preferably, the temperature of the heating and stirring is 50±2℃, and the time is 0.3-0.5h.

[0026] Preferably, the imidazoline compound is one or more of oleic acid imidazoline, stearic acid imidazoline, glutamic acid imidazoline, benzimidazole acetic acid imidazoline and benzotriazole acetic acid imidazoline.

[0027] Preferably, the base liquid is glycol or a mixture of glycol and deionized water.

[0028] In the present application, the carbon quantum dot nanoparticles are covalently bonded and surface-modified by nitrogen-containing heterocyclic rings with certain water solubility, which can increase the solubility and stability of the carbon quantum dots in the water-based medium, and the nitrogen-containing heterocyclic ring itself has certain corrosion inhibition performance and antioxidant performance, so that the surface modification of the carbon quantum dots can achieve active synergistic effect. Therefore, the low-cost organic reagent is selected as the precursor, the chemical method with simple operation is adopted to prepare the high-efficiency CDs, and the surface of the CDs is modified, so that the CDs have good corrosion inhibition synergistic effect when applied to the lubricating liquid.

[0029] In the present application, the composite lubricating liquid containing nitrogen-containing heterocyclic ring modified nitrogen-doped carbon quantum dots with different concentrations can be prepared according to the use requirements.

[0030] The present application has the following beneficial effects:

[0031] In the present application, the carbon quantum dot nanoparticles are surface-modified by nitrogen-containing heterocyclic rings, which can increase the solubility and stability of the carbon quantum dots in the water-based medium, so that the carbon quantum dots are fully dispersed in the lubricating liquid, and the mixing degree of the nanomaterials is increased.

[0032] The imidazoline corrosion inhibitor in the application is an organic compound, and the preparation process of the composite lubricating liquid is simple, the manufacturing cost is reduced, and industrialized production is easy to realize, so that the composite lubricating liquid is an environment-friendly composite lubricating liquid.

[0033] The composite lubricating liquid provided by the application has excellent tribological properties, corrosion resistance and thermal stability in an acid environment, and can be applied to many industries such as steel, chemical industry, petroleum, electric power, papermaking, oil refining, shipbuilding, storage and transportation. DETAILED DESCRIPTION

[0034] The various exemplary embodiments of the application will now be described in detail, which should not be considered as limiting the application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the application.

[0035] It should be understood that the terms described in the application are only for describing the specific embodiments, and are not used to limit the application. In addition, for the numerical range in the application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range and any other stated value or intermediate value in the stated range is also included in the application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application pertains. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the case of conflict, the content of the specification will control.

[0037] Many modifications and variations of the specific embodiments of the application described in the specification can be made without departing from the scope or spirit of the application, which will be apparent to those skilled in the art. Other embodiments resulting from the specification will be apparent to those skilled in the art. The specification and examples of the application are only exemplary.

[0038] As for the "comprising", "including", "having", "containing" and the like used herein, they are all open terms, that is, meaning containing but not limited to.

[0039] Example 1

[0040] S1. 5.6 g urea was dissolved in 45 mL acetaldehyde, then 16.0 g NaOH and 100 mL deionized water were added, stirred for 2 h, 2.5 mL hydrochloric acid (concentration 23%) was added dropwise to adjust the pH to neutral, continued to stir for 2 days until the solution system was uniform; the reacted solution was filtered, the supernatant was dialyzed, and the dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.9 g of a powdered sample as nitrogen-doped carbon quantum dots;

[0041] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 8.0 mL SOCl2, heated to reflux at 80°C for 2 h, then the remaining SOCl2 was removed by rotary evaporation, 6.7 mL ethylenediamine was added, and reacted at 100°C for 4 h. The obtained mixture was removed by rotary evaporation to remove excess ethylenediamine, washed with ethanol several times, and finally dried at 100°C for 24 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots;

[0042] S3. 1.2 g of benzotriazole acetic acid, 30 mL of toluene, and 5 mL of SOCl2 were mixed, heated to reflux at 80°C for 25 h, then the remaining SOCl2 was removed by rotary evaporation, the ethylenediamine-modified nitrogen-doped carbon quantum dots prepared in S2 were added, and reacted at 100°C for 4 h. The obtained mixture was removed by rotary evaporation to remove excess ethylenediamine, washed with ethanol several times, and finally dried at 100°C for 24 h to obtain 2.2 g of benzotriazole-modified nitrogen-doped carbon quantum dots with a particle size of 12 nm;

[0043] S4. Under N2, 2.2 g of benzotriazole-modified nitrogen-doped carbon quantum dots prepared in S3 were added to 10.0 mL of ethylene glycol solution, stirred at 50±2°C, and 1.2 g of imidazoline oleic acid was added. Keep stirring and heating for 0.5 h, stop stirring after cooling to room temperature, and obtain a composite lubricating liquid.

[0044] Example 2

[0045] S1. 5.6 g urea was dissolved in 45 mL acetaldehyde, then 16.0 g NaOH and 100 mL deionized water were added, stirred for 2 h, 2.5 mL hydrochloric acid (concentration 23%) was added dropwise to adjust the pH to neutral, continued to stir for 2 days until the solution system was uniform; the reacted solution was filtered, the supernatant was dialyzed, and the dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.9 g of a powdered sample as nitrogen-doped carbon quantum dots;

[0046] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 8.0 mL SOCl2, heated to reflux at 80 °C for 2.5 h, then the remaining SOCl2 was removed by rotary evaporation, 7.8 mL ethylenediamine was added, and the mixture was reacted at 100 °C for 4 h. The excess ethylenediamine was removed by rotary evaporation, and the mixture was washed with ethanol for several times. Finally, the mixture was dried at 100 °C for 18 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots.

[0047] S3. 1.0 g of benzotriazole acetic acid, 30 mL of toluene, and 5 mL of SOCl2 were mixed, heated to reflux at 80 °C for 2 h, then the excess SOCl2 was removed by rotary evaporation, and the ethylenediamine-modified nitrogen-doped carbon quantum dots prepared in S2 were added. The mixture was reacted at 100 °C for 4 h. The solvent was removed by rotary evaporation, and the mixture was washed with ethanol for several times. Finally, the mixture was dried at 100 °C for 24 h to obtain 1.7 g of benzotriazole-modified carbon quantum dots with a particle size of 10 nm.

[0048] S4. Under N2, 1.7 g of benzotriazole-modified nitrogen-doped carbon quantum dots prepared in S3 were added to 10.0 mL of ethylene glycol solution (100%), and 1.0 g of imidazoline oleic acid was added while stirring at 50±2 °C. The mixture was heated for 0.5 h, then the stirring was stopped after the temperature was lowered to room temperature to obtain a composite lubricating liquid.

[0049] Example 3

[0050] S1. 5.6 g of urea was dissolved in 45 mL of acetaldehyde, then 16.0 g of NaOH and 100 mL of deionized water were added and stirred for 2 h. 2.5 mL of hydrochloric acid (concentration 23%) was added to adjust the pH to 7, and the stirring was continued for 2 days until the solution system was uniform. The reaction solution was filtered, and the supernatant was dialyzed. The dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.9 g of a powdered sample of nitrogen-doped carbon quantum dots.

[0051] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 8.0 mL SOCl2, heated to reflux at 80 °C for 2 h, then the remaining SOCl2 was removed by rotary evaporation, 7.8 mL ethylenediamine was added, and the mixture was reacted at 100 °C for 4 h. The excess ethylenediamine was removed by rotary evaporation, and the mixture was washed with ethanol for several times. Finally, the mixture was dried at 100 °C for 18 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots.

[0052] S3. Mix 1.0 g of 2-(1-benzimidazole) acetic acid, 30 mL of toluene, 5 mL of SOCl2, heat to reflux at 80°C for 2 h, then remove excess SOCl2 by rotary evaporation, add the ethylenediamine modified nitrogen-doped carbon quantum dots prepared in S2, and react at 100°C for 4 h. Remove the solvent from the resulting mixture by rotary evaporation, wash with ethanol several times, and finally dry at 100°C for 24 h to obtain 1.6 g of benzimidazole-modified nitrogen-doped carbon quantum dots; the particle size is 6 nm;

[0053] S4. Under N2, add 1.6 g of benzimidazole-modified nitrogen-doped carbon quantum dots prepared in S3 to 10.0 mL of ethylene glycol solution, add 1.2 g of imidazoline oleic acid under stirring at 50±2°C for 0.5 h, stop stirring after cooling to room temperature, and obtain a composite lubricating liquid.

[0054] Example 4

[0055] S1. Dissolve 4.8 g of urea in 40 mL of acetaldehyde, then add 16.0 g of NaOH and 100 mL of deionized water and stir for 2 h, add 2.5 mL of hydrochloric acid (concentration 23%) dropwise to adjust the pH to neutral, continue stirring for 1.5 days until the solution system is uniform; filter the reaction solution, take the supernatant for dialysis, place the dialyzed solution in a freeze dryer, vacuumize, and freeze dry for 2 d to obtain 0.7 g of a powdered sample as nitrogen-doped carbon quantum dots;

[0056] S2. Mix the nitrogen-doped carbon quantum dots prepared in S1 and 7.5 mL of SOCl2, heat to reflux at 80°C for 2 h, then remove excess SOCl2 by rotary evaporation, add 6.6 mL of ethylenediamine, and react at 100°C for 4 h. Remove excess ethylenediamine from the resulting mixture by rotary evaporation, wash with ethanol several times, and finally dry at 100°C for 24 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots.

[0057] S3. Mix 1.0 g of 2-(1-benzimidazole) acetic acid, 30 mL of toluene, 5 mL of SOCl2, heat to reflux at 80°C for 25 h, then remove excess SOCl2 by rotary evaporation, add the ethylenediamine modified nitrogen-doped carbon quantum dots prepared in S2, and react at 100°C for 4 h. Remove excess ethylenediamine from the resulting mixture by rotary evaporation, wash with ethanol several times, and finally dry at 100°C for 24 h to obtain 1.5 g of benzimidazole-modified carbon quantum dots; the particle size is 10 nm.

[0058] S4. Under N2, add 1.5 g of benzimidazole-modified nitrogen-doped carbon quantum dots to 10.0 mL of ethylene glycol solution, add 1.2 g of imidazoline oleic acid under stirring at 50±2°C for 0.4 h, stop stirring after cooling to room temperature, and obtain a composite lubricating liquid.

[0059] Example 5

[0060] S1. 5.0 g urea was dissolved in 42 mL acetaldehyde, then 18.0 g KOH and 100 mL deionized water were added and stirred for 2 h, 2.3 mL hydrochloric acid (concentration 23%) was added dropwise to adjust the pH to neutral, and stirring was continued for 2 days until the solution system was uniform; the reacted solution was filtered, the supernatant was dialyzed, and the dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.6 g of a powdered sample as nitrogen-doped carbon quantum dots.

[0061] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 7.6 mL SOCl2, heated to reflux at 80°C for 2 h, then excess SOCl2 was removed by rotary evaporation, 7.0 mL ethylenediamine was added, and the mixture was reacted at 100°C for 4 h; the excess ethylenediamine was removed by a rotary evaporator, and the mixture was washed with ethanol several times; finally, it was dried at 100°C for 24 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots.

[0062] S3. 1.3 g mercaptobenzothiazole acetic acid, 30 mL toluene, and 5 mL SOCl2 were mixed, heated to reflux at 80°C for 24 h, then excess SOCl2 was removed by rotary evaporation, the ethylenediamine-modified nitrogen-doped carbon quantum dots prepared in S2 were added, and the mixture was reacted at 100°C for 4 h; the excess ethylenediamine was removed by a rotary evaporator, and the mixture was washed with ethanol several times; finally, it was dried at 100°C for 24 h to obtain 2.3 g of mercaptobenzothiazole-modified carbon quantum dots with a particle size of 6 nm.

[0063] S4. Under N2, 2.3 g of mercaptobenzothiazole-modified nitrogen-doped carbon quantum dots prepared in S3 were added to a mixture of 10.0 mL of ethylene glycol and water (1:1), stirred at 50±2°C, and 1.2 g of imidazoline oleic acid was added; heating and stirring were continued for 0.5 h, then the temperature was lowered to room temperature, and stirring was stopped to obtain a composite lubricating liquid.

[0064] Example 6

[0065] S1. 6.2 g urea was dissolved in 45 mL acetaldehyde, then 16.0 g NaOH and 100 mL deionized water were added and stirred for 2 h, 2.5 mL hydrochloric acid (concentration 23%) was added dropwise to adjust the pH to neutral, and stirring was continued for 1 day until the solution system was uniform; the reacted solution was filtered, the supernatant was dialyzed, and the dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.8 g of a powdered sample as nitrogen-doped carbon quantum dots.

[0066] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 8.3 mL SOCl2, heated to reflux at 80 °C for 2 h, then excess SOCl2 was removed by rotary evaporation, followed by the addition of 7.8 mL ethylenediamine, and reacted at 100 °C for 4 h. The resulting mixture was treated with rotary evaporation to remove excess ethylenediamine, washed with ethanol several times, and finally dried at 100 °C for 24 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots.

[0067] S3. 1.5 g of mercaptobenzothiazole acetic acid, 30 mL of toluene, and 5 mL of SOCl2 were mixed, heated to reflux at 80 °C for 25 h, then excess SOCl2 was removed by rotary evaporation, followed by the addition of the ethylenediamine-modified nitrogen-doped carbon quantum dots prepared in S2, and reacted at 100 °C for 4 h. The resulting mixture was treated with rotary evaporation to remove excess ethylenediamine, washed with ethanol several times, and finally dried at 100 °C for 24 h to obtain 2.8 g of mercaptobenzothiazole-modified carbon quantum dots with a particle size of 5 nm.

[0068] S4. Under N2, 10.0 mL of a mixture of ethylene glycol and water (1:1) was added to the 2.8 g of mercaptobenzothiazole-modified nitrogen-doped carbon quantum dots prepared in S3, stirred at 50±2 °C, and 1.2 g of imidazoline oleate was added. The stirring and heating were continued for 0.4 h, and then the stirring was stopped after the temperature was lowered to room temperature to obtain a composite lubricating liquid.

[0069] Example 7

[0070] S1. 6.2 g of urea was dissolved in 45 mL of acetaldehyde, then 16.0 g of NaOH and 100 mL of deionized water were added and stirred for 2 hours. 2.5 mL of hydrochloric acid (concentration 23%) was added to adjust the pH to neutral, and the stirring was continued for 2 days until the solution system was uniform. The reacted solution was filtered, and the supernatant was dialyzed. The dialyzed solution was placed in a freeze dryer, vacuumed, and freeze-dried for 2 d to obtain 0.7 g of a powder sample as nitrogen-doped carbon quantum dots.

[0071] S2. The nitrogen-doped carbon quantum dots prepared in S1 were mixed with 8.3 mL SOCl2, heated to reflux at 80 °C for 2 h, then excess SOCl2 was removed by rotary evaporation, followed by the addition of 7.8 mL ethylenediamine, and reacted at 100 °C for 4 h. The resulting mixture was treated with rotary evaporation to remove excess ethylenediamine, washed with ethanol several times, and finally dried at 100 °C for 24 h to obtain ethylenediamine-modified nitrogen-doped carbon quantum dots;

[0072] S3. 1.8 g tetrazole acetic acid, 30 mL toluene, 5 mL SOCl2 were mixed, heated to reflux at 80 °C for 25 h, then rotary evaporated to remove excess SOCl2, and then added the ethylenediamine modified nitrogen-doped carbon quantum dots prepared in S2, reacted at 100 °C for 4 h, the excess ethylenediamine was removed by a rotary evaporator, and the mixture was washed with ethanol for several times, and finally dried at 100 °C for 24 h to obtain 2.6 g tetrazole modified nitrogen-doped carbon quantum dots with a particle size of 6 nm;

[0073] S4. Under the condition of N2, 2.6 g tetrazole modified nitrogen-doped carbon quantum dots prepared in S3 were added into 10.0 mL ethylene glycol solution, stirred at 50±2 °C, and then 1.2 g oleic acid imidazoline was added, heated and stirred for 0.5 h, cooled to room temperature, and then the stirring was stopped to obtain a composite lubricating liquid.

[0074] Example 8

[0075] S1. 5.6 g urea was dissolved in 45 mL acetaldehyde, then 16.0 g NaOH and 100 mL deionized water were added and stirred for 2 h, 2.5 mL hydrochloric acid (concentration 23%) was added dropwise to adjust the pH to neutral, and the stirring was continued for 1 day until the solution system was uniform; the reacted solution was filtered, the supernatant was dialyzed, the dialyzed solution was placed in a freeze dryer, vacuumized, and freeze-dried for 2 d to obtain 0.7 g of a powder sample as nitrogen-doped carbon quantum dots.

[0076] S2. The nitrogen-doped carbon quantum dots prepared in S1 and 8.0 mL SOCl2 were mixed, heated to reflux at 80 °C for 2 h, then rotary evaporated to remove excess SOCl2, and then 7.2 mL ethylenediamine was added, reacted at 100 °C for 4 h, the excess ethylenediamine was removed by a rotary evaporator, and the mixture was washed with ethanol for several times, and finally dried at 100 °C for 24 h to obtain ethylenediamine modified nitrogen-doped carbon quantum dots.

[0077] S3. 2.2 g tetrazole acetic acid, 30 mL toluene, 5 mL SOCl2 were mixed, heated to reflux at 80 °C for 25 h, then rotary evaporated to remove excess SOCl2, and then added the ethylenediamine modified nitrogen-doped carbon quantum dots prepared in S2, reacted at 100 °C for 4 h, the solvent was removed by a rotary evaporator, and the mixture was washed with ethanol for several times, and finally dried at 100 °C for 24 h to obtain 2.4 g tetrazole modified nitrogen-doped carbon quantum dots with a particle size of 11 nm;

[0078] S4. Under the condition of N2, 2.4 g tetrazole modified nitrogen-doped carbon quantum dots prepared in S3 were added into 10.0 mL ethylene glycol solution, stirred at 50±2 °C, and then 1.2 g oleic acid imidazoline was added, heated and stirred for 0.4 h, cooled to room temperature, and then the stirring was stopped to obtain a composite lubricating liquid.

[0079] Performance test analysis

[0080] 1. Tribological property testing and analysis of composite lubricants

[0081] The frictional properties of the composite lubricants prepared in Examples 1-8 were evaluated using the MMW-1B vertical universal abrasion tester manufactured by Jinan Shunmao Test Instrument Co., Ltd.

[0082] During testing, a 10mm diameter steel ball (GCr15 bearing steel, HRC 64-66 hardness) was used, along with the composite lubricant prepared in the above examples. The test was conducted under point contact pressure using sliding friction. Dynamic friction data generated during the friction process was automatically recorded by the instrument and transmitted to a computer to generate friction curves. The wear scar diameter was measured using an Oswell M203 metallographic microscope. The average friction coefficient and average wear scar (WSD) diameter were the average values ​​of three friction tests. Table 1 shows the tribological test results of the composite lubricants prepared in Examples 1-8. It should be noted that in this embodiment of the invention, ethylene glycol or ethylene glycol + water was used as the lubricant base. Nitrogen-doped carbon quantum dots modified with nitrogen heterocycles and oleic acid imidazoline prepared in Examples 1-8 were added under stirring to obtain a composite lubricant. After mixing, the mixture was ultrasonically treated for 30 minutes to obtain a stable composite lubricant.

[0083] Table 1 Tribological properties of lubricants

[0084]

[0085] As can be seen from Table 1, the composite lubricants prepared by this invention all have good anti-wear and friction-reducing properties.

[0086] 2. Corrosion Inhibition Performance Test and Analysis of Composite Lubricants

[0087] The composite lubricants prepared in Examples 1, 4 and 8 were added to hydrochloric acid solution to obtain corrosion inhibitors of nitrogen-doped carbon quantum dots with different contents of nitrogen heterocyclic modification for use in a 1.0M HCl acidic environment.

[0088] Electrochemical measurements of the corrosion inhibitor in the above examples on Q235 carbon steel in 1.0M HCl solution at room temperature were recorded using a CHI-660E electrochemical workstation. The electrolyte volume was 80 mL, the auxiliary electrode was a platinum plate, the reference electrode was Hg / HgCl2, and the working electrode was Q235 steel with an exposure area of ​​1 cm². 2After the open circuit potential was stabilized for 30 min, the electrochemical impedance spectroscopy (EIS) was analyzed in the frequency range of 10-2 Hz to 105 Hz and the amplitude range of 5 mV. The EIS data were fitted and analyzed by ZView software. Then, the polarization curves were obtained in the range of -250 mV to +250 mV relative to OCP at a scan rate of 5 mV / s. The experiments were repeated three times under each condition.

[0089] The above-mentioned corrosion inhibitor solution was subjected to electrochemical test analysis, and Table 2 shows the electrochemical test results of the above-mentioned corrosion inhibitor solution on Q235 steel in 1.0 M HCl solution.

[0090] Table 2 Electrochemical test of the corrosion inhibitor solution

[0091] Composition Inhibition rate / % derived from fitted parameters 1 50 mg / L Example 1 76.32 2 100 mg / L Example 1 87.95 3 200 mg / L Example 1 91.65 4 100 mg / L Example 4 88.38 5 200 mg / L Example 4 94.26 6 50 mg / L Example 8 73.81 7 100 mg / L Example 8 86.33 8 200 mg / L Example 8 91.56

[0092] As can be seen from Table 2, the composite lubricating liquid based on the prepared nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots has good corrosion inhibition effect in an acidic solution. When the mass fraction of the contained lubricating liquid is in the range of 50-200 mg / L, the corrosion inhibition performance of the obtained composite lubricating liquid increases with the increase of the concentration, and the corrosion inhibition ability is obviously improved.

[0093] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preparing a complex lubricating fluid, characterized by, The nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots are added into a base solution under a nitrogen atmosphere, and an imidazoline compound is added under heating and stirring, and stirring is stopped after the solution is cooled to room temperature, to obtain the composite lubricating liquid. The preparation method of the nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots comprises the following steps: a nitrogen-containing compound is dissolved in an aldehyde compound, and is reacted in an alkaline solution; the nitrogen-doped carbon quantum dots are purified and dried to obtain the nitrogen-doped carbon quantum dots; the nitrogen-doped carbon quantum dots are connected with SOCl2 and a fatty diamine to obtain fatty diamine modified nitrogen-doped carbon quantum dots; the fatty diamine modified nitrogen-doped carbon quantum dots are added into a nitrogen-containing heterocyclic acyl chloride, and are heated and reacted, and the product is purified and dried to obtain the nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots.

2. The production method according to claim 1, characterized by, The use amount ratio of the nitrogen-containing compound and the aldehyde compound is (2-8) g:(40-45) mL.

3. The production method according to claim 1, characterized by, The mass ratio of the nitrogen-containing heterocyclic modified nitrogen-doped carbon quantum dots and the imidazoline compound is (1.25-2.33):

1.

4. The production method according to claim 1, characterized by, The temperature of the heating and stirring is 50±2℃, and the time is 0.3-0.5 h.

5. The preparation method according to claim 1, characterized in that, The imidazoline compound is one or more of oleic acid imidazoline, stearic acid imidazoline, glutamic acid imidazoline, benzimidazole acetic acid imidazoline and benzotriazole acetic acid imidazoline.

Images