Diesel additive and preparation method thereof

Abstract

The invention discloses a diesel additive and a preparation method thereof. The diesel oil additive comprises the following raw material components in percentage by mass: 1-5% of a function improver, 0.5-1% of an antioxidant, 0.1-0.3% of a dispersing agent and the balance of base oil. The invention also provides a preparation method of the diesel oil additive, and the diesel oil additive is prepared by mixing the raw material components. Compared with the prior art, the prepared diesel oil additive has the advantages of being good in anti-wear lubrication and low-temperature fluidity, small in additive amount, wide in adaptability, high in stability and the like, and the preparation method is easy and convenient to operate, low in cost and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of diesel additives, and particularly to a diesel additive and a preparation method thereof. Background Art

[0002] The prior art uses a deep processing and refining process to produce low-sulfur diesel with a sulfur content of less than 500 mg / kg, and begins to promote its use. Due to the use of a relatively harsh hydrogenation process, many natural components in diesel with anti-wear functions, such as nitrogen-containing, oxygen-containing compounds and polycyclic aromatic hydrocarbons, are also removed, resulting in a significant reduction in the lubricity of diesel, causing wear of some components that rely on diesel itself for lubrication, such as rotary pumps and distributor pumps, and reducing their service life.

[0003] The prior art usually adds a diesel anti-wear agent additive to low-sulfur diesel, which can adsorb on the metal surface, form a protective film on the metal surface, reduce the friction between metals, effectively improve the lubricity of low-sulfur diesel, and has the advantages of low cost, flexible production, and less pollution. The enterprise standards for diesel anti-wear agent technology formulated by Sinopec mainly include two categories: unsaturated fatty acids and their unsaturated fatty acid esters.

[0004] However, fatty acid-based anti-wear additives have many defects in application. Firstly, a large addition amount is required to meet the technical requirement of reducing the wear scar diameter of low-sulfur diesel to less than 420 μm. Secondly, there are problems affecting the cold filter plugging point and low-temperature storage stability of diesel, and poor compatibility with diesel or other additives. Although it will be found during use that the pour point of fatty acid ester diesel anti-wear agents is very low, their fluidity at low temperatures is very poor, and the pump body cannot transport them to the diesel tank for blending. Especially in cold northern regions, the transportation difficulty is even greater, and it must be heated to a certain temperature before it can be used, which is a waste of time and energy. Therefore, a diesel additive with excellent anti-wear lubrication and good low-temperature fluidity is needed.

[0005] CN117384702A discloses a production process and application of a diesel anti-wear lubricant. The diesel anti-wear lubricant provided by the invention contains the following raw materials in mass percentages: 4-8% of a modified additive, 2-3% of modified wear-resistant particles, 0.5-1% of alkyl diphenylamine, 1-1.5% of benzotriazole derivatives, and 0.1-0.3% of polyisobutylene succinimide, with the balance being base oil; the diesel anti-wear lubricant is prepared by uniformly mixing the raw materials. The diesel anti-wear lubricant provided by the invention has a good anti-wear lubrication effect. However, the low-temperature fluidity of this diesel anti-wear lubricant is poor, which may cause dry friction between the engine piston and the piston wall during low-temperature cold start of the engine because the diesel cannot be pumped to the engine lubrication part in time to play a lubricating role, resulting in wear of the engine and shortening the service life of the engine.

[0006] CN104789284A discloses a multifunctional low-sulfur diesel antiwear agent and its application. The multifunctional low-sulfur diesel antiwear agent comprises the following components in mass percentage: a) 85 - 94.5% of fatty acid, b) 5 - 10% of dimer acid, c) 0.5 - 5% of ethylene-styrene-vinyl acetate-maleate copolymer; the diesel antiwear agent provided by this invention is non-toxic, free of heavy metals, has a small addition amount and is convenient to use. It can significantly improve the lubricity of low-sulfur diesel, and at the same time can greatly improve the low-temperature fluidity of diesel. However, when this diesel antiwear agent is stored for a long time, components such as fatty acid and dimer acid contained therein may react with oxygen and moisture in the air, deteriorate, affecting its antiwear and low-temperature fluidity improvement effects, and may also produce corrosive substances, causing damage to the storage container. Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the present invention provides a diesel additive and its preparation method. The provided diesel additive has good antiwear lubrication and low-temperature fluidity, and has the advantages of small dosage, wide adaptability, and strong stability. The preparation method provided by the present invention is simple to operate, low in cost, and suitable for large-scale production.

[0008] To achieve the above object, the present invention provides a preparation method of a diesel additive, comprising the following steps:

[0009] Weigh each raw material: functional improver, antioxidant, dispersant and base oil respectively, and then mix the raw materials, and ultrasonically mix for 3 - 6 min under the conditions of ultrasonic frequency of 30 - 50 KHz and ultrasonic power of 50 - 100 W until evenly mixed to obtain the diesel additive.

[0010] Preferably, the raw material component ratio includes, by mass percentage:

[0011] 1 - 5% of functional improver, 0.5 - 1% of antioxidant and 0.1 - 0.3% of dispersant, and the balance is base oil.

[0012] Preferably, the functional improver is composed of composite modified graphene oxide and nano-copper oxide mixed in a mass ratio of 2 - 3:1; the composite modified graphene oxide is graphene oxide modified by polyethylene glycol fatty acid ester and imidazole ionic liquid.

[0013] Preferably, the preparation method of the composite modified graphene oxide comprises the following steps, by weight:

[0014] S1. Add 0.5 - 1.5 parts of graphene oxide into 10 - 20 parts of N,N - dimethylformamide, then add 40 - 60 parts of thionyl chloride. Under nitrogen protection, heat and reflux at 85 - 95 °C for 10 - 13 h to obtain a mixed reactant; distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran and dry in vacuum to obtain acid - chlorinated graphene oxide;

[0015] S2. Add 0.1 - 0.3 parts of the acid - chlorinated graphene oxide prepared in S1 above into a mixed solvent composed of 8 - 15 parts of N,N - dimethylformamide and 10 - 20 parts of toluene, then sequentially add 2 - 6 parts of polyethylene glycol fatty acid ester and 1.5 - 2.5 parts of triethylamine, and then stir at 75 - 85 °C for 10 - 13 h under nitrogen protection; after the reaction is completed, wash with ethanol and dry at 40 - 50 °C to obtain modified graphene oxide;

[0016] S3. Add 0.4 - 0.6 parts of the modified graphene oxide obtained above into 200 - 300 parts of absolute ethanol, and ultrasonically disperse for 2 - 5 min under the conditions of ultrasonic frequency of 30 - 50 KHz and ultrasonic power of 50 - 100 W to obtain a mixed solution; then add 0.4 - 0.6 parts of imidazolium ionic liquid into the above - mentioned mixed solution under a nitrogen atmosphere at 45 - 60 °C, and then heat and reflux for 4 - 6 h; filter, wash with absolute ethanol 2 - 3 times and then dry in vacuum at 50 - 60 °C to obtain composite - modified graphene oxide.

[0017] Preferably, the preparation method of the polyethylene glycol fatty acid ester comprises the following steps, by weight:

[0018] Mix 1.2 - 1.5 parts of fatty acid compound and 0.9 - 1.1 parts of polyethylene glycol in 20 - 30 parts of xylene, then add 0.05 - 0.08 parts of p - toluenesulfonic acid as a catalyst, and heat and reflux at 200 - 400 rpm and 115 - 125 °C for 20 - 25 h; after the reaction is completed, cool the reaction mixture to room temperature, extract the product with ethyl acetate 2 - 3 times, then extract with saturated sodium chloride aqueous solution 2 - 3 times, and then extract the organic phase with deionized water 3 - 4 times, and collect the organic phase; add anhydrous sodium sulfate into the organic phase, stir and filter, and collect the filtrate; evaporate the solvent of the filtrate at 50 - 60 °C using a rotary evaporator until the solvent is completely removed to obtain polyethylene glycol fatty acid ester.

[0019] Further preferably, the fatty acid compound is selected from one of γ - linolenic acid, linoleic acid, oleic acid, stearic acid, and palmitic acid.

[0020] In the preparation process of the above polyethylene glycol fatty acid ester, polyethylene glycol reacts with a fatty acid compound, and an esterification reaction occurs under the catalysis of p-toluenesulfonic acid to obtain the polyethylene glycol fatty acid ester.

[0021] Preferably, the preparation method of the imidazolium ionic liquid in the step S3 includes the following steps, by weight:

[0022] Mix 5-6 parts of 3-chloromethoxypropylsilane and 1.5-2.2 parts of imidazole at 105-115 °C, and mix and stir the reaction under a nitrogen atmosphere at 300-500 rpm for 20-25 h; then wash the reaction product with ethyl acetate to obtain the imidazolium ionic liquid.

[0023] In the preparation process of the above ionic liquid, the chlorine atom in 3-chloromethoxypropylsilane has strong activity, and the nitrogen atom in the imidazole molecule contains a lone pair of electrons and has nucleophilicity. During the reaction, the nitrogen atom in the imidazole molecule attacks the chlorine atom in 3-chloromethoxypropylsilane, and a nucleophilic substitution reaction occurs to prepare the ionic liquid.

[0024] Preferably, the base oil is selected from one or more of API Group I, II, III, IV, and V base oils.

[0025] More preferably, the base oil is selected from Group II base oil; the base oil is composed of a Group II 250N base oil and a Group II 150N base oil mixed in a mass ratio of 1-3:1.

[0026] Preferably, the antioxidant is selected from at least one of methyl epoxy oleate, 2,6-di-tert-butyl-p-cresol, and 2,6-di-tert-butylphenol;

[0027] Preferably, the dispersant is selected from at least one of tributyl phosphate, 3-(2-mercapto-benzothiazolyl)-2-ethoxypropanol, and polyisobutylene succinimide.

[0028] Graphene oxide has been widely used in tribological materials due to its two-dimensional and layered structure. However, due to the abundant hydroxyl and carboxyl groups on its surface, graphene oxide nanosheets are inherently hydrophilic, resulting in poor dispersibility in base oil and easy agglomeration, which limits its application. Therefore, surface modification must be carried out to increase its compatibility with base oil. In the preparation process of the composite modified graphene oxide of the present invention, graphene oxide is mixed and reacted with thionyl chloride. During the reaction process, the carboxyl groups in graphene oxide are converted into acyl chloride groups under the action of thionyl chloride, providing active intermediates for subsequent esterification reactions. Then, the acyl chlorinated graphene oxide reacts with polyethylene glycol fatty acid ester under the catalysis of triethylamine. During the reaction process, the acyl chloride groups carried by the acyl chlorinated graphene oxide form ester bonds with the hydroxyl groups in the structure of polyethylene glycol fatty acid ester, and polyethylene glycol fatty acid ester is successfully grafted onto the surface of graphene oxide to obtain modified graphene oxide. In the subsequent reaction process, the modified graphene oxide is mixed and reacted with imidazolium ionic liquid. The silane oxy groups (-OR) in the ionic liquid can undergo a silanization reaction with the hydroxyl groups on the surface of the modified graphene oxide under certain conditions. The silane oxy groups hydrolyze to form silanol groups (-SiOH), and the silanol groups dehydrate and condense with the hydroxyl groups on the surface of the modified graphene oxide to form stable Si-O-C bonds, thereby grafting the imidazolium ionic liquid onto the surface of the modified graphene oxide to obtain composite modified graphene oxide.

[0029] The inventors of the present invention found that the prepared composite modified graphene oxide has good dispersibility and compatibility in base oil. The introduction of the polyethylene glycol chain segment and fatty acid chain segment in the structure of polyethylene glycol fatty acid ester on the surface of the composite modified graphene oxide and the grafted imidazolium ionic liquid can significantly improve the dispersibility of graphene oxide in base oil, avoiding the problem of uneven dispersion caused by agglomeration of graphene in traditional additives, and making it have good stability in diesel. And the composite modified graphene oxide exhibits excellent anti-wear and friction-reducing properties. It can form a lubricating film between the contact surfaces, reducing the direct contact between metal surfaces, significantly reducing the wear diameter and friction coefficient, thereby reducing wear and friction. At the same time, it can also prevent the oxidation of the worn surface and prevent the generation of corrosive wear products. In addition, the inventors of the present invention also found that when the prepared composite modified graphene oxide and nano-copper oxide are used synergistically as functional improvers and introduced into the preparation process of diesel additives, it is beneficial to further improve the anti-wear and lubricating properties of diesel additives, and at the same time helps to improve the storage stability of diesel additives.

[0030] The present invention also provides a diesel additive prepared by the above method.

[0031] The beneficial effects of the present invention:

[0032] 1. Compared with the prior art, through reasonable proportioning and optimized preparation process conditions, the present invention prepares a diesel additive with excellent anti-wear and lubricating properties, while endowing the diesel additive with excellent low-temperature performance and stability. The diesel additive provided by the present invention solves the problem of large wear during the operation of diesel engines and extends the service life of fuel pumps. At the same time, it can ensure that the diesel engine can be normally started at a lower temperature, can be applied to the diesel oil of large vehicles in low-temperature environments, improves the low-temperature flow effect, alleviates the problem of low-temperature cold start of vehicles, and is beneficial to reducing fuel consumption and increasing the fuel-saving rate.

[0033] 2. Compared with the prior art, the present invention uses polyethylene glycol and fatty acids to prepare polyethylene glycol fatty acid ester, and introduces it into the preparation process of modified graphene oxide to modify graphene oxide, obtaining modified graphene oxide. Then, an imidazole ionic liquid is introduced for reaction, and it is grafted onto the surface of the modified graphene oxide to obtain composite modified graphene oxide. The obtained composite modified graphene oxide has excellent anti-wear and lubricating effects. At the same time, it is used in combination with nano-copper oxide as a functional improver and introduced into the preparation process of the diesel additive, which not only improves the anti-wear and lubricating effect of the diesel additive, but also improves the high-temperature kinematic viscosity and viscosity index, and at the same time improves the low-temperature fluidity. Specific Embodiments

[0034] Parameters and sources of specific chemical substances used.

[0035] Graphene oxide, particle size D50: 40μm, model: HM-2031, sourced from Xuzhou Huimo New Material Technology Co., Ltd.;

[0036] Polyethylene glycol, molecular weight: 4000;

[0037] Nano-copper oxide, particle size: 40nm, model: AM-CuO-023-1, sourced from Zhejiang Yamei Nano Technology Co., Ltd.;

[0038] Polyisobutylene succinimide, product number: A00294, sourced from Wuhan Jiyesheng Chemical Co., Ltd.;

[0039] Type II 250N base oil, pour point ≤ -20°C, viscosity index: 100, sourced from Suzhou Saipahan Special Oil Products Co., Ltd.;

[0040] Type II 150N base oil, pour point ≤ -20°C, viscosity index: 100, sourced from Suzhou Saipahan Special Oil Products Co., Ltd.

[0041] Example 1

[0042] A preparation method of a diesel additive specifically includes the following steps:

[0043] Weigh the following raw materials by mass percentage: 3.5% of functional improver, 0.8% of 2,6-di-tert-butyl-p-cresol, and 0.2% of polyisobutylene succinimide, with the balance being base oil. Mix the raw materials and ultrasonically mix them for 5 minutes until evenly mixed under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 w to obtain a diesel additive.

[0044] The base oil is composed of a mixture of type II 250N base oil and type II 150N base oil in a mass ratio of 2:1.

[0045] The functional improver is composed of a mixture of composite modified graphene oxide and nano-copper oxide in a mass ratio of 3:1. <M

[0046] The preparation method of the composite modified graphene oxide includes the following steps:

[0047] S1. Add 1 part by weight of graphene oxide to 15 parts by weight of N,N-dimethylformamide, then add 45 parts by weight of thionyl chloride, and under nitrogen protection, heat and reflux at 90 °C for 12 h to obtain a mixed reactant; distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran, and dry in vacuum to obtain acyl chloride-modified graphene oxide;

[0048] S2. Add 0.2 part by weight of the acyl chloride-modified graphene oxide prepared in S1 above to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene, then sequentially add 5 parts by weight of polyethylene glycol fatty acid ester and 2 parts by weight of triethylamine, and then stir at 80 °C for 12 h under nitrogen protection; after the reaction is completed, wash with ethanol and dry at 40 °C to obtain modified graphene oxide;

[0049] S3. Add 0.5 part by weight of the modified graphene oxide obtained above to 260 parts by weight of absolute ethanol, ultrasonically disperse it for 3 minutes under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution; then add 0.5 part by weight of imidazolium ionic liquid to the above mixed solution at 50 °C under a nitrogen atmosphere, and then heat and reflux for 5 h; filter, wash with absolute ethanol 3 times, and dry in vacuum at 55 °C to obtain composite modified graphene oxide.

[0050] The preparation method of the polyethylene glycol fatty acid ester in step S2 includes the following steps:

[0051] 1.4 parts by weight of γ-linolenic acid and 1 part by weight of polyethylene glycol were added to 20 parts by weight of xylene and mixed. Then, 0.07 part by weight of p-toluenesulfonic acid with a volume percentage of 2.5% was added as a catalyst, and the mixture was heated under reflux at 250 rpm and 120 °C for 24 h. After the reaction was completed, the reaction mixture was cooled to room temperature, and the product was extracted 3 times with ethyl acetate, then extracted 3 times with saturated sodium chloride aqueous solution, and then the organic phase was extracted 3 times with deionized water. The organic phase was collected. Anhydrous sodium sulfate was added to the organic phase, stirred and filtered, and the filtrate was collected. The solvent in the filtrate was evaporated using a rotary evaporator at 55 °C until the solvent was completely removed, and polyethylene glycol fatty acid ester was obtained.

[0052] The preparation method of the imidazolium ionic liquid in the step S3 includes the following steps:

[0053] 5.4 parts by weight of 3-chloromethoxypropylsilane and 2 parts by weight of imidazole were mixed at 110 °C and mixed and stirred at 400 rpm under a nitrogen atmosphere for 22 h. Then the reaction product was washed with ethyl acetate to obtain the imidazolium ionic liquid.

[0054] Example 2

[0055] A preparation method of a diesel additive, which is different from that of Example 1 in that the preparation method of the composite modified graphene oxide includes the following steps:

[0056] S1. 1 part by weight of graphene oxide was added to 15 parts by weight of N,N-dimethylformamide, and then 45 parts by weight of thionyl chloride was added. Under nitrogen protection, the mixture was heated under reflux at 90 °C for 12 h to obtain a mixed reactant. The excess thionyl chloride in the mixed reactant was removed by distillation, and then it was washed with tetrahydrofuran and dried in vacuo to obtain acyl chlorinated graphene oxide;

[0057] S2. 0.2 part by weight of the acyl chlorinated graphene oxide prepared in the above S1 was added to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene. Then, 5 parts by weight of polyethylene glycol fatty acid ester and 2 parts by weight of triethylamine were added in sequence, and then under nitrogen protection, the mixture was stirred at 80 °C for 12 h. After the reaction was completed, it was washed with ethanol and dried at 40 °C to obtain modified graphene oxide;

[0058] S3. 0.5 part by weight of the modified graphene oxide obtained above was added to 260 parts by weight of absolute ethanol, and ultrasonically dispersed for 3 min under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution. Then, under a nitrogen atmosphere at 50 °C, 0.5 part by weight of the imidazolium ionic liquid was added to the above mixed solution, and then heated under reflux for 5 h. Filtered, washed 3 times with absolute ethanol and dried in vacuo at 55 °C to obtain the composite modified graphene oxide.

[0059] The preparation method of polyethylene glycol fatty acid ester in step S2 includes the following steps:

[0060] Mix 1.4 parts by weight of linoleic acid and 1 part by weight of polyethylene glycol in 20 parts by weight of xylene, then add 0.07 part by weight of p-toluenesulfonic acid with a volume percentage of 2.5% as a catalyst, and heat under reflux at 250 rpm and 120 °C for 24 h; after the reaction is completed, cool the reaction mixture to room temperature, extract the product 3 times with ethyl acetate, then extract 3 times with saturated sodium chloride aqueous solution, and then extract the organic phase 3 times with deionized water, and collect the organic phase; add anhydrous sodium sulfate to the organic phase, stir and filter, and collect the filtrate; evaporate the solvent in the filtrate at 55 °C using a rotary evaporator until the solvent is completely removed to obtain polyethylene glycol fatty acid ester.

[0061] The preparation method of the imidazole ionic liquid in step S3 is the same as that in Example 1.

[0062] Example 3

[0063] A preparation method of a diesel additive, which is different from that in Example 1 in that the preparation method of the composite modified graphene oxide includes the following steps:

[0064] S1. Add 1 part by weight of graphene oxide to 15 parts by weight of N,N-dimethylformamide, then add 45 parts by weight of thionyl chloride, and heat under reflux at 90 °C for 12 h under nitrogen protection to obtain a mixed reactant; distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran, and dry under vacuum to obtain acyl chloride graphene oxide;

[0065] S2. Add 0.2 part by weight of the acyl chloride graphene oxide prepared in S1 above to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene, then sequentially add 5 parts by weight of polyethylene glycol fatty acid ester and 2 parts by weight of triethylamine, and then stir at 80 °C for 12 h under nitrogen protection; after the reaction is completed, wash with ethanol and dry at 40 °C to obtain modified graphene oxide;

[0066] S3. Add 0.5 part by weight of the modified graphene oxide obtained above to 260 parts by weight of absolute ethanol, and ultrasonically disperse for 3 min under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution; then add 0.5 part by weight of imidazole ionic liquid to the above mixed solution at 50 °C under a nitrogen atmosphere, and then heat under reflux for 5 h; filter, wash 3 times with absolute ethanol, and dry under vacuum at 55 °C to obtain composite modified graphene oxide.

[0067] The preparation method of polyethylene glycol fatty acid ester in step S2 includes the following steps:

[0068] 1.4 parts by weight of oleic acid and 1 part by weight of polyethylene glycol were added to 20 parts by weight of xylene and mixed, and then 0.07 parts by weight of 2.5% by volume of p-toluenesulfonic acid was added as a catalyst, and the mixture was heated under reflux at 250 rpm and 120° C. for 24 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, and the product was extracted three times with ethyl acetate, then extracted three times with a saturated sodium chloride aqueous solution, and then the organic phase was extracted three times with deionized water, and the organic phase was collected. Anhydrous sodium sulfate was added to the organic phase, stirred and filtered, and the filtrate was collected. The solvent of the filtrate was evaporated at 55° C. using a rotary evaporator until the solvent was completely removed to obtain polyethylene glycol fatty acid ester.

[0069] The preparation method of the imidazolium ionic liquid in step S3 is consistent with that in Example 1.

[0070] Example 4

[0071] A method for preparing a diesel additive, which differs from Example 1 in that the method for preparing the composite modified graphene oxide comprises the following steps:

[0072] S1. Add 1 part by weight of graphene oxide to 15 parts by weight of N,N-dimethylformamide, then add 45 parts by weight of thionyl chloride, and heat under reflux at 90°C for 12 hours under nitrogen protection to obtain a mixed reactant; remove excess thionyl chloride from the mixed reactant by distillation, then wash with tetrahydrofuran, and vacuum dry to obtain chlorinated graphene oxide;

[0073] S2, adding 0.2 weight parts of the chlorinated graphene oxide prepared in S1 above to a mixed solvent consisting of 10 weight parts of N,N-dimethylformamide and 15 weight parts of toluene, and then sequentially adding 5 weight parts of polyethylene glycol fatty acid ester and 2 weight parts of triethylamine, and then stirring at 80 ° C for 12 hours under nitrogen protection; after the reaction is completed, washing with ethanol and drying at 40 ° C to obtain modified graphene oxide;

[0074] S3. Add 0.5 parts by weight of the modified graphene oxide obtained above to 260 parts by weight of anhydrous ethanol, and ultrasonically disperse for 3 minutes at an ultrasonic frequency of 40 kHz and an ultrasonic power of 50 W to obtain a mixed solution; then, under a nitrogen atmosphere, 0.5 parts by weight of an imidazole ionic liquid is added to the above mixed solution at 50° C., and then heated to reflux for 5 hours; filter, wash with anhydrous ethanol three times, and then dry in a vacuum at 55° C. to obtain a composite modified graphene oxide.

[0075] The preparation method of the polyethylene glycol fatty acid ester in step S2 comprises the following steps:

[0076] 1.4 parts by weight of stearic acid and 1 part by weight of polyethylene glycol were added to 20 parts by weight of xylene and mixed, then 0.07 part by weight of p-toluenesulfonic acid with a volume percentage of 2.5% was added as a catalyst, and the mixture was heated under reflux at 250 rpm and 120 °C for 24 h; after the reaction was completed, the reaction mixture was cooled to room temperature, and the product was extracted 3 times with ethyl acetate, then extracted 3 times with saturated sodium chloride aqueous solution, and then the organic phase was extracted 3 times with deionized water, and the organic phase was collected; anhydrous sodium sulfate was added to the organic phase, stirred and filtered, and the filtrate was collected; the solvent in the filtrate was evaporated using a rotary evaporator at 55 °C until the solvent was completely removed to obtain polyethylene glycol fatty acid ester.

[0077] The preparation method of the imidazolium ionic liquid in step S3 is the same as that in Example 1.

[0078] Example 5

[0079] A preparation method of a diesel additive, which is different from that in Example 1 in that the preparation method of the composite modified graphene oxide includes the following steps:

[0080] S1. 1 part by weight of graphene oxide was added to 15 parts by weight of N,N-dimethylformamide, then 45 parts by weight of thionyl chloride was added, and under nitrogen protection, the mixture was heated under reflux at 90 °C for 12 h to obtain a mixed reactant; the excess thionyl chloride was removed from the mixed reactant by distillation, then washed with tetrahydrofuran, and dried in vacuo to obtain acyl chlorinated graphene oxide.

[0081] S2. 0.2 part by weight of the acyl chlorinated graphene oxide prepared in S1 was added to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene, then 5 parts by weight of polyethylene glycol fatty acid ester and 2 parts by weight of triethylamine were added in sequence, and then under nitrogen protection, the mixture was stirred at 80 °C for 12 h; after the reaction was completed, it was washed with ethanol and dried at 40 °C to obtain modified graphene oxide.

[0082] S3. 0.5 part by weight of the modified graphene oxide obtained above was added to 260 parts by weight of absolute ethanol, and ultrasonically dispersed for 3 min under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution; then under a nitrogen atmosphere and at 50 °C, 0.5 part by weight of imidazolium ionic liquid was added to the above mixed solution, and then heated under reflux for 5 h; filtered, washed 3 times with absolute ethanol, and dried in vacuo at 55 °C to obtain composite modified graphene oxide.

[0083] The preparation method of the polyethylene glycol fatty acid ester in step S2 includes the following steps:

[0084] 1.4 parts by weight of palmitic acid and 1 part by weight of polyethylene glycol were added to 20 parts by weight of xylene and mixed, and then 0.07 part by weight of p-toluenesulfonic acid with a volume percentage of 2.5% was added as a catalyst. The mixture was heated under reflux at 250 rpm and 120 °C for 24 h. After the reaction was completed, the reaction mixture was cooled to room temperature, and the product was extracted 3 times with ethyl acetate, then extracted 3 times with saturated sodium chloride aqueous solution, and then the organic phase was extracted 3 times with deionized water, and the organic phase was collected. Anhydrous sodium sulfate was added to the organic phase, stirred and filtered, and the filtrate was collected. The solvent in the filtrate was evaporated using a rotary evaporator at 55 °C until the solvent was completely removed to obtain polyethylene glycol fatty acid ester.

[0085] The preparation method of the imidazolium ionic liquid in the step S3 is the same as that in Example 1.

[0086] Comparative Example 1

[0087] A preparation method of a diesel additive, which is different from Example 1 in that the preparation method of the composite modified graphene oxide includes the following steps:

[0088] S1. 1 part by weight of graphene oxide was added to 15 parts by weight of N,N-dimethylformamide, and then 45 parts by weight of thionyl chloride was added. Under nitrogen protection, the mixture was heated under reflux at 90 °C for 12 h to obtain a mixed reactant. The excess thionyl chloride in the mixed reactant was removed by distillation, and then washed with tetrahydrofuran and dried in vacuo to obtain acyl chloride graphene oxide.

[0089] S2. 0.2 part by weight of the acyl chloride graphene oxide prepared in S1 above was added to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene, and then 5 parts by weight of hexadecanol and 2 parts by weight of triethylamine were added in sequence, and then stirred at 80 °C for 12 h under nitrogen protection. After the reaction was completed, it was washed with ethanol and dried at 40 °C to obtain modified graphene oxide.

[0090] S3. 0.5 part by weight of the modified graphene oxide obtained above was added to 260 parts by weight of absolute ethanol, and ultrasonically dispersed for 3 min under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution. Then, 0.5 part by weight of imidazolium ionic liquid was added to the above mixed solution at 50 °C under a nitrogen atmosphere, and then heated under reflux for 5 h. Filtered, washed 3 times with absolute ethanol and dried in vacuo at 55 °C to obtain composite modified graphene oxide.

[0091] The preparation method of the imidazolium ionic liquid in the step S3 is the same as that in Example 1.

[0092] Comparative Example 2

[0093] A preparation method of a diesel additive, which is different from Example 1 in that the preparation method of the composite modified graphene oxide comprises the following steps:

[0094] S1. Add 1 part by weight of graphene oxide to 15 parts by weight of N,N-dimethylformamide, then add 45 parts by weight of thionyl chloride, and under nitrogen protection, heat and reflux at 90 °C for 12 h to obtain a mixed reactant; Distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran and dry in vacuum to obtain acyl chlorinated graphene oxide;

[0095] S2. Add 0.2 part by weight of the acyl chlorinated graphene oxide prepared in S1 above to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene, then sequentially add 5 parts by weight of polyethylene glycol and 2 parts by weight of triethylamine, and then under nitrogen protection, stir at 80 °C for 12 h; After the reaction is completed, wash with ethanol and dry at 40 °C to obtain modified graphene oxide;

[0096] S3. Add 0.5 part by weight of the modified graphene oxide obtained above to 260 parts by weight of absolute ethanol, and ultrasonically disperse for 3 min under the conditions of an ultrasonic frequency of 40 KHz and an ultrasonic power of 50 W to obtain a mixed solution; Then, under a nitrogen atmosphere and at 50 °C, add 0.5 part by weight of an imidazole ionic liquid to the above mixed solution, and then heat and reflux for 5 h; Filter, wash 3 times with absolute ethanol, and then dry in vacuum at 55 °C to obtain composite modified graphene oxide.

[0097] The preparation method of the imidazole ionic liquid in step S3 is the same as that in Example 1.

[0098] Comparative Example 3

[0099] A preparation method of a diesel additive, which is different from Example 1 in that the functional improver is composed of modified graphene oxide and nano-copper oxide mixed in a mass ratio of 3:1.

[0100] The preparation method of the modified graphene oxide comprises the following steps:

[0101] S1. Add 1 part by weight of graphene oxide to 15 parts by weight of N,N-dimethylformamide, then add 45 parts by weight of thionyl chloride, and under nitrogen protection, heat and reflux at 90 °C for 12 h to obtain a mixed reactant; Distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran and dry in vacuum to obtain acyl chlorinated graphene oxide; <U+

[0102] S2. Add 0.2 parts by weight of the acyl-chlorinated graphene oxide prepared in S1 above to a mixed solvent composed of 10 parts by weight of N,N-dimethylformamide and 15 parts by weight of toluene. Then, add 5 parts by weight of polyethylene glycol fatty acid ester and 2 parts by weight of triethylamine in sequence. Then, under nitrogen protection, stir at 80 °C for 12 h. After the reaction is completed, wash with ethanol and dry at 40 °C to obtain modified graphene oxide.

[0103] The preparation method of the polyethylene glycol fatty acid ester in step S2 is the same as that in Example 1.

[0104] Comparative Example 4

[0105] A preparation method of a diesel additive, which is different from Example 1 in that the functional improver is composite modified graphene oxide.

[0106] The preparation method of the composite modified graphene oxide is the same as that in Example 1.

[0107] Test Example 1

[0108] Anti-wear and lubrication performance test

[0109] Respectively mix the diesel additives prepared in Examples 1-5 and Comparative Examples 1-4 with No. -10 vehicle diesel (commercially available, Sinopec) evenly, control the volume ratio of the diesel additive to No. -10 vehicle diesel to be 1:1000, and then according to the standard of "SH / T 0765-2021 Evaluation of Diesel Lubricity - High Frequency Reciprocating Rig Method", test the wear scar diameter of the diesel. The test results are shown in Table 1 below:

[0110] Table 1

[0111] Wear scar diameter (μm) Example 1 306 Example 2 315 Example 3 318 Example 4 323 Example 5 326 Comparative Example 1 332 Comparative Example 2 340 Comparative Example 3 345 Comparative Example 4 358

[0112] As can be seen from Table 1, by comparing Examples 1-5 and Comparative Examples 1-4, the wear scar diameters of Examples 1-5 are smaller than those of Comparative Examples 1-4, indicating that the diesel additives prepared in Examples 1-5 have a greater improvement effect on the lubricity of diesel and have good anti-wear and lubrication effects, among which Example 1 has the best anti-wear and lubrication effect. The reason may be that in the preparation process of the diesel additive, the introduction of the functional improver composed of composite modified graphene oxide and nano-copper oxide is beneficial to reducing the wear scar diameter, reducing wear, and improving the anti-wear and lubrication performance of the diesel additive. The composite modified graphene oxide exhibits excellent anti-wear and friction-reducing properties, and can reduce the direct contact between metal surfaces by forming a lubricating film between the contact surfaces, thereby reducing wear and friction. When the composite modified graphene oxide is used synergistically with nano-copper oxide, the non-ionic surfactant characteristics of the polyethylene glycol fatty acid ester grafted on the composite modified graphene oxide may have a synergistic effect with nano-copper oxide, further reducing wear, and thus further improving the lubrication effect.

[0113] The wear scar diameter of Example 1 is smaller than that of Examples 2-5, showing better anti-wear and lubricating effects. The possible reason for the analysis is that compared with Example 1 in which polyethylene glycol fatty acid ester is prepared by introducing γ-linolenic acid, the linoleic acid structure in Example 2 contains two carbon-carbon double bonds, and oleic acid in Example 3 contains one double bond. The presence of carbon-carbon double bonds is beneficial to the flexibility and adsorption capacity of the lubricating film, and at the same time can improve the stability of the lubricating film. The carbon-carbon double bonds of linoleic acid and oleic acid are fewer than those of γ-linolenic acid. Therefore, the anti-wear and lubricating effects are not as good as those of Example 1; stearic acid in Example 4 lacks double bonds, and palmitic acid in Example 5 lacks double bonds and has a shorter chain length. Therefore, the stability and lubricity of its lubricating film are not as good as those of the polyethylene glycol fatty acid ester formed by γ-linolenic acid, and the anti-wear and lubricating effects are not as good as those of Example 1.

[0114] The wear scar diameter of Example 1 is smaller than that of Comparative Examples 1-2, showing better anti-wear and lubricating effects. The possible reason for the analysis is that compared with Example 1 in which graphene oxide is modified with polyethylene glycol fatty acid ester having polyethylene glycol segments and fatty acid segments, hexadecanol used in Comparative Example 1 is a short-chain alcohol, and its lubricating performance is not as good as that of long-chain fatty acid esters. The lubricating film formed by short-chain alcohols is thinner and it is difficult to form a stable protective layer on the metal surface. Therefore, the anti-wear performance is poor; although polyethylene glycol in Comparative Example 2 has good polarity, it lacks the lubricating performance of long-chain fatty acid esters, and it is difficult to form an effective lubricating film by using polyethylene glycol alone, resulting in a decrease in anti-wear performance.

[0115] The wear scar diameter of Example 1 is smaller than that of Comparative Example 3, indicating that the anti-wear and lubricating effect of Example 1 in which the functional improver is composed of composite modified graphene oxide and nano-copper oxide is better than that of Comparative Example 3 in which the functional improver is composed of modified graphene oxide and nano-copper oxide. The possible reason for the analysis is that ionic liquids themselves have good lubricating performance. Graphene oxide modified with imidazole ionic liquid can be evenly distributed in diesel due to its better dispersibility, which helps to give full play to the lubricating effect of graphene oxide. At the same time, the introduction of imidazole ionic liquid can also prevent the oxidation of the wear scar surface, prevent the generation of corrosive wear products, and reduce wear.

[0116] The wear scar diameter of Example 1 is smaller than that of Comparative Example 4, indicating that the anti-wear and lubricating effect of Example 1 with the functional improver composed of composite modified graphene oxide and nano-copper oxide is better than that of Comparative Example 4 with the functional improver of composite modified graphene oxide. The possible reason for the analysis is that nano-copper oxide has a smaller particle size and a larger specific surface area. During the friction process, nano-copper oxide can fill the microscopic unevenness on the surface, reduce the direct contact between the friction pairs, and play a role similar to that of a ball bearing, so as to form a uniform protective film on the friction surface and play a certain lubricating and anti-wear role. When composite modified graphene oxide and nano-copper oxide are used synergistically, composite modified graphene oxide can reduce the agglomeration phenomenon of nano-copper oxide, enabling it to better play the lubricating and anti-wear role. At the same time, the layered structure in composite modified graphene oxide can overlap and combine with the layered structure of nano-copper oxide, and can form a denser and stronger protective lubricating film on the metal surface. This composite protective film can effectively isolate friction, reduce the direct contact and wear of the metal surface. The synergistic effect of the two may better play the lubricating and anti-wear roles of the diesel additive, and also enhance the overall stability of the additive.

[0117] Test Example 2

[0118] Performance Test

[0119] Refer to the standard of "GB / T 265-1988 Determination Method for Kinematic Viscosity and Calculation Method for Dynamic Viscosity of Petroleum Products" to test the kinematic viscosity of the diesel additives of each example and comparative example at 100 °C; kinematic viscosity is an index to measure the internal friction when a fluid flows under the action of gravity, and kinematic viscosity reflects the fluidity of the oil product. The kinematic viscosity at 100 °C indicates the fluidity of the diesel additive at 100 °C, but the value should not be too high or too low; within the normal viscosity range, the larger the kinematic viscosity value at 100 °C, the relatively poorer the fluidity; the smaller the kinematic viscosity value at 100 °C, the relatively better the fluidity; the specific test results are shown in Table 2 below;

[0120] Refer to the standard of "GB / T 1995-1998 Calculation Method for Viscosity Index of Petroleum Products" to test the viscosity index of the diesel additives of each example and comparative example; the viscosity index measures the degree of change in the viscosity of the oil product with temperature, the stability of the oil product viscosity with temperature change. The higher the viscosity index, the smaller the change in the oil product viscosity with temperature; conversely, the viscosity changes greatly with temperature; the specific test results are shown in Table 2 below;

[0121] Refer to the standard of "GB / T 3535-2006 Determination Method for Pour Point of Petroleum Products" to test the pour point of the diesel additives of each example and comparative example; the pour point is the lowest temperature at which the diesel additive can maintain fluidity when cooled under specified conditions. The pour point reflects the fluidity of the oil product at low temperatures. The lower the value, the better the fluidity of the oil product at lower temperatures; the specific test results are shown in Table 2 below;

[0122] Refer to the standard of "GB / T 6538-2022 Determination of Apparent Viscosity of Engine Oils - Cold Start Simulator Method" to test the low-temperature dynamic viscosity of the diesel additives in each example and comparative example; the test of the low-temperature dynamic viscosity at -20°C represents the dynamic viscosity of the diesel additive at -20°C. The low-temperature dynamic viscosity reflects the fluidity of the oil product at low temperatures. The greater the dynamic viscosity, the greater the flow resistance and the more difficult the diesel flows; the specific test results are shown in Table 2 below;

[0123] Refer to the standard of "SH / T 0562-2013 Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low Temperatures" to test the low-temperature pumping viscosity; the low-temperature pumping viscosity reflects the pumping performance of the oil product at extremely low temperatures. The smaller the value, the easier the oil product is pumped at low temperatures, reducing the resistance during engine startup and operation; in this test, the low-temperature pumping viscosity at -25°C is tested; the specific test results are shown in Table 2 below;

[0124] The present invention uses a bench test to test the starting performance of the engine using the diesel additives of Examples 1-5 of the present invention. The results show that the engine can be smoothly ignited and started at -25°C.

[0125] Table 2

[0126] <![CDATA[Kinematic viscosity at 100 °C (mm 2 / s)]]> Viscosity index Pour point (℃) Low temperature dynamic viscosity at -20℃ (mPa•s) Low temperature pumping viscosity at -25℃ (mPa•s) Example 1 13.58 154 -43 6050 22100 Example 2 13.65 150 -40 6180 23200 Example 3 13.82 152 -41 6220 23700 Example 4 13.91 149 -39 6280 24000 Example 5 14.03 147 -38 6300 24180 Comparative Example 1 14.32 142 -36 6350 26000 Comparative Example 2 14.43 139 -35 6450 27000 Comparative Example 3 14.61 143 -36 6320 26500 Comparative Example 4 14.86 126 -32 6600 32000

[0127] As can be seen from Table 2, by comparing Examples 1-5 and Comparative Examples 1-4, it is found that the kinematic viscosity at 100°C of Examples 1-5 is lower than that of Comparative Examples 1-4, indicating that the fluidity of the diesel additives prepared in Examples 1-5 of the present invention at 100°C is better than that of Comparative Examples 1-4, which can ensure that when the diesel is working at high temperature in the engine, the additive and the diesel are evenly mixed, a stable oil film is formed on the surface of the engine components, effectively lubricating, and reducing the wear of engine components.

[0128] By comparing Examples 1-5 and Comparative Examples 1-4, it is found that the viscosity index of Examples 1-5 is higher than that of Comparative Examples 1-4, indicating that the degree of change of the oil viscosity with temperature in Examples 1-5 is smaller than that in Comparative Examples 1-4, which can keep the diesel at a stable performance at different temperatures, facilitating the smooth fuel delivery and the normal startup of the engine.

[0129] By comparing Examples 1-5 with Comparative Examples 1-4, it was found that the pour points, low-temperature kinematic viscosities at -20°C, and low-temperature pumping viscosities at -25°C of Examples 1-5 were lower than those of Comparative Examples 1-4. This indicates that compared with Comparative Examples 1-4, the diesel additives prepared in Examples 1-5 can maintain better fluidity at lower temperatures, making the diesel less likely to solidify at lower temperatures, having better low-temperature fluidity. At the same time, it can avoid the fuel supply system from being blocked in cold environments, resulting in the engine being unable to start, which is beneficial to the normal pumping of diesel at low temperatures and maintaining the stable operation of the engine.

[0130] Based on the above test results, taking Example 1 with the best test effect of the present invention as an example for cause analysis, the possible reason may be that the present invention introduces the synergistic use of composite modified graphene oxide and a functional improver as the functional improver. The introduction of imidazolium ionic liquid in the composite modified graphene oxide enhances the thermal stability and chemical stability of graphene oxide, enabling it to maintain good lubrication performance under high-temperature and high-load conditions, which is beneficial to the high-temperature kinematic viscosity of the diesel additive. And the composite modified graphene oxide has good compatibility with the mineral base oil, can form a relatively stable dispersion system in the diesel additive. Moreover, the interaction between the composite modified graphene oxide nanosheets and the interaction between the polyethylene glycol chain segments and γ-linolenic acid long-chain structure in its structure and the base oil molecules can form a network-like structure in the diesel additive, which can effectively restrict the movement of the diesel additive molecules, change the microstructure of the diesel additive, and make the intermolecular sliding and arrangement changes of the diesel additive more orderly when the temperature changes, thus improving the viscosity index. At the same time, in the functional improver, the composite modified graphene oxide and nano-copper oxide are used synergistically. The composite modified graphene oxide can improve the dispersion stability of nano-copper oxide in the diesel additive, thereby affecting the kinematic viscosity. And the composite modified graphene oxide and nano-copper oxide can form strong intermolecular forces with the molecules of the diesel additive, interweaving with the surrounding diesel additive molecules, which can further enhance the structure of the network formed by the composite modified graphene oxide, thus constructing a more stable microstructure in the diesel additive. This structure can remain relatively stable at different temperatures, reducing the influence of temperature on the molecular arrangement and movement of the diesel additive.

[0131] The synergistic use of composite modified graphene oxide and nano-copper oxide is introduced. The polyethylene glycol fatty acid ester grafted on the composite modified graphene oxide may interfere with the orderly arrangement of the base oil molecules at low temperatures, hinder the formation and growth of wax crystals, thereby reducing the pour point of the diesel additive and improving the low-temperature fluidity. At the same time, the polar groups of the grafted ionic liquid in the composite modified graphene oxide may further enhance the wax crystal dispersion ability of the polyethylene glycol fatty acid ester, further optimizing the low-temperature performance.

Claims

1. A preparation method of a diesel additive, characterized in that, It includes the following steps: Weigh each raw material separately: functional improver, antioxidant, dispersant and base oil, and then mix the raw materials. Under the conditions of ultrasonic frequency of 30 - 50 KHz and ultrasonic power of 50 - 100 W, ultrasonic mix for 3 - 6 min until evenly mixed to obtain a diesel additive; The functional improver is composed of composite modified graphene oxide and nano - copper oxide mixed in a mass ratio of 2 - 3:1; The composite modified graphene oxide is graphene oxide modified by polyethylene glycol fatty acid ester and imidazolium ionic liquid.

2. The preparation method of the diesel fuel additive according to claim 1, characterized in that: The proportion of the raw material components includes, by mass percentage: Functional improver 1 - 5%, antioxidant 0.5 - 1% and dispersant 0.1 - 0.3%, and the balance is base oil.

3. The preparation method of the diesel fuel additive according to claim 1, wherein: The preparation method of the composite modified graphene oxide includes the following steps, by weight: S1. Add 0.5 - 1.5 parts of graphene oxide to 10 - 20 parts of N,N - dimethylformamide, then add 40 - 60 parts of thionyl chloride. Under nitrogen protection, heat - reflux at 85 - 95 °C for 10 - 13 h to obtain a mixed reactant; Distill the mixed reactant to remove the excess thionyl chloride, then wash with tetrahydrofuran and dry in vacuum to obtain acyl - chlorinated graphene oxide; S2. Add 0.1 - 0.3 parts of the acyl - chlorinated graphene oxide prepared in S1 above to a mixed solvent composed of 8 - 15 parts of N,N - dimethylformamide and 10 - 20 parts of toluene, then add 2 - 6 parts of polyethylene glycol fatty acid ester and 1.5 - 2.5 parts of triethylamine in sequence, and then stir at 75 - 85 °C for 10 - 13 h under nitrogen protection; After the reaction is completed, wash with ethanol and dry at 40 - 50 °C to obtain modified graphene oxide; S3. Add 0.4 - 0.6 parts of the modified graphene oxide obtained above to 200 - 300 parts of absolute ethanol, ultrasonically disperse for 2 - 5 min under the conditions of ultrasonic frequency of 30 - 50 KHz and ultrasonic power of 50 - 100 W to obtain a mixed solution; Then, under a nitrogen atmosphere and at 45 - 60 °C, add 0.4 - 0.6 parts of imidazolium ionic liquid to the above - mentioned mixed solution, and then heat - reflux for 4 - 6 h; Filter, wash with absolute ethanol 2 - 3 times and then dry in vacuum at 50 - 60 °C to obtain composite modified graphene oxide.

4. The preparation method of the diesel fuel additive according to claim 3, characterized in that: The preparation method of the polyethylene glycol fatty acid ester includes the following steps, by weight: 1.2 - 1.5 parts of fatty acid compound and 0.9 - 1.1 parts of polyethylene glycol are added to 20 - 30 parts of xylene and mixed, then 0.05 - 0.08 parts of p - toluenesulfonic acid is added as a catalyst, and the mixture is heated under reflux at 200 - 400 rpm and 115 - 125 °C for 20 - 25 h; after the reaction is completed, the reaction mixture is cooled to room temperature, and the product is extracted 2 - 3 times with ethyl acetate, then extracted 2 - 3 times with saturated sodium chloride aqueous solution, and then the organic phase is extracted 3 - 4 times with deionized water, and the organic phase is collected; anhydrous sodium sulfate is added to the organic phase, stirred and filtered, and the filtrate is collected; the solvent in the filtrate is evaporated using a rotary evaporator at 50 - 60 °C until the solvent is completely removed to obtain polyethylene glycol fatty acid ester.

5. The preparation method of the diesel fuel additive according to claim 4, characterized in that: The fatty acid compound is selected from one of γ - linolenic acid, linoleic acid, oleic acid, stearic acid, and palmitic acid.

6. The preparation method of the diesel fuel additive according to claim 3, characterized in that: The preparation method of the imidazolium ionic liquid in step S3 includes the following steps, by weight: 5 - 6 parts of 3 - chloromethoxypropylsilane and 1.5 - 2.2 parts of imidazole are mixed at 105 - 115 °C, and the mixture is stirred and reacted at 300 - 500 rpm under a nitrogen atmosphere for 20 - 25 h; then the reaction product is washed with ethyl acetate to obtain the imidazolium ionic liquid.

7. The preparation method of the diesel fuel additive according to claim 1, wherein: The base oil is selected from one or more of API I, II, III, IV, and V base oils.

8. The preparation method of the diesel fuel additive according to claim 1, characterized in that: The antioxidant is selected from at least one of methyl epoxy oleate, 2,6 - di - tert - butyl - p - cresol, and 2,6 - di - tert - butylphenol.

9. The preparation method of the diesel additive according to claim 1, characterized in that: The dispersant is selected from at least one of tributyl phosphate, 3 - (2 - benzothiazolyl) - 2 - ethoxypropanol, and polyisobutylene succinimide.

10. A diesel additive, characterized in that: Prepared by the method according to any one of claims 1 - 9.