A fuel additive containing a modified fatty acid and a method for its preparation

Abstract

The present application relates to the technical field of fuel additive, and discloses a fuel additive containing modified fatty acid and a preparation method thereof, which is composed of 40-60% of modified fatty acid, 15-25% of composite additive, 3-8% of antioxidant, 8-15% of di-tert-butyl peroxide and 5-12% of modified adamantane by mass percentage.The preparation method comprises three steps of modified fatty acid preparation, composite additive preparation and component mixing reaction.The fuel additive solves the problems of poor compatibility of unmodified fatty acid with fuel and insufficient high-temperature stability, has simple and environment-friendly preparation process, has excellent lubricating performance, high-temperature stability and combustion promotion effect, can effectively improve fuel combustion efficiency, reduce pollutant emission in tail gas, has no adverse effect on engine parts, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of fuel additive technology, specifically to a fuel additive containing modified fatty acids and its preparation method. Background Technology

[0002] With the continuous growth of energy demand and increasingly stringent environmental protection requirements, improving fuel combustion performance and reducing pollutant emissions have become important research directions in the fuel field. Fuel additives, as a key means of improving fuel quality, can effectively improve fuel lubricity, anti-wear properties, combustion efficiency, and other properties, thereby reducing engine wear and exhaust pollutant emissions.

[0003] Fatty acid compounds are frequently used in the preparation of fuel additives due to their wide availability and environmental friendliness. However, unmodified fatty acids suffer from poor water solubility, poor fuel compatibility, and insufficient high-temperature stability, limiting their application in fuel additives. Existing technologies for modifying fatty acids mainly include esterification, amidation, and sulfonation, but these methods generally suffer from harsh reaction conditions, complex processes, and low product yields. For example, in the molecular distillation method for separating and preparing fatty acid anti-wear agents, the relatively similar physical properties of the components in the crude fatty acid result in unsatisfactory product yields and quality; solvent freezing separation methods suffer from high energy consumption and the volatile organic solvents that pollute the environment.

[0004] Furthermore, the effectiveness of existing fatty acid-based fuel additives in improving fuel combustion efficiency and reducing exhaust emissions still needs improvement, and some additives can have adverse effects on engine components. Therefore, developing a fuel additive containing modified fatty acids that is simple to prepare, environmentally friendly, efficient, and can significantly improve the overall performance of fuel is of significant practical importance. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a fuel additive containing modified fatty acids and its preparation method, which has better lubrication performance and stability.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] To achieve the above objectives, the present invention provides the following technical solution: a fuel additive containing modified fatty acids, characterized in that, by mass percentage, its raw material composition includes: 40-60% modified fatty acids, 15-25% composite additives, 3-8% antioxidants, 8-15% di-tert-butyl peroxide, and 5-12% modified adamantane;

[0008] The modified fatty acid is prepared by amidation reaction of fatty acid and alcohol amine compound. The specific preparation steps are as follows: fatty acid and alcohol amine compound are added to reaction vessel at a molar ratio of 1:1.2-1.5. Under nitrogen protection, the temperature is raised to 120-150℃ and stirred for 3-5 hours. After the reaction is completed, the unreacted raw materials are removed by vacuum distillation to obtain modified fatty acid.

[0009] Preferably, the fatty acid is one of palmitic acid, stearic acid, oleic acid, and linoleic acid; the alkanolamine compound is one of diethanolamine and diisopropanolamine. Palmitic acid, stearic acid, oleic acid, and linoleic acid are selected as the base fatty acids because these fatty acids are widely available (e.g., extracted from vegetable oils), environmentally friendly, and their long-chain structure provides a lubricating basis. When combined with alkanolamine compounds such as diethanolamine and diisopropanolamine, the amino and hydroxyl groups they contain can undergo amidation reactions with fatty acids, specifically addressing the defects of unmodified fatty acids. The alkanolamine compounds are limited to diethanolamine and diisopropanolamine (both secondary amines), whose -NH- groups can undergo amidation reactions with the carboxyl groups of fatty acids. At the same time, the hydroxyl groups can enhance molecular polarity and adsorption capacity on metal surfaces. Compared with primary amines, secondary amines have moderate reactivity, which can avoid excessive reaction and the generation of byproducts.

[0010] Preferably, the composite additive is a mixture of calcium dodecylbenzenesulfonate and polyoxyethylene ether in a mass ratio of 1:0.8-1.2.

[0011] Preferably, the antioxidant is one of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite.

[0012] Preferably, the method for preparing the modified adamantane is as follows:

[0013] 1,6-hexanedialdehyde and 1-adamantaneamine were dissolved in 10-12 mL of anhydrous ethanol, stirred and mixed, and formic acid catalyst was added. The mixture was refluxed at 70-75 °C for 2-3 h. After the reaction was completed, the mixture was filtered, washed 2-3 times with a small amount of anhydrous ethanol, and dried to obtain modified adamantane. Nitrogen-containing flexible segments were introduced into the 1-adamantane molecule to form a "rigid adamantane core-flexible nitrogen-containing chain" structure. The rigid core provides excellent thermal stability, and the flexible chain enhances compatibility with other components.

[0014] Preferably, the ratio of 1,6-hexanedialdehyde, 1-adamantaneamine, and formic acid catalyst is 2-3 mmol: 4-6 mmol: 0.04-0.05 mL.

[0015] Preferably, it includes the following steps:

[0016] S1. Preparation of modified fatty acids: Fatty acids and alkanolamine compounds are added to a reaction vessel at a molar ratio of 1:1.2-1.5. Nitrogen gas is introduced for protection, the temperature is raised to 120-150℃, the stirring speed is controlled at 200-300 r / min, and the reaction is carried out for 3-5 h. After the reaction is completed, the reaction product is placed in a vacuum distillation apparatus and distilled for 30-60 min under a vacuum of 0.08-0.1 MPa and a temperature of 160-180℃ to remove unreacted raw materials and obtain modified fatty acids.

[0017] S2. Preparation of composite additive: Add calcium dodecylbenzenesulfonate and polyoxyethylene ether to a mixing tank at a mass ratio of 1:0.8-1.2, heat to 60-80℃, stir and mix to obtain composite additive;

[0018] S3. Preparation of fuel additives by mixing: According to the raw material composition ratio, the modified fatty acid prepared in S1, the composite additive prepared in S2, the antioxidant, di-tert-butyl peroxide, and the modified adamantane are added to the reactor in sequence, heated to 80-100℃, and the stirring speed is controlled at 150-250r / min. The mixture is reacted for 1.5-2.5h. After the reaction is completed, it is cooled to room temperature to obtain the fuel additive containing modified fatty acids.

[0019] Preferably, the mixing time in step S2 is 1-2 hours.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] This invention prepares modified fatty acids by reacting fatty acids with alkanolamine compounds. The modified fatty acid structure gives the molecule both polar groups and nonpolar long chains. The polar groups can be firmly adsorbed onto metal surfaces, while the nonpolar long chains are well compatible with fuel molecules, forming a protective film that combines adsorption stability and lubrication continuity. Simultaneously, a composite additive (a blend of calcium dodecylbenzenesulfonate and polyoxyethylene ether) works synergistically to further improve the dispersion uniformity of each component in the fuel, preventing the modified fatty acid from agglomerating and causing lubrication failure. During fuel combustion in an engine, local temperatures can reach hundreds of degrees Celsius. Ordinary fatty acid additives are prone to oxidative decomposition and thermal cracking, leading to additive failure and potentially producing impurities such as carbon deposits. The modified fatty acid structure in this invention has a higher bond energy, resulting in significantly improved thermal stability compared to the carboxyl structure of unmodified fatty acids. Combined with antioxidants such as 2,6-di-tert-butyl-p-cresol or triphenyl phosphite, it can inhibit the oxidation reactions of the additive itself and the fuel through mechanisms such as capturing free radicals and decomposing peroxides.

[0022] Di-tert-butyl peroxide, as a combustion improver, decomposes during combustion to generate free radicals, lowering the fuel ignition temperature, promoting complete pyrolysis of fuel molecules, and reducing incomplete combustion. Modified adamantane, a key component of this invention, possesses multiple performance advantages due to its unique structural design and modification process, playing a core supporting role in the overall effect of the fuel additive. Adamantane itself has a highly symmetrical tricyclic decane structure with strong molecular rigidity and high bond energy, exhibiting excellent thermal and chemical stability. This invention modifies adamantane through the condensation reaction of 1,6-hexanedialdehyde and 1-adamantaneamine, introducing nitrogen-containing flexible segments into the adamantane molecule to form a unique "rigid core-flexible chain" structure. The rigid adamantane core provides excellent thermal stability and resistance to decomposition, maintaining structural stability in high-temperature combustion environments and preventing impurities from self-pyrolysis. The flexible nitrogen-containing segments enhance compatibility with other components (modified fatty acids, composite additives, etc.), while the nitrogen-containing groups can form weak coordination with metal surfaces. Modified adamantane helps form a more stable lubricating film by aiding the modification of fatty acids. The nitrogen-containing groups in the modified adamantane molecule act as "ignition-promoting centers" during combustion, reducing the activation energy of the fuel and accelerating the combustion reaction rate. Simultaneously, the rigid core structure inhibits excessive polymerization of free radicals during combustion, reducing the formation of carbon deposit precursors, preventing carbon buildup inside the engine, ensuring unobstructed combustion channels, and further improving combustion efficiency. The rigid core of modified adamantane can embed itself into the lubricating film formed by modified fatty acids, acting as a "support point" to improve the load-bearing capacity and wear resistance of the lubricating film. The flexible segments can tightly bind with the lubricating film molecules, reducing the shedding of the lubricating film under high load and high speed, and synergistically with composite additives to further reduce the wear scar diameter. The rigid structure of modified adamantane hinders the contact between oxygen and other additive molecules, reducing oxidation reactions. Simultaneously, the nitrogen-containing groups can synergistically work with antioxidants, improving the antioxidant's free radical capture efficiency and further enhancing the high-temperature stability and storage stability of the additives. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Calcium dodecylbenzenesulfonate: Model T106A.

[0025] Polyoxyethylene ether: Model NP-9.

[0026] Example 1:

[0027] Preparation of modified fatty acids: Palmitic acid was selected as the fatty acid and diethanolamine as the alcohol amine compound. They were added to the reaction vessel at a molar ratio of 1:1.2, nitrogen gas was introduced for protection, the temperature was raised to 120℃, the stirring speed was controlled at 200 r / min, and the reaction was carried out for 3 h. After the reaction was completed, the reaction product was placed in a vacuum distillation apparatus and distilled for 30 min under a vacuum of 0.08 MPa and a temperature of 160℃ to remove unreacted raw materials and obtain modified fatty acids.

[0028] Preparation of composite additive: Calcium dodecylbenzenesulfonate and polyoxyethylene ether were added to a mixing tank at a mass ratio of 1:0.8, heated to 60°C, and stirred for 1 hour to obtain the composite additive.

[0029] Preparation of modified adamantane: 1,6-hexanedialdehyde, 1-adamantaneamine, and formic acid catalyst were weighed according to the ratio of 2 mmol:4 mmol:0.04 mL. 1,6-hexanedialdehyde and 1-adamantaneamine were dissolved in 10 mL of anhydrous ethanol and stirred. Formic acid catalyst was added and the mixture was refluxed at 70 °C for 2 h. After the reaction was completed, the mixture was filtered, washed twice with a small amount of anhydrous ethanol, and dried to obtain modified adamantane.

[0030] Fuel additive preparation by mixing: 60% modified fatty acid, 22% composite additive, 5% antioxidant (2,6-di-tert-butyl-p-cresol), 8% di-tert-butyl peroxide, and 5% modified adamantane by mass percentage were added to a reactor in sequence, heated to 80°C, and stirred at 150 r / min for 1.5 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a fuel additive containing modified fatty acid.

[0031] Example 2:

[0032] Preparation of modified fatty acids: Stearic acid was selected as the fatty acid and diisopropanolamine as the alkanolamine compound. They were added to the reaction vessel at a molar ratio of 1:1.3, and nitrogen gas was introduced for protection. The temperature was raised to 130℃, and the stirring speed was controlled at 250 r / min. The reaction was carried out for 4 h. After the reaction was completed, the reaction product was placed in a vacuum distillation apparatus and distilled for 45 min under a vacuum of 0.09 MPa and a temperature of 170℃ to remove unreacted raw materials and obtain modified fatty acids.

[0033] Preparation of composite additive: Calcium dodecylbenzenesulfonate and polyoxyethylene ether were added to a mixing tank at a mass ratio of 1:1.0, heated to 70°C, and stirred for 1.5 h to obtain the composite additive.

[0034] Preparation of modified adamantane: 1,6-hexanedialdehyde, 1-adamantaneamine, and formic acid catalyst were weighed according to the ratio of 2.5 mmol: 5 mmol: 0.045 mL. 1,6-hexanedialdehyde and 1-adamantaneamine were dissolved in 11 mL of anhydrous ethanol and stirred. Formic acid catalyst was added and the mixture was refluxed at 72 °C for 2.5 h. After the reaction was completed, the mixture was filtered, washed three times with a small amount of anhydrous ethanol, and dried to obtain modified adamantane.

[0035] Fuel additive preparation by mixing: 51% modified fatty acid, 20% composite additive, 5% antioxidant (triphenyl phosphite), 12% di-tert-butyl peroxide, and 12% modified adamantane by mass percentage were added to a reaction vessel in sequence, heated to 90°C, and stirred at 200 r / min for 2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a fuel additive containing modified fatty acid.

[0036] Example 3:

[0037] Preparation of modified fatty acids: Oleic acid was selected as the fatty acid and diisopropanolamine as the alkanolamine compound. They were added to the reaction vessel at a molar ratio of 1:1.4, and nitrogen gas was introduced for protection. The temperature was raised to 140℃, and the stirring speed was controlled at 280 r / min. The reaction was carried out for 4.5 h. After the reaction was completed, the reaction product was placed in a vacuum distillation apparatus and distilled for 50 min under a vacuum of 0.095 MPa and a temperature of 175℃ to remove unreacted raw materials and obtain modified fatty acids.

[0038] Preparation of composite additive: Calcium dodecylbenzenesulfonate and polyoxyethylene ether were added to a mixing tank at a mass ratio of 1:1.1, heated to 75°C, and stirred for 1.8 hours to obtain the composite additive.

[0039] Preparation of modified adamantane: 1,6-hexanedialdehyde, 1-adamantaneamine, and formic acid catalyst were weighed according to the ratio of 2.8 mmol: 5.5 mmol: 0.048 mL. 1,6-hexanedialdehyde and 1-adamantaneamine were dissolved in 11.5 mL of anhydrous ethanol and stirred. Formic acid catalyst was added and the mixture was refluxed at 74 °C for 2.8 h. After the reaction was completed, the mixture was filtered, washed three times with a small amount of anhydrous ethanol, and dried to obtain modified adamantane.

[0040] Fuel additive preparation by mixing: 55% modified fatty acid, 22% composite additive, 7% antioxidant (2,6-di-tert-butyl-p-cresol), 8% di-tert-butyl peroxide, and 8% modified adamantane by mass percentage were added to a reaction vessel in sequence, heated to 95°C, and stirred at 230 r / min for 2.2 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a fuel additive containing modified fatty acid.

[0041] Comparative Example 1:

[0042] Unmodified palmitic acid was used to replace the modified fatty acid in Example 3, and the remaining raw materials and preparation steps were exactly the same as in Example 3 to obtain a fuel additive.

[0043] Comparative Example 2:

[0044] Using 1,6-hexanedialdehyde instead of modified adamantane, the remaining raw materials and preparation steps were exactly the same as in Example 3, to obtain the fuel additive.

[0045] 1. Lubrication performance testing shall be conducted in accordance with GB / T3142-2019 "Determination of Lubricant Carrying Capacity (Four-Ball Method)".

[0046] 2. High-temperature stability test (mass loss rate determination).

[0047] Test equipment: constant temperature drying oven, electronic balance (accuracy 0.0001g).

[0048] Test conditions: The drying oven temperature was set to 200℃, and the holding time was 4 hours.

[0049] Test procedure: Accurately weigh approximately 5g of fuel additive sample and place it in a pre-weighed crucible, recording the initial mass m1 of the sample; place the crucible in a constant-temperature drying oven preheated to 200℃, keep it at that temperature for 4 hours, then remove it and cool it to room temperature in a desiccator, weighing the remaining mass m2 of the sample; calculate the mass loss rate using the following formula: mass loss rate (%) = (m1-m2) / m1×100%, the lower the mass loss rate, the better the high-temperature stability.

[0050] 3. Combustion efficiency test.

[0051] Testing equipment: small internal combustion engine test bench, fuel consumption meter, power tester.

[0052] Test subjects: 1000mL of gasoline as the base fuel was used to prepare test fuels by adding 5mL of the fuel additive to each fuel; the blank group was 1000mL of base fuel without additives.

[0053] Test conditions: The internal combustion engine speed was fixed at 2000 r / min, the load was 70% of the rated load, and it ran continuously for 1 hour.

[0054] Test steps: Record the fuel consumption V0 and V1 of the blank group and the test group during the test time, as well as the output power P0 and P1; calculate the combustion efficiency improvement rate according to the following formula: Combustion efficiency improvement rate (%) = [(P1 / V1) - (P0 / V0)] / (P0 / V0) × 100%. The higher the value, the more significant the combustion efficiency improvement effect.

[0055] 4. Exhaust gas pollutant emission test.

[0056] Testing equipment: Automotive exhaust gas analyzer (capable of detecting CO and NO) x concentration).

[0057] Test conditions: The same internal combustion engine operating conditions as the combustion efficiency test, and the test begins after the internal combustion engine has been running stably.

[0058] Test procedure: Detect CO and NO in the exhaust gas of the blank group (basic fuel) and the test group (including additive fuel) respectively. x The concentrations were recorded as C0 (blank group) and C1 (test group); the emission reduction rate was calculated using the following formula: Emission reduction rate (%) = (C0-C1) / C0×100%. The higher the value, the better the pollutant emission reduction effect.

[0059] 5. Fuel compatibility test.

[0060] Testing equipment: constant temperature chamber, transparent sealed container.

[0061] Test conditions: temperature 25℃, standing time 72h.

[0062] Test procedure: Add 0.5 mL of fuel additive to 49.5 mL of gasoline and 49.5 mL of diesel fuel respectively, stir well and pour into a transparent sealed container; place the container in a constant temperature chamber at 25℃ and let it stand for 72 hours, observe whether the fuel system shows phenomena such as layering, precipitation, or turbidity; if the system remains uniform and transparent, without layering or precipitation, it indicates good compatibility; otherwise, the compatibility is poor.

[0063] The modified fatty acid fuel additives prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to systematic performance tests according to the test methods (lubrication performance, high temperature stability, combustion efficiency, exhaust pollutant emissions, and fuel compatibility). The test results are shown in Table 1 below. All data are the average of three parallel tests to ensure accuracy and repeatability.

[0064] Table 1: Performance Tests

[0065]

[0066] As shown in Table 1, the lubrication performance of Examples 1-3 is as follows: the wear scar diameter is less than 0.35 mm, and it gradually decreases with the optimization of the formula. Among them, the wear scar diameter of Example 3 is only 0.25 mm, which shows the synergistic lubrication effect of modified fatty acid and modified adamantane. Comparative Example 1 uses unmodified palmitic acid, which has poor compatibility with fuel and the lubricating film is not fully formed, resulting in a wear scar diameter of 0.59 mm. Comparative Example 2 uses 1,6-hexanedialdehyde instead of modified adamantane, which loses the lubrication support of the rigid core, and the wear scar diameter increases to 0.43 mm, which is worse than that of the Examples.

[0067] High-temperature stability: The mass loss rate of Examples 1-3 was less than 1.2%. The unmodified fatty acid in Comparative Example 1 was prone to pyrolysis, with a mass loss rate of 3.6%. The 1,6-hexanedialdehyde in Comparative Example 2 had poor thermal stability and was easily volatilized at high temperatures, with a mass loss rate of 2.0%. Combustion efficiency and exhaust emissions: The combustion efficiency improvement rate of Examples 2 and 3 both exceeded 11%, and the exhaust pollutant reduction rate was significantly better than other groups. This was due to the ignition promotion and carbon deposition inhibition effects of modified adamantane, as well as the atomization optimization effect of modified fatty acids. Comparative Example 1 had an efficiency improvement rate of only 4.5% due to the poor compatibility of unmodified fatty acids and incomplete combustion, resulting in limited pollutant emission reduction. Comparative Example 2 lacked the catalytic combustion effect of modified adamantane, and its efficiency improvement rate and emission reduction effect were significantly weaker than those of the Examples. Fuel compatibility: Examples 1-3 all showed excellent compatibility, indicating the effectiveness of the combination of modified fatty acids and composite additives in preventing component agglomeration; the unmodified palmitic acid in Comparative Example 1 had a large difference in polarity with the fuel, resulting in turbid precipitation; the 1,6-hexanedialdehyde in Comparative Example 2 had poor compatibility with other components, leading to slight stratification, which verified the role of the modified adamantane "rigid core-flexible chain" structure in improving the system compatibility.

[0068] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0070] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A fuel additive containing modified fatty acids, characterized in that, By mass percentage, its raw material composition includes: 40-60% modified fatty acids, 15-25% compound additives, 3-8% antioxidants, 8-15% di-tert-butyl peroxide, and 5-12% modified adamantane; The modified fatty acid is prepared by amidation reaction of fatty acid and alcohol amine compound. The specific preparation steps are as follows: fatty acid and alcohol amine compound are added to reaction vessel at a molar ratio of 1:1.2-1.

5. Under nitrogen protection, the temperature is raised to 120-150℃ and stirred for 3-5 hours. After the reaction is completed, the unreacted raw material is removed by vacuum distillation to obtain modified fatty acid. The composite additive is composed of calcium dodecylbenzenesulfonate and polyoxyethylene ether mixed at a mass ratio of 1:0.8-1.2; The antioxidant is one of 2,6-di-tert-butyl-p-cresol and triphenyl phosphite; The method for preparing the modified adamantane is as follows: Dissolve 1,6-hexanedialdehyde and 1-adamantaneamine in 10-12 mL of anhydrous ethanol, stir and mix, continue to add formic acid catalyst, reflux at 70-75℃ for 2-3 h, filter after completion, wash 2-3 times with a small amount of anhydrous ethanol, dry to obtain modified adamantane. The ratio of 1,6-hexanedialdehyde, 1-adamantaneamine, and formic acid catalyst is 2-3 mmol: 4-6 mmol: 0.04-0.05 mL.

2. The fuel additive containing modified fatty acids according to claim 1, characterized in that, The fatty acid is one of palmitic acid, stearic acid, oleic acid, and linoleic acid; the alcohol amine compound is one of diethanolamine and diisopropanolamine.

3. A method for preparing a fuel additive containing modified fatty acids as described in any one of claims 1-2, characterized in that, Includes the following steps: S1. Preparation of modified fatty acids: Fatty acids and alkanolamine compounds are added to a reaction vessel at a molar ratio of 1:1.2-1.

5. Nitrogen gas is introduced for protection, the temperature is raised to 120-150℃, the stirring speed is controlled at 200-300 r / min, and the reaction is carried out for 3-5 h. After the reaction is completed, the reaction product is placed in a vacuum distillation apparatus and distilled for 30-60 min under a vacuum of 0.08-0.1 MPa and a temperature of 160-180℃ to remove unreacted raw materials and obtain modified fatty acids. S2. Preparation of composite additive: Add calcium dodecylbenzenesulfonate and polyoxyethylene ether to a mixing tank at a mass ratio of 1:0.8-1.2, heat to 60-80℃, stir and mix to obtain composite additive; S3. Preparation of fuel additives by mixing: According to the raw material composition ratio, the modified fatty acid prepared in S1, the composite additive prepared in S2, the antioxidant, di-tert-butyl peroxide, and the modified adamantane are added to the reactor in sequence, heated to 80-100℃, and the stirring speed is controlled at 150-250r / min. The mixture is reacted for 1.5-2.5h. After the reaction is completed, it is cooled to room temperature to obtain the fuel additive containing modified fatty acids.

4. The method for preparing the fuel additive containing modified fatty acids according to claim 3, characterized in that, The mixing time in S2 is 1-2 hours.

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