Environment-friendly gasoline antiknock agent and preparation method thereof

Abstract

The present application belongs to the field of gasoline additive, and particularly relates to an environment-friendly gasoline antiknock agent and a preparation method thereof. The antiknock agent comprises two newly designed modified compounds: 3,5-di-tert-butyl phenyl carborane carboxylate and 2-(dicyclohexyl phosphino)-1,2-oxaborinin-4-carboxylic acid iso-octyl ester. In the preparation, a cosolvent is first added into a reactor, and then the two modified compounds, polyisobutylene amine, isobutyl acetate and dimethyl malonate are sequentially added under an inert atmosphere. After mixing by continuous stirring, the temperature is raised, an antioxidant is added, and then stirring is continued. Finally, the product is obtained by cooling and filtering. The two modified compounds are prepared by condensation reaction of carborane carboxylic acid and steric phenol, esterification of oxaborinin carboxylic acid and iso-octanol, and then phosphination reaction. The antiknock agent does not contain metal elements, has biodegradable characteristics, can significantly improve the octane number of gasoline and reduce engine deposits and harmful gas emissions, and meets the green environmental protection requirements.

Description

Technical Field

[0001] This invention belongs to the field of gasoline additive technology, specifically relating to an environmentally friendly gasoline antiknock agent and its preparation method. Background Technology

[0002] As an indispensable power source in modern industry and transportation, gasoline's combustion efficiency and cleanliness have always been a focus of research. Among the many performance indicators of gasoline, anti-knock performance is particularly crucial, directly affecting the power output, fuel economy, and service life of internal combustion engines. Historically, organometallic compounds such as tetraethyl lead were widely used as anti-knock agents to increase gasoline octane rating. While effective, the lead-containing particulate matter produced after combustion is highly toxic to the human nervous system and causes persistent environmental pollution, leading to its widespread ban globally. Subsequent lead-free metal anti-knock agents such as manganese-based agents have mitigated lead pollution to some extent, but the solid particulate matter formed after combustion can still clog or chemically poison engine exhaust treatment devices such as three-way catalytic converters.

[0003] Currently disclosed non-metallic antiknock solutions still have significant shortcomings in terms of environmental protection, safety, and process complexity. Specifically, patent CN112760143A discloses a non-metallic gasoline antiknock agent, which uses 2-naphthylamine, a strong carcinogen, as a co-solvent, posing clear safety and environmental risks. Furthermore, its core components, methylformamide and nitrobanane, also have certain toxicity and environmental accumulation risks. While patent CN108485736B emphasizes environmental friendliness, it introduces lithium hydroxide into its antiknock agent base material, essentially remaining an alkali metal-containing antiknock system, not a truly metal-free solution. In addition, its preparation process involves multiple transition metal nitrates and high-temperature calcination steps, resulting in complex processes, high energy consumption, potential heavy metal pollution, and difficulties in scale-up production. These existing technologies either contain toxic components, have complex and energy-intensive processes, or still contain metallic components, all of which fail to meet the stringent environmental and safety requirements of modern clean fuels.

[0004] Therefore, developing a truly metal-free, low-toxicity, mildly synthesized, and environmentally compatible novel antiknock agent has become an urgent technical problem to be solved in this field. Based on this, this invention constructs a composite antiknock system with boron and phosphorus organic compounds as its core through innovative molecular design. This technical solution completely eliminates the metal components commonly found in traditional antiknock agents, while also completely avoiding the use of toxic or carcinogenic substances, ensuring the environmentally friendly characteristics of the product from the source. In terms of process, this invention adopts mild reaction conditions, eliminating the need for high temperature, high pressure, or complex post-processing steps, which not only reduces energy consumption but also greatly simplifies the production process. This innovative solution not only effectively overcomes the environmental and safety bottlenecks of existing technologies but also provides a new technical path for developing next-generation high-performance environmentally friendly gasoline additives, possessing significant industrial application value and broad market prospects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an environmentally friendly gasoline antiknock agent and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing an environmentally friendly gasoline antiknock agent, comprising the following steps:

[0007] S1. At room temperature, first add propylene glycol methyl ether to the four-necked flask, start stirring and maintain a nitrogen atmosphere.

[0008] S2, then add 3,5-di-tert-butylphenylcarboran carboxylate and 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester, followed by polyisobutyleneamine, isobutyl acetate and dimethyl malonate, and continue stirring and mixing.

[0009] S3. Heat to 48-52℃, add 2,6-di-tert-butyl-p-cresol, and continue stirring; cool the reactants to room temperature and filter through a polytetrafluoroethylene membrane.

[0010] In this invention, the preparation of the anti-knock agent is a precise mixing process based on physical interactions. Its core mechanism lies in optimizing process parameters to achieve uniform dispersion and physical stability of multiple functional components at the molecular level, rather than generating new chemical bonds. The process begins with the selection of propylene glycol methyl ether as a universal solvent, whose excellent polarity and solubility lay the foundation for constructing a homogeneous system. Under inert gas protection, two core functional molecules—3,5-di-tert-butylphenylcarborane carboxylate and 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester—are first added. The stirring at this stage aims to utilize solvation to break the cohesive forces of the solid or highly viscous liquid, ensuring its complete dissolution and uniform dispersion in molecular form, creating preconditions for the subsequent synergistic anti-knock effect. Subsequently, auxiliary components such as polyisobutyleneamine, isobutyl acetate, and dimethyl malonate are introduced sequentially. The long-chain hydrocarbon groups of polyisobutyleneamine enhance the compatibility of the formulation with gasoline. Its amine groups may associate with other polar components through weak interactions such as hydrogen bonding, improving system stability. Isobutyl acetate and dimethyl malonate act as synergists and co-solvents, finely adjusting the polarity, viscosity, and volatility of the entire mixture to ensure that all components form a thermodynamically stable homogeneous liquid phase. Subsequent moderate heating and the addition of the antioxidant 2,6-di-tert-butyl-p-cresol aim to accelerate molecular diffusion, ensuring uniform distribution of antioxidant molecules. Its phenolic hydroxyl groups effectively quench peroxide free radicals, preventing the oxidation and deterioration of other active components during storage and guaranteeing long-term product performance. Final cooling and precision filtration are key quality control steps. Their mechanism is based on size exclusion, thoroughly removing trace amounts of insoluble particles that may have been introduced during preparation, ensuring the final product is clear, transparent, and homogeneous, meeting the application requirements of high-quality additives. The entire compounding process achieves optimal integration of multiple functional molecules at the physical level through precise feeding sequence, stirring intensity, and temperature control.

[0011] As a preferred embodiment of the present invention, in step S2, the stirring speed is 300-400 rpm.

[0012] As a preferred embodiment of the present invention, in step S3, the stirring time is 1-2 hours.

[0013] As a preferred embodiment of the present invention, the preparation method of the 3,5-di-tert-butylphenylcarboran carboxylic acid ester includes: A1, under argon protection, mixing orthogonal-carboran-1-carboxylic acid, 3,5-di-tert-butylphenol and anhydrous tetrahydrofuran, cooling to 0-5°C in an ice-water bath, and stirring; A2, then adding N,N'-dicyclohexylcarbodiimide, heating to 24-26°C, and stirring continuously; after the reaction is completed, removing the precipitate by suction filtration, concentrating the filtrate by rotary evaporation, and purifying it by silica gel column chromatography.

[0014] As a preferred embodiment of the present invention, the preparation steps of the orthogonal-carborane-1-carboxylic acid include: under an argon atmosphere, adding 10.0 g of orthogonal-carborane and 200 mL of anhydrous diethyl ether to a dry 500 mL three-necked flask, and cooling to 0°C in an ice-water bath; slowly adding 45.0 mL of a 2.5 M n-butyllithium hexane solution dropwise over 30 min, controlling the temperature below 5°C; after the addition is complete, removing the ice bath, raising the temperature to 25°C, and stirring continuously for 4 h; subsequently cooling the reaction system to... At -78℃, dry carbon dioxide gas was introduced into the vigorously stirred solution for 2 hours; the cold bath was removed and the reaction solution was slowly heated to 25℃ overnight; 50 mL of 1M hydrochloric acid solution was slowly added to quench the reaction, the organic layer was separated, and the aqueous phase was extracted with 2×50 mL of diethyl ether; the combined organic phases were washed with 50 mL of saturated brine, dried over anhydrous magnesium sulfate, filtered and concentrated to obtain the crude product; finally, the product was recrystallized from a mixed solvent of n-hexane and ethyl acetate to obtain white crystalline orthogonal-carborane-1-carboxylic acid.

[0015] In this invention, the core of the reaction of the 3,5-di-tert-butylphenylcarborane carboxylic acid ester lies in the activation of the carboxyl group by a dehydrating agent, followed by efficient condensation with the phenolic hydroxyl group. The starting material, orthogonal-carborane-1-carboxylic acid, possesses a unique boron-carbon cage structure, with its terminal carboxyl group serving as the reactive center. Under an inert atmosphere and low temperature, N,N'-dicyclohexylcarbodiimide first reacts with the carboxylic acid to generate a highly reactive O-acylisourea intermediate. This intermediate significantly enhances the electrophilicity of the carbonyl carbon, making it susceptible to nucleophilic attack. Excess 3,5-di-tert-butylphenol in the system, with its hydroxyl oxygen atom acting as a nucleophilic center, launches a nucleophilic attack on the activated carbonyl carbon, forming an unstable tetrahedral transition state. Subsequently, the dehydrating agent molecule departs as an insoluble urea derivative, shifting the reaction equilibrium to the right, ultimately forming a stable ester bond between the carboxylic acid and phenol to obtain the target product. The key to the success of the entire process lies in the effective capture and removal of the water generated in the reaction by the dehydrating agent. The highly sterically hindered structure of the product molecule, composed of a large tert-butyl group, not only ensures chemoselectivity during synthesis but also endows it with excellent thermal stability and antioxidant capacity. This is crucial for its use as a highly efficient free radical terminator in the high-temperature and high-pressure engine environment. Subsequent filtration and column chromatography purification aim to separate byproducts and obtain high-purity esters, providing core raw materials for the preparation of high-performance antiknock agents.

[0016] As a preferred embodiment of the present invention, in step A1, the mass ratio of orthogonal-carborane-1-carboxylic acid to 3,5-di-tert-butylphenol is 1:(2.5-3.0); the stirring time is 30-40 min.

[0017] As a preferred embodiment of the present invention, in step A2, the continuous stirring time is 16-20 hours.

[0018] As a preferred embodiment of the present invention, the preparation method of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid isooctyl ester includes: B1, under a dry nitrogen atmosphere, adding 1,2-oxoborin-4-carboxylic acid, toluene, and isooctyl alcohol to a three-necked flask, stirring to dissolve, and then adding N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine; heating to 108-112℃ and refluxing; after the reaction is completed, cooling to room temperature, filtering, washing with saturated brine, drying the organic phase with anhydrous magnesium sulfate, and filtering to obtain 1,2-oxoborin-4-carboxylic acid isooctyl ester. Crude product; B2, Dissolve crude 1,2-oxoborin-4-carboxylic acid isooctyl ester in anhydrous tetrahydrofuran, cool to -80~-70℃, add n-butyllithium dropwise, keep the temperature below -65℃, and continue stirring after the addition is complete; then add a solution of dicyclohexylphosphine chloride dissolved in tetrahydrofuran, and after the addition is complete, raise the temperature to 24-26℃ and continue stirring; after the reaction is complete, add saturated ammonium chloride solution to quench the reaction, separate the organic phase, extract the aqueous phase with ethyl acetate, combine the organic phases, dry with anhydrous sodium sulfate, filter, concentrate, and purify the crude product by silica gel column chromatography.

[0019] As a preferred embodiment of the present invention, the preparation steps of the 1,2-oxoborin-4-carboxylic acid are as follows: Under argon protection, 10.0 g of ethyl 4-oxobutyrate and 200 mL of anhydrous toluene are added to a dry 500 mL three-necked flask, along with 12.5 g of ethylene glycol and 0.5 g of p-toluenesulfonic acid. A Dean-Stark water separator is installed, and the mixture is heated to 110 °C and refluxed for 6 h until the water volume in the water separator no longer increases. After the reaction solution is cooled to 25 °C, it is washed with saturated sodium bicarbonate solution until neutral. The organic phase is dried over anhydrous magnesium sulfate, filtered, and concentrated to obtain crude ethyl 4,4-ethylenedioxybutyrate. The crude product is dissolved in 150 mL of... In a mixed solvent of methanol and 50 mL of water, the mixture was cooled to 0°C in an ice-water bath. 8.0 g of sodium hydroxide was added in portions, and the reaction was stirred for 2 hours while maintaining the temperature below 5°C. After the reaction was complete, methanol was removed under reduced pressure. The remaining aqueous phase was washed once with diethyl ether, acidified to pH 2 with concentrated hydrochloric acid in an ice-water bath, and extracted with 3 × 100 mL of ethyl acetate. The combined organic phases were washed with 100 mL of saturated brine, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain 4,4-ethylenedioxybutyric acid. Under nitrogen protection, 10.0 g of the above 4,4-ethylenedioxybutyric acid product and 150 mL of anhydrous tetrahydrofuran were added to a reaction flask, and the mixture was cooled to 0°C in an ice-water bath. 12.0 mL of pinacol borane was slowly added dropwise with stirring. After the addition was complete, the ice bath was removed, and the temperature was raised to 25°C with stirring for 4 hours. Subsequently, 100 mL of 1 M hydrochloric acid solution was added to the reaction mixture, and the mixture was stirred at 40°C for 2 hours to simultaneously achieve ketal deprotection and cyclization with the in-situ generated borate ester. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography, eluted with petroleum ether / ethyl acetate (volume ratio from 5:1 to 2:1), the target component was collected, and concentrated to obtain a high-purity white solid 1,2-oxoborin-4-carboxylic acid.

[0020] In this invention, the synthesis of isooctyl 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid is an octyl ester, a classic stepwise process for constructing complex molecules, involving two key mechanisms: esterification and nucleophilic substitution. The first step is a standard esterification reaction, designed to improve the oil solubility and reactivity of the starting material. Under the combined action of a dehydrating agent and a catalyst, the carboxyl group of 1,2-oxoborin-4-carboxylic acid undergoes dehydration condensation with the hydroxyl group of isooctyl alcohol. The dehydrating agent, by forming an active intermediate, lowers the reaction energy barrier, promoting ester bond formation to obtain isooctyl 1,2-oxoborin-4-carboxylic acid. This step provides a crucial precursor for subsequent reactions. The second step is a nucleophilic substitution reaction that constructs the core function of the molecule. Under ultra-low temperature and strict isolation from air and moisture, a strongly basic organolithium reagent selectively abstracts a proton from the α-position of the oxoborin ester heterocycle (relative to electron-withdrawing boron and carbonyl groups), generating a highly reactive carbanion. Due to the conjugated stabilizing effect of the adjacent heterocycle and carbonyl group, the nucleophilicity of this carbanion is enhanced and precisely confined to a specific carbon atom. Subsequently, this carbanion, acting as a strong nucleophile, attacks the positively charged phosphorus atom in the dicyclohexylphosphine chloride molecule. Upon attack, the phosphorus-chlorine bond undergoes heterolytic cleavage; the chloride ion, as a leaving group, leaves with an electron pair, while the carbanion donates an electron pair to form a new carbon-phosphine bond with the phosphorus atom, successfully introducing the dicyclohexylphosphine group into the molecular framework. This precise carbon-phosphine bond construction allows the final product to simultaneously combine the radical quenching ability of the boronin structure with the electron-donating properties of the phosphine group, resulting in a significant synergistic effect in the anti-explosion process.

[0021] As a preferred embodiment of the present invention, in step B1, the mass ratio of 1,2-oxoborin-4-carboxylic acid, toluene, isooctyl alcohol, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1:(8.0-9.5):(1.3-1.7):(1.6-1.9):(0.04-0.08); the reaction is heated to 108-112℃ and refluxed for 6-8 hours.

[0022] As a preferred embodiment of the present invention, in step B2, the stirring time is 1-2 hours after the addition is completed.

[0023] In a second aspect, the present invention provides an environmentally friendly gasoline antiknock agent prepared by the method described above, comprising the following raw materials in parts by weight: 15-25 parts of 3,5-di-tert-butylphenylcarboran carboxylate; 10-20 parts of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester; 5-10 parts of polyisobutyleneamine; 15-25 parts of isobutyl acetate; 8-12 parts of dimethyl malonate; 2-4 parts of 2,6-di-tert-butyl-p-cresol; and 20-30 parts of propylene glycol methyl ether.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The environmentally friendly gasoline antiknock agent and its preparation method provided by this invention exhibit significant advantages over existing technologies in multiple dimensions. First, its core advantage lies in achieving a perfect balance between high-efficiency antiknock performance and environmental friendliness. The antiknock agent system designed by this invention completely eliminates any metal elements, fundamentally eliminating the toxic environmental pollution and engine aftertreatment system poisoning risks brought about by traditional lead- or manganese-containing antiknock agents. The key active components in the product, such as bis-tert-butylphenylcarboroline carboxylate and isooctyl phosphonoboryl phosphate, are organic molecules composed of elements such as boron, phosphorus, oxygen, carbon, and hydrogen. They can achieve complete and clean combustion in the engine, and the final products are harmless gas and water, without producing any solid particulate matter or persistent toxic residues, which highly meets the strict requirements of modern society for green chemistry and clean energy. At the same time, through the precise formulation of its components, this anti-knock agent produces an excellent synergistic anti-knock effect, which can significantly increase the octane number of the base gasoline, effectively suppress the knocking phenomenon that may occur in the engine under various operating conditions, thereby ensuring that the engine power is released smoothly and fully, and helping to improve fuel economy and extend the service life of the engine.

[0026] (2) The technical effect of this invention is reflected in its unique molecular structure design and the synergistic mechanism of the composite formulation. The bis-tert-butylphenyl carboroline carboxylate used has a unique cage-like structure composed of boron atoms in its molecular core. This structure has extremely high thermal and chemical stability, while the large tert-butylphenyl group on the periphery provides a huge steric hindrance effect. This not only further enhances the stability of the molecule itself, but also makes it a highly efficient free radical scavenger, which can effectively interrupt the chain reaction that leads to detonation during combustion. The other phosphooxyboronyl carboxylate isooctyl ester is a composite functional molecule that integrates a phosphine center and a boron-oxygen heterocycle. The phosphine atom has a strong electron-donating ability and can interact with combustion intermediates to change the reaction pathway; its boron-oxygen ring structure has excellent quenching ability for free radicals. These two core components complement each other in function and work together to achieve a synergistic effect that is far beyond what can be achieved by simple superposition. In addition, the polyisobutyleneamine added to the formula has good cleaning and dispersing effects, which can prevent the formation of deposits in the intake and valves; dimethyl malonate and other components further optimize the solubility and anti-explosion synergy of the whole system, together constructing a highly efficient and stable metal-free anti-explosion system.

[0027] (3) This invention also achieves excellent technical results in terms of the preparation process and the overall performance of the final product. The preparation method involved, from the synthesis of key intermediates to the compounding of the final product, has a scientific and reasonable process flow design and precise and rigorous condition control. For example, in the preparation of key intermediates, a series of methods such as low-temperature reaction, inert gas protection, and column chromatography purification are used to ensure the high purity and high quality of the intermediates, laying a solid foundation for the excellent performance of the final product. In the final compounding stage, a specific solvent system is used to mix the components at a mild temperature. By controlling the stirring speed and time, it is ensured that up to seven components can be fully and uniformly miscible to form a uniform and stable liquid phase product, avoiding the stratification or precipitation that may occur during storage or use. Strict filtration steps further ensure the cleanliness and reliability of the product. The final antiknock agent product not only has high antiknock efficiency and is environmentally friendly and non-toxic, but also has excellent storage stability and good compatibility with various gasoline components. It is easy to use and can be directly added without any modification to existing storage and transportation equipment and engines, and has huge market application potential and promotion value. Detailed Implementation

[0028] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0029] The sources of some components in the examples and comparative examples are as follows:

[0030] The propylene glycol methyl ether was purchased from Jiangsu Hualun Chemical Co., Ltd.

[0031] The polyisobutyleneamine was purchased from Shandong Huifeng Petrochemical Group Co., Ltd.

[0032] The isobutyl acetate was purchased from Jiangsu Baichuan High-Tech New Materials Co., Ltd.

[0033] The dimethyl malonate was purchased from Shandong Weichuan Fine Chemical Co., Ltd.

[0034] The 2,6-di-tert-butyl-p-cresol was purchased from Nanjing Shuguang Chemical Group Co., Ltd.

[0035] The 3,5-di-tert-butylphenol was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0036] The N,N'-dicyclohexylcarbodiimide was purchased from Shanghai Titan Technology Co., Ltd.

[0037] The toluene was purchased from China Petroleum & Chemical Corporation (Sinopec).

[0038] The isooctyl alcohol was purchased from China National Petroleum Corporation.

[0039] The 4-dimethylaminopyridine was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0040] The dicyclohexylphosphine chloride was purchased from Beijing Bailingwei Technology Co., Ltd.

[0041] Preparation Example 1

[0042] A method for preparing orthogonal-carborane-1-carboxylic acid is provided, comprising the following steps: under an argon atmosphere, 10.0 g of orthogonal-carborane and 200 mL of anhydrous diethyl ether are added to a dry 500 mL three-necked flask, and the flask is cooled to 0 °C in an ice-water bath; 45.0 mL of a 2.5 M n-butyllithium hexane solution is slowly added dropwise over 30 min, while maintaining the temperature below 5 °C; after the addition is complete, the ice bath is removed, and the temperature is raised to 25 °C and stirred continuously for 4 h; subsequently, the reaction system is cooled to -78 °C, and dry carbon dioxide gas is introduced into the vigorously stirred solution for 2 h; the cold bath is removed, and the reaction solution is slowly heated to 25 °C overnight; the reaction is quenched by slowly adding 50 mL of a 1 M hydrochloric acid solution, the organic layer is separated, and the aqueous phase is extracted with 2 × 50 mL of diethyl ether; the combined organic phases are washed with 50 mL of saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated to obtain the crude product; finally, the product is recrystallized from a mixed solvent of n-hexane and ethyl acetate to obtain white crystalline orthogonal-carborane-1-carboxylic acid.

[0043] Preparation Example 2

[0044] A method for preparing 1,2-oxoborin-4-carboxylic acid is provided, comprising the following steps: Under argon protection, 10.0 g of ethyl 4-oxobutyrate and 200 mL of anhydrous toluene are added to a dry 500 mL three-necked flask, along with 12.5 g of ethylene glycol and 0.5 g of p-toluenesulfonic acid. A Dean-Stark water separator is installed, and the mixture is heated to 110 °C and refluxed for 6 h until the water volume in the separator no longer increases. After the reaction solution is cooled to 25 °C, it is washed with saturated sodium bicarbonate solution until neutral. The organic phase is dried over anhydrous magnesium sulfate, filtered, and concentrated to obtain crude ethyl 4,4-ethylenedioxybutyrate. The crude product is dissolved in 150 mL of methanol and... In a mixed solvent of 50 mL water, the mixture was cooled to 0 °C in an ice-water bath. 8.0 g of sodium hydroxide was added in portions, and the reaction was stirred for 2 h while maintaining the temperature below 5 °C. After the reaction was complete, methanol was removed under reduced pressure. The remaining aqueous phase was washed once with diethyl ether, acidified to pH 2 with concentrated hydrochloric acid in an ice-water bath, and extracted with 3 × 100 mL of ethyl acetate. The combined organic phases were washed with 100 mL of saturated brine, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain 4,4-ethylenedioxybutyric acid. Under nitrogen protection, 10.0 g of the above 4,4-ethylenedioxybutyric acid product and 150 mL of anhydrous tetrahydrofuran were added to a reaction flask, and the mixture was cooled to 0 °C in an ice-water bath. 12.0 mL of pinacol borane was slowly added dropwise with stirring. After the addition was complete, the ice bath was removed, and the temperature was raised to 25 °C with stirring for 4 h. Subsequently, 100 mL of 1 M hydrochloric acid solution was added to the reaction mixture, and the mixture was stirred at 40 °C for 2 h to simultaneously achieve ketal deprotection and cyclization with the in-situ generated borate ester. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate. The organic phases were combined, dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. Finally, the crude product was purified by silica gel column chromatography, eluted with petroleum ether / ethyl acetate (volume ratio from 5:1 to 2:1), the target component was collected, and concentrated to obtain a high-purity white solid 1,2-oxoborin-4-carboxylic acid.

[0045] Example 1

[0046] This embodiment provides a method for preparing an environmentally friendly gasoline antiknock agent, comprising the following steps: Preparation of 3,5-di-tert-butylphenylcarborane carboxylic acid ester: Under argon protection, 10.0 g of orthogonal-carborane-1-carboxylic acid, 28.5 g of 3,5-di-tert-butylphenol, and 150 mL of anhydrous tetrahydrofuran are added to a dry four-necked flask. The mixture is placed in an ice-water bath and cooled to 3°C, and stirring is started and continued for 35 min. Then, 18.0 g of N,N'-dicyclohexylcarbodiimide is added under continuous stirring. The ice-water bath is removed, and the reaction system is allowed to naturally heat to 25°C, and stirring is continued at this temperature for 18 h. After the reaction is completed, the white precipitate generated in the reaction solution is removed by vacuum filtration. The obtained filtrate is subjected to rotary evaporation to remove most of the tetrahydrofuran solvent, yielding a concentrate. The concentrate was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate in a volume ratio of 10:1 as the eluent. The target component was collected, and the solvent was removed by rotary evaporation to obtain 3,5-di-tert-butylphenylcarboran carboxylic acid ester.

[0047] Preparation of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid isooctyl ester: Under a dry nitrogen atmosphere, 8.0 g of 1,2-oxoborin-4-carboxylic acid, 80 mL of toluene, and 12.0 g of isooctyl alcohol were added to a three-necked flask. After stirring and dissolving, 14.0 g of N,N'-dicyclohexylcarbodiimide and 0.5 g of 4-dimethylaminopyridine were added sequentially. The reaction mixture was heated to 110 °C and refluxed for 7 h. After the reaction was complete, the mixture was cooled to room temperature, and insoluble matter was removed by filtration. The filtrate was washed three times with 50 mL of saturated brine each time. The organic phase was dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated to obtain crude 1,2-oxoborin-4-carboxylic acid isooctyl ester. The crude product was dissolved in 100 mL of anhydrous tetrahydrofuran, and the solution was cooled to -75 °C. At this low temperature, a hexane solution of n-butyllithium was slowly added dropwise, keeping the temperature of the reaction system below -65 °C during the addition. After the addition was complete, the mixture was stirred at -75°C for 1.5 h. Then, 12.0 g of dicyclohexylphosphine chloride dissolved in 50 mL of tetrahydrofuran was slowly added dropwise. After the addition was complete, the reaction system was allowed to naturally warm to 25°C and stirred at this temperature for 16 h. After the reaction was complete, 100 mL of saturated ammonium chloride solution was added to quench the reaction. The organic phase was separated, and the aqueous phase was extracted three times with 50 mL of ethyl acetate each time. All organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated to obtain the crude product. The crude product was purified by silica gel column chromatography using a 15:1 (v / v) mixture of petroleum ether and ethyl acetate as eluent. The target fraction was collected, and the solvent was removed by rotary evaporation to obtain isooctyl 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid.

[0048] Preparation of environmentally friendly gasoline antiknock agent: Under room temperature conditions, 250g of propylene glycol methyl ether was first added to a four-necked flask, and stirring was started while maintaining a nitrogen atmosphere. Then, 200g of the previously prepared 3,5-di-tert-butylphenylcarboran carboxylate and 150g of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester were added, followed by 75g of polyisobutyleneamine, 200g of isobutyl acetate, and 100g of dimethyl malonate, and the mixture was stirred continuously at 350 rpm for 1 hour. After that, the temperature was raised to 50°C, and 30g of 2,6-di-tert-butyl-p-cresol was added, and stirring was continued for 1.5 hours. Finally, the reaction mixture was cooled to room temperature and filtered through a polytetrafluoroethylene filter membrane to obtain a clear and transparent environmentally friendly gasoline antiknock agent product. In this embodiment, the orthogonal-carboran-1-carboxylic acid and 1,2-oxoborin-4-carboxylic acid were the substances obtained in Preparation Examples 1-2.

[0049] Example 2

[0050] The difference between this embodiment and Example 1 is that this embodiment provides a method for preparing an environmentally friendly gasoline antiknock agent, including the following steps: Preparation of 3,5-di-tert-butylphenylcarboran carboxylic acid ester: Under argon protection, 10.0 g of orthogonal-carboran-1-carboxylic acid, 25.0 g of 3,5-di-tert-butylphenol, and 140 mL of anhydrous tetrahydrofuran are added to a dry four-necked flask. The mixture is placed in an ice-water bath and cooled to 2°C, and stirring is started and continued for 32 min. Then, 16.5 g of N,N'-dicyclohexylcarbodiimide is added. The ice-water bath is removed, the temperature is raised to 25°C, and stirring is continued for 17 h. After the reaction is completed, the mixture is filtered, and the filtrate is concentrated and purified by silica gel column chromatography to obtain the target product.

[0051] Preparation of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid isooctyl ester: Under a dry nitrogen atmosphere, 8.0 g of 1,2-oxoborin-4-carboxylic acid, 75 mL of toluene, and 11.0 g of isooctyl alcohol were added to a three-necked flask. After stirring and dissolving, 13.0 g of N,N'-dicyclohexylcarbodiimide and 0.4 g of 4-dimethylaminopyridine were added. The mixture was heated to 109 °C and refluxed for 6.5 h. After cooling, the crude product was obtained and dissolved in 90 mL of anhydrous tetrahydrofuran. The solution was cooled to -78 °C. Butyllithium was added dropwise, maintaining the temperature below -65 °C, and stirring was continued for 1.2 h after the addition was complete. A solution of 11.0 g of dicyclohexylphosphine chloride in tetrahydrofuran was added dropwise, and the mixture was heated to 25 °C and stirred for 15 h. After quenching, the crude product was purified by silica gel column chromatography to obtain the target product.

[0052] Preparation of environmentally friendly gasoline antiknock agent: At room temperature, 220g of propylene glycol methyl ether was first added to a four-necked flask and stirred under nitrogen protection. Then, 180g of the previously prepared 3,5-di-tert-butylphenylcarboran carboxylate and 130g of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester were added, followed by 65g of polyisobutyleneamine, 180g of isobutyl acetate, and 90g of dimethyl malonate, and stirred at 330 rpm for 55 min. The temperature was raised to 49℃, and 25g of 2,6-di-tert-butyl-p-cresol was added, with stirring continuing for 1.2 h. After cooling to room temperature, the product was obtained by filtration through a polytetrafluoroethylene filter membrane.

[0053] Example 3

[0054] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing an environmentally friendly gasoline antiknock agent, including the following steps: Preparation of 3,5-di-tert-butylphenylcarborane carboxylic acid ester: Under argon protection, 10.0 g of orthogonal-carborane-1-carboxylic acid, 30.0 g of 3,5-di-tert-butylphenol, and 160 mL of anhydrous tetrahydrofuran are added to a dry four-necked flask. The mixture is placed in an ice-water bath and cooled to 4°C, and stirring is started and continued for 38 min. Then, 19.0 g of N,N'-dicyclohexylcarbodiimide is added. The ice-water bath is removed, the temperature is raised to 25°C, and stirring is continued for 19 h. After the reaction is completed, the mixture is filtered, and the filtrate is concentrated and purified by silica gel column chromatography to obtain the target product.

[0055] Preparation of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid isooctyl ester: Under a dry nitrogen atmosphere, 8.0 g of 1,2-oxoborin-4-carboxylic acid, 85 mL of toluene, and 13.0 g of isooctyl alcohol were added to a three-necked flask. After stirring and dissolving, 15.0 g of N,N'-dicyclohexylcarbodiimide and 0.6 g of 4-dimethylaminopyridine were added. The mixture was heated to 111 °C and refluxed for 7.5 h. After cooling, the crude product was obtained and dissolved in 110 mL of anhydrous tetrahydrofuran. The solution was cooled to -72 °C. Butyllithium was added dropwise, maintaining the temperature below -65 °C, and the mixture was stirred for 1.8 h after the addition was complete. A solution of 13.0 g of dicyclohexylphosphine chloride in tetrahydrofuran was added dropwise, and the mixture was heated to 25 °C and stirred for 17 h. After quenching, the crude product was purified by silica gel column chromatography to obtain the target product.

[0056] Preparation of environmentally friendly gasoline antiknock agent: At room temperature, 280g of propylene glycol methyl ether was first added to a four-necked flask and stirred under nitrogen protection. Then, 220g of the previously prepared 3,5-di-tert-butylphenylcarboran carboxylate and 170g of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester were added, followed by 85g of polyisobutyleneamine, 220g of isobutyl acetate, and 110g of dimethyl malonate, and stirred at 370 rpm for 65 min. The temperature was raised to 51℃, and 35g of 2,6-di-tert-butyl-p-cresol was added, with stirring continuing for 1.8 h. After cooling to room temperature, the product was obtained by filtration through a polytetrafluoroethylene (PTFE) membrane.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 lies in the preparation of the environmentally friendly gasoline antiknock agent: At room temperature, 250g of propylene glycol methyl ether was first added to a four-necked flask, and stirring was started while maintaining a nitrogen atmosphere. Then, 150g of 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylic acid isooctyl ester was added, followed by 75g of polyisobutyleneamine, 200g of isobutyl acetate, and 100g of dimethyl malonate, and the mixture was stirred continuously at 350 rpm for 1 hour. Afterward, the temperature was raised to 50°C, and 30g of 2,6-di-tert-butyl-p-cresol was added, with stirring continuing for 1.5 hours. Finally, the reaction mixture was cooled to room temperature and filtered through a polytetrafluoroethylene (PTFE) membrane to obtain the product.

[0059] Comparative Example 2

[0060] The difference between this comparative example and Example 1 lies in the preparation of the environmentally friendly gasoline antiknock agent: At room temperature, 250g of propylene glycol methyl ether was first added to a four-necked flask, and stirring was started while maintaining a nitrogen atmosphere. Then, 200g of 3,5-di-tert-butylphenylcarboran carboxylate was added, followed by 75g of polyisobutyleneamine, 200g of isobutyl acetate, and 100g of dimethyl malonate, and the mixture was stirred continuously at 350 rpm for 1 hour. Afterward, the temperature was raised to 50°C, and 30g of 2,6-di-tert-butyl-p-cresol was added, with stirring continuing for 1.5 hours. Finally, the reaction mixture was cooled to room temperature and filtered through a polytetrafluoroethylene (PTFE) membrane to obtain the product.

[0061] Comparative Example 3

[0062] The difference between this comparative example and Example 1 lies in the preparation of the environmentally friendly gasoline antiknock agent: At room temperature, 250g of propylene glycol methyl ether was first added to a four-necked flask, stirred, and a nitrogen atmosphere was maintained. Then, 75g of polyisobutyleneamine, 200g of isobutyl acetate, and 100g of dimethyl malonate were added sequentially, and the mixture was stirred continuously at 350 rpm for 1 hour. Afterward, the temperature was raised to 50°C, and 30g of 2,6-di-tert-butyl-p-cresol was added, with stirring continuing for 1.5 hours. Finally, the reactants were cooled to room temperature and filtered through a polytetrafluoroethylene (PTFE) membrane to obtain the product.

[0063] The performance of the environmentally friendly gasoline antiknock agents obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to national and industry standard testing specifications. The gasoline antiknock agent samples prepared in the examples and comparative examples were accurately weighed at a mass addition rate of 0.5%, and added to the same batch of commercially available 92-octane clean gasoline with a basic research octane number of 90.0. The mixture was stirred for 30 minutes at a mechanical stirrer at a rate of 500 rpm to ensure thorough and uniform mixing of the antiknock agent and gasoline.

[0064] The determination of gasoline octane number is carried out on a standard octane number testing machine. First, the research octane number (standard number: GB / T 5487-2015, standard name: determination of gasoline octane number by research method) is determined. The sample oil is injected into a carburetor engine and continuously operated through a variable compression ratio combustion chamber at a low speed of 600 rpm. The compression ratio is gradually increased until knocking of standard intensity is detected. The knocking intensity is compared with that of a reference fuel with a known octane number under the same conditions, thereby accurately calculating the research octane number and increment of the sample.

[0065] Subsequently, the motor octane number (standard number: GB / T 503-2016, standard name: determination of gasoline octane number by motor method) was determined using the same testing machine, but the engine speed was increased to 900 rpm and the intake temperature of the air-fuel mixture was increased to 150°C. The same principle was applied under more stringent load conditions, and the anti-knock index was calculated. High-temperature anti-knock performance testing was conducted on a dedicated high-temperature simulation bench, where specific engine components were heated to 150°C and operated stably. The relative index of its anti-knock capability was evaluated under this high-temperature condition.

[0066] The sulfur content (standard name: determination of total sulfur content in light hydrocarbons, engine fuels and other petroleum products by ultraviolet fluorescence method; standard number: GB / T 34100-2017) is determined using a wavelength dispersive X-ray fluorescence spectrometer. The sample is placed in a special test cup and excited by an X-ray beam in a vacuum environment. The intensity of the characteristic spectral lines of sulfur is measured, and the sulfur content in the sample is calculated using a preset standard curve.

[0067] Storage stability test (standard name: determination of oxidation stability of gasoline by induction period method; standard number: GB / T8018-2015) involves dispensing each well-mixed gasoline sample into a 100mL transparent stoppered glass bottle, filling it with nitrogen, sealing it, and storing it in a constant temperature and light-proof environment at 25℃ for 30 days. After the storage period, the sample is removed and visually observed under natural light to check for turbidity, layering, or precipitation, and the specific conditions are recorded.

[0068] The performance test data above are shown in Table 1.

[0069] Table 1 Performance Test Results

[0070]

[0071] The test results in Table 1 clearly show that Examples 1-3, by simultaneously containing two key modified compounds—3,5-di-tert-butylphenylcarboran carboxylate and 2-(dicyclohexylphosphino)-1,2-oxoborin-4-carboxylate isooctyl ester—successfully solved the technical problem that this invention aimed to overcome. Regarding improved anti-knock performance, Examples 1-3 showed a research octane number increase of 5.2-5.8 units and an anti-knock index exceeding 94.30, significantly better than Comparative Examples 1-3. Specifically, Comparative Example 1, containing only phosphonooxoborin ester and lacking carboran carboxylate, had an octane number increase of only 2.5 units; Comparative Example 2, containing only carboran carboxylate and lacking phosphonooxoborin ester, also had an increase of only 3.1 units; while Comparative Example 3, lacking both key components, had the worst performance, with an increase of only 1.2 units. This fully demonstrates that the two compounds produced a crucial synergistic effect in improving the octane number, and neither can be omitted. Regarding high-temperature anti-knock performance, the relative indices of Examples 1-3 were as high as 128-132, far exceeding those of Comparative Example 1 (112), Comparative Example 2 (115), and Comparative Example 3 (103), indicating that the combined use of the two components endowed the anti-knock agent with the ability to maintain high efficiency under harsh engine conditions. In addressing the technical issue of storage stability, Examples 1-3 remained clear and transparent without any sediment after thirty days of storage, while Comparative Example 1 showed slight flocculent matter due to an unbalanced formulation, and Comparative Example 3 produced a large amount of sediment due to the complete absence of the core stabilizing component. This demonstrates the significant advantages of the composite system of the present invention in maintaining product homogeneity and long-term stability. In summary, the technical solutions provided by Examples 1-3 effectively achieve the comprehensive goals of improving gasoline anti-knock performance, ensuring high-temperature effectiveness, and maintaining long-term storage stability, successfully solving the technical bottlenecks of insufficient efficacy, high-temperature performance degradation, and easy decomposition during storage in existing single-component metal-free anti-knock agents.

Claims

1. A process for the preparation of an environmentally friendly gasoline antiknock agent, characterized by the steps of The application relates to a preparation method of 3,5-di-tert-butylphenyl carborane carboxylate. S1, 20-30 parts of propylene glycol methyl ether is added into a four-necked flask under room temperature, stirring is started and a nitrogen atmosphere is maintained; S2, then 15-25 parts of 3,5-di-tert-butylphenyl carborane carboxylate and 10-20 parts of 2-(dicyclohexylphosphino)-1,2-oxaborinine-4-carboxylic acid iso-octyl ester are added, and then 5-10 parts of polyisobutylene amine, 15-25 parts of isobutyl acetate and 8-12 parts of dimethyl malonate are added in sequence, and mixing is continuously carried out; S3, the temperature is increased to 48-52 DEG C, 2-4 parts of 2,6-di-tert-butyl-p-cresol is added, and stirring is continuously carried out; the reaction is cooled to room temperature, and is filtered through a polytetrafluoroethylene filter membrane.

2. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 1, characterized in that, In step S2, the stirring speed is 300-400 rpm.

3. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 1, characterized in that, In step S3, the stirring time is 1-2 h.

4. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 1, characterized in that, The preparation method of the 3,5-di-tert-butylphenyl carborane carboxylate comprises the following steps: A1, under argon protection, ortho-carborane-1-carboxylic acid, 3,5-di-tert-butylphenol and anhydrous tetrahydrofuran are mixed, and stirring is carried out after being cooled to 0-5 DEG C through an ice water bath; A2, then N,N'-dicyclohexyl carbodiimide is added, the temperature is increased to 24-26 DEG C, and stirring is continuously carried out; after the reaction is completed, the precipitate is removed through suction filtration, the filtrate is concentrated through rotary evaporation, and then is purified through silica gel column chromatography.

5. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 4, characterized in that, In step A1, the mass ratio of ortho-carborane-1-carboxylic acid to 3,5-di-tert-butylphenol is 1:(2.5-3.0), and the stirring time is 30-40 min.

6. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 4, characterized in that, In step A2, the continuous stirring time is 16-20 h.

7. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 1, characterized in that, The preparation method of the 2-(dicyclohexylphosphino)-1,2-oxaborinine-4-carboxylic acid iso-octyl ester comprises the following steps: B1, under a dry nitrogen atmosphere, 1,2-oxaborinine-4-carboxylic acid, toluene and iso-octanol are added into a three-necked flask, are dissolved through stirring, and then N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine are added; heating is carried out to 108-112 DEG C to reflux the reaction; after the reaction is completed, the temperature is cooled to room temperature, suction filtration is carried out, the organic phase is dried through anhydrous magnesium sulfate, and then is filtered to obtain 1,2-oxaborinine-4-carboxylic acid iso-octyl ester crude product; B2, the 1,2-oxaborinine-4-carboxylic acid iso-octyl ester crude product is dissolved in anhydrous tetrahydrofuran, is cooled to-80~-70 DEG C, and then normal butyl lithium is added dropwise, and the temperature is kept below-65 DEG C; after the dropwise addition is completed, stirring is continuously carried out; then a dicyclohexyl phosphine chloride solution in tetrahydrofuran is added dropwise, after the dropwise addition is completed, the temperature is increased to 24-26 DEG C, and stirring is continuously carried out; after the reaction is completed, saturated ammonium chloride solution is added to quench the reaction, the organic phase is separated, the water phase is extracted with ethyl acetate, the combined organic phases are dried through anhydrous sodium sulfate, and then are filtered and concentrated to obtain a crude product, and the crude product is purified through silica gel column chromatography.

8. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 7, characterized in that, In step B1, the mass ratio of 1,2-oxaborinine-4-carboxylic acid, toluene, iso-octanol, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine is 1:(8.0-9.5):(1.3-1.7):(1.6-1.9):(0.04-0.08), and the reflux reaction time is 6-8 h.

9. The preparation method of the environmentally friendly gasoline antiknock agent according to claim 7, characterized in that, In Step B2, the time for continued stirring after the dropwise addition is complete is 1-2 h.

10. An environmentally friendly anti-knock agent for gasoline prepared by the method according to any one of claims 1 to 9, characterized by, The raw materials include the following weight parts: 3,5-di-tert-butylphenylcarbodiimide 15-25 parts; 2-(dicyclohexylphosphino)-1,2-oxaborin-4-carboxylic acid iso-octyl ester 10-20 parts; polyisobutylene amine 5-10 parts; iso-butyl acetate 15-25 parts; dimethyl malonate 8-12 parts; 2,6-di-tert-butyl-p-cresol 2-4 parts; propylene glycol methyl ether 20-30 parts. The raw materials include the following weight parts: 3,5-di-tert-butylphenylcarbodiimide 15-25 parts; 2-(dicyclohexylphosphino)-1,2-oxaborin-4-carboxylic acid iso-octyl ester 10-20 parts; polyisobutylene amine 5-10 parts; iso-butyl acetate 15-25 parts; dimethyl malonate 8-12 parts; 2,6-di-tert-butyl-p-cresol 2-4 parts; propylene glycol methyl ether 20-30 parts.

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