Vanillyl octyl ester, its preparation method and application

Abstract

The application discloses vanillyl octyl ester, a preparation method and application thereof, and relates to the field of insulating oil additives. Vanillyl acid and n-octanol are subjected to esterification under the action of a biological enzyme catalyst to synthesize vanillyl octyl ester, and the synthesis method is efficient, green, environmentally friendly and low in cost. The prepared vanillyl octyl ester is added into synthetic ester insulating oil as an antioxidant active ingredient, the long ester chain in the vanillyl octyl ester has high thermal stability, can effectively inhibit the oxidation of the synthetic ester insulating oil at high temperature, and has good compatibility with the synthetic ester insulating oil. Therefore, compared with traditional antioxidants, the vanillyl octyl ester has significant advantages in maintaining excellent antioxidant properties and electrical properties of the synthetic ester insulating oil.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of insulating oil additives, in particular to a vanillic acid octyl ester, a preparation method and application thereof. BACKGROUND

[0002] With the increasing complexity of the operating conditions of power equipment, especially under high temperature, high pressure and long time operation conditions, the performance of insulating oil is crucial to the safe and stable operation of the equipment. Traditional mineral oil is gradually replaced by synthetic ester insulating oil due to its non-renewability and high environmental pollution risk. Synthetic ester insulating oil has become an ideal substitute for mineral oil in power equipment due to its excellent environmental performance, high flash point and good electrical insulation performance. However, synthetic ester insulating oil is prone to oxidation under long time high temperature conditions, generating acidic substances and sludge, which leads to a decrease in insulation performance and further affects the safe operation of power equipment.

[0003] Currently, antioxidant technology is considered the most economical and effective means to improve the antioxidant performance of synthetic ester insulating oil. Antioxidants can capture free radicals generated during the oxidation process, decompose peroxides or terminate free radical chain reactions, prevent the continuous progress of oxidation reactions, and reduce the generation of oxidation by-products, thereby maintaining the stability of the performance of insulating oil under long time high temperature operation conditions.

[0004] Common antioxidants on the market, such as 2,6-di-tert-butyl-p-cresol (BHT), can delay the oxidation process, but their antioxidant effect is limited and has a great impact on the dielectric properties of insulating oil. In addition, traditional antioxidants are mostly synthetic compounds, which can cause environmental pollution during use and are difficult to meet the increasingly stringent environmental requirements. Therefore, it is urgent to develop a more efficient and environmentally friendly antioxidant to improve the antioxidant performance of synthetic ester insulating oil while maintaining its excellent electrical performance. SUMMARY

[0005] The present application provides a vanillic acid octyl ester, a preparation method and application thereof. By adding vanillic acid octyl ester to synthetic ester insulating oil, the antioxidant performance is improved, and the impact on electrical performance is reduced, which can maintain excellent comprehensive performance.

[0006] To solve the above technical problems, one of the purposes of the present application provides a vanillic acid octyl ester, the chemical structural formula of which is: .

[0007] To solve the above technical problems, the second purpose of the present application provides a preparation method of vanillic acid octyl ester, comprising the following steps:

[0008] (1) adding vanillic acid and n-octanol into a container, adding a biological enzyme catalyst and molecular sieves, and performing esterification reaction to obtain a reaction product;

[0009] (2) adding adsorbent in the reaction product, stirring to remove impurities and pigments in the reaction process, filtering, then extracting the solution, removing organic solvent by rotary evaporation, and then purifying by column chromatography to obtain octyl vanillate.

[0010] As a preferred solution, in step (1), the molar ratio of vanillic acid to n-octanol is 1: (1.5-2).

[0011] As a preferred solution, in step (1), the molecular sieve is 4A molecular sieve, and the molecular sieve is 2wt%-4wt% of the total mass of vanillic acid and n-octanol.

[0012] As a preferred solution, in step (1), the biological enzyme catalyst is 5wt%-8wt% of the total mass of vanillic acid and n-octanol.

[0013] As a preferred solution, in step (2), the adsorbent includes activated carbon, silica gel and basic alumina with a mass ratio of 1:1: (1-2), and the adsorbent accounts for 5-10wt% of the total mass of the reaction system.

[0014] As a preferred solution, the biological enzyme catalyst is at least one of immobilized lipase 435, lipase acrylic resin, bacillus licheniformis lipase, bacillus subtilis lipase, bacillus licheniformis lipase, and pseudomonas lipase.

[0015] As a preferred solution, in step (1), the esterification reaction process adopts a step-by-step adjustment of vacuum degree method, and the initial vacuum degree is controlled at-0.02Mpa~-0.05Mpa, and decreases by 0.01Mpa per hour.

[0016] As a preferred solution, in step (1), the esterification reaction process controls the temperature to be 40-60℃, and the time to be 6-8 h.

[0017] As a preferred solution, in step (1), the esterification reaction process controls the stirring rate to be 150-300 rpm.

[0018] As a preferred solution, in step (2), the stirring temperature after adding the adsorbent is 40-60℃, and the stirring time is 30-60 min.

[0019] As a preferred solution, in step (2), the solution is extracted with ethyl acetate.

[0020] As a preferred solution, in step (2), silica gel is used as the stationary phase in the column chromatography purification process.

[0021] In order to solve the above technical problems, the third object of the present application provides an application of octyl vanillate in the field of preparing synthetic ester insulating oil.

[0022] To solve the above technical problems, the fourth object of the present application provides a synthetic ester insulating oil containing 0.1wt%-1wt% octyl vanillate.

[0023] As a preferred solution, 0.1wt%-1wt% octyl vanillate, 90-99.9wt% insulating oil base and 0wt%-9wt% functional additives, which are at least one of preservatives, antifoaming agents and antiemulsifying agents, are included, and the insulating oil base is TMP triester insulating oil or PETP tetraester insulating oil.

[0024] The present application adds octyl vanillate as an antioxidant active ingredient to the synthetic ester insulating oil. Since octyl vanillate contains a medium-long chain ester group structure, it increases the molecular weight of vanillic acid and enhances its thermal stability. Under high temperature conditions, the long chain structure is not easy to decompose, so it can effectively capture free radicals generated in the oxidation process of synthetic ester insulating oil, inhibit the oxidation reaction, significantly increase the initial oxidation temperature of synthetic ester insulating oil in oxygen and air atmosphere, effectively inhibit the oxidation of oil at high temperature, and improve the antioxidant capacity. The medium-long ester chain molecular structure of octyl vanillate also helps to improve its good solubility in synthetic ester insulating oil, has good compatibility, can reduce the influence on the dielectric loss, volume resistivity and AC breakdown voltage of synthetic ester insulating oil, can maintain excellent electrical performance, and meet the application requirements.

[0025] To solve the above technical problems, the fifth object of the present application provides a preparation method of synthetic ester insulating oil, comprising the following steps: adding octyl vanillate and functional additives to the insulating oil base by ultrasonic dispersion method, the temperature is 40-60℃, the stirring time is 1-3 hours, and then drying at 80-120℃ in a vacuum environment for 24-48 hours to obtain synthetic ester insulating oil.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The medium-long ester chain of the octyl vanillate provided by the present application has higher thermal stability, which can improve the oxidation stability of synthetic ester insulating oil in high temperature environment, and the octyl vanillate has good compatibility with synthetic ester insulating oil, which helps to maintain the synthetic ester insulating oil with higher volume resistivity and AC breakdown voltage and lower dielectric loss factor. Compared with traditional antioxidants, it has significant advantages in maintaining excellent antioxidant performance and electrical performance of synthetic ester insulating oil.

[0028] 2. The octyl vanillate is synthesized based on the biological enzyme catalysis method, which has the characteristics of high efficiency, environmental protection and low cost. The prepared octyl vanillate has high purity and good high temperature antioxidant capacity, realizing the full greenization of the preparation of insulating oil. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Figure 1 is an infrared spectrum of a vanillyl octyl ester prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0031] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intermediate value in the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned in this specification are herein incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference in this specification is not an admission that it is prior art.

[0033] Many modifications and variations of this application specification of the specific embodiments can be made without departing from the scope or spirit of the application, which would be apparent to one of skill in the art. Other embodiments resulting from the combination of the features of the application specification will be obvious to those skilled in the art. The present application specification and examples are only exemplary.

[0034] As used herein the term "includes" means including, but not limited to:

[0035] "Made from" is synonymous with "comprising". As used herein the terms "comprises", "comprising", "includes", "including", "has", "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited only to those elements but can include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0036] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0037] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically inventing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is invented individually. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0038] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0039] "Parts by mass" refers to the basic unit of measurement that expresses the proportional relationship of the mass of multiple components. One part can represent any unit mass. It is important to understand that, unlike the number of parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0040] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0041] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating orientation or positional relationship are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0042] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention. Unless otherwise specified, all raw materials used in the following embodiments and comparative examples are commercially available, and the same raw materials were used in parallel experiments.

[0043] Preparation Example 1

[0044] Octyl vanillate, with the following chemical structural formula: Its preparation method includes the following steps:

[0045] (1) In a three-necked flask reactor, vanillic acid and n-octanol were added in a molar ratio of 1:1.5, immobilized lipase Novozyme 435 biocatalyst and 4A molecular sieve were added, the reactor was equipped with a sampling port, a condenser, and then the condenser was connected to a receiving bottle and a circulating water vacuum pump in sequence, an esterification reaction was carried out, wherein the stirring speed was set to 200 rpm, the reaction temperature was 60°C, the initial vacuum degree was controlled to be-0.04 Mpa by gradually adjusting the vacuum degree, and it decreased by 0.01 Mpa per hour, when the water content in the receiver tended to be stable, the reaction was determined to be completed, the reaction time was 6h, and the reaction product was obtained;

[0046] wherein the amount of immobilized lipase Novozyme 435 biocatalyst added is 7wt% of the total mass of vanillic acid and n-octanol, and the amount of 4A molecular sieve is 3wt% of the total mass of vanillic acid and n-octanol;

[0047] (2) After the reaction was completed, an adsorbent was added to the reaction product, the adsorbent included activated carbon, silica gel and basic alumina in a mass ratio of 1:1:1, and the mass of the adsorbent was 5wt% of the total mass of the reaction system, stirring was carried out at 40°C for 40min to remove impurities and pigments in the reaction process, after the stirring was completed, the mixed solution was filtered to separate the catalyst, water adsorbent and the like, the solution was extracted with ethyl acetate, and then the organic solvent was removed by rotary evaporation to obtain crude octyl vanillate;

[0048] (3) The crude octyl vanillate was purified by column chromatography, silica gel was used as the stationary phase, before chromatography, the silica gel column was activated with 2 times the column volume of pure petroleum ether to ensure the separation effect of column chromatography, a petroleum ether-ethyl acetate gradient elution system (initial volume ratio of petroleum ether: ethyl acetate = 95:5, gradually increasing the proportion of ethyl acetate to 70:30) was used, and after gradual elution, the target product was collected and concentrated, finally octyl vanillate with a purity of ≥98wt% was obtained, and the infrared spectrum of the octyl vanillate is shown in Figure 1 As can be seen from the figure, the characteristic peak at 3378 cm -1 is the phenolic hydroxyl vibration peak in octyl vanillate, the peak at 1712 cm -1 is the carbon-based vibration peak, and the peak at 1150 cm -1 is the C-O-C vibration peak.

[0049] Example 1

[0050] A synthetic ester insulating oil, comprising 0.3wt% of the octyl vanillate of Preparation Example 1 and the balance of TMP triester insulating oil, and a preparation method thereof, comprising the following steps:

[0051] The vanillyl octyl ester is added to the TMP triester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0052] Example 2

[0053] A synthetic ester insulating oil, comprising 0.3wt% of the vanillyl octyl ester prepared in Preparation Example 1 and the balance of PETP tetraester insulating oil, and the preparation method thereof comprises the following steps:

[0054] The vanillyl octyl ester is added to the PETP tetraester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0055] Comparative Example 1

[0056] A synthetic ester insulating oil, comprising 0.3wt% of 2,6-di-tert-butyl-p-cresol (BHT) and the balance of PETP tetraester insulating oil, and the preparation method thereof comprises the following steps:

[0057] The 2,6-di-tert-butyl-p-cresol (BHT) is added to the PETP tetraester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0058] Comparative Example 2

[0059] A synthetic ester insulating oil, comprising 0.3wt% of vanillic acid and the balance of PETP tetraester insulating oil, and the preparation method thereof comprises the following steps:

[0060] The vanillic acid is added to the PETP tetraester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0061] Comparative Example 3

[0062] A synthetic ester insulating oil, comprising 0.3wt% of vanillic acid methyl ester and the balance of PETP tetraester insulating oil, and the vanillic acid methyl ester has the structural formula of The synthetic ester insulating oil and the preparation method thereof comprises the following steps:

[0063] The vanillic acid methyl ester is added to the PETP four ester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0064] Comparative example 4

[0065] A synthetic ester insulating oil, comprising 0.3wt% vanillic acid ethyl ester and the balance of PETP four ester insulating oil, the structural formula of the vanillic acid ethyl ester is The preparation method of the synthetic ester insulating oil comprises the following steps:

[0066] The vanillic acid ethyl ester is added to the PETP four ester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0067] Comparative example 5

[0068] A synthetic ester insulating oil, comprising 0.3wt% vanillic acid p-hydroxyphenyl ethyl ester and the balance of PETP four ester insulating oil, the structural formula of the vanillic acid p-hydroxyphenyl ethyl ester is The preparation method of the synthetic ester insulating oil comprises the following steps:

[0069] The vanillic acid p-hydroxyphenyl ethyl ester is added to the PETP four ester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0070] Comparative example 6

[0071] A synthetic ester insulating oil, comprising 0.3wt% coffee acid octyl ester and the balance of PETP four ester insulating oil, the structural formula of the coffee acid octyl ester is The preparation method of the synthetic ester insulating oil comprises the following steps:

[0072] The coffee acid octyl ester is added to the PETP four ester insulating oil by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution presents clear and transparent state, the oil sample is placed in the vacuum environment of 100 ℃ and dried for 48 hours, after cooling to room temperature, it is taken out, and the synthetic ester insulating oil is obtained.

[0073] Comparative example 7

[0074] A synthetic ester insulating oil, comprising TMP triester insulating oil, the preparation method thereof comprises the following steps:

[0075] The TMP triester insulating oil is treated by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution appears clear and transparent state, the oil sample is placed in a vacuum environment at 100 ℃ for drying for 48 hours, after cooling to room temperature, take out, get synthetic ester insulating oil.

[0076] Comparative Example 8

[0077] A synthetic ester insulating oil, comprising PETP tetraester insulating oil, the preparation method comprising the following steps:

[0078] The PETP tetraester insulating oil is treated by ultrasonic dispersion method, the temperature is set to 50 ℃, the stirring time is 1 hour, until the solution appears clear and transparent state, the oil sample is placed in a vacuum environment at 100 ℃ for drying for 48 hours, after cooling to room temperature, take out, get synthetic ester insulating oil.

[0079] Performance test

[0080] 1. The initial oxidation temperature of the synthetic ester insulating oil in the examples and comparative examples under oxygen and air atmosphere was tested according to ASTM E2009 non-isothermal DSC test standard, the specific test conditions were as follows: O2 or air atmosphere was introduced, the flow rate was 30 mL / min, the heating rate was 10 ℃ / min, the test temperature range was room temperature to 400 ℃, and the test results are shown in Table 1.

[0081] 2. The dielectric loss factor, volume resistivity and AC breakdown voltage of the synthetic ester insulating oil in the examples and comparative examples were tested according to IEC 60247 and IEC 60156 standards, and the test results are shown in Table 1.

[0082] Table 1-Performance test results of synthetic ester insulating oil in examples and comparative examples

[0083]

[0084] As shown in Table 1, compared with the traditional antioxidant 2,6-di-tert-butyl-p-cresol in Comparative Example 1, the synthetic ester insulating oil added with octyl vanillate in Example 2 exhibits more excellent antioxidant effect in oxygen or air environment. In addition, due to the medium-long chain ester group structure of octyl vanillate, the antioxidant effect and electrical properties thereof are better than those of vanillic acid in Comparative Example 2, because the increase of ester chain improves the molecular weight of vanillic acid, enhances the thermal stability thereof, and has better solubility with the synthetic ester insulating oil, so as to more effectively capture free radicals generated in the oxidation process, inhibit the progress of oxidation reaction, and significantly improve the antioxidant performance of the synthetic ester insulating oil. The octyl vanillate has lower influence on the dielectric loss, volume resistivity and AC breakdown voltage of the synthetic ester insulating oil, and can maintain excellent electrical properties.

[0085] The synthetic ester insulating oils in Comparative Examples 3-5 are respectively added with methyl vanillate, ethyl vanillate and p-hydroxyphenethyl vanillate, which can improve the initial oxidation temperature of the synthetic ester insulating oil to a certain extent, but the dielectric loss factor of Comparative Examples 3-5 is higher than that of the insulating oil without antioxidant in Comparative Example 8, and the volume resistivity and AC breakdown voltage are lower than those of Comparative Example 8, indicating that the addition of methyl vanillate, ethyl vanillate and p-hydroxyphenethyl vanillate in Comparative Examples 3-5 leads to the decline of electrical properties of the insulating oil.

[0086] Meanwhile, the carbon-carbon double bond structure of octyl caffeate added in Comparative Example 6 increases the molecular polarity, so that it is difficult to form a good dissolution state in the synthetic ester insulating oil, and thus the antioxidant effect is not as good as that of the octyl vanillate in Example 2, and the electrical properties of the synthetic ester insulating oil are also declined.

[0087] The above specific examples further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the protection scope of the present application. It is particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. Use of octyl vanillate in the preparation of synthetic ester insulating oils, characterized in that, The chemical structural formula of the octyl vanillate is: .

2. A synthetic ester insulating oil characterized in that, containing 0.1 wt% - 1 wt% of octyl vanillate having the chemical structure of: .

3. The synthetic ester insulating oil according to claim 2, characterized by The composition comprises 0.1wt%-1wt% octyl vanillate, 90-99.9wt% insulating oil base and 0wt%-9wt% functional auxiliary, the functional auxiliary is at least one of preservative, antifoam agent, anti-emulsifier, the insulating oil base is TMP triester insulating oil or PETP tetraester insulating oil.

4. The method of producing synthetic ester insulating oil according to claim 3, characterized by, The method comprises the following steps: The octyl vanillate and the functional auxiliary are added into the insulating oil base by ultrasonic dispersion method, the temperature is 40-60 DEG C, the stirring time is 1-3 hours, and then the synthetic ester insulating oil is obtained by drying at 80-120 DEG C under vacuum environment for 24-48 hours.

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