Alkaline microcapsule as well as preparation method and application thereof in waste grease-based insulating oil
Alkaline microcapsules prepared by interfacial polymerization are used for the purification of waste oils, which solves the problems of insufficient adsorption efficiency and selectivity in existing technologies, realizes efficient and environmentally friendly oil recycling, and produces insulating oil that meets the standards.
Patent Information
- Application Number
- CN202511646465.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-01-09
AI Technical Summary
Existing waste oil purification methods cannot simultaneously achieve high adsorption efficiency, high selectivity, and reusability, making it difficult to prepare high-quality insulating oil in an economical and environmentally friendly manner.
Alkaline microcapsules were prepared by interfacial polymerization. Water-soluble organic bases were encapsulated in a non-polar organic solvent to form tiny droplets. At the oil-water interface, silicate esters were catalyzed to hydrolyze, forming microcapsules with a silica shell. These microcapsules were used to adsorb free fatty acids and impurities in waste oils. Reusable microcapsules were obtained by vacuum drying and rinsing.
It achieves efficient and environmentally friendly oil purification, reduces acid value and removes impurities, avoids oil contamination, significantly improves the quality and reusability of refined oil, and reduces processing costs.
Smart Images
Figure CN121288694A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of insulating oil preparation technology, specifically relating to alkaline microcapsules, their preparation methods, and their application in waste oil-based insulating oils. Background Technology
[0002] With increasingly stringent environmental protection requirements and growing demand for resource recycling, the recycling of waste oils has become a research hotspot. Waste oils, after refining and purification, have the potential to be reused as electrical insulating oils. However, residual free fatty acids, oxidation products, pigments, metal ions, and other impurities can severely affect the dielectric properties, oxidative stability, and service life of the insulating oil. Therefore, developing efficient and environmentally friendly purification technologies is crucial for the recycling of waste oils.
[0003] Waste oil refining primarily employs chemical refining methods, with key steps including degumming, alkali refining, dehydration, deodorization, and decolorization. Alkali refining and decolorization can remove highly polar impurities or pigments. The disadvantages of alkali refining include: 1. High acid values in waste oils require large amounts of alkali to neutralize free fatty acids, resulting in high alkali concentrations and significant wastewater generation. 2. Poor selectivity, leading to excessive saponification of fatty acid glycerides, high losses, and low yield. Waste oil deodorization mainly utilizes adsorption methods. Traditional adsorbents (such as activated clay, silica gel, and activated carbon) have good adsorption effects on pigments or impurities. However, adsorption primarily occurs through van der Waals adsorption of impurities or pigments via the micropores or mesopores of the adsorbent, a reversible reaction. This requires a large adsorbent dosage, and single-use adsorption is often ineffective, typically requiring multiple adsorption cycles. Furthermore, alkaline adsorbents (such as calcium hydroxide and magnesium oxide) can be used to neutralize free fatty acids, but their powder form easily leads to oil contamination, hindering the widespread application of refined oil as insulating oil.
[0004] Microencapsulation technology offers a new approach to solving these problems. Microcapsules can encapsulate active substances within polymer or inorganic shells, protecting the core material while enabling controlled release and efficient recovery. However, the application of existing microcapsules in the purification of waste oils has not been reported, especially for the efficient adsorption purification of insulating oils, where alkaline microcapsule materials with high adsorption capacity, selectivity, and reusability are lacking. Summary of the Invention
[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide alkaline microcapsules, their preparation method and their application in waste oil-based insulating oil, so as to solve the technical problem that the existing waste oil purification methods cannot simultaneously achieve high adsorption efficiency, high selectivity and reusability, thus making it difficult to prepare insulating oil in an economical and environmentally friendly manner.
[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for preparing alkaline microcapsules, comprising the following steps: Emulsifier, water-soluble organic base and non-polar organic solvent are homogeneously dispersed to obtain emulsion; then wall material monomer is slowly added to the emulsion, the reaction is stirred, the microcapsules are collected and repeatedly washed, and after vacuum drying, alkaline microcapsules are obtained. Water-soluble organic bases are encapsulated by non-polar organic solvents to form tiny water-in-oil droplets. At the oil-water interface, the water-soluble organic bases promote the hydrolysis and polymerization of the wall material monomers, forming a shell on the outer layer of the water-in-oil droplets, encapsulating the water-soluble organic bases, and forming microcapsules.
[0007] Preferably, the wall material monomer is any one of tetraethyl orthosilicate, tetramethyl orthosilicate, and tetrapropyl orthosilicate.
[0008] Preferably, the water-soluble organic base is any one of piperazine, diisopropylamine, diethylenetriamine, triethylenetetramine, triethanolamine, and tetrabutylammonium hydroxide; the nonpolar organic solvent is any one of n-hexane, cyclohexane, petroleum ether, and kerosene; and the emulsifier is any one of Span 85, Tween 85, and Tween 40.
[0009] Preferably, the stirring speed is 200-2000 rpm and the stirring time is 2-5 h.
[0010] Preferably, the mass ratio of emulsifier, water-soluble organic base, non-polar organic solvent and wall material monomer is (0.1~3):(0.5~5):(1~5):(0.5~6.5).
[0011] Preferably, the microcapsules are rinsed with a non-polar organic solvent; the vacuum drying temperature is 60~100℃; and the vacuum drying time is 6~48 h.
[0012] The present invention also discloses an alkaline microcapsule, which is prepared by the above-mentioned method for preparing alkaline microcapsules. The alkaline microcapsule uses tetraalkyl silicate monomer as wall material raw material to form a silica shell and a water-soluble organic base as core material, and is prepared by interfacial polymerization.
[0013] The present invention also discloses the application of the alkaline microcapsules prepared by the above-mentioned method in waste oil-based insulating oil. Alkaline microcapsules are added to waste oil for adsorption, and after filtering out the alkaline microcapsules, waste oil-based insulating oil is obtained.
[0014] Preferably, the adsorption stirring speed is 200~400 rpm, the adsorption temperature is 60~80℃, the adsorption time is 30~90 min, and the waste oil-based insulating oil is dehydrated and deodorized under vacuum to obtain refined insulating oil.
[0015] Preferably, the amount of alkaline microcapsules added is 1% to 5% of the mass of waste oil; The separated alkaline microcapsules can be washed with ethanol or light alkanes and then dried at 80°C, and can be reused 3 to 5 times.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing alkaline microcapsules. First, a water-soluble organic base is homogenized and dispersed to form tiny droplets encapsulated by a non-polar organic solvent, while an emulsifier maintains emulsion stability. After adding a wall material monomer, the organic base catalyzes the hydrolysis of silicate esters at the oil-water interface, resulting in condensation and the formation of a dense outer shell. After the reaction is complete, unreacted substances are removed by rinsing, and the microcapsules are dried to obtain a core-shell structure. This process precisely controls the shell formation through interfacial polymerization, ensuring effective encapsulation of the active material in the core. The microcapsules prepared by this method have a stable shell, preventing direct dissolution of alkaline substances. Compared to traditional alkali refining processes, this technology eliminates the need for large amounts of alkali solution, reducing wastewater discharge. Compared to ordinary microcapsule preparation processes, the interfacial polymerization reaction proceeds spontaneously under alkaline conditions, requiring no additional catalyst. This enables the controlled release of alkaline substances during oil processing, effectively reducing acid value while preventing oil contamination. The microcapsule shell protects the core material from dissolution by oils, extending the reaction time. The preparation process requires no complex equipment, and the formed silica shell has good mechanical strength, allowing the microcapsules to be reused multiple times. This technology provides an environmentally friendly and efficient purification method for the regeneration of waste oils, significantly improving the quality of refined oils.
[0017] The alkaline microcapsules prepared by the method disclosed in this invention, through optimized structure and preparation method, are used to prepare insulating oil from waste oil through alkaline refining. Using high-acid-value waste oil as raw material, without alkaline refining with alkaline solution, free fatty acids and impurities in the waste oil are directly adsorbed by alkaline microcapsules. After vacuum deodorization and dehydration, refined insulating oil is obtained. Antioxidants and pour point depressants are added to the refined oil to obtain the final insulating oil. Evaluation of various physicochemical indicators shows that the waste oil-based insulating oil prepared by alkaline microcapsule adsorption as the main step meets the standards for insulating oil. This invention is of great significance for promoting the green recycling of waste oil in the field of insulating oil.
[0018] The alkaline microcapsules prepared by the method disclosed in this invention can be used in waste oil-based insulating oils. Traditional alkali refining methods require the direct addition of strong alkali solutions, leading to saponification side reactions. This invention, however, achieves directional neutralization through microencapsulation of organic alkali, avoiding oil saponification losses. Compared to powdered adsorbents, which are prone to leaving oil phase residues, the intact shell structure of the microcapsules allows for complete recovery through simple filtration. Compared to physical adsorbents such as activated clay, this invention utilizes chemical neutralization reactions, resulting in higher acid value reduction efficiency. Furthermore, the regenerated microcapsules can be reused, significantly reducing processing costs. Attached Figure Description
[0019] Figure 1 The images shown are SEM images of the alkaline microcapsules disclosed in Examples 1, 2, 3 and 5 of this invention; wherein, (a) is the diisopropylamine microcapsule prepared in Example 1; (b) is the diethylenetriamine microcapsule prepared in Example 2; (c) is the piperazine microcapsule prepared in Example 3; and (d) is the triethylenetetramine microcapsule prepared in Example 5. Detailed Implementation
[0020] The technical solution of the present invention will be clearly and completely described below. 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.
[0021] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.
[0022] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.
[0023] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.
[0024] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.
[0025] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.
[0026] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.
[0027] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.
[0028] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.
[0029] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.
[0030] The method for preparing alkaline microcapsules disclosed in this invention includes: (1) The emulsifier, water-soluble organic base and non-polar organic solvent are dispersed in a homogenizing emulsifier to obtain an emulsion; The mass ratio of nonpolar organic solvent, water-soluble organic base, and emulsifier is (1-5): (0.5-5): (0.1-3); the water-soluble organic base is any one of piperazine, diisopropylamine, diethylenetriamine, triethylenetetramine, triethanolamine, and tetrabutylammonium hydroxide, used as the core material; The nonpolar organic solvent is any one of n-hexane, cyclohexane, petroleum ether, and kerosene; the emulsifier is any one of Span 85, Tween 85, and Tween 40. (2) Slowly add 5-25g of wall material monomer to the emulsion obtained in step (1), control the stirring speed to 200-2000rpm, and react for 2-5 h; the mass ratio of wall material monomer to water-soluble organic base is (0.5~6.5):(0.5~5); The wall material monomer is any one of tetraethyl orthosilicate, tetramethyl orthosilicate, and tetrapropyl orthosilicate; (3) Collect microcapsules by high-speed centrifugation and wash them repeatedly with non-polar organic solvents. Place them in a vacuum drying oven at 60-100℃ for 6-48 h to obtain alkaline microcapsules. These alkaline microcapsules are made by interfacial polymerization with a water-soluble organic base as the core and one of the tetraalkyl silicates as the wall material. They can effectively adsorb free fatty acids and impurities in waste oils and efficiently reduce the acid value of waste oils.
[0031] This invention first disperses a water-soluble organic base in a non-polar organic solvent. Due to the presence of an emulsifier, the water-soluble organic base is encapsulated by the non-polar organic solvent to form tiny water-in-oil droplets. At the oil-water interface, the water-soluble organic base promotes the hydrolysis and polymerization of tetraalkyl silicate, forming a silica shell on the outer layer of the droplets, thus encapsulating the water-soluble organic base to form microcapsules. The preparation process of this invention is simple, and the adsorption capacity of the microcapsules can be controlled according to the type of water-soluble organic base added.
[0032] Waste oil pretreatment Filtration and impurity removal: The waste oil is filtered through a 100-200 mesh sieve to remove mechanical impurities, particulate matter, etc.
[0033] Dehydration treatment (optional): If the moisture content is high (>0.1%), it can be dehydrated under reduced pressure at 105~120℃ until the moisture content is ≤0.05%.
[0034] Alkaline microcapsule adsorption Microcapsule addition: Add alkaline microcapsules at 1%~5% of the waste oil mass. The specific dosage depends on the initial acid value (e.g., 5% when the acid value is 13~15 mg KOH / g). Adsorption conditions: Temperature: 60~80℃ (to promote diffusion and adsorption equilibrium); Stirring speed: 200~400 rpm, for 30~90 min; Vacuum adsorption.
[0035] solid-liquid separation Filtration: Microcapsules and refined oil are separated by pressure filtration (0.5~1.0 MPa) or centrifugation (3000~5000 rpm, 10~15 min) to obtain a clear oil phase. Microcapsule regeneration: The separated microcapsules are washed with 10% NaOH ethanol solution and then dried at 80℃, and can be reused 3~5 times.
[0036] Deodorization and dehydration of refined oil Dehydration: At lower temperatures (100~150℃) and under high vacuum, the solubility of water and dissolved gases decreases sharply, causing them to overflow from the oil and be removed. This reduces the trace amount of water in the oil and removes dissolved oxygen, preventing the oil from oxidizing during subsequent high-temperature deodorization.
[0037] Deodorization: Under high vacuum (absolute pressure usually below 0.5 kPa) and high temperature (220~260℃) conditions, direct steam is used as a carrier to reduce the partial pressure of volatile components in the oil to the minimum, and odor substances are evaporated along with the steam.
[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0039] Example 1 A method for preparing diisopropylamine microcapsules includes the following steps: (1) Mix 50 g of cyclohexane, 10 g of diisopropylamine aqueous solution (50%) and 1 g of Span 85, disperse in a homogenizer to prepare an emulsion for later use; (2) Add 15g of tetraethyl orthosilicate to the emulsion in step (1), control the stirring speed at 1000 rpm, and react for 3 h; (3) Collect the microcapsules by high-speed centrifugation and wash them three times with cyclohexane. Place them in a blower oven and dry them at 60°C for 48 h to obtain diisopropylamine microcapsules.
[0040] (4) Add diisopropylamine microcapsules to the waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated diisopropylamine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0041] Example 2 A method for preparing diethylenetriamine microcapsules includes the following steps: (1) Mix 25 g petroleum ether, 5 g diethylenetriamine aqueous solution (50%) and 0.5 g Tween 85, disperse them in a homogenizing emulsifier to make an emulsion for later use; (2) Add 10g of tetraethyl orthosilicate to the emulsion in step (1), and control the stirring speed to 2000 rpm for 5 h. (3) Collect the microcapsules by high-speed centrifugation and rinse them three times with petroleum ether. Place them in a blower oven and dry them at 80°C for 6 hours to obtain diethylenetriamine microcapsules.
[0042] (4) Add diethylenetriamine microcapsules to the waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated diethylenetriamine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0043] Example 3 A method for preparing piperazine microcapsules includes the following steps: (1) Dissolve piperazine at 150 °C for later use; (2) Mix 70 g kerosene, 15 g piperazine solution and 1.5 g Span 85, disperse in a homogenizer to form an emulsion for later use; (3) Add 15g of tetraethyl orthosilicate to the emulsion in step (2), control the stirring speed at 1000 rpm, and react for 3 h; (4) Filter the oil phase to collect the microcapsules and rinse them three times with kerosene. Then dry them in a blower oven at 80 ℃ for 6 h to obtain piperazine microcapsules.
[0044] (4) Add piperazine microcapsules to waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated piperazine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0045] Example 4 A method for preparing tetrabutylammonium hydroxide microcapsules includes the following steps: (1) Mix 20g kerosene, 5g tetrabutylammonium hydroxide (75%) solution and 0.5g Tween 40, disperse them thoroughly, and prepare an emulsion for later use; (2) The emulsion obtained in step (1) is mechanically stirred at room temperature, and the stirring speed is controlled at 600 rpm; (3) Add 8g of tetraethyl orthosilicate to the solution in step (2) and react for 4 h; (4) Filter the oil phase, collect the microcapsules, rinse them three times with petroleum ether, and dry them in a forced-air constant temperature drying oven at 100 ℃ for 8 hours to obtain tetrabutylammonium hydroxide microcapsules.
[0046] (4) Add tetrabutylammonium hydroxide microcapsules to the waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated tetrabutylammonium hydroxide microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0047] Example 5 A method for preparing triethylenetetramine microcapsules includes the following steps: (1) Mix 25g kerosene, 6g triethylenetetramine (70%) solution and 0.5g Tween 85, disperse them thoroughly, and prepare an emulsion for later use; (2) Add 10g of tetraethyl orthosilicate to the emulsion in step (1), and control the stirring speed to 800 rpm for 4 hours; (3) Filter the oil phase, collect the microcapsules, rinse them three times with petroleum ether, and dry them in a blower oven at 80°C for 24 hours to obtain triethylenetetramine microcapsules.
[0048] (4) Add triethylenetetramine microcapsules to the waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated triethylenetetramine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0049] Example 6 A method for preparing triethanolamine microcapsules includes the following steps: (1) Mix 50g of n-hexane, 15g of triethanolamine and 1.5g of Tween 85, disperse them thoroughly, and prepare an emulsion for later use; (2) Add 25g of tetraethyl orthosilicate to the emulsion in step (1), and control the stirring speed to 1000 rpm for 5h. (3) Filter the oil phase, collect the microcapsules, rinse them three times with petroleum ether, and dry them in a forced-air constant temperature drying oven at 100 degrees Celsius for 18 hours to obtain triethanolamine microcapsules.
[0050] (4) Triethanolamine microcapsules are added to waste oil to adsorb the oil, and then alkaline microcapsules are filtered out by vacuum filtration to obtain waste oil-based insulating oil. The separated triethanolamine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0051] Example 7 A method for preparing piperazine microcapsules includes the following steps: (1) Dissolve piperazine at 150 °C for later use; (2) Mix 10 g of n-hexane, 5 g of piperazine solution and 0.1 g of Span 85, disperse in a homogenizer to form an emulsion for later use; (3) Add 5g of tetraethyl orthosilicate to the emulsion in step (2), control the stirring speed at 200rpm, and react for 2h; (4) Filter the oil phase to collect the microcapsules and rinse them three times with kerosene. Place them in a blower oven at 60 ℃ and dry for 12 hours to obtain piperazine microcapsules.
[0052] (4) Add piperazine microcapsules to waste oil to adsorb the oil, and then filter out the alkaline microcapsules by vacuum filtration to obtain waste oil-based insulating oil. The separated piperazine microcapsules are washed and dried with 10% NaOH ethanol solution and reused.
[0053] Example 8 A method for preparing triethanolamine microcapsules includes the following steps: (1) Mix 5g kerosene, 5g triethanolamine and 3g Tween 85, disperse them thoroughly to make an emulsion, and set aside; (2) Add 6.5g of tetraethyl orthosilicate to the emulsion in step (1), and control the stirring speed at 400 rpm for 3h. (3) Filter the oil phase, collect the microcapsules, rinse them three times with petroleum ether, and dry them in a forced-air constant temperature drying oven at 80 degrees Celsius for 3 hours to obtain triethanolamine microcapsules.
[0054] (4) Add 2g of triethanolamine microcapsules to 100g of waste oil to adsorb the oil. The adsorption stirring speed is 300rpm and the adsorption temperature is 60 degrees Celsius. After adsorption for 30min, filter out the alkaline microcapsules through a 100-mesh filter screen to obtain waste oil-based insulating oil. Perform vacuum dehydration and deodorization treatment on the waste oil-based insulating oil to obtain refined oil. The water content of the refined oil is 0.05%. The triethanolamine microcapsules can be reused 4 times after being washed and dried with 10% NaOH ethanol solution.
[0055] Example 9 A method for preparing diisopropylamine microcapsules includes the following steps: (1) Mix 40g cyclohexane, 20g diisopropylamine aqueous solution (50%) and 1.5g Span 85, disperse in a homogenizer to form an emulsion for later use; (2) Add 20g of tetraethyl orthosilicate to the emulsion in step (1), control the stirring speed at 800 rpm, and react for 4h; (3) Collect the microcapsules by high-speed centrifugation and wash them three times with cyclohexane. Place them in a blower oven and dry them at 80°C for 24 hours to obtain diisopropylamine microcapsules.
[0056] (4) Add 1g of diisopropylamine microcapsules to 100g of waste oil to adsorb the oil. The adsorption stirring speed is 200rpm and the adsorption temperature is 60 degrees Celsius. After adsorption for 30min, filter out the alkaline microcapsules through a 100-mesh filter screen to obtain waste oil-based insulating oil. Perform vacuum dehydration and deodorization treatment on the waste oil-based insulating oil to obtain refined oil. The water content of the refined oil is 0.05%. The diisopropylamine microcapsules can be reused 3 times after being washed and dried with 10% NaOH ethanol solution.
[0057] Example 10 A method for preparing diethylenetriamine microcapsules includes the following steps: (1) Mix 5g petroleum ether, 5g diethylenetriamine aqueous solution (50%) and 0.1g Tween 85, disperse in a homogenizer to form an emulsion, and set aside for later use; (2) Add 5g of tetraethyl orthosilicate to the emulsion in step (1), and control the stirring speed to 1000 rpm for 4 h. (3) Collect the microcapsules by high-speed centrifugation and rinse them three times with petroleum ether. Place them in a blower oven and dry them at 60°C for 24 h to obtain diethylenetriamine microcapsules.
[0058] (4) Add 5g of diethylenetriamine microcapsules to 100g of waste oil to adsorb the oil. The adsorption stirring speed is 400rpm and the adsorption temperature is 80 degrees Celsius. After adsorption for 90min, filter out the alkaline microcapsules through a 200-mesh filter screen to obtain waste oil-based insulating oil. Perform vacuum dehydration and deodorization treatment on the waste oil-based insulating oil to obtain refined oil. The water content of the refined oil is 0.03%. The diethylenetriamine microcapsules can be reused 5 times after being washed and dried with 10% NaOH ethanol solution.
[0059] Figure 1The images show SEM images of the alkaline microcapsules disclosed in Examples 1, 2, 3 and 5 of this invention; (a) is the diisopropylamine microcapsule prepared in Example 1; (b) is the diethylenetriamine microcapsule prepared in Example 2; (c) is the piperazine microcapsule prepared in Example 3; and (d) is the triethylenetetramine microcapsule prepared in Example 5. As can be seen from the images, they are spherical or near-spherical, with good sphericity. Some microcapsules have relatively smooth surfaces and dense walls, while others have rough or porous surfaces, with sizes ranging from 10 to 30 μm.
[0060] Table 1. Comparison of color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different alkaline microcapsules (added at 5% of waste oil) disclosed in different embodiments.
[0061] Table 1 shows a comparison of the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different alkaline microcapsules disclosed in different embodiments. As can be seen from the table, the color, acid value, and dielectric loss parameters of the waste oil-based insulating oil after adsorption by alkaline microcapsules are all superior to those after adsorption by ordinary adsorption materials.
[0062] Table 2. Comparison of color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by diisopropylamine microcapsules with different dosages.
[0063] Table 2 compares the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different amounts of diisopropylamine microcapsules. As can be seen from the table, diisopropylamine microcapsules improve the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil. In their respective experiments, the effects of reducing color, decreasing acid value, improving dielectric loss factor, and increasing breakdown voltage all show an increasing trend with the increase of microcapsule addition.
[0064] Table 3. Comparison of color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by diethylenetriamine microcapsules with different dosages.
[0065] Table 3 compares the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different amounts of diethylenetriamine microcapsules. As can be seen from the table, triethylenetetramine microcapsules improve the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil. In their respective experiments, the effects of reducing color, decreasing acid value, improving dielectric loss factor, and increasing breakdown voltage all increase with the increase of microcapsule addition.
[0066] Table 4. Comparison of color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different dosages of piperazine microcapsules.
[0067] Table 4 compares the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different amounts of piperazine microcapsules. As can be seen from the table, piperazine microcapsules improve the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil. In their respective experiments, the effects of reducing color, decreasing acid value, improving dielectric loss factor, and increasing breakdown voltage all increase with the increase of microcapsule addition.
[0068] Table 5. Comparison of color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by microcapsules with different dosages of tetrabutylammonium hydroxide (TBAH).
[0069] Table 5 compares the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil after adsorption by different amounts of tetrabutylammonium hydroxide microcapsules. As can be seen from the table, TBAH microcapsules improve the color, acid value, dielectric loss factor, and breakdown voltage of waste oil-based insulating oil. In their respective experiments, the effects of reducing color, decreasing acid value, improving dielectric loss factor, and increasing breakdown voltage all show an increasing trend with the increase of microcapsule addition.
[0070] In summary, this invention discloses alkaline microcapsules, their preparation method, and their application in waste oil-based insulating oil. The microcapsules prepared by this method belong to the field of waste oil adsorbent material preparation. These microcapsules possess high specific surface area, strong alkalinity, and excellent adsorption performance, effectively reducing the acid value of waste oil and adsorbing other impurities, thereby producing a standard-compliant vegetable insulating oil. This invention employs interfacial polymerization to prepare microcapsules. A water-soluble organic base is dispersed in a non-polar organic solvent, emulsified, and then a microcapsule wall material monomer is added. After polymerization, the microcapsules are obtained. This invention has advantages such as high efficiency, environmental friendliness, and low cost, making it suitable for large-scale industrial production. The microcapsule particle size is 10-30 μm, and mesopores are present. Using waste oil as raw material, the resulting insulating oil, after adsorption, meets the corresponding standards for physicochemical properties such as acid value, dielectric loss, and breakdown voltage.
[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing alkaline microcapsules, characterized in that, Includes the following steps: Emulsifier, water-soluble organic base and non-polar organic solvent are homogeneously dispersed to obtain emulsion; then wall material monomer is slowly added to the emulsion, the reaction is stirred, the microcapsules are collected and repeatedly washed, and after vacuum drying, alkaline microcapsules are obtained. The water-soluble organic base is encapsulated by a non-polar organic solvent to form tiny water-in-oil droplets. At the oil-water interface, the water-soluble organic base promotes the hydrolysis and polymerization of the wall material monomers, forming a shell on the outer layer of the water-in-oil droplets, encapsulating the water-soluble organic base, and forming microcapsules.
2. The method for preparing alkaline microcapsules according to claim 1, characterized in that, The wall material monomer is any one of tetraethyl orthosilicate, tetramethyl orthosilicate, and tetrapropyl orthosilicate.
3. The method for preparing alkaline microcapsules according to claim 1, characterized in that, The water-soluble organic base is any one of piperazine, diisopropylamine, diethylenetriamine, triethylenetetramine, triethanolamine, and tetrabutylammonium hydroxide; the nonpolar organic solvent is any one of n-hexane, cyclohexane, petroleum ether, and kerosene; and the emulsifier is any one of Span 85, Tween 85, and Tween 40.
4. The method for preparing alkaline microcapsules according to claim 1, characterized in that, The stirring speed is 200-2000 rpm, and the stirring time is 2-5 h.
5. The method for preparing alkaline microcapsules according to claim 1, characterized in that, The mass ratio of the emulsifier, water-soluble organic base, non-polar organic solvent and wall material monomer is (0.1~3):(0.5~5):(1~5):(0.5~6.5).
6. The method for preparing alkaline microcapsules according to claim 1, characterized in that, The microcapsules are rinsed with a non-polar organic solvent; the vacuum drying temperature is 60~100℃; and the vacuum drying time is 6~48 h.
7. An alkaline microcapsule, characterized in that, The alkaline microcapsules are prepared by the method described in any one of claims 1 to 6, wherein the alkaline microcapsules are prepared by interfacial polymerization using tetraalkyl silicate ester wall material monomer as wall material raw material to form a silica shell and water-soluble organic base as core material.
8. The application of alkaline microcapsules prepared by the method of any one of claims 1 to 6 in waste oil-based insulating oil, characterized in that, Alkaline microcapsules are added to waste oil for adsorption. After filtering out the alkaline microcapsules, waste oil-based insulating oil is obtained.
9. The application of the alkaline microcapsules according to claim 8 in waste oil-based insulating oil, characterized in that, The adsorption stirring speed is 200~400 rpm, the adsorption temperature is 60~80℃, and the adsorption time is 30~90 min. The waste oil-based insulating oil is dehydrated and deodorized under vacuum to obtain refined insulating oil.
10. The application of the alkaline microcapsules according to claim 8 in waste oil-based insulating oil, characterized in that, The amount of alkaline microcapsules added is 1% to 5% of the mass of waste oil; The separated alkaline microcapsules can be washed with ethanol or light alkanes and then dried at 80°C, and can be reused 3 to 5 times.