Method for preparing electrical equipment insulating liquid from waste edible oil methyl ester with characteristic of improving pour point of ignition

Abstract

The invention relates to a method for preparing an electrical equipment insulating liquid from waste edible oil methyl ester with an improved pour ignition point characteristic, and belongs to the technical field of insulating liquids. Distilling the waste edible oil methyl ester to obtain distilled waste edible oil methyl ester; the method comprises the following steps: adding a molecular sieve, immobilized lipase IM-100, neopentyl glycol, distilled waste edible oil methyl ester and methyl nonanoate into a reaction vessel, reacting for 72-96 hours under the conditions that the temperature is 40-50 DEG C and the stirring rotating speed is 120-130 rpm, and separating out the molecular sieve and the immobilized lipase IM-100 to obtain waste edible oil-nonanoate neopentyl glycol diester; and carrying out adsorption, vacuum drying and filter membrane filtration on the obtained waste edible oil-nonanoic acid-based neopentyl glycol diester to generate the waste edible oil-nonanoic acid-based neopentyl glycol diester insulating liquid. The obtained waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid has an excellent low-temperature flow characteristic, and the ignition point also reaches the fireproof safety standard of K-grade insulating oil, so that the risk of accidents of power equipment such as a transformer and the like under severe environment conditions is reduced to a great extent; the vacancy of the insulating liquid in high-safety application places such as offshore wind power and the like is supplemented, and more choices are provided for the application of the insulating liquid.

Description

Technical Field

[0001] The invention relates to a method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point ignition property, belonging to the technical field of insulating liquid. Background Art

[0002] The safety of electrical equipment is the first line of defense to ensure the stable operation of the power system. As a key component of the power grid, power transformers play a vital role in the transmission and distribution of energy and are often hailed as the "heart" of the power system. Insulating oil is called the "blood" of power transformers. First, it eliminates air gaps in the transformer by impregnation and filling, thereby improving electrical insulation strength and helping heat dissipation. Second, it acts as an arc extinguishing medium, reducing the possibility of equipment failure.

[0003] Since 1887, mineral oil has been widely used as an insulating medium due to its good performance and relatively low cost. However, mineral oil has a low flash point and poor degradation ability, which will cause resource depletion and increase greenhouse gas emissions, making it difficult to use in safety-critical applications such as offshore wind power. Therefore, the use of a new liquid insulation mechanism that is non-toxic, environmentally friendly and biodegradable has become a natural choice to replace mineral oil.

[0004] In recent years, ester-based insulating oils have been widely studied due to their excellent natural degradability and excellent physical and chemical properties. For example, sunflower oil, rapeseed oil, linseed oil, and soybean oil have been tested for transformer oil applications and are gradually being considered as promising candidates for large transformers. However, they are highly susceptible to oxidation, which can shorten the service life of transformers. These shortcomings limit its sustainable application in transformers, so there is an urgent need to find an antioxidant, economical, and environmentally friendly raw material to produce insulating oil. Summary of the invention

[0005] In view of the problems and shortcomings of the above-mentioned prior art, the present invention provides a method for preparing an insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics. The present invention uses waste edible oil methyl ester as the main raw material. Compared with traditional edible vegetable oil, the cost of waste edible oil methyl ester is low, about 20-40% cheaper. The present invention adopts immobilized lipase IM-100 as a catalyst, and introduces antioxidant functional groups into the molecules of waste edible oil through ester exchange technology. The generated polyol ester changes the chemical structure of the waste edible oil. This change not only effectively overcomes the problem of easy oxidation of waste edible oil, but also achieves the goal of "waste into resources" and eliminates the negative impact that waste edible oil may cause to the environment. In addition, the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid prepared by the present invention has achieved significant improvements in various physical and chemical properties, specifically in: the improvement of ignition point, flash point, pour point and antioxidant stability. The improvement of these properties makes the insulating liquid have good low-temperature fluidity, better high temperature resistance, and stronger antioxidant ability, which greatly enhances the stability and reliability of electrical equipment, especially transformers in power systems.

[0006] The present invention is achieved through the following technical solutions.

[0007] A method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics, the steps comprising:

[0008] Step 1, distilling waste edible oil methyl ester to obtain distilled waste edible oil methyl ester;

[0009] Step 2, adding molecular sieves, immobilized lipase IM-100, neopentyl glycol, waste edible oil methyl ester and nonanoic acid methyl ester after distillation in step 1 into a reaction dish, and reacting for 72-96 hours at a temperature of 40-50° C. and a stirring speed of 120-130 rpm, separating the molecular sieves and immobilized lipase IM-100 to obtain waste edible oil-nonanoic acid neopentyl glycol diester;

[0010] Step 3, measuring the acid value of the waste cooking oil-nonanoic acid neopentyl glycol diester obtained in step 2, and performing alkali refining with sodium hydroxide to meet the acid value standard of synthetic ester insulating oil;

[0011] Step 4: After alkali refining in step 3, the waste edible oil-nonanoic acid neopentyl glycol diester is obtained, and adsorption, vacuum drying, and membrane filtration are performed to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0012] The distillation in step 1 is carried out at a pressure of 0.1-0.3 mbar and a temperature of 150-180°C.

[0013] In step 2, the molecular sieve accounts for 5% of the total mass of the reaction substrate.

[0014] In the step 2, the amount of immobilized lipase IM-100 added is 3-5% of the mass of waste edible oil methyl ester after distillation, and the immobilized lipase IM-100 is placed in the reaction vessel through a 100-mesh stainless steel sieve.

[0015] In the step 2, the molar ratio of neopentyl glycol to methyl ester alcohol of waste edible oil after distillation is 2.3-2.5:1; the amount of methyl nonanoate added is 5-20% of the mass of methyl ester of waste edible oil after distillation.

[0016] The acid value measurement method in step 3 is as follows: anhydrous ethanol is placed in a flask with a condenser to heat and remove CO2, an alkaline blue 6B indicator is added dropwise, and an ethanol solution is obtained by titrating with a 0.05 mol / L KOH solution until neutral; then, waste edible oil-nonanoic acid neopentyl glycol diester is mixed with the ethanol solution, and the solution is titrated with a KOH solution until the solution changes from blue to light red; the acid value is calculated as follows: A v It is the acid value, unit is MgKOH / g; M KOH is the molar mass of KOH; N is the concentration of KOH solution, unit is mol / L; V is the volume of KOH solution consumed, and G is the mass of a certain mass of waste edible oil-nonanoic acid neopentyl glycol diester taken out.

[0017] The alkaline substance required for alkali refining in step 3 is NaOH, and the calculation formula for the amount of alkali used is: Among them A ve is the acid value of waste edible oil-nonanoic acid neopentyl glycol diester; m is the mass of the product; M NaOH and M KOH is the molar mass of NaOH and KOH.

[0018] The adsorption in step 4 is to add an adsorbent consisting of basic alumina, 3A molecular sieve, silica gel and activated clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption lasts for 60 minutes.

[0019] The vacuum drying in step 4 is performed at 100 Pa and 75° C. for 48 hours.

[0020] The filter membrane in step 4 is a 0.25 μm filter membrane.

[0021] In the above step 2, the molecular sieve adsorbs the methanol molecules generated.

[0022] The beneficial effects of the present invention are:

[0023] (1) The method of the present invention uses immobilized lipase IM-100 as a catalyst, which has many advantages over traditional catalysts (strong acid and strong base), simple purification, and no by-products.

[0024] (2) The method of the present invention reduces energy demand, lowers waste disposal costs, can be recycled multiple times, uses "mild" (40-50°C) conditions, and does not require hazardous reagents.

[0025] (3) The present invention reduces the content of low molecular weight raw materials in waste cooking oil methyl ester by using the method of vacuum distillation, so that the waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid meets the K-level fire safety index, thereby further improving the fire safety of the power system.

[0026] (4) The present invention adds methyl nonanoate containing odd-numbered carbon, which greatly improves the low-temperature fluidity of the insulating oil and reduces the risk of transformer accidents in cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a waste edible oil-nonanoic acid neopentyl glycol diester reaction vessel prepared by the present invention.

[0028] Figure 2 The present invention is a complete flow chart of preparing waste edible oil-nonanoic acid neopentyl glycol diester.

[0029] Figure 3 This is the equation for the ester exchange technology using waste edible oil methyl ester and methyl octanoate with neopentyl glycol. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Comparative Example 1

[0032] The method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0033] Step 1, the components of the waste edible oil methyl ester before distillation are determined by GC-MS as shown in Table 1;

[0034] Table 1 Composition of undistilled fatty acid methyl esters of waste edible oil methyl esters

[0035] Types and contents of fatty acid methyl esters (wt%) Before distillation <![CDATA[Methyl laurate C 12：0 > 0.3 <![CDATA[Methyl myristate C 14：0 > 0.9 <![CDATA[Methyl palmitate C 16：0 > 36.5 <![CDATA[Methyl stearate C 18：0 > 9.28 <![CDATA[Methyl oleate C 18：1 > 32.38 <![CDATA[Methyl linoleate C 18：2 > 20.2 other 0.44

[0036] Step 2: Figure 1In a reaction dish, a molecular sieve is added to the bottom of the reaction dish, and an immobilized lipase IM-100 is placed inside a 100-mesh stainless steel sieve sleeve and then installed inside the 100-mesh stainless steel sieve sleeve, and then neopentyl glycol, undistilled waste edible oil methyl ester and nonanoic acid methyl ester are added, and the temperature is 45° C. and the stirring speed is 120 rpm. After reacting for 96 hours, the molecular sieve and the immobilized lipase IM-100 are separated to obtain waste edible oil-nonanoic acid neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester; the molar ratio of neopentyl glycol to waste edible oil methyl ester is 2.4:1; the amount of nonanoic acid methyl ester added is 5% of the mass of the waste edible oil methyl ester;

[0037] Step 3 and step 4, the waste edible oil-nonanoic acid neopentyl glycol diester obtained in step 2 is alkali-refined with NaOH (the amount of NaOH added is 3-4g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate an undistilled waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0038] The undistilled waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid obtained in Comparative Example 1 was subjected to performance tests. The flash point, pour point, breakdown voltage and viscosity were in accordance with ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 2 below.

[0039] Table 2 Physical and chemical properties of undistilled waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid

[0040]

[0041] Comparative Example 2

[0042] The method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0043] Step 1, distilling the waste edible oil methyl ester at a pressure of 0.1-0.3 mbar and a temperature of 150° C. to obtain the distilled waste edible oil methyl ester, and testing the components of the waste edible oil methyl ester before and after distillation at 150° C. by GC-MS, as shown in Table 3;

[0044] Table 3 Composition of fatty acid methyl esters of waste cooking oil methyl ester before and after distillation at 150°C

[0045] Fatty acid methyl ester (wt%) Before distillation After distillation <![CDATA[Methyl laurate C 12：0 > 0.3 0.12 <![CDATA[Methyl myristate C 14：0 > 0.9 0.15 <![CDATA[Methyl palmitate C 16：0 > 36.5 10.3 <![CDATA[Methyl stearate C 18：0 > 9.28 14.8 <![CDATA[Methyl oleate C 18：1 > 32.38 45.8 <![CDATA[Methyl linoleate C 18：2 > 20.2 28.83 other 0.44 0

[0046] Step 2: Figure 1 In a reaction dish, a molecular sieve is added to the bottom of the reaction dish, and an immobilized lipase IM-100 is placed inside the 100-mesh stainless steel sieve sleeve and then installed inside the 100-mesh stainless steel sieve sleeve, and then neopentyl glycol and the waste edible oil methyl ester after distillation in step 1 are added. After the reaction is carried out for 96 hours at a temperature of 45° C. and a stirring speed of 120 rpm, the molecular sieve and the immobilized lipase IM-100 are separated to obtain a waste edible oil-based neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of the immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester after distillation; the molar ratio of neopentyl glycol to the waste edible oil methyl ester alcohol after distillation is 2.4:1;

[0047] Step 3 and step 4, the waste edible oil-based neopentyl glycol diester obtained in step 2 is alkali-refined using NaOH (the amount of NaOH added is 3-4g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate a waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0048] The waste edible oil-based neopentyl glycol diester insulating liquid obtained in Comparative Example 2 and the undistilled waste edible oil-based neopentyl glycol diester insulating liquid prepared using the parameters of Comparative Example 2 were subjected to performance tests. The flash point, pour point, breakdown voltage, and viscosity were in accordance with ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 4 below.

[0049] Table 4 Physical and chemical properties of the waste edible oil-based neopentyl glycol diester insulating liquid obtained after distillation at 150°C

[0050]

[0051] From Table 4, it can be seen that the pour point of the waste cooking oil-based neopentyl glycol diester insulating liquid after distillation is -27°C, which improves the low-temperature fluidity of the insulating oil. At the same time, the flash point is as high as 324°C, which is higher than the safety standard of K-class insulating liquid.

[0052] Example 1

[0053] like Figures 1 to 3 As shown, the method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0054] Step 1, distilling the waste edible oil methyl ester at a pressure of 0.1-0.3 mbar and a temperature of 160° C. to obtain the waste edible oil methyl ester after distillation, and the waste edible oil methyl ester before and after distillation was determined by GC-MS. The components of the waste edible oil methyl ester before and after distillation are shown in Table 5;

[0055] Table 5 Composition of fatty acid methyl esters of waste cooking oil methyl ester before and after distillation at 160°C

[0056] Types and contents of fatty acid methyl esters (wt%) Before distillation After distillation <![CDATA[Methyl laurate C 12：0 > 0.3 0 <![CDATA[Methyl myristate C 14：0 > 0.9 0.14 <![CDATA[Methyl palmitate C 16：0 > 36.5 10.3 <![CDATA[Methyl stearate C 18：0 > 9.28 14.8 <![CDATA[Methyl oleate C 18：1 > 32.38 45.8 <![CDATA[Methyl linoleate C 18：2 > 20.2 28.83 other 0.44 0.13

[0057] Step 2: Figure 1 In a reaction dish, molecular sieves are added to the bottom of the reaction dish, and immobilized lipase IM-100 is placed inside the 100-mesh stainless steel sieve sleeve and then installed inside the 100-mesh stainless steel sieve sleeve, and then neopentyl glycol, waste edible oil methyl ester after distillation in step 1 and methyl nonanoate are added. After the reaction is carried out for 84 hours at a temperature of 45° C. and a stirring speed of 120 rpm, the molecular sieves and immobilized lipase IM-100 are separated to obtain waste edible oil-nonanoic acid neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester after distillation; the molar ratio of neopentyl glycol to the waste edible oil methyl ester after distillation is 2.3:1; the amount of methyl nonanoate added is 5% of the mass of the waste edible oil methyl ester after distillation;

[0058] Step 3 and step 4, the waste edible oil-nonanoic acid neopentyl glycol diester obtained in step 2 is alkali-refined with NaOH (the amount of NaOH added is 2-3g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0059] The various properties of the waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid prepared in this embodiment, such as flash point, pour point, breakdown voltage, viscosity, etc., were tested according to ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 6 below.

[0060] Table 6 Physical and chemical properties of waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid obtained after distillation at 160℃

[0061]

[0062] It can be seen from Table 6 that the pour point of the waste edible oil-based neopentyl glycol diester obtained after adding 5% methyl nonanoate and distilling at 160°C is -35°C, and its low-temperature fluidity is further improved compared with Comparative Example 2.

[0063] Example 2

[0064] like Figures 1 to 3 As shown, the method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0065] Step 1, distilling the waste edible oil methyl ester at a pressure of 0.1-0.3 mbar and a temperature of 170° C. to obtain the waste edible oil methyl ester after distillation, and the waste edible oil methyl ester before and after distillation was determined by GC-MS. The components of the waste edible oil methyl ester before and after distillation are shown in Table 7;

[0066] Table 7 Fatty acid composition of waste cooking oil methyl ester before and after distillation at 170°C

[0067] Types and contents of fatty acid methyl esters (wt%) Before distillation After distillation <![CDATA[Methyl laurate C 12：0 > 0.3 0 <![CDATA[Methyl myristate C 14：0 > 0.9 0.06 <![CDATA[Methyl palmitate C 16：0 > 36.5 8.5 <![CDATA[Methyl stearate C 18：0 > 9.28 16.8 <![CDATA[Methyl oleate C 18：1 > 32.38 51.57 <![CDATA[Methyl linoleate C 18：2 > 20.2 23.07 other 0.44 0

[0068] Step 2: Figure 1 In a reaction dish, molecular sieves are added to the bottom of the reaction dish, and immobilized lipase IM-100 is placed inside a 100-mesh stainless steel sieve sleeve and then installed inside a 100-mesh stainless steel sieve sleeve, and then neopentyl glycol, waste edible oil methyl ester after distillation in step 1, and methyl nonanoate are added. After reacting for 84 hours at a temperature of 45° C. and a stirring speed of 120 rpm, the molecular sieves and immobilized lipase IM-100 are separated to obtain waste edible oil-nonanoic acid neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester after distillation; the molar ratio of neopentyl glycol to the waste edible oil methyl ester after distillation is 2.3:1; the amount of methyl nonanoate added is 10% of the mass of the waste edible oil methyl ester after distillation;

[0069] Step 3 and step 4, the waste edible oil-nonanoic acid neopentyl glycol diester obtained in step 2 is alkali-refined by using NaOH (the amount of NaOH added is 2-3g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the amount added is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0070] The various properties of the waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid prepared in this embodiment, such as flash point, pour point, breakdown voltage, viscosity, etc., were tested according to ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 8 below.

[0071] Table 8 Physical and chemical properties of waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid obtained after distillation at 170℃

[0072]

[0073] Example 3

[0074] like Figures 1 to 3 As shown, the method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0075] Step 1, distilling the waste edible oil methyl ester at a pressure of 0.1-0.3 mbar and a temperature of 180° C. to obtain the waste edible oil methyl ester after distillation, and the waste edible oil methyl ester before and after distillation was determined by GC-MS. The components of the waste edible oil methyl ester before and after distillation are shown in Table 9;

[0076] Table 9 Composition of fatty acid methyl esters of waste cooking oil methyl ester before and after distillation at 180°C

[0077] Types and contents of fatty acid methyl esters (wt%) Before distillation After distillation <![CDATA[Methyl laurate C 12：0 > 0.3 0 <![CDATA[Methyl myristate C 14：0 > 0.9 0 <![CDATA[Methyl palmitate C 16：0 > 36.5 10.5 <![CDATA[Methyl stearate C 18：0 > 9.28 16.8 <![CDATA[Methyl oleate C 18：1 > 32.38 49.8 <![CDATA[Methyl linoleate C 1s：2 > 20.2 22.9 other 0.44 0

[0078] Step 2: Figure 1 In a reaction dish, molecular sieves are added to the bottom of the reaction dish, and immobilized lipase IM-100 is placed inside the 100-mesh stainless steel sieve sleeve and then installed inside the 100-mesh stainless steel sieve sleeve, and then neopentyl glycol, waste edible oil methyl ester after distillation in step 1 and methyl nonanoate are added. After the reaction is carried out for 84 hours at a temperature of 45° C. and a stirring speed of 120 rpm, the molecular sieves and immobilized lipase IM-100 are separated to obtain waste edible oil-nonanoic acid neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester after distillation; the molar ratio of neopentyl glycol to the waste edible oil methyl ester after distillation is 2.3:1; the amount of methyl nonanoate added is 15% of the mass of the waste edible oil methyl ester after distillation;

[0079] Step 3 and step 4, the waste edible oil-nonanoic acid neopentyl glycol diester obtained in step 2 is alkali-refined with NaOH (the amount of NaOH added is 1-2g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0080] The various properties of the waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid prepared in this embodiment, such as flash point, pour point, breakdown voltage, viscosity, etc., were tested according to ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 10 below.

[0081] Table 10 Physical and chemical properties of waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid obtained after distillation at 180℃

[0082]

[0083] Example 4

[0084] like Figures 1 to 3 As shown, the method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics comprises the following steps:

[0085] Step 1, distilling the waste edible oil methyl ester at a pressure of 0.1-0.3 mbar and a temperature of 180° C. to obtain the waste edible oil methyl ester after distillation, and the waste edible oil methyl ester before and after distillation was determined by GC-MS. The components of the waste edible oil methyl ester before and after distillation are shown in Table 9;

[0086] Step 2: Figure 1 In a reaction dish, molecular sieves are added to the bottom of the reaction dish, and immobilized lipase IM-100 is placed inside the 100-mesh stainless steel sieve sleeve and then installed inside the 100-mesh stainless steel sieve sleeve, and then neopentyl glycol, waste edible oil methyl ester after distillation in step 1 and methyl nonanoate are added. After the reaction is carried out for 84 hours at a temperature of 45° C. and a stirring speed of 120 rpm, the molecular sieves and immobilized lipase IM-100 are separated to obtain waste edible oil-nonanoic acid neopentyl glycol diester; wherein the molecular sieve is 5% of the total mass of the reaction substrate, and the amount of immobilized lipase IM-100 added is 4% of the mass of the waste edible oil methyl ester after distillation; the molar ratio of neopentyl glycol to the waste edible oil methyl ester after distillation is 2.3:1; the amount of methyl nonanoate added is 20% of the mass of the waste edible oil methyl ester after distillation;

[0087] Step 3 and step 4, the waste edible oil-nonanoic acid neopentyl glycol diester obtained in step 2 is alkali-refined by using NaOH (the amount of NaOH added is 1-2g), adsorbed (the adsorption is to add an adsorbent composed of basic alumina, 3A molecular sieve, silica gel and activated white clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption is 60min), vacuum dried (vacuum dried at 100Pa, 75°C for 48h), and filtered with a filter membrane (the filter membrane is a 0.25μm filter membrane) to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

[0088] The various properties of the waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid prepared in this embodiment, such as flash point, pour point, breakdown voltage, viscosity, etc., were tested according to ISO 2719, ISO 3016, IEC 60247, ISO 3104 and other standards. Some of the test results are shown in Table 11 below.

[0089] Table 11 Physical and chemical properties of waste cooking oil-nonanoic acid neopentyl glycol diester insulating liquid obtained after distillation at 180℃

[0090]

[0091] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics, characterized in that the steps include: Step 1, distilling waste edible oil methyl ester to obtain distilled waste edible oil methyl ester; Step 2, adding molecular sieves, immobilized lipase IM-100, neopentyl glycol, waste edible oil methyl ester and nonanoic acid methyl ester after distillation in step 1 into a reaction dish, and reacting for 72-96 hours at a temperature of 40-50° C. and a stirring speed of 120-130 rpm, separating the molecular sieves and immobilized lipase IM-100 to obtain waste edible oil-nonanoic acid neopentyl glycol diester; Step 3, measuring the acid value of the waste cooking oil-nonanoic acid neopentyl glycol diester obtained in step 2, and performing alkali refining with sodium hydroxide to meet the acid value standard of synthetic ester insulating oil; Step 4: After alkali refining in step 3, the waste edible oil-nonanoic acid neopentyl glycol diester is obtained, and adsorption, vacuum drying, and membrane filtration are performed to generate the waste edible oil-nonanoic acid neopentyl glycol diester insulating liquid.

2. The method for preparing an insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The distillation in step 1 is carried out at a pressure of 0.1-0.3 mbar and a temperature of 150-180°C.

3. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: In step 2, the molecular sieve accounts for 5% of the total mass of the reaction substrate.

4. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: In the step 2, the amount of immobilized lipase IM-100 added is 3-5% of the mass of waste edible oil methyl ester after distillation, and the immobilized lipase IM-100 is placed in the reaction vessel through a 100-mesh stainless steel sieve.

5. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: In the step 2, the molar ratio of neopentyl glycol to methyl ester alcohol of waste edible oil after distillation is 2.3-2.5:1; the amount of methyl nonanoate added is 5-20% of the mass of methyl ester of waste edible oil after distillation.

6. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The acid value measurement method in step 3 is: heating anhydrous ethanol to remove CO2, dropping alkaline blue 6B indicator, and titrating with 0.05 mol / L KOH solution to neutral to obtain an ethanol solution; then, mixing waste edible oil-nonanoic acid neopentyl glycol diester with the ethanol solution, and titrating with KOH solution until the solution changes from blue to light red; the acid value is calculated by the formula: A v It is the acid value, unit is MgKOH / g; M KOH is the molar mass of KOH; N is the concentration of KOH solution, unit is mol / L; V is the volume of KOH solution consumed, and G is the mass of a certain mass of waste edible oil-nonanoic acid neopentyl glycol diester taken out.

7. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The alkaline substance required for alkali refining in step 3 is NaOH, and the calculation formula for the amount of alkali used is: Among them A ve is the acid value of waste edible oil-nonanoic acid neopentyl glycol diester; m is the mass of waste edible oil-nonanoic acid neopentyl glycol diester produced; M NaOH and M KOH are the molar masses of NaOH and KOH, respectively.

8. The method for preparing insulating liquid for electrical equipment using waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The adsorption in step 4 is to add an adsorbent consisting of basic alumina, 3A molecular sieve, silica gel and activated clay in a mass ratio of 1:1:1:1, the added amount is 5% of the mass of the waste edible oil methyl ester after distillation, and the adsorption lasts for 60 minutes.

9. The method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The vacuum drying in step 4 is performed at 100 Pa and 75° C. for 48 hours.

10. The method for preparing insulating liquid for electrical equipment from waste edible oil methyl ester with improved pouring point characteristics according to claim 1, characterized in that: The filter membrane in step 4 is a 0.25 μm filter membrane.

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