Method for preparing polyol ester insulating oil based on recyclable catalyst

Abstract

The invention relates to a method for preparing polyol ester insulating oil based on a recyclable catalyst, and belongs to the technical field of insulating oil preparation. A catalyst used in the preparation method provided by the invention is metal oxide or cation exchange resin loaded with active ions; the active ions in the metal oxide loaded with the active ions are selected from S2O8 < 2-> and PO4 < 3->; the metal oxide is selected from a ZrO2-Fe3O4 compound (the molar ratio of ZrO2 to Fe3O4 is 1: (1-3)) or Al2O3; the cation exchange resin is selected from sulfonic group macroporous polystyrene ion exchange resin and sulfonic group styrene-divinylbenzene copolymer ion exchange resin. By adopting the preparation method provided by the invention, a crude product with a light color can be obtained, the reaction, washing and purification are simple, the catalyst can be continuously used for multiple times after being filtered after being used, the high catalytic efficiency is maintained, and the method has high environmental friendliness and important industrial economic value.

Description

Technical Field

[0001] The invention relates to the technical field of preparing insulating oil, and in particular to a method for preparing polyol ester insulating oil based on a recyclable catalyst. Background Art

[0002] As the key insulating medium for oil-filled power equipment such as transmission transformers, insulating oil plays important functions such as electrical insulation, heat dissipation and as a fault diagnosis carrier. Its performance determines the operating level of oil-filled power equipment. The insulating oils widely used in power systems mainly include mineral oil and natural ester insulating oil. Traditional mineral oil has a wide range of sources, low viscosity and pour point, but has disadvantages such as low flash point and ignition point and difficulty in degradation; natural ester insulating oil has high flame retardancy and is green and environmentally friendly, but still has problems such as poor antioxidant performance, easy aging, and high pour point, which restricts the application and promotion of natural ester insulating oil in power transformers.

[0003] Prepared polyol ester insulating oil is a new generation of green and efficient insulating oil, which takes into account the advantages of low viscosity, low pour point, high aging resistance and flame retardant properties, significantly improves the antioxidant properties of ester insulating oil, and successfully solves the problems of poor oxidation stability of natural ester insulating oil. Midel prepared ester insulating oil produced by Siemens Transformer Company is a typical representative of prepared polyol ester insulating oil. It is an environmentally friendly transformer insulating oil with a high flash point (above 300°C, much higher than traditional mineral oil); the biggest advantage is its flame retardancy and self-extinguishing properties, which are more reliable than high flash point hydrocarbon oil or similar products in fire safety. At present, it is still difficult to produce comparable polyol ester prepared insulating oil in China.

[0004] In 2021, Han Qiuhuang et al. studied a method for preparing low-viscosity diester insulating oil using enzyme catalysis technology and adsorption purification process. However, the enzyme catalysis technology has a low yield, a long reaction time, and complex process technology, which makes it difficult to meet the current economic efficiency requirements of mass production of transformer insulating oil; in 2022, Yao Jiachen et al. reported a method for preparing low pour point pentaerythritol ester insulating oil. The preparation yield of pentaerythritol ester can reach 98%. However, this method requires the use of a strong organic acid as a catalyst, the purification operation is cumbersome, and only small-scale experimental research has been completed in the laboratory.

[0005] Therefore, developing new organic preparation methods to establish efficient preparation technology for polyol ester insulating oil and simplifying the related purification process are key scientific and technological problems that need to be solved urgently in order to achieve breakthroughs in the production technology of power transformer insulating oil. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing polyol ester insulating oil based on a recyclable catalyst. The preparation method of the present invention is based on a recyclable solid catalyst, the obtained crude product has high quality, the catalyst is recyclable and has high recycling efficiency, and has environmental friendliness and high industrial value.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a method for preparing polyol ester insulating oil based on a recyclable catalyst, comprising the following steps:

[0009] (1) mixing a polyol, a fatty acid and a catalyst, heating for reaction, and filtering to obtain a crude product;

[0010] (2) decolorizing and purifying the crude product to obtain the polyol ester insulating oil;

[0011] The catalyst is a metal oxide or a cation exchange resin loaded with active ions;

[0012] In the metal oxide loaded with active ions, the active ions are S 2 O 8 2- ,PO 4 3- At least one of the metal oxides is ZrO 2 -Fe 3 O 4 Composite or Al 2 O 3 ; the ZrO 2 -Fe 3 O 4 In the composite, ZrO 2 with Fe 3 O 4 The molar ratio is 1:(1-3);

[0013] The cation exchange resin is at least one of a sulfonic acid macroporous polystyrene ion exchange resin and a sulfonic acid styrene-divinylbenzene copolymer ion exchange resin.

[0014] The present invention develops and establishes a highly efficient synthesis preparation method of polyol ester insulating oil based on a recyclable two-phase catalyst: polyol, fatty acid and catalyst are mixed, heated to carry out esterification reaction, the filter residue obtained by filtration is the catalyst that can be recovered and recycled, the filtrate is the crude product, and the crude product is further purified to obtain the polyol ester insulating oil product.

[0015] The present invention optimizes the types of catalysts used, and selects catalysts with high catalytic efficiency, recyclability, and the ability to maintain high catalytic efficiency after recycling. The specific types are selected from macroporous acidic cation exchange resins or active catalysts with specific strong acid radical ions loaded on specific solid phases. The above-mentioned specific two-phase catalyst is selected to realize the recycling of the catalyst, significantly simplify the subsequent separation and purification process, improve the quality of crude insulating oil, greatly save production costs, and increase benefits.

[0016] By adopting the preparation method of the present invention, the catalyst can be recycled for more than 5 times after filtering, and can still maintain efficient catalytic performance and high product yield, significantly reducing the amount of strong acid used in the production process of polyol esters; the method also effectively reduces the corrosion of free strong acid to equipment, reduces the requirements of production and processing for equipment and the danger of operation. At the same time, the preparation method provided by the present invention can achieve complete separation of the catalyst and the product through simple filtration, which solves the problem of using a large amount of alkali solution for neutralization and repeated removal of free strong acids such as benzenesulfonic acid, sulfuric acid, methanesulfonic acid, aminosulfonic acid, etc. in the traditional method, greatly simplifies the production process and reduces environmental pollution and production costs.

[0017] At the same time, the preparation method provided by the present invention filters and removes the acid catalyst in advance, and the washing step of the filtrate only requires the simple use of a weak base (the traditional method uses sodium hydroxide) to achieve the removal of the acid, and then the crude product can be obtained by separating the upper oil layer, so that the subsequent purification method is more green and safe; and the color of the polyol ester crude product obtained after washing is light yellow or light brown, the quality and purity of the crude product are high, and the subsequent decolorization and purification are more convenient; in contrast, the crude product prepared by using a catalyst such as sulfuric acid or benzenesulfonic acid in the traditional method is darker dark yellow-brown or yellow-brown.

[0018] In summary, the method for preparing polyol ester insulating oil based on a recyclable catalyst provided by the present invention has high production efficiency and high raw material utilization rate, the product has advanced performance, and the method is environmentally friendly and has important industrial economic value.

[0019] The types of the polyols include pentaerythritol and trimethylolethane, the types of the fatty acids include nonanoic acid and heptanoic acid, and the types of the polyol ester insulating oils include pentaerythritol tetranonanoate insulating oil, trimethylolethane-tripnonanoate insulating oil, and pentaerythritol tetraheptanoate insulating oil.

[0020] Preferably, the metal oxide loaded with active ions is loaded with S 2 O 8 2- ZrO 2 -Fe 3 O 4 Complex.

[0021] More preferably, the ZrO 2 -Fe 3 O 4 In the composite, ZrO 2 with Fe 3 O 4 The molar ratio is 1:2.

[0022] Further preferably, the load S 2 O 8 2- ZrO 2 -Fe 3 O 4 The preparation method of the complex is as follows:

[0023] S1. Add polyethylene glycol and magnetic-based ferrosoferric oxide to the zirconium chloride solution, mix and heat to 60-70°C, adjust the pH to 11-13, react, cool and filter to obtain a solid, which is the ZrO 2 -Fe 3 O 4 Complex;

[0024] S2. Soaking the ZrO in ammonium persulfate solution 2 -Fe 3 O 4 The composite is adsorbed to saturation, and then dried and calcined to obtain the loaded S 2 O 8 2- ZrO 2 -Fe 3 O 4 Complex.

[0025] More preferably, the calcination is: calcination at 400° C. for 3 h.

[0026] Further preferably, in said S2, the ammonium persulfate in the ammonium persulfate solution and the ZrO 2 -Fe 3 O 4 Fe in the complex 3 O 4 The molar ratio is 1:(0.1-0.3).

[0027] In the preparation method of the present invention, the load S with a preferred ratio prepared by a specific method is selected 2 O 8 2- ZrO 2 -Fe 3 O 4The composite has good catalytic effect and high preparation yield in the initial use process. After being repeatedly used for more than 5 times, it can still maintain a yield of more than 85% for the preparation of pentaerythritol tetranonanoate, and the catalytic effect is significantly better than the cyclic catalytic effect of other active ions or carrier combinations.

[0028] Preferably, the cation exchange resin is sulfonic acid macroporous polystyrene ion exchange resin Amberlyst-15.

[0029] Amberlyst-15 is selected as a specific catalyst in the cation exchange resin type catalyst and used in the preparation method of the present invention, which has very excellent cyclic catalytic performance: after being repeatedly recycled for more than 5 times, it can continue to be used to prepare different polyol ester insulating oils, and the product yield can still be maintained at more than 91%, the catalytic effect is good, and the raw material utilization rate is high.

[0030] Preferably, in step (1), the heating reaction temperature is 120-160° C., and the reaction time is 24-36 hours.

[0031] Preferably, in the step (1), after filtration, the filtrate is washed three times with saturated sodium bicarbonate, and the upper oil layers are recovered and combined to obtain the crude product.

[0032] Preferably, in step (2), the decolorization and purification is performed by adding SiO 2 、Na 2 SO 4 、Al 2 O 3 Reaction; the SiO 2 、Na 2 SO 4 、Al 2 O 3 The mass ratio is (4-6):(1-3):(1-3).

[0033] More preferably, the temperature of the decolorization and purification reaction is 80° C. and the time is 1 h.

[0034] The crude product prepared by the preparation method of the present invention has high quality and light color, and the subsequent decolorization and purification steps are simple, thereby achieving green preparation, reducing raw material loss, and saving energy.

[0035] Preferably, the method for preparing polyol ester insulating oil based on a recyclable catalyst further comprises recycling the catalyst, the steps being as follows:

[0036] The filtered residue is used as a catalyst to repeat the mixing reaction and filtering in step (1) to achieve the recycling of the catalyst.

[0037] More preferably, the catalyst is recycled ≥5 times.

[0038] The method for preparing polyol ester insulating oil based on a recyclable catalyst provided by the present invention can achieve high material utilization, high product yield, and the catalyst can be completely recovered and reused after simple filtration. The preferred catalyst type can also achieve repeated preparation using the recovered catalyst alone while maintaining a high yield. After continuous circulation to reach a certain catalyst activity loss, the catalytic efficiency can be improved by combining with a newly prepared catalyst, thereby comprehensively achieving a green preparation process that significantly reduces the use of strong acid preparations.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a method for preparing polyol ester insulating oil based on a recyclable catalyst by optimizing the types of catalysts used in preparing polyol ester insulating oil and simplifying the preparation steps: the catalyst can be recycled and reused many times, the raw material utilization rate is high, the washing step is simple, the crude product is of high quality, the decolorization and purification steps are significantly simplified, and high product yield and high production efficiency are comprehensively achieved; by selecting a catalyst with strong cyclic catalytic stability, it can be recycled and reused many times, the use of strong acid in the process is significantly reduced, and the corrosion of free acid to equipment is reduced, a large amount of production cost is saved as a whole, production safety is improved, and the product quality is excellent, and it has both environmental friendliness and high industrial value. DETAILED DESCRIPTION

[0041] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below in conjunction with specific examples. The test methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0042] In the following embodiments and comparative examples, the catalyst is obtained as follows:

[0043] The sulfonic acid macroporous polystyrene ion exchange resin Amberlyst-15, sulfonic acid styrene-divinylbenzene copolymer ion exchange resin D001 and PO 4 3- / Al 2 O 3 (Load PO 4 3- Al 2 O 3 ) was purchased from Anaiji Chemical Co., Ltd.;

[0044] The load S 2 O 8 2- ZrO2 -Fe 3 O 4 Complex (S 2 O 8 2- / ZrO 2 -Fe 3 O 4 ) is prepared as follows:

[0045] S1. Weigh 2.33g of anhydrous zirconium chloride into a 100mL round-bottom flask, add 50mL of distilled water, and stir thoroughly to dissolve it completely. Then add 15mL of polyethylene glycol and 4.66g of magnetic-based ferroferric oxide into the solution system at one time. After the reaction system is magnetically stirred thoroughly, heat it to 65°C. At the same time, slowly add ammonia water to control the pH value between 11-13. Continue to stir the reaction at this temperature for 3h, and then let it stand. After cooling to room temperature, filter the target filter cake by pressure filtration, and use 30mL of deionized water to wash it thoroughly to obtain ZrO 2 -Fe 3 O 4 Composite solid.

[0046] S2. ZrO 2 -Fe 3 O 4 The composite solid was soaked in 200 mL of 0.5 N ammonium persulfate solution for 24 h, taken out and placed in an electric constant temperature blast drying oven at 120 ° C for drying, calcined at 400 ° C for 3 h, and placed in a dryer for natural cooling to obtain a catalyst-loaded S 2 O 8 2- ZrO 2 -Fe 3 O 4 Composite, in which ZrO 2 with Fe 3 O 4 The molar ratio is 1:2 (S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 ).

[0047] The above-mentioned preparation steps S1 and S2 were used, but the amount of magnetic-based ferroferric oxide in S1 was changed to 2.33 g and 6.99 g respectively to obtain ZrO 2 with Fe 3 O 4 The molar ratio of S was 1:1 and 1:3. 2 O 8 2- ZrO2 -Fe 3 O 4 Complex (S 2 O 8 2- / 1:1ZrO 2 -Fe 3 O 4 , S 2 O 8 2- / 1:3ZrO 2 -Fe 3 O 4 )

[0048] Example 1

[0049] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following steps:

[0050] (1) Weighing compounds of pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) into a double-necked flask, then adding 1 g of Amberlyst-15, using a Dean-Stark apparatus, reacting under reduced pressure at 130° C. for 24 h, cooling to room temperature after the reaction, and then filtering with a sand core funnel, recovering the filter residue as the catalyst Amberlyst-15, washing the filtrate with 30 mL of saturated sodium bicarbonate for 3 times, and recovering the upper oil layer to obtain a light yellow crude product - pentaerythritol tetranonanoate insulating oil (purity greater than 98%);

[0051] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1h to obtain 50.2g of colorless pentaerythritol tetranonanoate insulating oil (yield 96.0%).

[0052] Example 2

[0053] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0054] (1) Weighing compounds of pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then adding 1 g of D001, using a Dean-Stark apparatus, reacting under reduced pressure at 140° C. for 36 h, cooling to room temperature after the reaction, and then filtering with a sand core funnel, recovering the filter residue as catalyst D001, washing the filtrate with 30 mL of saturated sodium bicarbonate for 3 times, and recovering the upper oil layer to obtain a light yellow crude product - pentaerythritol tetranonanoate insulating oil (purity greater than 97%);

[0055] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1h to obtain 49.5g of colorless pentaerythritol tetranonanoate insulating oil (yield 94.8%).

[0056] Example 3

[0057] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0058] (1) Weigh pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) into a double-necked flask, then add 1 g of loaded PO 4 3- Activated Alumina PO 4 3- / Al 2 O 3 , using a Dean-Stark apparatus, 160°C under reduced pressure for 36 hours, cooling to room temperature after the reaction, and then filtering with a sand core funnel to recover the filter residue as catalyst PO 4 3- / Al 2 O 3 The filtrate was washed three times with 30 mL of saturated sodium bicarbonate, and the upper oil layer was recovered to obtain a nearly colorless crude product - pentaerythritol tetranonanoate insulating oil (purity greater than 95%);

[0059] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1h to obtain 47.6g of colorless pentaerythritol tetranonanoate insulating oil (yield 91%).

[0060] Example 4

[0061] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0062] (1) Weigh pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then add 1 g of S-loaded 2 O 8 2- ZrO 2 -Fe 3 O 4 Complex (S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 ), using a Dean-Stark apparatus, reacting under reduced pressure at 120°C for 24 hours, cooling to room temperature after the reaction, and then filtering using a sand core funnel to recover the filter residue as catalyst S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 The filtrate was washed three times with 30 mL of saturated sodium bicarbonate, and the upper oil layer was recovered to obtain a yellow-brown crude product - pentaerythritol tetranonanoate insulating oil (purity greater than 99%);

[0063] (2) Add the crude product into a round-bottom flask and add 10 g SiO 2 , 5g Na 2 SO 4 、5gAl 2 O 3 , react at 80°C for 1h to obtain 48.5g of light yellow pentaerythritol tetranonanoate insulating oil (yield 92.7%).

[0064] Example 5

[0065] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention, the specific steps are different from those of Example 4 only in that the catalyst in step (1) is replaced by S with different molar ratios of carriers. 2 O 8 2- / 1:3ZrO 2 -Fe 3 O 4 .

[0066] The crude product yellow-brown pentaerythritol tetranonanoate insulating oil obtained in step (1) has a purity greater than 92%; and step (2) obtains 47.5 g of light yellow pentaerythritol tetranonanoate insulating oil (yield 91.1%).

[0067] Example 6

[0068] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0069] (1) Weighing the compounds trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then adding 1 g of Amberlyst-15, using a Dean-Stark apparatus, reacting under reduced pressure at 130° C. for 24 h, cooling to room temperature after the reaction, and then filtering with a sand core funnel, recovering the filter residue as the catalyst Amberlyst-15, washing the filtrate with 30 mL of saturated sodium bicarbonate for 3 times, and recovering the upper oil layer to obtain a light yellow crude trimethylolethane-trinonanoic acid ester insulating oil (purity greater than 98%);

[0070] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1h to obtain 51.9g of colorless trimethylolethane-tripelanate insulating oil (yield 95.9%).

[0071] Example 7

[0072] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0073] (1) Weighing the compounds trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then adding 1 g of D001, using a Dean-Stark apparatus, reacting under reduced pressure at 140° C. for 36 h, cooling to room temperature after the reaction, and then filtering with a sand core funnel, recovering the filter residue as catalyst D001, washing the filtrate with 30 mL of saturated sodium bicarbonate for 3 times, and recovering the upper oil layer to obtain a light yellow crude trimethylolethane-tris nonanoic acid ester insulating oil (purity greater than 97%);

[0074] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3, react at 80°C for 1 hour to obtain 50.3 g of colorless trimethylolethane-tripelanate insulating oil (yield 93.3%).

[0075] Example 8

[0076] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0077] (1) Weigh trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then add 1 g of loaded PO 4 3- Activated Alumina PO 4 3- / Al 2 O 3 , using a Dean-Stark apparatus, 160°C under reduced pressure for 36 hours, cooling to room temperature after the reaction, and then filtering with a sand core funnel to recover the filter residue as catalyst PO 4 3- / Al 2 O 3 The filtrate was washed three times with 30 mL of saturated sodium bicarbonate, and the upper oil layer was recovered to obtain a crude trimethylolethane-tripelanate insulating oil (with a purity greater than 97%) of approximately light yellow color;

[0078] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1 hour to obtain 48.3 g of colorless trimethylolethane-tripelanate insulating oil (yield 89.3%).

[0079] Example 9

[0080] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0081] (1) Weigh trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, then add 1 g of S-loaded 2 O 8 2- ZrO 2 -Fe 3 O 4 Complex (S 2 O 8 2- / 1:2ZrO 2 -Fe3 O 4 ), using a Dean-Stark apparatus, reacting under reduced pressure at 120°C for 24 hours, cooling to room temperature after the reaction, and then filtering using a sand core funnel to recover the filter residue as catalyst S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 The filtrate was washed three times with 30 mL of saturated sodium bicarbonate, and the upper oil layer was recovered to obtain yellow-brown trimethylolethane-tripelanate insulating oil (purity greater than 93%);

[0082] (2) Add the crude product into a round-bottom flask and add 10 g SiO 2 , 5g Na 2 SO 4 、5gAl 2 O 3 , react at 80°C for 1 hour to obtain 47.1 g of light yellow trimethylolethane-tripelanate insulating oil (yield 87.1%).

[0083] Example 10

[0084] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention, the specific steps are different from those of Example 9 only in that the catalyst in step (1) is replaced by S with different molar ratios of carriers. 2 O 8 2- / 1:3ZrO 2 -Fe 3 O 4 .

[0085] The crude product yellow-brown trimethylolethane-tris nonanoate insulating oil obtained in step (1) has a purity greater than 87%; and step (2) obtains 46.6 g of light yellow trimethylolethane-tris nonanoate insulating oil (yield 86.3%).

[0086] Embodiment 11

[0087] An embodiment of the method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention comprises the following specific steps:

[0088] (1) Weighing compounds of pentaerythritol (9.75 g, 0.075 mol) and heptanoic acid (39.1 g, 0.3 mol) into a double-necked flask, then adding 1 g of Amberlyst-15, using a Dean-Stark apparatus, reacting under reduced pressure at 130° C. for 24 h, cooling to room temperature after the reaction, and then filtering using a sand core funnel, recovering the filter residue as the catalyst Amberlyst-15, washing the filtrate with 30 mL of saturated sodium bicarbonate for 3 times, and recovering the upper oil layer to obtain a light yellow crude product - pentaerythritol tetraheptanoate insulating oil (purity greater than 96%);

[0089] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1h to obtain 41.2g of colorless pentaerythritol tetraheptanoate insulating oil (yield 94.1%).

[0090] Example 12

[0091] The difference between Example 12 and Example 4 is that the catalyst in step (1) is replaced by S with different carrier molar ratios. 2 O 8 2- / 1:1ZrO 2 -Fe 3 O 4 .

[0092] The crude product yellow-brown pentaerythritol tetranonanoate insulating oil obtained in step (1) has a purity greater than 92%; and step (2) obtains 45.6 g of light yellow pentaerythritol tetranonanoate insulating oil (yield 87.1%).

[0093] Embodiment 13

[0094] The difference between Example 13 and Example 9 is that the catalyst in step (1) is replaced by S with different carrier molar ratios. 2 O 8 2- / 1:1ZrO 2 -Fe 3 O 4 .

[0095] The crude product yellow-brown trimethylolethane-tripranoate insulating oil obtained in step (1) has a purity greater than 87%; and step (2) obtains 44.7 g of light yellow trimethylolethane-tripranoate insulating oil (yield 82.8%).

[0096] Comparative Example 1

[0097] Comparative Example 1 is a method for synthesizing pentaerythritol tetranonanoate insulating oil using sulfuric acid as a catalyst, and the steps are as follows:

[0098] (1) Weighing compounds of pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, adding 0.25 mL of sulfuric acid, using a Dean-Stark apparatus, reacting under reduced pressure at 130° C. for 6 h, cooling to room temperature after the reaction, and then using 10 mL of 0.1N sodium hydroxide aqueous solution to neutralize the sulfuric acid, and then using 30 mL of saturated sodium bicarbonate to wash three times, recovering the upper oil layer to obtain a dark brown crude product - pentaerythritol tetranonanoate insulating oil (purity of about 91%);

[0099] (2) Add the crude product into a round-bottom flask and add 10 g SiO 2 , 5g Na 2 SO 4 、5gAl 2 O 3 , react at 80°C for 1h to obtain 45.7 light yellow pentaerythritol tetranonanoate insulating oil (yield 87.6%).

[0100] Comparative Example 2

[0101] Comparative Example 2 is a method for synthesizing trimethylolethane-tripelanate insulating oil using sulfuric acid as a catalyst, and the steps are as follows:

[0102] (1) Weigh the compounds trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) into a two-necked flask, and then add 0.25 mL of sulfuric acid. Use a Dean-Stark apparatus, react under reduced pressure at 130°C for 6 h, cool to room temperature after the reaction, and then use 10 mL of 0.1N sodium hydroxide aqueous solution to neutralize the sulfuric acid, and then use 30 mL of saturated sodium bicarbonate to wash 3 times, and recover the upper oil layer to obtain a dark brown crude product - pentaerythritol tetranonanoate insulating oil (purity 93%).

[0103] (2) Add the crude product into a round-bottom flask and add 10 g SiO 2 , 5g Na 2 SO 4 、5gAl 2 O 3 , react at 80°C for 1 hour to obtain 49.1 g of light yellow trimethylolethane-tripelanate insulating oil (yield 90.9%).

[0104] Comparative Example 3

[0105] Comparative Example 3 is a method for synthesizing pentaerythritol tetranonanoate insulating oil using p-toluenesulfonic acid as a catalyst, and the steps are as follows:

[0106] (1) Weigh the compounds pentaerythritol (9.75 g, 0.075 mol) and nonanoic acid (47.5 g, 0.3 mol) and add them into a two-necked flask, then add p-toluenesulfonic acid (0.75 mmol, 129 mg). Use a Dean-Stark apparatus and react under reduced pressure at 130°C for 6 hours. After the reaction is completed, cool to room temperature, then use 10 mL of 0.1N sodium hydroxide aqueous solution to neutralize the p-toluenesulfonic acid, and then use 30 mL of saturated sodium bicarbonate to wash 3 times, and recover the upper oil layer to obtain a dark brown crude product - pentaerythritol tetranonanoate insulating oil (purity about 91%);

[0107] (2) Add the crude product into a round-bottom flask and add 10 g SiO 2 , 5g Na 2 SO 4 、5gAl 2 O 3 , react at 80°C for 1h to obtain 48.8g of light yellow pentaerythritol tetranonanoate insulating oil (yield 93.5%).

[0108] Comparative Example 4

[0109] Comparative Example 4 is a method for synthesizing trimethylolethane-tripelanate insulating oil using p-toluenesulfonic acid as a catalyst, and the steps are as follows:

[0110] (1) Weigh the compound trimethylolethane (12.0 g, 0.1 mol) and nonanoic acid (47.5 g, 0.3 mol) and add them into a double-necked flask, then add p-toluenesulfonic acid (0.75 mmol, 172 mg). Use a Dean-Stark apparatus and react under reduced pressure at 130°C for 6 h; after the reaction is completed, cool to room temperature, then use 10 mL of 0.1N sodium hydroxide aqueous solution to neutralize the p-toluenesulfonic acid, then wash with 30 mL of saturated sodium bicarbonate for 3 times, and recover the upper oil layer to obtain a yellow-brown crude product - trimethylolethane-tripelanate insulating oil (purity is 93%);

[0111] (2) Add the crude product into a round-bottom flask and add 5 g SiO 2 , 2g Na 2 SO 4 , 2g Al 2 O 3 , react at 80°C for 1 hour to obtain 49.6 g of light yellow trimethylolethane-tripelanate insulating oil (yield 91.8%).

[0112] Effect Example 1

[0113] In order to explore the preparation effect of the method for preparing polyol ester insulating oil based on recyclable catalyst provided by the present invention, the yield, product appearance, crude product appearance and recyclability of the catalyst of polyol ester insulating oil prepared by different preparation methods in the comparative examples and comparative examples are compared. The results are shown in Tables 1-1 to 1-2 below.

[0114] From the comparison of Tables 1-1 and 1-2, we can see that:

[0115] Combined with the above reaction conditions, it can be seen that in the method for preparing polyol ester insulating oil based on recyclable catalyst provided in the embodiment, the catalytic efficiency of each catalyst for the first preparation reaction is ranked from high to low: Amberlyst-15≈S 2 O 8 2- / 1:(2-3)ZrO 2 -Fe 3 O 4 >D001>PO 4 3- / Al 2 O 3 ; In Examples 4-5, 9-10, S is loaded 2 O 8 2- ZrO 2 -Fe 3 O 4 Under the ratio of the complex, the catalytic efficiency is high;

[0116] At the same time, the catalytic effect of the embodiment is compared with the traditional sulfuric acid (reaction time 6h, yield 87.6% and 90.9%) or p-toluenesulfonic acid (reaction time 12h, 93.5% and 91.8%) in the comparative example. Although the reaction time is prolonged, the yield obtained by using the catalyst Amberlyst-15 is relatively higher (96.0% and 95.9%). It can be seen from the physical properties of the product that compared with traditional sulfuric acid (dark brown) and p-toluenesulfonic acid (yellow brown), the method for preparing polyol ester insulating oil based on recyclable catalyst of the present invention has a higher catalytic yield when Amberlyst-15 is selected as the catalyst;

[0117] Moreover, by adopting the preparation strategy of the present invention, the crude product obtained has lighter color, higher purity and better quality, and the subsequent purification and decolorization are easier. By adopting the same decolorization treatment, the color of the product is colorless or light yellow, and the quality is higher than that of the traditional method. At the same time, the preparation method does not need to use strong alkali sodium hydroxide to neutralize the acidic environment of the product, thereby reducing the complicated process of post-treatment of the waste liquid.

[0118] Table 1-1 Effects of different methods for preparing pentaerythritol tetranonanoate insulating oil

[0119]

[0120]

[0121] Table 1-2 Effects of different methods for preparing trimethylolethane-trispelargonate insulating oil

[0122] catalyst Yield Product appearance Appearance of crude product Catalyst recycling Example 6 Amberlyst-15 95.9％ colorless Light yellow Recyclable Example 7 D001 93.3％ colorless Light yellow Recyclable Example 8 <h2 style=";text-align:left;direction:ltr"><![CDATA[PO <h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> 3- <h2 style=";text-align:left;direction:ltr"> / Al<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 89.3％ colorless Almost colorless Recyclable Example 9 <![CDATA[S 2 O 8 2- / 1:2ZrO 2 -Fairy 3 O 4 ]]> 87.1％ Light yellow Yellowish brown Recyclable Example 10 <![CDATA[S 2 ISLAND 8 2- / 1:3ZrO 2 -Fairy 3 ISLAND 4 ]]> 86.3％ Light yellow Yellowish brown Recyclable Embodiment 13 <![CDATA[S 2 EITHER 8 2- / 1:1ZrO 2 -Faith 3 EITHER 4 ]]> 82.8％ Light yellow Yellowish brown Recyclable Comparative Example 2 sulfuric acid 90.9％ Light yellow Dark Brown Not recyclable Comparative Example 4 p-Toluenesulfonic acid 91.8％ Light yellow Dark Brown Not recyclable

[0123] Effect Example 2

[0124] In order to explore the recycling effect of the catalyst recovered in the method for preparing polyol ester insulating oil based on a recyclable catalyst provided by the present invention in the preparation method provided by the present invention, the filter residue recovered by filtration in step (1) of Examples 1-4 and Example 6 was used as a catalyst and reused in the method for preparing polyol ester insulating oil based on a recyclable catalyst corresponding to each example. The number of catalyst cycles, reaction time and product yield are shown in Tables 2-1 to 2-5.

[0125] From Tables 2-1 to 2-5, we can see that:

[0126] The method for preparing polyol ester insulating oil based on a recyclable catalyst of the present invention is adopted, and the catalyst Amberlyst-15, D001, S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 ,PO 4 3- / Al 2 O 3 Both Amberlyst-15 and S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 Compared with other catalysts, it has a more outstanding recycling effect and can maintain a high catalytic efficiency even when it is recycled up to 5 times. It will have significant economic benefits in the production application process and greatly reduce production costs.

[0127] Table 2-1 Cycle efficiency of pentaerythritol tetranonanoate insulating oil prepared by Amberlyst-15 catalysis

[0128] Cycle times 1 2 3 4 5 Reaction time (h) 24 24 28 36 36 Yield 95.5％ 94.2％ 94.7％ 95.1％ 93.4％

[0129] Table 2-2 Cycle efficiency of trimethylolethane-trispelargonate insulating oil prepared by Amberlyst-15 catalysis

[0130] Cycle times 1 2 3 4 5 Reaction time (h) 24 24 24 28 36 Yield 95.6％ 94.4％ 91.8％ 94.9％ 94.1％

[0131] Table 2-3S 2 O 8 2- / 1:2ZrO 2 -Fe 3 O 4 Cycle efficiency of insulating oil prepared by catalytic preparation of pentaerythritol tetranonanoate

[0132] Cycle times 1 2 3 4 5 Reaction time (h) 24 24 28 28 36 Yield 92.6％ 91.7％ 90.2％ 85.6％ 90.4％

[0133] Table 2-4PO 4 3- / Al 2 O 3 Cycle efficiency of insulating oil prepared by catalytic preparation of pentaerythritol tetranonanoate

[0134] Cycle times 1 2 3 4 5 Reaction time (h) 36 36 48 72 72 Yield 87.6％ 86.5％ 78.3％ 79.2％ 65.2％

[0135] Table 2-5 Cycle efficiency of D001 catalytic preparation of pentaerythritol tetranonanoate insulating oil

[0136] Cycle times 1 2 3 4 5 Reaction time (h) 24 24 24 28 72 Yield 90.9％ 89.5％ 83.8％ 81.2％ 91.8％

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing polyol ester insulating oil based on a recyclable catalyst, characterized in that: The following steps are involved: (1) mixing a polyol, a fatty acid and a catalyst, heating for reaction, and filtering to obtain a crude product; (2) decolorizing and purifying the crude product to obtain the polyol ester insulating oil; The catalyst is a metal oxide or a cation exchange resin loaded with active ions; In the metal oxide loaded with active ions, the active ions are S2O8 2- PO4 3- At least one of the metal oxides is a ZrO2-Fe3O4 complex or Al2O3; in the ZrO2-Fe3O4 complex, the molar ratio of ZrO2 to Fe3O4 is 1:(1-3); The cation exchange resin is at least one of a sulfonic acid macroporous polystyrene ion exchange resin and a sulfonic acid styrene-divinylbenzene copolymer ion exchange resin.

2. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 1, characterized in that: The metal oxide loaded with active ions is loaded with S2O8 2- ZrO2-Fe3O4 composite.

3. The method for preparing polyol ester insulating oil based on a recyclable catalyst as claimed in claim 2, characterized in that: In the ZrO2-Fe3O4 composite, the molar ratio of ZrO2 to Fe3O4 is 1:

2.

4. The method for preparing polyol ester insulating oil based on a recyclable catalyst as claimed in claim 2, characterized in that: The loaded S2O8 2- The preparation method of the ZrO2-Fe3O4 composite is as follows: S1. Add polyethylene glycol and magnetic-based ferrosoferric oxide to the zirconium chloride solution, mix and heat to 60-70 ° C, adjust the pH to 11-13, react, cool and filter to obtain a solid, which is the ZrO2-Fe3O4 complex; S2. Soak the ZrO2-Fe3O4 composite in ammonium persulfate solution, adsorb to saturation, and then dry and calcine to obtain the loaded S2O8 2- ZrO2-Fe3O4 composite.

5. The method for preparing polyol ester insulating oil based on a recyclable catalyst as claimed in claim 4, characterized in that: In the S2, the molar ratio of ammonium persulfate in the ammonium persulfate solution to Fe3O4 in the ZrO2-Fe3O4 composite is 1:(0.1-0.3).

6. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 1, characterized in that: The cation exchange resin is sulfonic acid macroporous polystyrene ion exchange resin Amberlyst-15.

7. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 1, characterized in that: In the step (1), the heating reaction temperature is 120-160° C., and the reaction time is 24-36 hours.

8. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 1, characterized in that: In the step (2), the decolorization and purification is performed by adding SiO2, Na2SO4, and Al2O3 for reaction; the mass ratio of SiO2, Na2SO4, and Al2O3 is (4-6):(1-3):(1-3).

9. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 1, characterized in that: The catalyst is also recycled, the steps are as follows: The filtered residue is used as a catalyst to repeat the mixing reaction and filtering in step (1) to achieve the recycling of the catalyst.

10. The method for preparing polyol ester insulating oil based on a recyclable catalyst according to claim 9, characterized in that: The catalyst can be recycled ≥5 times.

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