Preparation of a catalyst and its use in the production of medium-chain triglycerides

Abstract

The application discloses a kind of preparation of catalyst and its application in medium chain triglyceride preparation, it is related to organic synthesis technical field, comprising the following steps: γ-alumina, silica gel is added to organic solvent, stirring is dispersed uniformly, heating reflux, obtains catalyst precursor;Leaching, suction filtration removes organic solvent in catalyst precursor, obtains catalyst filter cake;Catalyst filter cake is heated and calcined, obtains catalyst.Further, the preparation process of the catalyst also includes the following steps: catalyst filter cake is heated and calcined, after heating and calcining, catalyst filter cake is carried out p-toluenesulfonic acid load processing, obtains catalyst.The catalyst preparation method of the application is simple, reduces the hydroxyl value of product in the preparation of catalytic medium chain triglyceride, shortens reaction time simultaneously, reduces reaction temperature, improves the yield of medium chain triglyceride.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to the preparation of a catalyst and its application in the preparation of medium-chain triglycerides. Background Technology

[0002] Medium-chain triglycerides (MCTs) are fatty acid glycerides produced by the reaction of glycerol with medium-chain fatty acids. Due to their unique advantages such as rapid oxidative energy supply, independence from carnitine transport, and low metabolic burden, they are widely used in special medical purpose foods, infant formula, sports nutrition products, and pharmaceutical solubilizers. Currently, the industrial production of MCTs mainly falls into two categories: natural extraction and chemical synthesis. Natural extraction uses coconut oil and palm kernel oil as raw materials, obtaining MCT products through processes such as hydrolysis, fractionation, and molecular distillation. However, this method is limited by the source of raw materials, the fatty acid composition ratio in the product is fixed and difficult to control, and the separation and purification process is lengthy, energy-intensive, and results in limited product yield.

[0003] Chemical synthesis has become the mainstream route for the production of medium-chain triglycerides due to its advantages such as a wide range of raw material sources and flexible control over fatty acid composition. However, existing chemical synthesis methods still have technical shortcomings in terms of catalyst selection and process control.

[0004] Patent CN109836328A uses methyl sulfonate as a catalyst, and fatty acids and glycerol are mixed in a mass ratio of 1:(1~1.5) for esterification, followed by multiple water washing purification after the reaction. This method uses methyl sulfonate as a catalyst, which introduces genotoxic impurities, and the use of excess glycerol leads to a low content of medium-chain triglycerides and a high content of mono- and diesters.

[0005] Patent CN115448837A reports the direct esterification of medium-chain fatty acids with glycerol at high temperature to synthesize medium-chain triglycerides. After washing with alkaline solution and concentration, the refined medium-chain triglycerides are obtained. Although the process is simple to operate, the reaction temperature is high and the reaction time is long.

[0006] Patent CN104203896A uses oxides or chlorides of tungsten, molybdenum, calcium, zinc, chelate, or magnesium as catalysts to prepare medium-chain triglycerides. The products prepared at high temperatures are dark in color, and most of the metal catalysts used are precious metals. The post-processing adopts three-stage molecular distillation, which significantly increases the production cost.

[0007] Therefore, there is still room for improvement in the medium-chain triglycerides produced by existing catalysts. Summary of the Invention

[0008] The purpose of this invention is to provide a catalyst preparation method and its application in medium-chain triglycerides, in order to solve the problems raised in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: The preparation of a catalyst includes the following steps: S1: Add γ-alumina and silica gel to an organic solvent, stir to disperse evenly, and heat under reflux to obtain the catalyst precursor; S2: Washing and filtration are used to remove organic solvents from the catalyst precursor to obtain catalyst filter cake; S3: The catalyst filter cake is heated and calcined to obtain the catalyst.

[0010] Further, in step S1, the mass ratio of γ-alumina to silica gel is 1:2 to 1:5; the organic solvent is one or a combination of methanol, ethanol, and isopropanol; the liquid-solid ratio of the organic solvent to γ-alumina silica gel is 3 to 5 mL / g; the heating reflux temperature is 80 to 90°C, and the heating reflux time is 1 to 8 h.

[0011] Furthermore, the mass ratio of γ-alumina to silica gel is 1:3; the organic solvent is isopropanol; the liquid-to-solid ratio of the organic solvent to γ-alumina silica gel is 4 mL / g; the heating reflux temperature is 80~90℃, and the heating reflux time is 3~5 h.

[0012] Furthermore, in step S3, the heating and calcination temperature is 100~200℃, and the time is 1~10h.

[0013] Furthermore, the heating and roasting temperature is 130~150℃, and the time is 3~5h.

[0014] Furthermore, the catalyst preparation process also includes the following steps: heating and calcining the catalyst filter cake, and then subjecting the heated and calcined catalyst filter cake to p-toluenesulfonic acid loading treatment to obtain the catalyst.

[0015] Furthermore, the p-toluenesulfonic acid loading treatment includes the following steps: adding the catalyst filter cake after calcination and p-toluenesulfonic acid to deionized water, heating and stirring to react, reacting until the deionized water in the system evaporates to dryness, and then vacuum drying at 120~130℃ to constant weight.

[0016] Furthermore, the mass ratio of the catalyst filter cake after heating and calcination, p-toluenesulfonic acid, and deionized water is (10~15):(0.5~1.0):(30~40); the heating and stirring reaction temperature is 100~110℃.

[0017] Furthermore, the application process of the catalyst in the preparation of medium-chain triglycerides includes the following steps: mixing the catalyst with medium-chain fatty acids and glycerol uniformly, evacuating the system to below -0.1 MPa, heating and stirring the reaction, and after the reaction is completed, obtaining medium-chain triglycerides through post-treatment.

[0018] Furthermore, the medium-chain fatty acid is a mixture of octanoic acid and capric acid in a mass ratio of (3~5):2, and the molar ratio of medium-chain fatty acid to glycerol is (3.6~3.9):1; the catalyst accounts for 1%~5% of the total mass of medium-chain fatty acid and glycerol, the heating and stirring reaction temperature is 150~190℃, and the reaction time is 10~22h.

[0019] Furthermore, the heating and stirring reaction is a negative pressure staged reaction. The first stage reaction temperature is 150~160℃, the vacuum degree is -0.07~-0.09MPa, and the reaction time is 4~6h; the second stage reaction temperature is 160~190℃, the vacuum degree is -0.07~-0.09MPa, and the reaction time is 6~16h.

[0020] Furthermore, the post-processing steps are as follows: reduced pressure distillation to remove acid, filtration to remove catalyst, neutralization to remove acid, washing and purification, reduced pressure concentration and filtration.

[0021] Furthermore, the vacuum degree of vacuum distillation is ≤-0.01MPa, the vacuum distillation temperature is 150~160℃, and the vacuum distillation time is 3~4h.

[0022] Furthermore, neutralization and acid removal are performed using 400-500 mL of 0.5-1 mol / L sodium hydroxide solution at a temperature of 50-60℃ for 30-40 minutes.

[0023] Furthermore, the washing and purification process involves using 400-500 mL of purified water at a temperature of 50-60°C for 30-40 minutes.

[0024] Furthermore, the vacuum degree of vacuum concentration is ≤-0.09MPa, and the vacuum concentration temperature is 80~85℃.

[0025] Furthermore, the filtration uses a polyethersulfone organic membrane filter with a pore size of 0.2~0.5µm and a filtration temperature of ≤40℃.

[0026] Compared with the prior art, the beneficial effects of the present invention are: 1. The Lewis acid centers formed by numerous unsaturated coordinated Al³⁺ atoms on the surface of γ-alumina are the main source of its catalytic activity; the highly polar regions composed of abundant Si-OH atoms on the surface of silica gel can effectively adsorb and activate polar carboxylic acid and alcohol molecules; when silica gel is combined with γ-alumina, structural recombination occurs at the interface, forming a unique type of "pseudo-bridged silanol" active center. These sites can synergistically exert the catalytic effects of Lewis acids and Brønsted acids, while simultaneously activating alcohol and carboxylic acid molecules. By precisely coupling the strong adsorption capacity of silica gel with the strong acid activity of γ-alumina, a highly efficient catalytic system is constructed.

[0027] 2. This invention uses γ-alumina silica gel as a carrier to load trace amounts of p-toluenesulfonic acid. Under conditions of reduced reaction temperature and shortened reaction time, the conversion rate of medium-chain triglycerides is improved. The only reaction byproduct is water, which has no toxicity or contamination to the product. Furthermore, using γ-alumina silica gel as a carrier enables efficient removal of p-toluenesulfonic acid from the product, improving product purity. This method is simple to operate, and p-toluenesulfonic acid does not corrode equipment, making it suitable for industrial production. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0029] Example 1: Preparation of a catalyst: including the following steps: S1: 10g of γ-alumina and 30g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake was heated to 140℃ and calcined for 3 hours. 40g of the calcined catalyst filter cake and 2.0g of p-toluenesulfonic acid were added to 150mL of deionized water and heated to 105℃. The mixture was stirred continuously until the deionized water in the system evaporated to dryness. The mixture was then vacuum dried at 120℃ to constant weight to obtain the catalyst.

[0030] Application of the catalyst prepared in Example 1 in the preparation of medium-chain triglycerides: The process includes the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g catalyst to an esterification reactor, stir until homogeneous, evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, and keep the reactor connected to the storage tank. Heat to 150℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 4 hours. Heat to 160℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 6 hours. After the reaction, open the connection between the storage tank and the vacuum pump, evacuate under reduced pressure at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. Filter the system to remove the catalyst, add 400mL of 1.0mol / L sodium hydroxide solution to the filtrate, keep at 60℃ and stir for 30 minutes, allow to stand and separate, and discard the lower aqueous phase. The oil phase was washed twice with 400 mL of purified water, stirred at 60 °C for 30 min, and then separated. The oil layer was concentrated under reduced pressure at 80 °C to remove water, with a vacuum degree of -0.09 MPa. After concentration, the temperature was lowered to below 40 °C, and the mixture was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides.

[0031] Example 2: Preparation of a catalyst: including the following steps: S1: 10g of γ-alumina and 30g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 140℃ and calcined for 3 hours to obtain the catalyst.

[0032] Application of the catalyst prepared in Example 2 in the preparation of medium-chain triglycerides: The process includes the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g catalyst to an esterification reactor, stir until homogeneous, evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, and keep the reactor and storage tank connected. Heat to 155℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 5 hours. Heat to 185℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 14 hours. After the reaction, open the connection between the storage tank and the vacuum pump, evacuate under reduced pressure at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. Filter the system to remove the catalyst, add 400mL of 1.0mol / L sodium hydroxide solution to the filtrate, keep at 60℃ and stir for 30 minutes, allow to stand and separate, and discard the lower aqueous phase. The oil phase was washed twice with 400 mL of purified water, stirred at 60 °C for 30 min, and then separated. The oil layer was concentrated under reduced pressure at 80 °C to remove water, with a vacuum degree of -0.09 MPa. After concentration, the temperature was lowered to below 40 °C, and the mixture was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides.

[0033] Example 3: Preparation of a catalyst: including the following steps: S1: 30g of γ-alumina and 30g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 140℃ and calcined for 3 hours to obtain the catalyst.

[0034] Application of the catalyst prepared in Example 3 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0035] Example 4: Preparation of a catalyst: including the following steps: S1: 30g of γ-alumina and 10g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 140℃ and calcined for 3 hours to obtain the catalyst.

[0036] Application of the catalyst prepared in Example 4 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0037] Example 5: Preparation of a catalyst: including the following steps: S1: 30g of γ-alumina and 10g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 110℃ and calcined for 3 hours to obtain the catalyst.

[0038] Application of the catalyst prepared in Example 5 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0039] Example 6: Preparation of a catalyst: including the following steps: S1: 10g of γ-alumina and 30g of silica gel are added to 200mL of isopropanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of isopropanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 180℃ and calcined for 3 hours to obtain the catalyst.

[0040] Application of the catalyst prepared in Example 6 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0041] Example 7: Preparation of a catalyst: including the following steps: S1: 10g of γ-alumina and 30g of silica gel are added to 200mL of methanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of methanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 180℃ and calcined for 3 hours to obtain the catalyst.

[0042] Application of the catalyst prepared in Example 7 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0043] Example 8: Preparation of a catalyst: including the following steps: S1: 10g of γ-alumina and 30g of silica gel are added to 200mL of ethanol, stirred and dispersed evenly, heated to 85℃, and refluxed and stirred for 4h to obtain the catalyst precursor; S2: The system was cooled to room temperature and filtered. The filter cake was washed with 100 mL of ethanol to obtain the catalyst filter cake. S3: The catalyst filter cake is heated to 180℃ and calcined for 3 hours to obtain the catalyst.

[0044] Application of the catalyst prepared in Example 8 in the preparation of medium-chain triglycerides: The steps are the same as those in Example 2 for the preparation of medium-chain triglycerides, and medium-chain triglycerides are obtained.

[0045] Comparative Example 1: Preparation of a catalyst: The preparation process is the same as in the example.

[0046] Application of the catalyst in Comparative Example 1 in the preparation of medium-chain triglycerides: The process includes the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g γ-alumina to the esterification reactor. Evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, and keep the reactor connected to the storage tank. Heat to 155℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 5 hours. Heat to 185℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 14 hours. Open the connection between the storage tank and the vacuum pump, begin vacuum distillation at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. Filter the system to remove the solid γ-alumina. Add 400mL of 1.0mol / L sodium hydroxide solution to the filtrate, maintain the temperature at 60℃ with stirring for 30 minutes, allow to stand, separate the layers, and discard the lower aqueous phase. The oil phase was washed twice with 400 mL of purified water, stirred at 60 °C for 30 min, and then separated. The oil layer was concentrated under reduced pressure at 80 °C to remove water, with a vacuum degree of -0.09 MPa. After concentration, the temperature was lowered to below 40 °C, and the mixture was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides.

[0047] Comparative Example 2: Preparation of a catalyst: The preparation process is the same as in the example.

[0048] Application of the catalyst in Comparative Example 2 in the preparation of medium-chain triglycerides: The process includes the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g silica gel to an esterification reactor. Evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, but keep the reactor connected to the storage tank. Heat to 155℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 5 hours. Heat to 185℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 14 hours. Open the connection between the storage tank and the vacuum pump, begin vacuum distillation at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. Filter the system to remove the silica gel solids. Add 400mL of 1.0mol / L sodium hydroxide solution to the filtrate, maintain the temperature at 60℃ with stirring for 30 minutes, allow to stand, separate the layers, and discard the lower aqueous phase. The oil phase was washed twice with 400 mL of purified water, stirred at 60 °C for 30 min, and then separated. The oil layer was concentrated under reduced pressure at 80 °C to remove water, with a vacuum degree of -0.09 MPa. After concentration, the temperature was lowered to below 40 °C, and the mixture was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides.

[0049] Comparative Example 3: Application of Commercially Available Solid Acid Catalyst #1 in the Preparation of Medium-Chain Triglycerides: The process included the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g of commercially available solid acid catalyst #1 to the esterification reactor. Evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, and keep the reactor connected to the storage tank. Heat to 155℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 5 hours. Heat to 185℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 14 hours. Open the connection between the storage tank and the vacuum pump, begin vacuum distillation at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. The system was filtered to remove the commercially available solid acid catalyst #1. The filtrate was then added to 400 mL of a 1.0 mol / L sodium hydroxide solution, stirred at 60°C for 30 min, allowed to stand, and separated. The lower aqueous phase was discarded. The oil phase was washed twice with 400 mL of purified water, stirred at 60°C for 30 min, and separated. The oil layer was concentrated under reduced pressure at 80°C to remove water (vacuum degree -0.09 MPa). After concentration, the temperature was lowered to below 40°C, and the solution was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides. The commercially available solid catalyst #1 was N-ZSM-5, purchased from Hangzhou Carbonming Technology Co., Ltd.

[0050] Comparative Example 4: Application of Commercially Available Solid Acid Catalyst #2 in the Preparation of Medium-Chain Triglycerides: The process included the following steps: Add 585g octanoic acid, 315g decanoic acid, 150g glycerol, and 31.5g of commercially available solid acid catalyst #2 to the esterification reactor. Evacuate to below -0.1MPa, disconnect the connection between the storage tank and the vacuum pump, but keep the reactor connected to the storage tank. Heat to 155℃, adjust the vacuum to -0.085MPa with nitrogen, and maintain the temperature and pressure for 5 hours. Heat to 185℃, maintain the vacuum at -0.075MPa, and maintain the temperature and pressure for 14 hours. Open the connection between the storage tank and the vacuum pump, begin vacuum distillation at -0.01MPa, distill at 160℃ for 3 hours, cool to 60℃, and take a sample to measure the acid value. The system was filtered to remove the commercially available solid acid catalyst #2. 400 mL of a 1.0 mol / L sodium hydroxide solution was added to the filtrate, and the mixture was stirred at 60°C for 30 min. After standing, the liquid was separated, and the lower aqueous phase was discarded. The oil phase was washed twice with 400 mL of purified water, stirred at 60°C for 30 min, and then separated. The oil layer was concentrated under reduced pressure at 80°C to remove water (vacuum degree -0.09 MPa). After concentration, the temperature was lowered to below 40°C, and the mixture was filtered through a 0.22 µm polyethersulfone organic filter membrane to obtain medium-chain triglycerides. The commercially available solid acid catalyst #2 was HND-260, purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0051] 1. Catalyst p-toluenesulfonic acid loading = (mass after loading - mass before loading) / mass before loading × 100% 2. Determination of catalyst crystallinity: Place the sample on a glass slide and scan it with an X-ray diffractometer in the range of 5°~80°. Crystallinity = sum of the integral areas of all crystalline phase diffraction peaks / (integrated area of ​​amorphous phase scattering packet + sum of the integral areas of all crystalline phase diffraction peaks).

[0052] 3. Determination of total specific surface area / micropore specific surface area of ​​catalyst: 0.3~0.8g of uniform catalyst powder was selected and degassed under vacuum at 180℃ and <10Pa for 4h. After vacuum cooling to room temperature, it was weighed. Under the isothermal condition of liquid nitrogen at 77K, the total specific surface area of ​​the catalyst was obtained by testing with a multi-point BET model in the range of nitrogen relative partial pressure P / P0 of 0.05~0.35. At the same time, the micropore specific surface area of ​​the catalyst was obtained by testing with a t-plot model in the range of nitrogen relative partial pressure P / P0 of 0.001~0.05.

[0053] 4. Catalyst particle size distribution determination: The catalyst was dispersed in deionized water at a concentration of 100 µg / mL. After ultrasonic dispersion, the D90Vol.% value was immediately measured using a laser particle size analyzer.

[0054] 5. Determination of medium-chain triglyceride yield: Theoretically, 3 mol of fatty acid reacts with 1 mol of glycerol in an esterification reaction to produce medium-chain triglycerides. In the embodiments and comparative examples of this invention, an excess carboxylic acid scheme is used. Therefore, referring to the amount of glycerol used, the theoretical mass of medium-chain triglycerides = the amount of glycerol × the average molecular weight of the product. The average molecular weight of the product can be approximately calculated based on the proportion of fatty acids used. Medium-chain triglyceride yield = (actual mass of medium-chain triglycerides / theoretical mass of medium-chain triglycerides) × 100%.

[0055] 6. Determination of Hydroxyl Value of Medium-Chain Triglycerides: The hydroxyl value refers to the number of hydroxyl groups contained in 1g of test sample. It is determined using the method described in Section 0713 of the General Rules of the Chinese Pharmacopoeia (Part IV), concerning the determination of hydroxyl groups in fats and fatty oils. After acylation, the mass of potassium hydroxide used is expressed as mgKOH / g. The hydroxyl value indicates the amount of free hydroxyl groups in the product, reflecting the degree of reaction of the raw glycerol. The lower the hydroxyl value, the more complete the esterification reaction of the glycerol.

[0056] 7. Determination of acid value of medium-chain triglycerides: Acid value refers to the mass of potassium hydroxide required to neutralize all the acidic components in 1g of medium-chain triglycerides, expressed in mgKOH / g.

[0057] The measurement results are shown in Tables 1 and 2 below. Table 1. Test data on the catalyst in the preparation of medium-chain triglycerides.

[0058] Table 2 Catalyst Characteristic Test Data from Example 2

[0059] Conclusion: The optimal preparation process of the γ-alumina silica gel catalyst was verified by using the yield, hydroxyl value, and acid value of medium-chain triglycerides as standards. Furthermore, by using γ-alumina silica gel as a support and loading trace amounts of p-toluenesulfonic acid, the reaction temperature was lowered and the reaction time shortened, further improving the conversion rate of medium-chain triglycerides. Moreover, using γ-alumina silica gel as a support enables efficient removal of p-toluenesulfonic acid from the product, significantly reducing production costs. This catalyst is also simple to prepare and suitable for industrial production.

[0060] The optimal catalyst preparation method was optimized in Examples 2-7. In Example 2, the yield of chain triglyceride reached 85.2%, the reaction was relatively complete, and the hydroxyl value and acid value were low.

[0061] In Example 1, 1.96% p-toluenesulfonic acid was loaded onto the optimal γ-alumina silica support. Even with reduced reaction temperature and shortened reaction time, the yield of medium-chain triglycerides still reached 88.5%.

[0062] In Comparative Example 1, only single γ-alumina was used as a catalyst. Compared with Example 2, the yield was significantly reduced, the acid value of the post-treatment system was high, and there were more residual octanoic acid and decanoic acid raw materials.

[0063] In Comparative Example 2, only silica gel was used as a catalyst. Compared with Example 2, the yield was significantly reduced, the acid value of the post-treatment system was high, and there were more residual octanoic acid and decanoic acid raw materials.

[0064] Comparative Examples 3 and 4 used commercially available solid catalysts. The yields of medium-chain triglycerides prepared by these catalysts were significantly lower than those in Examples 1 and 2. The post-treatment systems had high acid values ​​and a large amount of residual octanoic acid and decanoic acid raw materials.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A catalyst preparation method, characterized in that: Includes the following steps: S1: Add γ-alumina and silica gel to an organic solvent, stir to disperse evenly, and heat under reflux to obtain the catalyst precursor; S2: Washing and filtration are used to remove organic solvents from the catalyst precursor to obtain catalyst filter cake; S3: The catalyst filter cake is heated and calcined to obtain the catalyst.

2. The preparation of a catalyst according to claim 1, characterized in that: In step S1, the mass ratio of γ-alumina to silica gel is 1:2 to 1:5; the organic solvent is one or a combination of methanol, ethanol, and isopropanol; the liquid-solid ratio of the organic solvent to γ-alumina silica gel is 3 to 5 mL / g; the heating reflux temperature is 80 to 90°C, and the heating reflux time is 1 to 8 h.

3. The preparation of a catalyst according to claim 1, characterized in that: In step S3, the heating and calcination temperature is 100~200℃, and the time is 1~10h.

4. The preparation of a catalyst according to claim 1, characterized in that: The catalyst preparation process further includes the following steps: heating and calcining the catalyst filter cake, and then subjecting the heated and calcined catalyst filter cake to p-toluenesulfonic acid loading treatment to obtain the catalyst.

5. The preparation of a catalyst according to claim 4, characterized in that: The p-toluenesulfonic acid loading treatment includes the following steps: The catalyst filter cake after calcination and p-toluenesulfonic acid were added to deionized water, heated and stirred to react. After the deionized water in the system was evaporated to dryness, the mixture was vacuum dried at 120~130℃ to constant weight.

6. The preparation of a catalyst according to claim 5, characterized in that: The mass ratio of the catalyst filter cake after calcination, p-toluenesulfonic acid, and deionized water is (10~15):(0.5~1.0):(30~40); the heating and stirring reaction temperature is 100~110℃.

7. The application of the catalyst prepared according to any one of claims 1 to 6 in the preparation of medium-chain triglycerides.

8. The application of the catalyst according to claim 7 in the preparation of medium-chain triglycerides, characterized in that: The application process The process includes the following steps: mixing the catalyst with medium-chain fatty acids and glycerol, evacuating the system to below -0.1 MPa, heating and stirring the reaction, and after the reaction is completed, post-processing is performed to obtain medium-chain triglycerides.

9. The application of the catalyst according to claim 8 in the preparation of medium-chain triglycerides, characterized in that: The medium-chain fatty acid is a mixture of octanoic acid and capric acid in a mass ratio of (3~5):

2. The molar ratio of the medium-chain fatty acid to glycerol is (3.6~3.9):

1. The catalyst accounts for 1%~5% of the total mass of the medium-chain fatty acid and glycerol. The heating and stirring reaction temperature is 150~190℃, and the reaction time is 10~22h.

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