A preparation method of monoglyceride of oleic acid and its product

Abstract

The present invention provides a preparation method of monoglyceride of oleic acid and its product, relating to the technical field of ester compound synthesis. The preparation method of the present invention comprises the following steps: (1) mixing glycerol, oleic acid and a solvent, adding a zeolite-p-toluenesulfonic acid catalyst to react, and obtaining an initial monoglyceride of oleic acid mixture; the molar ratio of glycerol to oleic acid is 1-2.5:1; the solvent is sulfolane and N,N-dimethylformamide in a mass ratio of 8:1-5; the ratio of the total mass of glycerol and oleic acid to the mass of the solvent is 4:1-3; (2) subjecting the initial monoglyceride of oleic acid mixture to a three-stage molecular distillation treatment: 100-200 Pa, 180-220°C, 50-80 Pa, 180-220°C, and 0-10 Pa, 180-230°C to obtain monoglyceride of oleic acid. The method of the present invention can improve the yield and purity of monoglyceride of oleic acid; mixing monoglyceride of oleic acid with a specific antioxidant can significantly improve the antioxidant properties of the product.

Description

Technical Field

[0001] The invention belongs to the technical field of ester compound synthesis, and particularly relates to a preparation method of oleic acid monoglyceride and a product thereof. Background Art

[0002] Fatty acid monoglycerides have emulsifying, lubricating, softening, and wetting properties and are widely used in food processing and cosmetics. For example, monoglyceride of lauric acid can be used as a food emulsifier, while monoglyceride of stearic acid can be used as a lubricant and antistatic agent in plastics.

[0003] The industrial production of fatty acid monoglycerides primarily involves chemical synthesis and enzymatic methods. The enzymatic method generally uses lipase as a catalyst to synthesize monoglycerides at relatively low temperatures. In his article, "Enzymatic Synthesis, Properties, and Application of Monoolein," Zeng Fankui used lipase to hydrolyze triglycerides and glycerol at a temperature of 50°C, yielding highly pure monoglyceride. However, the enzymatic method not only requires stringent reaction conditions and systems but also requires the use of bio-enzyme preparations, which are costly and unsuitable for large-scale production.

[0004] The chemical synthesis method utilizes glycerol and fatty acids to directly undergo an esterification reaction to produce fatty acid monoglycerides, as well as fatty acid diesters, fatty acid triglycerides and other components, resulting in a product mixture; the content of fatty acid monoglycerides in the mixture is generally only 40%-50%, and the yield and purity of fatty acid monoglycerides are low, which is not conducive to its further application.

[0005] Chinese invention patent CN113264831A discloses a method for preparing fatty acid monoglycerides, comprising the following steps: S1. Adding glycerol and fatty acids to a reactor, heating the reaction mixture to 140°C-180°C under the action of an alkaline catalyst, and reacting the mixture under vacuum at -0.096 MPa for 3-8 hours to obtain a crude fatty acid monoglyceride; S2. Removing crude fatty acids, glycerol, and other components from the fatty acid monoglyceride by molecular distillation at a temperature of 100°C-130°C, a pressure of 0-100 Pa, and a distillation time of 1-4 hours to obtain a distillate and a residue, the residue being the fatty acid monoglyceride. The product obtained by this method has a fatty acid monoglyceride content of 50%-55%, a fatty acid diester content of 35%-45%, a fatty acid triglyceride content of <5%, a glycerol content of <10%, and an acid value of <1 mgKOH / g. Although this method can increase the fatty acid monoglyceride content, the improvement is limited, and the fatty acid monoglyceride content in the product remains low, making it suitable only for industrial applications and not for the preparation of fine chemical products.

[0006] Chinese invention patent CN113698294A discloses a method for preparing olein by reactive azeotropic distillation. The method uses glycerol and oleic acid as the reaction raw materials, N-methylpyrrolidone as the reaction solvent, and toluene as the water-carrying agent, and is catalyzed by a solid acid to prepare olein. Toluene and water form an azeotropic system at a temperature of 95-110°C. The reaction temperature is 190-200°C, and the esterification reaction time is 6-8 hours. The molar ratio of alcohol to acid in the reaction raw materials is 1:4-5. The amount of the solid acid used is 2%-3% of the total mass of the reaction raw materials. The mass ratio of N-methylpyrrolidone to glycerol is 5:1, and the mass ratio of toluene to N-methylpyrrolidone is 1:1. Although this method can improve the conversion rate of the reaction process, the purity of the fatty acid monoglyceride still needs to be improved.

[0007] In view of this, further exploration and research on the preparation method of fatty acid monoglycerides is needed in order to obtain a higher fatty acid monoglyceride content; at the same time, further improvements should be made to the reaction process to solve the problem of insolubility and high viscosity of glycerol and fatty acids in the chemical synthesis method, which affects the purity and storage stability of the product. Summary of the Invention

[0008] The present invention addresses the problems existing in the prior art and provides a preparation method for oleic acid monoglyceride and a product thereof. Glycerol and oleic acid are used as reaction raw materials. In the presence of sulfolane and N,N-dimethylformamide, a zeolite-p-toluenesulfonic acid catalyst is added to carry out a reaction. The reaction product is subjected to a three-stage molecular distillation treatment to obtain high-purity oleic acid monoglyceride.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] First, the present invention provides a method for preparing monoglyceride of oleic acid, comprising the steps of:

[0011] (1) Glycerol, oleic acid and a solvent are mixed, and a zeolite-p-toluenesulfonic acid catalyst is added to react to obtain an initial oleic acid monoglyceride mixture; the molar ratio of the glycerol to the oleic acid is 1-2.5:1; the solvent is sulfolane and N,N-dimethylformamide in a mass ratio of 8:1-5; the mass ratio of the total mass of the glycerol and oleic acid to the mass of the solvent is 4:1-3;

[0012] (2) The initial monoglyceride oleate mixture obtained in step (1) is subjected to three-stage molecular distillation to obtain monoglyceride oleate; the conditions of the three-stage molecular distillation are: 100-200 Pa, 180-220° C. for the first stage molecular distillation treatment, 50-80 Pa, 180-220° C. for the second stage molecular distillation treatment, and 2-10 Pa, 180-230° C. for the third stage molecular distillation treatment.

[0013] Preferably, the preparation method is carried out in the presence of nitrogen or argon.

[0014] Preferably, in step (1), the mass ratio of sulfolane to N,N-dimethylformamide is 8:2-5.

[0015] Further preferably, in step (1), the mass ratio of sulfolane to N,N-dimethylformamide is 8:4.

[0016] Preferably, in step (1), the molar ratio of glycerol to oleic acid is 1.5-2:1.

[0017] Further preferably, in step (1), the molar ratio of glycerol to oleic acid is 1.8:1.

[0018] Preferably, in step (1), the ratio of the total mass of the glycerol and oleic acid to the mass of the solvent is 4:1-3.

[0019] Further preferably, in step (1), the ratio of the total mass of the glycerol and oleic acid to the mass of the solvent is 4:2.

[0020] Preferably, in step (1), the amount of the catalyst used is 1%-3% of the total mass of glycerol and oleic acid.

[0021] Further preferably, in step (1), the amount of the catalyst used is 2% of the total mass of glycerol and oleic acid.

[0022] In the present invention, the technical effects described in the present application can be achieved under the conditions of the dosage of the zeolite-p-toluenesulfonic acid catalyst; the dosage of the zeolite-p-toluenesulfonic acid catalyst is any endpoint value or intermediate value within the range, not limited to 1%-3%, 1%-2%, 2%-3%, 1%-2.5%, 1.5%-3%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3%.

[0023] Preferably, in step (1), the preparation method of the zeolite-p-toluenesulfonic acid catalyst is as follows: the zeolite is crushed through a 50-200 mesh sieve, activated at a temperature of 140-160°C for 1-3 hours, then immersed in a 40wt%-60wt% p-toluenesulfonic acid solution, pressurized at 5-10Pa for 4-6 hours, filtered, dried, and calcined at 120-140°C for 2-4 hours to obtain the zeolite-p-toluenesulfonic acid catalyst; the mass ratio of the zeolite to p-toluenesulfonic acid is 1:1-4.

[0024] Further preferably, in step (1), the preparation method of the zeolite-p-toluenesulfonic acid catalyst is as follows: the zeolite is crushed through a 100-mesh sieve, activated at 150°C for 2 hours, then immersed in a 50wt% p-toluenesulfonic acid solution, pressurized at 8-10Pa for 5 hours, filtered, dried, and calcined at 130°C for 3 hours to obtain the zeolite-p-toluenesulfonic acid catalyst.

[0025] More preferably, the mass ratio of the zeolite to p-toluenesulfonic acid is 1:3.

[0026] Preferably, in step (1), the reaction temperature is 130-150° C. and the reaction time is 3-6 h.

[0027] Further preferably, in step (1), the reaction temperature is 140° C. and the reaction time is 4 h.

[0028] Preferably, in step (1), after the reaction, the zeolite-p-toluenesulfonic acid catalyst is removed by filtration; and the excess solvents: sulfolane and N,N-dimethylformamide are removed by distillation under reduced pressure.

[0029] Preferably, in step (2), the conditions for the three-stage molecular distillation are: 100-200 Pa, 180-220 ° C, and a scraping speed of 500-700 rpm for the first stage molecular distillation treatment; 50-80 Pa, 180-220 ° C, and a scraping speed of 400-500 rpm for the second stage molecular distillation treatment; 2-10 Pa, 180-230 ° C, and a scraping speed of 400-500 rpm for the third stage molecular distillation treatment.

[0030] Further preferably, in step (2), the conditions for the three-stage molecular distillation are: 150Pa, 200°C, and a scraping speed of 600rpm for the first stage molecular distillation treatment; 60Pa, 200°C, and a scraping speed of 400rpm for the second stage molecular distillation treatment; 8Pa, 220°C, and a scraping speed of 400rpm for the third stage molecular distillation treatment.

[0031] Then, the present invention provides oleic acid monoglyceride prepared by the above preparation method; the purity of the oleic acid monoglyceride is 95%-99%.

[0032] Finally, the present invention provides a monoglyceride oleate product with high antioxidant properties, which is composed of the following components: the above-mentioned monoglyceride oleate and an antioxidant; the antioxidant is a mixture of Vc palmitate, BHT (2,6-di-tert-butyl-p-cresol) and vitamin E in a mass ratio of 2:2-5:1-3.

[0033] Preferably, the mass ratio of Vc palmitate, BHT and vitamin E is 2:4:2.

[0034] Preferably, in the monoglyceride oleate product, the mass ratio of monoglyceride oleate to antioxidant is 3000-6000:1.

[0035] Further preferably, in the monoglyceride oleate product, the mass ratio of monoglyceride oleate to antioxidant is 5000:1.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The preparation method of the present invention uses sulfolane and N,N-dimethylformamide as solvents, which is conducive to uniform mixing of glycerol and oleic acid. The reaction is promoted under the action of the composite catalyst zeolite-p-toluenesulfonic acid, thereby improving the yield and purity of oleic monoglyceride. Before molecular distillation, the oleic monoglyceride content in the initial oleic monoglyceride can reach 80%-87%. The method of the present invention can significantly improve the yield and purity of oleic monoglyceride.

[0038] 2. In the preparation method of the present invention, zeolite can also be used as a dehydrating agent to absorb water produced during the reaction, thereby promoting the reaction and improving the yield and purity of the product.

[0039] 3. In the preparation method of the present invention, oleic acid monoglyceride is purified by three-stage molecular distillation to improve the purity of the product.

[0040] 4. The monoglyceride of oleic acid prepared by the present invention, under the synergistic effect of Vc palmitate, BHT and vitamin E, can significantly improve the antioxidant property of the product, thereby improving storage stability and reducing the POV value. DETAILED DESCRIPTION

[0041] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. The following are merely illustrative of the scope of the present invention, and those skilled in the art may make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0042] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs.

[0043] The present invention is further described below by way of specific examples. Unless otherwise specified, the various chemical reagents used in the examples of the present invention were obtained through conventional commercial channels. The products of different manufacturers did not significantly affect the effects.

[0044] In the present invention, the purity (content, %) of monoglyceride of oleic acid = mass of monoglyceride of oleic acid / total mass of the product × 100%.

[0045] The total yield of monoglyceride of oleic acid (%) = actual mass of monoglyceride of oleic acid / theoretical mass of monoglyceride of oleic acid × 100%.

[0046] Example 1

[0047] A preparation method of monoglyceride of oleic acid is:

[0048] Step (1): 88.8 g of glycerol, 151.2 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial monoglyceride oleate mixture, wherein the content of monoglyceride oleate in the initial monoglyceride oleate mixture was 86.0%; the molar ratio of glycerol to oleic acid was 1.8:1;

[0049] The zeolite-p-toluenesulfonic acid catalyst was prepared by crushing the zeolite through a 100-mesh sieve, activating the zeolite at 150°C for 2 hours, immersing the zeolite in a 50 wt% p-toluenesulfonic acid solution, and pressurizing the solution at 9±1 Pa for 5 hours. The zeolite-p-toluenesulfonic acid catalyst was filtered, dried, and calcined at 130°C for 3 hours. The mass ratio of zeolite to p-toluenesulfonic acid was 1:3.

[0050] Step (2), the initial monoglyceride oleate mixture obtained in step (1) is subjected to three-stage molecular distillation: 150Pa, 200°C, and a scraping speed of 600rpm for the first stage molecular distillation treatment; 60Pa, 200°C, and a scraping speed of 400rpm for the second stage molecular distillation treatment; 8Pa, 220°C, and a scraping speed of 400rpm for the third stage molecular distillation treatment to obtain monoglyceride oleate, the yield of monoglyceride oleate is 79.3%, and the purity of monoglyceride oleate is 98.9%.

[0051] Example 2

[0052] Different from Example 1, in step (1), the mass ratio of the solvent sulfolane and N,N-dimethylformamide is different, and the mass ratio of the total mass of glycerol and oleic acid to the solvent is different.

[0053] Step (1): 88.8 g of glycerol, 151.2 g of oleic acid, 144 g of sulfolane, and 36 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial monoglyceride oleate mixture, wherein the content of monoglyceride oleate in the initial monoglyceride oleate mixture was 85.9%; the molar ratio of glycerol to oleic acid was 1.8:1;

[0054] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0055] Example 3

[0056] Different from Example 1, in step (1), the mass ratio of the solvent sulfolane and N,N-dimethylformamide is different, and the mass ratio of the total mass of glycerol and oleic acid to the solvent is different.

[0057] Step (1): 88.8 g of glycerol, 151.2 g of oleic acid, 36.9 g of sulfolane, and 23.1 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial oleic monoglyceride mixture, wherein the content of oleic monoglyceride in the initial oleic monoglyceride mixture was 85.1%; the molar ratio of glycerol to oleic acid was 1.8:1;

[0058] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0059] Example 4

[0060] The difference from Example 1 is that the molar ratio of glycerol to oleic acid in step (1) is different, and the amount of catalyst used and the composition ratio of the catalyst are different.

[0061] Step (1): 78.8 g of glycerol, 161.2 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 2.4 g of zeolite-p-toluenesulfonic acid catalyst (1% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial oleic monoglyceride mixture, wherein the content of oleic monoglyceride in the initial oleic monoglyceride mixture was 80.2%; the molar ratio of glycerol to oleic acid was 1.5:1;

[0062] The zeolite-p-toluenesulfonic acid catalyst was prepared by crushing the zeolite through a 100-mesh sieve, activating the zeolite at 150°C for 2 hours, immersing the zeolite in a 50 wt% p-toluenesulfonic acid solution, and pressurizing the solution at 9±1 Pa for 5 hours. The zeolite-p-toluenesulfonic acid catalyst was filtered, dried, and calcined at 130°C for 3 hours. The mass ratio of the zeolite to the p-toluenesulfonic acid was 1:1.

[0063] The three-stage molecular distillation in step (2) is the same as that in Example 1.

[0064] Example 5

[0065] The difference from Example 1 is that the molar ratio of glycerol to oleic acid in step (1) is different, and the amount of catalyst used and the ratio of catalyst components are different.

[0066] Step (1): 94.7 g of glycerol, 145.3 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 7.2 g of zeolite-p-toluenesulfonic acid catalyst (3% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial oleic monoglyceride mixture, wherein the content of oleic monoglyceride in the initial oleic monoglyceride mixture was 85.7%; the molar ratio of glycerol to oleic acid was 2:1;

[0067] The zeolite-p-toluenesulfonic acid catalyst was prepared by crushing the zeolite through a 100-mesh sieve, activating the zeolite at 150°C for 2 hours, immersing the zeolite in a 50 wt% p-toluenesulfonic acid solution, and pressurizing the solution at 9±1 Pa for 5 hours. The zeolite-p-toluenesulfonic acid catalyst was filtered, dried, and calcined at 130°C for 3 hours. The mass ratio of the zeolite to the p-toluenesulfonic acid was 1:4.

[0068] The three-stage molecular distillation in step (2) is the same as that in Example 1.

[0069] Example 6

[0070] The difference from Example 1 is that the molar ratio of glycerol to oleic acid in step (1) is different.

[0071] Step (1): 59 g of glycerol, 181 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial monoglyceride oleate mixture, wherein the content of monoglyceride oleate in the initial monoglyceride oleate mixture was 82.8%; the molar ratio of glycerol to oleic acid was 1:1;

[0072] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0073] Example 7

[0074] The difference from Example 1 is that the molar ratio of glycerol to oleic acid in step (1) is different.

[0075] Step (1): 107.8 g of glycerol, 132.2 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial monoglyceride oleate mixture, wherein the content of monoglyceride oleate in the initial monoglyceride oleate mixture was 86.3%; the molar ratio of glycerol to oleic acid was 2.5:1;

[0076] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0077] The specific reaction conditions of step (1) of Examples 1 to 7, the content of monoglyceride in the initial monoglyceride mixture obtained in step (1), and the total yield and purity of the final monoglyceride obtained after purification in step (2) are shown in Table 1.

[0078] Table 1

[0079]

[0080] Example 8

[0081] The difference from Example 1 is that the reaction conditions of step (1) are different: the reaction is carried out at 150° C. for 3 h to obtain an initial monoglyceride oleate mixture. The content of monoglyceride oleate in the initial monoglyceride oleate mixture obtained in step (1) is 84.6%.

[0082] Step (2) was the same as in Example 1, and the total yield of monoglyceride of oleic acid was 77.9% and the purity was 97.1%.

[0083] Example 9

[0084] The difference from Example 1 is that the reaction conditions of step (1) are different: the reaction is carried out at 130° C. for 6 h to obtain an initial oleic acid monoglyceride mixture. The initial oleic acid monoglyceride mixture obtained in step (1) has an oleic acid monoglyceride content of 84.8%.

[0085] Step (2) was the same as in Example 1, and the total yield of monoglyceride of oleic acid was 76.1% and the purity was 97.3%.

[0086] Example 10

[0087] The difference from Example 1 is that the conditions for the tertiary molecular distillation in step (2) are different.

[0088] Step (1) and the preparation method of zeolite-p-toluenesulfonic acid catalyst are the same as those in Example 1;

[0089] Step (2), the initial monoglyceride oleate mixture obtained in step (1) is subjected to three-stage molecular distillation: 100Pa, 220°C, and a scraping speed of 500rpm for the first stage molecular distillation treatment; 50Pa, 220°C, and a scraping speed of 500rpm for the second stage molecular distillation treatment; 10Pa, 180°C, and a scraping speed of 500rpm for the third stage molecular distillation treatment, to obtain a total yield of 76.6% and a purity of 96.8% of monoglyceride oleate.

[0090] Example 11

[0091] The difference from Example 1 is that the conditions for the tertiary molecular distillation in step (2) are different.

[0092] Step (1) and the preparation method of zeolite-p-toluenesulfonic acid catalyst are the same as those in Example 1;

[0093] Step (2), the initial monoglyceride oleate mixture obtained in step (1) is subjected to three-stage molecular distillation: 200Pa, 180°C, and a scraping speed of 700rpm for the first stage molecular distillation treatment; 80Pa, 180°C, and a scraping speed of 400rpm for the second stage molecular distillation treatment; 2Pa, 230°C, and a scraping speed of 400rpm for the third stage molecular distillation treatment, and the total yield of monoglyceride oleate is 76.0% and the purity is 96.1%.

[0094] Comparative Example 1

[0095] Glyceryl oleate was prepared according to the method described in Example 1 of Publication No. CN113698294A.

[0096] Solid acid catalyst SO4 2- The preparation method of / ZrO2-Al2O3 is as follows: zirconium oxychloride and aluminum nitrate in a molar ratio of 3:1 are dissolved in deionized water. After uniform dissolution, 28% NH3·H2O is added dropwise at room temperature with vigorous stirring to produce a white precipitate. After adjusting the pH of the system to 10, stirring is stopped and the precipitate is aged at room temperature for 24 hours. After aging, it is filtered and washed with deionized water until the filtrate is free of chloride ions. The filter cake is tested with silver nitrate and dried at 110°C for 24 hours. It is ground into powder, immersed in a 1 mol / L ammonium sulfate solution with stirring for 24 hours, and then filtered. After drying for 24 hours, it is calcined at 550°C for 6 hours to obtain the solid acid catalyst SO4 2- / ZrO2-Al2O3.

[0097] The raw materials 3.68g glycerol, 33.8g oleic acid, 18.41g solvent N-methylpyrrolidone and 20g water-carrying agent toluene were added into the reactor, and then 0.75g solid acid catalyst SO4 was weighed. 2- / ZrO2-Al2O3, the reaction temperature was controlled at 190°C, and the reaction was stirred and distilled for 6 hours. After the reaction, the product was filtered to separate the catalyst, and the solvent N-methylpyrrolidone was removed by washing with water. The water-carrying agent toluene was removed by vacuum rotary evaporation to obtain crude olein. The crude olein product had a 61.8% olein content and a total yield of 42.0%.

[0098] Comparative Example 2

[0099] The difference from Example 1 is that the sulfolane and N,N-dimethylformamide in step (1) are replaced entirely with N-methylpyrrolidone; that is, the solvent is 120 g of N-methylpyrrolidone. The rest is the same as Example 1.

[0100] Comparative Example 3

[0101] The difference from Example 1 is that the sulfolane in step (1) is replaced by N,N-dimethylformamide; that is, the solvent is 120 g of N,N-dimethylformamide. The rest is the same as Example 1.

[0102] Comparative Example 4

[0103] The difference from Example 1 is that N,N-dimethylformyl in step (1) is replaced by sulfolane; that is, the solvent is 120 g of sulfolane. The rest is the same as Example 1.

[0104] Comparative Example 5

[0105] Different from Example 1, in step (1), the mass ratio of the total mass of glycerol and oleic acid to the mass of the solvent is 1:4.

[0106] Step (1): 11.1 g of glycerol, 18.9 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 0.6 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial oleic monoglyceride mixture, wherein the content of oleic monoglyceride in the initial oleic monoglyceride mixture was 39.5%; the molar ratio of glycerol to oleic acid was 1.8:1;

[0107] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0108] Comparative Example 6

[0109] Different from Example 1, the molar ratio of glycerol to oleic acid is 1:2.

[0110] 33.6 g of glycerol, 206.4 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 4.8 g of zeolite-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140°C for 4 h to obtain an initial monooleylglycerol mixture having an oleylglycerol content of 28.1%. The molar ratio of glycerol to oleic acid was 1.8:1.

[0111] The preparation method of the zeolite-p-toluenesulfonic acid catalyst and the three-stage molecular distillation in step (2) are the same as those in Example 1.

[0112] Comparative Example 7

[0113] The difference from Example 1 is that the zeolite-p-toluenesulfonic acid catalyst in step (1) is replaced with zeolite (4.8 g) that has only passed through a 100-mesh sieve, and p-toluenesulfonic acid is not used. The rest is the same as Example 1.

[0114] Comparative Example 8

[0115] The difference from Example 1 is that the zeolite-p-toluenesulfonic acid catalyst in step (1) is replaced by an activated carbon-p-toluenesulfonic acid catalyst.

[0116] Step (1): 88.8 g of glycerol, 151.2 g of oleic acid, 80 g of sulfolane, and 40 g of N,N-dimethylformamide were mixed, 4.8 g of activated carbon-p-toluenesulfonic acid catalyst (2% of the total mass of glycerol and oleic acid) was added, and the mixture was reacted at 140° C. for 4 h to obtain an initial monoglyceride of oleate; the molar ratio of glycerol to oleic acid was 1.8:1;

[0117] The activated carbon-p-toluenesulfonic acid catalyst was prepared by grinding the activated carbon through a 100-mesh sieve, activating the activated carbon at 150°C for 2 hours, immersing the activated carbon in a 50 wt% p-toluenesulfonic acid solution, and pressurizing the solution at 9±1 Pa for 5 hours. The activated carbon-p-toluenesulfonic acid catalyst was filtered, dried, and calcined at 130°C for 3 hours. The mass ratio of the activated carbon to the p-toluenesulfonic acid was 1:3.

[0118] Step (2), subjecting the initial monoglyceride oleate mixture obtained in step (1) to three-stage molecular distillation: 150Pa, 200°C, and a scraping speed of 600rpm for the first stage molecular distillation treatment; 60Pa, 200°C, and a scraping speed of 400rpm for the second stage molecular distillation treatment; 8Pa, 220°C, and a scraping speed of 400rpm for the third stage molecular distillation treatment to obtain monoglyceride oleate.

[0119] Comparative Example 9

[0120] Unlike Example 1, the molecular distillation in step (2) is a single-stage molecular distillation: the initial monoglyceride oleate mixture obtained in step (1) is subjected to molecular distillation at 150 Pa, 200° C., and a scraping speed of 600 rpm to obtain monoglyceride oleate. Step (1) and the preparation method of the zeolite-p-toluenesulfonic acid catalyst are the same as those in Example 1.

[0121] Comparative Example 10

[0122] The difference from Example 1 is that the conditions of the three-stage molecular distillation in step (2) are different: the initial oleic acid monoglyceride mixture obtained in step (1) is subjected to a first-stage molecular distillation treatment at 80 Pa, 200° C., and a scraping speed of 600 rpm; a second-stage molecular distillation treatment is carried out at 40 Pa, 200° C., and a scraping speed of 400 rpm; and a third-stage molecular distillation treatment is carried out at 8 Pa, 220° C., and a scraping speed of 400 rpm.

[0123] Step (1) and the preparation method of the zeolite-p-toluenesulfonic acid catalyst are the same as those in Example 1.

[0124] In the technical solutions of Comparative Examples 2 to 10, the oleic acid monoglyceride content in the initial oleic acid monoglyceride mixture obtained in step (1), and the total yield and purity of the final oleic acid monoglyceride obtained after purification in step (2) are shown in Table 2.

[0125] Table 2

[0126]

[0127] Application Examples

[0128] Since monooleylglycerol is easily oxidized, antioxidants are usually added to improve its storage stability. This application example studies the stability of monooleylglycerol treated with different antioxidants, with the main indicator being the peroxide value (POV).

[0129] The monoglyceride obtained in Example 1 was mixed with various antioxidants to produce products containing monoglyceride. These products were stored under accelerated oxidation conditions at 63±1°C for 36 days. The POV values ​​(meq / kg) of the monoglyceride in each group of products are shown in Table 3.

[0130] Table 3

[0131]

[0132] The letters a, b, c, and d in Table 3 represent the results of significant differences: the same letters in different rows of the same column indicate no significant difference (P>0.05), and different letters indicate significant difference (P<0.05).

[0133] As can be seen from Table 3, when a specific ratio of Vc palmitate, BHT (2,6-di-tert-butyl-p-cresol) and vitamin E is used as an antioxidant to act on monoglyceride, compared with other antioxidant ingredients, the antioxidant properties of monoglyceride can be significantly improved. The POV values ​​of monoglyceride in groups 1-3 are small and the oxidation rate is slow; the POV values ​​of groups 1-3 are significantly lower than those in groups 4-7. The comparison results of groups 1-3 and 4-5 show that the Vc palmitate, BHT and vitamin E of the present invention as a whole can bring about a synergistic antioxidant effect, and the POV value is significantly reduced; the results of groups 1-3 and 6 show that not all antioxidants can achieve the technical effects of the present application. When Vc palmitate, BHA (butylated hydroxyanisole) and TBHQ (tert-butylhydroquinone) act on monoglyceride of oleic acid, the POV value is higher than that of groups 1-3, and the antioxidants of the present application as a whole have substantial characteristics; the results of groups 1-3 and 7 show that only the three antioxidants can bring about the effect of significantly reducing the POV value under a specific ratio.

[0134] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing monoglyceride of oleic acid, characterized in that: Including steps: (1) Glycerol, oleic acid and a solvent are mixed, and a zeolite-p-toluenesulfonic acid catalyst is added to react to obtain an initial oleic acid monoglyceride mixture; the molar ratio of the glycerol to the oleic acid is 1-2.5:1; the solvent is sulfolane and N,N-dimethylformamide in a mass ratio of 8:2-5; the mass ratio of the total mass of the glycerol and oleic acid to the mass of the solvent is 4:1-3; (2) The initial monoglyceride oleate mixture obtained in step (1) is subjected to three-stage molecular distillation to obtain monoglyceride oleate; the conditions of the three-stage molecular distillation are: 100-200 Pa, 180-220° C. for the first stage molecular distillation treatment, 50-80 Pa, 180-220° C. for the second stage molecular distillation treatment, and 2-10 Pa, 180-230° C. for the third stage molecular distillation treatment.

2. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of glycerol to oleic acid is 1.5-2:

1.

3. The preparation method according to claim 2, characterized in that In step (1), the molar ratio of glycerol to oleic acid is 1.8:1; the mass ratio of sulfolane to N,N-dimethylformamide is 8:

4.

4. The preparation method according to claim 1, characterized in that In step (1), the ratio of the total mass of the glycerol and oleic acid to the mass of the solvent is 4:

2.

5. The preparation method according to claim 1, characterized in that In step (1), the catalyst is used in an amount of 1%-3% of the total mass of glycerol and oleic acid.

6. The preparation method according to claim 1, characterized in that In step (1), the preparation method of the zeolite-p-toluenesulfonic acid catalyst is as follows: the zeolite is crushed through a 50-200 mesh sieve, activated at a temperature of 140-160°C for 1-3 hours, then immersed in a 40wt%-60wt% p-toluenesulfonic acid solution, pressurized at 5-10Pa for 4-6 hours, filtered, dried, and calcined at 120-140°C for 2-4 hours to obtain the zeolite-p-toluenesulfonic acid catalyst; the mass ratio of the zeolite to p-toluenesulfonic acid is 1:1-4.

7. The preparation method according to claim 1, characterized in that In step (1), the reaction temperature is 130-150°C and the reaction time is 3-6 hours.

8. The preparation method according to claim 1, characterized in that In step (2), the conditions for the three-stage molecular distillation are: 100-200 Pa, 180-220 ° C, and a scraping speed of 500-700 rpm for the first stage molecular distillation treatment; 50-80 Pa, 180-220 ° C, and a scraping speed of 400-500 rpm for the second stage molecular distillation treatment; 2-10 Pa, 180-230 ° C, and a scraping speed of 400-500 rpm for the third stage molecular distillation treatment.

9. A monoglyceride oleate product with high antioxidant properties, characterized in that: The invention is composed of the following components: oleic acid monoglyceride prepared by the preparation method according to any one of claims 1 to 8 and an antioxidant; the antioxidant is a mixture of Vc palmitate, BHT and vitamin E in a mass ratio of 2:2-5:1-3; The mass ratio of oleic acid monoglyceride to antioxidant is 3000-6000:1.

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