A preparation method for extracting refined vegetable oil fatty acids

Abstract

The present invention relates to the technical field of oil processing, and specifically to a preparation method for extracting refined vegetable oil fatty acids. A preparation method for extracting refined vegetable oil fatty acids comprises the following steps: vegetable oil refining treatment and separation and extraction of refined vegetable oil fatty acids. In the process of vegetable oil refining treatment, modified rice husk-based porous carbon is used to deacidify and decolorize the degummed vegetable oil, which can efficiently adsorb the pigment, free fatty acid and heavy metal components in the vegetable oil, achieve the effect of simultaneous adsorption, deacidification and decolorization, effectively improve the efficiency of vegetable oil refining, and help improve the quality of vegetable oil refining, thereby improving the extraction effect of refined vegetable oil fatty acids; in the separation and extraction process of refined vegetable oil fatty acids, by adding a crystallization inclusion auxiliary agent, the contact between urea and saturated fatty acids in refined vegetable oil can be promoted, and stable inclusion composite crystals can be quickly formed, thereby improving the extraction purity of unsaturated fatty acids.

Description

Technical Field

[0001] The invention relates to the technical field of oil processing, and more specifically to a preparation method for extracting refined vegetable oil fatty acids. Background Art

[0002] The vegetable crude oil obtained by the existing process usually contains a lot of impurities, such as free fatty acids and heavy metals. The high content of free fatty acids will lead to too high acid value of vegetable oil, which will easily cause unnecessary chemical reactions in the process of fatty acid extraction, affecting the extraction effect of fatty acids. Heavy metal ions (such as arsenic, lead, copper, etc.) are oxidation catalysts that can accelerate the oxidation process of oils and fats, generate peroxides and other harmful byproducts, and then cause the structure and properties of fatty acids to change, affecting the extraction effect of fatty acids. Therefore, before the extraction of vegetable oil fatty acids, the vegetable crude oil is usually subjected to refining treatments such as degumming, deacidification, decolorization, and deodorization to remove impurities therein, thereby improving the extraction effect of vegetable oil fatty acids.

[0003] At present, the main methods for deacidification of vegetable oils include alkali refining, distillation, membrane, supercritical fluid extraction, adsorption, etc. Although the traditional alkali refining method is simple, it has the disadvantages of high oil loss, high nutrient loss, residual saponification, large water resource consumption and wastewater production; the distillation method is greatly affected by the phospholipid content and is prone to produce trans fatty acids; the membrane method and supercritical fluid extraction method have high costs, and the former membrane is easy to be contaminated, and it is difficult to be industrially applied in edible oils; the adsorption method is to use the adsorption of free fatty acids by adsorbents to achieve the effect of deacidification, which has the advantages of low cost, simple operation, and no wastewater discharge. However, the existing adsorbents such as activated white clay and attapulgite have limited adsorption effects. Although they can adsorb free fatty acids, they cannot achieve the purpose of decolorization and deacidification and adsorption of heavy metal ions at the same time. Therefore, decolorization or heavy metal ion removal can only be carried out after deacidification, which reduces the efficiency of vegetable oil refining, and it is easy to have more free fatty acids or heavy metal ions remaining in the refined vegetable oil, which affects the extraction effect of refined vegetable oil fatty acids.

[0004] Among the fatty acids in vegetable oils, although saturated fatty acids can provide energy for the human body and participate in the formation of human tissue cells, they have a high energy density and are prone to problems of difficulty in digestion or excess calories; unsaturated fatty acids have many benefits such as lowering cholesterol and triglycerides in the blood, regulating heart function, reducing blood viscosity, and improving blood microcirculation, and have been highly valued by the food, medicine, and cosmetics industries. The existing methods for extracting and separating unsaturated fatty acids mainly include low-temperature crystallization and urea inclusion method, in which urea inclusion method mainly separates based on the unsaturation of fatty acids. However, in the process of urea inclusion and adsorption of saturated fatty acids, there is a problem of inclusion of unsaturated fatty acids or incomplete dissociation of saturated fatty acids, which affects the extraction and separation rate and extraction purity of unsaturated fatty acids. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a preparation method for extracting refined vegetable oil fatty acids.

[0006] A preparation method for extracting refined vegetable oil fatty acids comprises the following steps:

[0007] S1: refining of vegetable oil, pressing raw materials to obtain crude vegetable oil, degumming the crude vegetable oil to obtain degummed vegetable oil, deacidifying and decolorizing the degummed vegetable oil using modified rice husk-based porous carbon to obtain deacidified and decolorized vegetable oil, and deodorizing the deacidified and decolorized vegetable oil to obtain refined vegetable oil;

[0008] S2: separation and extraction of refined vegetable oil fatty acids, the refined vegetable oil, sodium hydroxide and ethanol solution are heated and stirred to react, then cooled and allowed to stand, the upper liquid is separated and taken, the upper liquid is washed, dehydrated and dried, filtered and vacuum-evaporated to obtain preliminary extracted fatty acids, the preliminary extracted fatty acids are heated and stirred with urea, a crystallization inclusion aid and an ethanol solution, then cooled and stirred for a period of time, then allowed to stand and crystallize, filtered and taken the filtrate, extracted with n-hexane, washed, dehydrated and dried, filtered and vacuum-evaporated to obtain unsaturated fatty acids;

[0009] The modified rice husk-based porous carbon is obtained by activating rice husk and calcining it at high temperature to form rice husk-based porous carbon, and then modifying the rice husk-based porous carbon with amino cellulose diacetate.

[0010] Amination of cellulose diacetate is obtained by modifying cellulose diacetate with ethylenediamine.

[0011] Furthermore, the raw material is one of rice bran, rapeseed, soybean, peanut, sunflower seed or palm fruit.

[0012] Furthermore, step S1 of vegetable oil refining treatment specifically comprises the following steps:

[0013] S1.1: Pressing the raw material to obtain vegetable crude oil;

[0014] S1.2: adding a 75% by volume phosphoric acid solution to the vegetable crude oil at 80-85°C, wherein the amount of the 75% by volume phosphoric acid solution added is 3-5% of the volume of the vegetable crude oil, stirring and mixing, placing the mixture in a magnetic stirrer with variable speed stirring, and after the stirring is completed, centrifuging and filtering to obtain degummed vegetable oil;

[0015] S1.3: placing the degummed vegetable oil in a reactor, stirring the vegetable oil in the reactor at a speed of 180-200 rpm under the condition of 50-72°C, slowly adding the modified rice husk-based porous carbon into the reactor during the stirring process, and stopping adding the modified rice husk-based porous carbon when the amount of the modified rice husk-based porous carbon added is 4-6% of the mass of the degummed vegetable oil in the reactor, continuing stirring for 10-15 minutes, and then centrifuging and filtering to obtain the deacidified and decolorized vegetable oil;

[0016] S1.4: The deacidified and decolorized vegetable oil is vacuum-sucked into the deodorizer, and the temperature is raised to 100°C under a vacuum degree of >0.01Mpa. High-pressure and high-temperature steam is introduced, and the pressure is controlled at 0.02-0.04Mpa. The high-pressure and high-temperature steam is allowed to enter the deacidified and decolorized vegetable oil and circulate from the lower layer to the upper layer. The deodorization temperature is 200-230°C, and the deodorization time is 70-90min. Subsequently, refined vegetable oil is obtained after cooling and filtration.

[0017] Furthermore, in step S1.2, the specific operation of variable speed stirring is first stirring at 100-150 rpm for 1-3 min, and then stirring at 50-70 rpm for 60-90 min.

[0018] Furthermore, step S2 of separating and extracting refined vegetable oil fatty acids specifically comprises the following steps:

[0019] S2.1: Refined vegetable oil, sodium hydroxide and 95% ethanol solution are stirred and reacted at 70-80°C for 1-2h. After the reaction is completed, the temperature is lowered and allowed to stand for 20-60min, the lower layer liquid is separated and removed, and the upper layer liquid is taken. The upper layer liquid is washed with deionized water at 35-40°C until the pH value is neutral, and the washed upper layer liquid is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain the initially extracted fatty acids;

[0020] S2.2: Stir and mix the initially extracted fatty acids, urea, crystallization inclusion aid and 95% ethanol solution, heat and stir at 60-70°C for 10-30 minutes, cool to 34-40°C and stir for 6-15 minutes, then stand at 1-8°C for 2-4 hours, and filter to obtain the filtrate;

[0021] S2.3: The filtrate is extracted with n-hexane for 2 to 4 times, the organic solutions obtained after each extraction are combined, the organic solution is washed with deionized water at room temperature until the pH value is neutral, the washed organic solution is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain unsaturated fatty acids.

[0022] Furthermore, in step S2.1, the amount of sodium hydroxide added is 0.5% of the mass of the refined vegetable oil, and the volume fraction of 95% ethanol solution is 1 to 3 times the volume of the refined vegetable oil.

[0023] Furthermore, the mass ratio of the initially extracted fatty acid, urea, crystallization inclusion aid and 95% ethanol solution by volume is 1:1-2.5:0.02-0.04:4-9.

[0024] Furthermore, the crystallization inclusion aid is prepared by mixing gallic acid, chlorogenic acid and deionized water in a mass ratio of 0.1-2:8-14:80-120.

[0025] Furthermore, the preparation of modified rice husk-based porous carbon specifically includes the following steps:

[0026] The rice husk is washed, crushed and sieved to obtain rice husk powder, the rice husk powder is mixed with a 0.5% sulfuric acid solution at a solid-liquid mass ratio of 1:16-24, stirred and reacted at 100-120° C. for 0.5-1 h, and a filter residue A is filtered to obtain the filter residue A, and the filter residue A is washed to be neutral, and then placed in an oven at 50-65° C. to dry to obtain acidified rice husk;

[0027] The acidified rice husk and a 10% potassium hydroxide solution are mixed at a solid-liquid mass ratio of 1:20-25, stirred and reacted at room temperature for 0.5-1h, and the residue B is filtered and dried in an oven at 50-65°C to obtain activated rice husk. The activated rice husk is placed in a tubular furnace and kept at 500-600°C for 30-60min under a nitrogen atmosphere, and naturally cooled to room temperature to obtain rice husk-based porous carbon.

[0028] Add amino cellulose diacetate to acetone at a solid-liquid ratio of 0.1 g / mL, stir until the amino cellulose diacetate is dissolved, then add deionized water in an amount of 1 / 8 to 1 / 10 of the volume of acetone, stir evenly, and obtain an amino cellulose diacetate solution;

[0029] The rice husk-based porous carbon and the amino cellulose diacetate solution are stirred and mixed in a solid-liquid mass ratio of 1:0.5-2. After stirring evenly, a mixture is obtained. The mixture is spread on a tray container, left to stand at room temperature for 6-12 hours, and then dried in an oven at 58-65°C for 8-12 hours to obtain modified rice husk-based porous carbon.

[0030] Furthermore, the preparation of amino cellulose diacetate specifically comprises the following steps:

[0031] 15 to 21 parts by weight of ethylenediamine, 1 to 7 parts by weight of sodium carbonate and 60 to 100 parts by weight of deionized water are uniformly mixed to obtain a reaction solution, cellulose diacetate is added to the reaction solution, the solid-liquid mass ratio of cellulose diacetate to the reaction solution is 1:15 to 30, after uniform stirring, heating in a water bath at 60 to 90° C. for 2 to 4 hours, after the reaction is completed, filtering, washing and drying to obtain amino cellulose diacetate.

[0032] The present invention has the following advantages:

[0033] 1. In the present invention, cellulose diacetate is subjected to an amino modification treatment so that the hydroxyl groups on the surface of cellulose diacetate react with ethylenediamine having an amino group. During the reaction, the hydroxyl groups on the surface of cellulose diacetate undergo a dehydration reaction due to the nucleophilicity of the alcohol group, remove small molecule alcohols, and form amino active groups. The obtained amino cellulose diacetate can utilize the good mechanical strength and pore structure of cellulose diacetate to serve as an efficient filtering medium in the vegetable oil refining process. Moreover, under the action of the amino groups on the surface of the amino cellulose diacetate, it can not only undergo an acid-base neutralization reaction with the carboxyl groups in free fatty acids to form an amide bond or a salt structure, thereby efficiently adsorbing free fatty acids, but also can adsorb and fix heavy metal ions onto the amino cellulose diacetate by ion exchange and the formation of coordination bonds, thereby achieving the purpose of effectively adsorbing and removing free fatty acids and heavy metal ions.

[0034] 2. In the present invention, rice husk-based porous carbon is prepared by using rice husk as raw material. The large surface area and porous structure of the rice husk-based porous carbon can effectively adsorb pigments and free fatty acids in vegetable oils, thereby achieving good decolorization and deacidification purposes. Aminated cellulose diacetate is loaded in the rice husk-based porous carbon. The obtained modified rice husk-based porous carbon combines the adsorption characteristics of rice husk-based porous carbon and aminated cellulose diacetate. Under the synergistic effect of the rice husk-based porous carbon and the aminated cellulose diacetate, the pigments, free fatty acids and heavy metal components in the vegetable oils can be efficiently adsorbed, thereby effectively improving the efficiency of vegetable oil refining, improving the quality of vegetable oil refining, and thus improving the extraction effect of refined vegetable oil fatty acids;

[0035] 3. In the process of separation and extraction of refined vegetable oil fatty acids, the present invention can not only form inclusion composite crystals between urea and saturated fatty acids in the initially extracted fatty acids to separate saturated fatty acids from the initially extracted fatty acids, but also, through the addition of crystallization inclusion aids, can utilize the surface activity of gallic acid and chlorogenic acid to enhance the affinity between urea and fatty acids, reduce the interfacial tension between urea and fatty acids, promote the contact between urea and saturated fatty acids, make urea and saturated fatty acids more easily combine with each other, and then ensure the rapid and stable formation of inclusion composite crystals, thereby helping to remove saturated fatty acids and improve the extraction rate and extraction purity of unsaturated fatty acids. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Embodiment 1:

[0038] A preparation method for extracting refined vegetable oil fatty acids, specifically comprising the following steps:

[0039] S1: Vegetable oil refining,

[0040] S1.1: Using rapeseed as raw material, the rapeseed is squeezed to obtain rapeseed crude oil;

[0041] S1.2: adding a 75% by volume phosphoric acid solution to the rapeseed crude oil at 85°C, wherein the amount of the 75% by volume phosphoric acid solution added is 5% of the volume of the rapeseed crude oil, stirring and mixing, placing the mixture in a magnetic stirrer at 150 rpm for 2 min, and then stirring at 70 rpm for 60 min. After the stirring is completed, centrifuging and filtering are performed to obtain degummed rapeseed oil;

[0042] S1.3: placing the degummed rapeseed oil in a reactor, stirring the rapeseed oil in the reactor at a speed of 200 rpm under the condition of 65°C, slowly adding the modified rice husk-based porous carbon into the reactor during the stirring process, and stopping adding the modified rice husk-based porous carbon when the amount of the modified rice husk-based porous carbon added is 6% of the mass of the degummed rapeseed oil in the reactor, continuing stirring for 15 minutes, and then centrifuging and filtering to obtain the deacidified and decolorized rapeseed oil;

[0043] S1.4: Vacuum the deacidified and decolorized rapeseed oil into a deodorizer, raise the temperature to 100°C under a vacuum degree of 0.02Mpa, introduce high-pressure and high-temperature steam, control the pressure at 0.04Mpa, allow the high-pressure and high-temperature steam to enter the deacidified and decolorized vegetable oil, and circulate from the lower layer to the upper layer. The deodorization temperature is 210°C and the deodorization time is 90 minutes. Subsequently, after cooling and filtering, refined rapeseed oil is obtained;

[0044] S2: Separation and extraction of refined vegetable oil fatty acids,

[0045] S2.1: Refined rapeseed oil, sodium hydroxide and 95% ethanol solution by volume, wherein the amount of sodium hydroxide added is 0.5% of the mass of the refined rapeseed oil and the volume of 95% ethanol solution is 3 times the volume of the refined rapeseed oil, are stirred and reacted at 80°C for 1.5h. After the reaction is completed, the mixture is cooled and allowed to stand for 60min, the lower layer liquid is separated and removed, and the upper layer liquid is taken. The upper layer liquid is washed with deionized water at 40°C until the pH value is neutral, and the washed upper layer liquid is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain the initially extracted fatty acids;

[0046] S2.2: The initially extracted fatty acids, urea, crystallization inclusion aid and 95% ethanol solution were mixed in a mass ratio of 1:1.5:0.04:6, heated and stirred at 70°C for 15 min, then cooled to 34°C and stirred for 15 min, then allowed to stand at 3°C ​​for 4 h, and the filtrate was filtered;

[0047] The crystallization inclusion aid is prepared by mixing gallic acid, chlorogenic acid and deionized water in a mass ratio of 0.6:12:120;

[0048] S2.3: The filtrate is extracted with n-hexane for 4 times, the organic solutions obtained after each extraction are combined, the organic solution is washed with deionized water at room temperature until the pH value is neutral, the washed organic solution is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain unsaturated fatty acids.

[0049] The preparation of amino cellulose diacetate comprises the following steps:

[0050] 21 parts by weight of ethylenediamine, 7 parts by weight of sodium carbonate and 100 parts by weight of deionized water were mixed uniformly to obtain a reaction solution, cellulose diacetate was added to the reaction solution, the solid-liquid mass ratio of cellulose diacetate to the reaction solution was 1:30, and after stirring uniformly, the mixture was heated in a water bath at 90° C. for 3 hours. After the reaction was completed, the mixture was filtered, washed and dried to obtain amino cellulose diacetate.

[0051] The preparation and modification of rice husk-based porous carbon include the following steps:

[0052] The rice husk was washed, crushed and sieved to obtain rice husk powder, and the rice husk powder was mixed with a 0.5% sulfuric acid solution at a solid-liquid mass ratio of 1:24, and stirred for reaction at 110°C for 1h, and the filter residue A was filtered out, and the filter residue A was washed to neutrality, and then the filter residue A was placed in an oven at 65°C to dry to obtain acidified rice husk;

[0053] The acidified rice husk and 10% potassium hydroxide solution were mixed at a solid-liquid mass ratio of 1:25, stirred and reacted at room temperature for 1 hour, and the residue B was filtered out, and the residue B was placed in an oven at 65°C for drying to obtain activated rice husk;

[0054] The activated rice husk was placed in a tubular furnace and kept at 540°C for 60 min under a nitrogen atmosphere. After naturally cooling to room temperature, the rice husk-based porous carbon was obtained.

[0055] Add amino cellulose diacetate to acetone at a solid-liquid ratio of 0.1 g / mL, stir until the amino cellulose diacetate is dissolved, then add deionized water in an amount of 1 / 8 of the volume of acetone, stir evenly, and obtain an amino cellulose diacetate solution;

[0056] The rice husk-based porous carbon and the amino cellulose diacetate solution were stirred and mixed in a solid-liquid mass ratio of 1:1.5. After stirring evenly, a mixture was obtained. The mixture was spread on a tray container, allowed to stand at room temperature for 12 hours, and then dried in an oven at 60°C for 12 hours to obtain modified rice husk-based porous carbon.

[0057] Embodiment 2:

[0058] A preparation method for extracting refined vegetable oil fatty acids, specifically comprising the following steps:

[0059] S1: Vegetable oil refining,

[0060] S1.1: Using rapeseed as raw material, the rapeseed is squeezed to obtain rapeseed crude oil;

[0061] S1.2: adding a 75% by volume phosphoric acid solution to the rapeseed crude oil at 80°C, wherein the amount of the 75% by volume phosphoric acid solution added is 5% of the volume of the rapeseed crude oil, stirring and mixing, placing the mixture in a magnetic stirrer at 100 rpm for 2 min, and then stirring at 50 rpm for 90 min. After the stirring is completed, centrifuging and filtering are performed to obtain degummed rapeseed oil;

[0062] S1.3: placing the degummed rapeseed oil in a reactor, stirring the rapeseed oil in the reactor at a speed of 180 rpm under the condition of 70°C, slowly adding the modified rice husk-based porous carbon into the reactor during the stirring process, and stopping adding the modified rice husk-based porous carbon when the amount of the modified rice husk-based porous carbon added is 6% of the mass of the degummed rapeseed oil in the reactor, continuing stirring for 10 minutes, and then centrifuging and filtering to obtain the deacidified and decolorized rapeseed oil;

[0063] S1.4: Vacuum the deacidified and decolorized rapeseed oil into a deodorizer, raise the temperature to 100°C under a vacuum degree of 0.02Mpa, introduce high-pressure and high-temperature steam, control the pressure at 0.04Mpa, allow the high-pressure and high-temperature steam to enter the deacidified and decolorized vegetable oil, and circulate from the lower layer to the upper layer. The deodorization temperature is 230°C and the deodorization time is 70 minutes. Subsequently, after cooling and filtering, refined rapeseed oil is obtained;

[0064] S2: Separation and extraction of refined vegetable oil fatty acids,

[0065] S2.1: Refined rapeseed oil, sodium hydroxide and 95% ethanol solution by volume, wherein the amount of sodium hydroxide added is 0.5% of the mass of the refined rapeseed oil and the volume of 95% ethanol solution is 3 times the volume of the refined rapeseed oil, are stirred and reacted at 70°C for 2h. After the reaction is completed, the mixture is cooled and allowed to stand for 40min, the lower layer liquid is separated and removed, and the upper layer liquid is taken. The upper layer liquid is washed with deionized water at 35°C until the pH value is neutral, and the washed upper layer liquid is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain the initially extracted fatty acids;

[0066] S2.2: The initially extracted fatty acids, urea, crystallization inclusion aid and 95% ethanol solution were mixed in a mass ratio of 1:1.5:0.04:6, heated and stirred at 60°C for 30 minutes, then cooled to 40°C and stirred for 6 minutes, then allowed to stand at 1°C for 2 hours, and the filtrate was filtered;

[0067] The crystallization inclusion aid is prepared by mixing gallic acid, chlorogenic acid and deionized water in a mass ratio of 0.6:12:120;

[0068] S2.3: The filtrate is extracted with n-hexane for 4 times, the organic solutions obtained after each extraction are combined, the organic solution is washed with deionized water at room temperature until the pH value is neutral, the washed organic solution is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain unsaturated fatty acids.

[0069] The preparation of amino cellulose diacetate comprises the following steps:

[0070] 21 parts by weight of ethylenediamine, 7 parts by weight of sodium carbonate and 100 parts by weight of deionized water were mixed uniformly to obtain a reaction solution, cellulose diacetate was added to the reaction solution, the solid-liquid mass ratio of cellulose diacetate to the reaction solution was 1:30, and after stirring uniformly, heated in a water bath at 60° C. for 4 hours. After the reaction was completed, the amino cellulose diacetate was obtained by filtering, washing and drying.

[0071] The preparation and modification of rice husk-based porous carbon include the following steps:

[0072] The rice husk was washed, crushed and sieved to obtain rice husk powder, and the rice husk powder was mixed with a 0.5% sulfuric acid solution at a solid-liquid mass ratio of 1:24, and stirred at 100°C for 1 hour, and the filter residue A was filtered to obtain the filter residue A, and the filter residue A was washed to neutrality, and then placed in a 60°C oven to dry to obtain acidified rice husk;

[0073] The acidified rice husk and 10% potassium hydroxide solution were mixed at a solid-liquid mass ratio of 1:25, stirred and reacted at room temperature for 1 hour, and the residue B was filtered out, and the residue B was placed in an oven at 60°C for drying to obtain activated rice husk;

[0074] The activated rice husk was placed in a tubular furnace and kept at 600°C for 30 min under a nitrogen atmosphere. After naturally cooling to room temperature, the rice husk-based porous carbon was obtained.

[0075] Add amino cellulose diacetate to acetone at a solid-liquid ratio of 0.1 g / mL, stir until the amino cellulose diacetate is dissolved, then add deionized water in an amount of 1 / 8 of the volume of acetone, stir evenly, and obtain an amino cellulose diacetate solution;

[0076] The rice husk-based porous carbon and the amino cellulose diacetate solution were stirred and mixed at a solid-liquid mass ratio of 1:1.5. After stirring evenly, a mixture was obtained. The mixture was spread on a tray container, allowed to stand at room temperature for 12 hours, and then dried in an oven at 65°C for 8 hours to obtain modified rice husk-based porous carbon.

[0077] Embodiment 3:

[0078] A preparation method for extracting refined vegetable oil fatty acids, specifically comprising the following steps:

[0079] S1: Vegetable oil refining,

[0080] S1.1: Using rapeseed as raw material, the rapeseed is squeezed to obtain rapeseed crude oil;

[0081] S1.2: adding a 75% by volume phosphoric acid solution to the rapeseed crude oil at 85°C, wherein the amount of the 75% by volume phosphoric acid solution added is 3% of the volume of the rapeseed crude oil, stirring and mixing, placing the mixture in a magnetic stirrer at 150 rpm for 2 min, and then stirring at 70 rpm for 60 min. After the stirring is completed, centrifuging and filtering are performed to obtain degummed rapeseed oil;

[0082] S1.3: placing the degummed rapeseed oil in a reactor, stirring the rapeseed oil in the reactor at a speed of 200 rpm under the condition of 65°C, slowly adding the modified rice husk-based porous carbon into the reactor during the stirring process, and stopping adding the modified rice husk-based porous carbon when the amount of the modified rice husk-based porous carbon added is 4% of the mass of the degummed rapeseed oil in the reactor, continuing stirring for 15 minutes, and then centrifuging and filtering to obtain the deacidified and decolorized rapeseed oil;

[0083] S1.4: Vacuum the deacidified and decolorized rapeseed oil into a deodorizer, raise the temperature to 100°C under a vacuum degree of 0.02Mpa, introduce high-pressure and high-temperature steam, control the pressure at 0.04Mpa, allow the high-pressure and high-temperature steam to enter the deacidified and decolorized vegetable oil, and circulate from the lower layer to the upper layer. The deodorization temperature is 210°C and the deodorization time is 90 minutes. Subsequently, after cooling and filtering, refined rapeseed oil is obtained;

[0084] S2: Separation and extraction of refined vegetable oil fatty acids,

[0085] S2.1: Refined rapeseed oil, sodium hydroxide and 95% ethanol solution by volume, wherein the amount of sodium hydroxide added is 0.5% of the mass of the refined rapeseed oil and the amount of 95% ethanol solution by volume is 1 times the volume of the refined rapeseed oil, are stirred and reacted at 80°C for 1.5 hours. After the reaction is completed, the mixture is cooled and allowed to stand for 60 minutes, the lower layer liquid is separated and removed, and the upper layer liquid is taken. The upper layer liquid is washed with deionized water at 40°C until the pH value is neutral, and the washed upper layer liquid is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain the initially extracted fatty acids;

[0086] S2.2: The initially extracted fatty acids, urea, crystallization inclusion aid and 95% ethanol solution were mixed in a mass ratio of 1:2.5:0.04:9, heated and stirred at 70°C for 15 min, then cooled to 34°C and stirred for 15 min, then allowed to stand at 3°C ​​for 4 h, and the filtrate was filtered;

[0087] The crystallization inclusion aid is prepared by mixing gallic acid, chlorogenic acid and deionized water in a mass ratio of 2:8:120;

[0088] S2.3: The filtrate is extracted with n-hexane for 4 times, the organic solutions obtained after each extraction are combined, the organic solution is washed with deionized water at room temperature until the pH value is neutral, the washed organic solution is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain unsaturated fatty acids.

[0089] The preparation of amino cellulose diacetate comprises the following steps:

[0090] 15 parts by weight of ethylenediamine, 1 part by weight of sodium carbonate and 60 parts by weight of deionized water were mixed uniformly to obtain a reaction solution, cellulose diacetate was added to the reaction solution, the solid-liquid mass ratio of cellulose diacetate to the reaction solution was 1:20, and after stirring uniformly, the mixture was heated in a water bath at 90°C for 3 hours. After the reaction was completed, the mixture was filtered, washed and dried to obtain amino cellulose diacetate.

[0091] The preparation and modification of rice husk-based porous carbon include the following steps:

[0092] The rice husk is washed, crushed and sieved to obtain rice husk powder, the rice husk powder is mixed with a 0.5% sulfuric acid solution at a solid-liquid mass ratio of 1:20, stirred and reacted at 110°C for 1h, and a filter residue A is filtered to obtain the filter residue A, and the filter residue A is washed to neutrality, and then placed in an oven at 65°C to dry to obtain acidified rice husk;

[0093] The acidified rice husk and 10% potassium hydroxide solution were mixed at a solid-liquid mass ratio of 1:20, stirred and reacted at room temperature for 1 hour, and the residue B was filtered out, and the residue B was placed in an oven at 65°C for drying to obtain activated rice husk;

[0094] The activated rice husk was placed in a tubular furnace and kept at 540°C for 60 min under a nitrogen atmosphere. After naturally cooling to room temperature, the rice husk-based porous carbon was obtained.

[0095] Add amino cellulose diacetate to acetone at a solid-liquid ratio of 0.1 g / mL, stir until the amino cellulose diacetate is dissolved, then add deionized water in an amount of 1 / 10 of the volume of acetone, stir evenly, and obtain an amino cellulose diacetate solution;

[0096] The rice husk-based porous carbon and the amino cellulose diacetate solution were stirred and mixed in a solid-liquid mass ratio of 1:1. After stirring evenly, a mixture was obtained. The mixture was spread on a tray container, allowed to stand at room temperature for 12 hours, and then dried in an oven at 60°C for 12 hours to obtain modified rice husk-based porous carbon.

[0097] Comparative Example 1:

[0098] The same rapeseed crude oil as in Example 1 was used. Compared with Example 1, the difference of Comparative Example 1 was that the modified rice husk-based porous carbon in step S1.3 was replaced by rice husk-based porous carbon, and the other steps remained unchanged, which was recorded as Comparative Example 1.

[0099] Comparative Example 2:

[0100] The same rapeseed crude oil as in Example 1 was used. Compared with Example 1, the difference of Comparative Example 2 was that the modified rice husk-based porous carbon in step S1.3 was replaced by amino-cellulose diacetate, and the other steps remained unchanged, which was recorded as Comparative Example 2.

[0101] Comparative Example 3:

[0102] Using the same rapeseed crude oil as in Example 1, the difference of Comparative Example 3 compared with Example 1 is that, in the preparation process of modified rice husk-based porous carbon, the amino cellulose diacetate is replaced by cellulose diacetate, cellulose diacetate is mixed with acetone and deionized water to prepare a cellulose diacetate solution, and then the rice husk-based porous carbon and the cellulose diacetate solution are stirred and mixed to prepare rice husk-based porous carbon modified with cellulose diacetate, the modified rice husk-based porous carbon in step S1.3 is replaced by rice husk-based porous carbon modified with cellulose diacetate, and the other steps remain unchanged, which is recorded as Comparative Example 3.

[0103] Comparative Example 4:

[0104] The same rapeseed crude oil as in Example 1 was used. Compared with Example 1, the difference of Comparative Example 4 is that the crystallization inclusion aid in step S2.2 is removed. In S2.2, the initially extracted fatty acids, urea, and 95% by volume ethanol solution are stirred and mixed in a mass ratio of 1:1.5:6, and the remaining steps remain unchanged, which is recorded as Comparative Example 4.

[0105] Decolorization rate determination: 1 mL was taken from the degummed rapeseed oil of Examples 1-3 and Comparative Examples 1-3 as sample A, 4 mL of n-hexane was added to each group of sample A for dilution, and after oscillation, the absorbance was measured at 669 nm by a UV-visible spectrophotometer, and recorded as the absorbance value N0 of the rapeseed oil before decolorization and deacidification; subsequently, 1 mL was taken from the deacidified and decolorized rapeseed oil of Examples 1-3 and Comparative Examples 1-3 as sample B, 4 mL of n-hexane was added to each group of sample B for dilution, and after oscillation, the absorbance was measured at 669 nm by a UV-visible spectrophotometer, and recorded as the absorbance value N1 of the rapeseed oil after decolorization and deacidification, and the decolorization rate was calculated. The decolorization rate calculation formula is: M (%) = (N0-N1) / N0*100%, and the decolorization rate results are shown in Table 1.

[0106] Deacidification rate determination: According to the cold solvent indicator titration method in GB 5009.229-201, the acid values ​​of the degummed rapeseed oil of Examples 1-3 and Comparative Examples 1-3 and the deacidified and bleached rapeseed oil of Examples 1-3 and Comparative Examples 1-3 were respectively measured, and recorded as S0 and S1, respectively. The deacidification rate was calculated. The deacidification rate calculation formula is: T (%) = (S0-S1) / S0*100%. The deacidification rate results are shown in Table 1.

[0107] Heavy metal removal rate: According to GB 5009.11-2024, GB 5009.12-2023, GB 5009.13-2017 and GB5009.14-2017, the degummed rapeseed oil in Example 1-3 and Comparative Example 1-3, and the deacidified and decolorized rapeseed oil in Example 1-3 and Comparative Example 1-3 were respectively measured for the heavy metal contents of arsenic, lead, copper and zinc, and the results of the arsenic, lead, copper and zinc content measured for the degummed rapeseed oil and the deacidified and decolorized rapeseed oil in each group were summed up respectively to obtain the heavy metal content of the degummed rapeseed oil and the heavy metal content of the deacidified and decolorized rapeseed oil in each group, wherein the heavy metal content of the degummed rapeseed oil was recorded as Z0, and the heavy metal content of the deacidified and decolorized rapeseed oil was recorded as Z1, and the heavy metal removal rate was calculated, and the heavy metal removal rate calculation formula was: A (%) = (Z0-Z1) / Z0*100%, and the heavy metal removal rate results are shown in Table 1;

[0108]

[0109] As can be seen from the results in Table 1, the decolorization rate, deacidification rate and heavy metal removal rate measurement results of Examples 1-3 are better than the measurement results of Comparative Examples 1-3, indicating that the modified rice husk-based porous carbon is applied to the deacidification and decolorization process of rapeseed oil. The amino diacetate cellulose in the modified rice husk-based porous carbon and the rice husk-based porous carbon cooperate with each other to effectively improve the decolorization effect, deacidification effect and heavy metal removal effect of rapeseed oil, and effectively adsorb and remove free fatty acids, heavy metal components and pigments in rapeseed oil. Specifically, it can be seen from Examples 1-3 and Comparative Examples 1-2 that It can be seen that the rice husk-based porous carbon in the modified rice husk-based porous carbon mainly plays the role of pigment adsorption, and also has a certain adsorption effect on free fatty acids and heavy metal components. It can be seen from Examples 1-3 and Comparative Examples 2-3 that the amino-modified cellulose diacetate in the modified rice husk-based porous carbon has a significant adsorption and removal effect on free fatty acids and heavy metal components, indicating that the adsorption capacity of cellulose diacetate for free fatty acids and heavy metals in vegetable oils can be effectively improved by aminated modification of cellulose diacetate, thereby achieving the purpose of efficient adsorption and removal of free fatty acids and heavy metal ions.

[0110] Determination of unsaturated fatty acid extraction rate: According to the requirements of GB5009.168-2016 "Determination of fatty acids in food of national food safety standard", the unsaturated fatty acid content of the rapeseed crude oil used for extraction in Examples 1-3 and Comparative Examples 1-4 was determined, and the unsaturated fatty acid content in the rapeseed crude oil used for extraction was recorded as B0, and the unsaturated fatty acid content of each group of step S2.3 was determined, and the actual unsaturated fatty acid mass obtained by extraction was recorded as B1. The extraction rate and purity of the unsaturated fatty acids obtained in Examples 1-3 and Comparative Examples 1-4 were calculated respectively. The calculation formula for the unsaturated fatty acid extraction rate is: Q = B1 / B0*100%, and the calculation formula for the unsaturated fatty acid purity is: C (%) = B1 / the mass of unsaturated fatty acids obtained in step S2.3*100%. The results are shown in Table 2;

[0111]

[0112] It can be seen from Table 1-2 that in the rapeseed oil refining process, the deacidification rate, heavy metal removal rate and decolorization rate of Example 1-3 are higher than those of Comparative Examples 1-3, and the extraction rate of unsaturated fatty acids in the refined rapeseed oil is also relatively higher, and the extraction rate of unsaturated fatty acids reaches a level of more than 97%. However, the rapeseed oil in Comparative Examples 1-3 has relatively poor deacidification, decolorization and heavy metal component removal effects during the refining process, resulting in a high proportion of residual pigments, free fatty acids and heavy metal components in the refined rapeseed oil, thereby affecting the extraction rate of unsaturated fatty acids. This shows that the use of modified rice husk-based porous carbon to deacidify and decolorize rapeseed oil can not only effectively remove free fatty acids, heavy metal components and pigments, but also is beneficial to improve the extraction rate of unsaturated fatty acids in the separation and extraction process of refined vegetable oil fatty acids. In addition, it can be seen from Examples 1-3 and Comparative Example 4 that the extraction rate and purity of unsaturated fatty acids in Comparative Example 4 are relatively lower than those in Examples 1-3, indicating that in the separation and extraction process of refined vegetable oil fatty acids, the addition of a crystallization inclusion aid is beneficial to the effective separation of saturated fatty acids and unsaturated fatty acids, thereby avoiding the problem of inclusion of unsaturated fatty acids or incomplete dissociation of saturated fatty acids during the urea inclusion adsorption process of saturated fatty acids, thereby improving the extraction rate and purity of unsaturated fatty acids.

[0113] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention. Parts not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A preparation method for extracting refined vegetable oil fatty acids, characterized in that: The steps include: S1: refining of vegetable oil, pressing raw materials to obtain crude vegetable oil, degumming the crude vegetable oil to obtain degummed vegetable oil, deacidifying and decolorizing the degummed vegetable oil using modified rice husk-based porous carbon to obtain deacidified and decolorized vegetable oil, and deodorizing the deacidified and decolorized vegetable oil to obtain refined vegetable oil; S2: separation and extraction of refined vegetable oil fatty acids, the refined vegetable oil, sodium hydroxide and ethanol solution are heated and stirred to react, then cooled and allowed to stand, the upper liquid is separated and taken, the upper liquid is washed, dehydrated and dried, filtered and vacuum-evaporated to obtain preliminary extracted fatty acids, the preliminary extracted fatty acids are heated and stirred with urea, a crystallization inclusion aid and an ethanol solution, then cooled and stirred for a period of time, then allowed to stand and crystallize, filtered and taken the filtrate, extracted with n-hexane, washed, dehydrated and dried, filtered and vacuum-evaporated to obtain unsaturated fatty acids; The preparation of modified rice husk-based porous carbon specifically comprises the following steps: The rice husk is washed, crushed and sieved to obtain rice husk powder, the rice husk powder is mixed with a 0.5% sulfuric acid solution at a solid-liquid mass ratio of 1:16-24, stirred and reacted at 100-120° C. for 0.5-1 h, and a filter residue A is filtered to obtain the filter residue A, and the filter residue A is washed to be neutral, and then placed in an oven at 50-65° C. to dry to obtain acidified rice husk; The acidified rice husk and a 10% potassium hydroxide solution are mixed at a solid-liquid mass ratio of 1:20-25, stirred and reacted at room temperature for 0.5-1h, and the residue B is filtered and dried in an oven at 50-65°C to obtain activated rice husk. The activated rice husk is placed in a tubular furnace and kept at 500-600°C for 30-60min under a nitrogen atmosphere, and naturally cooled to room temperature to obtain rice husk-based porous carbon. Add amino cellulose diacetate to acetone at a solid-liquid ratio of 0.1 g / mL, stir until the amino cellulose diacetate is dissolved, then add deionized water in an amount of 1 / 8 to 1 / 10 of the volume of acetone, stir evenly, and obtain an amino cellulose diacetate solution; The rice husk-based porous carbon and the amino diacetate cellulose solution were stirred and mixed in a solid-liquid mass ratio of 1:0.5-2, and after being stirred evenly, a mixture was obtained, and the mixture was spread on a tray container, left to stand at room temperature for 6-12 hours, and then dried in an oven at 58-65°C for 8-12 hours to obtain a modified rice husk-based porous carbon; The preparation of amino cellulose diacetate specifically comprises the following steps: 15 to 21 parts by weight of ethylenediamine, 1 to 7 parts by weight of sodium carbonate and 60 to 100 parts by weight of deionized water are mixed uniformly to obtain a reaction solution, cellulose diacetate is added to the reaction solution, the solid-liquid mass ratio of cellulose diacetate to the reaction solution is 1:15 to 30, after stirring uniformly, heating in a water bath at 60 to 90° C. for 2 to 4 hours, after the reaction is completed, filtering, washing and drying to obtain amino cellulose diacetate; The crystallization inclusion aid is prepared by mixing gallic acid, chlorogenic acid and deionized water in a mass ratio of 0.1-2:8-14:80-120.

2. The method for extracting refined vegetable oil fatty acids according to claim 1, characterized in that: The raw material is one of rice bran, rapeseed, soybean, peanut, sunflower seed or palm fruit.

3. The method for extracting refined vegetable oil fatty acids according to claim 1, characterized in that: Step S1: vegetable oil refining treatment, specifically comprising the following steps: S1.1: Pressing the raw material to obtain vegetable crude oil; S1.2: adding a 75% by volume phosphoric acid solution to the vegetable crude oil at 80-85°C, wherein the amount of the 75% by volume phosphoric acid solution added is 3-5% of the volume of the vegetable crude oil, stirring and mixing, placing the mixture in a magnetic stirrer with variable speed stirring, and after the stirring is completed, centrifuging and filtering to obtain degummed vegetable oil; S1.3: placing the degummed vegetable oil in a reactor, stirring the vegetable oil in the reactor at a speed of 180-200 rpm under the condition of 50-72°C, slowly adding the modified rice husk-based porous carbon into the reactor during the stirring process, and stopping adding the modified rice husk-based porous carbon when the amount of the modified rice husk-based porous carbon added is 4-6% of the mass of the degummed vegetable oil in the reactor, continuing stirring for 10-15 minutes, and then centrifuging and filtering to obtain the deacidified and decolorized vegetable oil; S1.4: The deacidified and decolorized vegetable oil is vacuum-sucked into the deodorizer, and the temperature is raised to 100°C under a vacuum degree of >0.01Mpa. High-pressure and high-temperature steam is introduced, and the pressure is controlled at 0.02-0.04Mpa. The high-pressure and high-temperature steam is allowed to enter the deacidified and decolorized vegetable oil and circulate from the lower layer to the upper layer. The deodorization temperature is 200-230°C, and the deodorization time is 70-90min. Subsequently, refined vegetable oil is obtained after cooling and filtration.

4. The method for extracting refined vegetable oil fatty acids according to claim 3, characterized in that: In step S1.2, the specific operation of variable speed stirring is first stirring at 100-150 rpm for 1-3 min, and then stirring at 50-70 rpm for 60-90 min.

5. The method for extracting refined vegetable oil fatty acids according to claim 1, characterized in that: Step S2 is separation and extraction of refined vegetable oil fatty acids, specifically comprising the following steps: S2.1: Refined vegetable oil, sodium hydroxide and 95% ethanol solution are stirred and reacted at 70-80°C for 1-2h. After the reaction is completed, the temperature is lowered and allowed to stand for 20-60min, the lower layer liquid is separated and removed, and the upper layer liquid is taken. The upper layer liquid is washed with deionized water at 35-40°C until the pH value is neutral, and the washed upper layer liquid is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain the initially extracted fatty acids; S2.2: Stir and mix the initially extracted fatty acids, urea, crystallization inclusion aid and 95% ethanol solution, heat and stir at 60-70°C for 10-30 minutes, cool to 34-40°C and stir for 6-15 minutes, then stand at 1-8°C for 2-4 hours, and filter to obtain the filtrate; S2.3: The filtrate is extracted with n-hexane for 2 to 4 times, the organic solutions obtained after each extraction are combined, the organic solution is washed with deionized water at room temperature until the pH value is neutral, the washed organic solution is dehydrated and dried with anhydrous sodium sulfate, filtered and evaporated under reduced pressure to obtain unsaturated fatty acids.

6. The method for extracting refined vegetable oil fatty acids according to claim 5, characterized in that: In step S2.1, the amount of sodium hydroxide added is 0.5% of the mass of the refined vegetable oil, and the volume fraction of 95% ethanol solution is 1 to 3 times the volume of the refined vegetable oil.

7. The method for extracting refined vegetable oil fatty acids according to claim 6, characterized in that: The mass ratio of the initially extracted fatty acid, urea, crystallization inclusion aid and 95% ethanol solution is 1:1-2.5:0.02-0.04:4-9.

Images