Production process of rapeseed oil

Abstract

The invention discloses a rapeseed oil production process, relates to the field of edible oil processing, and in particular relates to a rapeseed oil production process for extracting grease through a specific quaternary ammonium salt solvent. The cation of the solvent is a three-short-chain alkyl-one-long-chain alkyl quaternary ammonium cation, and the anion is one or more of saccharide, amino acid and organic acid anions. The process comprises the steps of pretreatment, squeezing, solvent leaching, separation, refining and solvent recovery. By controlling parameters of each step, such as mixing mass ratio, temperature, stirring speed and the like, efficient extraction and separation are realized. The quaternary ammonium salt solvent is low in toxicity, water-soluble and easy to separate, and the three anions have the advantages that the saccharide anions improve the grease compatibility, the amino acid anions promote grease release, the organic acid anions adjust the acid-base property, and the oil extraction rate and the separation effect are comprehensively improved. The solvent recovery step realizes cyclic utilization, the production cost and the environmental pollution risk are reduced, and finally the high-quality refined rapeseed oil is obtained.

Description

Technical Field

[0001] The present invention relates to the field of edible oil processing, and particularly to a production process of rapeseed oil. Background Art

[0002] In the production process of rapeseed oil, traditional processing techniques mainly use two methods, mechanical pressing and solvent extraction, to extract oil. Although mechanical pressing is simple to operate, there are problems such as low oil yield and the quality of the oil being easily affected by heat. Solvent extraction usually uses highly toxic organic solvents such as n-hexane. Although the extraction efficiency is high, there are large safety hazards, high environmental pollution risks, and the solvent residue may affect the quality of the oil. In addition, the existing solvent extraction process often requires complex equipment and cumbersome operations in the separation process of the solvent and the oil, with a high separation cost and it is difficult to achieve efficient recycling of the solvent.

[0003] Furthermore, the anions in the existing technology are relatively single, and the advantages of different anions cannot be fully utilized to comprehensively improve aspects such as oil yield and separation effect. Especially when facing the complex composition of rapeseeds, a single-anion solvent is difficult to adapt to the interaction characteristics of different components and oil, resulting in many limitations in the extraction and separation processes and it is difficult to meet the multiple requirements of modern rapeseed oil production for high efficiency, safety, environmental protection, and high quality. Summary of the Invention

[0004] Aiming at the above-mentioned disadvantages of the existing technology, the purpose of the present invention is to provide a production process of rapeseed oil to solve one or more problems in the existing technology.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A production process of rapeseed oil, comprising the following steps,

[0007] S1, Pretreatment: Mix 5% quaternary ammonium salt solvent with the washed rapeseeds according to a mass ratio of (3 - 3.5):1, stand still for 1 - 2 h under the condition of a temperature of 50 - 60°C, stir at a speed of 50 - 60 rpm, crush to a particle size of 0.5 - 0.8 mm, and perform hot air drying to reduce the water content of the rapeseeds to 8 - 10%. Obtain softened rapeseeds.

[0008] S2, Pressing: Extrude the softened rapeseeds at a temperature of 50 - 60°C and a pressure of 50 - 80 MPa to obtain cake residue. Let the extruded mixed liquid stand and separate layers to obtain crude oil.

[0009] S3, Solvent Leaching: Mix 15 - 20% quaternary ammonium salt solvent with cake meal at a mass ratio of (10 - 12):1, stir at a speed of 100 rpm for 2 - 3 h at 50 - 60 °C. Centrifuge and filter to obtain the leaching solution and defatted cake meal.

[0010] S4, Solvent Separation: Keep the crude oil at 60 - 70 °C for 2 - 3 h, and separate to obtain the oil phase and the solvent phase. Adjust the pH value of the leaching solution to 3.0, let it stand for 30 - 40 min, and centrifuge and purify at 2000 rpm for 10 min to obtain the oil phase and the solvent phase.

[0011] S5, Refining: Add citric acid and activated carbon to the oil phase, stir at 70 - 80 °C for 20 - 30 min, and filter to obtain refined rapeseed oil.

[0012] Among them, the cation in the quaternary ammonium salt solvent is a tri - short - chain - alkyl - one - long - chain - alkyl quaternary ammonium cation, and the structural general formula is [NR1R2R3R4] + , where R1, R2, and R3 are all independently selected C1 - C3 alkyl groups, and R4 is a C8 - C 18 linear or branched alkyl group.

[0013] Furthermore, the anion in the quaternary ammonium salt solvent is one or more of saccharide anions, amino acid anions, and organic acid anions.

[0014] Specifically, the saccharide anion is a carboxylate obtained by oxidizing monosaccharides or disaccharides. The amino acid anion is the carboxylate obtained by de - protonating natural amino acids. The organic acid anion is a C2 - C6 dibasic or tribasic carboxylate.

[0015] Furthermore, the production process also includes S6, Solvent Recovery: Adjust the pH value of the solvent phase to 7.0, and evaporate the water under vacuum to obtain a solid mixture.

[0016] Specifically, a weak base or an organic base is used to adjust the pH value in S6.

[0017] Furthermore, the solid mixture is recycled at least 5 times, and 5 - 10% of the quaternary ammonium salt solvent is supplemented each time during recycling.

[0018] Specifically, the evaporation conditions are a vacuum degree of - 0.08 to - 0.1 MPa, an evaporation temperature of 50 - 55 °C, and an evaporation time of 30 - 40 min.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] (1) The present invention adopts a combination of a specific quaternary ammonium salt solvent structure (the cation is a tri-short-chain alkyl-one long-chain alkyl quaternary ammonium cation, and the anion is one or more of a carbohydrate, an amino acid, and an organic acid anion) and a pretreatment step (specific mass ratio mixing, temperature, stirring speed, crushed particle size, drying moisture content, etc.), so that the pretreated rapeseed is fully contacted and mixed with the solvent in subsequent processing, and the oil release is easier, thereby improving the extraction efficiency and quality of the oil and allowing the solvent to better play its role.

[0021] (2) Quaternary ammonium salt solvents themselves have the characteristic of low toxicity. Different from the use of some highly toxic solvents in the existing technology, in the rapeseed oil processing process, they can not only protect the health of operators and reduce the safety hazards caused by solvent toxicity, but also make the final product rapeseed oil safer and more reliable, meeting people's high requirements for food quality and safety. At the same time, they are more environmentally friendly and reduce the risk of environmental pollution caused by highly toxic solvents.

[0022] (3) The quaternary ammonium salt solvent has the characteristics of being water-soluble and easy to separate, so that the solvent and oil can be better separated in each link of rapeseed oil processing. The insulation separation of crude oil and the centrifugal purification of the leaching solution after adjusting the pH value can both achieve efficient separation by virtue of the water solubility of the solvent. Compared with the solvents in the prior art that are difficult to separate or require complex equipment and tedious operations to separate, the present invention simplifies the separation process, reduces separation costs, improves production efficiency, and also helps to ensure the purity of rapeseed oil.

[0023] (4) The anions in the quaternary ammonium salt solvent are one or more of carbohydrate anions, amino acid anions, and organic acid anions. These three types of anions each have their own advantages and, together with the cationic component, have a positive impact on the rapeseed oil processing process. For example, carbohydrate anions help improve the compatibility between the solvent and the oil, enabling the solvent to better dissolve the oil, thereby increasing the oil yield; amino acid anions can interact with proteins and other components in the oil, facilitating the release of oil from the rapeseed, thereby increasing the oil yield; and organic acid anions can adjust the acidity and alkalinity of the solvent system, making the interaction between the solvent and the oil more suitable, further improving the oil extraction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic flow diagram of the production process of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and exemplary explanations. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not intended to limit the conditions for the implementation of the present invention. Therefore, they have no technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose of the present invention.

[0026] Example

[0027] The rapeseed oil production process of the present invention comprises the steps of pretreatment, pressing, solvent extraction, solvent separation, refining and solvent recovery, and oil is extracted by a specific quaternary ammonium salt solvent, thereby achieving efficient, safe, environmentally friendly and high-quality rapeseed oil production.

[0028] The following steps are involved:

[0029] Preprocessing steps:

[0030] The cleaned rapeseed is mixed with a 5% quaternary ammonium salt solvent at a mass ratio of (3-3.5):1, allowed to stand at 50-60°C for 1-2 hours, and stirred at 50-60 rpm to allow the rapeseed to fully absorb the solvent and soften. The mixture is then crushed to a particle size of 0.5-0.8 mm and then hot-air dried to reduce the rapeseed moisture content to 8-10%, yielding softened rapeseed. This step, by controlling the mixing ratio, temperature, stirring speed and time, as well as the crushed particle size and drying conditions, alters the internal structure of the rapeseed, facilitating subsequent oil extraction.

[0031] Pressing steps:

[0032] The pre-treated, softened rapeseed is extruded at a temperature of 50-60°C and a pressure of 50-80 MPa to produce a meal. During the extrusion process, a mixed liquid overflows and is allowed to separate into layers, with the upper layer representing the crude oil. This high-temperature, high-pressure extrusion process initially separates the oil from the rapeseed, preparing it for subsequent solvent extraction.

[0033] Solvent extraction steps:

[0034] 20% quaternary ammonium salt solvent is mixed with the cake in a mass ratio of (10-12):1 and stirred at 100 rpm at 50-60°C for 2-3 hours. After stirring, centrifuge and filter to obtain an extract and defatted cake. In this step, the quaternary ammonium salt solvent is fully utilized to further extract the residual oil in the cake.

[0035] Solvent separation steps:

[0036] The crude oil obtained by pressing is kept at 60-70°C for 2-3 hours to allow for natural stratification, resulting in the separation of the oil phase and the solvent phase. Simultaneously, the pH of the extract obtained by solvent extraction is adjusted to 3.0. After standing for 30-40 minutes, it is centrifuged at 2000 rpm for 10 minutes to similarly separate the oil phase and the solvent phase. Through temperature control and pH adjustment, the solvent and oil phases are effectively separated.

[0037] Refining steps:

[0038] An appropriate amount of citric acid and activated carbon is added to the separated oil phase and stirred at 70-80°C for 20-30 minutes to fully remove impurities, pigments, and odors. The oil is then filtered to obtain refined, high-quality rapeseed oil. This refining process effectively improves the quality and taste of the rapeseed oil.

[0039] Solvent recovery steps:

[0040] The pH value of the solvent phase after solvent separation is adjusted to 7.0, and water is removed from the solvent phase using vacuum evaporation conditions with a vacuum degree of -0.08 to -0.1 MPa, an evaporation temperature controlled at 50-55°C, and an evaporation time of 30-40 minutes to obtain a solid mixture. The solid mixture can be recycled at least five times, with 5-10% of the quaternary ammonium salt solvent added each time to achieve efficient solvent recovery and recycling.

[0041] Composition and function of quaternary ammonium salt solvent:

[0042] The quaternary ammonium salt solvent used in the present invention has a cation of a tri-short-chain alkyl-one-long-chain alkyl quaternary ammonium cation, and the general structural formula is [NR1R2R3R4] + , wherein R1, R2, and R3 are independently selected C1-C3 alkyl groups, and R4 is C8-C 18 Straight-chain or branched alkyl groups. The anion is one or more of a carbohydrate anion, an amino acid anion, or an organic acid anion. Carbohydrate anions are carboxylates derived from the oxidation of monosaccharides or disaccharides; amino acid anions are deprotonated carboxylates of natural amino acids; and organic acid anions are C2-C6 di- or tricarboxylates. Quaternary ammonium salt solvents with different anions play different roles in the rapeseed oil extraction process: carbohydrate anions improve the compatibility of the solvent with the oil, allowing the solvent to better dissolve the oil; amino acid anions interact with proteins and other components in the oil, facilitating its release from the rapeseed; and organic acid anions adjust the acidity and alkalinity of the solvent system, optimizing oil extraction. Quaternary ammonium salt solvents are low in toxicity, water-soluble, and easily separable, ensuring operator health and product quality while simplifying the separation process, reducing costs, and contributing to environmental protection.

[0043] To verify the feasibility and advantages of the process of the present invention, the following experiments were conducted to numerically detect parameters such as oil yield, acid value, peroxide value, color, and solvent residue of rapeseed oil produced using different production parameters. By introducing a simple weighted scoring mechanism, the quality of rapeseed oil in different experimental groups was intuitively and objectively evaluated.

[0044] The experiment content is as follows:

[0045] 1. Experimental Materials

[0046] Rapeseed: Select rapeseed with uniform maturity and no mold as raw material.

[0047] Quaternary ammonium salt compound: The cation is a tri-short chain alkyl-one long chain alkyl quaternary ammonium cation, with the general structural formula [NR1R2R3R4] + , wherein R1, R2, and R3 are all C2 alkyl groups, and R4 is C 13 Straight-chain or branched alkyl. Anions include carbohydrate anions (carboxylates obtained by oxidation of monosaccharides), amino acid anions (deprotonated carboxylates of natural amino acids), and organic acid anions (C4 dicarboxylates).

[0048] n-Hexane: used for control group experiments.

[0049] 2. Experimental Procedure

[0050] Pretreatment: Washed rapeseed is mixed with a 5% quaternary ammonium salt solvent or n-hexane at a mass ratio of 3:1. The mixture is allowed to stand at 50°C for 1 hour while stirring at 50 rpm to allow the rapeseed to fully absorb the solvent and soften. The mixture is then crushed to a particle size of 0.5 mm and dried with hot air to reduce the moisture content to 9%, resulting in softened rapeseed.

[0051] Pressing: The pre-treated softened rapeseed is squeezed at a temperature of 50°C and a pressure of 50 MPa to produce meal. During the squeezing process, the mixed liquid will overflow and then be allowed to stand and separate into layers. The upper layer is the crude oil.

[0052] Solvent extraction: Mix 15-20% quaternary ammonium salt solvent or n-hexane with the cake in a mass ratio of (10-12):1 and stir at 100 rpm for 2 hours at 55°C. After stirring, centrifuge and filter to obtain the leachate and defatted cake.

[0053] Solvent separation: The crude oil obtained by pressing was kept at 65°C for 2 hours to allow natural stratification, resulting in the separation of the oil phase and the solvent phase. Simultaneously, the extract obtained by solvent extraction was adjusted to a pH of 3.0, allowed to stand for 30 minutes, and then centrifuged at 2000 rpm for 10 minutes to similarly obtain the oil phase and the solvent phase.

[0054] Refining: Add an appropriate amount of citric acid and activated carbon to the separated oil phase and stir at 70°C for 20 minutes to fully remove impurities, pigments, and odors. Filter the oil to obtain refined high-quality rapeseed oil.

[0055] Solvent Recovery: The pH of the solvent phase after solvent separation is adjusted to 7.0. Water is removed from the solvent phase using vacuum evaporation conditions at -0.08 MPa, 50°C, and 30 minutes to obtain a solid mixture. This solid mixture can be recycled at least five times, with 5% of the quaternary ammonium salt solvent added each time.

[0056] 3. Determination method

[0057] (1) Acid value determination: According to the national standard method GB / T 5535-2017, weigh an appropriate amount of rapeseed oil sample, add a certain amount of neutral ethanol solution, then add phenolphthalein indicator, titrate with potassium hydroxide standard solution, record the volume of potassium hydroxide standard solution consumed, and calculate the acid value.

[0058] (2) Determination of peroxide value: According to GB / T 5538-2005, accurately weigh the rapeseed oil sample, add a mixture of potassium chloride solution and glacial acetic acid, and then titrate with sodium thiosulfate standard solution. Calculate the peroxide value based on the volume of sodium thiosulfate solution consumed.

[0059] (3) Color determination: According to GB / T 5536-2018, the rapeseed oil sample was compared with the standard colorimetric solution using a Lovibond colorimeter under the specified light source and conditions to determine its color.

[0060] (4) Determination of residual solvent: According to GB 5009.257-2016, the rapeseed oil sample was injected into the gas chromatograph, and the residual solvent was separated and detected under specific chromatographic conditions. The residual solvent was calculated based on the peak area.

[0061] 4. Weighted Scoring Mechanism

[0062] In order to comprehensively evaluate the quality of rapeseed oil, a weighted scoring mechanism is used to calculate the five indicators of oil yield, acid value, peroxide value, color and solvent residue, with weights of 0.3, 0.2, 0.2, 0.2 and 0.1 respectively. The calculation formula is as follows:

[0063] Quality score = oil yield score × 0.3 + acid value score × 0.2 + peroxide value score × 0.2 + color score × 0.2 + solvent residue score × 0.1

[0064] The score of each indicator is calculated as follows: the best value of the corresponding indicator in all experimental groups is 100 points, and the score of other experimental groups is (own value / best value) × 100.

[0065] 5. Experimental Results

[0066] (1) Comparative experimental data of the quaternary ammonium salt experimental group and the prior art experimental group (n-hexane solution)

[0067]

[0068] (2) Comparison of experimental data of three anionic quaternary ammonium salt solvents

[0069]

[0070] 6. Scoring results and data analysis

[0071] (1) Quality score of the comparative test of quaternary ammonium salt and n-hexane

[0072] The data in the table shows that the quaternary ammonium salt experimental group outperformed the n-hexane experimental group in all indicators. The quaternary ammonium salt experimental group had a significantly higher oil yield, better oil quality indicators such as acid value, peroxide value, and color, and significantly lower solvent residue. This demonstrates that quaternary ammonium salt solvents offer improved performance and lower safety risks in the rapeseed oil extraction process, resulting in the production of higher-quality rapeseed oil.

[0073] The reason why the score does not always change linearly with the variable: within a certain range, increasing the solvent concentration can increase the contact opportunity between the solvent and the oil, thereby increasing the oil yield. However, when the solvent concentration is too high, the competition effect between the solvent molecules may reduce the effective interaction between the solvent and the oil molecules, resulting in the oil yield no longer increasing significantly or even decreasing slightly. At the same time, too high a solvent concentration may dissolve more impurities, affecting the quality indicators of the oil. Increasing the mass ratio of solvent to material can provide more solvent molecules to dissolve the oil, thereby increasing the oil yield. However, when the mass ratio is too high, too much solvent may dilute the oil molecules, reduce the interaction efficiency between the solvent and the oil molecules, resulting in the oil yield no longer increasing significantly. In addition, too much solvent may increase the difficulty of the subsequent separation process, affecting the solvent recovery rate and the quality of the oil.

[0074] Principle Analysis: From a molecular perspective, quaternary ammonium salt cations carry a positive charge, which forms electrostatic interactions and hydrogen bonds with polar groups in oil molecules (such as the carboxyl groups of fatty acids). This interaction enables quaternary ammonium salt solvents to more effectively dissolve oil molecules, thereby increasing oil yield. Furthermore, the water solubility of quaternary ammonium salts makes it easier to separate from oils and fats during subsequent separation, simplifying the separation process and reducing the amount of residual solvent.

[0075] In contrast, n - hexane is a non - polar solvent that mainly interacts with oil molecules through van der Waals forces. This interaction is relatively weak, resulting in lower efficiency in extracting oil with n - hexane. Moreover, due to its non - polar nature, it is difficult to completely remove from the oil during the separation process, leading to a relatively high solvent residue.

[0076] (2) Quality fractions of the three anionic quaternary ammonium salt solvents compared with each other

[0077] From the data in the table, it can be seen that the three anionic quaternary ammonium salt solvents have their own advantages in different indicators:

[0078] Carbohydrate anions: They perform better in terms of oil yield, with a relatively high average oil yield. However, quality indicators such as acid value, peroxide value, and color are relatively slightly worse, and the solvent residue is also relatively high.

[0079] Amino acid anions: They have the lowest acid value, and the best peroxide value and color, indicating that they have significant advantages in improving the quality of oil. However, the oil yield is slightly lower than that of carbohydrate anions.

[0080] Organic acid anions: They have the lowest solvent residue, but their oil yield and oil quality indicators are between those of carbohydrate anions and amino acid anions.

[0081] In summary, the three anionic quaternary ammonium salt solvents have their own characteristics in the rapeseed oil extraction process. The appropriate anionic type can be selected according to the actual production requirements to achieve the best production effect and product quality.

[0082] Principle analysis: Carbohydrate anions: Carbohydrate anions usually have multiple hydroxyl and carboxyl groups. These groups can form hydrogen bonds and electrostatic interactions with the glycerol backbone and fatty acid chains in oil molecules. This multi - point interaction enhances the compatibility between the solvent and the oil, making the carbohydrate anionic quaternary ammonium salt perform well in terms of oil yield. However, too many hydroxyl and carboxyl groups may also cause the interaction between the solvent and the oil to be too strong, resulting in the dissolution of some impurities, thus affecting the quality indicators of the oil (such as acid value, peroxide value, and color).

[0083] Amino acid anions: Amino acid anions contain amino and carboxyl groups, which can form hydrogen bonds and electrostatic interactions with the glycerol backbone and fatty acid chains in oil molecules. In addition, amino acid anions can also interact with components such as proteins in rapeseed, helping to release more oil. This multi - faceted interaction makes amino acid anionic quaternary ammonium salts have significant advantages in improving the quality of oil, such as reducing acid value, peroxide value, and improving color. However, due to their interaction with components such as proteins, the oil yield may be slightly lower than that of carbohydrate anions.

[0084] Organic acid anions: Organic acid anions contain carboxyl groups, which can form electrostatic interactions with the glycerol backbone of oil molecules. Their acidic properties can also adjust the pH of the solvent system, facilitating the release of oil molecules from rapeseed. This adjustment helps reduce residual solvent levels, but may also affect oil yield and oil quality.

[0085] The various technical features described in the above exemplary embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above exemplary embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A production process of rapeseed oil, characterized in that: It includes the following steps. S1, Pretreatment: Mix 5% quaternary ammonium salt solvent with the cleaned rapeseeds according to a mass ratio of (3 - 3.5):1, let it stand for 1 - 2 h at a temperature of 50 - 60 °C; stir at a speed of 50 - 60 rpm; crush to a particle size of 0.5 - 0.8 mm, and hot air dry to reduce the water content of the rapeseeds to 8 - 10%; obtain softened rapeseeds. S2, Pressing: Extrude the softened rapeseeds at a temperature of 50 - 60 °C and a pressure of 50 - 80 MPa to obtain cake residue; let the extruded mixed liquid stand and separate into layers to obtain crude oil. S3, Solvent extraction: Mix 15 - 20% quaternary ammonium salt solvent with the cake residue according to a mass ratio of (10 - 12):1, stir at a speed of 100 rpm for 2 - 3 h at 50 - 60 °C; centrifuge and filter to obtain the leaching solution and defatted cake residue. S4, Solvent separation: Keep the crude oil at a temperature of 60 - 70 °C for 2 - 3 h, separate to obtain the oil phase and the solvent phase; adjust the pH value of the leaching solution to 3.0, let it stand for 30 - 40 min, and centrifuge and purify at 2000 rpm for 10 min to obtain the oil phase and the solvent phase. S5, Refining: Add citric acid and activated carbon to the oil phase, stir at a temperature of 70 - 80 °C for 20 - 30 min, and filter to obtain refined rapeseed oil. Among them, the cation in the quaternary ammonium salt solvent is a tri-short-chain alkyl-monol long-chain alkyl quaternary ammonium cation, and the structural general formula is [NR1R2R3R4] + , R1, R2, and R3 are all independently selected alkyl groups with 1 to 3 carbon atoms, and R4 is a C8-C 18 linear or branched alkyl group.

2. The production process of rapeseed oil according to claim 1, characterized in that: The anion in the quaternary ammonium salt solvent is one or more of sugar anions, amino acid anions, and organic acid anions.

3. The production process of rapeseed oil according to claim 2, characterized in that: The sugar anion is the carboxylate obtained by oxidizing monosaccharides or disaccharides. The amino acid anion is the carboxylate obtained by deprotonating natural amino acids. The organic acid anion is a C2 - C6 binary or ternary carboxylate.

4. The production process of rapeseed oil according to claim 1, characterized in that The production process further includes S6, Solvent recovery: Adjust the pH value of the solvent phase to 7.0, and vacuum evaporate the water to obtain a solid mixture.

5. The production process of rapeseed oil according to claim 4, characterized in that: In S6, a weak base or an organic base is used to adjust the pH value.

6. The production process of rapeseed oil according to claim 4, characterized in that: The solid mixture is recycled at least 5 times, and 5 - 10% of the quaternary ammonium salt solvent is supplemented each time during recycling.

7. The production process of rapeseed oil according to claim 4, characterized in that: The evaporation conditions are a vacuum degree of -0.08 to -0.1 MPa, an evaporation temperature of 50 - 55 °C, and an evaporation time of 30 - 40 min.

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