Edible waste grease recovery process

Abstract

The invention relates to the technical field of oil and fat refining, in particular to an edible waste oil and fat recovery process. Comprising the following steps: heating, centrifuging, dehydrating and deslagging the edible waste oil; preparing a magnetic phase transfer catalyst; the prepared amino acid ionic liquid is used as a green catalyst and is used for finely treating waste grease and recycling. The amino acid ionic liquid prepared by taking 1-butyl-3-methylimidazole hydroxide and alanine as raw materials can greatly promote two-phase interface mass transfer which is difficult to occur in a homogeneous reaction in a biodiesel transesterification reaction, so that the transesterification reaction is efficiently catalyzed to generate fatty acid methyl ester, namely biodiesel and glycerol; after the reaction is finished, the amino acid ionic liquid can be separated from a reaction system through standing layering or simple centrifugation by virtue of the characteristics of non-volatility and immiscibility with a product, so that the effects of increasing the content of an effective component, namely fatty acid methyl ester, in biodiesel and reducing impurities are achieved, and meanwhile, the amino acid ionic liquid is more environment-friendly compared with a traditional base catalyst; and the method has the characteristic of environmental friendliness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil refining, in particular to a kind of edible waste oil recovery process. BACKGROUND

[0002] Edible waste oil is a kind of oil mainly derived from waste oil, oil feet and fried residues generated in catering industry, food processing enterprises and household kitchens, which will cause environmental problems such as water pollution, soil destruction and pipe network blockage if not properly treated and directly discharged; If illegally recycled for feed or food production, it will seriously threaten food safety and public health. Therefore, standardizing the recycling and resource utilization of edible waste oil not only helps to reduce environmental load, but also is an important way to realize circular economy and produce renewable energy such as biodiesel.

[0003] At present, the recycling and reuse of edible waste oil is usually through ester exchange reaction to prepare biodiesel, in which homogeneous base catalysis is the most widely used traditional process, which has the advantages of high reaction efficiency, mild conditions and low cost. However, its inherent defects are also very prominent: homogeneous catalyst is difficult to separate and recover from the reaction system, and must be removed by acid-base neutralization and a large amount of water washing, which not only has complicated process, high energy consumption, but also produces high-concentration organic wastewater containing salt and soap, causing secondary pollution and increasing subsequent treatment cost, in addition, strong alkaline conditions can easily lead to saponification of free fatty acids in raw materials, reducing the yield of biodiesel and aggravating the emulsification phenomenon, further increasing the difficulty of product separation and purification.

[0004] In order to overcome the above problems, heterogeneous catalytic process is widely studied, such as using solid base or immobilized enzyme catalyst, which can be separated by filtration or centrifugation, to a certain extent, reducing the generation of wastewater. However, non-homogeneous catalysts generally have low accessibility of active sites, large mass transfer resistance and lower catalytic efficiency than homogeneous systems, which limits their industrial application potential. And heterogeneous catalysts face the problems of poor cycle stability, complex preparation process and high cost, therefore, the present application provides a kind of edible waste oil recovery process, which has solved the problems existing in the prior art. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a kind of edible waste oil recovery process.

[0006] A kind of edible waste oil recovery process, comprising the following steps: S1: heating, centrifuging, dehydrating and deslagging of edible waste oil The edible waste oil is heated to 75-90℃, stirred at 20-40r / min for 30-40min, then centrifuged at 75-90℃ and 3000-3600r / min for 5-10min by a three-phase centrifuge, the crude treated oil is discharged from the light phase outlet, the waste water is discharged from the heavy phase outlet, and the solid residue is discharged from the solid phase outlet, the crude treated oil is collected, vacuum dehydrated at 100-120℃ and -0.08MPa for 1-2h, then de-residued by a filter to obtain the refined waste oil; S2: preparation of magnetic phase transfer catalyst The ferriferrous oxide is dispersed in an ethanol aqueous solution and heated and stirred, concentrated ammonia water is added, TEOS is added dropwise into the stirred reactants, after the completion of the dropwise addition of TEOS, the reaction is continued under vigorous stirring, the reaction bottle is taken out of the water bath and cooled to room temperature, the solid product is separated and the precipitate is washed with anhydrous ethanol and ultrapure water alternately for three times, after drying, the ferriferrous oxide coated silica is obtained, the ferriferrous oxide coated silica is dispersed in anhydrous toluene, silane coupling agent is added, after the reaction, washing is performed, anhydrous toluene is then added, followed by the addition of poly(N-isopropyl acrylamide) and trioctylamine, heating and reaction are performed, then the product is washed and dried, dispersed in acetonitrile, iodomethane is added, heating and reflux are performed, and washing and drying are performed to obtain the magnetic phase transfer catalyst; S3: preparation of amino acid ionic liquid as green catalyst The equimolar [Bmim][OH] aqueous solution and alanine solid are mixed and reacted under stirring, vacuum rotary evaporation is performed at 60-70℃, the system is concentrated to one fifth of the original volume, vacuum drying is performed at 70-80℃ for 24-25h to remove residual water to obtain the amino acid ionic liquid. S4: recovery treatment of refined waste oil The refined waste oil is preheated, then sodium methoxide is added, followed by the addition of amino acid ionic liquid and magnetic phase transfer catalyst, stirring is performed, then the temperature is increased and stirring is continued for 10-15min, the magnetic phase transfer catalyst in the system is attracted to the bottle wall by the external adsorption of a strong magnet to form a compact deposit, the upper layer of the reaction liquid is poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product, the upper and lower layers of the reaction liquid in the separatory funnel are separated after standing, the lower layer is removed, and the upper layer of the oil phase is distilled using a rotary evaporator to obtain biodiesel.

[0007] Further, the preparation of the amino acid ionic liquid as a green catalyst in S3 is specifically as follows: The equimolar [Bmim][OH] aqueous solution and alanine solid are mixed in an ice water bath at 0-2℃, the reaction is performed under magnetic stirring at 300-400r / min for 12-13h to obtain an ionic liquid aqueous solution, vacuum rotary evaporation is performed at 60-70℃ using a rotary evaporator, the system is concentrated to one fifth of the original volume, vacuum drying is performed at 70-80℃ for 24-25h to remove residual water to obtain the amino acid ionic liquid.

[0008] Further, the S2 preparation of the magnetic phase transfer catalyst is specifically: 1-3 parts by mass of ferroferric oxide is dispersed in 10-12 parts by mass of an ethanol aqueous solution, and heated to 40-45℃, and 2-2.5 parts by mass of concentrated ammonia water is added after stirring at 200-300 r / min for 5-10 min. 0.3-0.5 parts by mass of TEOS is added to the stirred reactants at a speed of 1 mL / s, and after the TEOS is completely added, the reaction is continued at 40-45℃ with vigorous stirring for 12-13 h, and a grayish-brown shell layer is formed on the surface of the ferroferric oxide. The reaction bottle is removed from the water bath and cooled to room temperature. The solid product is separated and the precipitate is washed three times with anhydrous ethanol and ultrapure water alternately, and after drying at 60-65℃, silica surface-coated ferroferric oxide is obtained. 3-5 parts by mass of silica surface-coated ferroferric oxide is dispersed in 20-25 parts by mass of anhydrous toluene, and a silane coupling agent is added, and the reaction is refluxed under an inert atmosphere for 3-4 h. It is washed thoroughly with toluene and ethanol, and then 20-25 parts by mass of anhydrous toluene is added, followed by the addition of 5-6 parts by mass of poly(N-isopropylacrylamide) and 7-9 parts by mass of trioctylamine. The reaction is heated to 60-65℃ for 5-6 h, and then the product is washed and dried, dispersed in 20-25 parts by mass of acetonitrile, and 8-10 parts by mass of iodomethane is added. The reaction is refluxed at 65-70℃ to completely convert the tertiary amine groups to quaternary ammonium salt groups. It is washed with ethanol and dried to obtain a magnetic phase transfer catalyst.

[0009] Further, the S4 refining of waste oil recovery treatment is specifically: 10-15 parts by mass of refined waste oil is preheated at 30-35℃, and then 6-8 parts by mass of sodium methoxide is added, followed by the addition of 1-2 parts by mass of amino acid ionic liquid and 0.2-0.3 parts by mass of magnetic phase transfer catalyst. Stirring at 600-700 r / min for 3-4 h, then the temperature is raised to 50-55℃, and stirring is continued for 10-15 min. Then the stirring is turned off, and the magnetic phase transfer catalyst in the system is attracted to the bottle wall by a strong magnet outside to form a tight deposit. The upper layer of the reaction liquid is poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product. The upper layer of the reaction liquid in the separatory funnel is allowed to stand for 4-5 h, and after the layers are separated, the upper and lower layers are separated, and the lower layer is removed. The upper layer of the oil phase is distilled under reduced pressure at 50-60℃ using a rotary evaporator to obtain biodiesel.

[0010] Further, the silane coupling agent is specifically 3-(glycidyloxypropyl)trimethoxysilane.

[0011] Further, the magnetic phase transfer catalyst adsorbed on the bottle wall is washed with methanol or acetone, and the adsorbed magnetic phase transfer catalyst is washed repeatedly for 5 times to remove residual organic matter, and is stored after vacuum drying, and can be directly used for the next reaction.

[0012] Further, the strong magnet is specifically a neodymium magnet.

[0013] The present application has the following advantages: 1. The amino acid ionic liquid prepared from 1-butyl-3-methylimidazolium hydroxide and alanine as raw materials in the biodiesel transesterification reaction, the anion of the ionic liquid as a Bronsted base can abstract the proton of methanol to generate active methoxy ions, and the cation of the ionic liquid as a phase transfer carrier carries the methoxy ions to the hydrophobic oil phase through electrostatic interaction, greatly promoting the mass transfer at the two-phase interface which is difficult to occur in the homogeneous reaction, thereby efficiently catalyzing the transesterification reaction to generate fatty acid methyl ester (biodiesel) and glycerol; after the reaction is completed, the amino acid ionic liquid can be separated from the reaction system by standing and layering or simple centrifugation due to its non-volatility and immiscibility with the product, thereby improving the content of the effective component (fatty acid methyl ester) in the biodiesel and reducing impurities; meanwhile, the amino acid ionic liquid is more environmentally friendly than traditional alkali catalysts and has the characteristics of being friendly to the environment.

[0014] 2. The magnetic temperature-controlled phase transfer catalyst is prepared by modifying poly (N-isopropyl acrylamide) and trioctylamine on the silica shell layer and converting the quaternary ammonium salt group through iodomethane; the silica shell layer not only stabilizes the magnetic core but also provides abundant surface hydroxyl groups for chemical grafting; poly (N-isopropyl acrylamide) is a temperature-sensitive polymer, and its chain segment makes its solubility have temperature responsiveness, so that intelligent phase behavior switching of low-temperature dispersion reaction and high-temperature aggregation separation can be realized; trioctylamine generates a structure containing a quaternary ammonium salt group after reaction with iodomethane, and the quaternary ammonium salt cation can act as the catalytic active center of the magnetic catalyst to catalyze the phase transfer of the aqueous phase and the organic phase in waste oil; at the same time, the poly (N-isopropyl acrylamide) is grafted on the same silica shell layer together with the trioctylamine, so as to integrate the catalytic function and the intelligent response function, solve the contradiction of low efficiency of heterogeneous catalysts from the source, and improve the efficiency of the phase transfer catalytic reaction.

[0015] 3、The magnetic temperature-controlled phase transfer catalyst prepared in the application in the biodiesel preparation process, the catalyst uses the quaternary ammonium salt group to transfer the methoxy ion in the methanol reactant to the oil and fat phase, and only needs to simply raise the system temperature to above the minimum critical solution temperature, so that the catalyst with the magnetic ferroferric oxide core can be precipitated from the reaction medium due to the dehydration and curling of the polymer chain, and the instantaneous and complete solid-liquid separation can be realized by the external magnet adsorption, so that the catalyst is recycled and used, and the direct benefit brought by this mechanism is that the traditional process is completely abandoned, the purification process is greatly simplified, and the post-treatment cost is reduced. Meanwhile, the heterogeneous catalytic characteristics of the catalyst avoid the pollution of the catalyst to the reaction product, ensure the high purity of the biodiesel product, and the recyclability of the catalyst significantly reduces the material consumption and operating cost of the production process, so that the whole waste oil recovery process chain reduces the energy consumption and economic investment. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The edible waste oil recovery process flowchart of the application. DETAILED DESCRIPTION

[0017] In order to make the person skilled in the art better understand the technical solutions in the application, the technical solutions in the embodiments of the application will be clearly and completely described below in combination with the drawings in the embodiments of the application.

[0018] Embodiment 1: An edible waste oil recovery process, as shown in Figure 1 , comprises the following steps: S1: heating, centrifuging, dehydrating and deslagging of edible waste oil The edible waste oil is heated to 75℃, stirred at 20r / min for 30min, and then centrifuged at 75℃ and 3000r / min for 5min through a three-phase centrifuge, the crude treated oil is discharged from the light phase outlet, the waste water is discharged from the heavy phase outlet, and the solid slag is discharged from the solid phase outlet, the crude treated oil is collected, dehydrated at 100℃ and -0.08MPa vacuum for 1h, and then deslagged through a filter to obtain the refined waste oil.

[0019] S2: preparation of a magnetic phase transfer catalyst 1g of ferroferric oxide is dispersed in 10g of an ethanol aqueous solution, heated to 40℃, and then 2g of concentrated ammonia water is added after stirring at 200r / min for 5min, 0.3g of TEOS is added to the stirred reactant at a speed of 1mL / s, after the TEOS is added dropwise, the reaction is continued at 40℃ for 12h, and a gray-brown shell layer is formed on the surface of the ferroferric oxide, the reaction bottle is taken out from the water bath, and cooled to room temperature; The solid product was separated and the precipitate was washed with anhydrous ethanol and ultrapure water alternately three times, and dried at 60°C to obtain silica surface coated with ferroferric oxide; 3g of silica surface coated with ferroferric oxide was dispersed in 20g of anhydrous toluene, silane coupling agent 3-(glycidyloxypropyl)trimethoxysilane was added, and refluxed under inert atmosphere for 3h, washed thoroughly with toluene and ethanol, then 20g of anhydrous toluene was added, followed by the addition of 5g of poly(N-isopropylacrylamide) and 7g of trioctylamine, heated to 60°C for 5h, then the product was washed and dried, dispersed in 20g of acetonitrile, 8g of iodomethane was added, heated to 65°C to reflux, so that the tertiary amine group was completely converted to quaternary ammonium salt group, washed with ethanol and dried to obtain a magnetic phase transfer catalyst.

[0020] S3: Preparation of amino acid ionic liquid as green catalyst Equal molar amounts of [Bmim][OH] aqueous solution and alanine solid were mixed in an ice water bath at 0°C, stirred at 300r / min under magnetic stirring for 12h, to obtain an ionic liquid aqueous solution, which was concentrated to one fifth of the original volume by rotary evaporation at 60°C under reduced pressure, and then vacuum dried at 70°C for 24h to remove residual water, to obtain an amino acid ionic liquid.

[0021] S4: Recovery treatment of refined waste oil 10g of refined waste oil was preheated at 30°C, then 6g of sodium methoxide was added, followed by the addition of 1g of amino acid ionic liquid and 0.2g of magnetic phase transfer catalyst, stirred at 600r / min for 3h, then the temperature was raised to 50°C and stirring was continued for 10min, then the stirring was stopped and the magnetic phase transfer catalyst in the system was attracted to the bottle wall by a neodymium magnet outside to form a compact deposit, the upper layer of the reaction liquid was poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product, and the upper layer of the reaction liquid in the separatory funnel was allowed to stand for 4h, then the upper and lower layers were separated after layering, the lower layer was removed, and the upper layer of the oil phase was distilled under reduced pressure at 50°C using a rotary evaporator to obtain biodiesel.

[0022] Furthermore, the magnetic phase transfer catalyst adsorbed on the bottle wall was washed with methanol or acetone, and the adsorbed magnetic phase transfer catalyst was washed repeatedly for 5 times to wash away the residual organic matter, and then vacuum dried and stored, which could be directly used for the next reaction.

[0023] Example 2: A process for recycling edible waste oil, as shown in Figure 1 includes the following steps: S1: Heating, centrifugation, dehydration and deslagging of edible waste oil The edible waste oil was heated to 85℃, stirred at 30r / min for 35min, then centrifuged at 85℃ and 3300r / min for 8min by a three-phase centrifuge, the crude treated oil was discharged from the light phase outlet, the waste water was discharged from the heavy phase outlet, and the solid residue was discharged from the solid phase outlet, the crude treated oil was collected, vacuum dehydrated at 110℃ and -0.08MPa for 1.5h, then de-residue by a filter to obtain the refined waste oil.

[0024] S2: Preparation of magnetic phase transfer catalyst 2g of Fe3O4 was dispersed in 11g of aqueous ethanol solution and heated to 42℃, 250r / min stirring for 8min, then 2.2g of concentrated ammonia was added, 0.4g of TEOS was added to the stirred reactants at a speed of 1mL / s, after the completion of TEOS dropwise addition, continue to stir vigorously at 42℃ for 12.5h, a gray-brown shell layer is formed on the surface of Fe3O4, the reaction bottle is taken out from the water bath and cooled to room temperature; The solid product was separated and the precipitate was washed with anhydrous ethanol and ultrapure water alternately for three times, and then dried at 62℃ to obtain Fe3O4-coated SiO2; 4g of Fe3O4-coated SiO2 was dispersed in 22g of anhydrous toluene, silane coupling agent 3-(glycidyloxypropyl)trimethoxysilane was added, and the reaction was carried out under reflux for 3.5h in an inert atmosphere, and then washed with toluene and ethanol, and then 22g of anhydrous toluene was added, followed by the addition of 5.5g of poly(N-isopropylacrylamide) and 8g of trioctylamine, and then heated to 62℃ for reaction for 5.5h, and then the product was washed and dried, dispersed in 22g of acetonitrile, and then 9g of iodomethane was added, and then heated to 67℃ for reflux to completely convert the tertiary amine groups into quaternary ammonium salt groups, and then washed with ethanol and dried to obtain the magnetic phase transfer catalyst.

[0025] S3: Preparation of amino acid ionic liquid as green catalyst Equal molar amounts of [Bmim][OH] aqueous solution and alanine solid were mixed in an ice water bath at 1℃, and the reaction was carried out under magnetic stirring at 350r / min for 12.5h to obtain an aqueous solution of ionic liquid, which was concentrated to one fifth of the original volume by rotary evaporation at 65℃ under reduced pressure, and then vacuum dried in a vacuum drying oven at 75℃ for 24.5h to remove residual water to obtain the amino acid ionic liquid.

[0026] S4: Recovery treatment of refined waste oil 12g refined waste oil was preheated at 32℃, then 7g sodium methoxide was added, followed by 1.5g amino acid ionic liquid and 0.25g magnetic phase transfer catalyst, stirred at 650r / min for 3.5h, then the temperature was raised to 52℃, and stirring was continued for 12min, then the stirring was turned off, the magnetic phase transfer catalyst in the system was attracted to the bottle wall by a neodymium magnet outside to form a tight deposit, the upper layer of the reaction liquid was poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product, the upper layer of the reaction liquid in the separatory funnel was allowed to stand for 4.5h, and after the layers were separated, the upper and lower layers were separated, and the lower layer was removed, the upper layer of the oil phase was distilled under reduced pressure at 55℃ using a rotary evaporator to obtain biodiesel.

[0027] And the magnetic phase transfer catalyst adsorbed on the bottle wall was washed with methanol or acetone, and the adsorbed magnetic phase transfer catalyst was washed repeatedly for 5 times to wash away the residual organic matter, and was stored after vacuum drying, which could be directly used for the next reaction.

[0028] Example 3: A kind of edible waste oil recovery process, as shown in Figure 1 , comprising the following steps: S1: edible waste oil heating, centrifugation, dehydration, deslagging The edible waste oil was heated to 90℃, stirred at 40r / min for 40min, then centrifuged at 90℃ and 3600r / min for 10min by a three-phase centrifuge, the crude treated oil was discharged from the light phase outlet, the waste water was discharged from the heavy phase outlet, and the solid residue was discharged from the solid phase outlet, the crude treated oil was collected, dehydrated at 120℃ and -0.08MPa vacuum for 2h, and then deslagged by a filter to obtain refined waste oil.

[0029] S2: preparation of magnetic phase transfer catalyst 3g Fe3O4 was dispersed in 12g aqueous ethanol solution and heated to 45℃, 300r / min stirring for 10min, then 2.5g concentrated ammonia was added, 0.5g TEOS was added to the stirred reaction at a rate of 1mL / s, after the completion of TEOS dropwise addition, the reaction was continued at 45℃ with vigorous stirring for 13h, a gray-brown shell layer was formed on the surface of Fe3O4, the reaction bottle was taken out of the water bath and cooled to room temperature; The solid product was separated and the precipitate was washed with anhydrous ethanol and ultrapure water alternately three times, and dried at 65℃ to obtain Fe3O4-coated SiO2; 5 g of the silica surface coated with ferroferric oxide was dispersed in 25 g of anhydrous toluene, 3-(glycidyloxypropyl)trimethoxysilane was added as a silane coupling agent, and the reaction was carried out under reflux for 4 h in an inert atmosphere. The product was washed with toluene and ethanol, 25 g of anhydrous toluene was added, followed by the addition of 6 g of poly(N-isopropylacrylamide) and 9 g of trioctylamine, and the reaction was carried out at 65 °C for 6 h. The product was then washed and dried, dispersed in 25 g of acetonitrile, 10 g of iodomethane was added, and the reaction was carried out under reflux at 70 °C to completely convert the tertiary amine groups into quaternary ammonium salt groups. The product was washed with ethanol and dried to obtain the magnetic phase transfer catalyst.

[0030] S3: Preparation of amino acid ionic liquid as green catalyst Equal molar amounts of [Bmim][OH] aqueous solution and alanine solid were mixed in an ice water bath at 2 °C, and the reaction was carried out under magnetic stirring at 400 r / min for 13 h to obtain an ionic liquid aqueous solution. The solution was concentrated to one-fifth of the original volume by rotary evaporation at 70 °C under reduced pressure, and then vacuum dried at 80 °C for 25 h to remove residual water to obtain the amino acid ionic liquid.

[0031] S4: Recovery treatment of refined waste oil 15 g of refined waste oil was preheated at 35 °C, followed by the addition of 8 g of sodium methoxide, 2 g of amino acid ionic liquid, and 0.3 g of magnetic phase transfer catalyst. The mixture was stirred at 700 r / min for 4 h, and then the temperature was increased to 55 °C and the stirring was continued for 15 min. The magnetic phase transfer catalyst in the system was then attracted to the bottle wall by a neodymium magnet to form a compact deposit. The upper layer of the reaction solution was poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product. The upper layer of the reaction solution in the separatory funnel was allowed to stand for 5 h, and then the upper and lower layers were separated. The lower layer was removed, and the upper layer of the oil phase was distilled under reduced pressure at 60 °C using a rotary evaporator to obtain biodiesel.

[0032] In addition, the magnetic phase transfer catalyst adsorbed on the bottle wall was washed with methanol or acetone, and the adsorbed magnetic phase transfer catalyst was washed repeatedly for 5 times to remove residual organic matter. After vacuum drying, the product was stored and could be directly used in the next reaction.

[0033] Comparative Example 1 Comparative Example 1 is different from Example 1 in that step S3 is not performed, and step S4 is performed using [Bmim][OH] aqueous solution instead of amino acid ionic liquid, and the remaining steps are unchanged, which is denoted as Comparative Example 1.

[0034] Comparative Example 2 Comparative Example 2 is different from Example 1 in that TEOS is not added in step S2, and the remaining steps are unchanged, which is denoted as Comparative Example 2.

[0035] Comparative Example 3: Comparative Example 3 is different from Example 1 in that no iodomethane is added in step S2, and the remaining steps are unchanged, denoted as Comparative Example 3.

[0036] Comparative Example 4: Comparative Example 4 is a commercially available phase transfer catalyst used to replace the magnetic phase transfer catalyst in step S4, denoted as Comparative Example 4.

[0037] The content of fatty acid methyl ester in the biodiesel of Examples 1-3 and Comparative Examples 1 and 4 was analyzed by gas chromatography (GC), and the content of fatty acid methyl ester in the biodiesel was calculated, and the results are shown in Table 1. The content of fatty acid methyl ester in the biodiesel of Examples 1-3 and Comparative Examples 2-4 was analyzed by gas chromatography (GC), and the mass of the biodiesel obtained in step S3 was weighed, and the yield of fatty acid methyl ester produced from waste edible oil was calculated, fatty acid methyl ester yield = (fatty acid methyl ester content * biodiesel mass) / edible waste oil mass, and the results are shown in Table 2. After the reaction was completed, the phase transfer catalyst was recovered for the next reaction, and the yield of fatty acid methyl ester when the phase transfer catalyst was first used and the yield of fatty acid methyl ester after being reused 5 times were recorded, and the change rate (percentage decrease) of the yield of fatty acid methyl ester was calculated, and the test objects were Examples 1-3 and Comparative Example 4, and the results are shown in Table 3.

[0038] Table 1

[0039] Table 2

[0040] Table 3

[0041] As can be seen from Table 1, the content of fatty acid methyl ester of Examples 1-3 is 97-98%; Comparative Example 1 only uses [Bmim][OH] to reduce to 84%; It is shown that the catalytic activity of the amino acid ionic liquid formed by attaching alanine to [Bmim][OH] is significantly higher than that of [Bmim][OH] alone, and the amino acid ionic liquid obtained by modification of alanine exhibits better catalytic performance.

[0042] As can be seen from Table 2, the yield of fatty acid methyl ester is 92-93% in Examples 1-3; the yield of fatty acid methyl ester is reduced to 76% in Comparative Example 3 without TEOS, without SiO2shell; the yield of fatty acid methyl ester is reduced to 62% in Comparative Example 4 without iodomethane, without quaternization of the tertiary amine of trioctylamine, which shows that the TEOS shell not only protects Fe3O4 but also provides graftable sites; and the quaternization of trioctylamine by iodomethane improves the phase transfer efficiency, and both are indispensable.

[0043] As can be seen from Table 3, the performance of the commercially available phase transfer catalyst is significantly lower than the system, the commercially available catalyst can only give 85% of the ester content and 79% of the fatty acid methyl ester yield in Table 1 and Table 2, and the fatty acid methyl ester yield is reduced by 12.86% after 5 cycles, while the system is reduced by only 5.3-5.5%, which shows that the magnetic phase transfer catalyst of the application not only has high activity but also has good stability.

[0044] It should be understood that those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the application. The parts not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A process for recovering edible waste oil, characterized by, Comprising the following steps: S1: edible waste oil heating, centrifugation, dehydration, deslagging The edible waste oil is heated to 75-90℃, stirred at 20-40r / min for 30-40min, then centrifuged at 75-90℃ by a three-phase centrifuge at 3000-3600r / min for 5-10min, the crude treated oil is discharged from the light phase outlet, waste water is discharged from the heavy phase outlet, and solid slag is discharged from the solid phase outlet, the crude treated oil is collected, vacuum dehydrated at 100-120℃ and-0.08MPa for 1-2h, then deslagged by a filter to obtain refined waste oil; S2: preparation of magnetic phase transfer catalyst Fe3O4 is dispersed in an ethanol aqueous solution and heated and stirred, concentrated ammonia is added, TEOS is added dropwise to the stirred reactants, after the addition of TEOS is completed, the reaction is continued under vigorous stirring, the reaction bottle is taken out of the water bath and cooled to room temperature, the solid product is separated and the precipitate is washed with anhydrous ethanol and ultrapure water three times alternately, dried, and then coated with Fe3O4 on the surface of SiO2, the Fe3O4-coated SiO2 is dispersed in anhydrous toluene, a silane coupling agent is added, washed after reaction, anhydrous toluene is added again, then poly(N-isopropyl acrylamide) and trioctylamine are added, heated and reacted, then the product is washed and dried, dispersed in acetonitrile, iodomethane is added, heated and refluxed, washed and dried to obtain a magnetic phase transfer catalyst; S3: preparation of amino acid ionic liquid as green catalyst Equal molar amounts of [Bmim][OH] aqueous solution and alanine solid are mixed and reacted under stirring, vacuum rotary evaporation is performed at 60-70℃, concentrated to one fifth of the original volume, then vacuum drying is performed at 70-80℃ for 24-25h to remove residual water to obtain an amino acid ionic liquid. S4: refined waste oil recovery treatment The refined waste oil is preheated, then sodium methoxide is added, followed by the addition of amino acid ionic liquid and magnetic phase transfer catalyst, stirring, then heating and continuing to stir for 10-15min, the magnetic phase transfer catalyst in the system is attracted to the bottle wall by a strong magnet to form a compact deposit, the upper layer of the reaction liquid is poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product, the upper and lower layers of the reaction liquid in the separatory funnel are separated after standing, the lower layer is removed, and the upper layer of the oil phase is distilled using a rotary evaporator to obtain biodiesel.

2. The process for recovering waste edible oil according to claim 1, characterized in that, S3: preparation of amino acid ionic liquid as green catalyst Equal molar amounts of [Bmim][OH] aqueous solution and alanine solid are mixed in an ice water bath at 0-2℃, stirred at 300-400r / min for 12-13h to obtain an ionic liquid aqueous solution, vacuum rotary evaporation is performed at 60-70℃, concentrated to one fifth of the original volume, then vacuum drying is performed at 70-80℃ for 24-25h to remove residual water to obtain an amino acid ionic liquid.

3. The process for recovering waste edible oil according to claim 2, characterized in that, S2: preparation of magnetic phase transfer catalyst 1-3 parts by mass of ferroferric oxide was dispersed in 10-12 parts by mass of an ethanol aqueous solution, heated to 40-45 DEG C, and stirred at 200-300 r / min for 5-10 min, then 2-2.5 parts by mass of concentrated ammonia water was added, 0.3-0.5 parts by mass of TEOS was added to the stirred reactants at a rate of 1 mL / s, after the addition of TEOS was completed, the reaction was continued at 40-45 DEG C with vigorous stirring for 12-13 h, a grayish-brown shell layer was formed on the surface of the ferroferric oxide, the reaction bottle was removed from the water bath, and cooled to room temperature; The solid product was separated and the precipitate was washed with anhydrous ethanol and ultrapure water three times, and then dried at 60-65 DEG C to obtain silica surface coated ferroferric oxide; 3-5 parts by mass of silica surface coated ferroferric oxide was dispersed in 20-25 parts by mass of anhydrous toluene, a silane coupling agent was added, and the reaction was refluxed under an inert atmosphere for 3-4 h, then washed with toluene and ethanol, then 20-25 parts by mass of anhydrous toluene was added, followed by the addition of 5-6 parts by mass of poly(N-isopropyl acrylamide) and 7-9 parts by mass of trioctylamine, heated to 60-65 DEG C and reacted for 5-6 h, then the product was washed and dried, dispersed in 20-25 parts by mass of acetonitrile, 8-10 parts by mass of iodomethane was added, heated to 65-70 DEG C and refluxed to completely convert the tertiary amine groups to quaternary ammonium salt groups, washed with ethanol and dried to obtain a magnetic phase transfer catalyst.

4. The process for recovering waste edible oil according to claim 3, wherein The S4 refined waste oil recovery treatment is specifically as follows: 10-15 parts by mass of refined waste oil was preheated at 30-35 DEG C, then 6-8 parts by mass of sodium methoxide was added, then 1-2 parts by mass of amino acid ionic liquid and 0.2-0.3 parts by mass of magnetic phase transfer catalyst were added, and stirred at 600-700 r / min for 3-4 h, then the temperature was increased to 50-55 DEG C, and the stirring was continued for 10-15 min, then the stirring was stopped, the magnetic phase transfer catalyst in the system was attracted to the bottle wall by a strong magnet outside to form a compact deposit, the upper layer of the reaction liquid was poured into a separatory funnel to separate the magnetic phase transfer catalyst from the reaction product, the upper layer of the reaction liquid in the separatory funnel was allowed to stand for 4-5 h, and then the upper and lower layers were separated, and the lower layer was removed, and the upper layer of the oil phase was distilled under reduced pressure at 50-60 DEG C using a rotary evaporator to obtain biodiesel.

5. The process of claim 3, wherein the process is characterized by, The silane coupling agent is specifically 3-(glycidyloxypropyl)trimethoxysilane.

6. The process of claim 4, wherein the process is characterized by, The magnetic phase transfer catalyst adsorbed on the bottle wall was washed with methanol or acetone, and the adsorbed magnetic phase transfer catalyst was washed repeatedly for 5 times to wash away the residual organic matter, and then vacuum dried and stored, which can be directly used for the next reaction.

7. The process of claim 4, wherein the process is characterized by, The strong magnet is specifically a neodymium magnet.

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