Polyunsaturated fatty acid ester and monounsaturated fatty acid ester composite surfactant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of bio-based surfactants, and relates to a polyunsaturated fatty acid ester and monounsaturated fatty acid ester composite surfactant and a preparation method and application thereof. The preparation method comprises the following steps: mixing polyunsaturated fatty acid ester with monounsaturated fatty acid ester, saturated fatty acid ester and aromatic compounds; carrying out an alkylation reaction under the catalytic action of FeCl3 or methanesulfonic acid, and then sequentially carrying out an amidation reaction and a quaternization reaction to obtain the product, the molar ratio of the polyunsaturated fatty acid ester to the monounsaturated fatty acid ester is (0.1-2.6): 1. Compared with the prior art, unsaturated double bonds and hydrophilic head groups on fat long chains are subjected to alkyl modification, then the ampholytic surfactant is prepared through amidation reaction and quaternization reaction in sequence, and the interfacial tension between the ampholytic surfactant and Daqing crude oil reaches the ultralow interfacial tension level; the application of the grease with high polyunsaturated fatty acid content in the high-interfacial-activity surfactant is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of bio-based surfactants, and relates to a preparation method and application of a composite surfactant of polyunsaturated fatty acid esters and monounsaturated fatty acid esters, and in particular to a method for preparing a high-surface-active bio-based surfactant using mixed fatty acids or their derivatives with a high, medium or low ratio of polyunsaturated fatty acids to monounsaturated fatty acids as raw materials, and the application of the high-surface-active bio-based surfactant. Background Art

[0002] Since the 1950s, petrochemical resources have been the primary source for the synthesis of surfactants. Although petroleum raw materials are relatively cheap, fluctuations in oil supply can lead to unstable prices for petrochemical products, forcing surfactant manufacturers to diversify their supply chains. Since the 1990s, interest has gradually shifted to renewable raw materials. This is partly due to the recognition that oil reserves are limited and that alternative resources must be sought. Another reason is that studies have found that the use of renewable raw materials can significantly reduce CO2 emissions, which is related to carbon emissions, making them more environmentally friendly. Therefore, bio-based surfactants prepared from renewable materials such as proteins, sugars, natural oils and fats, and fatty acid derivatives of oils and fats have attracted much attention. Currently, bio-based surfactants have good application prospects because of their renewable raw materials, stable supply, and relatively good surface and interfacial properties, and can partially replace oil-based surfactants in daily life.

[0003] Chinese invention patent CN114736184A uses methyl oleate, a major component of vegetable oil, as a raw material and uses acetalization to connect aromatic aldehydes to produce a low-toxic, easily degradable bio-based surfactant. Chinese invention patent CN103342996A uses oleic acid, a major component of waste oils, to produce a simple, short-reaction, mild, and low-cost bio-based surfactant. Chinese invention patent CN113930249A uses oleic acid from animal and vegetable oils and anisole extracted from fennel as raw materials instead of benzene to produce a benzyloxy-oleoyl quaternary ammonium surfactant, which has great application potential in tertiary oil recovery.

[0004] The aforementioned bio-based surfactants are primarily based on single fatty acids or monounsaturated fatty acids and their derivatives from oils and fats. However, oil hydrolysis contains a large amount of saturated and unsaturated fatty acids, with polyunsaturated and monounsaturated fatty acids coexisting in the unsaturated fatty acids, and the ratio of polyunsaturated to monounsaturated fatty acids varies within a certain range. Using only single fatty acids or monounsaturated fatty acids as raw materials not only involves raw material separation issues but also leads to high costs. Polyunsaturated fatty acids are also widely present in nature and coexist with monounsaturated fatty acids. Using mixed fatty acids containing polyunsaturated fatty acids as raw materials would not only address the low overall utilization rate of oils and fats caused by using single fatty acids, but also avoid the high costs and waste of resources caused by the need to separate monounsaturated fatty acids as raw materials. However, studies have reported that plant oils with high monounsaturated fatty acid content, medium saturated fatty acid content, and no or low polyunsaturated fatty acid content are more suitable as surfactant raw materials, as the presence of polyunsaturated fatty acids is detrimental to the performance of surfactants. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing and applying a composite surfactant of polyunsaturated fatty acid esters and monounsaturated fatty acid esters, which is used to solve the problem of low interfacial activity in preparing surfactants using oils and fats with a high ratio of polyunsaturated fatty acids (linoleic acid) to monounsaturated fatty acids (oleic acid). The present invention alkylates the unsaturated double bonds and hydrophilic head groups on the long fatty acid chains, and then sequentially produces an amphoteric surfactant through amidation and quaternization. The interfacial tension between the surfactant and Daqing crude oil reaches an ultra-low interfacial tension level, thus enabling the application of oils and fats with a high polyunsaturated fatty acid content in highly interfacially active surfactants.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A first aspect of the present invention provides a method for preparing a composite surfactant of a polyunsaturated fatty acid ester and a monounsaturated fatty acid ester, comprising: mixing a polyunsaturated fatty acid ester with a monounsaturated fatty acid ester, a saturated fatty acid ester, and an aromatic compound, and subjecting the mixture to an alkylation reaction under the catalytic action of FeCl3 or methanesulfonic acid, followed by an amidation reaction and a quaternization reaction to obtain;

[0008] The molar ratio of the polyunsaturated fatty acid ester to the monounsaturated fatty acid ester is (0.1-2.6):1;

[0009] The aromatic compound is selected from one of benzene, toluene or anisole;

[0010] The mixture of the polyunsaturated fatty acid ester, monounsaturated fatty acid ester and saturated fatty acid ester is referred to as mixed fatty acid ester.

[0011] In some preferred technical solutions, in the preparation method, the following process conditions are obtained through orthogonal experiments, with the oil-water interfacial tension under the target environment as the performance indicator:

[0012] The amount of polyunsaturated fatty acid esters, the amount of monounsaturated fatty acid esters, the amount of saturated fatty acid esters, the type and amount of aromatic compounds, the selection and amount of FeCl3 or methanesulfonic acid, the reaction conditions of the amidation reaction, and the reaction conditions of the quaternization reaction.

[0013] In some preferred technical solutions, the molar ratio of the polyunsaturated fatty acid ester to the monounsaturated fatty acid ester is 0.236, 0.534, or 2.56. The high, medium, and low molar ratios of the polyunsaturated fatty acid (linoleic acid) to the monounsaturated fatty acid (oleic acid) are calculated based on the composition of different fatty acids in the vegetable oil and the production and consumption conditions.

[0014] In some specific embodiments, since the content of linolenic acid in the polyunsaturated fatty acid in common oils and fats is much lower than that of other fatty acids, and the content of hexadecanoic acid in the saturated fatty acid is much higher than that of other saturated fatty acids, the polyunsaturated fatty acid ester in the present invention is preferably methyl linoleate, and the monounsaturated fatty acid ester is preferably methyl oleate.

[0015] In some specific embodiments, the saturated fatty acid ester is representatively selected from methyl hexadecanoate, and the ratio of its molar amount to the total molar amount of polyunsaturated fatty acid esters and monounsaturated fatty acid esters is 1:(8-10).

[0016] In some specific embodiments, the molar ratio of the mixed fatty acid ester to the aromatic compound is 1:(5-8).

[0017] In some preferred embodiments, the molar ratio of the mixed fatty acid ester to benzene or toluene is 1:5.

[0018] In some preferred embodiments, the molar ratio of the mixed fatty acid ester to anisole is 1:8.

[0019] In some specific embodiments, in the alkylation reaction, the reaction temperature is 50-70° C., and the reaction time is 3-8 h.

[0020] In some specific embodiments, the molar ratio of the mixed fatty acid ester to FeCl3 is 1:(0.25-1).

[0021] In some specific embodiments, the molar ratio of the mixed fatty acid ester to methanesulfonic acid is 1:(1-6).

[0022] In some specific embodiments, in the amidation reaction, the amidation reagent used is selected from one of N,N-dimethylethylenediamine, N,N-dimethylpropylenediamine or N,N-diethylpropylenediamine.

[0023] In some specific embodiments, the molar ratio of the mixed fatty acid ester to the amidation agent is 1:(1-2).

[0024] In some specific embodiments, in the amidation reaction, the catalyst used is TiCl4.

[0025] In some specific embodiments, the mass ratio of the mixed fatty acid ester to TiCl4 is 1:0.001 to 1:0.01.

[0026] In some specific embodiments, in the amidation reaction, the reaction temperature is 140-170° C., and the reaction time is 4-8 h.

[0027] In some specific embodiments, in the quaternization reaction, the quaternizing agent used is selected from one of sodium 3-chloro-2-hydroxypropanesulfonate, sodium chloroacetate or butane sultone; and the molar ratio of the mixed fatty acid ester to the quaternizing agent is 1:(1-2).

[0028] In some preferred technical solutions, in the quaternization reaction, the quaternization agent is sodium 3-chloro-2-hydroxypropanesulfonate, and its usage is 13.4 g / 0.034 mol of mixed fatty acid ester.

[0029] In some preferred technical solutions, sodium carbonate is further added during the quaternization reaction, and the molar ratio of the mixed fatty acid ester to sodium carbonate is 1:0.25 to 1:2.

[0030] In some preferred technical solutions, in the quaternization reaction, the reaction solvent is a mixture of ethanol and water in a volume ratio of 1:1 to 4:1.

[0031] In some preferred technical solutions, the volume ratio of ethanol to water is 73.5:31.5.

[0032] In some preferred technical solutions, in the quaternization reaction, the reaction temperature is 65-95° C. and the reaction time is 6-12 h.

[0033] A second aspect of the present invention provides a composite surfactant of polyunsaturated fatty acid esters and monounsaturated fatty acid esters prepared by the method described above, wherein the group combination thereof is the group combination with the best interfacial activity of the composite surfactant obtained by orthogonal experiment, preferably the following compounds:

[0034]

[0035] (1) The molecular formula is C 32 H 58 O6N2SNaCl, the structural formula is shown above, the relative molecular mass is 656.5, and the maximum abundance molecular weight is 656.4;

[0036]

[0037] (2) The molecular formula is C 32 H 56 O6N2SNaCl, the structural formula is shown above, the relative molecular mass is 654.5, and the maximum abundance molecular weight is 654.3;

[0038]

[0039] (3) The molecular formula is C 23 H 48 O5N2SNaCl, with the structural formula shown above, has a relative molecular mass of 522.5 and a maximum abundance molecular weight of 522.3.

[0040] The third aspect of the present invention provides a method for preparing a composite surfactant of polyunsaturated fatty acid esters and monounsaturated fatty acid esters, comprising: subjecting an oil containing polyunsaturated fatty acids, monounsaturated fatty acids and saturated fatty acids to an ester exchange reaction with methanol, and then sequentially subjecting the oil to an alkylation reaction, an amidation reaction, and a quaternization reaction to obtain a composite surfactant.

[0041] In some specific embodiments, the preparation method includes: conducting an ester exchange reaction between different oils and methanol, and then sequentially undergoing an alkylation reaction, an amidation reaction, and a quaternization reaction to obtain; the polyunsaturated fatty acid corresponds to the polyunsaturated fatty acid ester, the monounsaturated fatty acid corresponds to the monounsaturated fatty acid ester, and the saturated fatty acid not only corresponds to the above-mentioned saturated fatty acid ester, but also includes methyl octadecanoate.

[0042] In some specific embodiments, the oil is selected from one of rapeseed oil, swill oil or soybean oil;

[0043] The molar ratio of the oil to methanol is 1:9 to 1:20;

[0044] In the transesterification reaction, the catalyst used is KOH, and the amount used is 0.1-2 wt% of the oil; the reaction temperature is 60-70° C., and the reaction time is 0.5-4 h.

[0045] A fourth aspect of the present invention provides an application of a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester prepared by the method described above, including using the composite surfactant for tertiary oil recovery.

[0046] The present invention is based on polyunsaturated fatty acid ester (methyl linoleate), and carries out alkylation reaction with monounsaturated fatty acid ester (methyl oleate), saturated fatty acid ester, and alkylating agent, thereby achieving the effective preparation of mixed fatty acid methyl ester with high polyunsaturated fatty acid content, and then obtaining high interfacial activity surfactant through amidation reaction and quaternization reaction. The interfacial tension between the surfactant and Daqing crude oil can reach ultra-low interfacial tension level, and can maintain stability within 2 hours, and has good application prospects in the field of alkali-free ultra-low interfacial tension. At the same time, the present invention also improves the comprehensive utilization rate of grease. The ratio of the raw material polyunsaturated fatty acid to monounsaturated fatty acid is wide, not only covering the common soybean oil and rapeseed oil in production and consumption, but also including the waste grease generated in the production and consumption process, and has good industrial application value.

[0047] Compared with the prior art, the present invention has the following characteristics:

[0048] The present invention designs an orthogonal experiment using mixed fatty acid methyl esters with low, medium and high ratios of polyunsaturated fatty acid to monounsaturated fatty acid content as raw materials, takes different reaction types as factors and reactants of different groups used in the same reaction type as levels, and conducts orthogonal analysis on the equilibrium oil-water interfacial tension to obtain the effects of different group structures and different fatty acid compositions on the interfacial properties of the surfactant.

[0049] Using mixed fatty acid methyl esters with low, medium, and high ratios of polyunsaturated fatty acids to monounsaturated fatty acids as raw materials, amphoteric surfactants were prepared by modifying the optimal group combinations obtained through orthogonal optimization. The surfactants have excellent interfacial activity. At 45°C, 3.0g / L and 0.50g / L of the surfactants can achieve ultra-low interfacial tension with Daqing crude oil, and the tension can be maintained for 2 hours, showing good performance in reducing interfacial tension.

[0050] The present invention uses mixed fatty acid methyl ester with a high polyunsaturated fatty acid content as a raw material and prepares a surfactant under modification of an optimal group combination. The surfactant has good interfacial performance. At 45°C, the interfacial tension between 3.0 g / L and 0.50 g / L surfactant solutions and Daqing crude oil can reach ultra-low interfacial tension and can be maintained for 2 hours. This solves the problem of poor performance of the surfactant prepared by using mixed fatty acids with a high polyunsaturated fatty acid content as a raw material, improves the comprehensive utilization rate of oils and fats, avoids the problem of separation required when a single fatty acid is used as a raw material, and reduces costs.

[0051] The raw materials of the present invention include soybean oil with a high polyunsaturated fatty acid content, rapeseed oil with a low unsaturated fatty acid content, and waste oils generated during the production and consumption of these oils. The raw materials are widely available, renewable, and have a stable supply, showing great application prospects in the field of tertiary oil recovery. Furthermore, the reuse of waste oils is in line with the concept of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a gas chromatogram of the first intermediate product in Example 3;

[0053] Figure 2-4 is the mass spectrum of the first intermediate product in Example 3 ( Figure 2 is methyl anisole octadecanoate, Figure 3 is anisole methyl oleate, Figure 4 is methyl hexadecanoate);

[0054] Figure 5 is a gas chromatogram of the second intermediate product in Example 3;

[0055] Figure 6-8 is the mass spectrum of the second intermediate product in Example 3 ( Figure 6 is anisole octadecanoic acid amide, Figure 7 is anisole oleamide, Figure 8 is palmitic acid amide);

[0056] Figure 9 is a liquid chromatogram of the amphoteric surfactant in Example 3;

[0057] Figure 10 The electrospray mass spectra of the amphoteric surfactants in Example 3 are shown in LC-MS (a and b are anisole octadecanoic acid amide hydroxysulfonic acid type surfactants, c and d are anisole oleic acid amide hydroxysulfonic acid type surfactants, and e and f are hexadecanoic acid amide hydroxysulfonic acid type surfactants);

[0058] Figure 11 is the electrospray mass spectrum of the amphoteric surfactant in Example 3;

[0059] Figure 12 is a liquid chromatogram of the amphoteric surfactant in Example 4;

[0060] Figure 13 The electrospray mass spectra of the amphoteric surfactants in Example 4 in LC-MS are shown (a and b are phenyl stearamide acetic acid type surfactants, c and d are phenyl oleamide acetic acid type surfactants, and e and f are hexadecanoic acid amide acetic acid type surfactants);

[0061] Figure 14 is the electrospray mass spectrum of the amphoteric surfactant in Example 4;

[0062] Figure 15 is a liquid chromatogram of the amphoteric surfactant in Example 8;

[0063] Figure 16 The mass spectra of the amphoteric surfactants in Example 8 (a and b are tolyl stearamide sulfonic acid type surfactants, c and d are tolyl oleamide sulfonic acid type surfactants, and e and f are hexadecanoic acid amide sulfonic acid type surfactants);

[0064] Figure 17 is the electrospray mass spectrum of the amphoteric surfactant in Example 8;

[0065] Figure 18 is the electrospray ionization mass spectrum of the amphoteric surfactant in Example 11;

[0066] Figure 19 is the electrospray mass spectrum of the amphoteric surfactant in Example 12;

[0067] Figure 20 is the electrospray mass spectrum of the amphoteric surfactant in Example 13;

[0068] Figure 21 This is a gas phase diagram of the mixed fatty acid methyl esters obtained by transesterification of rapeseed oil in Example 14;

[0069] Figure 22-25 The mass spectrum of the mixed fatty acid methyl esters obtained by transesterification of rapeseed oil in Example 14 ( Figure 22 is methyl oleate, Figure 23 Methyl linoleate, Figure 24 is methyl hexadecanoate, Figure 25 is methyl octadecanoate);

[0070] Figure 26 This is the gas phase diagram of the mixed fatty acid methyl esters obtained by transesterification of swill oil in Example 14;

[0071] Figure 27 This is a gas phase diagram of the mixed fatty acid methyl esters obtained by soybean oil transesterification in Example 14;

[0072] Figure 28 This is the electrospray ionization mass spectrum of the surfactant prepared from the raw material obtained by transesterification of rapeseed oil in Example 15;

[0073] Figure 29 This is the electrospray ionization mass spectrum of the surfactant prepared from the raw materials obtained by transesterification of swill oil in Example 15;

[0074] Figure 30 This is the electrospray ionization mass spectrum of the surfactant prepared from the raw material obtained by soybean oil transesterification in Example 15;

[0075] Figure 31 This is the interfacial tension diagram between the surfactant prepared from the mixed fatty acid methyl ester with low polyunsaturated fatty acid content in Example 16 and Daqing crude oil at 45°C;

[0076] Figure 32 This is the interfacial tension diagram between the surfactant prepared from the mixed fatty acid methyl ester with a medium polyunsaturated fatty acid content in Example 16 and Daqing crude oil at 45°C;

[0077] Figure 33 This is the interfacial tension diagram between the surfactant prepared from the mixed fatty acid methyl ester with a high polyunsaturated fatty acid content in Example 16 and Daqing crude oil at 45°C;

[0078] Figure 34 This is the interfacial tension diagram of the surfactant prepared from rapeseed oil in Example 16 and Daqing crude oil;

[0079] Figure 35 This is the interfacial tension diagram between the surfactant prepared from swill oil in Example 16 and Daqing crude oil;

[0080] Figure 36 This is the interfacial tension diagram of the surfactant prepared from soybean oil in Example 16 and Daqing crude oil. DETAILED DESCRIPTION

[0081] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0082] Based on the composition range of fatty acids in vegetable oils (Table 1), as well as the annual production and import volumes of common vegetable oils, we selected mixed fatty acids or their derivatives with low, medium, and high polyunsaturated to monounsaturated fatty acid ratios as raw materials. This wide range of raw material ratios covers not only common vegetable oils in production and consumption, but also waste oils generated during production and consumption.

[0083] Table 1 Fatty acid composition in vegetable oils (mol%)

[0084]

[0085] Table 2 Orthogonal experimental design table

[0086]

[0087]

[0088] The orthogonal optimization of the group combination was performed by orthogonal experiment (the specific orthogonal combination design is shown in Table 2), and mixed fatty acid methyl esters with low, medium, and high polyunsaturated fatty acid to monounsaturated fatty acid content ratios were used as raw materials. The amphoteric surfactant was prepared by double bond modification of the optimal group, amidation, and quaternization. The specific preparation method of the amphoteric surfactant includes the following steps:

[0089] (1) reacting mixed fatty acid methyl esters having low, medium, and high polyunsaturated fatty acid to monounsaturated fatty acid content ratios with anisole at 50° C. to 70° C. using FeCl 3 as an auxiliary agent to obtain a first intermediate product;

[0090] (2) mixing the first intermediate product with N,N-dimethylethylenediamine, reacting at 140°C to 170°C for 4h to 8h with TiCl4 as an auxiliary agent to obtain a second intermediate product;

[0091] (3) The second intermediate product is mixed with sodium 3-chloro-2-hydroxypropanesulfonate, water, ethanol, and Na2CO3, and reacted at 65°C to 95°C for 6h to 12h to obtain the surfactant.

[0092] As for the separation and purification method of the reaction products, after the alkylation reaction, the excess FeCl3 is removed by centrifugation, the product is washed with water until neutral and the excess alkylating agent is removed by distillation under reduced pressure. After the amidation reaction, the excess diamine is removed by distillation under reduced pressure. After the quaternization reaction, the water and ethanol in the solution are first evaporated, and then dissolved with ethanol, the salt in the surfactant is removed by centrifugation, and the excess ethanol is evaporated.

[0093] The application prospect of this surfactant is in the field of preparing bio-based surfactants with high interfacial activity.

[0094] This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0095] The following are more detailed implementation cases, which further illustrate the technical solutions of the present invention and the technical effects that can be obtained.

[0096] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercially available products or conventional processing techniques in the art.

[0097] Example 1

[0098] A phenyl stearamide sulfonic acid surfactant prepared from a mixed fatty acid methyl ester having a low ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, wherein the preparation method comprises the following steps:

[0099] S1: Weigh 8.443mL of methyl oleate, 1.925mL of methyl linoleate, and 1.16mL of methyl hexadecanoate as raw materials (the total molar amount of the three ester compounds is 0.034mol, and the molar ratio of polyunsaturated fatty acids to monounsaturated fatty acids is 0.236), add 15mL (0.17mol) of benzene and 13.23mL (0.204mol) of methanesulfonic acid (the molar ratio of the raw material mixed fatty acid methyl ester to benzene to methanesulfonic acid is 1:5:6, respectively), and react at 65°C for 6h. After the reaction is completed, the alkylated product is transferred to a separatory funnel, and appropriate amounts of ethyl acetate and water are added to extract the separated liquids. After washing with water until the water layer is neutral, a small amount of water in the organic layer is absorbed with Na2SO4, and the solution is then distilled under reduced pressure to remove excess benzene and ethyl acetate to obtain the first intermediate product, phenyl fatty acid methyl ester.

[0100] S2: The above-mentioned phenyl fatty acid methyl ester was reacted with 6.08 mL (0.068 mol) of N,N-dimethylethylenediamine (the molar ratio of the raw material mixed fatty acid methyl ester to N,N-dimethylethylenediamine was 1:2) and 58 μL of TiCl4 (the mass ratio of the raw material mixed fatty acid methyl ester to the catalyst TiCl4 was 1:1 wt%) at 160°C for 6 h. After the reaction, the solvent was removed by distillation under reduced pressure to obtain the second intermediate product, phenyl fatty acid amide.

[0101] S3: The above phenyl fatty acid amide, 13.368g sodium 3-chloro-2-hydroxypropanesulfonate (0.068mol, with the raw material molar ratio of 1:2), 3.604g Na2CO3 (0.068mol, with the mixed fatty acid methyl ester raw material molar ratio of 1:2) and 73.5mL ethanol, 31.5mL water (V 醇 / V 水 The mixture was stirred at 75°C for 8 hours. The excess water and ethanol were then distilled off under reduced pressure, and the product was dissolved in anhydrous ethanol. The salt in the product was insoluble in ethanol. The product was separated by centrifugation, and the upper clear layer was collected and the ethanol was removed by rotary evaporation to obtain the final product.

[0102] Example 2

[0103] A tolyl stearamide sulfonic acid surfactant prepared from a mixed fatty acid methyl ester having a low ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, wherein the preparation method thereof is different from that of Example 1 in that:

[0104] In step S1, 18.1 mL of toluene (0.17 mol) was used instead of 15 mL of benzene; the amount of methanesulfonic acid used was 13.2 mL (0.204 mol) (the molar ratio of the raw material mixed fatty acid methyl ester: toluene: methanesulfonic acid was 1:5:6); the first intermediate product obtained was tolyl fatty acid methyl ester;

[0105] In step S2, 8.49 mL of N,N-dimethylpropylenediamine (0.068 mol) was used instead of N,N-dimethylethylenediamine (the molar ratio of the raw material mixed fatty acid methyl ester to N,N-dimethylpropylenediamine was 1:2), and the obtained second intermediate product was toluyl fatty amide;

[0106] In step S3, the amount of sodium 3-chloro-2-hydroxypropanesulfonate used is 13.4 g (0.068 mol), and the amount of Na2CO3 used is 3.60 g (0.068 mol). The rest is the same as in Example 1.

[0107] Example 3

[0108] A methylbenzene octadecanoic acid surfactant prepared from a mixed fatty acid methyl ester having a low ratio of polyunsaturated fatty acids to monounsaturated fatty acids, wherein the preparation method thereof is different from that of Example 1 in that:

[0109] In step S1, 29.5 mL of anisole (0.272 mol) is used instead of benzene, and 5.50 g of FeCl3 (0.034 mol) is used instead of methanesulfonic acid (the raw material mixed fatty acid methyl ester: anisole: FeCl3 molar ratio is 1:8:1); the resulting reaction product mixture is centrifuged and the precipitate is removed. The supernatant is extracted with 20 mL of water and 20 mL of ethyl acetate. After centrifugation, the upper organic phase is allowed to stand and the organic phase is washed three times with a water-ethyl acetate solution. The washed organic phase is collected and the ethyl acetate is evaporated to obtain the first intermediate product, anisole fatty acid methyl ester.

[0110] Wherein, the GC chromatogram of the first intermediate product is as shown in the attached Figure 1 Its mass spectrum is shown in the attached Figure 2 The detection conditions included: injection volume 1 μL, split ratio 20:1, detector temperature 290°C. The column oven temperature was set at 260°C for 2 minutes, then ramped to 290°C at a rate of 20°C / min. The column was then run for 30 minutes.

[0111] In step S2, 11.1 mL of N,N-diethylpropylenediamine (0.068 mol) was used instead of 6.08 mL of N,N-dimethylethylenediamine; the obtained second intermediate product was anisole fatty amide.

[0112] Wherein, the GC chromatogram of anisole fatty amide is as shown in the attached figure. Figure 3 Its mass spectrum is shown in the attached Figure 4 The detection conditions included: injection volume 1 μL, split ratio 20:1, detector temperature 290°C. The column oven temperature was set at 260°C for 2 minutes, then ramped to 290°C at a rate of 20°C / min. The column was then run for 100 minutes.

[0113] In step S3, the final product obtained is an anisole-based fatty amide sulfonic acid type amphoteric surfactant.

[0114] Among them, the LC-MS UV detection diagram of the product is as follows Figure 5 As shown in the mass spectrum Figure 6 The detection conditions included: injection volume: 10 μL; detection wavelength: scanning within the wavelength range of 200-600 nm; flow rate: 0.40 mL / min; gradient conditions: 0-8 min, 80% methanol, 8-28 min, 80-100% methanol, 28-80 min, 100% methanol.

[0115] The electrospray mass spectrum of anisole fatty amide sulfonic acid type amphoteric surfactant is shown in the attached figure. Figure 7 The rest is the same as in Example 1.

[0116] Example 4

[0117] A phenyl stearamide acetic acid type surfactant using a mixed fatty acid methyl ester with a medium ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, and a preparation method thereof comprises the following steps:

[0118] In step S1, the amount of methyl oleate is 6.79 mL, the amount of methyl linoleate is 3.50 mL, and the amount of methyl hexadecanoate is 1.16 mL (the total molar amount of the three ester compounds is 0.034 mol, 0.31:0.58:0.11, and the molar ratio of polyunsaturated fatty acid to monounsaturated fatty acid content is 0.534); the amount of benzene is 7.5 mL (0.085 mol), and the amount of methanesulfonic acid is 6.62 mL (0.102 mol) (mixed fatty acid methyl ester raw material: benzene: methanesulfonic acid molar ratio is 1:2.5:3); the reaction temperature is 50 ° C, and the reaction time is 8 h; the first intermediate product obtained is phenyl fatty acid methyl ester;

[0119] In step S2, the amount of the amidation reagent N,N-dimethylpropylenediamine used is 4.25 mL (0.034 mol) (mixed fatty acid methyl ester raw material: N,N-dimethylpropylenediamine molar ratio = 1:1), and the amount of the amidation catalyst TiCl4 used is 29 μL (the mass ratio of the raw material mixed fatty acid methyl ester to the amidation catalyst TiCl4 is 1:0.5 wt%); the reaction temperature is 170°C and the reaction is carried out for 4 hours;

[0120] In step S3, the amount of quaternizing agent sodium chloroacetate is 5.94g (0.051mol), the amount of quaternizing catalyst Na2CO3 is 2.70g (0.051mol) (mixed fatty acid methyl ester raw material: sodium chloroacetate: Na2CO3 molar ratio is 1:1.5:1.5), the amount of ethanol is 84.0mL, and the amount of water is 21.0mL; the reaction temperature is 65°C, and the reaction time is 12h; the resulting product is a phenyl fatty amide acetic acid type amphoteric surfactant. The UV detection diagram of LC-MS is shown in the attached figure. Figure 8 The mass spectrum is shown in the attached Figure 9 The detection conditions included: injection volume: 10 μL; detection wavelength: scanning within the wavelength range of 200-600 nm; flow rate: 0.40 mL / min; gradient conditions: 0-8 min, 80% methanol, 8-28 min, 80-100% methanol, 28-80 min, 100% methanol.

[0121] The electrospray mass spectrometry of phenyl fatty acid amide acetic acid type amphoteric surfactant is as follows Figure 10 shown.

[0122] Example 5

[0123] A tolyl stearamide sulfonic acid surfactant using a mixed fatty acid methyl ester with a moderate ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, the preparation method of which is different from that of Example 4 only in that:

[0124] In step S1, 8.97 mL of toluene (0.085 mol) was used instead of benzene; the amount of methanesulfonic acid used was 6.62 mL (0.102 mol); the reaction temperature was 50° C., and the reaction time was 8 h;

[0125] In step S2, 3.04 mL of N,N-dimethylethylenediamine (0.034 mol) was used instead of N,N-dimethylpropylenediamine;

[0126] In step S3, 5.34 mL of butane sultone (0.051 mol) was used instead of sodium chloroacetate, and the resulting product was a toluene fatty amide sulfonic acid type amphoteric surfactant.

[0127] Example 6

[0128] A methylbenzene octadecanoic acid surfactant prepared from a mixed fatty acid methyl ester having a moderate ratio of polyunsaturated fatty acids to monounsaturated fatty acids. The preparation method thereof is different from that of Example 4 in that:

[0129] In step S1, 14.8 mL of anisole (0.136 mol) was used instead of toluene, and 2.75 g of FeCl3 (0.017 mol) was used instead of methanesulfonic acid. After the reaction was completed, the reaction was centrifuged and the precipitate was removed. The supernatant was extracted with 20.0 mL of water and 20.0 mL of ethyl acetate. After centrifugation, the upper organic phase was allowed to stand, and a water-ethyl acetate solution was added to wash the organic phase three times. The washed organic phase was collected and ethyl acetate was evaporated to obtain anisole fatty acid methyl ester.

[0130] In step S2, 5.54 mL of N,N-diethylpropylenediamine (0.034 mol) was used to replace N,N-dimethylethylenediamine, and the second intermediate product obtained was anisole fatty amide.

[0131] In step S3, 6.68 g of sodium 3-chloro-2-hydroxypropanesulfonate (0.034 mol) was used instead of sodium chloroacetate. The resulting product was an anisole-based fatty amide sulfonic acid type amphoteric surfactant. The rest of the steps were the same as in Example 4.

[0132] Example 7

[0133] A phenyl stearamide sulfonic acid surfactant using a mixed fatty acid methyl ester having a high ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, and a preparation method thereof comprising:

[0134] In step S1, the amount of methyl oleate is 2.93 mL, the amount of methyl linoleate is 7.25 mL, and the amount of methyl hexadecanoate is 1.16 mL (the total molar amount of the three ester compounds is 0.034 mol, 0.64:0.25:0.11, and the molar ratio of polyunsaturated fatty acid to monounsaturated fatty acid content is 2.56); the amount of benzene is 3 mL (0.034 mol); the amount of methanesulfonic acid is 2.21 mL (0.034 mol) (the molar ratio of raw material mixed fatty acid methyl ester: benzene: methanesulfonic acid is 1:1:1); the reaction temperature is 70 ° C, and the reaction time is 3 h;

[0135] In step S2, the amount of the amidation reagent N,N-diethylpropylenediamine used is 8.30 mL (0.051 mol) (the molar ratio of the raw material mixed fatty acid methyl ester: N,N-diethylpropylenediamine is 1:1.5), the amount of TiCl4 used is 6 μL; the reaction temperature is 140° C., and the reaction time is 8 h;

[0136] In step S3, the amount of the quaternizing agent butane sultone used is 3.56 mL (0.034 mol), the amount of Na2CO3 used is 0.450 g (0.0085 mol) (mixed fatty acid methyl ester raw material: butane sultone: Na2CO3 molar ratio = 1:1:0.25), the amount of ethanol used is 52.5 mL, and the amount of water used is 52.5 mL; the reaction temperature is 95°C, and the reaction time is 6 hours. The resulting product is a phenyl fatty amide sulfonic acid type amphoteric surfactant.

[0137] Example 8

[0138] A phenyl octadecylamide sulfonic acid surfactant using a mixed fatty acid methyl ester having a high ratio of polyunsaturated fatty acids to monounsaturated fatty acids as a raw material, the preparation method of which differs from that of Example 7 only in that:

[0139] In step S1, 3.60 mL of toluene (0.034 mol) was used instead of benzene. The first intermediate product obtained was toluene fatty acid methyl ester;

[0140] In step S2, 4.56 mL of N,N-dimethylethylenediamine (0.051 mol) was used instead of N,N-diethylpropylenediamine; the reaction temperature was 170°C and the reaction time was 6 h. The resulting second intermediate product was toluene fatty acid amide.

[0141] In step S3, the quaternary ammonium reagent used was 3.56 mL of butane sultone (0.034 mol), the amount of Na2CO3 used was 1.80 g (0.034 mol), the reaction temperature was 75°C, and the reaction time was 8 h. The volumes of ethanol and water in the solvent were both 52.5 mL. The UV detection graph of the LC-MS of the obtained toluene fatty amide sulfonic acid type amphoteric surfactant is shown in the attached figure. Figure 11 The mass spectrum is shown in the attached Figure 12 The detection conditions are the same as those in Example 3. The electrospray mass spectrometer is shown in the attached figure. Figure 13 The rest is the same as in Example 7.

[0142] Example 9

[0143] A methylbenzene octadecanoic acid surfactant prepared from a mixed fatty acid methyl ester having a high ratio of polyunsaturated fatty acids to monounsaturated fatty acids, wherein the preparation method thereof is different from that of Example 7 in that:

[0144] In step S1, 3.69mL anisole (0.034mol) is adopted to replace benzene. 1.38g FeCl3 (0.0085mol) is adopted to replace methanesulfonic acid. The reaction times is 5h. After reaction terminates, centrifuge and remove precipitation. Supernatant adds 20mL water and 20mL ethyl acetate extraction, stands after centrifugation and takes upper organic phase, then adds water-ethyl acetate solution to wash organic phase three times, collects washed organic phase and steams off ethyl acetate to obtain anisole fatty acid methyl ester.

[0145] In step S2, 6.42 mL of N,N-dimethylpropylenediamine (0.051 mol) was used instead of N,N-diethylpropylenediamine, the reaction temperature was 170° C., the reaction time was 6 h, and the obtained second intermediate product was anisole fatty amide.

[0146] In step S3, the quaternizing agent is butane sultone, the amount of Na2CO3 used is 0.90 g, and the resulting product is an anisole-based fatty amide sulfonic acid type amphoteric surfactant. The rest is the same as in Example 7.

[0147] Example 10

[0148] This example was used to test the oil-water interfacial tension of surfactants prepared from mixed fatty acid methyl esters with different ratios of polyunsaturated fatty acids to monounsaturated fatty acids in Examples 1-9 under different group combinations with Daqing crude oil over a 2-hour period. The statistical results of the equilibrium interfacial tension at 2 hours are shown in the following table. Surfactants prepared from combinations with high polyunsaturated fatty acid content in the raw materials generally had larger equilibrium interfacial tension values and poorer interfacial properties.

[0149] Table 2 IFT of surfactants prepared in the above 9 examples with Daqing crude oil at 2h equ

[0150]

[0151]

[0152] Example 11

[0153] By performing orthogonal analysis on the oil-water interface properties of each surfactant synthesized in orthogonal synthesis, an anisole-based fatty acid amide sulfonic acid surfactant prepared from a mixed fatty acid methyl ester with a low ratio of polyunsaturated fatty acids to monounsaturated fatty acids under optimal group combination modification is obtained. The preparation method comprises the following steps:

[0154] S1: Weigh 8.44mL methyl oleate, 1.93mL methyl linoleate, 1.16mL methyl hexadecanoate as raw materials (the total molar amount of the three ester compounds is about 0.034mol, and the molar ratio is 0.72:0.17:0.11), add 29.5mL (0.272mol) anisole, 5.50g (0.034mol) FeCl3, and react at 65°C for 6h. After completion of the reaction, centrifuge and remove the precipitate. The supernatant is extracted with 20.0mL water and 20.0mL ethyl acetate, and the upper organic phase is allowed to stand after centrifugation. Water-ethyl acetate solution is added to wash the organic phase three times, the washed organic phase is collected and ethyl acetate is evaporated to obtain anisole fatty acid methyl ester.

[0155] S2: The above-mentioned anisole fatty acid methyl ester, 6.08 mL of N,N-dimethylethylenediamine (0.068 mol), and 58.0 μL of TiCl₄ were reacted at 160°C for 6 h. After the reaction, the solvent was removed by distillation under reduced pressure to obtain the second intermediate product, toluene fatty acid amide.

[0156] S3: The above-mentioned anisole fatty amide was mixed with 13.4 g of sodium 3-chloro-2-hydroxypropanesulfonate (0.068 mol), 3.60 g of Na2CO3 (0.068 mol), 73.5 mL of ethanol, and 31.5 mL of water, and the mixture was reacted at 75°C for 8 h. Excess water and ethanol were then removed by distillation under reduced pressure, and the mixture was dissolved in anhydrous ethanol. The salt in the product was insoluble in ethanol. The product was separated by centrifugation, and the upper clear layer was taken and the ethanol was removed by rotary evaporation to obtain anisole fatty amide sulfonic acid type amphoteric surfactant. Its electrospray ionization mass spectrum is shown in the attached figure. Figure 14 shown.

[0157] Example 12

[0158] The preparation method of the anisole-based fatty acid amide sulfonic acid surfactant prepared from a mixed fatty acid methyl ester with a moderate ratio of polyunsaturated fatty acids to monounsaturated fatty acids under optimal group combination modification is different from that of Example 11 only in that:

[0159] S1: The raw materials are 6.79 mL of methyl oleate, 3.50 mL of methyl linoleate, and 1.16 mL of methyl hexadecanoate (the total molar amount of the three ester compounds is 0.034 mol, and the molar ratio is 0.58:0.31:0.11), 29.5 mL of anisole (0.272 mol), 5.50 g of FeCl3 (0.034 mol), and the reaction is carried out at 65 ° C for 6 h.

[0160] Steps S2 and S3 are consistent with those in Example 11. The electrospray mass spectrometry of the anisole-based fatty acid amide sulfonic acid surfactant prepared using fatty acid methyl esters with a medium ratio of polyunsaturated fatty acids to monounsaturated fatty acids as raw materials is shown in the attached figure. Figure 15 as shown

[0161] Example 13

[0162] The preparation method of the anisole-based fatty amide sulfonic acid surfactant prepared from a mixed fatty acid methyl ester with a high ratio of polyunsaturated fatty acids to monounsaturated fatty acids under the modification of the optimal group combination is different from that of Example 11 as follows:

[0163] S1: Weigh 2.93 mL of methyl oleate, 7.25 mL of methyl linoleate, and 1.16 mL of methyl palmitate as raw materials (the total molar amount of the three ester compounds is 0.034 mol, and the molar ratio is 0.25:0.64:0.11), add 29.5 mL of anisole (0.272 mol), and 5.50 g of FeCl3 (0.034 mol), and react at 65 °C for 6 h.

[0164] Steps S2 and S3 are the same as those in Example 11. The electrospray mass spectrum of the anisole-based fatty amide sulfonic acid surfactant prepared from the fatty acid methyl ester with a high ratio of polyunsaturated fatty acids to monounsaturated fatty acids obtained here is as shown in the appendix Figure 16 as shown

[0165] Example 14

[0166] Table 4 Reaction conditions for verifying the practical applicability of the optimal combination using oils and fats as raw materials

[0167]

[0168] *The mass dosage of KOH relative to the total mass of oils and fats and methanol.

[0169] According to Table 1, three kinds of oils and fats: rapeseed oil (Yihai Kerry Golden Arowana Food Group Co., Ltd.), soybean oil (Yihai Kerry Golden Arowana Food Group Co., Ltd.), and swill oil (provided by Daqing Huali Biotechnology Co., Ltd.) are respectively heated and reacted with methanol under the catalysis of KOH. After the reaction, the lower-layer glycerol is removed, the upper-layer clear liquid is taken, methanol is evaporated and recovered, cooled, and washed with water to neutrality in a separating funnel. The organic phase is dehydrated by adding 2 vol% of anhydrous sodium sulfate to obtain mixed fatty acid methyl esters with low, medium, and high contents of polyunsaturated fatty acids and monounsaturated fatty acids. The GC chromatograms of the mixed fatty acid methyl esters obtained by transesterification with rapeseed oil, swill oil, and soybean oil are respectively as shown in the appendix Figure 17 and Figure 19 and Figure 20 as shown. Their mass spectra are as shown in the appendix Figure 18As shown. The detection conditions include: injection volume of 1 μL, split ratio of 20:1, detector temperature of 290 °C. The initial temperature of the column oven is 200 °C, held for 2 min, with a heating rate of 20 °C per minute, heated to 290 °C, and run for 10 min under this condition.

[0170] Example 15

[0171] In this example, the mixed fatty acid methyl esters with low, medium, and high ratios of polyunsaturated fatty acids to monounsaturated fatty acids obtained from the transesterification of different oils in Example 13 were used to replace the anisole-based fatty acid methyl esters in Example 11, Example 12, and Example 13 respectively, and according to the subsequent steps of the corresponding examples, amphoteric surfactants were prepared by alkylation, amidation, and quaternization in sequence. Their electrospray mass spectra are respectively as shown in the appendix Figure 21 , Figure 22 , Figure 23 shown.

[0172] Example 16

[0173] This example is used to test the oil-water interfacial tension of the amphoteric surfactants prepared from the mixed fatty acid methyl esters with low, medium, and high ratios of polyunsaturated fatty acids to monounsaturated fatty acids in Example 11, 12, and 13 to evaluate their interfacial properties, and the oil-water interfacial tension of the amphoteric surfactants prepared from rapeseed oil, waste oil, and soybean oil in Example 14 to evaluate their interfacial properties. The specific test method is as follows: The oil phase is selected as Daqing Xingwu No. 5 crude oil (crude oil produced from the Xingwu No. 5 area of Daqing), and the solution is Daqing simulated formation aqueous solution (the solution ratio is shown in the following table). The changes in the oil-water interfacial tension of the simulated formation aqueous solution of the surfactant at 3.0 g / L and 0.50 g / L and Daqing crude oil (the volume ratio of the simulated formation aqueous solution to Daqing crude oil is 1.5 mL:1 μL) within two hours are tested respectively at 45 °C. The test results of the interfacial properties of the surfactant directly using the mixed fatty acid methyl ester as the raw material are as shown in the appendix Figure 24 , 25, 26 shown, and the test results of the oil-water interfacial properties of the amphoteric surfactant prepared by the transesterification reaction of the corresponding oil are as shown in the appendix Figure 27 , 28, 29 shown. The surfactants with different structures prepared from these different raw materials can all reach an ultra-low interfacial tension within two hours. Among them, the raw materials with a high content of polyunsaturated fatty acids (Example 13 and soybean oil as the raw material in Example 14) can also reach an ultra-low interfacial tension within two hours under the modification of the optimal group combination, solving the problem of the difficulty in preparing high-interfacial-activity surfactants from raw materials with a high content of polyunsaturated fatty acid methyl esters, and having good application prospects in the field of tertiary oil recovery.

[0174] Table 5 Ion composition in Daqing simulated formation water

[0175]

[0176] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester, characterized in that: include: The polyunsaturated fatty acid ester is mixed with the monounsaturated fatty acid ester, the saturated fatty acid ester and the aromatic compound, and an alkylation reaction is carried out under the catalysis of FeCl3 or methanesulfonic acid, followed by an amidation reaction and a quaternization reaction to obtain; The molar ratio of the polyunsaturated fatty acid ester to the monounsaturated fatty acid ester is (0.1-2.6):1; The aromatic compound is selected from one of benzene, toluene or anisole; The mixture of the polyunsaturated fatty acid ester, monounsaturated fatty acid ester and saturated fatty acid ester is referred to as mixed fatty acid ester.

2. The method for preparing a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester according to claim 1, wherein In this preparation method, the following process conditions were obtained through orthogonal experiments, with the oil-water interfacial tension under the target environment as the optimized performance indicator: The amount of polyunsaturated fatty acid esters, the amount of monounsaturated fatty acid esters, the amount of saturated fatty acid esters, the type and amount of aromatic compounds, the selection and amount of FeCl3 or methanesulfonic acid, the reaction conditions of the amidation reaction, and the reaction conditions of the quaternization reaction.

3. The preparation method of the polyunsaturated fatty acid ester and monounsaturated fatty acid ester composite surfactant according to claim 1, wherein The polyunsaturated fatty acid ester is methyl linoleate, and the monounsaturated fatty acid ester is methyl oleate; The saturated fatty acid ester is methyl hexadecanoate, and the ratio of the molar amount of the saturated fatty acid ester to the total molar amount of the polyunsaturated fatty acid ester and the monounsaturated fatty acid ester is 1:(8-10).

4. The method for preparing a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester according to claim 1, wherein The molar ratio of the mixed fatty acid ester to the aromatic compound is 1:(5-8); Preferably, the molar ratio of the mixed fatty acid ester to benzene or toluene is 1:5; The ratio of the total molar amount of the mixed fatty acid ester to the molar amount of anisole is 1:

8.

5. The method for preparing a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester according to claim 1, wherein In the alkylation reaction, the reaction temperature is 50-70°C and the reaction time is 3-8h; The molar ratio of FeCl3 to mixed fatty acid ester is (0.25-1):1; The molar ratio of the methanesulfonic acid to the mixed fatty acid ester is (1-6):

1.

6. The method for preparing the composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester according to claim 1, wherein In the amidation reaction, the amidation reagent used is selected from one of N,N-dimethylethylenediamine, N,N-dimethylpropylenediamine or N,N-diethylpropylenediamine; the molar ratio of the mixed fatty acid ester to the amidation reagent is 1:(1-2); The agent is TiCl4, and the mass ratio of TiCl4 to mixed fatty acid ester is (0.1wt% to 1wt%):1; The reaction temperature is 140-170°C and the reaction time is 4-8 hours; In the quaternization reaction, the quaternizing agent used is selected from one of sodium 3-chloro-2-hydroxypropanesulfonate, sodium chloroacetate or butane sultone; the molar ratio of the mixed fatty acid ester to the quaternizing agent is 1:(1-2); The reaction solvent is a mixture of ethanol and water in a volume ratio of 1:1 to 4:1; The reaction temperature is 65-95°C, and the reaction time is 6-12h.

7. A composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester prepared by the method according to any one of claims 1 to 6, characterized in that: The complex surfactant comprises the following compounds: (1) The molecular formula is C 32 H 58 O6N2SNaCl, the structural formula is shown above, the relative molecular mass is 656.5, and the maximum abundance molecular weight is 656.4; (2) The molecular formula is C 32 H 56 O6N2SNaCl, the structural formula is shown above, the relative molecular mass is 654.5, and the maximum abundance molecular weight is 654.3; (3) The molecular formula is C 23 H 48 O5N2SNaCl, with the structural formula shown above, has a relative molecular mass of 522.5 and a maximum abundance molecular weight of 522.

3.

8. A method for preparing a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester, characterized in that: include: The oil containing polyunsaturated fatty acids, monounsaturated fatty acids and saturated fatty acids is subjected to an ester exchange reaction with methanol, and then subjected to an alkylation reaction, an amidation reaction and a quaternization reaction in sequence to obtain the product.

9. The method for preparing the composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester according to claim 8, wherein The oil is selected from one of rapeseed oil, swill oil or soybean oil; The molar ratio of the oil to methanol is 1:9 to 1:20; In the transesterification reaction, the catalyst used is KOH, and the amount used is 0.1-2 wt% of the oil; the reaction temperature is 60-70° C., and the reaction time is 0.5-4 h.

10. An application of a composite surfactant of polyunsaturated fatty acid ester and monounsaturated fatty acid ester, characterized in that: The complex surfactant is a complex surfactant prepared by the method according to any one of claims 1 to 6, 8, and 9, or the complex surfactant according to claim 7; The composite surfactant is used for tertiary oil recovery.

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