Oligomeric bio-based surfactant as well as preparation method and application thereof

Abstract

The invention relates to an oligomeric bio-based surfactant and a preparation method and application thereof, the oligomeric bio-based surfactant has a structure as shown in the following formula 1 or formula 2: # imgabs0 # imgabs1 # X1-X2 are selected from-(CH2) n-or substituted or unsubstituted thienyl with the carbon atom number of 4-10, n represents the number of CH2, and n is any integer selected from 0-12; z1-Z5 are respectively and independently selected from a disaccharide group, R1-R5 are respectively and independently selected from-CH (CH3)-Y-COOH, and Y is selected from a saturated or unsaturated linear alkyl group with the carbon atom number of 9-19. Compared with unmodified sophorolipid, the sophorolipid is modified. The oligomeric bio-based surfactant disclosed by the invention has a lower contact angle and higher wettability; meanwhile, molecules have a branched space structure and intramolecular sugar ring steric hindrance, fusion of foams can be promoted, the low-foam characteristic is shown, and the low-foam bio-based cleaning agent has a good industrial application prospect as a green and efficient low-foam bio-based cleaning agent.

Description

Technical Field

[0001] The present disclosure relates to a surfactant, and in particular, to an oligomeric bio-based surfactant and a preparation method and application thereof. Background Art

[0002] Surfactants are a class of amphiphilic compounds that contain both a hydrophilic head group and a hydrophobic tail chain in the molecule. They have unique functions such as foaming, wetting, solubilization, and emulsification. The raw materials used in the preparation process of traditional surfactants are traced back to petroleum refining products, which leads to poor biodegradability and becomes a difficult-to-treat environmental pollutant. In recent years, bio-based surfactants such as sophorolipids and rhamnolipids obtained by biological fermentation have been regarded as alternative materials to traditional petroleum-based synthetic surfactants due to their green, non-toxic, easy to degrade, and high efficiency. They have also gradually begun to be used in industrial cleaning, daily chemicals, oil production, environmental protection (especially soil leaching), medicine and other fields. At present, although the cost of bio-fermentation products is within a controllable range, the price is still relatively high, ranging from 2 to 5 times the price of petroleum-based synthetic surfactant materials. How to improve the application efficiency of bio-based surfactants and reduce the dosage of agents is very critical to the industrial promotion and application of such surfactants.

[0003] Stevens' research group reported a series of new dimeric sophorolipids (ACS Sustainable Chemistry & Engineering, 2018, 6, 7, 8992-9005.), and evaluated the antibacterial and transfection properties of this type of new dimeric sophorolipids. The synthesis steps of dimeric sophorolipids reported in the literature require at least 4 to 6 steps, including the ester exchange ring opening of sophorolipids, esterification protection of sugar ring hydroxyl groups, the conversion of tail chain ester groups to aldehyde groups, condensation of aldehyde groups with alkylamines to form Schiff bases, and subsequent reduction, deprotection of sugar ring hydroxyl groups of the reduced products, and quaternization of tertiary amine linking groups. Obviously, this method has many reaction steps, resulting in a low overall yield, and industrial amplification is difficult to achieve. At the same time, the application performance of dimeric sophorolipid products in water, such as foaming and cleaning, has not been evaluated, and the advantages of low consumption and high efficiency of dimer products have not been presented, so its potential applications still need to be further explored.

[0004] In addition, in the field of industrial cleaning or soil washing, the large amount of foam generated by surfactants is difficult to handle, which will greatly increase the difficulty of post-processing of the cleaning or washing process. Therefore, low-foaming surfactants are preferred as cleaning agents or washing agents. However, so far, there is a lack of comprehensive evaluation of the foaming and cleaning capabilities of biosurfactants (sophorolipids, rhamnolipids, lipopeptides) or their modified products, so it is impossible to optimize the relevant products. Summary of the invention

[0005] The purpose of the present disclosure is to provide an oligomeric bio-based surfactant and a preparation method and application thereof. The oligomeric bio-based surfactant provided by the present disclosure has a branched spatial structure and has a stronger ability to strip the oil phase. When it is used to clean oily soil, it has a good cleaning effect, with a cleaning efficiency of more than 85%, and almost no foaming, reducing the difficulty of subsequent elution.

[0006] In order to achieve the above-mentioned object, the present disclosure provides, in a first aspect, an oligomeric bio-based surfactant, wherein the oligomeric bio-based surfactant has a structure as shown in Formula 1 or Formula 2:

[0007]

[0008] X1~X2 is selected from -(CH2) n -or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, n represents the number of CH2, and n is selected from any integer from 0 to 12; Z1 to Z5 are each independently selected from a disaccharide group, R1 to R5 are each independently selected from -CH(CH3)-Y-COOH, wherein Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms.

[0009] Optionally, Z1 to Z4 are each independently selected from the following groups: in Indicates the chemical bond connecting Z1~Z4 and R1~R4; -* indicates that Z1~Z4 and or Chemical bonds connected.

[0010] Optionally, Z5 is selected from in Indicates the chemical bond connecting Z5 and R5; —* indicates that Z5 and Chemical bonds connected.

[0011] Optionally, the oligomeric bio-based surfactant has a structure as shown in the following formulas (I) to (VI):

[0012]

[0013] Optionally, X1 to X2 are selected from -(CH2) n -, n is selected from any integer of 0 to 10, preferably, n is selected from any integer of 0 to 3; when X1 to X2 are selected from substituted or unsubstituted thienylene groups having 4 to 10 carbon atoms, the thienylene group is selected from a substituted or unsubstituted group W, wherein the unsubstituted group W is selected from the group consisting of the following groups: in represents a chemical bond; the substituted group W has one or more substituents, each of which is independently selected from deuterium, fluorine, cyano, methyl, ethyl, n-propyl, isopropyl or tert-butyl; preferably, X1 to X2 are selected from The Y is selected from -(CH2)9-, -(CH2)6CH=CH(CH2)7- or -(CH2)3CH=CHCH2CH=CH(CH2)7-.

[0014] Optionally, the oligomeric bio-based surfactant has a foaming height of less than 10 mL; a foam stabilization time of less than 60 s; and a contact angle of less than 20°.

[0015] A second aspect of the present disclosure provides a method for preparing an oligomeric bio-based surfactant, the method comprising:

[0016] (1) preparing a sophorolipid aqueous solution, adjusting the pH of the sophorolipid aqueous solution to 1.0 to 5.0 with an acid, and performing a first stirring to obtain a first solution;

[0017] (2) contacting the first solution with an aldehyde cross-linking agent to obtain a second solution; adjusting the pH of the second solution to 7.0 to 8.5 with a base, and performing a second stirring;

[0018] The sophorolipids include acid-type sophorolipids and / or lactone-type sophorolipids, and the acid-type sophorolipids have a structure shown in Formula 3: The lactone-type sophorolipid has a structure shown in Formula 4: Wherein RZ- is selected from R1-Z1-, R2-Z2-, R3-Z3-, R4-Z4- or R5-Z5-, Z' and Z1 to Z5 are each independently selected from disaccharide groups; R1 to R5 are each independently selected from -CH(CH3)-Y-COOH, Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms; the aldehyde crosslinking agent is selected from CHO-X1-CHO or CHO-X2-CHO, wherein X1 to X2 are selected from -(CH2) n - or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, wherein n represents the number of CH2 groups and n is selected from any integer in the range of 0 to 12.

[0019] Optionally, in step (1), the acid-type sophorolipid is selected from one or more of the structures shown below:

[0020]

[0021]

[0022] The lactone-type sophorolipid is selected from one or more of the structures shown below:

[0023]

[0024] Based on the total weight of the sophorolipid aqueous solution, the content of sophorolipid in the sophorolipid aqueous solution is 5 to 30 weight %; the water used to prepare the sophorolipid aqueous solution is selected from one or more of deionized water, distilled water and ultrapure water;

[0025] The acid is selected from one or more of hydrochloric acid, sulfuric acid and phosphoric acid; the temperature of the first stirring is 10-40° C., and the time is 20-120 min.

[0026] Optionally, in step (2), the molar ratio of the aldehyde cross-linking agent to the sophorolipid in the first solution is 1: (2 to 4), preferably 1: (2 to 3); the aldehyde cross-linking agent is selected from alkyl dialdehyde or thienyl dialdehyde; the alkyl dialdehyde is selected from glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde or heptanedialdehyde, preferably glyoxal, succindialdehyde or glutaraldehyde; the thienyl dialdehyde is selected from thiophene-2,3-dicarboxaldehyde, thiophene-2,4-dicarboxaldehyde or thiophene-2,5-dicarboxaldehyde, preferably thiophene-2,3-dicarboxaldehyde; the base is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; the temperature of the second stirring is 10 to 40°C, and the time is 3 to 6 hours.

[0027] The third aspect of the present disclosure provides an oligomeric bio-based surfactant prepared by the method described in the second aspect of the present disclosure.

[0028] Optionally, the oligomeric bio-based surfactant has a foaming height of less than 10 mL; a foam stabilization time of less than 60 s; and a contact angle of less than 20°.

[0029] The fourth aspect of the present disclosure provides an application of the oligomeric bio-based surfactant described in the first and third aspects of the present disclosure in oilfield oil-containing solid cleaning, oil pollution cleaning, pesticide formulation and daily chemicals.

[0030] Optionally, the use of the oligomeric bio-based surfactant in the cleaning of oil-containing solids in oil fields includes: mixing an aqueous solution containing the oligomeric bio-based surfactant with the oil-containing solids, the mixing temperature being 50 to 80°C and the time being 2 to 8 hours; wherein the concentration of the oligomeric bio-based surfactant in the aqueous solution is 3000 to 30000 mg / L, and the weight ratio of the oil-containing solids to the aqueous solution is 1:(3 to 10), preferably 1:(5 to 10).

[0031] Through the above technical scheme, the present disclosure provides an oligomeric bio-based surfactant and a preparation method and application thereof, wherein the oligomeric bio-based surfactant is a modified sophorolipid dimer or trimer formed by connecting the hydroxyl group of a sophorolipid with the aldehyde group of an aldehyde cross-linking agent through a chemical bond. Compared with unmodified sophorolipids, the oligomeric bio-based surfactant disclosed in the present disclosure has a lower contact angle and higher wettability, and has a branched spatial structure and intramolecular sugar ring steric hindrance, which can reduce the generation of foam and promote the fusion between foams. The preparation method disclosed in the present disclosure has mild conditions, is simple and easy to operate, does not produce three wastes, and can produce an oligomeric bio-based surfactant with a lower critical micelle concentration and better surface activity. When the oligomeric bio-based surfactant is used to clean soil contaminated with heavy oil, the contact angle is less than 18°, and the heavy oil-covered surface can be turned over to a strongly water-wet surface, with excellent oil phase stripping ability, and almost no foaming, reducing the difficulty of subsequent elution. Compared with unmodified sophorolipids, the cleaning efficiency of the oligomeric bio-based surfactant disclosed in the present invention on heavy oil-contaminated soil is as high as over 85%, and the critical micelle concentration is reduced by 1 to 2 orders of magnitude, is more resistant to dilution, and requires a lower dosage.

[0032] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0034] Figure 1 It is the mass spectrometry spectrum of the oligomeric bio-based surfactant prepared in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0035] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0036] The first aspect of the present disclosure provides an oligomeric bio-based surfactant, wherein the oligomeric bio-based surfactant has a structure as shown in Formula 1 or Formula 2:

[0037]

[0038] X1~X2 is selected from -(CH2) n-or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, n represents the number of CH2, and n is selected from any integer from 0 to 12; Z1 to Z5 are each independently selected from a disaccharide group, R1 to R5 are each independently selected from -CH(CH3)-Y-COOH, wherein Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms.

[0039] The oligomeric bio-based surfactant provided by the present invention is to connect the hydroxyl group of the sophorolipid with the aldehyde group of the aldehyde cross-linking agent through a chemical bond to form a modified sophorolipid dimer or trimer. Compared with unmodified sophorolipids, the oligomeric bio-based surfactants disclosed in the present invention have a lower contact angle and higher wettability, and have a branched spatial structure and intramolecular sugar ring steric hindrance, which can reduce the generation of foam and promote the fusion between foams. Sophorolipids are usually composed of hydrophilic sophorose (2 glucose molecules are bound by β-1,2 glycosidic bonds) and hydrophobic saturated or unsaturated long-chain ω- (or ω-1) hydroxy fatty acids.

[0040] Depending on the different fatty acid chains to which the sophorolipid is connected, the types of R1 to R5 are not limited. In one embodiment, Y in R1 to R5 is selected from -(CH2)9-, -(CH2)6CH=CH(CH2)7- or -(CH2)3CH=CHCH2CH=CH(CH2)7-.

[0041] In one embodiment of the present disclosure, Z1 to Z4 are each independently selected from the following groups: in Indicates the chemical bond connecting Z1~Z4 and R1~R4; -* indicates that Z1~Z4 and or In the above embodiment, " The meaning of "chemical bond connecting Z1 to Z4 and R1 to R4" includes represents the chemical bond connecting Z1 and R1, represents the chemical bond connecting Z2 and R2, represents the chemical bond connecting Z3 and R3, Represents the chemical bond connecting Z4 and R4.

[0042] “—* indicates that Z1~Z4 and or The meaning of "chemical bond connecting" includes - * indicates that Z1 and The chemical bond connecting Z2 and The chemical bond connecting Z3 and The chemical bond connecting Z4 and Chemical bonds connected.

[0043] In one embodiment of the present disclosure, Z5 is selected from in Indicates the chemical bond connecting Z5 and R5; -* indicates that Z5 and Chemical bonds connected.

[0044] In one embodiment of the present disclosure, the oligomeric bio-based surfactant has a structure as shown in the following formulas (I) to (VI):

[0045] In the above embodiment, the oligomeric bio-based surfactant has a branched spatial structure and intramolecular sugar ring steric hindrance, which can reduce the generation of foam and promote the fusion between foams.

[0046] In one embodiment of the present disclosure, X1 to X2 are selected from -(CH2) n -, n is selected from any integer in the range of 0 to 10, for example, n can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. Wherein, when n is 0, X1 or X2 is an empty structure, and the carbon atoms on the two -CHOH- are directly connected; preferably, n is selected from any integer in the range of 0 to 3, for example, n can be 0, 1, 2 or 3.

[0047] In another embodiment of the present disclosure, when X1-X2 is selected from substituted or unsubstituted thienylene groups having 4 to 10 carbon atoms, the thienylene group is selected from substituted or unsubstituted groups W, wherein the unsubstituted group W is selected from the group consisting of the following groups: in represents a chemical bond; the substituted group W has one or more substituents, each of which is independently selected from deuterium, fluorine, cyano, methyl, ethyl, n-propyl, isopropyl or tert-butyl; preferably, X1 to X2 are selected from

[0048] In one embodiment of the present disclosure, the foaming height of the oligomeric bio-based surfactant is lower than 10 mL, for example, the foaming height can be 10 mL, 9 mL, 8 mL, 7 mL, 6 mL, 5 mL, 4 mL, 3 mL, 2 mL, 1 mL, or any value between the two; the foam stabilization time is lower than 60 s, for example, the foam stabilization time can be 60 s, 50 s, 40 s, 30 s, 20 s, 10 s, or any value between the two; the contact angle is lower than 20°, for example, the contact angle can be 20°, 18°, 15°, 12°, 10°, 8°, 6°, 4°, 2°, or any value between the two. In the above embodiment, the oligomeric bio-based surfactant has a low foaming height, poor foam stabilization ability, and a small contact angle, and a strong wetting reversal ability, which can flip the oily interface into a strong water-wet interface, and can be used as a green and efficient low-foaming oil detergent.

[0049] A second aspect of the present disclosure provides a method for preparing an oligomeric bio-based surfactant, the method comprising:

[0050] (1) preparing a sophorolipid aqueous solution, adjusting the pH of the sophorolipid aqueous solution to 1.0 to 5.0, preferably 2.0 to 4.0, with an acid, and performing a first stirring to obtain a first solution;

[0051] (2) contacting the first solution with an aldehyde cross-linking agent to obtain a second solution; adjusting the pH of the second solution to 7.0 to 8.5, preferably 7.0 to 7.5, with a base, and performing a second stirring;

[0052] The sophorolipids include acid-type sophorolipids and / or lactone-type sophorolipids, and the acid-type sophorolipids have a structure as shown in Formula 3 below: The lactone-type sophorolipid has a structure as shown in Formula 4: Wherein RZ- is selected from R1-Z1-, R2-Z2-, R3-Z3-, R4-Z4- or R5-Z5-, Z' and Z1 to Z5 are each independently selected from disaccharide groups; R1 to R5 are each independently selected from -CH(CH3)-Y-COOH, Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms; the aldehyde crosslinking agent is selected from CHO-X1-CHO or CHO-X2-CHO, wherein X1 to X2 are selected from -(CH2) n - or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, wherein n represents the number of CH2 groups and n is selected from any integer in the range of 0 to 12.

[0053] The preparation method disclosed in the present invention has mild conditions, is simple and easy to operate, does not generate three wastes, and can produce oligomeric bio-based surfactants with lower critical micelle concentration and better surface activity.

[0054] In one embodiment of the present disclosure, in step (1), the acid-type sophorolipid is selected from one or more of the structures shown below:

[0055]

[0056] In another embodiment, the lactone-type sophorolipid in step (1) is selected from one or more of the following structures:

[0057]

[0058] In one embodiment, based on the total weight of the sophorolipid aqueous solution, the content of sophorolipid in the sophorolipid aqueous solution is 5 to 30% by weight; the water used to prepare the sophorolipid aqueous solution is selected from one or more of deionized water, distilled water and ultrapure water; the acid is selected from one or more of hydrochloric acid, sulfuric acid and phosphoric acid; the first stirring temperature is 10 to 40°C, and the time is 20 to 120 minutes. In the above embodiment, the preferred sophorolipid is selected to produce an oligomeric bio-based surfactant with better wetting, emulsification and solubilization properties. The sophorolipid can be a commercially available chemical reagent or prepared according to a method known in the art.

[0059] In one embodiment of the present disclosure, in step (2), the molar ratio of the aldehyde cross-linking agent to the sophorolipid in the first solution is 1: (2-4), preferably 1: (2-3); the aldehyde cross-linking agent is selected from alkyl dialdehyde or thienyl dialdehyde; the alkyl dialdehyde is selected from glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde or heptanedialdehyde, preferably glyoxal, succindialdehyde or glutaraldehyde; the thienyl dialdehyde is selected from thiophene-2,3-dicarboxaldehyde (CAS No. 932-41-2), thiophene-2,4-dicarboxaldehyde (CAS No. 932-93-4) or thiophene-2,5-dicarboxaldehyde (CAS No. 932-95-6), preferably thiophene-2,3-dicarboxaldehyde; the base is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; the temperature of the second stirring is 10-40° C., and the time is 3-6 hours. In the above embodiment, the aldehyde-based cross-linking agent may be a pure product, or an aqueous solution with any mass fraction, for example, an aqueous solution with a mass fraction of 25% or a aqueous solution with a mass fraction of 50%.

[0060] The third aspect of the present disclosure provides an oligomeric bio-based surfactant prepared by the method described in the second aspect of the present disclosure.

[0061] The oligomeric bio-based surfactant prepared by the method disclosed in the present invention has the characteristics of low foaming height, poor foam stabilization ability and small contact angle, and can be used as a green and efficient low-foaming oil cleaning agent. Specifically, the foaming height of the oligomeric bio-based surfactant is less than 10 mL; the foam stabilization time is less than 60 s; and the contact angle is less than 20°.

[0062] The fourth aspect of the present disclosure provides an application of the oligomeric bio-based surfactant described in the first aspect and the third aspect of the present disclosure in cleaning oil-containing solids in oil fields, cleaning oil pollution, pesticide formulation and daily chemicals. Specifically, the application of the oligomeric bio-based surfactant in cleaning oil-containing solids in oil fields includes using the oligomeric bio-based surfactant as a cleaning agent, oil washing agent or leaching agent for oil-containing solids in oil fields to clean soil contaminated by heavy oil.

[0063] In one embodiment, the use of the oligomeric bio-based surfactant in cleaning oil-containing solids in oil fields includes: mixing an aqueous solution containing the oligomeric bio-based surfactant with oil-containing solids, the mixing temperature is 50-80°C, and the time is 2-8 hours; wherein the concentration of the oligomeric bio-based surfactant in the aqueous solution is 3000-30000 mg / L, and the weight ratio of the oil-containing solids to the aqueous solution is 1:(3-10), preferably 1:(5-10). The oil-containing solids include oil-containing soil, oil-containing sludge, oily stainless steel or oily ceramics.

[0064] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto. Unless otherwise specified, the raw materials used in the examples and comparative examples of the present disclosure are purchased through commercial channels and are pure reagents.

[0065] The mass spectrometer used in the examples and comparative examples is Bruker ultrafleXtreme. The mass spectrometer detection conditions are: the ionization source is MALDI-TOF positive ion mode; the sheath gas flow rate is 45 arb, the auxiliary gas flow rate is 10 arb, the capillary voltage is 3300 V, and the capillary temperature is 350°C.

[0066] Example 1

[0067] (1) Weigh 12.4 g (10 mmols) of lactone-type sophorolipid (purchased from Shandong Qilu Biotechnology Co., Ltd., with a mass content of 50% and a structural formula of ) in a round-bottom flask, add 50 g of distilled water, and stir evenly with a magnetic stirrer at room temperature (25±2°C) to obtain a sophorolipid aqueous solution, wherein the sophorolipid content is 20% by weight; then slowly add hydrochloric acid while performing a first stirring, adjust the pH value of the system to 3.0, and continue to stir magnetically at room temperature (25±2°C) for 30 minutes to obtain a first solution;

[0068] (2) Slowly add 0.8 g of 50 wt% glutaraldehyde aqueous solution (aldehyde crosslinker, 4 mmols, purchased from Inokai) to the first solution, wherein the molar ratio of glutaraldehyde to the sophorolipid in the first solution is 1:2.5; continue stirring the reaction at room temperature (25±2°C) for 4 hours, stop the reaction, and obtain a second solution. Slowly add 10 wt% sodium hydroxide aqueous solution to the second solution, while performing a second stirring, and adjust the pH value of the system to 7.0, to obtain an oligomeric bio-based surfactant, denoted as OSL-C1, OSL-C1 includes a mixture having structures shown in formulas (I) to (VI):

[0069] , X1~X2 are -(CH2)3-, R1~R5 are -CH(CH3)-Y-COOH, Y is -(CH2)6CH=CH(CH2)7-, and its mass fraction is 10.4%.

[0070] The oligomeric bio-based surfactant was subjected to mass spectrometry analysis, and the MALDI-TOF mass spectrum was as follows: Figure 1 As shown in the figure, the mass spectrum peak with a mass-to-charge ratio of 1367.745 corresponds to the molecular ion peak after the dimerized sophorolipid is added with one sodium ion ([M+Na] + ). The mass spectrometry results showed that when the molar ratio of aldehyde to sophorolipid was 1:2.5, the active substance obtained was mainly dimeric sophorolipid, while the content of trimeric sophorolipid was relatively small and the molecular weight was large and difficult to peak, so the peak intensity corresponding to trimeric sophorolipid in the mass spectrum was very low.

[0071] Example 2

[0072] The method of Example 1 is adopted, except that in step (1), 12.4 g (10 mmols) of sophorolipid is added to 20 g of distilled water, and the sophorolipid content in the obtained sophorolipid aqueous solution is 38% by weight; in step (2), 0.72 g of 40 wt% succinaldehyde aqueous solution (3.33 mmols) is slowly added to the first solution, wherein the molar ratio of succinaldehyde to the sophorolipid in the first solution is 1:3, and the reaction is stirred at room temperature for 5 hours. Finally, an oligomeric bio-based surfactant is obtained, which is denoted as OSL-C2. OSL-C2 includes a mixture having a structure shown in formula (I) to (VI), wherein X1 to X2 are -(CH2)2-, R1 to R5 are -CH(CH3)-Y-COOH, and Y is -(CH2)6CH=CH(CH2)7-, and its mass fraction is 19.6%.

[0073] Example 3

[0074] The method of Example 1 is adopted, except that in step (1), 12.4 g (10 mmols) of sophorolipid is added to 10 g of distilled water, and the sophorolipid content in the obtained sophorolipid aqueous solution is 55% by weight; in step (2), 0.29 g of 40 wt% glyoxal aqueous solution (5 mmols) is slowly added to the first solution, wherein the molar ratio of glyoxal to the sophorolipid in the first solution is 1:2. Finally, an oligomeric bio-based surfactant is obtained, which is denoted as OSL-C3. OSL-C3 includes a mixture having a structure shown in formula (I) to (VI), wherein X1 to X2 are -(CH2)0-, R1 to R5 are -CH(CH3)-Y-COOH, and Y is -(CH2)6CH=CH(CH2)7-, and its mass fraction is 27.8%.

[0075] Example 4

[0076] The method of Example 1 was adopted, except that, in step (2), 0.56 g of thiophene-2,3-dicarboxaldehyde (4 mmols) was slowly added to the first solution, wherein the molar ratio of thiophene-2,3-dicarboxaldehyde to the sophorolipid in the first solution was 1:2.5. Finally, an oligomeric bio-based surfactant was obtained, denoted as OSL-C4, OSL-C4 comprising a mixture having structures shown in formulas (I) to (VI), wherein X1 to X2 are R1~R5 are -CH(CH3)-Y-COOH, Y is -(CH2)6CH=CH(CH2)7-, and its mass fraction is 10.8%.

[0077] Comparative Example 1

[0078] 68.88 g (100 mmol) of lactone-type sophorolipid (purchased from Shandong Qilu Biotechnology Group Co., Ltd.) was dissolved in 500 mL of N,N-dimethylformamide and stirred continuously at 50°C until completely dissolved. Then, 0.2 mol of sulfur trioxide pyridine complex was added and reacted at 80°C for 4 h. After the reaction was completed, the solvent was removed by a rotary evaporator to obtain a sulfonated modified sophorolipid with the structural formula: The yield was 99%.

[0079] Test Example 1

[0080] The foaming ability and foam stability of the oligomeric bio-based surfactants prepared in Examples 1 to 4, the sulfonated modified sophorolipids prepared in Comparative Example 1, and the unmodified sophorolipids were evaluated:

[0081] The foaming ability and foam stability are evaluated by Roche foam meter according to the method of GB / T 7462-94. The test temperature is controlled at 25±1℃, the water used in the test is deionized water, and the concentration of the aqueous solution of the test sample is 1000mg / L. Record the change of foam height over time, record every 10s, until the foam height is less than half of the initial height. The initial foam height is recorded as h, and the time taken for the foam height to drop to half of the initial height is recorded as t 1 / 2 The higher the h value, the stronger the foaming ability. 1 / 2 The larger the value, the higher the foam stability. The measurement results are shown in Table 1:

[0082] Table 1

[0083] Surfactants h / mL <![CDATA[t 1 / 2 / s]]> OSL-C1 2 - OSL-C2 3 - OSL-C3 2 - OSL-C4 2 - Sulfonated modified sophorolipids 8 40 Unmodified sophorolipids 10 60

[0084] It can be seen from the data in Table 1 that compared with unmodified sophorolipids and sulfonated modified sophorolipids, the oligomeric bio-based surfactant modified by the method disclosed herein has a reduced foaming ability, the initial foam height is not higher than 3 mL, and the foam completely collapses within 10 seconds. This is because the branched structure of the molecule after the reaction is not conducive to the generation of foam, and can promote the fusion between foams, so that the oligomeric bio-based surfactant exhibits almost no foaming characteristics.

[0085] Test Example 2

[0086] The wetting ability of the oligomeric bio-based surfactants prepared in Examples 1 to 4, the sulfonated modified sophorolipids prepared in Comparative Example 1, and the unmodified sophorolipids was evaluated:

[0087] First, Shengli Y8X heavy oil was evenly coated on the surface of a clean glass slide at high temperature and allowed to cool naturally. Then, the contact angle of the aqueous solution of the sample to be tested was measured by the sessile drop method using the KRUSSDSA100 contact angle meter. The concentrations of the aqueous solution of the sample to be tested were 10 mg / L, 100 mg / L, and 1000 mg / L, respectively. The contact angle experiment temperature was controlled at 25°C. The timing started when the droplet reached the oily interface. After 1 minute of equilibrium, the contact angle was obtained by taking a photo and fitting. The measurement results are shown in Table 2:

[0088] Table 2

[0089]

[0090] The data results in Table 2 show that when the concentration is 1000 mg / L, the contact angle of the unmodified sophorolipid aqueous solution droplet on the heavy oil coated surface is higher than 50°. When the concentration drops to 100 mg / L, the contact angle rises to 58.8°, and when the concentration drops to 10 mg / L, the contact angle rises to 102.3°, and there is no longer a wetting flip effect. The contact angles of the sulfonated modified sophorolipids at the same concentration are 2 to 11° lower than the contact angles of the unmodified sophorolipids. In contrast, the contact angles of the oligomeric bio-based surfactants disclosed in the present invention within the above concentration range are all lower than 18°, which is more than 20° lower than before modification or sulfonated modified sophorolipids, thereby being able to flip the heavy oil covered surface into a strongly water-wet surface, and its wetting flip effect is greatly improved compared to unmodified sophorolipids and sulfonated modified sophorolipids, and the dosage is lower.

[0091] Test Example 3

[0092] The oil washing ability of the oligomeric bio-based surfactants prepared in Examples 1 to 4, the sulfonated modified sophorolipids prepared in Comparative Example 1, and the unmodified sophorolipids was evaluated:

[0093] Uncontaminated soil (from the Y8X block of Shengli Oilfield) was crushed and dried in a 150°C thermostat for 6 hours, and the dried soil was sieved with a 100-mesh sorting sieve. The sieved soil and crude oil were placed in an 80°C thermostat for 8 hours. 85g of dried soil was taken, 15g of heavy oil from the Y8X block of Shengli Oilfield (density of 0.903g / mL) was added, and mixed evenly at 80°C. The soil mixed with crude oil was placed in a 50°C thermostat for aging for one week to prepare an oil-containing soil sample with an oil content of 15%. The oligomeric bio-based surfactants and unmodified sophora biosurfactants prepared in Examples 1 to 4 were formulated into a 1000mg / L oil washing system with tap water.

[0094] Weigh 10g of an oily soil sample with an oil content of 15%, add 60mL of the oil washing system into a conical flask, seal it, and place it in a Jinyi SHZ-88 water bath constant temperature oscillator to heat it to 50°C, and shake it at a constant rate of 30rpm for 3 hours. After cooling to room temperature, let it stand and settle to separate, separate the solution and the washed crude oil from the solid phase, dry the separated solid at 100°C to constant weight, and weigh its weight m. Finally, the cleaning efficiency of the oil washing system is calculated by the following formula:

[0095] Cleaning efficiency = (10g-m) / (1.5g)×100%; the calculation results are shown in Table 3:

[0096] Table 3

[0097] Surfactants Cleaning efficiency / (%) OSL-C1 86.8 OSL-C2 85.2 OSL-C3 85.5 OSL-C4 86.7 Sulfonated modified sophorolipids 73.2 Unmodified sophorolipids 70.1

[0098] The results in Table 3 show that the oligomeric bio-based surfactant disclosed in the present invention can have a good cleaning effect on the crude oil-contaminated soil in the Shengli Y8X block, and its cleaning efficiency can reach more than 85%, which is more than 15% higher than the cleaning efficiency of unmodified sophorolipids and more than 12% higher than the sulfonated modified sophorolipids.

[0099] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0100] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0101] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. An oligomeric bio-based surfactant, characterized in that The oligomeric bio-based surfactant has a structure as shown in Formula 1 or Formula 2: X1~X2 is selected from -(CH2) n - or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, wherein n represents the number of CH2 groups, and n is selected from any integer in the range of 0 to 12; Z1-Z5 are each independently selected from disaccharide groups, and R1-R5 are each independently selected from -CH(CH3)-Y-COOH, wherein Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms.

2. The oligomeric bio-based surfactant according to claim 1, characterized in that Z1 to Z4 are each independently selected from the following groups: in Indicates the chemical bond connecting Z1~Z4 and R1~R4; -* indicates that Z1~Z4 and or Chemical bonds connected.

3. The oligomeric bio-based surfactant according to claim 1, characterized in that Z5 is selected from in represents the chemical bond connecting Z5 and R5; —* indicates Z5 and Chemical bonds connected.

4. The oligomeric bio-based surfactant according to claim 1, characterized in that The oligomeric bio-based surfactant has a structure as shown in the following formulas (I) to (VI):

5. The oligomeric bio-based surfactant according to claim 1, characterized in that X1~X2 is selected from -(CH2) n -, n is selected from any integer in the range of 0 to 10, preferably, n is selected from any integer in the range of 0 to 3; When X1 to X2 are selected from substituted or unsubstituted thienylene groups having 4 to 10 carbon atoms, the thienylene group is selected from substituted or unsubstituted groups W, wherein the unsubstituted group W is selected from the group consisting of the following groups: in represents a chemical bond; the substituted group W has one or more substituents, each of which is independently selected from deuterium, fluorine, cyano, methyl, ethyl, n-propyl, isopropyl or tert-butyl; preferably, X1 to X2 are selected from The Y is selected from -(CH2)9-, -(CH2)6CH=CH(CH2)7- or -(CH2)3CH=CHCH2CH=CH(CH2)7-.

6. The oligomeric bio-based surfactant according to claim 1, characterized in that The foaming height of the oligomeric bio-based surfactant is less than 10 mL; the foam stabilization time is less than 60 s; and the contact angle is less than 20°.

7. A method for preparing an oligomeric bio-based surfactant, characterized in that: The method comprises: (1) preparing a sophorolipid aqueous solution, adjusting the pH of the sophorolipid aqueous solution to 1.0 to 5.0 with an acid, and performing a first stirring to obtain a first solution; (2) contacting the first solution with an aldehyde cross-linking agent to obtain a second solution; adjusting the pH of the second solution to 7.0 to 8.5 with a base, and performing a second stirring; The sophorolipids include acid-type sophorolipids and / or lactone-type sophorolipids, and the acid-type sophorolipids have a structure as shown in Formula 3 below: The lactone-type sophorolipid has a structure as shown in Formula 4: wherein RZ- is selected from R1-Z1-, R2-Z2-, R3-Z3-, R4-Z4- or R5-Z5-, Z' and Z1 to Z5 are each independently selected from disaccharide groups; R1 to R5 are each independently selected from -CH(CH3)-Y-COOH, and Y is selected from a saturated or unsaturated straight-chain alkyl group having 9 to 19 carbon atoms; The aldehyde crosslinking agent is selected from CHO-X1-CHO or CHO-X2-CHO, wherein X1 to X2 are selected from -(CH2) n - or a substituted or unsubstituted thienylene group having 4 to 10 carbon atoms, wherein n represents the number of CH2 groups and n is selected from any integer in the range of 0 to 12.

8. The method according to claim 7, characterized in that In step (1), the acid-type sophorolipid is selected from one or more of the structures shown below: The lactone-type sophorolipid is selected from one or more of the structures shown below: Based on the total weight of the sophorolipid aqueous solution, the content of sophorolipid in the sophorolipid aqueous solution is 5 to 30 weight %; the water used to prepare the sophorolipid aqueous solution is selected from one or more of deionized water, distilled water and ultrapure water; The acid is selected from one or more of hydrochloric acid, sulfuric acid and phosphoric acid; the temperature of the first stirring is 10-40° C., and the time is 20-120 min.

9. The method according to claim 7, characterized in that: In step (2), the molar ratio of the aldehyde cross-linking agent to the sophorolipid in the first solution is 1:(2-4), preferably 1:(2-3); the aldehyde cross-linking agent is selected from alkyl dialdehyde or thienyl dialdehyde; The alkyl dialdehyde is selected from glyoxal, malondialdehyde, succindialdehyde, glutaraldehyde, adipaldehyde or heptanedialdehyde, preferably glyoxal, succindialdehyde or glutaraldehyde; the thienyl dialdehyde is selected from thiophene-2,3-dicarboxaldehyde, thiophene-2,4-dicarboxaldehyde or thiophene-2,5-dicarboxaldehyde, preferably thiophene-2,3-dicarboxaldehyde; The alkali is selected from one or more of sodium hydroxide, potassium hydroxide, ammonia water, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate; the second stirring temperature is 10-40° C., and the time is 3-6 hours.

10. An oligomeric bio-based surfactant prepared by the method according to any one of claims 7 to 9.

11. The oligomeric bio-based surfactant according to claim 10, characterized in that The foaming height of the oligomeric bio-based surfactant is less than 10 mL; the foam stabilization time is less than 60 s; and the contact angle is less than 20°.

12. Use of the oligomeric bio-based surfactant according to any one of claims 1 to 6 and claim 11 in cleaning of oil-containing solids in oil fields, cleaning of oil pollution, formulation of pesticides and daily chemicals.

13. The use according to claim 12, characterized in that: The application of the oligomeric bio-based surfactant in cleaning oil-containing solids in oil fields comprises: mixing an aqueous solution containing the oligomeric bio-based surfactant with oil-containing solids, wherein the mixing temperature is 50 to 80° C. and the mixing time is 2 to 8 hours; The concentration of the oligomeric bio-based surfactant in the aqueous solution is 3000-30000 mg / L, and the weight ratio of the oil-containing solid to the aqueous solution is 1:(3-10), preferably 1:(5-10).

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