Liquid-liquid condensed phase systems, methods of making and using same, and methods of cleaning oil sands

Abstract

This invention relates to the field of oil sludge cleaning technology, and discloses a liquid-liquid condensed phase system, its preparation method and application, and an oil-containing sand cleaning method. The liquid-liquid condensed phase system comprises anionic cyclodextrin derivatives, gemini quaternary ammonium salt surfactants, and water; wherein the charge ratio of the anionic cyclodextrin derivatives to the gemini quaternary ammonium salt surfactants is (0.5-10):1. The condensed phase droplets in the resulting liquid-liquid phase separation system can be stably dispersed in water for more than 24 hours, and can rapidly spread and penetrate on the oil phase surface, exerting a synergistic cleaning effect of surfactants and cyclodextrin derivatives, effectively improving oil washing efficiency.

Description

Technical Field

[0001] This invention relates to the field of oil sludge cleaning technology, specifically to a liquid-liquid condensed phase system, its preparation method and application, and an oil-containing sand cleaning method. Background Technology

[0002] In recent years, the large amounts of oil sludge generated during crude oil extraction, pipeline transportation, and refining, as well as the oil-contaminated soil from decommissioned oilfield well sites and relocated refining facilities, have become significant environmental concerns in the petroleum and petrochemical industry. Polar substances such as gums and asphaltenes in crude oil have strong adhesion to siliceous substrates, making it difficult for crude oil to desorb from sandy solid surfaces. Strengthening the driving force of oil-solid separation and improving oil washing efficiency are key technologies for achieving efficient oil sludge cleaning and rapid remediation of oil-contaminated soil.

[0003] Surfactant molecules possess both hydrophilic head groups and lipophilic alkyl chains, thus exhibiting amphiphilic characteristics. Their aqueous solutions can reduce the interfacial tension between oil and water, thereby stripping oil from oil sands to the aqueous phase for removal. Cyclodextrin derivatives, on the other hand, are green agents that rely on their hydrophobic cavities to solubilize contaminants, carrying contaminated oil into the aqueous phase. However, aqueous solutions of surfactants or cyclodextrin derivatives typically lack sufficient affinity for crude oil, resulting in slow adsorption rates at the oil-water interface and difficulty in penetrating the oil phase. Therefore, there is a need to develop oil washing systems with better affinity for the oil phase.

[0004] Liquid-liquid phase separation refers to the spontaneous separation of a homogeneous colloidal solution into two immiscible phases (a dilute phase and a condensed phase). The condensed phase, enriched with colloidal substances, is referred to as liquid-liquid phase separation. A unique characteristic of liquid-liquid phase separation is its spontaneous phase separation, which distinguishes it from homogeneous solutions, precipitates, and gels, giving it unique advantages in the separation and enrichment of substances. To date, liquid-liquid phase separation has been widely applied in various industrial fields, including daily chemicals, wastewater treatment, and protein purification. Theoretically, the mass concentration of colloidal substances in the condensed phase of liquid-liquid phase separation can be concentrated to over 20%, which should significantly enhance its affinity for the oil-phase interface, thereby promoting the spreading and penetration of reagents on the oil-phase surface. Simultaneously, its adsorption and enrichment rate at the oil-water interface will also be greatly accelerated.

[0005] However, industrial cleaning processes for oily soil and sludge require that the phase separation rate not be too fast, and that the condensed phase droplets have a certain degree of stability before contacting the oil phase so that they can be dispersed in water. This makes most liquid-liquid phase separation systems unsuitable for this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor oil phase affinity, poor stability, and low oil washing efficiency of existing oil washing agents, and to provide a liquid-liquid condensed phase system, its preparation method and application, and an oil sand cleaning method. This liquid-liquid condensed phase system has a liquid-liquid phase separation structure, good stability, good spreading and penetration of the oil phase, and high oil washing efficiency.

[0007] To achieve the above objectives, the present invention provides a liquid-liquid condensed phase system, wherein the condensed phase system comprises an anionic cyclodextrin derivative, a gemini quaternary ammonium salt surfactant, and water;

[0008] The charge ratio of the anionic cyclodextrin derivative to the double-chain quaternary ammonium salt surfactant is (0.5-10):1.

[0009] A second aspect of the present invention provides a method for preparing the above-described liquid-liquid condensed phase system.

[0010] A third aspect of the present invention provides the application of the above-mentioned liquid-liquid condensed phase system in the industrial cleaning of oily soil and oily sludge.

[0011] The fourth aspect of the present invention provides a method for cleaning oily sand containing oil, comprising: mixing oily sand containing oil and an oil-washing agent under stirring conditions;

[0012] The washing agent includes the liquid-liquid condensed phase system described in the first aspect.

[0013] This invention utilizes biocompatible cyclodextrin derivatives and gemini-type quaternary ammonium salt surfactants to obtain a liquid-liquid phase separation condensed phase system. The resulting condensed phase droplets in the liquid-liquid phase separation system can be stably dispersed in water for more than 24 hours, meeting the residence time requirements of cleaning agents in industrial cleaning processes for oily soil and sludge generated in oil fields and refineries. Upon encountering the oil phase, the condensed phase droplets can rapidly spread and penetrate the oil phase surface, exerting a synergistic cleaning effect of the surfactant and cyclodextrin derivative, effectively improving oil washing efficiency. Through optimized structures of the anionic cyclodextrin derivative and gemini-type quaternary ammonium salt surfactant, the dispersion stability of the liquid-liquid phase separation condensed phase droplets in water can be further improved, enabling its application in industrial oil washing. Attached Figure Description

[0014] Figure 1 These are microscope images of the liquid-liquid condensed phase system prepared in Example 1 of this invention;

[0015] Figure 2 This describes the contact situation of droplets in the liquid-liquid condensed phase system obtained in Example 1 of this invention on the surface of the oil phase. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of this invention provides a liquid-liquid condensed phase system, the liquid-liquid condensed phase system comprising an anionic cyclodextrin derivative, a gemini quaternary ammonium salt surfactant, and water;

[0018] The charge ratio of the anionic cyclodextrin derivative to the double-chain quaternary ammonium salt surfactant is (0.5-10):1.

[0019] In existing technologies, anionic surfactants and cationic surfactants are typically not combined because such combinations readily produce precipitation. The inventors of this invention discovered that combining anionic cyclodextrin derivatives with a specific charge ratio and the aforementioned double-chain quaternary ammonium salt surfactant exhibits good dispersion stability in water. The condensed phase droplets show strong affinity for crude oil, enabling rapid spreading and penetration onto the oil phase surface. This effectively promotes the stripping of crude oil from solid surfaces, resulting in high oil washing efficiency, making it particularly suitable as a high-efficiency oil washing agent.

[0020] According to the present invention, the condensed phase system has a liquid-liquid phase separation structure. The liquid-liquid phase separation structure, as conventionally defined in the art, refers to a condensed phase enriched with colloidal substances, whose internal microstructure is a random sponge-like structure. Microscopic observation reveals clearly visible condensed phase droplets, demonstrating the formation of liquid-liquid phase separation.

[0021] In this invention, the charge ratio of the anionic cyclodextrin derivative and the double-chain quaternary ammonium salt surfactant refers to the ratio of the molar amount of negative charge contained in the anionic cyclodextrin derivative to the molar amount of positive charge contained in the double-chain quaternary ammonium salt surfactant.

[0022] According to some preferred embodiments of the present invention, the charge ratio of the anionic cyclodextrin derivative to the gemini quaternary ammonium surfactant is (0.8-5):1, for example, it can be a typical but not limiting charge ratio or a range between the two, such as 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, 5:1. Preferably, the charge ratio of the anionic cyclodextrin derivative to the gemini quaternary ammonium surfactant is (1.2-4):1. In the preferred embodiment described above, the surface of the liquid-liquid phase separation droplets has a certain negative charge, and the electrostatic repulsion between the droplets slows down the aggregation process between the droplets, which is further beneficial to improving the dispersion stability of the liquid-liquid phase separation droplets in water.

[0023] In this invention, the anionic cyclodextrin derivative refers to a product derived by replacing the H atom on at least one hydroxyl group in a cyclodextrin with an anionic hydrophilic group or an alkylene group with an anionic hydrophilic group at the end. Various anionic cyclodextrin derivatives known in the art can be used in this invention, such as at least one of sulfonate, sulfate, phosphate and carboxylate cyclodextrin derivatives.

[0024] Preferably, the anionic cyclodextrin derivative has the structure shown in formula (1).

[0025]

[0026] Where m is selected from any integer from 1 to 10, and n is selected from any integer from 0 to 10;

[0027] The R1 group contains any one of -SO3M, -COOM, -PO3M2 and -PO3HM, and optionally a C1-C4 alkylene group, wherein M is an alkali metal, for example, any one of Li, Na and K, preferably Na or K.

[0028] According to the present invention, the R1 group can be selected from any one of -SO3M, -COOM, -PO3M2 and -PO3HM, or it can be a C1-C4 alkylene group and a combination of any one of -SO3M, -COOM, -PO3M2 and -PO3HM.

[0029] In this invention, the C1-C4 alkylene groups can be straight-chain or branched alkylene groups, preferably straight-chain alkylene groups, such as methylene, ethylene, propylene, or butylene.

[0030] Preferably, m is selected from any integer from 1 to 8, and n is selected from any integer from 0 to 7.

[0031] According to some preferred embodiments of the present invention, R1 is any one of the groups in the structures shown in formulas (1-1) to (1-5).

[0032]

[0033] Wherein, M is an alkali metal, preferably Na or K.

[0034] Using anionic cyclodextrin derivatives with the above-mentioned preferred structure, whose molecules contain several hydroxyl groups and anionic head groups, is beneficial for regulating the interaction forces between them and cationic quaternary ammonium salt surfactants, such as hydrogen bonding and electrostatic interactions, which is beneficial for further improving the dispersion stability of liquid-liquid phase condensed phase droplets in water.

[0035] In this invention, the term "gemini quaternary ammonium salt surfactant" has the conventional definition in the art and can also be referred to as cationic quaternary ammonium salt gemini surfactant.

[0036] According to some preferred embodiments of the present invention, the gemini quaternary ammonium salt surfactant has the structure shown in formula (2).

[0037]

[0038] Each R2 is independently selected from saturated or unsaturated hydrocarbon groups of C8-22; R3 contains at least one of alkylene, hydroxyl and amide groups; and each R4 is independently selected from methyl or ethyl groups.

[0039] X is a halogen, preferably Cl or Br.

[0040] In this invention, "C8-22 saturated or unsaturated hydrocarbon groups" refers to saturated or unsaturated hydrocarbon groups with a total number of carbon atoms of 8-22. Saturated hydrocarbon groups of C8-22 can be, for example, straight-chain or branched alkyl groups with a total number of carbon atoms of 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20, or 22, such as n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, etc. Unsaturated hydrocarbon groups of C8-22 can be, for example, carbon chains or aromatic rings containing unsaturated bonds.

[0041] According to the present invention, in formula (2), R3 is a linking group between two amphiphilic units, and the R3 group contains at least one of alkylene, hydroxyl and amide groups.

[0042] According to some preferred embodiments of the present invention, R3 is a group having the structure shown in any one of formulas (2-1) to (2-4).

[0043]

[0044] In equation (2-1), s is selected from integers from 0 to 10, preferably integers from 0 to 4.

[0045] According to some preferred embodiments of the present invention, the anionic cyclodextrin derivative has the structure shown in formula (1), wherein m is selected from any integer from 1 to 8, n is selected from any integer from 0 to 7, and R1 is any one of the groups with the structures shown in formulas (1-1) to (1-5); the gemini quaternary ammonium salt surfactant has the structure shown in formula (2), wherein R2 is selected from saturated or unsaturated hydrocarbon groups of C8-22, X is Cl or Br, and R3 is a group with the structure shown in any one of formulas (2-1) to (2-4).

[0046] Combining a gemini quaternary ammonium salt surfactant with the above-mentioned preferred structure with anionic cyclodextrin derivatives is beneficial to adjusting the interaction force between the two surfactants and the cationic quaternary ammonium salt surfactant by utilizing the quaternary ammonium salt head groups, anionic head groups, hydroxyl groups, etc. contained in the two surfactants. This is beneficial to further improve the dispersion stability of the liquid-liquid phase condensed phase droplets in water and improve the oil washing efficiency.

[0047] The present invention allows for a wide range of choices regarding the ratio of surfactant to water in the liquid-liquid condensed phase system. The anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant are combined using the above-mentioned charge ratio to form a liquid-liquid phase separation condensed phase system. The condensed phase droplets in the resulting liquid-liquid phase separation system can be stably dispersed in water.

[0048] According to some preferred embodiments of the present invention, based on the total amount of the condensed phase system, the molar concentration of the anionic cyclodextrin derivative is not less than 0.05 mmol / L, preferably 0.1-2 mmol / L. For example, it can be typical but not limiting proportions such as 0.1 mmol / L, 0.2 mmol / L, 0.3 mmol / L, 0.4 mmol / L, 0.5 mmol / L, 0.6 mmol / L, 0.7 mmol / L, 0.8 mmol / L, 0.9 mmol / L, 1 mmol / L, 1.1 mmol / L, 1.2 mmol / L, 1.3 mmol / L, 1.4 mmol / L, 1.5 mmol / L, 1.6 mmol / L, 1.7 mmol / L, 1.8 mmol / L, 1.9 mmol / L, and 2 mmol / L. Within the above preferred ranges, the concentration of colloidal substances and the strength of intermolecular interactions are both beneficial to the stability of liquid-liquid phase separation.

[0049] Preferably, based on the total amount of the condensed phase system, the total molar concentration of the anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant is not less than 0.1 mmol / L, preferably 0.3-10 mmol / L. For example, it can be typical but not limiting concentration values ​​or a range between the two, such as 0.3 mmol / L, 0.4 mmol / L, 0.5 mmol / L, 0.6 mmol / L, 0.7 mmol / L, 0.8 mmol / L, 0.9 mmol / L, 1 mmol / L, 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L.

[0050] A second aspect of the present invention provides a method for preparing the above-mentioned condensed phase system, comprising: preparing an aqueous solution A of an anionic cyclodextrin derivative and an aqueous solution A of a gemini quaternary ammonium salt surfactant, and then mixing the aqueous solution A and the aqueous solution B.

[0051] According to the present invention, a liquid-liquid condensed phase system with liquid-liquid phase separation can be obtained by simply mixing anionic cyclodextrin derivatives and gemini quaternary ammonium salt surfactants. The preparation method is simple and efficient.

[0052] According to the present invention, the specific selection of the anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant is the same as that defined in the first aspect, and will not be repeated here. The amounts of aqueous solution A and aqueous solution B are such that the charge ratio of the anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant is (0.5-10):1.

[0053] The present invention does not impose any particular limitation on the concentrations of the above-mentioned aqueous solutions A and B. In a preferred embodiment, it is sufficient to ensure that the concentration of the mixed solution meets the above-mentioned preferred range requirements. Those skilled in the art can make selections based on the actual situation.

[0054] The present invention does not have any particular requirements for the mixing order of the aqueous solution A and the aqueous solution B. Preferably, the mixing is carried out under stirring conditions, and the stirring speed is 20-1000 rpm, preferably 100-300 rpm.

[0055] The present invention does not have special requirements for the temperature and pressure of the mixing, and can be carried out under normal temperature and pressure conditions.

[0056] A third aspect of the present invention provides the application of the above-mentioned condensed phase system in the industrial cleaning of oily soil and sludge.

[0057] Conventional liquid-liquid phase separation systems in the prior art can be divided into polymer systems, polymer-surfactant complex systems, and surfactant-organic small molecule complex systems. However, polymers are easily adsorbed and retained on the surface of sand and soil, causing secondary pollution. At the same time, the industrial cleaning process of oily soil and oily sludge requires that the phase separation rate cannot be too fast. The condensed phase droplets need to have a certain stability before contacting the oil phase so that they can be dispersed in water. This makes most liquid-liquid phase separation systems unsuitable for industrial cleaning of oily soil and oily sludge.

[0058] The liquid-liquid condensed phase system provided by this invention allows the condensed phase droplets to be stably dispersed in water for more than 24 hours, meeting the residence time requirements of cleaning agents in industrial cleaning processes for oily soil and sludge generated in oil fields and refineries. Upon encountering the oil phase, the condensed phase droplets can rapidly spread and penetrate the oil phase surface, exerting a synergistic cleaning effect of anionic cyclodextrin derivatives and gemini quaternary ammonium salt surfactants, effectively improving oil washing efficiency and demonstrating promising application prospects.

[0059] The fourth aspect of the present invention provides a method for cleaning oily sand containing oil, comprising: mixing oily sand containing oil and an oil-washing agent under stirring conditions;

[0060] The washing agent is the condensed phase system described in the first aspect.

[0061] According to some preferred embodiments of the present invention, the liquid-solid mass ratio of the washing agent and the oil-containing oil sand is (1-10):1, for example, it can be a typical but not limiting ratio or a range between the two, such as 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1. Preferably, the liquid-solid mass ratio of the washing agent and the oil-containing oil sand is (2-5):1. In the above preferred cases, it is beneficial for the washing agent and the oil sand to react fully, thereby improving the washing efficiency.

[0062] In this invention, the oil-bearing sands can be oily sludge generated during crude oil extraction, pipeline transportation, and refining, or oil-contaminated soil from decommissioned oilfield well sites and relocated refining sites. The crude oil contaminant content in the oil-bearing sands is not less than 5 wt%, preferably 5-25 wt%. For oil-bearing sands with the above composition, the oil-washing agent provided by this invention has a superior cleaning effect.

[0063] The present invention does not have any particular limitation on the mixing conditions of the oily sand and the washing agent. Conventional operating conditions in the art can be used. Preferably, the mixing temperature is 40-65℃, preferably 50-60℃, the stirring rate is 100-200rpm, preferably 120-150rpm, and the mixing time is 1-12h, preferably 2-4h.

[0064] The present invention will be described in detail below through embodiments.

[0065] Unless otherwise specified, all reagents used in the following examples are commercially available chemical reagents.

[0066] Example 1

[0067] Preparation based on liquid-liquid phase separation of sulfobutyl-β-cyclodextrin and geminal quaternary ammonium salt 12-6-12. The structural formulas of sulfobutyl-β-cyclodextrin (purchased from Accela, 98% purity, catalog number SY003635) and 12-6-12 (prepared according to the method described in Langmuir 1991, 7, 1072-1075) are shown in formulas a1 and b1, respectively:

[0068]

[0069] Where m is 2 and n is 5.

[0070]

[0071] Weigh 0.435 g of sulfobutyl-β-cyclodextrin and prepare 100 mL of aqueous solution (3 mM concentration); weigh 0.067 g of 12-6-12 gemini surfactant and prepare 100 mL of aqueous solution (1 mM concentration). Then, gradually add the 12-6-12 aqueous solution to the sulfobutyl-β-cyclodextrin aqueous solution under stirring. The two prepared aqueous solutions are mixed at room temperature with stirring at 300 rpm to prepare a liquid-liquid condensed phase system. Observe under a microscope at 40x magnification, as shown... Figure 1 As shown, the condensed phase droplets can be clearly seen, proving that liquid-liquid phase separation has occurred.

[0072] In this system, the concentration of sulfobutyl-β-cyclodextrin is 1.5 mM, the concentration of 12-6-12 Gemini surfactant is 0.5 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin to 12-6-12 is 3:1.

[0073] Example 2

[0074] Preparation based on the liquid-liquid phase separation of carboxymethyl-β-cyclodextrin and the geminal quaternary ammonium salt 12-3-12. The structural formulas of carboxymethyl-β-cyclodextrin (purchased from Inokai, 99% purity, catalog number A62744) and 12-3-12 (prepared according to the method described in Langmuir 1991, 7, 1072-1075) are shown in formulas a2 and b2, respectively:

[0075]

[0076] Where m is 7 and n is 0.

[0077]

[0078] Weigh 0.0308 g of carboxymethyl-β-cyclodextrin and prepare 100 mL of aqueous solution (0.2 mM concentration); weigh 0.0366 g of 12-3-12 geminal quaternary ammonium salt surfactant and prepare 100 mL of aqueous solution (0.584 mM concentration). Then, gradually add the carboxymethyl-β-cyclodextrin aqueous solution to the 12-3-12 aqueous solution under stirring. Mix the two prepared aqueous solutions at room temperature with stirring at 100 rpm to prepare the liquid-liquid condensed phase system.

[0079] In this system, the concentration of carboxymethyl-β-cyclodextrin is 0.1 mM, the concentration of 12-3-12 Gemini quaternary ammonium salt surfactant is 0.292 mM, and the mixed charge ratio of carboxymethyl-β-cyclodextrin to 12-6-12 is 1.2:1.

[0080] Example 3

[0081] Preparation based on liquid-liquid phase separation of sulfonyl-β-cyclodextrin and gemini quaternary ammonium salt Malic-2C12. The structural formula of sulfonyl-β-cyclodextrin (purchased from Accela, 98% purity, catalog number SY003635) is shown in formula a1, and the structural formula of gemini quaternary ammonium salt Malic-2C12 (prepared according to Example 1 of invention patent CN111072511B) is shown in formula b3.

[0082]

[0083] Weigh 0.58 g of sulfobutyl-β-cyclodextrin and prepare a 100 mL aqueous solution (4 mM concentration); weigh 0.077 g of Malic-2C12 gemini quaternary ammonium salt surfactant and prepare a 100 mL aqueous solution (1 mM concentration). Then, gradually add the Malic-2C12 aqueous solution to the sulfobutyl-β-cyclodextrin aqueous solution under stirring. Mix the two prepared aqueous solutions at room temperature with stirring at 250 rpm to prepare a liquid-liquid condensed phase system.

[0084] In this system, the concentration of sulfobutyl-β-cyclodextrin is 2 mM, the concentration of Malic-2C12 gemini surfactant is 0.5 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin to Malic-2C12 is 4:1.

[0085] Example 4

[0086] The method is the same as in Example 1, except that 0.435 g of sulfobutyl-β-cyclodextrin is weighed and prepared into 100 mL of aqueous solution (3 mM); 0.201 g of 12-6-12 Gemini surfactant is weighed and prepared into 100 mL of aqueous solution (3 mM). After mixing, a liquid-liquid condensed phase system is obtained.

[0087] In this system, the concentration of sulfobutyl-β-cyclodextrin is 1.5 mM, the concentration of 12-6-12 Gemini surfactant is 1.5 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin and 12-6-12 is 1:1.

[0088] Example 5

[0089] The method is the same as in Example 1, except that the gemini quaternary ammonium salt surfactant 12-6-12 is replaced with 12-3-12, and its linking group is changed from —(CH2)6— to —(CH2)3—. The structure of 12-3-12 is shown in Formula b4:

[0090]

[0091] Accordingly, 0.063 g of 12-3-12 Gemini surfactant was weighed and prepared into 100 mL of aqueous solution (1 mM concentration). After mixing, the liquid-liquid condensed phase system was obtained.

[0092] In this system, the concentration of sulfobutyl-β-cyclodextrin is 1.5 mM, the concentration of 12-3-12 Gemini surfactant is 0.5 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin to 12-3-12 is 3:1.

[0093] Example 6

[0094] The method is the same as in Example 1, except that...

[0095] Weigh 0.0232 g of sulfobutyl-β-cyclodextrin and prepare 100 mL of aqueous solution (0.16 mM concentration); weigh 0.0355 g of 12-6-12 gemini surfactant and prepare 1000 mL of aqueous solution (0.053 mM concentration). Measure 100 mL of the 12-6-12 aqueous solution and mix it with 100 mL of the sulfobutyl-β-cyclodextrin aqueous solution to obtain a liquid-liquid condensed phase system.

[0096] In this system, the concentration of sulfobutyl-β-cyclodextrin is 0.08 mM, the concentration of 12-6-12 Gemini surfactant is 0.027 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin to 12-6-12 is 3:1.

[0097] Comparative Example 1

[0098] Preparation of a complex system of sulfobutyl-β-cyclodextrin and single-chain quaternary ammonium salt dodecyltrimethylammonium bromide (DTAB).

[0099] Weigh 0.435 g of sulfobutyl-β-cyclodextrin and prepare 100 mL of aqueous solution (3 mM concentration); weigh 0.062 g of the single-chain quaternary ammonium salt surfactant DTAB and prepare 100 mL of aqueous solution (2 mM concentration). Then, gradually add the DTAB aqueous solution to the sulfobutyl-β-cyclodextrin aqueous solution under stirring. The two prepared aqueous solutions are mixed at room temperature with stirring at 300 rpm to obtain the composite system.

[0100] In this system, the concentration of sulfobutyl-β-cyclodextrin is 1.5 mM, the concentration of DTAB surfactant is 1 mM, and the mixed charge ratio of sulfobutyl-β-cyclodextrin and DTAB is 3:1.

[0101] The composite system was clear and transparent, and no liquid-liquid phase separation was formed.

[0102] Comparative Example 2

[0103] Weigh 0.218 g of sulfobutyl-β-cyclodextrin and prepare 100 mL of aqueous solution (1.5 mM). The resulting aqueous solution is clear and transparent, and no liquid-liquid phase separation is formed.

[0104] Comparative Example 3

[0105] Weigh 0.034 g of 12-6-12 Gemini surfactant and prepare 100 mL of aqueous solution (0.5 mM concentration). The resulting aqueous solution is clear and transparent, and no liquid-liquid phase separation is formed.

[0106] Test case

[0107] (1) Determination of the wettability of the liquid-liquid phase separation system on oil-containing surfaces:

[0108] The oil phase used was crude oil obtained by separating oily soil (16 wt% crude oil contaminant content) from Shengli HK oilfield and oily sludge (20 wt% crude oil contaminant content) from YS refinery.

[0109] First, the oil phase from the oil-containing sand was uniformly coated onto a clean glass slide surface at high temperature and allowed to cool naturally. Then, the contact angles of the droplets in the liquid-liquid condensed phase systems prepared in the above examples and comparative examples on the glass slide surface were measured using a KRUSSDSA100 contact angle meter via the seated drop method. The contact angle experiment temperature was controlled at 25°C. Timing began when the droplet reached the oily interface, and after equilibration for 3 minutes, the contact angle was obtained by photographing and fitting the image. The measurement results are shown in Table 1. The contact situation of the droplets in the liquid-liquid condensed phase system prepared in Example 1 on the glass slide surface is shown in Table 1. Figure 2 As shown, the liquid-liquid phase separation system exhibits good spreading performance on the oil phase surface and has a small contact angle.

[0110] Table 1

[0111]

[0112] As shown in Table 1, the liquid-liquid phase separation systems prepared in the embodiments of the present invention have lower contact angles (all below 20 degrees) on oily surfaces, proving that the prepared liquid-liquid phase separation systems have the ability to spread and penetrate rapidly on oily surfaces containing oil sands. Preferably, the liquid-liquid phase separation systems prepared in Examples 1-3 all have contact angles below 15 degrees on oily surfaces, indicating better penetration. In contrast, after replacing the gemini quaternary ammonium salt surfactant with a single-chain quaternary ammonium salt surfactant, the contact angle is higher than 40 degrees, and the wetting ability of the system on oily surfaces decreases significantly. Furthermore, when sulfobutyl cyclodextrin or gemini quaternary ammonium salt surfactants are present as a single component, the contact angle of the droplets on oily surfaces is higher than 60 degrees, indicating even weaker wetting ability on oily surfaces.

[0113] (2) Determination of the water dispersion stability of liquid-liquid phase separated droplets:

[0114] Take 100 mL of the liquid-liquid condensed phase system prepared in the above example, transfer it to a transparent stoppered graduated glass test tube, let it stand, and observe and record the time required for the liquid-liquid phase separation system to begin to show a clear phase separation boundary.

[0115] Meanwhile, the Zeta potential of the newly prepared liquid-liquid phase separation system solution at 25°C was tested using a Malven Zetasizer Nano-ZS instrument, and the results are shown in Table 2.

[0116] Table 2

[0117] serial number t / h Zeta potential / mV Example 1 28.0 -6.55 Example 2 26.5 -4.83 Example 3 25.5 -3.75 Example 4 27.0 -2.51 Example 5 24.5 -6.40 Example 6 38.5 -3.33

[0118] Table 2 shows that the liquid-liquid phase separation droplets can be stably dispersed in water for more than 24 hours, fully meeting the requirements of industrial cleaning processes for oily soil and sludge. The good dispersion stability of the liquid-liquid phase separation system is due to the negative charge on the surface of the condensed phase droplets, with all of them having negative Zeta potentials and absolute values ​​higher than 2.50 mV, proving that there is electrostatic repulsion between the droplets.

[0119] (3) Evaluation of oil-washing ability:

[0120] This evaluation experiment used oil-contaminated soil from the Shengli HK oilfield (16 wt% crude oil contaminant content) and oil sludge from the YS refinery (20 wt% crude oil contaminant content) as the oil washing targets. 10 g of oil sludge was placed in a 100 mL Erlenmeyer flask, and the aqueous washing systems prepared in the above examples and comparative examples (addition amounts are shown in Table 3) were added respectively. After sealing, the flasks were placed in a Jinyi SHZ-88 water bath constant temperature shaker and heated to 40°C, maintaining a constant shaking rate of 30 rpm for 4 hours. After cooling to room temperature, the flasks were allowed to settle and separate. The solution and the washed crude oil were separated from the solid phase. The separated solid was dried at 100°C to constant weight, and its weight m was measured.

[0121] The cleaning efficiency of this oil washing system was calculated using the following formula, and the results are shown in Table 3:

[0122] Cleaning efficiency = (mass of uncleaned oily sand – m) / mass of crude oil contaminants in uncleaned oily sand × 100%.

[0123] Table 3 Cleaning efficiency of different washing systems

[0124]

[0125]

[0126] Table 3 shows that the liquid-liquid phase separation oil washing system prepared in the embodiments of the present invention can achieve good cleaning effect on oilfield and refinery sludge, with cleaning efficiencies of 82.4% and 83.2% or higher, respectively, and preferably 85% and 90% or higher, respectively. In contrast, when the gemini quaternary ammonium salt surfactant is replaced with a single-chain quaternary ammonium salt surfactant, the composite system formed by it and the cyclodextrin derivative cannot achieve liquid-liquid phase separation, and the highest oil washing efficiencies for oilfield and refinery sludge are 78.6% and 80.2%, respectively. In addition, the oil washing efficiency when the cyclodextrin derivative or the gemini quaternary ammonium salt surfactant is present alone is less than 62%. This proves that the liquid-liquid phase separation system provided by the present invention can be used as a highly efficient and green oil washing agent, and has good application prospects in the fields of efficient cleaning of oil sludge generated in oilfields and refineries and rapid remediation of oil-contaminated soil.

[0127] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A liquid-liquid condensed phase system, characterized in that, The liquid-liquid condensed phase system includes anionic cyclodextrin derivatives, gemini quaternary ammonium salt surfactants, and water; The charge ratio of the anionic cyclodextrin derivative to the gemini quaternary ammonium salt surfactant is (0.8-5):

1. The anionic cyclodextrin derivative has the structure shown in formula (1). Equation (1), Where m is selected from any integer from 1 to 10, and n is selected from any integer from 0 to 10; The R1 group contains any one of -SO3M, -COOM, -PO3M2 and -PO3HM, and optionally a C1-C5 alkylene group; wherein M is an alkali metal.

2. The liquid-liquid condensed phase system according to claim 1, wherein, The liquid-liquid condensed phase system has a liquid-liquid phase separation structure.

3. The liquid-liquid condensed phase system according to claim 1, wherein, The charge ratio of the anionic cyclodextrin derivative to the gemini quaternary ammonium salt surfactant is (1.2-4):

1.

4. The liquid-liquid condensed phase system according to claim 1, wherein, M is either Na or K.

5. The liquid-liquid condensed phase system according to claim 1, wherein, R1 is any one of the groups in the structures shown in formulas (1-1) to (1-5). Where M represents an alkali metal.

6. The liquid-liquid condensed phase system according to claim 5, wherein, M is either Na or K.

7. The liquid-liquid condensed phase system according to any one of claims 1-6, wherein, The gemini quaternary ammonium salt surfactant has the structure shown in formula (2). Equation (2), Each R2 is independently selected from saturated or unsaturated hydrocarbon groups of C8-22; R3 contains at least one of alkylene, hydroxyl and amide groups; and each R4 is independently selected from methyl or ethyl groups. X is a halogen.

8. The liquid-liquid condensed phase system according to claim 7, wherein, X is either Cl or Br.

9. The liquid-liquid condensed phase system according to claim 7, wherein, R3 is a group having any one of the structures shown in formulas (2-1) to (2-4). In equation (2-1), s is selected from integers from 0 to 10.

10. The liquid-liquid condensed phase system according to claim 9, wherein, s is an integer selected from 0 to 4.

11. The liquid-liquid condensed phase system according to any one of claims 1-6, wherein, Based on the total amount of the liquid-liquid condensed phase system, the molar concentration of the anionic cyclodextrin derivative is not less than 0.05 mmol / L.

12. The liquid-liquid condensed phase system according to claim 11, wherein, Based on the total amount of the liquid-liquid condensed phase system, the molar concentration of the anionic cyclodextrin derivative is 0.1-2 mmol / L.

13. The liquid-liquid condensed phase system according to any one of claims 1-6, wherein, Based on the total amount of the liquid-liquid condensed phase system, the total molar concentration of the anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant is not less than 0.1 mmol / L.

14. The liquid-liquid condensed phase system according to claim 13, wherein, Based on the total amount of the liquid-liquid condensed phase system, the total molar concentration of the anionic cyclodextrin derivative and the gemini quaternary ammonium salt surfactant is 0.3-10 mmol / L.

15. A method for preparing the liquid-liquid condensed phase system according to any one of claims 1-14, comprising: Prepare aqueous solutions A of anionic cyclodextrin derivatives and B of gemini quaternary ammonium salt surfactants, and then mix aqueous solutions A and B.

16. The preparation method according to claim 15, wherein, The mixing is carried out under stirring conditions at a stirring rate of 20-1000 rpm.

17. The preparation method according to claim 16, wherein, The mixing is carried out under stirring conditions at a stirring rate of 100-300 rpm.

18. The application of the liquid-liquid condensed phase system according to any one of claims 1-14 in the industrial cleaning of oily soil and oily sludge.

19. A method for cleaning oil-containing sand, comprising: Under stirring conditions, oily sand and washing agent are mixed; The washing agent includes the liquid-liquid condensed phase system according to any one of claims 1-14.

20. The method according to claim 19, wherein, The liquid-solid mass ratio of the washing agent and the oily sand is (1-10):

1.

21. The method according to claim 19, wherein, The liquid-solid mass ratio of the washing agent and the oily sand is (2-5):

1.

22. The method according to any one of claims 19-21, wherein, The content of crude oil contaminants in the oil sands shall not be less than 5 wt%.

23. The method according to any one of claims 19-21, wherein, The mixing temperature is 40-65℃, the stirring rate is 100-200rpm, and the mixing time is 1-12h.

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