A high-efficiency, non-foaming and environment-friendly surfactant, its preparation method and application

Abstract

This invention discloses a highly efficient, non-foaming, and environmentally friendly surfactant, its preparation method, and its applications. The preparation method involves dissolving maleic anhydride and a monohydric saturated alcohol in N,N-dimethylformamide at a 1:1 molar ratio, heating and stirring to esterify and obtain a carbon-carbon double-bond intermediate; adding an aqueous solution of sodium bisulfite and a co-solvent to the system, heating and sulfonating to add the sulfonate, and then concentrating, filtering, drying, and grinding to obtain a powdered product. The prepared surfactant exhibits excellent thermal stability, with a weight loss of only 0.96 wt% at 178℃, ensuring its molecular structure remains intact during MH formation and guaranteeing long-term stable promoting effects; the interfacial tension and contact angle can be reduced to 16.13 mN / m and 31.5°, respectively, significantly improving the gas-liquid mass transfer efficiency during MH formation; at a concentration of 0.3 wt%, the MH gas storage capacity is 171.03 V / V, the hydrate conversion rate is 85.42%, the induction time is 2.5 min, there is no foaming, and rapid dissociation occurs within 55 min; it has no significant inhibition of Escherichia coli growth and exhibits excellent environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of surfactant technology, and in particular to a highly efficient, non-foaming, and environmentally friendly surfactant, its preparation method, and its application. Background Technology

[0002] Methane hydrate (MH) is an ice-like solid formed under low temperature and high pressure conditions, consisting of water molecules forming a cage-like lattice that encapsulates methane molecules. Compared to traditional liquefied natural gas (LNG) and compressed natural gas (CNG) technologies, MH exhibits significant advantages due to its superior gas density, relatively mild storage conditions, and higher safety. However, limited by low gas-liquid mass transfer efficiency during its formation, MH often faces problems such as long induction time and slow growth rate, which has become a key bottleneck restricting its large-scale industrial application.

[0003] To address the bottleneck of slow MH formation kinetics, the introduction of surfactants is considered a simple and efficient solution. Common surfactants mainly fall into three categories: anionic, cationic, and nonionic. Among them, anionic surfactants, especially sodium dodecyl sulfate (SDS), are recognized as one of the most efficient MH kinetic promoters due to their unique long alkyl chain and sulfonic acid group structure, which can significantly reduce mass transfer resistance. However, SDS causes severe foaming problems during MH decomposition. These foams accumulate on the MH surface, forming new mass transfer barriers, a problem particularly prominent in recycling and large-scale applications. Furthermore, SDS has poor environmental compatibility, and the potential ecological risks further restrict its large-scale promotion.

[0004] Therefore, based on the structural characteristics of SDS and in accordance with the principles of green chemistry, it is of great significance to develop a surfactant that combines high efficiency, low foaming properties and environmental friendliness, effectively solve the bottlenecks of existing technologies, and promote the large-scale application of MH technology. Summary of the Invention

[0005] This invention provides a highly efficient, non-foaming, and environmentally friendly surfactant, its preparation method, and its application, to overcome the aforementioned problems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a highly efficient, non-foaming, and environmentally friendly surfactant includes the following steps: S1: Synthesis of intermediate: Maleic anhydride and monohydric saturated alcohol were dissolved in N,N-dimethylformamide in a 1:1 molar ratio and esterified under heating and stirring conditions to obtain an intermediate containing carbon-carbon double bonds. S2: Sulfonation reaction: Sodium bisulfite aqueous solution and co-solvent are added to the reaction system of the intermediate, and a sulfonation addition reaction is carried out under heating conditions. After the reaction is completed, the solution is concentrated, filtered, dried and ground to obtain the surfactant in powder form.

[0008] Further, in step S1, the molar ratio of the monosaturated alcohol to the N,N-dimethylformamide DMF is 1:10-15; the preferred molar ratio of the monosaturated alcohol to the N,N-dimethylformamide DMF is 1:11.

[0009] Further, in step S2, the mass concentration of the sodium bisulfite aqueous solution is 1%-10%; preferably, the mass concentration of the sodium bisulfite aqueous solution is 5.7%.

[0010] Further, in step S2, the co-solvent is at least one of isopropanol, ethanol, or n-propanol; the co-solvent is preferably isopropanol.

[0011] Further, the heating conditions in step S1 are: heating at 50 ℃-80 ℃ for a reaction time of 6 h-24 h. Preferably, the reaction is carried out at 60 ℃ with magnetic stirring at 300 rpm for 12 h.

[0012] Furthermore, the heating conditions in step S2 are: heating at 100 °C for a reaction time of 6 h-24 h.

[0013] Furthermore, in step S2, the concentration is a rotary evaporation concentration, and the process conditions for rotary evaporation concentration are 80 °C for 3 h.

[0014] Furthermore, in step S2, the drying method is vacuum drying, and the conditions are vacuum drying at 50 ℃ for 12 hours.

[0015] Furthermore, the monohydric saturated alcohol is a straight-chain or branched monohydric alcohol with 8 to 18 carbon atoms; the monohydric saturated alcohol is preferably n-nonyl alcohol.

[0016] In another aspect, the present invention provides a highly efficient, non-foaming, and environmentally friendly surfactant, which is prepared by the aforementioned method.

[0017] In another aspect, the present invention provides the application of the aforementioned high-efficiency, non-foaming, and environmentally friendly surfactant in the fields of hydration, cleaning, emulsification, or wetting.

[0018] The beneficial effects of this invention are: I. The surfactant synthesized by the method for preparing a highly efficient, non-foaming, and environmentally friendly surfactant disclosed in this invention possesses excellent thermal stability and interfacial regulation capabilities. Under conditions as high as 178°C, the surfactant molecule weight loss rate is only 0.96 wt%. This characteristic ensures the integrity of its molecular structure during MH generation, thereby ensuring a long-term stable promoting effect. At the same time, this surfactant exhibits excellent interfacial regulation capabilities, reducing the interfacial tension and contact angle to 16.13 mN / m and 31.5°, respectively, thereby significantly improving the gas-liquid mass transfer efficiency during MH generation. II. The surfactant synthesized in this invention possesses excellent kinetic promoting properties and rapid, foam-free dissociation characteristics. At a concentration of 0.3 wt%, the MH storage capacity reaches 171.03 V / V, the water-hydrate conversion rate (WTH) reaches 85.42%, and the induction time is shortened to 2.5 min. Furthermore, this surfactant exhibits a unique foam-free advantage; in three cyclic experiments, it achieved rapid dissociation within 55 min without foam generation, effectively solving the problem of foam hindering mass transfer and dissociation in traditional technologies. Third, the surfactant synthesized in this invention exhibits excellent environmental friendliness. In LB medium under the action of the surfactant, Escherichia coli colonies continued to grow to 239 within 72 hours, essentially covering the entire medium. This result proves that the surfactant synthesized in this invention does not significantly inhibit microbial growth, demonstrates excellent environmental friendliness, and has lower potential ecological risks. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the preparation process of the surfactant of the present invention; Figure 2 The characterization results of the surfactants prepared in the embodiments of the present invention are as follows, wherein, Figure 2 a represents the ATR-FTIR spectrum. Figure 2 b represents the element distribution; Figure 3 The performance test results of the surfactants prepared in the embodiments of the present invention are as follows, wherein, Figure 3 a represents the curve of conductivity versus concentration. Figure 3 b is the TGA curve. Figure 3 c is the contact angle on the steel plate. Figure 3d represents surface tension; Figure 4 The results show the performance analysis of the surfactant prepared in this invention during the MH generation process in solutions of different concentrations. Figure 4 'a' represents the pressure change curve. Figure 4 b represents the gas storage capacity; Figure 5 The induction time and WTH conversion rate of the surfactant prepared in this invention in solutions of different concentrations; Figure 6 The pressure change curve of the surfactant prepared in this invention under three cycles at 0.3 wt% MH; Figure 7 The foam-forming ability analysis results of the surfactant prepared in this invention are as follows, wherein, Figure 7 'a' represents the foam-forming ability of the surfactant solution. Figure 7 b represents the foam-forming ability during the dissociation of MH; Figure 8 The growth of Escherichia coli colonies in LB medium under the action of the surfactant prepared in this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example: like Figure 1 The diagram illustrates a method for preparing a highly efficient, non-foaming, and environmentally friendly surfactant, comprising the following steps: S1: Synthesis of intermediates 7.8448 g of maleic anhydride, 13.94 mL of n-nonyl alcohol, and 60 mL of N,N-dimethylformamide (DMF) (molar ratio of 1:1:11) were added to a round-bottom flask. The mixture was magnetically stirred at 300 rpm for 12 h at 60 °C to allow the esterification reaction to proceed fully. During the reaction, the hydroxyl group on the n-nonyl alcohol nucleophilically attacked the carbonyl carbon atom in the maleic anhydride, forming an ester bond through a dehydration condensation reaction, ultimately yielding an intermediate product containing a carbon-carbon double bond. S2: Preparation of surfactants After the reaction in step S1 was completed, 100 mL of a 5.7% sodium bisulfite aqueous solution and 50 mL of isopropanol were added to the reaction system. The system was then heated to 100 °C and magnetically stirred at 300 rpm for 24 h to ensure the addition reaction proceeded fully, thus preparing a surfactant with a 9-carbon hydrophobic tail and a sulfonic acid group hydrophilic head. After the reaction was complete, the solution was transferred to a rotary evaporator and concentrated at 80 °C for 3 h. The solid precipitated after solvent removal was separated by filtration to obtain a white precipitate, which was then vacuum dried at 50 °C for 12 h. Finally, the precipitate was ground to obtain the surfactant powder sample NMS9. In the reaction process in step S2, sodium bisulfite undergoes a sulfonation reaction with the intermediate containing carbon-carbon double bonds obtained in step S1, introducing sulfonic acid groups into the molecular structure, thereby successfully preparing a surfactant, which is named NMS9, where 9 represents the number of carbon atoms in n-nonanol.

[0023] The performance of the prepared NMS9 was tested: 1. ATR-FTIR spectrum and elemental distribution analysis of surfactant NMS9 This invention utilizes a Fourier transform infrared spectroscopy (Nicolet iS50, USA) and scanning electron microscopy with energy-band spectroscopy software (BRUKERQUANTAX ESPRIT) to characterize the functional groups and elemental composition of the surfactant NMS9. In the ATR-FTIR test, 2 mg of sample was uniformly spread on the surface of a preheated ATR crystal, and pressure was applied to eliminate air gaps. The test parameters were set as follows: 16 scans, 4 cm⁻¹ resolution. -1 Scanning range 4000~400 cm -1 Before EDS analysis, the sample was treated with ion sputtering gold, and its elemental composition was then analyzed using energy scattering spectroscopy software. The results are as follows: Figure 2 As shown.

[0024] like Figure 2 As shown in figure a, surfactant NMS9 at 1231 cm⁻¹ -1 The characteristic peak at 2920 cm⁻¹ is attributed to the stretching vibration of S=O in the sulfonic acid group; -1 With 2967 cm -1 The absorption peaks at 3325 cm⁻¹ correspond to the stretching vibrations of the methylene (-CH₂-) and methyl (-CH₃) groups, respectively. These vibrational peaks are consistent with the characteristic peak positions of n-nonyl alcohol, confirming the presence of a long alkyl chain in the product. Notably, the absorption peak at 3325 cm⁻¹ in n-nonyl alcohol... -1 The hydroxyl (-OH) stretching vibration peak at , and the peak at 1856 cm⁻¹ in maleic anhydride (MA). -1 1778 cm -1(C=O) and 1057 cm -1 The characteristic peaks at (CO) completely disappeared in the NMS spectrum. This phenomenon proves that esterification and subsequent ring-opening addition reactions occurred between the starting materials during the synthesis process. Furthermore, Figure 2 EDS analysis of b showed that the surfactant was composed of four elements: C, O, Na, and S. Its actual elemental composition was highly consistent with the theoretical molecular structure, further confirming the successful preparation of the target product.

[0025] 2. Conductivity-concentration relationship, thermogravimetric analysis (TGA), contact angle and surface tension tests and results of surfactant NMS9 on steel plate. This invention utilizes a conductivity meter (DDS-11A), a thermogravimetric analyzer (Shimadzu TGA-50), and a droplet shape analyzer (SDC-350) to systematically characterize the conductivity, thermal stability, contact angle, and surface tension of the surfactant NMS9. The results are as follows: Figure 3 As shown.

[0026] like Figure 3 As shown in Figure a, the conductivity of the surfactant NMS9 solution increases with increasing concentration. At a concentration of 0.3 wt%, the rate of increase in conductivity slows significantly; this inflection point corresponds to the onset of micelle formation. Therefore, the critical micelle concentration (CMC) of this surfactant is determined to be 0.3 wt%. Thermogravimetric analysis (TGA) curves ( Figure 3 (b) shows that the sample lost approximately 0.96 wt% of weight in the initial stage (<178 °C), mainly due to the evaporation of residual moisture; in the 178–278 °C range, the organic framework began to break, resulting in a weight loss of 12.30 wt%; when the temperature rose to 310 °C, the weight loss was approximately 40.02 wt%, mainly due to the breaking of sulfonic acid groups (SO, SC bonds), ester bonds, and main chain CC bonds; thereafter, the weight loss rate slowed significantly, indicating that the remaining components were mainly stable carbonized residues. Overall, the surfactant NMS9 exhibits excellent high-temperature stability. Furthermore, the contact angle ( Figure 3 c) and surface tension ( Figure 3 The test results in d) show that both the contact angle and surface tension initially decrease and then increase (or tend to stabilize) with increasing concentration, reaching their optimal state near the CMC value (0.3 wt%). At this point, the contact angle drops sharply to 31.5°, and the surface tension drops to its lowest value of 16.13 mN / m. This phenomenon indicates that at a concentration of 0.3 wt%, NMS molecules reach a saturated adsorption state at both the solid-liquid and gas-liquid interfaces, thus achieving dual optimization of wetting performance and surface tension, demonstrating its great application potential in efficiently improving gas-liquid mass transfer.

[0027] 3. Pressure change curves and gas storage capacity test results of surfactant NMS9 promoting MH generation in solutions of different concentrations. The experiment was conducted using a high-pressure stainless steel reactor with an effective volume of 600 mL and a pressure resistance limit of 20 MPa. First, 250 mL of NMS9 surfactant solutions of different concentrations (0.1 wt%, 0.3 wt%, 0.5 wt%, and 0.7 wt%) were added to the reactor. Then, the reactor was placed in a constant-temperature water bath, and the temperature was set (275.15 K) and maintained. Next, methane gas was introduced into the reactor until the pressure reached 6 MPa, initiating the hydration reaction. During the reaction, a data acquisition system connected to a computer automatically recorded time, temperature, and pressure data every 5 seconds to monitor the kinetics of MH formation in real time. The results are as follows: Figure 4 As shown.

[0028] like Figure 4 As shown in Figure a, the pressure of the NMS9 surfactant systems at all concentrations decreased rapidly over time, and the final stable pressure remained at around 3.3 MPa. Notably, the 0.3 wt% NMS9 surfactant system performed particularly well, with an induction time of almost zero, achieving instantaneous reaction initiation.

[0029] Gas storage capacity is a core indicator for evaluating the performance of kinetic promoters, and its calculation formula is shown in equation (1). Figure 4 As shown in b, the surfactant NMS9 significantly promotes the gas storage capacity of MH. The peak gas storage capacity of 171.03 V / V is achieved at a concentration of 0.3 wt%. This indicates that the surfactant NMS9 exhibits excellent surface activity even at low concentrations, potentially improving MH gas storage performance while also reducing environmental risks and economic costs in practical applications.

[0030] (1) in, The volume of water consumed to generate MH. The amount of gas molar storage within a given time range can be determined using formulas (2) and (3).

[0031] (2) It is the gas compressibility coefficient determined by the corresponding relationship under specific conditions, and is determined by the Peng-Robinson equation of state (3).

[0032] (3) in, , , These are the pressures (MPa) under initial, final, and critical conditions, respectively. , , These are the temperatures (K) under the initial, final, and critical conditions, respectively. yes t The gas phase volume at time t. R is the gas constant (8.3145 J·mol⁻¹). -1 ·K -1 ), where ω is the eccentricity factor.

[0033] 4. Induction time and WTH conversion rate of surfactant NMS9 in solutions of different concentrations Induction time (t) ind The time required from the start of the reaction to the stable formation of crystal nuclei is defined as t0. In this experiment, the moment when the aeration pressure reaches the target value (6 MPa) is denoted as t0, and the moment when the pressure begins to decrease is denoted as t1. n WTH conversion rate is defined as the number of moles of MH converted from each mole of initial water. Accordingly, the induction time and WTH conversion rate can be calculated using formulas (4) and (5), respectively. Figure 5 As shown, surfactant NMS9 exhibited the best performance at a concentration of 0.3 wt%, with an induction time of only 2.5 min and a WTH conversion rate as high as 85.42%. Notably, as the concentration continued to increase, surfactant NMS9 did not show drastic performance fluctuations; although the performance indicators slightly declined, they remained at a high level.

[0034]

[0035] in, M It is the water element. n w It is the number of moles of water.

[0036] 5. Cyclic stability test and results of surfactant NMS9 promoting MH formation at a concentration of 0.3 wt%. To evaluate the practical application potential of surfactant NMS9 as a gas storage medium for MH, this invention conducted three cyclic experiments with 0.3 wt% surfactant NMS9, and the pressure change curves are shown below. Figure 6As shown in the figure, the dissociation peak pressure remained stable at 6.5 MPa for all three cycles, while the generation pressure remained within a narrow range of 3.2-3.3 MPa with minimal fluctuation. This high repeatability strongly demonstrates the excellent cycling stability of this surfactant. Notably, this stability is a direct reflection of the intact molecular structure, indicating that the structure of surfactant NMS9 remained undamaged during multiple cycles, thus enabling it to continuously exert a stable promoting effect and ensure its effectiveness over long-term use.

[0037] 6. Test results on the foam-forming ability of surfactant NMS9 solution and MH during dissociation process. This invention uses a 500 mL graduated cylinder in conjunction with a high-powered microscope (XSP-H1600) to characterize the foam-forming ability during the dissociation of MH. The graduated cylinder is used for macroscopic observation of foam volume and stability, while the high-powered microscope is used to capture the microscopic morphological characteristics of the foam. The results are as follows: Figure 7 As shown.

[0038] like Figure 7 As shown in Figure a, after bubbling nitrogen gas into a solution of surfactant NMS9 for 5 seconds, only a foam layer with a height of approximately 8 mm was formed, indicating that the solution lacks the ability to form stable foam. Based on this, the present invention further investigated the foaming behavior of MH during its dissociation process at room temperature. Figure 7 (b) Observations showed that no foam was generated throughout the entire dissociation process of MH. The above qualitative observations and quantitative analysis results jointly confirm that the surfactant NMS9 prepared in this invention has extremely low foaming properties.

[0039] 7. Environmental friendliness test results of surfactant NMS9 In this experiment, 1.0 g peptone, 0.5 g yeast extract, 1.0 g sodium chloride, and 1.5 g agar powder were dissolved in 100 mL of deionized water, and the pH was adjusted to 7.0 with 5 mol / L NaOH to prepare LB solid culture medium. The growth activity of *E. coli* was used as the key indicator for analysis and evaluation. The colony counting method was used to quantitatively analyze the growth rate of *E. coli* in LB medium at a concentration of 3 × 10⁶ cells / mL under the action of 0.3 wt% surfactant NMS9. 8 The evolution of E. coli colony count (CFU / mL) over time, as shown in the results. Figure 8As shown in the figure, the experimental results indicate that *E. coli* exhibited vigorous growth activity in the NMS9-treated group. The colony count continued to increase within 72 hours, eventually reaching 239 colonies, with an average growth rate of 3.32 colonies / hour, and the colonies essentially covered the entire surface of the culture medium. This result confirms that the NMS9 surfactant has no inhibitory effect on the growth of *E. coli*. In summary, the NMS9 surfactant prepared in this invention exhibits excellent biocompatibility and has low potential ecological risk.

[0040] Based on the aforementioned experimental results, this invention successfully prepared a highly efficient, non-foaming, and environmentally friendly surfactant. This surfactant, while strictly adhering to green chemistry principles, significantly improved the formation kinetics of MH and effectively suppressed foam generation during the dissociation process, achieving the integration and optimization of multiple properties. 1. Significantly improves the generation kinetics of MH: At a concentration of 0.3 wt%, this surfactant not only increases the MH storage capacity and WTH conversion rate to 171.03 V / V and 85.42%, respectively, but also significantly shortens the induction time to 2.5 min.

[0041] 2. Excellent foam suppression ability: The surfactant NMS9 forms only a foam layer with a height of about 8 mm on the solution surface, exhibiting extremely poor foam stability. Furthermore, no foam generation was observed during the process of promoting the dissociation of generated MH, achieving a good foam suppression effect.

[0042] 3. Excellent environmental friendliness: After 72 h of culture, the number of Escherichia coli colonies on LB medium treated with surfactant increased to 239, with an average growth rate of 3.32 colonies / h, indicating that the surfactant has extremely low ecotoxicity.

[0043] This surfactant possesses multiple properties such as high efficiency, non-foaming, and environmental friendliness, and can significantly improve hydrate formation kinetics, thus providing a powerful promoter solution for the large-scale industrial application of hydrate-based gas storage technology.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a highly efficient, non-foaming, and environmentally friendly surfactant, characterized in that, Includes the following steps: S1: Maleic anhydride and a monohydric saturated alcohol are dissolved in N,N-dimethylformamide in a 1:1 molar ratio and esterified under heating and stirring conditions to obtain an intermediate containing carbon-carbon double bonds. S2: Sodium bisulfite aqueous solution and co-solvent are added to the reaction system of the intermediate, and a sulfonation addition reaction is carried out under heating conditions. After the reaction is completed, the solution is concentrated, filtered, dried and ground to obtain the surfactant in powder form.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of the monohydric saturated alcohol to the N,N-dimethylformamide is 1:10-15.

3. The preparation method according to claim 1, characterized in that, In step S2, the mass concentration of the sodium bisulfite aqueous solution is 1%-10%.

4. The preparation method according to claim 1, characterized in that, In step S2, the co-solvent is at least one of isopropanol, ethanol, or n-propanol.

5. The preparation method according to claim 1, characterized in that, The heating conditions in step S1 are: heating at 50 ℃-80 ℃ for a reaction time of 6 h-24 h.

6. The preparation method according to claim 1, characterized in that, The heating conditions in step S2 are: heating at 100 °C for a reaction time of 6 h-24 h.

7. The preparation method according to claim 1, characterized in that, In step S2, the concentration is a rotary evaporation concentration, and the process conditions for rotary evaporation concentration are 3 hours at 80 °C.

8. The preparation method according to claim 1, characterized in that, The monohydric saturated alcohol is a straight-chain or branched monohydric alcohol with a carbon number of 8 to 18.

9. A highly efficient, non-foaming, and environmentally friendly surfactant, characterized in that, It is prepared by the preparation method described in claim 1.

10. The application of the efficient, non-foaming, and environmentally friendly surfactant according to claim 9 in the fields of hydration, cleaning, emulsification, or wetting.

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