A method for evaluating temperature resistance of a surfactant based on molecular dynamics simulation

Abstract

The present application belongs to the technical field of molecular dynamics simulation, and particularly relates to a method for evaluating temperature resistance of surfactants based on molecular dynamics simulation. The present application constructs an initialization model of an oil phase / surfactant / water phase simulation system, optimizes the initialization model, and obtains an optimized model of the oil phase / surfactant / water phase simulation system with minimized energy. The optimized model of the oil phase / surfactant / water phase simulation system is subjected to molecular dynamics simulation analysis to obtain simulation results. The influence of the surfactant molecular structure and the simulation temperature on the interfacial activity is judged according to the simulation results, so as to evaluate the temperature resistance of the surfactant. The present application can quickly and accurately reveal the interaction mechanism between the surfactant molecular structure and the temperature, thereby guiding the development of new temperature-resistant surfactants. The method of the present application is clean and environmentally friendly, easy to operate, and low in overall cost, and can verify and test unknown or assumed new surfactants.

Description

Technical Field

[0001] This invention belongs to the field of molecular dynamics simulation technology, specifically relating to a method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation. Background Technology

[0002] In the petrochemical industry, surfactants are the core oil displacement agents in chemical flooding, enhancing oil recovery by reducing oil-water interfacial tension, altering wettability, and promoting emulsification. Surfactants are also widely used in the construction of dispersion systems, fluid viscosity control, and enhanced solubility. Research and testing show that introducing surfactants can significantly improve the fluidity of high-viscosity crude oil and effectively prevent the accumulation and retention of heavy components in reservoir pores.

[0003] However, the temperature resistance of surfactants has always been a core factor restricting their effective, stable, and safe use in specific high-temperature environments. High temperatures easily damage the molecular structure of surfactants, disrupting their stable adsorption at the interface and causing them to lose their solubilizing, emulsifying, and dispersing functions, resulting in a sharp decline in interfacial performance. Especially in the fields of oil and gas extraction and high-temperature processing, temperature resistance is a key indicator for evaluating surfactant quality. However, traditional experimental methods for testing the temperature resistance of surfactants are limited by technology, time, and space. They can usually only measure macroscopic final-state data and cannot capture the dynamic adsorption process at the molecular scale in situ, thus making it difficult to reveal the intrinsic influence of temperature on the interfacial activity of surfactant molecules. At the same time, the experimental procedures are cumbersome, time-consuming, and inefficient, making it difficult to quickly verify unknown or hypothetical novel structures. This makes it difficult to quickly and accurately determine the mechanism by which molecular structure and ambient temperature affect adsorption performance, ultimately leading to high costs and long development cycles in the design and development of new temperature-resistant or temperature-tunable surfactants. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation. This invention utilizes molecular dynamics simulation to study the interactions of an oil-phase / surfactant / aqueous-phase simulated system, revealing the interaction mechanism between surfactant molecular structure and temperature. This guides the development of novel temperature-resistant surfactants and solves the technical problems of traditional experimental methods, which struggle to reveal the intrinsic influence of temperature on the interfacial activity of surfactant molecules and to quickly and accurately determine the mechanisms by which molecular structure and ambient temperature affect adsorption performance. Ultimately, this leads to high costs and long development cycles in the design and development of novel temperature-resistant or temperature-adjustable surfactants.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] This invention provides a method for evaluating the temperature resistance of surfactants based on molecular dynamics simulations, comprising the following steps:

[0007] An initial model of the oil-phase / surfactant / aqueous phase simulation system was constructed. The initial model was then structurally optimized to obtain an optimized model that minimized energy. Molecular dynamics simulations were performed on the optimized model to obtain simulation results of surfactant molecules at the oil-water interface under different simulation temperatures. The simulation results included the interfacial distribution region, adsorption configuration, interfacial adsorption energy, and interfacial tension of the surfactant at the oil-water interface. Based on the simulation results, the influence of surfactant molecular structure and simulation temperature on interfacial activity was determined to evaluate the temperature resistance of the surfactant.

[0008] This invention first constructs a rationally configured oil / surfactant / water simulation system, then performs molecular dynamics simulation analysis to obtain simulation results; based on the analysis of the simulation results, it evaluates the temperature resistance performance of the surfactant. The method of this invention provides a way to reveal the differences in surfactant molecular structure and the influence of system temperature on its oil-water interfacial activity from a molecular perspective. This method is clean and environmentally friendly, differs from traditional experimental methods, is easy to operate, and has low overall cost.

[0009] This invention uses molecular dynamics simulations to clearly obtain specific information such as the distribution area, adsorption configuration, interfacial adsorption energy, and interfacial tension of surfactant molecules at the oil-water interface. The simulation method described in this invention requires running multiple simulation systems independently at different temperatures to systematically compare the changes in the distribution, adsorption configuration, interfacial adsorption energy, and interfacial tension of surfactants at the oil-water interface under different temperatures, and finally evaluate the temperature resistance of the surfactants.

[0010] The preferred method for obtaining an optimized model of the oil phase / surfactant / aqueous phase simulation system is as follows:

[0011] An initial model for the oil phase, an initial model for the aqueous phase, and an initial model for the surfactant were constructed. These initial models were then assembled to obtain an initial model for the oil / surfactant / aqueous phase simulation system. The initial model was then structurally optimized to obtain an optimized model for the oil / surfactant / aqueous phase simulation system that minimizes energy.

[0012] Preferably, the initial oil phase model is as follows: Figure 1 As shown, it includes four straight-chain alkanes with different carbon numbers. The four straight-chain alkanes with different carbon numbers are C 13 H 28 C 15 H 32 C 18 H38 and C 21 H 44 .

[0013] In this invention, C 13 H 28 C 15 H 32 C 18 H 38 C 21 H 44 The mass fractions of the oil phase in the initial model were 4.23%, 90.12%, 4.39%, and 1.27%, respectively.

[0014] Preferably, in the initial oil phase model, C 13 H 28 The number of molecules is 5, C 15 H 32 The number of molecules is 101, C 18 H 38 The number of molecules is 4, C 21 H 44 The number of molecules is 1; the initial model of the oil phase is a cubic lattice model, with a length and width of 5 nm and a density of 0.8 g / cm³. 3 .

[0015] Preferably, the initial aqueous phase model is as follows: Figure 2 As shown, the number of water molecules is 1500; the initial water phase model is a cubic lattice model with a length and width of 5 nm and a density of 1.0 g / cm³. 3 .

[0016] Preferably, the initial surfactant model has 5 molecules, such as... Figure 3 As shown, the initial model of the surfactant is a cubic lattice model with a length and width of 5 nm and a density of 0.8 g / cm³. 3 .

[0017] This invention utilizes the Sketch function of Materials Studio software to construct surfactant molecules with different structures and performs geometric optimization to obtain the final optimized bond lengths, bond angles, and dihedral angles of the molecular topology, such as oleic acid, oleamide, linoleic acid, linoleamide, abietic acid, abiamide, and bisrosinamide. Then, the Amorphous CellConstruction module is used to construct an initial surfactant model containing five molecules, with the model density set to 0.8 g / cm³. 3 The length and width of the fixed system are both 5nm.

[0018] The preferred method for constructing an initial model of the oil phase / surfactant / aqueous phase simulation system is as follows:

[0019] like Figure 4 As shown, an initial model of the oil phase / surfactant / aqueous phase simulation system is constructed by using the initial oil phase model as the first layer, the initial surfactant model as the second layer, and the initial aqueous phase model as the third layer.

[0020] Preferably, the simulation temperature is 298K to 453K. In this invention, the molecular dynamics simulation is an equilibrium molecular dynamics simulation with a time step of 0.2fs and a simulation time of 300ps, and the trajectory file of the system is recorded.

[0021] Preferably, the surfactant is oleic acid, oleamide, linoleic acid, linoleamide, rosin acid, rosinamide, or bisrosinamide. This invention does not limit the surfactant to specifically oleic acid, oleamide, linoleic acid, linoleamide, rosin acid, rosinamide, or bisrosinamide; it can also be other artificially designed surfactant molecules.

[0022] In this invention, the formula for calculating the interfacial adsorption energy is: E interface =E A-B -E A -E B ;in, E interface It is the interfacial adsorption energy; E A-B The total energy of the simulated oil phase / surfactant / aqueous phase system; E A The total energy of the oil and water phases; E B This represents the total energy of the surfactant.

[0023] The formula for calculating interfacial tension is: ;in, γ Let z be the interface tension; let the normal direction of the interface be the z-direction, and the two mutually orthogonal directions within the interface be the x-direction and y-direction. L z To optimize the model's dimensions in the z-direction; P zz For the pressure tensor component in the z-direction; P xx The pressure tensor component in the x-direction ；P yy The pressure tensor component is in the y-direction. In this invention, the z-direction is perpendicular to the interface.

[0024] This invention primarily evaluates the temperature resistance of surfactants by comprehensively analyzing the changes in the distribution area, adsorption configuration, interfacial adsorption energy, and interfacial tension of surfactants at the oil-water interface under different temperature conditions.

[0025] In this invention, such as Figure 5 The surfactant molecule interface distribution region shown in (a) is as follows: Figure 5 The adsorption configuration shown in (b) is the final result at the end of the simulation. The interfacial adsorption energy and interfacial tension are both average values ​​from the last 50 ps of the molecular simulation. Figure 6 Figure (a) shows the change in interfacial adsorption energy throughout the simulation process. Figure 6 In the middle (b), the average value of the interfacial adsorption energy in the last 50 ps simulation is shown.

[0026] In this invention, the method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity is based on the interfacial distribution region, interfacial adsorption energy, and surface tension.

[0027] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on the interfacial distribution region is as follows: As the simulated temperature increases, when the surfactant is concentrated near the oil-water interface and the interfacial distribution region tends to stabilize, the surfactant exhibits good temperature resistance within the simulated temperature range. At this point, temperature has a relatively small impact on the interfacial activity of the surfactant.

[0028] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on interfacial adsorption energy is as follows: as the simulated temperature increases, the lower the decay rate of the surfactant's interfacial adsorption energy, or the more stable the interfacial adsorption energy tends to be, the better the surfactant's temperature resistance within the simulated temperature range. At this point, temperature has a relatively small impact on the surfactant's interfacial activity.

[0029] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on surface tension is as follows: the lower the decay rate of the surfactant's surface tension as the simulated temperature increases, or the better the surface tension stability, the better the surfactant's temperature resistance within the simulated temperature range.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention can construct an accurate oil / surfactant / water system model, and explain the interaction mechanism between the surface active molecule structure and system temperature and the oil and water phases from a molecular perspective. Based on the advantages of computer simulation, it can effectively reduce the time cost of trial and error, reduce experimental costs, predict the temperature resistance performance of surfactants with different molecular structures, and shorten the time required for surfactant molecule optimization.

[0032] At the same time, by setting different temperatures and different surfactant molecular weights, the optimal operating temperature and optimal dosage of surfactants can be accurately evaluated, providing a reference for the selection of surfactants under different environments.

[0033] 2. This invention provides a simulation method for studying the interaction of oil phase / surfactant / aqueous phase simulation systems based on molecular dynamics simulation. This method can quickly and accurately reveal the interaction mechanism between surfactant molecular structure and temperature, thereby guiding the development of novel temperature-resistant surfactants.

[0034] 3. This invention reveals the molecular structure differences of surfactants and the influence of system temperature on their oil-water interfacial activity from a molecular perspective. The method of this invention is clean and environmentally friendly, different from traditional experimental methods, easy to operate, and has low overall cost. It can be used to verify and test unknown or hypothetical novel surfactants. Attached Figure Description

[0035] Figure 1 The initial oil phase model is used as an example.

[0036] Figure 2 The initial aqueous phase model is used as an example.

[0037] Figure 3 The surfactant is the initial model for the example.

[0038] Figure 4 This is the initial model of the oil / surfactant / water system used in the example.

[0039] Figure 5 The following diagrams show the density distribution and adsorption configuration of the surfactant at the oil-water interface at the end of the simulation of the oil / surfactant / water system in this example. (a) shows the density distribution at the oil-water interface; (b) shows the adsorption configuration at the oil-water interface.

[0040] Figure 6 The following is a simulation of the change in surfactant interfacial adsorption energy under different temperature conditions. (a) shows the change in surfactant interfacial adsorption energy at different temperatures during the simulation process; (b) shows the average interfacial adsorption energy of the simulation system at equilibrium at different temperatures.

[0041] Figure 7 This is the molecular structure model of the surfactant in Example 1.

[0042] Figure 8 This is the molecular structure model of the surfactant in Example 2.

[0043] Figure 9The diagrams show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at temperatures of 298K and 338K, respectively, in Example 1. (a) and (b) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 298K, respectively; (c) and (d) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 338K, respectively.

[0044] Figure 10 The diagrams show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at temperatures of 423K and 453K, respectively, in Example 1. Specifically, (a) and (b) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 423K, and (c) and (d) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 453K, respectively.

[0045] Figure 11 This is a graph showing the change in interfacial adsorption energy of surfactant molecules at the oil-water interface under different temperature conditions in Example 1.

[0046] Figure 12 This is a graph showing the surface tension changes of surfactant molecules at the oil-water interface under different temperature conditions in Example 1.

[0047] Figure 13 The diagram shows the density distribution and adsorption configuration changes of surfactant molecules at the oil-water interface under temperature conditions of 298K and 338K in Example 2. (a) and (b) are the density distribution and adsorption configuration diagrams of surfactant molecules at the oil-water interface at 298K, respectively; (c) and (d) are the density distribution and adsorption configuration diagrams of surfactant molecules at the oil-water interface at 338K, respectively.

[0048] Figure 14 The diagrams show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at temperatures of 423K and 453K, respectively, in Example 2. Specifically, (a) and (b) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 423K, and (c) and (d) show the density distribution and adsorption configuration of surfactant molecules at the oil-water interface at 453K, respectively.

[0049] Figure 15 This is a graph showing the change in interfacial adsorption energy of surfactant molecules at the oil-water interface under different temperature conditions in Example 2.

[0050] Figure 16 This is a graph showing the surface tension changes of surfactant molecules at the oil-water interface under different temperature conditions in Example 2. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] 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.

[0053] A method for evaluating the temperature resistance of surfactants based on molecular dynamics simulations includes the following steps:

[0054] Step 1: Construct an initial model of the oil phase / surfactant / aqueous phase simulation system, optimize the structure of the initial model, and obtain an optimized model of the oil phase / surfactant / aqueous phase simulation system with minimum energy.

[0055] The method for obtaining an optimized model of the oil phase / surfactant / aqueous phase simulation system is as follows:

[0056] Step 1.1: Construct the initial model of the oil phase.

[0057] In this embodiment of the invention, the initial oil phase model includes four straight-chain alkanes with different carbon numbers, namely C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, 13 H 28 C 15 H 32 C 18 H 38 and C 21 H 44 C 13 H 28 The number of molecules is 5, C 15 H 32 The number of molecules is 101, C 18 H 38 The number of molecules is 4, C 21 H 44 The number of molecules is 1.

[0058] The methods for constructing the initial model of the oil phase include: using the Sketch Atom function of Materials Studio software to model four straight-chain alkanes with different carbon numbers. 13 H 28 C 15 H 32 C 18 H 38 C 21 H 44Molecular construction was performed, and then the AmorphousCell Construction module was used to construct a structure containing 5 C atoms. 13 H 28 Molecules, 101 C 15 H 32 molecule, 4 C 18 H 38 molecule and 1 C 21 H 44 Initial model of the oil phase for molecules; the density of the initial oil phase model is 0.8 g / cm³. 3 The length and width of the initial oil phase model were both set to 5 nm.

[0059] Step 1.2: Construct the initial model of the aqueous phase.

[0060] In this embodiment of the invention, the number of water molecules in the initial aqueous phase model is 1500.

[0061] The method for constructing the initial aqueous phase model includes: using the Amorphous CellConstruction module of Materials Studio software to construct an initial aqueous phase model containing 1500 water molecules; the density of the initial aqueous phase model is 1.0 g / cm³. 3 The length and width of the initial aqueous phase model were both set to 5 nm, and the final simulation system size of the initial aqueous phase model was 5 nm × 5 nm × 1.794 nm.

[0062] Step 1.3: Construct the initial model of the surfactant.

[0063] The method for constructing the initial surfactant model includes: using the Sketch function of Materials Studio software to construct the surfactant molecular configuration and perform geometric optimization; then using the Amorphous Cell Construction module to construct an initial surfactant model containing 5 molecules, with a density of 0.8 g / cm³. 3 The length and width of the initial surfactant model were both set to 5 nm.

[0064] Step 1.4: Assemble the initial models of the oil phase, water phase, and surfactant to obtain the initial model of the oil / surfactant / water phase simulation system.

[0065] The method for constructing the initial model of the oil-phase / surfactant / aqueous phase simulation system includes: using the build Layers function of MaterialsStudio software, with the oil phase initial model as Layer 1, the surfactant initial model as Layer 2, and the aqueous phase initial model as Layer 3, to construct the initial model of the oil-phase / surfactant / aqueous phase simulation system. The simulation system size of the initial model is 5nm × 5nm × 9nm.

[0066] Step 1.5: Optimize the structure of the initial model to obtain an optimized model of the oil / surfactant / aqueous phase simulation system with minimal energy.

[0067] The methods for structural optimization of the initialization model include: using the COMPASS III force field, selecting the Steep algorithm for the energy minimization process, and setting the maximum number of iterations to 5000.

[0068] Step 2: Perform molecular dynamics simulation analysis on the optimized model of the oil phase / surfactant / water phase simulation system to obtain the simulation results of surfactant molecules at the oil-water interface under different simulation temperature conditions. The simulation results include the interfacial distribution region, adsorption configuration, interfacial adsorption energy and interfacial tension of the surfactant at the oil-water interface. Based on the simulation results, determine the influence of surfactant molecular structure and simulation temperature on interfacial activity to evaluate the temperature resistance of the surfactant.

[0069] The method for evaluating the temperature resistance of surfactants is as follows:

[0070] Step 2.1: Perform molecular dynamics simulation analysis on the optimized model of the oil phase / surfactant / water phase simulation system to obtain the simulation results of surfactant molecules at the oil-water interface under different simulation temperature conditions.

[0071] The methods for performing molecular dynamics simulation analysis are as follows:

[0072] The ensemble was set to NVT, the thermostat to Berendsen, the simulation temperature to be 298K to 453K, the electrostatic interaction force to be set to Ewald method, the van der Waals force to be Atom based, and the cutoff radius to be 1.25nm.

[0073] Molecular dynamics simulations were performed using equilibrium molecular dynamics with a time step of 0.2 fs and a simulation time of 300 ps. The energy and simulation temperature parameters of the optimized model were recorded.

[0074] Step 2.2: Based on the simulation results, determine the influence of surfactant molecular structure and simulation temperature on interfacial activity to evaluate the temperature resistance of surfactants.

[0075] The simulation results include the interfacial distribution region, adsorption configuration, interfacial adsorption energy, and interfacial tension of the surfactant at the oil-water interface.

[0076] The formula for calculating interfacial adsorption energy is: E interface =E A-B -E A -E B ;in, E interface It is the interfacial adsorption energy; E A-B The total energy of the simulated oil phase / surfactant / aqueous phase system; E A The total energy of the oil and water phases; E B This represents the total energy of the surfactant.

[0077] The formula for calculating interfacial tension is: ;in, γ Let z be the interface tension; let the normal direction of the interface be the z-direction, and the two mutually orthogonal directions within the interface be the x-direction and y-direction. L z To optimize the model's dimensions in the z-direction; P zz For the pressure tensor component in the z-direction; P xx The pressure tensor component in the x-direction ；P yy The pressure tensor component is in the y-direction. In this invention, the z-direction is perpendicular to the interface.

[0078] In this invention, the method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity is based on the interfacial distribution region, interfacial adsorption energy, and surface tension.

[0079] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on the interfacial distribution region is as follows: As the simulated temperature increases, when the surfactant is concentrated near the oil-water interface and the interfacial distribution region tends to stabilize, the surfactant exhibits good temperature resistance within the simulated temperature range. At this point, temperature has a relatively small impact on the interfacial activity of the surfactant.

[0080] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on interfacial adsorption energy is as follows: as the simulated temperature increases, the lower the decay rate of the surfactant's interfacial adsorption energy, or the more stable the interfacial adsorption energy tends to be, the better the surfactant's temperature resistance within the simulated temperature range. At this point, temperature has a relatively small impact on the surfactant's interfacial activity.

[0081] The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on surface tension is as follows: the lower the decay rate of the surfactant's surface tension as the simulated temperature increases, or the better the surface tension stability, the better the surfactant's temperature resistance within the simulated temperature range.

[0082] Based on the simulation results, the temperature resistance of surfactants is determined, providing a reference for the selection of surfactants under different environments.

[0083] The technical solution of the present invention will be further described below through specific embodiments. Unless otherwise specified, the methods described in the following embodiments are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0084] Example 1

[0085] A method for evaluating the temperature resistance of surfactants based on molecular dynamics simulations includes the following steps:

[0086] Step 1: Construct an initial model of the oil phase / surfactant / aqueous phase simulation system, optimize the structure of the initial model, and obtain an optimized model of the oil phase / surfactant / aqueous phase simulation system with minimum energy.

[0087] Step 1.1: Construct the initial model of the oil phase.

[0088] Using the Sketch Atom function in Materials Studio software, C4 of four straight-chain alkanes with different carbon numbers was analyzed. 13 H 28 C 15 H 32 C 18 H 38 C 21 H 44 Molecular construction was performed, and then the Amorphous Cell Construction module was used to construct, such as Figure 1 The initial oil phase model shown contains 5 C atoms. 13 H 28 101 C 15 H 32 4 Cs 18 H 38 And 1 C 21 H44 The initial density of the oil phase in the molecular model is 0.8 g / cm³. 3 The length and width of the initial oil phase model were both set to 5 nm.

[0089] Step 1.2: Construct the initial model of the aqueous phase.

[0090] like Figure 2 As shown, an initial aqueous phase model containing 1500 water molecules was constructed using the Amorphous Cell Construction module of Materials Studio software. The density of the initial aqueous phase model was 1.0 g / cm³. 3 The initial aqueous phase model was set to 5 nm in both length and width, and the final simulation system size of the initial aqueous phase model was 5 nm × 5 nm × 1.794 nm.

[0091] Step 1.3: Construct the initial model of bislinoleamide.

[0092] Build using the Sketch function of Materials Studio software, such as Figure 7 The bislinoleamide molecular configuration shown was geometrically optimized, and then constructed using the Amorphous Cell Construction module as follows: Figure 3 The diagram shows an initial model of bis(linoleic acid) amide containing 5 molecules. The density of the initial model of bis(linoleic acid) amide is set to 0.8 g / cm³. 3 The initial model of bis(linoleic acid amide) has a length and width of 5 nm.

[0093] Step 1.4: Assemble the initial models of the oil phase, aqueous phase, and bis(linoleic acid amide) to obtain the initial model of the oil phase / bis(linoleic acid amide) / aqueous phase simulation system.

[0094] Using the "build Layers" function in Materials Studio software, with the oil phase as the initial model (Layer 1), the bis(linoleic acid amide) as the initial model (Layer 2), and the aqueous phase as the initial model (Layer 3), the following model was constructed: Figure 4 The initial model of the oil phase / bislinoleamide / aqueous phase simulation system is shown, with length, width, and height of 5nm, 5nm, and 9nm, respectively.

[0095] Step 1.5: Optimize the structure of the initial model to obtain an optimized model of the oil phase / bislinoleic amide / aqueous phase simulation system with minimum energy.

[0096] The force field used is the COMPASS III force field, and the energy minimization process uses the Steep algorithm with a maximum number of iterations of 5000.

[0097] Step 2: Molecular dynamics simulation analysis is performed on the optimized model of the oil phase / bislinoleic amide / aqueous phase simulation system to obtain the simulation results of bislinoleic amide molecules at the oil-water interface under different simulation temperatures. The simulation results are the interfacial distribution region, adsorption configuration, interfacial adsorption energy and interfacial tension of bislinoleic amide at the oil-water interface. Based on the simulation results, the influence of bislinoleic amide molecular structure and simulation temperature on interfacial activity is determined to evaluate the temperature resistance performance of bislinoleic amide.

[0098] Step 2.1: Perform molecular dynamics simulation analysis on the optimized model of the oil phase / bislinoleic amide / aqueous phase simulation system to obtain the simulation results of bislinoleic amide molecules at the oil-water interface under different simulation temperature conditions.

[0099] Molecular dynamics simulations were performed using equilibrium molecular dynamics simulations. Four independent simulation systems were constructed at temperatures of 298K, 338K, 423K, and 453K. The ensemble for each system was NVT, the thermostat was Berendsen, the electrostatic interaction force was set to the Ewald method, and the van der Waals force was based on the atom method with a cutoff radius of 1.25nm.

[0100] The time step was 0.2 fs, the simulation time was 300 ps, ​​and the energy and simulation temperature parameters of the optimized model were recorded.

[0101] Step 2.2: Based on the simulation results, determine the influence of the molecular structure of bislinoleic amide and the simulation temperature on the interfacial activity, in order to evaluate the temperature resistance performance of bislinoleic amide.

[0102] The density distribution and adsorption configuration of bislinoleamide molecules at the oil-water interface are as follows: Figure 9 and Figure 10 As shown, under different temperature conditions, bislinoleamide molecules exhibit good surface activity, and surfactant molecules aggregate near the oil-water interface. However, as the temperature increases, the distribution width of bislinoleamide molecules near the interface gradually increases from 2.575 nm at 298 K to about 3.282 nm at 423 K and 3.123 nm at 453 K. It can be seen that as the temperature increases, the distribution area of ​​bislinoleamide molecules at the oil-water interface becomes larger and larger, and its surface activity continuously decreases.

[0103] The analysis results of the interfacial adsorption energy of the bislinoleamide molecule are shown in the figure. Figure 11The average interfacial adsorption energy of bislinoleamide molecules gradually decreases with increasing temperature. In the low-temperature range of 298K to 423K, the change in interfacial adsorption energy is relatively small. In the high-temperature range of 423K to 453K, the interfacial adsorption energy decreases rapidly with increasing temperature. Therefore, the analysis of interfacial adsorption energy shows that bislinoleamide molecules have good temperature resistance in the range of 298K to 423K, and the interfacial activity decreases only slightly with increasing temperature. However, in the high-temperature range from 423K to 453K, the interfacial activity of bislinoleamide decreases rapidly.

[0104] The change of interfacial tension of bislinoleamide molecules with temperature is shown in the figure. Figure 12 The interfacial tension of bislinoleamide molecules also showed a trend of gradually decreasing with increasing temperature. In the low-temperature range of 298K to 423K, the change in interfacial tension was relatively small. In the high-temperature range of 423K to 453K, the interfacial tension decreased significantly with increasing temperature. The results were consistent with the analysis of interfacial adsorption energy. Bislinoleamide molecules have good temperature resistance in the range of 298K to 423K, and the effect of increasing temperature on its interfacial activity is small. However, in the high-temperature range of 423K to 453K, the interfacial activity of bislinoleamide decreases rapidly with increasing temperature.

[0105] Example 2

[0106] A method for evaluating the temperature resistance of surfactants based on molecular dynamics simulations includes the following steps:

[0107] Step 1: Construct an initial model of the oil phase / surfactant / aqueous phase simulation system, optimize the structure of the initial model, and obtain an optimized model of the oil phase / surfactant / aqueous phase simulation system with minimum energy.

[0108] Step 1.1: Construct the initial model of the oil phase.

[0109] Using the Sketch Atom function in Materials Studio software, complete the creation of four straight-chain alkanes with different carbon numbers. 13 H 28 C 15 H 32 C 18 H 38 C 21 H 44 The molecular construction was then performed, and the Amorphous Cell Construction module was used to construct, as follows: Figure 1 The initial oil phase model shown contains 5 C atoms. 13 H 28 101 C 15 H 32 4 Cs18 H 38 1 C 21 H 44 The initial density of the oil phase in the molecular model is 0.8 g / cm³. 3 The length and width of the initial oil phase model were both set to 5 nm.

[0110] Step 1.2: Construct the initial model of the aqueous phase.

[0111] like Figure 2 As shown, an initial aqueous phase model containing 1500 water molecules was constructed using the Amorphous Cell Construction module of Materials Studio software. The length and width of the initial aqueous phase model were both set to 5 nm, and the density of the initial aqueous phase model was set to 1.0 g / cm³. 3 The final simulation system size of the initial aqueous phase model is 5nm×5nm×1.794nm.

[0112] Step 1.3: Construct the initial model of bisrosinamide.

[0113] Build using the Sketch function of Materials Studio software, such as Figure 8 The bis(rosinamide) molecular configuration shown was geometrically optimized, and the Amorphous Cell Construction module was used to construct the following structure: Figure 3 The diagram shows an initial model of bisrosinamide containing 5 molecules, with a density set to 0.8 g / cm³. 3 The initial model of bis(rosinamide) has a length and width of 5 nm.

[0114] Step 1.4: Assemble the initial models of the oil phase, aqueous phase, and bisrosinamide to obtain the initial model of the oil / bisrosinamide / aqueous phase simulation system.

[0115] Using the "build Layers" function in Materials Studio, the initial model for the oil phase was set as Layer 1, the initial model for the bis(rosinamide) phase as Layer 2, and the initial model for the aqueous phase as Layer 3, to construct the following model: Figure 4 The initial model of the oil phase / bisrosinamide / aqueous phase simulation system is shown, with length, width, and height of 5nm, 5nm, and 9nm, respectively.

[0116] Step 1.5: Optimize the structure of the initial model to obtain an optimized model of the oil phase / bisrosinamide / aqueous phase simulation system with minimized energy.

[0117] The force field used is the COMPASS III force field, and the energy minimization process uses the Steep algorithm with a maximum number of iterations of 5000.

[0118] Step 2: Molecular dynamics simulation analysis is performed on the optimized model of the oil phase / bisrosinamide / aqueous phase simulation system to obtain the simulation results of bisrosinamide molecules at the oil-water interface under different simulation temperatures. The simulation results are the interfacial distribution region, adsorption configuration, interfacial adsorption energy and interfacial tension of bisrosinamide at the oil-water interface. Based on the simulation results, the influence of bisrosinamide molecular structure and simulation temperature on interfacial activity is determined to evaluate the temperature resistance of bisrosinamide.

[0119] Step 2.1: Perform molecular dynamics simulation analysis on the optimized model of the oil phase / bisrosinamide / aqueous phase simulation system to obtain the simulation results of bisrosinamide molecules at the oil-water interface under different simulation temperature conditions.

[0120] Molecular dynamics simulations were performed using equilibrium molecular dynamics simulations. Four independent simulation systems were constructed at temperatures of 298K, 338K, 423K, and 453K. The ensemble for each system was NVT, the thermostat was Berendsen, the electrostatic interaction force was set to the Ewald method, and the van der Waals force was based on the atom method with a cutoff radius of 1.25nm.

[0121] The time step was 0.2 fs, the simulation time was 300 ps, ​​and parameters such as energy and temperature of the system were recorded.

[0122] Step 2.2: Based on the simulation results, determine the influence of the molecular structure of bisrosinamide and the simulation temperature on the interfacial activity, in order to evaluate the temperature resistance of bisrosinamide.

[0123] Density distribution and adsorption configuration of bisrosinamide at the oil-water interface, such as Figure 13 and Figure 14 As shown, bisrosinamide molecules mainly aggregate near the oil-water interface. However, as the temperature increases, the distribution width of bisrosinamide molecules near the interface gradually increases from 2.393 nm at 298 K to 2.715 nm at 453 K. It can be seen that the interfacial activity of bisrosinamide molecules gradually decreases with increasing temperature.

[0124] The analysis results of the interfacial adsorption energy of bis(rosinamide) molecules are shown in [the table below]. Figure 15 The average interfacial adsorption energy of bisrosinamide molecules gradually decreases with increasing temperature. In the low-temperature range of 298K to 338K, the interfacial adsorption energy decreases rapidly with increasing temperature. In the high-temperature range of 338K to 453K, the effect of temperature on the interfacial adsorption energy is relatively small, and the decrease in interfacial adsorption energy is slower. Therefore, the analysis of interfacial adsorption energy shows that the temperature resistance of bisrosinamide molecules is poor in the range of 298K to 338K, but in the high-temperature range of 338K to 453K, the temperature resistance of bisrosinamide is good, and the interfacial activity is relatively stable.

[0125] The change of interfacial tension of bisrosinamide molecules with temperature is shown in the figure. Figure 16 The interfacial tension of bisrosinamide molecules also showed a trend of gradually decreasing with increasing temperature. In the low-temperature range of 298K to 338K, the change in interfacial tension was significant. In the high-temperature range of 338K to 453K, the effect of temperature on interfacial tension was relatively small. The results are consistent with the analysis results of interfacial adsorption energy. Bisrosinamide molecules have good temperature resistance in the range of 338K to 453K, and the effect of temperature increase on its interfacial activity is small. However, in the low-temperature region of 298K to 338K, the interfacial activity of bisrosinamide decreases rapidly with increasing temperature.

[0126] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation, characterized in that, Includes the following steps: An initial model of the oil phase / surfactant / aqueous phase simulation system was constructed, and the structure of the initial model was optimized to obtain an optimized model of the oil phase / surfactant / aqueous phase simulation system with minimum energy. Molecular dynamics simulation analysis was performed on the optimized model of the oil-phase / surfactant / aqueous phase simulation system to obtain the simulation results of surfactant molecules at the oil-water interface under different simulation temperatures. The simulation results include the interfacial distribution region, adsorption configuration, interfacial adsorption energy, and interfacial tension of surfactant adsorption at the oil-water interface. Based on the simulation results, the influence of surfactant molecular structure and simulation temperature on interfacial activity was determined to evaluate the temperature resistance of surfactants. The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on the interfacial distribution region is as follows: as the simulated temperature increases, when the surfactant is concentrated near the oil-water interface and the interfacial distribution region tends to be stable, the surfactant has good temperature resistance within the simulated temperature range. The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on interfacial adsorption energy is as follows: as the simulated temperature increases, the lower the decay rate of the surfactant's interfacial adsorption energy, or the more stable the interfacial adsorption energy tends to be, the better the surfactant's temperature resistance within the simulated temperature range. The method for determining the influence of surfactant molecular structure and simulated temperature on interfacial activity based on surface tension is as follows: the lower the decay rate of the surfactant's surface tension as the simulated temperature increases, or the better the surface tension stability, the better the surfactant's temperature resistance within the simulated temperature range. By setting different temperatures and different surfactant molecular weights, the optimal application temperature and optimal dosage of surfactants are accurately evaluated; the simulated temperature ranges from 298K to 453K; the surfactants are oleic acid, oleamide, linoleic acid, linoleamide, rosin acid, rosinamide, or bisrosinamide; The method for obtaining an optimized model of the oil phase / surfactant / aqueous phase simulation system is as follows: Construct initial models for the oil phase, aqueous phase, and surfactant phase; The initial models of the oil phase, aqueous phase, and surfactant were assembled to obtain the initial model of the oil / surfactant / aqueous phase simulation system. The initial model was structurally optimized to obtain an optimized model of the oil / surfactant / aqueous phase simulation system that minimizes energy. The initial oil phase model includes four straight-chain alkanes with different carbon numbers, namely C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C22< / 13 H 28 C 15 H 32 C 18 H 38 and C 21 H 44 .

2. The method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation according to claim 1, characterized in that, In the initial model of the oil phase, C 13 H 28 The number of molecules is 5, C 15 H 32 The number of molecules is 101, C 18 H 38 The number of molecules is 4, C 21 H 44 The number of molecules is 1; The initial model for the oil phase was a cubic lattice model, with a length and width of 5 nm and a density of 0.8 g / cm³. 3 .

3. The method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation according to claim 1, characterized in that, The initial aqueous phase model contains 1500 water molecules; the initial aqueous phase model is a cubic lattice model with a length and width of 5 nm and a density of 1.0 g / cm³. 3 .

4. The method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation according to claim 1, characterized in that, The initial surfactant model consists of 5 molecules; the initial surfactant model is a cubic lattice model with a length and width of 5 nm and a density of 0.8 g / cm³. 3 .

5. The method for evaluating the temperature resistance of surfactants based on molecular dynamics simulation according to claim 1, characterized in that, The method for constructing an initial model of the oil phase / surfactant / aqueous phase simulation system is as follows: An initial model of the oil phase / surfactant / aqueous phase simulation system was constructed by using the initial model of the oil phase as the first layer, the initial model of the surfactant as the second layer, and the initial model of the aqueous phase as the third layer.

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