An evaluation method for adsorption of organic matter by silicon dioxide based on molecular dynamics simulation

Abstract

The application relates to a method for evaluating adsorption of organic matters on silicon dioxide based on molecular dynamics simulation, which comprises the following steps: constructing a hydroxylated silicon dioxide surface model; wherein the density of silanol on the hydroxylated silicon dioxide surface is 0-9.4 OH / nm 2 ; constructing an organic matter molecular model and inserting the organic matter molecular model into the hydroxylated silicon dioxide surface model to obtain an organic matter / silicon dioxide model; performing molecular dynamics simulation on the organic matter / silicon dioxide model; and evaluating the obtained simulation result. The application directly reveals the interaction between different organic matter molecules and different hydroxylated silicon dioxide surfaces at an atomic scale, evaluates the interfacial activity of the formed silicon dioxide surfaces with different hydroxylization degrees and different ionization degrees, and can provide important theoretical guidance for improving the crude oil recovery rate, mineral flotation efficiency, solid surface self-cleaning and other fields.

Description

Technical Field

[0001] This invention belongs to the field of molecular dynamics simulation, and specifically relates to an evaluation method for silica adsorption of organic matter based on molecular dynamics simulation. Background Technology

[0002] Different inherent compositions and structures on mineral surfaces result in different surface properties and wettability. Generally, sandstone reservoirs can be classified into carbonate and silicate types. Different types of minerals within the reservoir exhibit varying characteristics; for example, most sandstone reservoirs currently studied are hydrophilic, while carbonate reservoirs are hydrophobic. Besides the chemical properties of the mineral, the number and arrangement of exposed hydroxyl groups on the mineral surface also influence its hydrophilicity.

[0003] Silica is widely found in nature, including crystalline and amorphous forms. Crystalline silica can be classified into three crystal structures: quartz, tridymite, and cristobalite. The crystal form of silica can change under the influence of temperature, pH, and pressure. Different crystal forms have different surface structures, hydroxylation densities, and even different numbers and densities of negatively charged groups after ionization. However, current methods for analyzing the structure and properties of minerals mainly rely on techniques such as nuclear magnetic resonance (NMR), neutron scattering, atomic force microscopy, and X-ray absorption spectroscopy. These methods do not provide a more direct, atomic-level understanding of the impact of mineral surface properties on adsorption performance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the adsorption performance of silica based on molecular dynamics simulation, so as to study the adsorption performance of mineral surfaces more intuitively.

[0005] To achieve the above objectives, this invention provides an evaluation method for the adsorption of organic matter by silica based on molecular dynamics simulations. This evaluation method includes: A surface model of hydroxylated silica was constructed; the density of silanol on the surface of hydroxylated silica ranged from 0 to 9.4 OH / nm. 2 ; An organic molecule model is constructed and inserted into the hydroxylated silica surface model to obtain an organic / silica model. Molecular dynamics simulations were performed on the organic / silica model, and the simulation results were evaluated.

[0006] Optionally, the hydroxylated silica surface is constructed by a method comprising the following steps: S1, pyrolyzing and hydrating α-quartz cells to obtain Q.2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Mixed surface; S2, the Q 2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Some silanol bonds in the hybrid surface are replaced by SiO − Molecular dynamics simulations of ionized silica surfaces revealed surface silanol densities of 0–9.4 OH / nm. 2 The silica surface in equilibrium.

[0007] Optionally, step S1 includes: cleaving and hydrating the {0 0 1} facet of the first α-quartz expanded cell to obtain Q. 2 Surface; the {2 0 2} facet of the second α-quartz expanded cell is cleaved and hydrated to obtain Q. 3 Surface; for the Q 2 Surface heating and / or Q 3 The silanol groups on the surface undergo partial hydrolysis to obtain Q. 2 / Q 3 Mixed surface; the Q 3 The surface is dehydroxylated to obtain Q. 3 / Q 4 A mixed surface; wherein the first α-quartz expander and the second α-quartz expander have different sizes; Q 4 The density of surface silanol groups is 0; the Q 2 Each silicon atom on the surface is bonded to two silanol groups. Si(OH)2, the Q 3 Each silicon atom on the surface is bonded to two silanol groups. SiOH.

[0008] Optionally, the parameters for molecular dynamics simulation of ionized silica include at least the following: energy minimization using the steepest descent method; NVT ensemble; temperature 300-373 K; Velocity-rescale thermostat for temperature control; Berendsen pressure control; AMBER force field; Group-based electrostatic force application; Atom-based van der Waals force application; time step 1-10 fs; simulation time 10-100 ns; and output of results every 100-1000 steps.

[0009] Optionally, the SiO2 on the ionized silica surface − The density is 0-1.5 / nm. 2 Preferably, the dimensions of the hydroxylated silica surface model include: x-axis 69 Å; y-axis 69 Å; z-axis 100 Å.

[0010] Optionally, the average molecular weight of the organic molecules is 78-800; and / or, the density of the organic molecules is 0.01-0.3 g / cm³. 3 Preferably, the organic molecule includes one or more of dodecane and C5Pe.

[0011] Optionally, the organic molecule model is constructed by a method including the following steps: constructing the three-dimensional structure of the organic molecule using the Avogadro program, and performing geometric optimization on the organic molecule; wherein the parameters of the geometric optimization include: the force field is GAFF; the energy descent adopts the steepest descent method; the electrostatic force adopts the Group Based method; and the van der Waals force adopts the Atom Based method.

[0012] Optionally, the number of organic molecules added to each hydroxylated silica surface is 0.5-3.5 molecules / nm. 2 .

[0013] Optionally, the parameters for molecular dynamics simulation of the organic / silica model include at least: ensemble NVT; temperature 300-373 K; temperature control method Velocity-rescale thermostat; pressure control using the Berendsen method; force field AMBER; electrostatic force applied using Group Based; van der Waals force applied using Atom Based; time step 2-10 fs; simulation time 60-150 ns. Optionally, the method further includes: performing geometric optimization on the organic / silica model before molecular dynamics simulation, wherein the parameters for geometric optimization include at least: force field AMBER; energy minimization using the steepest descent method; electrostatic force applied using the Group Based method; van der Waals force applied using the Atom Based method; and a maximum number of iterations of 40,000-60,000.

[0014] Optionally, the evaluation process includes: calculating the time and density of organic molecules reaching adsorption equilibrium on the surface of hydroxylated silica; and / or determining the adsorption state of organic molecules on the silica surface.

[0015] Through the above technical solution, this invention constructs an organic matter / silica model based on molecular dynamics simulations. This model intuitively reveals the interactions between different organic molecules and silica surfaces with varying degrees of hydroxylation at the atomic scale, and evaluates the interfacial activity of silica surfaces with different degrees of hydroxylation and ionization. Furthermore, by constructing silica surfaces with different degrees of hydroxylation and ionization, the adsorption mechanisms of different surfaces are analyzed, providing important theoretical guidance for improving oil recovery, mineral flotation efficiency, and solid surface self-cleaning.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of an evaluation method for silica adsorption of organic matter based on molecular dynamics simulation provided by the present invention.

[0018] Figure 2 These are silica surface model diagrams with different degrees of hydroxylation provided in some specific embodiments of the present invention.

[0019] Figure 3 These are the adsorption states of dodecane on silica surfaces with different degrees of hydroxylation in some embodiments of the present invention.

[0020] Figure 4 This is a number density distribution diagram of dodecane adsorption equilibrium on silica surfaces with different degrees of hydroxylation in some embodiments of the present invention.

[0021] Figure 5 These are the adsorption states of polycyclic aromatic hydrocarbon molecules C5pe on silica surfaces with different degrees of hydroxylation in some embodiments of the present invention. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] With the rapid development of computer hardware and the continuous optimization of force field parameters, molecular dynamics simulation has become an important method for studying the structure and properties of minerals. It can accurately reproduce the structure of the system, calculate various interactions between atoms in the system (such as Coulomb forces, van der Waals forces, intramolecular covalent bonds, etc.), and study the interactions and adsorption phenomena between organic and inorganic molecules. It can also be combined with theoretical methods in statistical physics to calculate properties such as diffusion coefficient, adsorption rate, free energy change, and vibrational spectrum.

[0024] This invention provides an evaluation method for the adsorption of organic matter by silica based on molecular dynamics simulations. The evaluation method includes: A surface model of hydroxylated silica was constructed; the density of silanol on the surface of hydroxylated silica ranged from 0 to 9.4 OH / nm. 2 ; An organic molecule model is constructed and inserted into the hydroxylated silica surface model to obtain an organic / silica model. Molecular dynamics simulations were performed on the organic / silica model, and the simulation results were evaluated.

[0025] This invention, based on molecular dynamics simulations, constructs an organic matter / silica model, intuitively revealing the interactions between different organic molecules and silica surfaces with varying degrees of hydroxylation at the atomic scale, and evaluating the interfacial activity of silica surfaces with different degrees of hydroxylation and ionization. Furthermore, by constructing silica surfaces with different degrees of hydroxylation and ionization, the adsorption mechanisms of different surfaces are analyzed, providing important theoretical guidance for improving oil recovery, mineral flotation efficiency, and solid surface self-cleaning.

[0026] This invention can construct silica surfaces with different degrees of hydroxylation by expanding, sectioning, and altering the silanol group linkage type and ionization degree using silica unit cells of different crystal forms obtained from mineral crystal structure databases. Simultaneously, it models various organic or inorganic ions required for the simulation system, uses adaptive force fields, and combines empirical and experimental parameters to perform molecular dynamics simulations such as system energy minimization, NPT, and NVT, and analyzes the simulation results.

[0027] In some embodiments of the present invention, the α-quartz cell used is an α-quartz rectangular cell. Different silicon dioxide surfaces can be obtained by expanding the cell and then cutting it.

[0028] In some specific embodiments of the present invention, the initial unit cell of the α-quartz rectangular cell has the following lattice parameters: a = 4.978 Å; b = 4.978 Å; c = 6.948 Å, α = 90°, β = 90°, γ = 120°. The initial unit cell is expanded to meet the simulation requirements.

[0029] In some embodiments of the present invention, the dimensions of the hydroxylated silica surface model include: x-axis 69 Å; y-axis 69 Å; z-axis 100 Å.

[0030] In some embodiments of the present invention, the hydroxylated silica surface is constructed by a method comprising the following steps: S1. The α-quartz cells were lysed and hydrated to obtain Q. 2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Mixed surfaces; S2, the Q 2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Some silanol bonds in the hybrid surface are replaced by SiO − Molecular dynamics simulations of ionized silica surfaces revealed surface silanol densities of 0–9.4 OH / nm. 2 The silica surface in equilibrium.

[0031] In some embodiments of the present invention, step S1 includes: The {0 0 1} facet of the first α-quartz expanded cell was cleaved and hydrated to obtain Q. 2 surface; The {2 0 2} facet of the second α-quartz expanded cell was cleaved and hydrated to obtain Q. 3 surface; For the Q 2 Surface heating and / or Q 3 The silanol groups on the surface undergo partial hydrolysis to obtain Q. 2 / Q 3 Mixed surfaces; Q 3 The surface is dehydroxylated to obtain Q. 3 / Q 4 Mixed surfaces; The first α-quartz expander and the second α-quartz expander have different sizes; Q 4The density of surface silanol groups is 0; The Q 2 Each silicon atom on the surface is bonded to two silanol groups. Si(OH)2, the Q 3 Each silicon atom on the surface is bonded to two silanol groups. SiOH.

[0032] In the above steps, Q 2 / Q 3 The creation of a hybrid surface can be achieved by adjusting Q. 2 It can be obtained by surface heating (removing some hydroxyl groups during the simulation process), or by using Q. 3 The surface was partially hydrolyzed (some hydroxyl groups were added during the simulation process) to obtain the product.

[0033] The above steps were used to construct silica surfaces with different silanol densities to observe the adsorption state of different organic molecules on silica surfaces with different degrees of hydroxylation, as well as the time to reach adsorption equilibrium.

[0034] In some embodiments of the present invention, Q 2 Surface, Q 2 / Q 3 Hybrid surfaces, Q 3 Surface, Q 3 / Q 4 The hydroxylation density of the mixed surfaces decreases sequentially. For example, in some specific embodiments of the present invention, the hydroxylation density of the silica surface can be 9.4 / nm. 2 6.9 / nm 2 4.7 / nm 2 2.4 / nm 2 And 0.

[0035] In some embodiments of the present invention, the parameters for molecular dynamics simulation of ionized silica include at least: energy minimization using the steepest descent method; NVT ensemble; temperature of 300-373 K; temperature control method of Velocity-rescale thermostat; pressure control using the Berendsen method; force field of AMBER; electrostatic force applied using Group Based; van der Waals force applied using Atom Based; time step of 1-10 fs; simulation time of 10-100 ns; and output of results every 100-1000 steps.

[0036] In some embodiments of the present invention, the SiO2 on the ionized silicon dioxide surface − The density is 0-1.5 / nm. 2 .

[0037] In some embodiments of the present invention, the average molecular weight of the organic molecules can be 78-800. The organic matter used in the present invention to evaluate the adsorption properties of silica surfaces can be a liquid organic matter, preferably an organic molecule with C6 or higher molecular weight.

[0038] In some embodiments of the present invention, the density of the organic molecules can be 0.01-0.3 g / cm³. 3 .

[0039] In some preferred embodiments of the present invention, the organic molecule comprises one or more of dodecane and C5Pe. C5Pe is constructed based on N-(1-hexylheptyl)-N′-(5-carboxypentyl)perylene-3,4,9,10-tetracarboxybisimide (C5Pe) proposed by Nordgård and Sjöblom et al., and its molecular structure includes a hydrophilic carboxyl chain and a dinaphthalene-containing planar structure.

[0040] In some embodiments of the present invention, the organic molecule model is constructed by a method comprising the following steps: The Avogadro program was used to construct the three-dimensional structure of organic molecules and to perform geometric optimization on the organic molecules. The parameters for geometry optimization include: a GAFF force field; the steepest descent method for energy descent; a group-based method for electrostatic force; and an atom-based method for van der Waals force. In some specific embodiments of the present invention, during geometry optimization, the energy of dodecane molecules can be 34496.41 Kcal / mol, and the energy of C5Pe can be 48821.77 Kcal / mol.

[0041] In some embodiments of the present invention, the number of organic molecules added to each hydroxylated silica surface can be 0.5-3.5 molecules / nm. 2 For example, in some specific embodiments of the present invention, the amount of dodecane molecules added can be 1.89 molecules / nm. 2 The amount of C5Pe added can be 1.05 per nm. 2 .

[0042] In some embodiments of the present invention, the method further includes: performing geometric optimization on the organic / silica model before performing molecular dynamics simulation on the organic / silica model, wherein the parameters of the geometric optimization include at least: the force field is AMBER; energy is minimized by the steepest descent method; Energy is 1000 KJ / mol; the electrostatic force is performed using the Group-Based method; the van der Waals force is performed using the Atom-based method; and the maximum number of iterations is 40,000-60,000.

[0043] In some embodiments of the present invention, the parameters for molecular dynamics simulation of the organic / silica model include at least: an ensemble of NVT; a temperature of 300-373 K; a Velocity-rescale thermostat for temperature control; pressure control using the Berendsen method; a force field of AMBER; electrostatic forces applied using Group Based; van der Waals forces applied using Atom Based; a time step of 2-10 fs; and a simulation time of 60-150 ns. For example, in some specific embodiments of the present invention, the time step is 2 fs and the simulation time is 60 ns.

[0044] In this invention, the box used for simulation construction in the process of geometric optimization and molecular dynamics simulation of the organic / silica model adopts a periodic boundary. The box has a periodic boundary in the xyz direction. Since the periodic boundary conditions must be considered in the simulation process, in order to reduce the influence of periodicity in the z direction on the system, the z-axis value is appropriately increased in the energy minimization and simulation process.

[0045] In some embodiments of the present invention, the evaluation process includes: calculating the time and density of organic molecules reaching adsorption equilibrium on the surface of hydroxylated silica; and / or determining the adsorption state of organic molecules on the silica surface.

[0046] This invention employs molecular dynamics simulation to study the adsorption behavior of various molecules on different silica surfaces in a more intuitive, convenient, and efficient manner at the molecular level. Optimal software combinations are selected for molecular dynamics simulation. Professional software such as GROMACS, Material Studio, and VMD are used, with a focus on accuracy and stability in modeling, calculation, and analysis to ensure the accuracy and efficiency of the molecular dynamics simulation results. Through a more practical and adaptable combination of software, force fields, methods, and information, this invention constructs silica structures with different crystal morphologies, silanol group densities, and ionization degrees using molecular dynamics simulation. The structure, charge properties, interfacial activity, and adsorption of water and organic matter on different silica surfaces are studied at the nanoscale, providing important theoretical guidance for improving oil recovery, mineral flotation efficiency, and solid surface self-cleaning.

[0047] The present invention will be further described in detail below through examples, but the present invention is not limited thereto.

[0048] Example 1 This embodiment illustrates the method for constructing a silica surface model according to the present invention, which includes the following steps: S1. Obtain the α-quartz rectangular unit cell model with the following lattice parameters: a=4.978 Å; b=4.978 Å; c=6.948 Å, α=90°, β=90°, γ=120°; S2. Establish silica surfaces with different degrees of hydroxylation.

[0049] Specifically, step S2 includes: 1) The {0 0 1} facet of the α-quartz expanded cell (7x4x3) was cleaved and hydrated to obtain Q. 2 Surface, making Q 2 Each silicon atom on the surface is bonded to two silanol groups. Si(OH)2, Q obtained 2 The density of the surface silanol is 9.4 OH / nm. 2 ; 2) The {2 0 2} facets of the α-quartz expanded cell (4x7x2) were cleaved and hydrated to obtain Q. 3 Surface, making Q 3 Each silicon atom on the surface is bonded to two silanol groups. SiOH, Q 3 The density of the surface silanol is 4.7 OH / nm. 2 ; 3) Q 3 The surface silanol undergoes partial hydrolysis (addition of hydroxyl groups) to obtain Q. 2 / Q 3 A hybrid surface with a silanol density of 6.9 OH / nm. 2 ; 4) Q 3 The surface is dehydroxylated to obtain Q. 3 / Q 4 A mixed surface with a silanol density of 2.4 OH / nm. 2 ; 5) Through high temperature Q 3 The complete condensation and energy minimization of surface silanol groups (with some Si-O bonds stretched by 10%) constructs Q. 4 Surface, Q 4 The density of the silanol on the surface is 0.

[0050] The parameters for molecular dynamics simulation of ionized silica include at least the following: energy minimization using the steepest descent method; NVT ensemble; temperature of 300 K; temperature control method of Velocity-rescale thermostat; pressure control using the Berendsen method; force field of AMBER; electrostatic force applied using Group Based; van der Waals force applied using Atom Based; time step of 1 fs; simulation time of 10 ns; and output of results every 100 steps.

[0051] Figure 2 In the middle figure, a and e represent hydroxylation densities of 9.4 OH / nm, respectively. 2 6.9 OH / nm 2 4.7 OH / nm 2 2.4OH / nm 2 A model diagram of the silicon surface with 0. Figure a shows the hydroxylation density at 9.4 OH / nm. 2 The silicon surface, Q 2 Crystal form; Figure b shows the hydroxylation density at 6.9 OH / nm. 2 The silicon surface, Q 2 / Q 3 Mixed crystal form; Figure c shows a hydroxylation density of 4.7 OH / nm. 2 The silicon surface, Q 3 Crystal form; Figure d shows the hydroxylation density at 2.4 OH / nm. 2 The silicon surface, Q 3 / Q 4 Mixed crystal form; Figure e shows the silicon facet with a hydroxylation density of 0, which is Q. 4 Crystal form.

[0052] Example 2 This embodiment illustrates a method for evaluating the adsorption performance of dodecane molecules on silica surfaces with different degrees of hydroxylation. The method includes the following steps: (1) Construct a dodecane molecular model using Avogadro and optimize the structure of the constructed dodecane molecular model. Obtain the topology file of the optimized structure using AcPyPE. (2) The size of the silica surface model box in the z direction obtained in Example 1 was adjusted to 5 nm. Dodecane molecule models were added to the silica surface model by Gromacs. 90 dodecane molecules were added to the silica surface systems with different degrees of hydroxylation. Then the size of the silica solid surface box in the z direction was adjusted to 15 nm to obtain the dodecane / silica model. (3) The energy of the dodecane / silica model was minimized using the steepest descent method, and molecular dynamics simulation was performed on the resulting geometrically optimized structure. The molecular dynamics simulation used a canonical (NVT) ensemble. To avoid violent molecular thermal motion, the simulation temperature was set to 200 K, and the Velocity rescale method was used for the heat bath. The pressure control was performed using the Berendsen method. The force field was AMBER. The electrostatic force was applied using Group Based. The van der Waals force was applied using Atom Based. The step size was set to 1 fs, and the simulation time was 60 ns to complete the adsorption simulation process.

[0053] The parameters for energy minimization include: the force field is AMBER; energy minimization is performed using the steepest descent method; Energy is 1000 KJ / mol; the electrostatic force uses the Group Based method; the van der Waals force uses the Atom Based method; and the maximum number of iterations is 50000.

[0054] The potential function used in this example is: , where r i The position of atom i. E For the total potential energy, m i E represents the atomic mass of atom i. total =E bonded +E non-bonded E total E is the total energy of the system. bonded For covalent bond energy, E non-bonded This is a non-covalent bond energy. E bonded =E bond +E angle +E torsion E non-bonded =E electrostatic +E vanderWaals , of which E bonded E represents the potential energy generated by the bond length deformation between two bonded atoms. angle E is the potential energy of the angular motion between the three bonded atoms that form two consecutive chemical bonds. torsion It represents the potential energy generated in a molecule due to the twisting of four atoms.

[0055] After the simulation was completed, the adsorption state of dodecane on the silica surface at different times was observed using GROMACS and VMD software. The final structure file and trajectory file were optimized and processed, and the required simulation snapshots and trajectories were saved. The time and state of adsorption equilibrium were calculated and determined using GROMACS and VMD software.

[0056] Figure 3This is a top view of the organic matter / silica surface at which dodecane molecules reach adsorption equilibrium on silica surfaces with different degrees of hydroxylation in this embodiment. According to... Figure 3 It can be observed that the adsorption state of dodecane molecules as oil phase on silica surfaces with different degrees of hydroxylation is different. Dodecane molecules are distributed in layers on the silica surface and are not completely spread on the silica surface.

[0057] Figure 4 This is a number density distribution diagram of dodecane molecules reaching adsorption equilibrium on silica surfaces with different degrees of hydroxylation in this embodiment. Figure 4 It can be seen that in Si-OH 9.4 / nm 2 Si-OH 6.9 / nm 2 Si-OH 4.7 / nm 2 Si-OH 2.4 / nm 2 In the five systems, Si-OH, the z-coordinates corresponding to the peak values ​​of the adsorption curves are 2.55 nm, 3.15 nm, 3.15 nm, 2.55 nm, and 3.15 nm, respectively. The z-coordinates corresponding to the silica surface in these five systems are 1.95 nm, 2.55 nm, 2.55 nm, 1.95 nm, and 2.55 nm, respectively. Therefore, the distances from the first adsorption peak to the surface are 0.60 nm, 0.60 nm, 0.60 nm, 0.60 nm, and 0.60 nm, respectively.

[0058] The possible reason why the hydroxyl density of silica affects the adsorption state of dodecane is that the interaction between dodecane molecules and the silicon surface mainly occurs between the silanol groups attached to silicon atoms. The interaction between dodecane molecules and the silica surface is primarily a hydrophobic effect, with Si-OH 6.9 / nm. 2 Si-OH 4.7 / nm 2 Si-OH 2.4 / nm 2 In the Si-OH system, the interaction strength between dodecane molecules and the silica surface increases with increasing hydrophobicity; however, for Si-OH, the interaction strength is 9.4 / nm. 2 In this system, because each surface silicon atom is connected to two silanol groups, the hydrogen bonds formed between the silanol groups enhance the interaction between the silicon surface and the dodecane molecules.

[0059] Example 4 This embodiment illustrates a method for evaluating the adsorption performance of organic C5Pe asphaltenes molecules on silica surfaces with different degrees of hydroxylation. The method includes the following steps: (1) A polycyclic aromatic hydrocarbon C5Pe molecular model was constructed using Avogadro, and the structure of the constructed C5Pe molecular model was optimized. The topology file of the optimized structure was obtained using Acpype. The size of the silica solid surface model box in the z direction was adjusted to 9 nm. Asphaltene C5Pe molecular model was added to the silica surface model using Gromacs. 50 C5Pe asphaltene molecules were added to five silica surface systems with different degrees of hydroxylation. In the initial prototype simulation, the asphaltene molecules were randomly distributed. Then the size of the silica solid surface box in the z direction was adjusted to 15 nm to obtain the C5Pe / silica model. (2) The energy of the C5Pe / silica model was minimized and the resulting geometrically optimized structure was subjected to molecular dynamics simulation. The canonical (NVT) ensemble was selected, the simulation temperature was set to 300 K, and the Velocity rescale method was used for the heat bath. The pressure control was carried out using the Berendsen method. The force field was AMBER. The electrostatic force was applied using Group Based. The van der Waals force was applied using Atom Based. The step size was set to 1 fs and the simulation time was 60 ns to complete the adsorption simulation process.

[0060] The parameters for geometric optimization of the C5Pe / silica model include: force field is AMBER; energy is minimized using the steepest descent method; Energy is 1000 kJ / mol; electrostatic force is performed using the group-based method; van der Waals force is performed using the atom-based method; and the maximum number of iterations is 50,000.

[0061] During energy minimization and throughout the NVT simulation, the position of the silica plane is restricted, except for surface atoms.

[0062] After the simulation was completed, the adsorption state of C5Pe asphaltenes molecules on the silica surface at different times was observed using GROMACS and VMD software. The final structure and trajectory files were optimized and processed, and the required simulation snapshots and trajectories were saved. The time and state of adsorption equilibrium were calculated and determined using GROMACS and VMD software. VMD was used as a visualization tool to extract the molecular structure graphics of the system.

[0063] The potential function used in this example is , where r i The position of atom i. E For the total potential energy, m i E represents the atomic mass of atom i. total =E bonded +E non-bonded E total E is the total energy of the system. bondedFor covalent bond energy, E non-bonded This is a non-covalent bond energy. E bonded =E bond +E angle +E torsion E non-bonded =E electrostatic +E vanderWaals , of which E bonded E represents the potential energy generated by the bond length deformation between two bonded atoms. angle E is the potential energy of the angular motion between the three bonded atoms that form two consecutive chemical bonds. torsion It represents the potential energy generated in a molecule due to the twisting of four atoms.

[0064] Figure 5 This embodiment shows the adsorption states of the polycyclic aromatic hydrocarbon molecule C5pe on silica surfaces at different degrees of hydroxylation. Figure a shows the adsorption state of C5pe at a hydroxylation density of 9.4 OH / nm. 2 Figure b shows the adsorption state of C5pe on the silicon surface; Figure b shows the adsorption state of C5pe on the silicon surface with a hydroxylation density of 6.9 OH / nm. 2 The adsorption state of C5pe on the silicon surface; Figure c shows the adsorption state of C5pe at a hydroxylation density of 4.7 OH / nm. 2 The adsorption state of C5pe on the silicon surface; Figure d shows the adsorption state of C5pe at a hydroxylation density of 2.4 OH / nm. 2 Figure e shows the adsorption state of C5pe on a silicon surface with a hydroxylation density of 0.

[0065] according to Figure 5 It can be observed that C5Pe molecules exhibit aggregation and adsorption behavior on the silica surface in all systems. During adsorption, the hydrophilic -COOH terminal of the asphaltene C5Pe molecules and the hydroxylation sites (i.e., silanol groups) on the silica surface interact. Due to Q... 2 Crystal form and Q 3 Differences in crystal form, Si-OH 9.4 / nm 2 The system has a high density of silanol groups, and hydrogen bonding exists between silanol groups on the surface, resulting in C5Pe molecules having a Si-OH density of 9.4 / nm. 2 The adsorption capacity of the SiO2 surface in this system is not as good as that of Si-OH (6.9 / nm). 2 System. Q 2 Q 3 In the mixed crystal system, the adsorption of asphaltene molecules on the silica surface is greater than Q. 3 Crystalline surface. Si-OH 4.7 / nm 2 and Si-OH 2.4 / nm 2In this system, each silicon atom is bonded to a silanol group (≡Si(OH)). The difference between the systems lies in the varying density of silanol groups on the SiO2 surface, leading to different hydrophobicities. As the hydrophobicity of the SiO2 surface increases, the hydrogen bonding interaction between asphaltenes C5Pe molecules and the SiO2 surface decreases, weakening the adsorption. For the Si-OH system, the adsorption of asphaltenes molecules mainly depends on the attraction between the hydrophobic aromatic ring and the SiO2 surface. This attraction is greater than the repulsion between the -COOH group in the asphaltenes and the surface, resulting in a lower adsorption degree compared to the Si-OH system (2.4 / nm). 2 The system has been strengthened.

[0066] In summary, this invention, based on molecular dynamics simulations, constructs an organic matter / silica model, intuitively revealing the interactions between different organic molecules and silica surfaces with varying degrees of hydroxylation at the atomic scale, and evaluating the adsorption characteristics of the formed interfaces. Furthermore, the construction of silica surfaces with different degrees of hydroxylation and ionization can provide important theoretical guidance for improving oil recovery, mineral flotation efficiency, and solid surface self-cleaning.

[0067] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0069] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for evaluating the adsorption of organic matter by silica based on molecular dynamics simulations, characterized in that, The evaluation method includes: A surface model of hydroxylated silica was constructed; the density of silanol on the surface of hydroxylated silica ranged from 0 to 9.4 OH / nm. 2 ; An organic molecule model is constructed and inserted into the hydroxylated silica surface model to obtain an organic / silica model. Molecular dynamics simulations were performed on the organic / silica model, and the simulation results were evaluated.

2. The evaluation method according to claim 1, wherein, The hydroxylated silica surface is constructed by a method comprising the following steps: S1. The α-quartz cells were lysed and hydrated to obtain Q. 2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Mixed surfaces; S2, the Q 2 Surface, Q 3 Surface, Q 2 / Q 3 Hybrid surfaces and Q 3 / Q 4 Some silanol bonds in the hybrid surface are replaced by SiO − Molecular dynamics simulations of ionized silica surfaces revealed surface silanol densities of 0–9.4 OH / nm. 2 The silica surface in equilibrium.

3. The evaluation method according to claim 2, wherein, Step S1 includes: The {0 0 1} facet of the first α-quartz expanded cell was cleaved and hydrated to obtain Q. 2 surface; The {2 0 2} facet of the second α-quartz expanded cell was cleaved and hydrated to obtain Q. 3 surface; For the Q 2 Surface heating and / or Q 3 The silanol groups on the surface undergo partial hydrolysis to obtain Q. 2 / Q 3 Mixed surfaces; Q 3 The surface is dehydroxylated to obtain Q. 3 / Q 4 Mixed surfaces; The first α-quartz expander and the second α-quartz expander have different sizes; Q 4 The density of surface silanol groups is 0; the Q 2 Each silicon atom on the surface is bonded to two silanol groups. Si(OH)2, the Q 3 Each silicon atom on the surface is bonded to two silanol groups. SiOH.

4. The evaluation method according to claim 2, wherein, The parameters for molecular dynamics simulation of ionized silica include at least the following: energy minimization using the steepest descent method; NVT ensemble; temperature 300-373 K; temperature control method using a Velocity-rescale thermotubation; pressure control using the Berendsen method; force field using AMBER; electrostatic force applied using Group-Based; van der Waals force applied using Atom-based; time step 1-10 fs; simulation time 10-100 ns; and outputting results every 100-1000 steps.

5. The evaluation method according to claim 2, wherein, SiO on the ionized silica surface − The density is 0-1.5 / nm. 2 ; Preferably, the dimensions of the hydroxylated silica surface model include: x-axis 69 Å; y-axis 69 Å; z-axis 100 Å.

6. The evaluation method according to claim 1, wherein, The average molecular weight of the organic molecules is 78-800; and / or, The density of the organic molecules is 0.01-0.3 g / cm³. 3 ; Preferably, the organic molecule includes one or more of dodecane and C5Pe.

7. The evaluation method according to claim 1, wherein, The organic molecule model is constructed using a method comprising the following steps: The Avogadro program was used to construct the three-dimensional structure of organic molecules and to perform geometric optimization on the organic molecules. The parameters for geometric optimization include: the force field is GAFF; the energy descent uses the steepest descent method; the electrostatic force uses the Group-Based method; and the van der Waals force uses the Atom-based method.

8. The evaluation method according to claim 1, wherein, The number of organic molecules added to each hydroxylated silica surface is 0.5-3.5 per nm. 2 .

9. The evaluation method according to claim 1, wherein, The parameters for molecular dynamics simulation of the organic / silica model include at least the following: ensemble NVT; temperature 300-373 K; temperature control method Velocity-rescale thermostat; pressure control using the Berendsen method; force field AMBER; electrostatic force applied using Group Based; van der Waals force applied using Atom Based; time step 2-10 fs; simulation time 60-150 ns. Optionally, the method further includes: performing geometric optimization on the organic / silica model before performing molecular dynamics simulation on the organic / silica model, wherein the parameters of the geometric optimization include at least: the force field is AMBER; energy is minimized by the steepest descent method; the electrostatic force is performed by the Group Based method; the van der Waals force is performed by the Atom Based method; and the maximum number of iterations is 40,000-60,000.

10. The evaluation method according to claim 1, wherein, The evaluation process includes: calculating the time and density of organic molecules reaching adsorption equilibrium on the hydroxylated silica surface; and / or, Determine the adsorption state of organic molecules on the silica surface.

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