A method for screening metal single-atom catalysts for the hydrochlorination of acetylene with nitrogen-containing functional groups

Abstract

The present application belongs to the technical field of catalyst calculation design and screening, in particular to a screening method for metal monatomic catalysts with nitrogen-containing functional groups for acetylene hydrochlorination reaction, comprising the following steps: constructing a single-atom catalyst candidate structure model with nitrogen-containing functional groups coordinated with metal chlorides; using first-principle calculation method to optimize the geometric structure of all candidate structure models, obtaining the ground state stable configuration, calculating the binding energy, and performing preliminary stability evaluation; correcting the free energy of the optimized stable configuration, calculating the thermodynamic binding energy; obtaining the influence law of temperature and chlorine chemical potential on the stability of active center structure; screening out the functional group-metal chloride coordination configuration with negative binding energy under the target reaction conditions as the stable candidate active site. The present application provides a theoretical basis and prediction method for rationally designing high-stability acetylene hydrochlorination reaction catalyst active sites, which can significantly reduce the trial-and-error cost and research and development cycle of catalyst development.

Description

Technical Field

[0001] This invention belongs to the field of catalyst computational design and screening technology, specifically a method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction. Background Technology

[0002] The acetylene hydrochlorination reaction is a crucial step in the industrial production of vinyl chloride. Traditionally, this reaction uses mercury-based catalysts, but the loss of the HgCl2 active component from mercury-based catalysts has led to a series of environmental problems and health hazards, prompting researchers to develop more environmentally friendly and sustainable mercury-free catalysts. Carbon-supported single-atom metal catalysts are considered to be mercury-free catalysts with application potential. However, under reaction conditions, single-atom metal active sites are prone to reduction sintering or overchlorination, leading to rapid catalyst deactivation. Existing research shows that the chlorine coordination of the metal single atom is crucial for maintaining the active metal cation and inhibiting the reduction sintering of the metal active sites. By rationally controlling the coordination environment between the metal and chlorine, the activity and stability of the catalyst can be effectively improved.

[0003] Functional groups on the surface of carbon supports play an important role in enhancing the stability of metal chlorides on the carbon support surface. Literature reports that nitrogen species in nitrogen-modified activated carbon can effectively anchor Au. n+ Thus stabilizing Au 3+ Besides catalysts, catalysts with a large number of nitrogen-containing functional groups can effectively stabilize metals such as Fe, Ag, and Pd that are prone to agglomeration and deactivation. However, the diversity of functional groups on the surface of carbon supports makes it difficult to analyze these nitrogen-containing functional groups used for metal stabilization. Furthermore, existing technologies suffer from the following drawbacks: First, due to the diversity of functional groups on the surface of carbon supports, the specific types of nitrogen-containing functional groups used for metal stabilization and their respective stabilizing effects on metal chlorides are difficult to analyze experimentally, lacking a systematic theoretical understanding. Second, the stability of active sites depends not only on the internal coordination environment between the functional group and the metal chloride but also on external factors such as temperature and reaction atmosphere under actual reaction conditions. Existing research methods fail to integrate the internal coordination environment and external reaction conditions into a unified framework for comprehensive analysis. Third, among numerous possible combinations of functional group types, metal types, and chlorine coordination numbers, there is a lack of efficient theoretical screening methods to quickly identify the thermodynamically most stable active site configuration, resulting in high trial-and-error costs and long development cycles in experimental research.

[0004] Accurate theoretical simulations are crucial for describing the metal-support interactions between single-atom species and functional groups on the surface of carbon supports. Therefore, there is an urgent need to design a screening method for nitrogen-containing functional group-stabilized single-atom metal catalysts for the acetylene hydrochlorination reaction to address the aforementioned technical challenges. Summary of the Invention

[0005] The purpose of this invention is to provide a method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction. By constructing a "functional group-metal chloride" coordination structure model and combining it with first-principles calculations, the influence of different nitrogen-containing functional groups on the stability of metal chlorides is systematically studied, so as to achieve precise control of nitrogen-containing functional groups at the edge of carbon support.

[0006] The technical solution adopted by this invention to achieve the above objectives is: a method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction, comprising the following steps:

[0007] 1) Construct candidate structural models for single-atom catalysts with nitrogen-containing functional groups coordinated with metal chlorides;

[0008] 2) Using first-principles calculations, the geometric structure of all candidate structural models obtained in step 1) is optimized to obtain ground-state stable configurations, and the binding energy is calculated to conduct a preliminary stability assessment.

[0009] 3) Perform free energy correction on the optimized ground-state stable configuration and calculate the thermodynamic binding energy of the coordination structure of the functional group-metal chloride under the target reaction conditions;

[0010] 4) Examine and plot the relationship between thermodynamic binding energy and temperature and the relationship between temperature and chlorination potential to obtain the influence of temperature and chlorination potential on the structural stability of the active center.

[0011] 5) Based on the thermodynamic binding energy data in steps 3) and 4), functional group-metal chloride coordination configurations with negative binding energies and absolute values ​​that meet the threshold size under the target acetylene hydrochlorination reaction conditions are selected as stable candidate active sites.

[0012] Step 1) includes the following steps:

[0013] 1-1) Provide a carbon support having nitrogen-containing functional groups, wherein the carbon support is graphene and the nitrogen-containing functional groups are located at the edge of the graphene.

[0014] 1-2) Provides metal chloride active centers, in the form of M is a transition metal selected from at least one of Au, Ag, Cu, Fe, Ni, Ru, Rh, Pd, Ir, and Pt, and x is the number of chlorine atoms coordinated with M. The value of x ranges from 0 to 5, representing six coordination states from non-chlorine coordination to pentachlorine coordination.

[0015] 1-3) Connect the metal atoms in the active center of the metal chloride with the nitrogen atoms in the nitrogen-containing functional group through chemical bonds. For each type of functional group, each type of metal, and each combination of chlorine coordination number x, construct an atomic-level initial coordination structure model one by one to form a candidate structure model library containing multiple functional group-metal chloride combinations.

[0016] The nitrogen-containing functional groups are selected from the following types: , , , , , , , .

[0017] Step 2) includes the following steps:

[0018] 2-1) Using a first-principles calculation algorithm, set the calculation parameters and perform geometric optimization on each of the constructed initial coordination structure models to relax each structure to the energy minimum point on its potential energy surface, thereby obtaining the stable configuration of each structure in the ground state.

[0019] 2-2) For each stable configuration obtained, calculate the total energy of the system. And calculate the energy of the corresponding nitrogen-containing functional group carrier separately. precursor Energy of coordination compounds as well as Energy of a single Cl atom in a molecule Calculate the binding energy of this coordination configuration using the following formula. :

[0020]

[0021] in, This represents the total energy of the entire system after the metal chloride is combined with the functional group carrier. This represents the energy required for the nitrogen-containing functional group support without metal loading to exist alone. Hexachloro coordination metal precursor The energy when it exists alone, x is the number of chlorine atoms actually coordinated with metal M in the current configuration, and (6-x) represents the number of chlorine atoms dissociated from the hexachlorine precursor. Chlorine molecules The average energy distributed to a single Cl atom;

[0022] 2-3) For all calculated results Sort the values ​​in ascending order, and based on the sorting results, initially select the binding energies. Configurations with negative values.

[0023] In step 2-1), setting the calculation parameters specifically involves:

[0024] The electron exchange correlation is described using a PBE exchange-correlation functional under the generalized gradient approximation. The plane wave cutoff energy is set to 400 eV. A 2×1×1 MP grid is used for the Brillouin zone integration, and the self-consistent field energy convergence threshold is set to 1×10⁻. 5 eV, with the force convergence criterion set to 0.02 eV / Å.

[0025] Step 3) includes the following steps:

[0026] 3-1) For stable configurations with negative binding energy after optimization, vibration frequency is calculated under the same calculation parameter settings as the first-principles calculation algorithm. By analyzing all vibration modes of each configuration, its simple harmonic vibration frequency and vibration entropy are obtained.

[0027] 3-2) After obtaining the vibrational frequency data, the Gibbs free energy of each configuration at different temperature points in the temperature range of 0 K to 1073.15 K was calculated using statistical thermodynamics.

[0028] The Gibbs free energy includes: electronic ground state energy, zero-point vibrational energy, vibrational internal energy, and temperature correction term for vibrational entropy;

[0029] 3-3) For each configuration obtained at each temperature point, extract the total Gibbs free energy of the system. Gibbs free energy of corresponding nitrogen-containing functional group supports precursor Gibbs free energy as well as Gibbs free energy of a single Cl atom in a molecule Calculate the thermodynamic binding energy at different temperatures using the following formula. :

[0030]

[0031] in, This represents the Gibbs free energy of the entire system at a specified temperature after a metal chloride is supported on a functional group carrier. The value represents the Gibbs free energy of the nitrogen-containing functional group support without metal loading at a specified temperature. Hexachloro coordination metal precursor The Gibbs free energy at a specified temperature, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. Chlorine molecules Gibbs free energy of a single Cl atom at a specified temperature; The more negative the value, the higher the thermodynamic stability of the coordination configuration at that temperature.

[0032] Step 4) includes the following steps:

[0033] 4-1) Selecting the chlorination potential The reference states are respectively adopted The energies of the molecules and HCl molecules are used as a reference. The range of values ​​is calibrated, rich Atmosphere Corresponding Reference values ​​are taken from Molecular chemical potential, corresponding to HCl-rich atmosphere The reference value is taken from the chemical potential of the HCl molecule, thus determining the range of the chlorination potential to be examined from HCl-rich atmospheres to HCl-rich atmospheres. A continuous range of atmosphere;

[0034] 4-2) Within a defined range of chlorination potentials, for each configuration, calculate the chemical binding energy at different chlorination potentials using the following formula. :

[0035]

[0036] in, The chemical potential of the entire system after a metal chloride is supported on a functional group carrier is denoted as . The chemical potential of the nitrogen-containing functional group support without metal loading. Hexachloro coordination metal precursor The chemical potential, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. For The chemical potential of a single Cl atom as indicated by a molecule or an HCl molecule;

[0037] 4-3) By plotting the relationship between thermodynamic binding energy and chemical potential binding energy as a function of external conditions, the influence of the reaction environment on the structural stability of the active center can be revealed.

[0038] Step 4-3) specifically involves:

[0039] With temperature as the x-axis, thermodynamic binding energy Plot the values ​​of x on different chlorine coordination numbers on supports with different functional groups, using x as the ordinate. configuration A heatmap showing the relationship between temperature and stability, with temperatures ranging from 0 K to 1073.15 K, reflects the stability trend across the entire range from room temperature to the experimental thermal activation temperature; simultaneously... The horizontal axis represents the chemical potential and binding energy. Plot the values ​​of x, with y as the vertical axis, for different chlorine coordination numbers at a fixed reaction temperature. configuration The graph shows the relationship between the chemical potential of chlorination and the reaction atmosphere, reflecting the influence of the reaction atmosphere on the stable configuration of the active center.

[0040] Step 5) includes the following steps:

[0041] 5-1) At the target acetylene hydrochlorination reaction temperature, extract the thermodynamic binding energy of each functional group-metal chloride coordination configuration at each chlorine coordination number x. or chemical potential binding energy The value;

[0042] 5-2) With binding energy or The negative value is used as the basic criterion for thermodynamic stability. By comparing the relative magnitudes of the binding energies of different chlorine coordination number configurations on the same functional group of the same metal, the chlorine coordination number configuration with the largest negative binding energy in each combination is selected as the most stable coordination form of the functional group-metal combination under the reaction conditions.

[0043] 5-3) The most stable coordination forms of each functional group-metal combination screened out are compared horizontally, and the combinations whose absolute value of binding energy meets the threshold value are selected as stable candidate active sites for the acetylene hydrochlorination reaction.

[0044] The metals of the stable candidate active sites are Group IB metals;

[0045] The Group IB metal is Au, Ag, or Cu, and its most stable chlorine coordination form is: or ;

[0046] The screened stable active site configuration is composed of carbon support surface Stable functional groups Coordination structure; in a reaction atmosphere with HCl as the chlorine source, this The coordination structure undergoes a configurational transformation, changing from a trichlorocoagulation state to... The monochlorinated coordination state exists stably in this state.

[0047] The present invention has the following beneficial effects and advantages:

[0048] 1. This invention utilizes first-principles calculations and high-throughput computation to investigate the ability of edge nitrogen functional groups that may exist on carbon supports to stabilize different metal chlorides. It proposes a single-atom coordination configuration of "functional group-metal chloride" and reveals the influence of functional group type, metal type and chlorine coordination number on the stability of active centers. This provides a theoretical basis and prediction method for the rational design of active sites of highly stable acetylene hydrochlorination catalysts under reaction conditions.

[0049] 2. In evaluating the stability of active centers, this invention not only considers the internal coordination environment between functional group type and metal chloride, but also incorporates the temperature effect under actual reaction conditions and the external environment of chlorination potential into a comprehensive consideration. By drawing heat maps of thermodynamic binding energy with temperature and graphs of its relationship with chlorination potential, the influence of environmental conditions on the structural stability of active centers is intuitively revealed, making up for the shortcomings of existing research methods that fail to comprehensively consider the internal coordination environment and external reaction conditions.

[0050] 3. The method of this invention provides direct theoretical guidance for the rational design and screening of catalyst active sites through theoretical calculations, and for the targeted synthesis of carbon supports with specific edge chemistry to stabilize metal catalysts. This significantly reduces the R&D costs associated with traditional experimental trial-and-error methods, shortens the R&D cycle, and provides an efficient theoretical prediction tool for the development of mercury-free catalysts for the acetylene hydrochlorination reaction. Attached Figure Description

[0051] Figure 1 The present invention provides a comparison diagram of the binding energies of different metals at the anchoring points of the -pyro functional groups on the edge of graphene.

[0052] Figure 2 The present invention provides a binding energy diagram of AuClx anchored by different functional groups at the edge of graphene;

[0053] Figure 3 The present invention provides a Gibbs binding energy thermal map of AuClx at different temperatures, using different functional groups at the edge of graphene as anchoring points.

[0054] Figure 4 The present invention provides a trend diagram of the binding energy variation of AuClx anchored by the -NH101 functional group at the edge of graphene under different chemical potentials.

[0055] Figure 5 The overall flowchart of the catalyst screening method of the present invention. Detailed Implementation

[0056] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific implementation methods of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0057] This invention provides a method for designing nitrogen-containing functional group-stabilized single-atom metal catalysts for the hydrochlorination of acetylene. This method utilizes high-throughput first-principles calculations to construct a theoretical model of the "functional group-metal chloride," systematically examining its stability under reaction conditions, and achieving rational design and rapid screening of efficient and stable active site configurations.

[0058] like Figure 5 The diagram shown is an overall flowchart of the catalyst screening method of the present invention. The present invention provides a method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction, comprising the following steps:

[0059] Step (1): Constructing a candidate structure model for a single-atom catalyst with nitrogen-containing functional groups coordinated with metal chlorides. Based on the nitrogen-containing functional groups at the edge of the carbon support, metal chloride active centers are constructed with transition metals selected from Au, Ag, Cu, Fe, Ni, Ru, Rh, Pd, Ir, and Pt. In chlorine coordination environments with x=0 to 5, initial atomic-level coordination structure models of various functional group-metal chlorides were constructed.

[0060] Step (2): Structural optimization and preliminary stability assessment. Using first-principles calculations, the geometric structure of all candidate structural models constructed in step (1) is optimized to obtain ground-state stable configurations. Their binding energies are calculated, and preliminary stability ranking is performed.

[0061] Step (3): Calculation of thermodynamic binding energy. Considering the temperature effect and chlorination potential environment of the reaction system, the free energy is corrected for the stable configuration optimized in step (2), and the thermodynamic binding energy of different functional group-metal chloride coordination structures under the target reaction conditions is calculated.

[0062] Step (4): Systematically examine and plot the relationship between thermodynamic binding energy and temperature and chlorination potential in step (3), obtain the influence law of temperature and chlorination potential on the structural stability of active center, and intuitively reveal the influence of environmental conditions on the structural stability of active center.

[0063] Step (5): Screening of stable active site configurations. By comparing and analyzing the thermodynamic binding energies of all coordination structures obtained in step (4) at the reaction temperature, functional group-metal chloride coordination configurations with negative binding energies and large absolute values ​​under the target acetylene hydrochlorination reaction conditions are screened as stable candidate active sites.

[0064] The steps described above will be explained in detail below with reference to specific embodiments.

[0065] First, the calculation method and corresponding parameter settings were selected: all first-principles calculations in this invention were performed using the VASP software package. During the calculations, the PBE exchange-correlation functional under the generalized gradient approximation was used to describe the electron exchange correlation. The cutoff energy of the plane wave approximation was set to 400 eV, and the Brillouin zone integral used a 2×1×1 Monkhorst-Pack k-point grid. The self-consistent field energy convergence threshold was set to 1×10⁻⁻⁻⁴. 5 eV, and the convergence criterion for force during the geometry optimization process is set to 0.02 eV / Å. In the vibration frequency calculation, the same calculation parameter settings are used to obtain the simple harmonic vibration frequencies of each configuration through the finite displacement method, and the Gibbs free energy at different temperatures is calculated based on the statistical thermodynamic method, where the Gibbs free energy includes the temperature correction terms for the electronic ground state energy, zero-point vibrational energy, vibrational internal energy, and vibrational entropy.

[0066] Example 1:

[0067] Step (1): Construct a model with the -pyro functional groups at the edge of graphene as anchor points. Au, Ag, Cu, Fe, Ni, Ru, Rh, Pd, Ir, and Pt atoms are placed near the N atom, and a model is constructed from... arrive A series of possible coordination structures (M represents metal) are used as the initial model library.

[0068] Step (2): Perform DFT geometric optimization on all models. Calculate the total energy Etotal of the system after the metal chloride complex is combined with the functionalized support, and the energy of the separated support Esupport and precursor Eprecursor. Energy of coordination compounds The formula for calculating binding energy is:

[0069]

[0070] The calculation results are as follows Figure 1 As shown in the figure. The calculation results show that for the -pyro functional group, the stability of the metal chlorine coordination configuration exhibits a volcano-like trend with the increase of chlorine coordination number: in the low coordination number range (x=0 to 1), the binding energy is weak, and the binding energy of some metals is positive, showing endothermic instability; as the coordination number increases to x=3 or 4, the binding energy reaches its peak, and the anchoring effect is the strongest; while when the coordination number reaches x=5, the binding energy increases significantly, that is, the stability decreases, indicating that excessively high chlorine coordination number is not conducive to the stable anchoring of metals on the support.

[0071] The chlorine coordination configurations of different metals exhibit significantly different anchoring strengths. Among them, the first transition metals Au, Ag, and Cu show the most significant differences. or Binding energy of configuration Minimum: -3.02eV, -3.63eV, With a binding energy of -3.79 eV, it exhibits the strongest anchoring effect; while the 3Cl coordination configuration binding energy of metals such as Ir and Ru is relatively weak. -0.27eV, -0.5 eV. Chlorine-free coordination. The structural binding energy is the highest, among which It is 6.21 eV. The voltage is 6.32 eV, indicating extreme endothermic instability. These results provide a quantitative basis for the selection of metal coordination active sites with excellent stability, particularly for Au, Ag, and Cu. The configuration can serve as a reference structure for subsequent experimental synthesis.

[0072] Example 2:

[0073] Step (1): Fix the metal as Au, with the coordination configuration as follows By altering the functional groups at the edge of the carbon support, separate structures were constructed. and , , , , , , , Initial model of functional group coordination, optimization of all models.

[0074] Step (2): Calculate the binding energy The calculation results are as follows: Figure 2 As shown. Different functional groups affect Stability is significantly affected: The binding energy of the structure remains positive, indicating endothermic instability, but it exhibits stability when binding with the pyd01 functional group. It has a voltage of 2.25 eV and binds to the NH101 functional group. The binding energy difference is 0.61 eV, with a stability difference of 1.64 eV. Comparing the stability of different chlorine groups coordinated to different functional groups reveals that... The most stable functional group is NH101, followed by -pyro. These two functional groups have a significant impact on... The binding energies are all below -2.5 eV, and the structure is stable.

[0075] This embodiment filters out, for The active center, with its coordination environment provided by the NH101 functional group, is thermodynamically the most stable, which provides direct theoretical guidance for the targeted synthesis of carbon supports with specific edge chemistry to stabilize gold catalysts.

[0076] Example 3:

[0077] This embodiment is constructed in step (1) of embodiment 2. Based on the initial model of coordination with nine functional groups, the effect of temperature on the stability of the active center was further investigated.

[0078] Step (3): Fix the carbon support and release Vibrational frequencies were calculated for functional group atoms. This was applied to all optimized atoms in Example 2. Under the same computational parameter settings, the simple harmonic frequencies of each configuration were calculated using the finite displacement method, obtaining the frequency distribution and vibrational entropy data of all vibrational modes. Based on this, statistical thermodynamics was used to calculate the Gibbs free energy of each configuration at multiple temperature points within the temperature range of 0 K to 1073.15 K. The temperature step size was reasonably set according to the temperature range, and the sampling points were appropriately densified in regions with drastic temperature changes. The calculation of the Gibbs free energy includes the electronic ground state energy, zero-point vibrational energy correction, the change of vibrational internal energy with temperature, and the temperature correction term for the vibrational entropy.

[0079] Step (4): Based on the Gibbs free energy data obtained in step (3), calculate the various free energy values ​​at different temperatures. The thermodynamic binding energy of the configuration is calculated using the following formula:

[0080]

[0081] in, This represents the Gibbs free energy of the entire system at a specified temperature after a metal chloride is supported on a functional group carrier. The value represents the Gibbs free energy of the nitrogen-containing functional group support without metal loading at a specified temperature. Hexachloro coordination metal precursor The Gibbs free energy at a specified temperature, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. Chlorine molecules Gibbs free energy of a single Cl atom at a specified temperature; The more negative the value, the higher the thermodynamic stability of the coordination configuration at that temperature.

[0082] With temperature as the x-axis, Plot the ordinate as the vertical axis. The formation energy thermal map on nine functional group carriers is represented by color intensity. The relative size, the result is as follows Figure 3 As shown.

[0083] Calculation results show that as temperature increases, Gibbs binding energy Significant changes occur, and the relative stability order of configurations with different chlorine coordination numbers is reversed. Specifically, there is a distinct temperature abrupt change region located around 900 K. Below 900 K, chlorine-free coordination configurations... structure The highest value indicates the most unstable state (marked in red in the figure). When 3Cl to 4Cl coordinates The value is the lowest, indicating the most stable state (marked by the dark blue area in the figure). When the temperature rises above 900K, the high-chlorine coordination structures (4Cl to 5Cl) exhibit... Gradually increasing in concentration, it transitions to an unstable state; while the low-chlorine coordination structures (1Cl to 3Cl) Relative reduction It exhibits a more stable state when coordinated with 1Cl to 3Cl.

[0084] The above results reveal the regulatory mechanism of temperature on the stability of the chlorine coordination configuration of the active site: at lower temperatures, the high chlorine coordination number configuration is more stable; as the temperature increases, the chlorine coordination configuration tends to shift to a lower coordination number. This finding provides a quantitative criterion for selecting the optimal chlorine coordination number under different reaction temperature windows.

[0085] Example 4:

[0086] This embodiment, based on Examples 2 and 3, further investigates the effect of the reaction atmosphere on the stability of the active center.

[0087] Step (4): With the reaction temperature fixed at the typical operating temperature of 473.15 K for the acetylene hydrochlorination reaction, and using the carbon support modified with the most stable functional group NH101 as a model, the chlorination potential was systematically investigated. right (x=1 to 5) Effect of the thermodynamic stability of the active center.

[0088] First, a reference state for the chlorination potential is selected for calibration. The calibration is performed using... Molecules and HCl molecules serve as reference standards for the chlorination potential: in rich... Atmospheric conditions, Reference values ​​are taken from The chemical potential of a molecule, corresponding to The value is -2.27 eV; under HCl-rich atmosphere conditions, The reference value is taken from the chemical potential of the HCl molecule, corresponding to The value is -3.18 eV. Therefore, the range of the chlorination potential is determined to be from HCl-rich atmospheres to HCl-rich atmospheres. A continuous range of atmosphere.

[0089] Secondly, within the aforementioned range of chlorination potential, each [potential] is calculated according to the following formula. Configuration in different Chemical potential binding energy at this value:

[0090]

[0091] in, The chemical potential of the entire system after a metal chloride is supported on a functional group carrier is denoted as . The chemical potential of the nitrogen-containing functional group support without metal loading. Hexachloro coordination metal precursor The chemical potential, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. For The chemical potential of a single Cl atom as indicated by a molecule or an HCl molecule;

[0092] by x-axis Plot the ordinate as the vertical axis. (x=1 to 5) Each configuration Follow The relationship diagram of the changes is as follows: Figure 4 As shown.

[0093] Research results indicate that, with From wealth The atmosphere is lowered to a HCl-rich atmosphere (i.e., (Values ​​change from -2.27 eV to -3.18 eV), different chlorine coordination numbers Chemical potential binding energy of configuration The system exhibits regular changes, and a clear critical chemical potential intersection exists within it. In rich... Atmosphere side ( (Higher region), high chlorine coordination configuration and With lower The value represents the thermodynamically stable state; as... Gradually decrease and cross the critical chemical potential intersection point, and of As the concentration increases, the high-chlorine coordination configuration becomes unstable, while the low-chlorine coordination configuration... of The temperature gradually decreases, reaching a new thermodynamically stable state. In an atmosphere where HCl is the chlorine source ( =-3.18eV), the most stable form of Au species is Monochlorinated coordination state.

[0094] The above results indicate that the reaction atmosphere has a significant regulatory effect on the chlorine coordination configuration of the Au active center: in a rich atmosphere... In an oxidizing atmosphere, Au tends to exist stably in a high-chlorine coordination configuration; in a reducing atmosphere rich in HCl, Au tends to exist stably in a low-chlorine coordination configuration. This finding provides a theoretical basis for selecting and designing the optimal active site configuration based on actual reaction atmosphere conditions.

[0095] This invention proposes a method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction. By constructing a "functional group-metal chloride" coordination structure model and combining it with first-principles high-throughput calculations, the rational design and efficient screening of nitrogen-containing functional group stable metal single-atom active sites at the edge of carbon supports are realized. Compared with the prior art, the core innovation of this invention is: (1) For the first time, multiple nitrogen-containing functional group types, different transition metal types, and different chlorine coordination numbers at the edge of carbon supports are incorporated into a unified design framework, and the synergistic influence of functional group type, metal type, and chlorine coordination number on the stability of the active center is systematically revealed; (2) When evaluating the stability of the active center, the dual influence of the internal coordination environment and external reaction conditions (temperature and reaction atmosphere) is considered at the same time. By drawing a graph showing the relationship between thermodynamic binding energy and temperature and chlorination potential, the regulation mechanism of environmental conditions on the structural stability of the active center is intuitively revealed; (3) Through high-throughput calculations and multi-dimensional screening, the thermodynamically most stable active site configuration can be quickly identified from a large number of candidate configurations, which significantly reduces the R&D cost and cycle brought about by the traditional experimental trial and error method.

[0096] Specifically, this invention verifies the following key findings through examples: the stability of the metal chlorine coordination configuration exhibits a volcanic variation trend with the chlorine coordination number, with the optimal chlorine coordination number concentrated between 3 and 4; the MCl2 or MCl3 configurations of the first subgroup metals Au, Ag, and Cu show the strongest anchoring effect; for Au-based catalysts, the NH101 functional group provides the optimal coordination environment; the temperature abrupt change region is located around 900 K, and the optimal chlorine coordination number changes significantly around this temperature; in an HCl-rich reaction atmosphere, Au species tend to... The form is stable. The above findings provide direct theoretical guidance and quantitative criteria for the experimental synthesis of carbon supports with specific edge chemistry to stabilize metal catalysts, and are of great significance for promoting the rational design of mercury-free catalysts for the hydrochlorination of acetylene.

[0097] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention, and the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. This is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0098] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for screening nitrogen-containing functional group-stabilized single-atom metal catalysts for the hydrochlorination reaction of acetylene, characterized in that, Includes the following steps: 1) Construct candidate structural models for single-atom catalysts with nitrogen-containing functional groups coordinated with metal chlorides; 2) Using first-principles calculations, the geometric structure of all candidate structural models obtained in step 1) is optimized to obtain ground-state stable configurations, and the binding energy is calculated to conduct a preliminary stability assessment. 3) Perform free energy correction on the optimized ground-state stable configuration and calculate the thermodynamic binding energy of the coordination structure of the functional group-metal chloride under the target reaction conditions; 4) Examine and plot the relationship between thermodynamic binding energy and temperature and the relationship between temperature and chlorination potential to obtain the influence of temperature and chlorination potential on the structural stability of the active center. 5) Based on the thermodynamic binding energy data in steps 3) and 4), functional group-metal chloride coordination configurations with negative binding energies and absolute values ​​that meet the threshold size under the target acetylene hydrochlorination reaction conditions are selected as stable candidate active sites.

2. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 1, characterized in that, Step 1) includes the following steps: 1-1) Provide a carbon support having nitrogen-containing functional groups, wherein the carbon support is graphene and the nitrogen-containing functional groups are located at the edge of the graphene. 1-2) Provides metal chloride active centers, in the form of M is a transition metal selected from at least one of Au, Ag, Cu, Fe, Ni, Ru, Rh, Pd, Ir, and Pt, and x is the number of chlorine atoms coordinated with M. The value of x ranges from 0 to 5, representing six coordination states from non-chlorine coordination to pentachlorine coordination. 1-3) Connect the metal atoms in the active center of the metal chloride with the nitrogen atoms in the nitrogen-containing functional group through chemical bonds. For each type of functional group, each type of metal, and each combination of chlorine coordination number x, construct an atomic-level initial coordination structure model one by one to form a candidate structure model library containing multiple functional group-metal chloride combinations.

3. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 2, characterized in that, The nitrogen-containing functional groups are selected from the following types: , , , , , , , .

4. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 1, characterized in that, Step 2) includes the following steps: 2-1) Using a first-principles calculation algorithm, set the calculation parameters and perform geometric optimization on each of the constructed initial coordination structure models to relax each structure to the energy minimum point on its potential energy surface, thereby obtaining the stable configuration of each structure in the ground state. 2-2) For each stable configuration obtained, calculate the total energy of the system. And calculate the energy of the corresponding nitrogen-containing functional group carrier separately. precursor Energy of coordination compounds as well as Energy of a single Cl atom in a molecule Calculate the binding energy of this coordination configuration using the following formula. : ； in, This represents the total energy of the entire system after the metal chloride is combined with the functional group carrier. This represents the energy required for the nitrogen-containing functional group support without metal loading to exist alone. Hexachloro coordination metal precursor The energy when it exists alone, x is the number of chlorine atoms actually coordinated with metal M in the current configuration, and (6-x) represents the number of chlorine atoms dissociated from the hexachlorine precursor. Chlorine molecules The average energy distributed to a single Cl atom; 2-3) For all calculated results Sort the values ​​in ascending order, and based on the sorting results, initially select the binding energies. Configurations with negative values.

5. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 4, characterized in that, In step 2-1), setting the calculation parameters specifically involves: The electron exchange correlation is described using a PBE exchange-correlation functional under the generalized gradient approximation. The plane wave cutoff energy is set to 400 eV. A 2×1×1 MP grid is used for the Brillouin zone integration, and the self-consistent field energy convergence threshold is set to 1×10⁻. 5 eV, with the force convergence criterion set to 0.02 eV / Å.

6. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 1, characterized in that, Step 3) includes the following steps: 3-1) For stable configurations with negative binding energy after optimization, vibration frequency is calculated under the same calculation parameter settings as the first-principles calculation algorithm. By analyzing all vibration modes of each configuration, its simple harmonic vibration frequency and vibration entropy are obtained. 3-2) After obtaining the vibrational frequency data, the Gibbs free energy of each configuration at different temperature points in the temperature range of 0 K to 1073.15 K was calculated using statistical thermodynamics. The Gibbs free energy includes: electronic ground state energy, zero-point vibrational energy, vibrational internal energy, and temperature correction term for vibrational entropy; 3-3) For each configuration obtained at each temperature point, extract the total Gibbs free energy of the system. Gibbs free energy of corresponding nitrogen-containing functional group supports precursor Gibbs free energy as well as Gibbs free energy of a single Cl atom in a molecule Calculate the thermodynamic binding energy at different temperatures using the following formula. : ； in, This represents the Gibbs free energy of the entire system at a specified temperature after a metal chloride is supported on a functional group carrier. The value represents the Gibbs free energy of the nitrogen-containing functional group support without metal loading at a specified temperature. Hexachloro coordination metal precursor The Gibbs free energy at a specified temperature, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. Chlorine molecules Gibbs free energy of a single Cl atom at a specified temperature; The more negative the value, the higher the thermodynamic stability of the coordination configuration at that temperature.

7. The method for screening nitrogen-containing functional group-stabilized single-atom metal catalysts for the acetylene hydrochlorination reaction according to claim 1, characterized in that, Step 4) includes the following steps: 4-1) Selecting the chlorination potential The reference states are respectively adopted The energies of the molecules and HCl molecules are used as a reference. The range of values ​​is calibrated, rich Atmosphere Corresponding Reference values ​​are taken from Molecular chemical potential, corresponding to HCl-rich atmosphere The reference value is taken from the chemical potential of the HCl molecule, thus determining the range of the chlorination potential to be examined from HCl-rich atmospheres to HCl-rich atmospheres. A continuous range of atmosphere; 4-2) Within a defined range of chlorination potentials, for each configuration, calculate the chemical binding energy at different chlorination potentials using the following formula. : ； in, The chemical potential of the entire system after a metal chloride is supported on a functional group carrier is denoted as . The chemical potential of the nitrogen-containing functional group support without metal loading. Hexachloro coordination metal precursor The chemical potential, where x is the number of chlorine atoms actually coordinated with metal M in the current configuration. For The chemical potential of a single Cl atom as indicated by a molecule or an HCl molecule; 4-3) By plotting the relationship between thermodynamic binding energy and chemical potential binding energy as a function of external conditions, the influence of the reaction environment on the structural stability of the active center can be revealed.

8. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 7, characterized in that, Step 4-3) specifically involves: With temperature as the x-axis, thermodynamic binding energy Plot the values ​​of x on different chlorine coordination numbers on supports with different functional groups, using x as the ordinate. configuration A heatmap showing the relationship between temperature and stability, with temperatures ranging from 0 K to 1073.15 K, reflects the stability trend across the entire range from room temperature to the experimental thermal activation temperature; simultaneously... The horizontal axis represents the chemical potential and binding energy. Plot the values ​​of x, with y as the vertical axis, for different chlorine coordination numbers at a fixed reaction temperature. configuration The graph shows the relationship between the chemical potential of chlorination and the reaction atmosphere, reflecting the influence of the reaction atmosphere on the stable configuration of the active center.

9. The method for screening nitrogen-containing functional group stable metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 1, characterized in that, Step 5) includes the following steps: 5-1) At the target acetylene hydrochlorination reaction temperature, extract the thermodynamic binding energy of each functional group-metal chloride coordination configuration at each chlorine coordination number x. or chemical potential binding energy The value; 5-2) With binding energy or The negative value is used as the basic criterion for thermodynamic stability. By comparing the relative magnitudes of the binding energies of different chlorine coordination number configurations on the same functional group of the same metal, the chlorine coordination number configuration with the largest negative binding energy in each combination is selected as the most stable coordination form of the functional group-metal combination under the reaction conditions. 5-3) The most stable coordination forms of each functional group-metal combination screened out are compared horizontally, and the combinations whose absolute value of binding energy meets the threshold value are further selected as stable candidate active sites for the acetylene hydrochlorination reaction.

10. The method for screening nitrogen-containing functional group-stabilized metal single-atom catalysts for the acetylene hydrochlorination reaction according to claim 9, characterized in that, The metals of the stable candidate active sites are Group IB metals; The Group IB metal is Au, Ag, or Cu, and its most stable chlorine coordination form is: or ; The screened stable active site configuration is composed of carbon support surface Stable functional groups Coordination structure; in a reaction atmosphere with HCl as the chlorine source, this The coordination structure undergoes a configurational transformation, changing from a trichlorocoagulation state to... The monochlorinated coordination state exists stably in this state.

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