A method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization
The molecular structure of trifluorochloroethylene was constructed using GaussView and Gaussian software. The thermodynamic and kinetic parameters of the trifluorochloroethylene dimerization reaction were calculated using rigid scanning and transition state optimization. This solved the problem of unclear mechanism of trifluorochloroethylene dimerization reaction, reduced research costs and safety risks, and provided a theoretical basis for the target product.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI 3F NEW MATERIAL TECH CO LTD
- Filing Date
- 2026-02-04
- Publication Date
- 2026-05-26
AI Technical Summary
The reaction mechanism and pathway of trifluorochloroethylene dimerization in existing technologies are unclear. Traditional experimental methods are time-consuming and costly, and it is difficult to obtain thermodynamic and kinetic data of toxic gases under high-temperature conditions, which poses safety risks.
The molecular structure of trifluorochloroethylene was constructed using GaussView and Gaussian software. The reaction pathway was predicted by rigid scanning and transition state optimization, combined with intrinsic reaction coordinate calculation. The electron energy error was corrected using the CCSD/cc-PVTZ method, and the thermodynamic and kinetic parameters of the reaction were calculated.
The mechanism of trifluorochloroethylene dimerization was clarified, reducing research costs and safety risks, providing a theoretical basis for the target product, and improving research efficiency and accuracy.
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Abstract
Description
Technical Field
[0001] This invention relates to the technical field of hexafluorobutadiene preparation process, and in particular to a method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization. Background Technology
[0002] In recent years, with the development of the semiconductor industry, the demand for electronic etching gases has gradually increased. Among them, hexafluorobutadiene has excellent etching performance, is easily decomposed in the atmosphere, and has a low greenhouse effect, thus showing great development prospects.
[0003] There are many methods for preparing hexafluorobutadiene, among which 3,4-dichlorohexafluoro-1-butene can be directly synthesized from hexafluorobutadiene via a dechlorination reaction, which is simple and yields a high rate. Although trifluorochloroethylene, the raw material for preparing 3,4-dichlorohexafluoro-1-butene, is widely available, the yield of 3,4-dichlorohexafluoro-1-butene synthesized from trifluorochloroethylene via a high-temperature dimerization reaction is less than 30%, and the single-pass conversion rate of trifluorochloroethylene is approximately 45%-55%. Its reaction mechanism is similar to olefin cracking, with trifluorochloroethylene undergoing thermal dechlorination at high temperatures to produce hexafluorobutadiene. and Free radicals then react with trifluorochloroethylene or other free radicals to form dimer products. Therefore, this reaction produces a wide variety of byproducts, such as 1,2-dichlorohexafluorocyclobutane, 1,4-dichlorohexafluoro-1-butene, and 1,3-dichlorohexafluoro-1-butene. The selectivity of the main byproduct, 1,2-dichlorohexafluorocyclobutane, is approximately 2-3 times that of 3,4-dichlorohexafluoro-1-butene.
[0004] In the field of chemical engineering, a deep understanding and accurate prediction of the chemical reactions or molecular transformation processes of a system are essential prerequisites for the development of efficient processes, catalyst design, and the creation of new materials. Traditional experimental research methods, such as determining the thermodynamic properties (e.g., heat of reaction, Gibbs free energy change) and kinetic parameters (e.g., reaction rate constant, activation energy) of reactions through calorimetry and spectral analysis, are reliable, but are typically time-consuming and costly. Furthermore, experimental methods often have limitations when dealing with microscopic processes that are difficult to capture, such as highly reactive intermediates and transition states. With the development of computational chemistry, especially first-principles calculations based on quantum mechanics, computer simulations of chemical reaction processes have become an indispensable and powerful supplement and leading tool for experimental research. The dimerization reaction of trifluorochloroethylene is usually carried out at high temperatures of 500℃–600℃. The reaction is rapid, but excessively high temperatures can lead to rapid carbon deposition. Moreover, the products of this reaction system are highly toxic, resulting in high costs and risks in obtaining thermodynamic and kinetic experimental data.
[0005] Currently, most methods for preparing 3,4-dichlorohexafluoro-1-butene via the dimerization of trifluorochloroethylene are only reported in rough experimental preparations, with only partial products known and the specific reaction process remaining unclear. The relevant reaction mechanisms and pathways have not yet been reported.
[0006] Therefore, there is an urgent need for a computational simulation method to study the reaction network, thermodynamics, and kinetics of the trifluorochloroethylene dimerization reaction, which can effectively improve the safety and efficiency of the research. Summary of the Invention
[0007] To address the aforementioned technical problems, this invention provides a method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization, the method comprising:
[0008] (1) The initial structure of the trifluorochloroethylene molecule was constructed using GaussView software, and all corresponding reaction pathways were deduced. The optimal functional and basis set were selected using Gaussian software.
[0009] (2) The transition state of the reaction process is found with the aid of rigid scanning method, and optimization and vibrational frequency analysis are performed to confirm that it has only one imaginary frequency. The intrinsic reaction coordinates (IRC) are used to calculate and verify that the transition state correctly connects the expected reactants / intermediates and products. The reaction path is predicted based on the confirmed transition state. Among them, frequency analysis can be used to confirm that the structure is a minimum point (without imaginary frequency) or a transition state (with only one imaginary frequency) on the potential energy surface, and the thermodynamic functions of the system at specific temperatures and pressures are calculated using statistical thermodynamic formulas. The thermodynamic data (such as enthalpy, Gibbs free energy, etc.) of the substance at a specific temperature can be directly read in the Gaussian output file.
[0010] (3) Using GaussView software, construct the initial molecular structures of all possible reactants, target products, byproducts, possible intermediates, and transition states for the reaction pathways predicted in step (2); perform geometric optimization on all stable point structures to obtain stable configurations on the potential energy surface. This step is the basis for subsequent frequency calculations and thermodynamic corrections. During optimization, the correct spin multiplicity needs to be set according to the system characteristics (such as open shells and spin states).
[0011] (4) Extract the Gibbs free energy or enthalpy value at the specified temperature and pressure from the frequency calculation output file, calculate the thermodynamic function change of the reaction path predicted in step (2), compare the free energy change of different reaction paths, and draw the reaction energy barrier diagram; and use the CCSD / cc-PVTZ method to perform high-precision single-point energy calculation, correct the electronic energy error to obtain more accurate thermodynamic data.
[0012] (5) Using the obtained thermodynamic parameters, the reaction rate constant is obtained by using the transition state theory (TST) and tunneling coefficient, and the pre-exponential factor and activation energy are obtained by fitting the Arrhenius equation.
[0013] Furthermore, the specific steps for predicting the reaction pathway in step (1) are as follows:
[0014] (11) Construct the initial structure of the trifluorochloroethylene molecule using a visual interface;
[0015] (12) Use Gaussian to perform simulation calculations and analyze the bond breaking process: use potential energy surface scanning to help find the transition state of the carbon-chlorine bond breaking process;
[0016] (13) Using different functionals and basis sets, the structures of reactants and products in the carbon-chlorine bond breaking process of trifluorochloroethylene were combined and optimized and the frequency was calculated by using Opt+Freq keywords;
[0017] (14) Select the functional and basis set that are closest to the theoretical value through comparative analysis;
[0018] (15) Based on the selected functional and basis set, infer its reaction pathway.
[0019] To ensure the reliability of the calculation results, the selected method needs to be validated. This can be done by comparing known experimental data or by calculating the thermodynamic properties of a series of related reactions. For special groups or interactions present in the system, more precise calculation methods can be used for correction to improve the prediction accuracy of the entire calculation process.
[0020] Furthermore, the functional selected in step (1) is WB97XD, and the basis set is 6-311g (d,p).
[0021] Furthermore, the specific steps of step (2) are as follows:
[0022] A constrained rigid scan is performed on the characteristic coordinates of the target reaction (such as bond length, dihedral angle, etc.). During the scan, only the target reaction coordinates are released, and the structure of the remaining atomic coordinates is optimized to obtain a curve of energy changing with the reaction coordinates. The highest energy point in the curve is taken as the initial guessed structure of the transition state.
[0023] Starting with the initial guessed structure obtained by rigid scanning, the transition state optimization calculation is performed, which converges to the first saddle point on the potential energy surface (i.e. the energy extreme point corresponding to the transition state), and completes precise convergence to obtain a structure close to the real transition state.
[0024] Vibrational frequency calculations of the obtained near-real transition state structure revealed that it has only one imaginary frequency, and the direction of change in its vibrational amplitude tends to the structural transformation between reactants and products.
[0025] Performing intrinsic reaction coordinate (IRC) calculations confirms that the transition state uniquely connects the corresponding reactant / intermediate to the product, thus verifying that the transition state is a true saddle point on the target reaction pathway, rather than a transition state of other unrelated reactions.
[0026] Furthermore, the predicted reaction pathway in step (2) is:
[0027] Main reaction: 2CTFE → RL316
[0028] Side reaction: 2CTFE → RC316
[0029] 2CTFE→IM1
[0030] RL316→C-C4F6Cl2
[0031] RL316→IM2
[0032] IM1→A-C4F6Cl2
[0033] IM2→B-C4F6Cl2
[0034] IM1 and IM1 represent different intermediates.
[0035] Furthermore, the predicted reaction pathway in step (2) also includes:
[0036] CTFE+RC316→IM3
[0037] IM3→CTFE+RL316
[0038] IM3 represents the intermediate.
[0039] Furthermore, in step (4), the reaction thermodynamic calculation includes the reaction's free energy change ∆G and enthalpy change ∆H, wherein the formula for calculating the free energy change ∆G is:
[0040] ∆G(Gibbs free energy change of reaction) = ∑G(products) - ∑G(reactants)
[0041] The formula for calculating enthalpy change ∆H is:
[0042] ∆H (enthalpy change of reaction) = ∑H (products) - ∑H (reactants).
[0043] Furthermore, in step (4), the temperature range is specified as 633.15K to 873.15K and the pressure is 1 atm.
[0044] Specifically, in Gaussian software, the Opt+Freq task type is used. The reaction path predicted in step (2) obtains the precise equilibrium geometry of each material potential energy surface under 633.15K conditions, and the enthalpy and Gibbs free energy of the corresponding structure are read in the running result file.
[0045] The CCSD / cc-PVTZ method was used for specific geometry optimization. The final accurate single-point energy was combined with the thermodynamic data obtained from the previous frequency calculation to obtain a more accurate Gibbs free energy and enthalpy value for the corresponding structure.
[0046] Furthermore, the formula for calculating the corrected reaction rate constant k in step (5) is as follows:
[0047]
[0048] In the formula, This is the tunneling coefficient;
[0049] The reaction rate constant obtained through TST is calculated using the following formula:
[0050]
[0051] In the formula, The degree of degeneracy of the reaction; Boltzmann constant; h is Planck constant; R is molar gas constant; T is temperature; The pressure is atmospheric pressure, taken as 1 bar; The activation free energy change refers to the difference between the Gibbs free energy of the transition state of a reaction at temperature T and the Gibbs free energy of the reactants; n is the number of reactant molecules (or atoms, ions, free radicals, etc.) that directly participate in the elementary reaction. .
[0052] Tunneling coefficient The Wigner correction method is used, and its calculation formula is:
[0053]
[0054] In the formula, For the imaginary frequency of the transition state, cm -1 。
[0055] The present invention has the following beneficial effects:
[0056] (1) This invention constructs a specific reaction network for the dimerization of trifluorochloroethylene, clarifies its reaction mechanism, speculates on the intermediates and transition states that may exist in the reaction process, and calculates the thermodynamic and kinetic data of the relevant reactions. It attempts to provide a solution for improving the target product 3,4-dichlorohexafluoro-1-butene from the perspective of reaction mechanism, and provides a theoretical basis for industrial production.
[0057] (2) This invention can avoid the research risks brought about by high-risk experiments, and can avoid the safety threats and environmental hazards caused by directly operating toxic gases under high temperature conditions, thus greatly reducing the research cost.
[0058] (3) This invention selects the optimal functional and basis set using Gaussian software, predicts its reaction path, and confirms that the target reaction has only one imaginary frequency by performing rigid scanning, transition state optimization and vibrational frequency analysis in sequence. The intrinsic reaction coordinates (IRC) are used to calculate and verify that the transition state correctly connects the expected reactants / intermediates and products. The reaction path is predicted based on the confirmed transition state, which can avoid the research risks brought about by high-risk experiments, avoid the safety threats and environmental hazards brought about by directly operating toxic gases under high temperature conditions, and greatly reduce the research cost.
[0059] (4) This invention can directly visualize transition states and highly reactive intermediates that cannot be captured by experiments through Gaussian calculations, thereby clearly revealing the process of chemical bond breaking and formation from the electronic structure level.
[0060] (5) By constructing a complete reaction potential energy surface, this invention can compare the energy barriers and thermodynamic driving forces of each path for generating target products and by-products in parallel and quantitatively, thus clarifying the root cause of by-product formation. Attached Figure Description
[0061] Figure 1 This is a flowchart of the reaction thermodynamics and kinetics calculations in this invention.
[0062] Figure 2 This is a schematic diagram of the trifluorochloroethylene dimerization reaction network prediction in this invention.
[0063] Figure 3 This is a schematic diagram of the reactants, products, intermediates, and transition state structures during the trifluorochloroethylene dimerization process in this invention.
[0064] Figure 4 This is a schematic diagram of the energy barrier for the dimerization reaction of trifluorochloroethylene in this invention.
[0065] Figure 5 This is a schematic diagram of the reaction pathway for synthesizing the target product from 1,2-dichlorohexafluorocyclobutane and trifluorochloroethylene in this invention. Detailed Implementation
[0066] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. However, these embodiments are not intended to limit the present invention. Any similar structures and similar variations of the present invention should be included in the protection scope of the present invention. The commas in the present invention all indicate the relationship between and. The English letters in the present invention are case-sensitive.
[0067] like Figure 1 As shown, this invention provides a thermodynamic and kinetic calculation method for the dimerization reaction of trifluorochloroethylene. The simulation calculations for trifluorochloroethylene are performed at ambient pressure (1 atm) and a temperature range of 633.15 K to 873.15 K. The method includes the following steps:
[0068] Step 1: Construct the initial structure of the trifluorochloroethylene molecule using GaussView software, deduce all its corresponding reaction pathways, and select the optimal functional and basis set using Gaussian software.
[0069] First, the initial structure of the trifluorochloroethylene molecule was constructed using GaussView software. Then, Gaussian simulations were performed to analyze the bond-breaking process. Potential surface scanning was used to locate the transition state of the carbon-chlorine bond breaking process. The simulation results showed that there was no significant energy barrier in the carbon-chlorine bond breaking process of the trifluorochloroethylene molecule, i.e., no obvious transition state. Subsequently, different functionals and basis sets were used, and the structures of the reactants and products in the carbon-chlorine bond breaking process of trifluorochloroethylene were optimized and their frequencies calculated using the Opt+Freq keywords. The reaction equation for this process is as follows:
[0070]
[0071] The theoretical value for the carbon-chlorine bond dissociation energy in this process is approximately 103.9. 2 kcal / mol. Calculations were performed using different functionals and basis sets. After comparative analysis, the calculation result of WB97XD / 6-311g(d,p) was found to be closest to the theoretical value and had the highest accuracy. Therefore, this functional was selected for subsequent simulation studies.
[0072] Step 2: Use rigid scanning method to find the transition state of the reaction process, and perform optimization and vibrational frequency analysis to confirm that it has only one imaginary frequency. Use intrinsic reaction coordinates to calculate and verify that the transition state correctly connects the expected reactant / intermediate and product. Predict the reaction path based on the confirmed transition state.
[0073] Due to the scarcity of research reports on the dimerization reaction of trifluorochloroethylene, its reaction mechanism and network remain unclear. Therefore, it is necessary to prioritize the prediction of potential reaction pathways based on existing experimental results, followed by verification and analysis through simulation calculations. The entire process follows a cycle of "stabilization point optimization → transition state search → frequency verification → energy calculation".
[0074] The most crucial step lies in the search and verification of the transition state, requiring the identification of a saddle point structure linking the two stable points, i.e., having one and only one imaginary frequency. For guessing the initial transition state, methods such as the Transition State Search (TS), QST2 / QST3, and rigid scanning are commonly used. QST2 and QST3 require optimized structures of the reactants and products as input, but this calculation process demands explicit knowledge of which atom in the product corresponds to each atom in the reactants, potentially leading to errors. Rigid scanning, on the other hand, performs a constrained optimization scan of the target reaction coordinates (such as bond lengths and dihedral angles) to find the highest energy point as the initial guess for the transition state. The TS method, however, only requires constructing the transition state structure to quickly infer a transition state structure close to the true saddle point, achieving precise convergence. Furthermore, it requires determining whether the vibrational amplitude of the imaginary frequency tends towards the reactants and products, and performing IRC verification. If the IRC calculation verification confirms that the transition state connects the expected reactants and products, then the transition state is considered to meet expectations. Therefore, in order to improve the efficiency of finding the reaction transition state, we first use rigid scanning for auxiliary searching, then construct the transition state structure and use the TS method for calculation, and finally verify the specific structure and data of the transition state.
[0075] The specific steps are as follows: a constrained rigid scan is performed on the characteristic coordinates of the target reaction (such as bond length, dihedral angle, etc.). During the scan, only the target reaction coordinates are released, and the structure of the remaining atomic coordinates is optimized to obtain a curve of energy changing with the reaction coordinates. The highest energy point in the curve is taken as the initial guessed structure of the transition state.
[0076] Starting with the initial guessed structure obtained by rigid scanning, the transition state optimization calculation is performed, which converges to the first saddle point on the potential energy surface (i.e. the energy extreme point corresponding to the transition state), and completes precise convergence to obtain a structure close to the real transition state.
[0077] Vibrational frequency calculations of the obtained near-real transition state structure revealed that it has only one imaginary frequency, and the direction of change in its vibrational amplitude tends to the structural transformation between reactants and products.
[0078] Performing intrinsic reaction coordinate (IRC) calculations confirms that the transition state uniquely connects the corresponding reactant / intermediate to the product, thus verifying that the transition state is a true saddle point on the target reaction pathway, rather than a transition state of other unrelated reactions.
[0079] Using the above method, the final result is as follows: Figure 2 The reaction network shown is as follows: trifluorochloroethylene is reacted under high temperature conditions to produce... and Free radicals are formed, which then react with other free radicals or trifluorochloroethylene to produce dimer products. The main products are 3,4-dichlorohexafluoro-1-butene and 1,2-dichlorohexafluorocyclobutane, with other byproducts such as 1,4-dichlorohexafluoro-1-butene and 1,3-dichlorohexafluoro-1-butene. The main product 3,4-dichlorohexafluoro-1-butene may also continue to react to generate other byproducts, and the main byproduct 1,2-dichlorohexafluorocyclobutane may be converted into the main product 3,4-dichlorohexafluoro-1-butene.
[0080] Step 3: Based on the reaction path predicted in Step 2, use GaussView to construct the initial geometry of all possible reactants, intermediates, products, and corresponding transition states to prepare for subsequent accurate calculations.
[0081] Step 4: Extract the Gibbs free energy or enthalpy at the specified temperature and pressure from the frequency calculation output file, calculate the thermodynamic function changes of the reaction path predicted in Step 2, compare the free energy changes of different reaction paths, and draw the reaction energy barrier diagram; and use the CCSD / cc-PVTZ method to perform high-precision single-point energy calculation, correct the electronic energy error to obtain more accurate thermodynamic data.
[0082] Based on the reaction network diagram predicted in step two, reaction thermodynamics calculations are performed. The formulas for calculating the reaction's free energy change ∆G and enthalpy change ∆H are as follows:
[0083] ∆G(Gibbs free energy change of reaction) = ∑G(products) - ∑G(reactants)
[0084] ∆H (enthalpy change of reaction) = ∑H (products) - ∑H (reactants)
[0085] The methods for obtaining the corresponding thermodynamic data for each substance are as follows:
[0086] In Gaussian software, the Opt+Freq task type and the WB97XD / 6-311g(d,p) method are used to calculate the precise equilibrium geometry of each material potential energy surface at 633.15 K. The enthalpy and Gibbs free energy of the corresponding structure can be read from the result file, providing data for thermodynamic correction.
[0087] To obtain more accurate energies and correct for electron energy errors caused by inaccuracies in the preceding DFT functional, high-precision single-point energy calculations are required for the corresponding structure. Employing a method with higher precision than geometric optimization, this invention uses the CCSD / cc-PVTZ method. The final accurate single-point energy is combined with the thermodynamic data obtained from the preceding frequency calculations to obtain more accurate Gibbs free energy and enthalpy values for the corresponding structure.
[0088] The simulation calculations were performed at temperatures of 673.15 K, 713.15 K, 753.15 K, 793.15 K, 833.15 K, and 873.15 K, respectively, repeating the above steps. The reactants, products, intermediates, and transition states involved in the reaction network, along with their abbreviations, are shown below. Figure 3 As shown in the diagram. TS represents the transition state, and IM represents the intermediate; the reaction energy barrier diagram is shown below. Figure 4 As shown. The specific reaction equation is as follows:
[0089] 1:2CTFE→RL316
[0090] 2:2CTFE→RC316
[0091] 3:2CTFE→IM1
[0092] 4:RL316→C-C4F6Cl2
[0093] 5:RL316→IM2
[0094] 6:IM1→A-C4F6Cl2
[0095] 7:IM2→B-C4F6Cl2
[0096] Step 5: Using the obtained thermodynamic parameters, the reaction rate constant is obtained by employing the transition state theory (TST) and tunneling coefficient, and the pre-exponential factor and activation energy are obtained by fitting the Arrhenius equation.
[0097] Using the thermodynamic parameters obtained in step four, the reaction rate constant is obtained using transition state theory (TST) and tunneling coefficient, and the calculation formula is as follows:
[0098]
[0099] In the formula, k is the corrected reaction rate constant; This is the tunneling coefficient; The reaction rate constant obtained through TST is calculated using the following formula:
[0100]
[0101] In the formula, The degree of degeneracy of the reaction; Boltzmann constant; h is Planck constant; R is molar gas constant; T is temperature; The pressure is atmospheric pressure, taken as 1 bar; The activation free energy change refers to the difference between the Gibbs free energy of the transition state of a reaction at temperature T and the Gibbs free energy of the reactants; for an n-molecule reaction, .
[0102] The calculation uses the Wigner correction method, and the calculation formula is as follows:
[0103]
[0104] In the formula, For the imaginary frequency of the transition state, cm -1 In this case study, due to the high reaction temperature and very small imaginary frequency, the reaction process does not involve the transfer of light atoms such as hydrogen. The value can be considered as 1.
[0105] The corresponding thermodynamic and kinetic parameters calculated for the final reaction 1-7 are shown in Table 1-7.
[0106] Table 1
[0107]
[0108] Table 2
[0109]
[0110] Table 3
[0111]
[0112] Table 4
[0113]
[0114] Table 5
[0115]
[0116] Table 6
[0117]
[0118] Table 7
[0119]
[0120] The above reaction kinetic data were fitted using the Arrhenius equation, which is as follows:
[0121] k = Aexp(-E / RT)
[0122] In the formula, A is the pre-exponential factor and E is the activation energy. The final reaction kinetic parameters for each reaction step are shown in Table 8.
[0123] Table 8
[0124]
[0125] In addition, the main byproduct 1,2-dichlorohexafluorocyclobutane reacts with the raw material trifluorochloroethylene via a reaction pathway to generate the target product 3,4-dichlorohexafluoro-1-butene, as follows:
[0126] 8:CTFE+RC316→IM3
[0127] 9:IM3→CTFE+RL316
[0128] The specific structures of reactions 8 and 9 above are as follows: Figure 5 As shown. Using the same research methods as the previous steps, the pre-exponential factor A of reaction 8 was finally obtained as 3.41E12 m. 3 / (mol*s), the activation energy is 397683 J / mol. The pre-exponential factor A of reaction 9 is 1.77E14 1 / s, the activation energy is 435771 J / mol, and the main byproduct RC316 obtained can be co-fed with the raw material trifluorochloroethylene to a certain extent to improve the yield of the target product 3,4-dichlorohexafluoro-1-butene.
[0129] This invention constructs a specific reaction network for the dimerization of trifluorochloroethylene, clarifies its reaction mechanism, predicts possible intermediates and transition states during the reaction, and calculates the thermodynamic and kinetic data of the relevant reactions. It attempts to provide a solution for improving the target product 3,4-dichlorohexafluoro-1-butene from the perspective of reaction mechanism, and provides a theoretical basis for industrial production.
[0130] Although preferred embodiments of this application 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 the preferred embodiments as well as all changes and modifications falling within the scope of this application.
Claims
1. A method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization, characterized in that, The method includes: (1) The initial structure of the trifluorochloroethylene molecule was constructed using GaussView software, and all corresponding reaction pathways were deduced. The optimal functional and basis set were selected using Gaussian software. (2) The transition state of the reaction process is found by rigid scanning method, and optimization and vibrational frequency analysis are performed to confirm that it has only one imaginary frequency. The intrinsic reaction coordinates are used to calculate and verify that the transition state correctly connects the expected reactants / intermediates and products. The reaction path is predicted based on the confirmed transition state. (3) Using GaussView software, construct the initial molecular structures of all possible reactants, target products, byproducts, possible intermediates and transition states for the reaction pathway predicted in step (2); (4) Extract the Gibbs free energy or enthalpy value at the specified temperature and pressure from the frequency calculation output file, calculate the thermodynamic function change of the reaction path predicted in step (2), compare the free energy change of different reaction paths, and draw the reaction energy barrier diagram; and use the CCSD / cc-PVTZ method to perform high-precision single-point energy calculation and correct the electronic energy error. (5) Using the obtained thermodynamic parameters, the reaction rate constant is obtained by using the transition state theory and tunneling coefficient, and the pre-exponential factor and activation energy are obtained by fitting the Arrhenius equation.
2. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, The specific steps for predicting the reaction pathway in step (1) are as follows: (11) Construct the initial structure of the trifluorochloroethylene molecule using a visual interface; (12) Use Gaussian to perform simulation calculations and analyze the bond breaking process: use potential energy surface scanning to help find the transition state of the carbon-chlorine bond breaking process; (13) Using different functionals and basis sets, the structures of reactants and products in the carbon-chlorine bond breaking process of trifluorochloroethylene were combined and optimized and the frequency was calculated by using Opt+Freq keywords; (14) Select the functional and basis set that are closest to the theoretical value through comparative analysis; (15) Based on the selected functional and basis set, infer its reaction pathway.
3. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 2, characterized in that, The functional selected in step (1) is WB97XD, and the basis set is 6-311g (d,p).
4. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, The specific steps of step (2) are as follows: A constrained rigid scan is performed on the characteristic coordinates of the target reaction. During the scan, only the target reaction coordinates are released, and the structure of the remaining atomic coordinates is optimized to obtain a curve of energy changing with the reaction coordinates. The highest energy point in the curve is taken as the initial guessed structure of the transition state. Starting with the initial guessed structure obtained by rigid scanning, we perform transition state optimization calculations, converge to the first-order saddle point on the potential energy surface, and complete precise convergence to obtain a structure close to the real transition state. Vibrational frequency calculations of the obtained near-real transition state structure revealed that it has only one imaginary frequency, and the direction of change in its vibrational amplitude tends to the structural transformation between reactants and products. Perform intrinsic reaction coordinate calculations to confirm that the transition state can uniquely connect the corresponding reactant / intermediate and product. This verifies that the transition state is a true saddle point on the target reaction path, rather than a transition state of other irrelevant reactions.
5. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, The predicted reaction pathway in step (2) is: Main reaction: 2CTFE → RL316 Side reaction: 2CTFE → RC316 2CTFE→IM1 RL316→C-C4F6Cl2 RL316→IM2 IM1→A-C4F6Cl2 IM2→B-C4F6Cl2 IM1 and IM2 represent different intermediates.
6. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 5, characterized in that, The predicted reaction pathway in step (2) also includes: CTFE+RC316→IM3 IM3→CTFE+RL316 IM3 represents the intermediate.
7. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, In step (4), the reaction thermodynamic calculation includes the reaction's free energy change ∆G and enthalpy change ∆H, wherein the formula for calculating the free energy change ∆G is: ∆G(Gibbs free energy change of reaction) = ∑G(products) - ∑G(reactants) The formula for calculating enthalpy change ∆H is: ∆H (enthalpy change of reaction) = ∑H (products) - ∑H (reactants).
8. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, In step (4), the specified temperature range is 633.15K to 873.15K and the pressure is 1 atm.
9. The method for calculating the reaction thermodynamics and kinetics of trifluorochloroethylene dimerization according to claim 1, characterized in that, The formula for calculating the corrected reaction rate constant k in step (5) is: In the formula, This is the tunneling coefficient; The reaction rate constant obtained through TST is calculated using the following formula: In the formula, The degree of degeneracy of the reaction; Boltzmann constant; h is Planck constant; R is molar gas constant; T is temperature; The pressure is atmospheric pressure, taken as 1 bar; The activation free energy change refers to the difference between the Gibbs free energy of the transition state of a reaction at temperature T and the Gibbs free energy of the reactants; n is the number of reactant molecules / atoms / ions / free radicals that directly participate in the elementary reaction. ; Tunneling coefficient The Wigner correction method is used, and its calculation formula is: In the formula, For the imaginary frequency of the transition state, cm -1 .