Iridium / phosphine ligand catalyst performance calculation method based on density functional theory and catalyst
Through the density functional theory-based calculation method of iridium/phosphine ligand catalyst performance, the problems of high energy consumption and serious pollution in acetic acid production were solved, efficient and environmentally friendly catalyst optimization was achieved, and the efficiency of acetic acid production was improved.
Patent Information
- Application Number
- CN202510741651.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-04
- Publication Date
- 2025-09-12
AI Technical Summary
The existing acetic acid production process has problems such as high energy consumption, serious pollution, low conversion rate, poor selectivity and equipment corrosion. The traditional catalyst preparation method is inefficient and seriously wastes resources.
A density functional theory-based calculation method for iridium/phosphine ligand catalyst performance is used to obtain basic catalyst data, calculate binding energy and thermodynamic data, predict the catalytic reaction mechanism and spatial topography, and optimize the catalyst structure.
It improves the selectivity and stability of the catalyst, reduces resource waste, lowers experimental costs, meets environmental protection requirements, and saves time and computing resources.
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Figure CN120636583A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of iridium / phosphine ligand catalysts, and in particular to a performance calculation method of iridium / phosphine ligand catalysts based on density functional theory and an iridium / phosphine ligand catalyst. Background Art
[0002] Acetic acid, an important fatty acid, is widely used in industries such as chemicals, light industry, textiles, pesticides, pharmaceuticals, electronics, and food, and plays a vital role in countries around the world. In recent years, my country has seen rapid growth in downstream acetic acid products, such as acetic anhydride, acetate esters, terephthalic acid, polyvinyl alcohol, vinyl acetate, cellulose acetate, chloroacetic acid, and diketene. This has significantly driven market demand for acetic acid, leading to rapid market growth. After decades of continuous development and progress, the acetic acid industry has established a variety of industrialized production technologies worldwide, including acetaldehyde oxidation, light hydrocarbon liquid-phase oxidation, and methanol carbonylation. The acetaldehyde oxidation process involves the oxidation of acetaldehyde with oxygen under specific pressure and temperature to produce peracetic acid. The peracetic acid is then decomposed into crude acetic acid in the presence of a catalyst, which then undergoes distillation processes, including removal of high-boiling and low-boiling acids, and evaporation, to produce finished acetic acid. This process is energy-intensive and uses mercuric sulfate, a catalyst that is highly environmentally polluting, and is gradually being phased out. The liquid-phase oxidation of liquid hydrocarbons primarily utilizes n-butane and naphtha as feedstocks. Acetic acid is produced by liquid-phase oxidation of n-butane or naphtha. The oxidation process occurs in the liquid phase at a reaction temperature of 150-225°C and a pressure of 4M-8MPa. The catalyst is an acetate or cyclohexane salt of cobalt, manganese, nickel, or chromium. The oxidation product undergoes multiple distillation steps to produce acetic acid. Byproducts of butane oxidation include acetaldehyde, acetone, and methanol, while those of light oil oxidation include formic acid, propionic acid, and butyric acid. The acetic acid yield is 72%-76%. This process has low conversion rates, poor selectivity, and produces numerous byproducts. The separation process is complex, with significant equipment corrosion and high material requirements. Consequently, investment and energy consumption are high, and economic feasibility is limited. No production facilities employing this method exist in China. The methanol carbonylation process uses methanol and CO as feedstocks to synthesize acetic acid via carbonylation. The carbonylation process has the advantages of diverse feedstock routes, using coal tar, natural gas, and heavy oil as its base raw materials. It is particularly suitable for coal chemical industry, produces few byproducts and waste, and boasts highly active and long-lived catalysts. According to the International Acetic Acid Association, as of 2021, China's annual acetic acid production was approximately 7 million tons, with a global total capacity of approximately 20 million tons. China accounts for 35% of this capacity, ranking first globally.
[0003] Therefore, designing and developing an efficient and stable acetic acid synthesis process is a key link in improving the efficiency of domestic acetic acid production. Summary of the Invention
[0004] The object of the present invention is to provide a method for calculating the performance of iridium / phosphine ligand catalysts based on density functional theory to solve at least one of the above technical problems.
[0005] The present invention provides the following solutions:
[0006] According to one aspect of the present invention, a method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory is provided. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory comprises:
[0007] Obtain basic data information of each intermediate molecular model of iridium-catalyzed methanol carbonylation;
[0008] Obtain an iridium / phosphine ligand catalyst, the general structural formula of the iridium / phosphine ligand catalyst is [Ir(CO)I2L] - , L is a phosphine ligand;
[0009] Obtain the binding energy between the phosphine ligand and the central metal Ir;
[0010] Calculate thermodynamic data and transition states of catalytic reaction mechanisms in the presence of phosphine ligands;
[0011] The buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts were calculated using the SambVca program.
[0012] Optionally, the basic data information of each intermediate molecular model of the iridium-catalyzed methanol carbonylation is obtained, including:
[0013] The DFT / M06 / (DEF2SVP / Landz12dz) calculation method in the Gaussian program package was used to perform structural optimization and frequency calculation on each intermediate molecular model to obtain the stable configuration and thermodynamic data of each molecular model, find the transition state of the reaction, and determine that the reaction rate-determining step is I. - The activation energy of the removal reaction is 52.48 kcal / mol.
[0014] Alternatively, the phosphine ligand includes tricyclohexylphosphine, triethylphosphine, trimethylphosphine, triphenylphosphine, trimethoxyphosphine and triphenoxyphosphine.
[0015] Optionally, obtaining the binding energy between the phosphine ligand and the central metal Ir includes:
[0016] The binding energy between the phosphine ligand and the central metal Ir was calculated using the DFT / M06 / DEF2SVP calculation method in the Gaussian program package.
[0017] Optionally, the thermodynamic data and transition states for calculating the catalytic reaction mechanism in the presence of a phosphine ligand include:
[0018] The DFT / M06 / calculation method in the Gaussian program package was used to calculate the thermodynamic data and transition states of the catalytic reaction mechanism in the presence of phosphine ligands.
[0019] Optionally, the calculation of the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts using the SambVca program includes:
[0020] The SambVca program was used to calculate the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts. By comparing the buried volumes of different ligands, the stability and reaction activity of the complexes were predicted and explained.
[0021] The present application also provides an iridium / phosphine ligand catalyst, characterized in that the structural formula of the iridium / phosphine ligand catalyst is [Ir(CO)I2L] - .
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] 1. The method of the present invention solves the shortcomings of the traditional "trial and error" method of preparing catalysts, saves time and resources, determines the initial catalyst structure based on density functional theory, and analyzes the performance through theoretical calculations.
[0024] 2. The present invention does not involve the implementation and experiment of chemical products in the entire process, will not produce chemical pollution, is in line with the concept of environmental protection and green, and has low cost, convenient operation, easy implementation, and is suitable for application and promotion.
[0025] 3. The present invention can predict the performance of the catalyst in advance through calculation results before the experiment, select suitable samples in advance, and save experimental time.
[0026] 4. By setting the calculation parameters reasonably, the calculation time is reduced and the waste of computer time is avoided. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a flow chart of a method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory in one embodiment of the present application.
[0028] Figure 2 This is a schematic diagram of the energy pathway of iridium-based catalyst reactions.
[0029] Figure 3 is the binding energy between the phosphine ligand and the metal center Ir.
[0030] Figure 4 This is a schematic diagram of the energy pathway of the iridium / triphenylphosphine catalyst reaction.
[0031] Figure 5 is the relationship between the buried volume of the ligand and the I-removal energy. DETAILED DESCRIPTION
[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.
[0033] like Figure 1 The performance calculation method of iridium / phosphine ligand catalyst based on density functional theory shown includes:
[0034] Obtain basic data information of each intermediate molecular model of iridium-catalyzed methanol carbonylation;
[0035] Obtain an iridium / phosphine ligand catalyst, the general structural formula of the iridium / phosphine ligand catalyst is [Ir(CO)I2L] - , L is a phosphine ligand;
[0036] Obtain the binding energy between the phosphine ligand and the central metal Ir;
[0037] Calculate thermodynamic data and transition states of catalytic reaction mechanisms in the presence of phosphine ligands;
[0038] The buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts were calculated using the SambVca program.
[0039] In this embodiment, the basic data information for obtaining each intermediate molecular model of iridium-catalyzed methanol carbonylation includes:
[0040] The DFT / M06 / (DEF2SVP / Landz12dz) calculation method in the Gaussian program package was used to perform structural optimization and frequency calculation on each intermediate molecular model to obtain the stable configuration and thermodynamic data of each molecular model, find the transition state of the reaction, and determine that the reaction rate-determining step is I. - The activation energy of the removal reaction is 52.48 kcal / mol.
[0041] In this embodiment, the phosphine ligand includes tricyclohexylphosphine, triethylphosphine, trimethylphosphine, triphenylphosphine, trimethoxyphosphine and triphenoxyphosphine.
[0042] In this embodiment, obtaining the binding energy between the phosphine ligand and the central metal Ir includes:
[0043] The binding energy between the phosphine ligand and the central metal Ir was calculated using the DFT / M06 / DEF2SVP calculation method in the Gaussian program package.
[0044] In this embodiment, the thermodynamic data and transition states for calculating the catalytic reaction mechanism in the presence of a phosphine ligand include:
[0045] The DFT / M06 / calculation method in the Gaussian program package was used to calculate the thermodynamic data and transition states of the catalytic reaction mechanism in the presence of phosphine ligands.
[0046] In this embodiment, the calculation of the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts using the SambVca program includes:
[0047] The SambVca program was used to calculate the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts. By comparing the buried volumes of different ligands, the stability and reaction activity of the complexes were predicted and explained.
[0048] The present application is further described in detail below by way of examples. It should be understood that the examples do not constitute any limitation to the present application.
[0049] Step 1: Determine the reaction mechanism of the iridium-based catalyst through literature analysis, use the DFT / M06 / (DEF2SVP / Landz12dz) calculation method in the Gaussian program package to perform structural optimization and frequency calculation on each intermediate molecular model, obtain the stable configuration and thermodynamic data of each molecular model, find the transition state of the reaction, and determine that the rate-determining step of the reaction is the removal of I-, the reaction activation energy is 52.48 kcal / mol, and the reaction path energy barrier is as follows: Figure 2 shown.
[0050] Step 2: According to literature review, phosphine ligands bind to metal centers more strongly than oxygen ligands and nitrogen ligands. PR3 ligands accept electrons fed back from the metal center through the hybrid orbital of the d orbital of the P atom and the σ* orbital of PR. Phosphine ligands bind to the metal center more tightly. Therefore, the present invention selects phosphine ligands as the object.
[0051] Step 3, select tricyclohexylphosphine, triethylphosphine, trimethylphosphine, triphenylphosphine, trimethoxyphosphine and triphenoxyphosphine. Table 1 shows that the binding energy of Ir and triphenylphosphine is -42.37kcal / mol, and the bond lengths of Ir-P are The low binding energy indicates that the complex formed with Ir is unstable. This is likely due to the weak electron-donating ability of the triphenylphosphine ligand and its significant steric hindrance, resulting in a low binding energy between the ligand and Ir. The binding energies of tricyclohexylphosphine, triethylphosphine, and trimethylphosphine with Ir are -50.25 kcal / mol, -46.92 kcal / mol, and -45.88 kcal / mol, respectively. Stronger chemical bonds, in turn, have longer bond lengths. This is because tricyclohexylphosphine, triethylphosphine, and trimethylphosphine are strong σ electron donors with high lone pair energy and a wide electron cloud extension, allowing them to form strong coordination bonds without being close to Ir. In contrast, the binding energies of trimethoxyphosphine and triphenoxyphosphine with Ir are -49.73 kcal / mol and -48.20 kcal / mol, respectively. The coordination bonds formed by trimethoxyphosphine and triphenoxyphosphine with Ir are primarily metal-to-ligand feedback π bonds. PR3 requires the PR σ* orbital to accept electrons, and must be in close proximity to Ir to form effective orbital overlap to accept feedback electrons.
[0052] In this embodiment, the binding energy between the ligand and the central metal Ir was calculated using the DFT / M06 / DEF2SVP calculation method in the Gaussian program package. The calculation formula is E binding =E total -(E ligand +E [IrCOI2]- );
[0053] Step 4: The DFT / M06 / (DEF2SVP / Landz12dz) calculation method in the Gaussian program package is used to calculate the thermodynamic data and transition state of the catalytic reaction mechanism in the presence of the ligand. The structural optimization and frequency calculation of each intermediate molecular model are performed to determine the rate-determining step of the reaction. The results show that the reaction energy barriers of all iridium / phosphine ligand catalysts are reduced, and the energy barrier of iridium / triphenylphosphine catalyst is the lowest, which is 41.64 kcal / mol. The rate-determining step is the removal of I-, and its reaction energy path is as follows: Figure 3 The energy for I-removal in the iridium / tricyclohexylphosphine catalyst is 36.66 kcal / mol, but the rate-determining step of the reaction is the oxidative addition of iodomethane, with an energy barrier of 44.79 kcal / mol. This is because the steric hindrance of the tricyclohexyl group is too large. Although it effectively weakens the bond energy of the Ir-I bond, it hinders the addition of iodomethane. However, the overall reaction energy barrier is still reduced.
[0054] Step 5, use the SambVca program to calculate the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts, and make the following Figure 4 The trend line shows that the energy required for I-desorption is inversely proportional to the buried volume of the ligand.
[0055] The present application also provides an iridium / phosphine ligand catalyst, the general structural formula of which is [Ir(CO)I2L] - .
[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for calculating the performance of iridium / phosphine ligand catalysts based on density functional theory, characterized in that: The performance calculation method of the iridium / phosphine ligand catalyst based on density functional theory includes: Obtain basic data information of each intermediate molecular model of iridium-catalyzed methanol carbonylation; Obtain an iridium / phosphine ligand catalyst, the general structural formula of the iridium / phosphine ligand catalyst is [Ir(CO)I2L] - , L is a phosphine ligand; Obtain the binding energy between the phosphine ligand and the central metal Ir; Calculate thermodynamic data and transition states of catalytic reaction mechanisms in the presence of phosphine ligands; The buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts were calculated using the SambVca program.
2. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory according to claim 1, wherein: The basic data information for obtaining each intermediate molecular model of iridium-catalyzed methanol carbonylation includes: The DFT / M06 / (DEF2SVP / Landz12dz) calculation method in the Gaussian program package was used to perform structural optimization and frequency calculation on each intermediate molecular model to obtain the stable configuration and thermodynamic data of each molecular model, find the transition state of the reaction, and determine that the reaction rate-determining step is I. - The activation energy of the removal reaction is 52.48 kcal / mol.
3. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory according to claim 2, wherein: The phosphine ligands include tricyclohexylphosphine, triethylphosphine, trimethylphosphine, triphenylphosphine, trimethoxyphosphine and triphenoxyphosphine.
4. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory according to claim 3, wherein: The step of obtaining the binding energy between the phosphine ligand and the central metal Ir comprises: The binding energy between the phosphine ligand and the central metal Ir was calculated using the DFT / M06 / DEF2SVP calculation method in the Gaussian program package.
5. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory according to claim 4, wherein: The thermodynamic data and transition states for calculating the catalytic reaction mechanism in the presence of a phosphine ligand include: The DFT / M06 / calculation method in the Gaussian program package was used to calculate the thermodynamic data and transition states of the catalytic reaction mechanism in the presence of phosphine ligands.
6. The method for calculating the performance of an iridium / phosphine ligand catalyst based on density functional theory according to claim 5, wherein: The use of the SambVca program to calculate the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts includes: The SambVca program was used to calculate the buried volume percentage and spatial topography of different iridium / phosphine ligand catalysts. By comparing the buried volumes of different ligands, the stability and reaction activity of the complexes were predicted and explained.
7. An iridium / phosphine ligand catalyst, characterized in that The general structural formula of the iridium / phosphine ligand catalyst is [Ir(CO)I2L] - .