Method for predicting intermiscibility of single-component pentaerythritol ester and refrigerant
By constructing a three-dimensional molecular structure model and a quantum chemical parameter prediction model for a single-component pentaerythritol ester, the problem of low efficiency in predicting the compatibility of polyol esters with hydrofluorocarbon refrigerants was solved, achieving efficient and accurate compatibility prediction and molecular design optimization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-10
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies struggle to efficiently predict the compatibility of polyol esters with hydrofluorocarbon refrigerants using molecular structure information, resulting in low R&D efficiency and high costs, and an inability to cope with changes in refrigerant types.
By constructing a three-dimensional molecular structure model of a single-component pentaerythritol ester, calculating key molecular properties, and using quantum chemical parameters to construct a predictive model, a compatibility prediction method was established in conjunction with experimental data.
It improves the accuracy and efficiency of compatibility prediction, reduces experimental workload, lowers R&D costs, optimizes molecular design, and shortens the R&D cycle.
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Figure CN121838896A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of refrigeration oil technology, and more specifically to a method for predicting the compatibility of a single-component pentaerythritol ester with a refrigerant. Background Technology
[0002] In the air conditioning and other refrigeration compressor industries, with increasing environmental awareness, chlorinated refrigerants (such as R22) are gradually being phased out, replaced by third-generation hydrofluorocarbon (HFC) refrigerants considered more ideal, such as R134a, R410A, R407C, and R32. A significant characteristic of these new refrigerants is their much higher molecular polarity compared to previous HFC refrigerants. However, this enhanced polarity makes them immiscible with traditional mineral oils (such as naphthenic oils and white oils) and some synthetic oils (such as PAO and alkylbenzenes). Refrigerant compatibility is a crucial technical indicator for refrigeration oils; a lack of compatibility means that existing mineral oil-based refrigeration oils cannot be used in HFC refrigeration systems. Therefore, polyol esters, due to their high polarity, exhibit good compatibility with HFC refrigerants and have become one of the most suitable refrigeration oils for HFC refrigerants.
[0003] Nevertheless, the compatibility of polyol esters with hydrofluorocarbon refrigerants is strongly dependent on their molecular structure. For example, pentaerythritol and dipentaerythritol have four and six reaction sites, respectively, and the saturated fatty acids they esterify can vary in carbon chain length from C5 to C18, and can be either straight-chain or branched. To achieve ideal viscosity and pour point properties, at least two or more types of fatty acids are usually required for esterification. Different fatty acid types and their mixing ratios can create an extremely wide range of structural schemes. Therefore, designing and developing polyol esters with good compatibility with specific hydrofluorocarbon refrigerants is a complex task. Traditional experience-based and trial-and-error R&D models are not only extremely labor-intensive, time-consuming, inefficient, and costly, but also heavily reliant on the experience of technical personnel. Furthermore, this approach cannot fully explain the relationship between the molecular structure of polyol esters and refrigerant compatibility at the molecular level, remaining only at the macroscopic empirical level. Once the type of refrigerant changes, previous technical experience and knowledge may become invalid or need to be rebuilt.
[0004] Therefore, predicting the compatibility of polyol esters with refrigerants using molecular structure information to provide precise guidance for research and development, reduce numerous trial-and-error experiments, and improve R&D efficiency is an urgent problem to be solved. Although there are existing technologies exploring the use of molecular structure information to predict lubricating oil properties, these methods are either computationally intensive and time-consuming, or their predictive effectiveness is limited by the quality and scale of the database, failing to deeply reveal the influence of molecular substructures or fine structures on overall properties. Currently, there is an urgent need for a method that can efficiently screen out the structures of single-component pentaerythritol esters with good compatibility with hydrofluorocarbon refrigerants. Summary of the Invention
[0005] The purpose of this invention is to provide a method for predicting the miscibility of single-component pentaerythritol esters with refrigerants. By calculating the molecular properties of single-component pentaerythritol esters, particularly those key properties affecting refrigerant miscibility, and combining these calculations with actual miscibility experimental data, a predictive model is constructed. This method helps to clarify the relationship between molecular structure and properties from a microscopic perspective, providing guidance for designing more efficient refrigeration oils.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for predicting the compatibility of a single-component pentaerythritol ester with a refrigerant includes the following steps:
[0008] S1: Obtain experimental data on the compatibility of pentaerythritol esters with different structures and refrigerants;
[0009] S2: Construct a three-dimensional molecular structure model of a single-component pentaerythritol ester, and perform geometric optimization and frequency analysis on the three-dimensional molecular structure model to obtain a thermodynamically stable three-dimensional molecular structure model of a single-component pentaerythritol ester.
[0010] S3: Based on the three-dimensional molecular structure model of the thermodynamically stable single-component pentaerythritol ester, calculate the molecular properties of the single-component pentaerythritol ester and screen and determine the key molecular properties that affect the compatibility of pentaerythritol ester with refrigerant.
[0011] S4: Determine the quantum chemical parameters of the carboxylic acid that makes up the single-component pentaerythritol ester. Construct a modeling dataset using the quantum chemical parameters of the carboxylic acid and the key molecular property data affecting the miscibility of pentaerythritol ester with the refrigerant determined in step S3. Divide the modeling dataset into a training set and a test set. Using the quantum chemical parameters of the carboxylic acid as input and the molecular properties of the corresponding single-component pentaerythritol ester as output, construct a molecular property prediction model for the single-component pentaerythritol ester using the training set. Test the molecular property prediction model using the test set and select the optimal prediction model.
[0012] S5: Use the prediction model to predict the molecular properties of the single-component pentaerythritol ester, and evaluate the compatibility of the single-component pentaerythritol ester with the refrigerant based on the molecular polarity index.
[0013] Further: In step S1, the experimental data on the compatibility of pentaerythritol esters with different structures and refrigerants are obtained, including: mixing pentaerythritol esters and refrigerants in a preset mass ratio and measuring the two-phase separation temperature of the mixture.
[0014] Furthermore, the preset mass ratio is 20% pentaerythritol ester and 80% refrigerant.
[0015] Furthermore, in step S2, the three-dimensional molecular structure model of the single-component pentaerythritol ester was constructed using GaussView software and exported in gjf format.
[0016] Furthermore, in step S2, the geometric structure optimization and frequency analysis of the three-dimensional molecular structure model are performed using Gaussian16 software and the M06 / 6-31G(d) theory method in density functional theory is adopted.
[0017] Furthermore, the criterion for determining that the molecular structure model is thermodynamically stable in step S2 is that all frequency values in the frequency analysis results are positive.
[0018] Furthermore, the molecular properties of the single-component pentaerythritol ester calculated in step S3 include one or more combinations of dipole moment, polarizability, quadrupole moment, electrostatic potential, and molecular polarity index.
[0019] Further: The method for screening and determining the key molecular properties that affect the compatibility of pentaerythritol ester with refrigerant in step S3 is as follows: calculate the correlation coefficient between different molecular properties and refrigerant compatibility, and select the property with the largest correlation coefficient as the evaluation index for evaluating the compatibility of pentaerythritol ester with refrigerant.
[0020] Further: In step S4, determining the quantum chemical parameter values of the raw material carboxylic acid that constitutes the single-component pentaerythritol ester includes: calculating the dipole moment and polarizability of the raw material carboxylic acid.
[0021] Further: Step S5 specifically includes:
[0022] S501: Calculate the quantum chemical parameters of the carboxylic acid raw material for the single-component pentaerythritol ester to be predicted;
[0023] S502: Input the quantum chemical parameter values of the raw material carboxylic acid described in step S501 into the prediction model constructed in step S4 to obtain the molecular polarity index of the single component pentaerythritol ester to be predicted, and evaluate the compatibility of the single component pentaerythritol ester with the refrigerant based on the molecular polarity index.
[0024] Compared with the prior art, the present invention has the following advantages:
[0025] I. Improved Prediction Efficiency: This invention, by establishing a predictive model, can rapidly predict the compatibility of single-component pentaerythritol esters with different structures and refrigerants, significantly reducing the workload of artificial synthesis and testing. This method greatly improves prediction efficiency and helps accelerate the research and development process of pentaerythritol ester base oils for refrigeration oils.
[0026] II. Reduced R&D Costs: Since this method can predict the compatibility of single-component pentaerythritol esters with refrigerants before actual synthesis, it can effectively reduce unnecessary experiments, thereby saving manpower and resources, shortening the R&D cycle, and significantly reducing R&D costs.
[0027] III. Deepening the understanding at the molecular level: This invention screens key factors affecting the compatibility of single-component pentaerythritol esters with refrigerants and establishes a predictive model by correlating the structure of single-component pentaerythritol esters with their corresponding properties. This helps to clarify the structure-property relationship between the structure and molecular properties of single-component pentaerythritol esters at the microscopic molecular level, providing scientific guidance for the design of polyol ester base oils for refrigeration oils.
[0028] IV. Improved Prediction Accuracy: This method combines quantum chemical calculations and experimental data to construct a prediction model based on the quantum chemical parameters of the raw material carboxylic acid, which can more accurately predict the molecular properties of single-component pentaerythritol esters, thereby improving the accuracy of compatibility prediction.
[0029] V. Optimization of Molecular Design: This method allows researchers to evaluate the compatibility of single-component pentaerythritol esters with refrigerants at the molecular design stage, thereby optimizing molecular design and improving the development efficiency of new refrigeration oils. Attached Figure Description
[0030] Figure 1 This is a flowchart of a method for predicting the compatibility of a single-component pentaerythritol ester with a refrigerant in one embodiment of the present invention;
[0031] Figure 2 This is a schematic diagram of the molecular structure of pentaerythritol ester according to an embodiment of the present invention. In the figure, acid1, acid2, acid3, and acid4 represent different carboxylic acid groups, and R1, R2, R2, and R4 represent the alkyl carbon chains of different carboxylic acid groups.
[0032] Figure 3 The graph shows the linear correlation between the miscibility temperature of the three pentaerythritol esters with R134a refrigerant and the molecular polarity index.
[0033] Figure 4This is a graph showing the linear correlation between the predicted and actual values of a molecular polarity prediction model according to an embodiment of the present invention on the training set.
[0034] Figure 5 This is a graph showing the linear correlation between the predicted and actual values of a molecular polarity prediction model according to an embodiment of the present invention on a test set. Detailed Implementation
[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0037] like Figure 1 As shown, a method for predicting the compatibility of a single-component pentaerythritol ester with a refrigerant includes the following steps:
[0038] S1: Obtain experimental data on the compatibility of pentaerythritol esters with different structures and refrigerants.
[0039] In some embodiments, obtaining the compatibility experimental data of pentaerythritol esters with different structures and refrigerants in step S1 includes: mixing pentaerythritol esters and refrigerants in a preset mass ratio and measuring the two-phase separation temperature of the mixture.
[0040] In this embodiment, pure pentaerythritol tetraisohexanoate, pentaerythritol tetraisooctanoate, and pentaerythritol tetranonoctanoate were obtained through experimental separation. The molecular structure diagrams are shown below. Figure 2As shown. According to the petrochemical industry standard SH / T 0699-2000 "Test Method for Compatibility of Refrigeration Oils with Refrigerants", the two-phase separation temperatures of pentaerythritol tetraisohexanoate, pentaerythritol tetraisooctanoate, and pentaerythritol tetraisonononate with refrigerant R134a were measured at a ratio of 20% ester and 80% R134a: -75℃, -11℃, and -19℃, respectively. This preset mass ratio (20% single-component pentaerythritol ester and 80% refrigerant) can effectively reflect the working conditions of refrigeration oils in actual applications.
[0041] S2: Construct a three-dimensional molecular structure model of a single-component pentaerythritol ester, and perform geometric optimization and frequency analysis on the three-dimensional molecular structure model to obtain a thermodynamically stable three-dimensional molecular structure model of a single-component pentaerythritol ester.
[0042] In some embodiments: the three-dimensional molecular structure model of the single-component pentaerythritol ester in step S2 is constructed using GaussView software and exported in gjf format. Geometric optimization and frequency analysis of the three-dimensional molecular structure model are performed using Gaussian16 software, employing the M06 / 6-31G(d) theory method from density functional theory.
[0043] In this process, when all frequency values in the frequency analysis results are positive, the molecular structure model can be determined to be a thermodynamically stable molecular structure model. This step ensures the accuracy of subsequent calculations.
[0044] S3: Based on the three-dimensional molecular structure model of the thermodynamically stable single-component pentaerythritol ester, calculate the molecular properties of the single-component pentaerythritol ester and screen and determine the key molecular properties that affect the compatibility of pentaerythritol ester with refrigerant.
[0045] In some embodiments: the molecular properties of single-component pentaerythritol ester calculated in step S3 include one or more combinations of dipole moment, polarizability, quadrupole moment, electrostatic potential, and molecular polarity index; the method for screening and determining the key molecular properties affecting the compatibility of pentaerythritol ester with refrigerant is as follows: calculate the correlation coefficient between different molecular properties and refrigerant compatibility, and select the property with the largest correlation coefficient as the evaluation index for evaluating the compatibility of pentaerythritol ester with refrigerant.
[0046] In this embodiment, the molecular polarity index (MPI) is selected as an indicator to measure the compatibility of the single-component pentaerythritol ester with the refrigerant. The molecular polarity index can be understood as the average absolute value of the electrostatic potential of the molecular surface, which can better reflect the non-uniformity of the molecular charge distribution. The higher the value, the stronger the molecular polarity. Figure 3The graph shows the linear correlation between the miscibility temperature of three pentaerythritol esters and refrigerant R134a and their molecular polarity indices. The calculation results show that the molecular polarity indices of pentaerythritol tetraisohexanoate, pentaerythritol tetraisooctanoate, and pentaerythritol tetraisonononate are 5.95 kcal / mol, 4.72 kcal / mol, and 5.56 kcal / mol, respectively. The calculated molecular polarity indices are consistent with the solubility trend; the larger the molecular polarity index, the better the solubility with the refrigerant.
[0047] S4: Determine the quantum chemical parameters of the carboxylic acid that makes up the single-component pentaerythritol ester. Construct a modeling dataset using the quantum chemical parameters of the carboxylic acid and the key molecular property data affecting the miscibility of pentaerythritol ester with the refrigerant determined in step S3. Divide the modeling dataset into a training set and a test set. Using the quantum chemical parameters of the carboxylic acid as input and the molecular properties of the corresponding single-component pentaerythritol ester as output, construct a molecular property prediction model for the single-component pentaerythritol ester using the training set. Test the molecular property prediction model using the test set and select the optimal prediction model.
[0048] In this embodiment, 11 carboxylic acids, including 2-methylpropionic acid, 2,2-dimethylpropionic acid, 3-methylbutyric acid, 4-methylvaleric acid, 2-ethylhexanoic acid, 3,5,5-trimethylhexanoic acid, n-butyric acid, n-valeric acid, n-hexanoic acid, n-octanoic acid, and n-nonanoic acid, were used as the basic raw materials for pentaerythritol esters. Through permutations and combinations, 196 pentaerythritol ester molecules were constructed. 126 single-component pentaerythritol ester molecules were collected as training set samples, and 70 single-component pentaerythritol ester molecules were collected as test set samples. A multiple linear regression model was constructed based on the collected data. During the modeling process, the types of carboxylic acids constituting single-component pentaerythritol esters were selected as features to distinguish different single-component pentaerythritol esters. The dipole moment and polarizability of each raw material carboxylic acid were calculated, and the dipole moment and polarizability of the carboxylic acids were correlated with the properties of pentaerythritol esters to construct a predictive model. The fitting results of the model on the training and test sets are as follows: Figure 4 and Figure 5 As shown, by appendix Figure 4 and attached Figure 5 It can be seen that the model's predicted values are in good agreement with the actual values, with a coefficient of determination R² exceeding 0.9, and the mean absolute error is less than 0.5 kcal / mol, indicating a small error.
[0049] S5: Use the prediction model to predict the molecular properties of the single-component pentaerythritol ester, and evaluate the compatibility of the single-component pentaerythritol ester with the refrigerant based on the molecular polarity index.
[0050] In some embodiments, step S5 specifically includes:
[0051] S501: Calculate the quantum chemical parameters of the carboxylic acid raw material for the single-component pentaerythritol ester to be predicted;
[0052] S502: Input the quantum chemical parameter values of the raw material carboxylic acid described in step S501 into the prediction model constructed in step S4 to obtain the molecular polarity index of the single component pentaerythritol ester to be predicted, and evaluate the compatibility of the single component pentaerythritol ester with the refrigerant based on the molecular polarity index.
[0053] Among them, the quantum chemical parameter values in S501 can be dipole moment and polarizability.
[0054] like Figure 5 As shown, to verify the effectiveness of this method, we used the model to predict the molecular polarity indices of pentaerythritol tetraisohexanoate, pentaerythritol tetraisooctanoate, and pentaerythritol tetraisonononate. The model-predicted values were 6.01 kcal / mol, 4.84 kcal / mol, and 5.35 kcal / mol, respectively, while the actual calculated values were 5.95 kcal / mol, 4.72 kcal / mol, and 5.56 kcal / mol, respectively. This indicates that the molecular polarity index values predicted by the model are in high agreement with the actual calculated values. Furthermore, the molecular polarity index shows a consistent trend with refrigerant miscibility; the larger the molecular polarity index, the better the miscibility with the refrigerant. This demonstrates that the method of this invention can effectively predict the miscibility of single-component pentaerythritol esters with refrigerants.
[0055] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for predicting the compatibility of a single component pentaerythritol ester with a refrigerant, characterized by, The method comprises the following steps: S1: obtaining experimental data of the phase solubility of single-component pentaerythritol esters with refrigerants; S2: constructing a three-dimensional molecular structure model of the single-component pentaerythritol ester, and performing geometric structure optimization and frequency analysis on the three-dimensional molecular structure model to obtain a three-dimensional molecular structure model of the thermodynamically stable single-component pentaerythritol ester; S3: based on the three-dimensional molecular structure model of the thermodynamically stable single-component pentaerythritol ester, calculating the molecular properties of the single-component pentaerythritol ester, and determining the key molecular properties affecting the phase solubility of the pentaerythritol ester and the refrigerant; S4: determining the quantum chemical parameter value of the raw material carboxylic acid constituting the single-component pentaerythritol ester, and constructing a modeling data set with the quantum chemical parameter value of the raw material carboxylic acid and the key molecular property data determined in step S3 affecting the phase solubility of the pentaerythritol ester and the refrigerant; dividing the modeling data set into a training set and a test set; constructing a single-component pentaerythritol ester molecular property prediction model with the quantum chemical parameter value of the raw material carboxylic acid as input and the molecular properties of the single-component pentaerythritol ester corresponding to the composition as output; training the single-component pentaerythritol ester molecular property prediction model using the training set, testing the single-component pentaerythritol ester molecular property prediction model using the test set, and selecting the optimal prediction model; S5: applying the optimal prediction model to predict the molecular properties of the single-component pentaerythritol ester, and evaluating the phase solubility of the single-component pentaerythritol ester and the refrigerant according to the molecular polarity index.
2. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, characterized in that, In step S1, the experimental data of the phase solubility of single-component pentaerythritol esters with refrigerants is obtained by mixing single-component pentaerythritol esters and refrigerants in a predetermined mass ratio, and measuring the two-phase separation temperature of the mixture.
3. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 2, characterized in that, The predetermined mass ratio is 20% single-component pentaerythritol ester and 80% refrigerant.
4. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, characterized in that, In step S2, the three-dimensional molecular structure model of the single-component pentaerythritol ester is constructed using GaussView software and exported in gjf format.
5. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein In step S2, the geometric structure optimization and frequency analysis of the three-dimensional molecular structure model are performed using Gaussian16 software and the theoretical method in the density functional theory.
6. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein In step S2, the standard for determining that the molecular structure model is thermodynamically stable is that the frequency values in the frequency analysis results are all positive.
7. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein In step S3, the calculated single-component pentaerythritol ester molecular properties include one or more combinations of dipole moment, polarizability, quadrupole moment, electrostatic potential, and molecular polarity index.
8. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein In step S3, the method for determining the key molecular properties affecting the phase solubility of the pentaerythritol ester and the refrigerant is to calculate the correlation coefficients of different molecular properties and the phase solubility of the refrigerant, and select the property with the largest correlation coefficient as the evaluation index for evaluating the phase solubility of the pentaerythritol ester and the refrigerant.
9. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein In step S4, the quantum chemical parameter value of the raw material carboxylic acid constituting the single-component pentaerythritol ester includes calculating the dipole moment and polarizability of the raw material carboxylic acid.
10. The method of predicting the refrigerant compatibility of a single component pentaerythritol ester according to claim 1, wherein Step S5 specifically includes: S501: calculating the quantum chemical parameter value of the raw material carboxylic acid of the single-component pentaerythritol ester to be predicted; S502: input the quantum chemistry parameter value of the raw material carboxylic acid calculated in step S501 into the prediction model constructed in step S4, obtain the single-component pentaerythritol ester molecule polarity index to be predicted, and evaluate the compatibility of the single-component pentaerythritol ester with the refrigerant according to the single-component pentaerythritol ester molecule polarity index.