A method for calculating the viscosity index of lubricating oil base oil

Abstract

The present invention relates to a method for calculating the viscosity index of lubricating oil base oil: high-resolution mass spectrometry and nuclear magnetic resonance are respectively used to analyze the lubricating oil base oil to be measured, obtaining the carbon atom number distribution information and the average carbon atom number information, and determining the molecular structure information of the lubricating oil base oil to be measured according to the obtained information; for each component in the lubricating oil base oil to be measured: according to the molecular structure information and the group contribution method, the viscosities of each component i in the lubricating oil base oil to be measured at 40 °C and 100 °C are respectively determined; according to the molecular composition of the lubricating oil base oil to be measured, the blending correction method is used to calculate the viscosities of the lubricating oil base oil to be measured at 40 °C and 100 °C; the viscosity index VI of the lubricating oil base oil to be measured is calculated according to and. The present invention establishes a calculation method for the viscosity and viscosity index of base oil based on molecular composition, and can calculate relatively accurate viscosity and viscosity index.

Description

Technical Field

[0001] The present invention relates to a method for calculating the viscosity index of lubricating oil base oil. Background Art

[0002] API Group III base oils belong to high-grade base oils, with a VI value greater than 120 and a pour point lower than -18°C. The main production process of API Group III base oils is the full-hydrogenation process of hydrocracking-hydroisomerization using mineral oil as raw material, and the isodewaxing and pour point reduction process is the focus of development and research.

[0003] In order to deeply study the influence of the hydroisomerization process on the viscosity index of base oils, usually the feedstock oil and the base oil are cut into narrow fractions by true boiling point distillation, and the narrow fractions are analyzed by mass spectrometry (MS) to obtain the contents of paraffins, naphthenes with different ring numbers, and alkylbenzenes, so as to understand the changes in the narrow fraction VI and hydrocarbon content of the feedstock oil and the base oil, and thus infer the reaction conditions. However, the changes of various hydrocarbon compounds during the conversion process and the quantitative contribution of such changes to the viscosity index cannot be understood; sometimes, a correlation relationship between the final boiling point of the narrow fraction and the VI is also established, but this correlation is interfered by the difference in hydrocarbon content. After all, the final boiling point is only one of the macroscopic manifestations of the molecular composition of the narrow fraction. The determination of nuclear magnetic resonance (NMR) can obtain information on the degree of isomerization and the average number of carbon atoms in the composition of the base oil. When studying the influence of this on the VI as a criterion, a phenomenon may occur: the influence of the average number of carbon atoms on the VI conflicts with the result of the influence of the paraffin content on the VI. In recent years, gas chromatography-field ionization / time-of-flight mass spectrometry (GC-FI / TOF MS) has been applied to the high-resolution mass spectrometry analysis of base oil samples, and the carbon atom number distribution information of paraffins and naphthenes with different ring numbers can be obtained. From the rich information of the carbon atom number, the average number of carbon atoms of paraffins and the side chains of naphthenes can be respectively understood. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for calculating the viscosity index of lubricating oil base oil, which can realize the prediction and calculation of the viscosity and viscosity index of lubricating oil base oil based on the molecular composition, and the accuracy of the calculated viscosity and viscosity index is high.

[0005] In order to achieve the above purpose, the present invention provides a method for calculating the viscosity index of lubricating oil base oil, which includes:

[0006] Analyze the lubricating oil base oil to be measured by high-resolution mass spectrometry and nuclear magnetic resonance respectively to obtain the carbon atom number distribution information and the average carbon atom number information;

[0007] Determine the molecular structure information of the lubricating oil base oil to be measured according to the carbon atom number distribution information and the average carbon atom number information;

[0008] - The carbon atom number distribution information is the carbon atom distribution information of high-resolution mass spectrometry, and the average carbon atom number information is the carbon atom distribution information of nuclear magnetic resonance;

[0009] - The molecular structure information includes: the number of branched chains of alkanes, the number of side chains and the number of branched chains on the side chains of monocyclic cycloalkanes, the number of side chains and the number of branched chains on the side chains of bicyclic cycloalkanes, the number of side chains and the number of branched chains on the side chains of tricyclic cycloalkanes, the number of side chains and the number of branched chains on the side chains of tetracyclic cycloalkanes, the number of side chains and the number of branched chains on the side chains of pentacyclic cycloalkanes;

[0010] For each component in the lubricating oil base oil to be measured: according to the molecular structure information, the viscosity v of component i at 40 °C is determined respectively i,40℃ and the viscosity v at 100 °C i,100℃ ;

[0011] According to the molecular composition of the lubricating oil base oil to be measured, the viscosity v of the lubricating oil base oil to be measured at 40 °C is calculated respectively by formula (1) and formula (2) mix,40℃ and the viscosity v at 100 °C mix,100℃ ,

[0012]

[0013]

[0014] - In formula (1) and formula (2), x i is the mole fraction of component i in the lubricating oil base oil to be measured; k i is the blending factor of component i, i is any integer from 1 to m, and m is the number of components in the lubricating oil base oil to be measured;

[0015] The viscosity index VI of the lubricating oil base oil to be measured is calculated according to formula (3) and formula (4),

[0016]

[0017]

[0018] - Wherein, H is the viscosity of the reference oil sample at 40 °C, and the unit is mm 2 / s; U is the viscosity v of the lubricating oil base oil to be measured at 40 °C mix,40℃ , and the unit is mm 2 / s; Y is the viscosity v of the lubricating oil base oil to be measured at 100 °C mix,100℃ , and the unit is mm 2 / s.

[0019] Through the above technical solution, according to the complementary characteristics of the structural information provided by nuclear magnetic resonance and high-resolution mass spectrometry, by integrating and analyzing the measurement results of the two, the blending correction method is used to calculate the viscosity and viscosity index of the lubricating oil base oil, and the obtained results are relatively accurate.

[0020] Other features and advantages of the present invention will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings:

[0022] Figure 1 is a distribution diagram of the content of alkanes in samples B1 and B2 in Example 1 of the present invention with respect to the number of carbon atoms;

[0023] Figure 2 is a comparison diagram of the calculated values and measured values of the 100 °C viscosity of samples B1 and B2 obtained by using different methods in Example 2 and Example 3 of the present invention;

[0024] Figure 3 is a comparison diagram of the calculated values and measured values of the 40 °C viscosity of samples B1 and B2 obtained by using different methods in Example 2 and Example 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not used to limit the present invention.

[0026] The present invention provides a method for calculating the viscosity index of a lubricating oil base oil, the method comprising:

[0027] Analyzing the lubricating oil base oil to be measured by using high-resolution mass spectrometry and nuclear magnetic resonance respectively to obtain the carbon atom number distribution information and the average carbon atom number information;

[0028] Determining the molecular structure information of the lubricating oil base oil to be measured according to the carbon atom number distribution information and the average carbon atom number information, and establishing a molecular-level composition model for this type of oil product;

[0029] -- The carbon atom number distribution information is the carbon atom distribution information of the high-resolution mass spectrometry, and the average carbon atom number information is the carbon atom distribution information of the nuclear magnetic resonance;

[0030] --The molecular structure information includes: the number of side chains of alkanes, the number of side chains and the number of branched chains on the side chains of monocyclic naphthenes, the number of side chains and the number of branched chains on the side chains of bicyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tricyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tetracyclic naphthenes, and the number of side chains and the number of branched chains on the side chains of pentacyclic naphthenes;

[0031] For each component in the lubricating oil base oil to be measured: according to the molecular structure information, determine the viscosity v of component i at 40 °C i,40℃ and the viscosity v at 100 °C i,100℃ ;

[0032] According to the molecular composition of the lubricating oil base oil to be measured, use Equation (1) and Equation (2) to calculate the viscosity v of the lubricating oil base oil to be measured at 40 °C mix,40℃ and the viscosity v at 100 °C mix,100℃ ,

[0033]

[0034]

[0035] --In Equation (1) and Equation (2), x i is the mole fraction of component i in the lubricating oil base oil to be measured; k i is the blending factor of component i, where i is any integer from 1 to m, and m is the number of components in the lubricating oil base oil to be measured;

[0036] Calculate the viscosity index VI of the lubricating oil base oil to be measured according to Equation (3) and Equation (4),

[0037]

[0038]

[0039] --where H is the viscosity of the reference oil sample at 40 °C, with the unit of mm 2 / s; U is the viscosity v of the lubricating oil base oil to be measured at 40 °C mix,40℃ , with the unit of mm 2 / s; Y is the viscosity v of the lubricating oil base oil to be measured at 100 °C mix,100℃ , with the unit of mm 2 / s.

[0040] Among them, the reference oil sample refers to the oil sample with the same viscosity at 100 °C as the lubricating oil base oil to be measured in the query table of GB / T 2541-1981.

[0041] The viscosity and viscosity-temperature index of lubricating base oil are closely related to the number of branches of isoparaffins and the number of branches of long side chains of naphthenes in the base oil, and this information cannot be directly obtained from the results of individual high-resolution mass spectrometry and individual nuclear magnetic resonance analysis. The present invention integrates and analyzes the test results of nuclear magnetic resonance analysis and high-resolution mass spectrometry of the lubricating base oil to be tested, and estimates the viscosity and viscosity index of the base oil through a molecular information management method, which is conducive to assisting in understanding the real chemical conversion process. Compared with the existing blending index method and linear addition method, the viscosity calculated by the blending correction method of the present invention is more accurate and closer to the viscosity value obtained by actual measurement, and the viscosity index calculated thereby is also relatively accurate.

[0042] According to the present invention, the method of analyzing lubricating base oil by high-resolution mass spectrometry and nuclear magnetic resonance is well-known to those skilled in the art and will not be elaborated here. The lubricating base oil can be the lubricating base oil produced from the hydroisomerization dewaxing process.

[0043] In a specific embodiment of the present invention, according to the carbon atom number distribution information and the average carbon atom number information, the molecular structure information of the lubricating base oil to be tested is determined, including:

[0044] According to the carbon atom number distribution information, the average carbon atom number CP of paraffins, the average carbon atom number CscN1 of the side chains of monocyclic naphthenes, the average carbon atom number CscN2 of the side chains of bicyclic naphthenes, the average carbon atom number CscN3 of the side chains of tricyclic naphthenes, the average carbon atom number CscN4 of the side chains of tetracyclic naphthenes, and the average carbon atom number CscN5 of the side chains of pentacyclic naphthenes in the lubricating base oil to be tested are determined. Exemplarily, a fitted curve is obtained by fitting the hydrocarbon type carbon number distribution measured by high-resolution mass spectrometry, and the average carbon atom number of paraffins and the average carbon atom number of naphthene side chains can be calculated according to the fitted statistical distribution curve.

[0045] The average carbon atom number information may include the terminal methyl carbon ratio the naphthene carbon ratio the paraffin carbon ratio the normal paraffin carbon ratio the isoparaffin carbon ratio and the branched chain terminal methyl carbon ratio etc. In order to obtain the number of side chains of naphthenes, according to the average carbon atom number information, the formula (5) is used to calculate the average terminal methyl number ntX of monocyclic naphthenes, bicyclic naphthenes, tricyclic naphthenes, tetracyclic naphthenes, and pentacyclic naphthenes respectively; in the formula (5), CscNX is the average carbon atom number of the naphthene side chain, and X is an integer from 1 to 5, representing the number of rings of the naphthene; f Ct is the terminal methyl carbon ratio; is the paraffin carbon ratio. Exemplarily, the average terminal methyl number of monocyclic naphthenes Average number of terminal methyl groups of bicyclic cycloalkanes

[0046] Based on the average number of terminal methyl groups ntX of monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes and pentacyclic cycloalkanes obtained from the above calculations, the number of side chains of monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes and pentacyclic cycloalkanes is determined.

[0047] In a specific embodiment, when ntX is 1.2 or less, the number of side chains is 1; when ntX is greater than 1.2 and 1.8 or less, the number of side chains is 1 and 2; when ntX is greater than 1.8 and 2.3 or less, the number of side chains is 2; when ntX is greater than 2.3 and 2.8 or less, the number of side chains is 2 and 3; when ntX is greater than 2.8, the number of side chains is 3. Among them, the number of side chains being 1 means that the structure of the corresponding compound when calculating the average number of terminal methyl groups ntX has one molecular structure, and this molecular structure has 1 side chain; the number of side chains being 1 and 2 means that the compound corresponding to calculating the average number of terminal methyl groups ntX has two molecular structures, one molecular structure has 1 side chain, and the other molecular structure has 2 side chains; the number of side chains being 2 and 3 means that the compound corresponding to calculating the average number of terminal methyl groups ntX has two molecular structures, one molecular structure has 2 side chains, and the other molecular structure has 3 side chains.

[0048] Exemplarily, the average number of terminal methyl groups ntX of monocyclic cycloalkanes is calculated to be 2.27, and the monocyclic cycloalkanes can be represented by one molecular structure, and this molecular structure has 2 side chains; the average number of terminal methyl groups ntX of the calculated tricyclic cycloalkanes is 1.56, and the tricyclic cycloalkanes can be represented by two molecular structures, one molecular structure has 1 side chain, and the other molecular structure has 2 side chains.

[0049] In order to determine the number of branched chains of alkanes and the number of branched chains on the side chains of cycloalkanes, according to the average number of carbon atoms CP of alkanes, the average number of carbon atoms CscNX of the side chains of monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes and pentacyclic cycloalkanes, and the branched-chain terminal methyl carbon ratio and the alkane carbon ratio The ratio is used to determine the number of branched chains of alkanes, monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes and pentacyclic cycloalkanes respectively.

[0050] In a specific embodiment, the formula (6) "Number of branched chains of alkanes " is used to calculate the theoretical number of branched chains of alkanes; the formula (7) "Number of branched chains of cycloalkanes ”Calculate the theoretical number of branched chains of monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes, and pentacyclic cycloalkanes respectively, where X in CscNX is an integer from 1 to 5, representing the number of rings of the cycloalkane; determine the number of branched chains of alkanes, monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes, and pentacyclic cycloalkanes according to the theoretical number of branched chains.

[0051] Further, determining the number of branched chains of alkanes, monocyclic cycloalkanes, bicyclic cycloalkanes, tricyclic cycloalkanes, tetracyclic cycloalkanes, and pentacyclic cycloalkanes according to the theoretical number of branched chains includes: when nb is below 1.2, the number of branched chains is 1; when nb is greater than 1.2 and below 1.8, the number of branched chains is 1 and 2; when nb is greater than 1.8 and below 2.2, the number of branched chains is 2; when nb is greater than 2.2 and below 2.8, the number of branched chains is 2 and 3; when nb is greater than 2.8, the number of branched chains is 3. Among them, the number of branched chains being 1 means that there is one molecular structure in the structure of the corresponding compound when calculating the theoretical number of branched chains, and there is 1 branched chain in this molecular structure; the number of branched chains being 1 and 2 means that the corresponding compound when calculating the theoretical number of branched chains has two molecular structures, one molecular structure has 1 branched chain, and the other molecular structure has 2 branched chains; the number of branched chains being 2 and 3 means that the corresponding compound when calculating the theoretical number of branched chains has two molecular structures, one molecular structure has 2 branched chains, and the other molecular structure has 3 branched chains.

[0052] Exemplarily, the calculated theoretical number of branched chains nb of monocyclic cycloalkanes is 2.26, and monocyclic cycloalkanes can be represented by two molecular structures, one molecular structure has 2 branched chains, and the other molecular structure has 3 branched chains; the calculated theoretical number of branched chains nb of bicyclic cycloalkanes is 2.02, and bicyclic cycloalkanes can be represented by one molecular structure, and this molecular structure has 2 branched chains.

[0053] In a specific embodiment, the average number of terminal methyl groups ntX of alkanes can be calculated by formula (5), and the number of alkyl branches with ethyl branches and above that alkanes may contain is determined from the average number of terminal methyl groups ntX. Further, subtract 2 from ntX to remove the 2 true terminal methyl groups in the alkane, and the remaining is the number of non-methyl branches of the alkane. Combine the average number of terminal methyl groups ntX of the alkane with the number of branched chains nb of the alkane to further determine the number of branched chains and the number of carbon atoms of the branched chains of the alkane.

[0054] By combining and analyzing the carbon atom number distribution information and the average carbon atom number information as described above, the number of branched chains of paraffins, the number of side chains and the number of branched chains on the side chains of monocyclic naphthenes, the number of side chains and the number of branched chains on the side chains of bicyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tricyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tetracyclic naphthenes, and the number of side chains and the number of branched chains on the side chains of pentacyclic naphthenes in the lubricating oil base oil can be obtained. From this, the molecular structure information of the lubricating oil base oil to be tested can be determined, which is beneficial to improving the accuracy of estimating the viscosity and viscosity index of the lubricating oil base oil.

[0055] In one embodiment, according to the molecular structure information, the viscosity v of component i of the lubricating oil base oil to be tested at 40 °C is determined i,40℃ and the viscosity v of component i at 100 °C i,100℃ may include: calculating the viscosities of component i at 100 °C, 80 °C and 60 °C by using the group contribution method, and fitting and extrapolating according to the viscosities of component i at 100 °C, 80 °C and 60 °C to obtain the viscosity of component i at 40 °C; the group contribution method includes Rarey's group contribution method, Joback group contribution method or van group contribution method, preferably Rarey's group contribution method. The method of fitting and extrapolating is well known to those skilled in the art. Exemplarily, the viscosity of component i at 40 °C can be obtained according to v = aT b and the viscosities of component i at 100 °C, 80 °C and 60 °C by fitting and extrapolating; wherein, T is the temperature, in °C, and v is the viscosity of component i, in mm 2 / s. In one embodiment, the viscosities of component i at 100 °C, 80 °C and 60 °C are substituted into v = aT b . After obtaining the values of parameters a and b by multiple linear fitting, the viscosity of component i at 40 °C is calculated.

[0056] In one embodiment, the blending factor k can be determined by the following steps i : k i is selected from the blending factor k' of isoparaffins, the blending factor k'' of monocyclic naphthenes, and the blending factor k''' of other naphthenes; according to Equation (1) or Equation (2) and at least 5 groups of known v mix , x i and v i , k', k'' and k''' are obtained by multiple linear fitting. Exemplarily, when component i is an isoparaffin, the blending factor k i is k'; when component i is a monocyclic naphthene, the blending factor k i is k''; when component i is other naphthenes, the blending factor k i is k'''.

[0057] In a specific embodiment, the method further includes: measuring the base oil of the lubricating oil to be tested by high-resolution mass spectrometry to obtain the molecular composition of the base oil of the lubricating oil to be tested.

[0058] In another specific embodiment, the method further includes: calculating the molecular composition of the base oil of the lubricating oil to be tested; further, based on the conventional properties such as the density and distillation range of the measured base oil, assuming that hydrocarbon compounds are continuously distributed with the carbon number, representing the molecular composition of the base oil with a statistical distribution function, and using the minimum difference between the physical properties calculated from the molecular composition and the measured physical properties as the objective function, optimizing and solving, and calculating the molecular composition of the base oil from the optimized statistical distribution parameter values.

[0059] According to the present invention, the difference between the calculated viscosity index VI and the measured viscosity index of the lubricating oil base oil can be 0.5 to 1.5 units.

[0060] In one embodiment, a plurality of typical samples of lubricating oil base oil are obtained; a hydrocarbon model compound library is established according to the molecular structure information of the typical samples of lubricating oil base oil, and the number of carbon atoms of the hydrocarbon model compounds in the hydrocarbon model compound library is C 18 ~C 38 , and the hydrocarbon model compounds include alkanes, monocyclic naphthenes, bicyclic naphthenes, tricyclic naphthenes, tetracyclic naphthenes and pentacyclic naphthenes; the viscosity v of each hydrocarbon model compound in the hydrocarbon model compound library at 40 °C is determined respectively j,40℃ and the viscosity v at 100 °C j,100℃ ; according to the viscosities of all the hydrocarbon model compounds at 40 °C and 100 °C, a viscosity database of the hydrocarbon model compounds is established. According to the molecular structure information, the viscosity v of the component i at 40 °C is determined respectively j,40℃ and the viscosity v at 100 °C j,100℃ may include: according to the viscosity database of the hydrocarbon model compounds, determining the viscosity v of the hydrocarbon components in the base oil of the lubricating oil to be tested at 40 °C mix,40℃ and the viscosity v at 100 °C mix,100℃ . By establishing the above database of hydrocarbon model compounds, the time for calculating viscosity and viscosity index can be effectively saved, and the calculation speed and accuracy can be improved.

[0061] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0062] Example 1

[0063] Samples B1 and B2 are respectively subjected to high-resolution mass spectrometry and nuclear magnetic resonance (NMR) analysis (B1 and B2 are two samples of lubricating oil base oil respectively), and the carbon atom distribution information of high-resolution mass spectrometry and the carbon atom distribution information of nuclear magnetic resonance are obtained (see Table 2).

[0064] The molecular structure information of lubricating base oil was obtained by the following method:

[0065] It can be seen from Figure 1 that the scatter points in the figure are measured values, and the continuous curve is the normal distribution curve fitted by the statistical distribution law. The carbon atom number distribution conforms to the statistical law of normal distribution (or Γ distribution). The average carbon atom number CP of paraffins, and the average carbon atom numbers CscN1 to CscN5 of the side chains of monocyclic naphthenes, bicyclic naphthenes, tricyclic naphthenes, tetracyclic naphthenes and pentacyclic naphthenes were calculated by successive statistical distributions, and the results are shown in Table 1.

[0066] Table 1 Statistical average carbon atom numbers of paraffin and naphthene side chains of each sample

[0067]

[0068] Table 2 Structure parameters obtained by nuclear magnetic resonance analysis

[0069]

[0070] Based on the average carbon atom number of the side chain, according to the formula and combined with the NMR measurement results shown in Table 2, the average number of terminal methyl groups of paraffins, monocyclic naphthenes, bicyclic naphthenes, tricyclic naphthenes, tetracyclic naphthenes and pentacyclic naphthenes, and the average number of terminal methyl groups ntX of paraffins were estimated, and the results are shown in Table 3. It can be seen from Table 3 that monocyclic naphthenes and bicyclic naphthenes have 2 side chains, tricyclic naphthenes may contain 1 - 2 side chains, and tetracyclic naphthenes and pentacyclic naphthenes have 1 side chain.

[0071] Table 3 Estimated values of the average number of terminal methyl groups ntX of each hydrocarbon

[0072]

[0073] Based on the average carbon atom number CP of paraffins and the average carbon atom numbers CscN1 to CscN5 of the naphthene side chains of each sample, as well as the branched chain terminal methyl carbon ratio and the paraffin carbon ratio ratio f Cb / f Cp , according to the formula: the theoretical number of branched chains of paraffins calculate the theoretical number of branched chains nb on paraffins; according to the formula: the theoretical number of branched chains of naphthenes calculate the theoretical number of branched chains nb on the naphthene side chains, and the results are shown in Table 4. According to the results in Table 4, the number of branched chains of paraffins in the lubricating base oil is 3, the number of branched chains of monocyclic naphthenes is 2 and 3, the number of side chain branches of bicyclic naphthenes is 2, the number of side chain branches of tricyclic naphthenes is 1 and 2, and the number of side chain branches of tetracyclic naphthenes and pentacyclic naphthenes is 1.

[0074] Table 4 Estimated values of the average number of branches \(n_b\)

[0075]

[0076] After integrating the obtained molecular structure information of the lubricating oil base oil, a hydrocarbon model compound library is obtained. The number of carbon atoms of the hydrocarbon model compounds in the hydrocarbon model compound library is \(C\) 18 ~\(C\) 38 .

[0077] A partial model compound set of the hydrocarbon model compound library (taking \(C\) 26 as an example) is listed in Table 5.

[0078] Table 5 Partial model compounds of the lubricating oil base oil and their viscosities

[0079]

[0080]

[0081] The viscosities of the hydrocarbon model compounds in the hydrocarbon model compound library at 100 °C, 80 °C and 60 °C are calculated by using Rarey's group contribution method. At the same time, the viscosity at 40 °C is extrapolated by fitting according to the formula \(v = aT\) b ; A viscosity database is established for the above hydrocarbon model compounds and the viscosities at the corresponding temperatures for easy reference in calculations.

[0082] The molecular composition of the lubricating oil base oil to be measured is measured by high-resolution mass spectrometry.

[0083] According to the viscosity database and the molecular composition of the lubricating oil base oil to be measured, the formulas and are used to calculate the viscosity \(v\) mix,40℃ of the lubricating oil base oil to be measured at 40 °C and the viscosity \(v\) mix,100℃ at 100 °C respectively; among them, the blending factor of isoparaffin is \(k' = 0.923\), the blending factor of monocyclic naphthene is \(k'' = 1.02\), and the blending factor of other naphthenes is \(k''' = 0.72\).

[0084] According to and the viscosity index VI of the lubricating oil base oil to be measured is calculated.

[0085] Example 2

[0086] (1) The composition of the hydrocarbon types of the lubricating oil base oil sample B1 distributed with the number of carbon atoms is analyzed by high-resolution mass spectrometry. The carbon number range is between \(C\) 18 ~\(C\) 38 .

[0087] (2) Call the viscosities v of each hydrocarbon model compound at 100 °C from the established viscosity database i,100℃ and the viscosity v at 40 °C i,40℃ ;

[0088] (3) Apply the blending correction relationships (1) and (2) to calculate the viscosities v of B1 at 100 °C respectively mix,100℃ to be 4.992 mm 2 / s, and the viscosity v at 40 °C mix,40℃ to be 25.66 mm 2 / s, with the measured values being 4.994 mm 2 / s and 25.58 mm 2 / s;

[0089] (4) Use equations (3) and (4) to calculate the viscosity index VI of base oil B1 to be 121.99, with the measured value being 123, and the difference between the calculated value and the measured value being 1 unit.

[0090] Among them, the results of calculating the viscosity and viscosity index of lubricating base oil sample B1 by different methods are as Figure 2 and Figure 3 shown. It can be seen from the figure that the viscosity calculated by the blending correction method of the present invention is more accurate than the viscosities calculated by the blending index method and the linear addition method in the prior art.

[0091] Example 3

[0092] (1) Analyze the composition of the hydrocarbon types of lubricating base oil sample B2 with the distribution of carbon atoms by high-resolution mass spectrometry, and the carbon number range is between C 18 and C 38 ;

[0093] (2) Call the viscosities v of each hydrocarbon model compound at 100 °C from the established viscosity database i,100℃ and the viscosity v at 40 °C i,40℃ ;

[0094] (3) Apply the blending correction relationships (1) and (2) to calculate the viscosities v of B2 at 100 °C respectively mix,100℃ to be 4.287 mm 2 / s, and the viscosity v at 40 °C mix,40℃ to be 20.14 mm 2 / s, with the measured values being 4.227 mm 2 / s and 20.06 mm 2 / s;

[0095] (4) Use equations (3) and (4) to calculate the viscosity index VI of base oil B2 to be 120.3, with the measured value being 120, and the difference between the calculated value and the measured value being less than 1 unit.

[0096] Among them, the results of calculating the viscosity and viscosity index of the lubricating base oil sample B2 by different methods are as Figure 2 and Figure 3 shown. It can be seen from the figure that the viscosity calculated by the blending correction method of the present invention is more accurate than the viscosities calculated by the blending index method and the linear summation method in the prior art.

[0097] The viscosities and viscosity indices of the lubricating base oil calculated by the method of the present invention have high accuracy.

[0098] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0099] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any suitable way without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0100] Furthermore, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for calculating the viscosity index of lubricating base oil, the method comprises: Analyzing the lubricating base oil to be tested by high-resolution mass spectrometry and nuclear magnetic resonance respectively to obtain the carbon atom number distribution information and the average carbon atom number information; The lubricating base oil to be tested is the lubricating base oil produced from the hydroisomerization dewaxing process; Determining the molecular structure information of the lubricating base oil to be tested according to the carbon atom number distribution information and the average carbon atom number information; -- The carbon atom number distribution information is the carbon atom number distribution information of high-resolution mass spectrometry, and the average carbon atom number information is the average carbon atom number information of nuclear magnetic resonance; -- The molecular structure information includes: the number of branched chains of paraffins, the number of side chains and the number of branched chains on the side chains of monocyclic naphthenes, the number of side chains and the number of branched chains on the side chains of bicyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tricyclic naphthenes, the number of side chains and the number of branched chains on the side chains of tetracyclic naphthenes, the number of side chains and the number of branched chains on the side chains of pentacyclic naphthenes; For each component in the lubricant base oil to be measured: According to the molecular structure information, the viscosity vi of component i at 40 °C and the viscosity vi at 100 °C are respectively determined. i,40℃ and the viscosity vi at 100 °C i,100℃ ; According to the molecular composition of the lubricating oil base oil to be measured, the viscosities v of the lubricating oil base oil to be measured at 40 °C and 100 °C are calculated respectively using formula (1) and formula (2). mix , 40℃ and the viscosity v at 100 °C mix , 100℃ , Formula (1), Formula (2), --In formulas (1) and (2), x i is the mole fraction of component i in the lubricating oil base oil to be measured; k i is the blending factor of component i, where i is any integer from 1 to m, and m is the number of components in the lubricating oil base oil to be measured; Calculating the viscosity index VI of the lubricating base oil to be tested according to formula (3) and formula (4), Formula (3), Equation (4), --where H is the viscosity of the reference oil sample at 40°C, with the unit of mm 2 / s; U is the viscosity v of the lubricating oil base oil to be measured at 40°C mix , 40℃ , with the unit of mm 2 / s; Y is the viscosity v of the lubricating oil base oil to be measured at 100°C mix , 100℃ , with the unit of mm 2 / s; Determine the blending factor k by the following steps i : k i The blending factor k' of isoparaffins, the blending factor k'' of monocyclic naphthenes, and the blending factor k''' of other naphthenes; according to formula (1) or formula (2) and at least 5 groups of known v mix , x i and v i , k', k'' and k''' are obtained by multiple linear fitting.

2. The method according to claim 1, wherein, The step of determining the molecular structure information of the lubricating base oil to be tested according to the carbon atom number distribution information and the average carbon atom number information includes: Determining the average carbon atom number CP of the paraffins, the average carbon atom number CscN1 of the side chains of monocyclic naphthenes, the average carbon atom number CscN2 of the side chains of bicyclic naphthenes, the average carbon atom number CscN3 of the side chains of tricyclic naphthenes, the average carbon atom number CscN4 of the side chains of tetracyclic naphthenes, and the average carbon atom number CscN5 of the side chains of pentacyclic naphthenes in the lubricating base oil to be tested according to the carbon atom number distribution information; Calculating the average number of terminal methyl groups ntX of the monocyclic naphthenes, the bicyclic naphthenes, the tricyclic naphthenes, the tetracyclic naphthenes and the pentacyclic naphthenes respectively according to the average carbon atom number information by using formula (5); ntX = CscNX × f C t / f C Equation (5), --Among them, CscNX is the average number of carbon atoms in the naphthene side chain, X is an integer from 1 to 5, representing the number of rings of the naphthene; f Ct is the terminal methyl carbon ratio; f C p is the paraffin carbon ratio; Determining the number of side chains of the monocyclic naphthenes, the bicyclic naphthenes, the tricyclic naphthenes, the tetracyclic naphthenes and the pentacyclic naphthenes respectively according to the average number of terminal methyl groups ntX of the paraffins, the monocyclic naphthenes, the bicyclic naphthenes, the tricyclic naphthenes, the tetracyclic naphthenes and the pentacyclic naphthenes; According to the average number of carbon atoms of the alkane, the average number of carbon atoms of the side chains of the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane, and the terminal methyl carbon ratio f C b of the branched chain and the alkane carbon ratio f C P ratio, respectively determine the number of branched chains of the alkane, the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane.

3. The method according to claim 2, wherein, The step of determining the number of side chains of the monocyclic naphthenes, the bicyclic naphthenes, the tricyclic naphthenes, the tetracyclic naphthenes and the pentacyclic naphthenes respectively according to the average number of terminal methyl groups ntX of the monocyclic naphthenes, the bicyclic naphthenes, the tricyclic naphthenes, the tetracyclic naphthenes and the pentacyclic naphthenes includes: When ntX is 1.2 or less, the number of side chains is 1; When ntX is greater than 1.2 and less than or equal to 1.8, the number of side chains is 1 and 2; When ntX is greater than 1.8 and less than or equal to 2.3, the number of side chains is 2; When ntX is greater than 2.3 and less than or equal to 2.8, the number of side chains is 2 and 3; When ntX is greater than 2.8, the number of side chains is 3.

4. The method according to claim 2, Among them, According to the average number of carbon atoms of the alkane, the average number of carbon atoms of the side chains of the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane, as well as the terminal methyl carbon ratio f C b and the alkane carbon ratio f C The ratios of P are used to respectively determine the number of branched chains of the alkane, the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane, including: the theoretical number of branched chains of the alkane is calculated using Equation (6), The theoretical number of side chains of the alkane = (f C b / f C p) × CP formula (6), the theoretical number of branched chains of the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane are calculated respectively using Equation (7), The theoretical number of side chains of cycloalkanes = (f C b / f C p) × CscNX Formula (7), and determine the number of side chains of the alkane, the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane according to the theoretical number of side chains.

5. The method according to claim 4, wherein, determining the number of branched chains of the alkane, the monocyclic cycloalkane, the bicyclic cycloalkane, the tricyclic cycloalkane, the tetracyclic cycloalkane, and the pentacyclic cycloalkane according to the theoretical number of branched chains includes: when the theoretical number of branched chains is 1.2 or less, the number of branched chains of the corresponding compound is 1; when the theoretical number of branched chains is greater than 1.2 and less than or equal to 1.8, the number of branched chains of the corresponding compound is 1 and 2; when the theoretical number of branched chains is greater than 1.8 and less than or equal to 2.2, the number of branched chains of the corresponding compound is 2; when the theoretical number of branched chains is greater than 2.2 and less than or equal to 2.8, the number of branched chains of the corresponding compound is 2 and 3; when the theoretical number of branched chains is greater than 2.8, the number of branched chains of the corresponding compound is 3.

6. The method according to claim 1, wherein, Determining the viscosity v of component i of the lubricating oil base oil to be measured at 40 °C according to the molecular structure information i , 40℃ and the viscosity v at 100 °C i , 100℃ including: the viscosity of the component i at 100 °C, 80 °C, and 60 °C is calculated using the group contribution method, and the viscosity of the component i at 40 °C is obtained by fitting and extrapolating based on the viscosity of the component i at 100 °C, 80 °C, and 60 °C; the group contribution method includes Rarey's group contribution method, Joback's group contribution method, or van's group contribution method.

7. The method according to claim 6, wherein, Substitute the viscosities of component i at 100°C, 80°C, and 60°C into v = aT b After obtaining the values of parameters a and b through multiple linear fitting, then calculate the viscosity of component i at 40°C; wherein, is the temperature, in °C, and v is the viscosity of the component i, in mm 2 / s.

8. The method according to claim 1, wherein, the method further includes: measuring the base oil of the lubricating oil to be tested using high-resolution mass spectrometry to obtain the molecular composition of the base oil of the lubricating oil to be tested.

9. The method according to claim 1, wherein, the difference between the calculated viscosity index VI and the measured viscosity index of the base oil of the lubricating oil is 0.5 to 1.5 units.

10. The method according to claim 1, wherein, the method further includes: obtaining a plurality of typical samples of the base oil of the lubricating oil; Establish a hydrocarbon model compound library based on the molecular structure information of the typical sample of the lubricating oil base oil, where the number of carbon atoms of the hydrocarbon model compounds in the hydrocarbon model compound library is C 18 ~C 38 , and the hydrocarbon model compounds include alkanes, monocyclic naphthenes, bicyclic naphthenes, tricyclic naphthenes, tetracyclic naphthenes and pentacyclic naphthenes; Determine the viscosity v of each of the hydrocarbon model compounds in the hydrocarbon model compound library at 40 °C j,40℃ and the viscosity v at 100 °C j,100℃ ; establishing a viscosity database of hydrocarbon model compounds based on the viscosities of all the hydrocarbon model compounds at 40 °C and 100 °C. According to the molecular structure information, determining the viscosity v of the component i at 40°C j,40℃ and the viscosity v at 100°C j,100℃ comprising: Determine the viscosity v at 40 °C of the hydrocarbon components in the lubricating oil base oil to be measured according to the viscosity database of the hydrocarbon model compounds mix , 40℃ and the viscosity v at 100 °C mix , 100℃ .

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