Standard fuel and use of standard fuel in fuel cetane number determination method

Abstract

The application relates to the technical field of cetane number testing, and discloses standard fuel and application of the standard fuel in a fuel cetane number determination method. The standard fuel comprises low-cetane-number normal standard fuel and high-cetane-number normal standard fuel; wherein the low-cetane-number normal standard fuel is a hanging type tetrahydrodicyclopentadiene, and the high-cetane-number normal standard fuel is selected from one of normal dodecane, normal decane and normal tetradecane. The standard fuel provided by the application has a good volume linear relationship, strictly meets the requirements of normal standard fuel, can expand the cetane number determination range of test fuel to 21.88-81.19, can greatly reduce the test cost, and is suitable for promotion.

Description

Technical Field

[0001] This invention relates to the field of cetane number testing technology, specifically to a standard fuel and its application in a method for determining the cetane number of fuels. Background Technology

[0002] Cetane number is an important indicator of diesel fuel activity, reflecting its ignition and combustion characteristics in compression-ignition engines. When determining the cetane number of diesel fuel using the standard engine method, a standard fuel is required. GB / T 386-2010, "Diesel Cetane Number Determination Method," specifies that the standard fuel is n-hexadecane and 2,2,4,4,6,8,8-heptamethylnonane. The standard specifies that the cetane number of n-hexadecane is 100, and the cetane number of 2,2,4,4,6,8,8-heptamethylnonane is 15. A mixture of n-hexadecane and 2,2,4,4,6,8,8-heptamethylnonane prepared in a certain volume ratio is the standard fuel. The cetane number of the standard fuel = 100 × volume fraction of n-hexadecane + 15 × volume fraction of heptamethylnonane. However, due to the ease with which n-hexadecane crystallizes and the high price of 2,2,4,4,6,8,8-heptamethylnonane, the application of positive standard fuels in actual tests has been greatly limited, thus leading to the development of secondary standard fuels.

[0003] GB / T 386-2010 standard specifies that secondary standard fuels are carefully selected high- and low-cetane number hydrocarbon fuels and their volume-ratio mixtures that can replace primary standard fuels for calculating the cetane number of diesel fuel. The two fuels are: T fuel (high cetane number, 73-76) and U fuel (low cetane number, 19-22). In routine diesel cetane number determination, the cetane number of diesel samples can be determined using secondary standard fuels calibrated to primary standard fuels and their volume-ratio mixtures.

[0004] Compared to pure standard fuels, secondary standard fuels are mixtures, and their stability and homogeneity cannot compare. Furthermore, because secondary standard fuels are mixtures, the cetane number of the blended standard fuel exhibits a non-linear blending effect to varying degrees, which is detrimental to improving the accuracy of test results. In addition, there are significant differences in composition between different batches of secondary standard fuels from different manufacturers. Currently, the secondary standard fuel market is mainly monopolized by Haltermann and Chevron-Phillips in the United States, and their prices are relatively high.

[0005] Positive standard fuels are single, pure compounds, exhibiting superior stability and homogeneity compared to mixed secondary standard fuels. If convenient and reasonably priced, positive standard fuels should be the optimal standard fuel for cetane number testing. Recently, ASTM in the United States proposed including 2,2,4,6,6-pentamethylheptane in the list of low-cetane number positive standard fuels, with a cetane number of 16.3. Compared to 2,2,4,4,6,8,8-heptamethylnonane, pentamethylheptane offers a purity of up to 99.5% and a relatively lower price. However, cetane number testing requires a large quantity of standard fuels, and 2,2,4,6,6-pentamethylheptane remains relatively expensive.

[0006] Therefore, there is an urgent need to provide a standard fuel that is not prone to crystallization, has stable product properties, can improve testing accuracy, and can reduce testing costs. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of easy crystallization and high price of positive standard fuel and unstable quality of secondary standard fuel products in the existing technology, and to provide a standard fuel and its application in the method of determining the cetane number of fuel, as well as the application of hanging tetrahydrodicyclopentadiene as a positive standard fuel in the method of determining the cetane number of fuel.

[0008] To achieve the above objectives, a first aspect of the present invention provides a standard fuel, wherein the standard fuel includes a low-hexadecane positive standard fuel and a high-hexadecane positive standard fuel; wherein the low-hexadecane positive standard fuel is a spooled tetrahydrodicyclopentadiene, and the high-hexadecane positive standard fuel is selected from one of n-dodecane, n-decane, and n-tetradecane.

[0009] A second aspect of the present invention provides the application of the standard fuel described in the first aspect of the present invention in a method for determining the cetane number of fuels.

[0010] 1) The standard fuel provided by this invention uses a hanging tetrahydrodicyclopentadiene as a low-hexadecane positive standard fuel and one of n-dodecane, n-decane and n-tetradecane as a high-hexadecane positive standard fuel. This makes the error between the theoretical hexadecane number of the standard fuel obtained by blending with the positive standard fuel and the test hexadecane number of the standard fuel measured by the constant volume combustion bomb method ≤ 0.9 hexadecane number units, and has a good volume linear relationship. It can expand the range of hexadecane number determination of the test fuel to 21.88-81.19.

[0011] 2) The standard fuel provided by this invention has significant cetane number differentiation and stability, strictly meets the requirements of positive standard fuel, and greatly reduces testing costs, making it suitable for widespread application. Attached Figure Description

[0012] Figure 1This is a graph showing the relationship between the derived cetane number and the n-dodecane volume fraction of the standard fuels in Examples 1-3;

[0013] Figure 2 This is a graph showing the relationship between the derived cetane number and the n-dodecane volume fraction of the standard fuel in Example 2. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] A first aspect of the present invention provides a standard fuel, the standard fuel comprising a low-hexadecane positive standard fuel and a high-hexadecane positive standard fuel; wherein the low-hexadecane positive standard fuel is a spooled tetrahydrodicyclopentadiene, and the high-hexadecane positive standard fuel is selected from one of n-dodecane, n-decane, and n-tetradecane.

[0016] The inventors of this invention discovered through research that using tetrahydrodicyclopentadiene as a low-hexadecane positive standard fuel and one of n-dodecane, n-decane, and n-tetradecane as a high-hexadecane positive standard fuel can avoid crystallization problems and improve the stability of the standard fuel. It can also increase the convergence between the theoretical hexadecane number and the tested hexadecane number of the blended standard fuel, increase the distinguishability of the hexadecane number of the standard fuel, and expand the test range of the hexadecane number of the fuel to be tested.

[0017] According to one embodiment of the present invention, the mass purity of the hanging tetrahydrodicyclopentadiene is ≥95%, preferably ≥98.5%.

[0018] According to one embodiment of the present invention, the mass purity of the n-dodecane is ≥97%, preferably ≥99%; the mass purity of the n-decane is ≥97%, preferably ≥99%; and the mass purity of the n-tetradecane is ≥97%, preferably ≥99%.

[0019] According to one embodiment of the present invention, the high cetane number standard fuel is n-dodecane. The standard fuel exhibits optimal overall performance when it is a mixture of tetrahydrodicyclopentadiene and n-dodecane.

[0020] According to one embodiment of the present invention, there is a volumetric linear relationship between the theoretical cetane number of the standard fuel and the test cetane number of the low cetane number positive standard fuel and the test cetane number of the high cetane number positive standard fuel.

[0021] In this invention, the volume linearity refers to the ability to calculate the theoretical cetane number of a standard fuel using the test cetane number of a low-cetane-number positive standard fuel and its volume fraction in the standard fuel, as well as the test cetane number of a high-cetane-number positive standard fuel and its volume fraction in the standard fuel.

[0022] This invention does not impose any particular limitations on the testing methods for the cetane number of low-cetane number positive standard fuels and the testing methods for the cetane number of high-cetane number positive standard fuels. Commonly used cetane number testing methods in the art can all be used in this invention.

[0023] Preferably, in this invention, the cetane number test refers to the cetane number of the fuel under test, measured using NB / SH / T 6035 "Determination of Derived Cetane Number of Diesel Fuel - Constant Volume Combustion Chamber Ignition Delay and Combustion Delay Method". This test method is performed on a constant volume combustion bomb system. The fuel under test is injected at a certain pressure into a bomb pre-filled with high-temperature, high-pressure synthesis air. The fuel spontaneously combusts, generating a dynamic pressure wave. Based on the ignition delay period determined by the dynamic pressure curve, the cetane number of the fuel under test is calculated. The cetane number of the fuel under test measured using NB / SH / T 6035 is also called the derived cetane number.

[0024] According to one embodiment of the present invention, the theoretical cetane number of the standard fuel satisfies Equation 1:

[0025] CN=CN1*V1+CN2*V2 Equation 1

[0026] Wherein, CN represents the theoretical cetane number of the standard fuel; CN1 represents the tested cetane number of the low cetane number positive standard fuel; V1 represents the volume percentage of the low cetane number positive standard fuel in the standard fuel; CN2 represents the tested cetane number of the high cetane number positive standard fuel; and V2 represents the volume percentage of the high cetane number positive standard fuel in the standard fuel.

[0027] According to one embodiment of the present invention, the error between the theoretical cetane number and the tested cetane number of the standard fuel is ≤0.9 cetane number units, preferably ≤0.75 cetane number units.

[0028] In this invention, the smaller the error between the theoretical cetane number and the tested cetane number of the standard fuel, the better the linear relationship between the theoretical cetane number and the volume of the standard fuel.

[0029] According to one embodiment of the present invention, the mixing volume ratio of low-cetane number positive standard fuel and high-cetane number positive standard fuel is not specifically required and can be selected according to the specific fuel to be tested. The closer the theoretical cetane number of the standard fuel is to the cetane number of the fuel to be tested, the higher the accuracy of the test results. To improve the accuracy of the test, it is preferable to determine the mixing volume ratio of low-cetane number positive standard fuel and high-cetane number positive standard fuel based on the cetane number of the fuel to be tested.

[0030] According to one embodiment of the present invention, the mixing volume ratio can be achieved by directly measuring the volume for mixing, or by converting the volume to mass using density and then weighing the corresponding mass. Compared with the mixing method of directly measuring the volume, the standard fuel volume content obtained by weighing after converting to mass is more accurate.

[0031] According to one embodiment of the present invention, after being placed at room temperature for 5-10 days, the change in the test cetane number of the standard fuel is ≤0.6 cetane number units, preferably ≤0.35 cetane number units.

[0032] In this invention, the change in the cetane number of the standard fuel refers to the absolute value of the difference between the derived cetane numbers before and after storage. This invention does not specifically limit the room temperature, which can be 15-35°C. The standard fuel in this invention, after being stored at room temperature for 5-10 days, shows virtually no change in its cetane number, indicating good stability.

[0033] A second aspect of the present invention provides the application of the standard fuel described in the first aspect of the present invention in a method for determining the cetane number of fuels.

[0034] According to one embodiment of the present invention, the present invention does not specifically limit the fuel and can be applied to all fuels that require testing for cetane number. Preferably, the fuel is diesel.

[0035] According to one embodiment of the present invention, the standard fuel is used as a low-cetane-number positive standard fuel in a fuel cetane number determination method.

[0036] The present invention will be described in detail below through embodiments. In the embodiments, the molecular formula of the pedigree tetrahydrodicyclopentadiene is C2 10 H 16 It has a molecular weight of 136.23 g / mol and a density (at 20℃) of 0.936 g / cm³. 3 The purity is 98.5%; the molecular formula of n-dodecane is C60. 12 H 26 It has a molecular weight of 170.38 g / mol and a density of 0.749 g / cm³. 3The purity is 99%.

[0037] Method for determining cetane number

[0038] The derived cetane number of low-cetane number standard fuel, high-cetane number standard fuel, and standard fuel was tested using the CID 510 cetane number analyzer manufactured by PAC Corporation, according to the standard NB / SH / T 6035 "Determination of derived cetane number of diesel fuel - constant volume combustion chamber ignition lag and combustion lag method". The derived cetane number of hanging tetrahydrodicyclopentadiene was 21.88, and that of n-dodecane was 81.19.

[0039] Example 1

[0040] A mixture of tetrahydrodicyclopentadiene and n-dodecane was prepared according to the mass conversion method to obtain a standard fuel; wherein the volume fraction of n-dodecane in the standard fuel was 25%; the theoretical cetane number of the standard fuel was calculated to be 36.71 using the formula 1CN = 21.88 * 0.75 + 81.19 * 0.25; the derived cetane number of the standard fuel was 37.27 as determined by the derived cetane number determination method.

[0041] The comparison shows that the theoretical cetane number and the derived cetane number of the standard fuel differ by 0.56 cetane number units, indicating that the standard fuel has a good volume linear relationship.

[0042] After the standard fuel was left at room temperature for 5 days, its derived cetane number was retested, and the derived cetane number was 37.31. Compared with the test result 5 days ago, the cetane number increased by 0.04 cetane number units, which is essentially unchanged, indicating the stability of the physicochemical properties of the standard fuel.

[0043] Example 2

[0044] Similar to Example 1, except that standard fuels with dodecane volume fractions of 50%, 51%, and 52% were prepared respectively. The theoretical and derived cetane numbers of these three standard fuels are shown in Table 1.

[0045] Table 1

[0046] n-Dodecane / V% Theoretical cetane number Derivation of cetane number error 50 51.54 50.99 0.55 51 52.13 51.67 0.46 52 52.72 52.23 0.49

[0047] As shown in Table 1, the theoretical and derived cetane numbers of the standard fuel gradually increase with the gradual increase of the n-dodecane volume fraction. Theoretical calculations show that for every 1% increase in the n-dodecane volume fraction, the cetane number of the standard fuel increases by approximately 0.6 cetane number units. Actual test results show that for every 1% increase in the n-dodecane volume fraction, the derived cetane number of the standard fuel increases by an average of approximately 0.62 cetane number units. Therefore, the standard fuel formulated using tetrahydrodicyclopentadiene and n-dodecane in this invention exhibits excellent cetane number distinguishability. Even with drastic changes in volume fraction, the cetane number remains highly distinguishable and exhibits good stability.

[0048] After the three standard fuels prepared in Example 2 were left at room temperature for 5 days, their derived cetane numbers were retested. The derived cetane number of the standard fuel with a 50% n-dodecane volume fraction was 50.75, a decrease of 0.24 cetane number units, with a change rate of 0.47%; the derived cetane number of the standard fuel with a 51% n-dodecane volume fraction was 51.70, an increase of 0.03 cetane number units, with a change rate of 0.06%; and the derived cetane number of the standard fuel with a 52% n-dodecane volume fraction was 52.53, an increase of 0.3 units, with a change rate of 0.57%. Therefore, the standard fuels prepared using tetrahydrodicyclopentadiene and n-dodecane in this invention exhibit good stability.

[0049] Example 3

[0050] Similar to Example 1, except that a standard fuel with a dodecane volume fraction of 73% was prepared, and the theoretical cetane number of the standard fuel was calculated to be 65.18 using the formula 1CN = 21.88 * 0.27 + 81.19 * 0.73;

[0051] The derived cetane number of the standard fuel was tested and found to be 64.47. After the standard fuel was left at room temperature for five days, it was tested again, and the derived cetane number was 64.79.

[0052] The relationship between the derived cetane number and the n-dodecane volume fraction of the standard fuels prepared in Examples 1-3 is as follows: Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 It is evident that, in this invention, a linear relationship exists between the derived cetane number and the volume fraction of n-dodecane in the standard fuel prepared using tetrahydrodicyclopentadiene and n-dodecane. The fitted line DCN = 21.90 + 0.588*V has an R-value of 0.9998. Theoretically, the cetane number range of samples that can be tested using the standard fuel of this invention is 21.88-81.19, which expands the testing range compared to existing standards.

[0053] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The application of a standard fuel in a method for determining the cetane number of fuels, characterized in that, The standard fuels include low-hexadecane positive standard fuels and high-hexadecane positive standard fuels; wherein, the low-hexadecane positive standard fuel is a spooled tetrahydrodicyclopentadiene, and the high-hexadecane positive standard fuel is selected from one of n-dodecane, n-decane, and n-tetradecane; There is a volumetric linear relationship between the theoretical cetane number of the standard fuel and the tested cetane number of the low-cetane-number positive standard fuel and the tested cetane number of the high-cetane-number positive standard fuel. The theoretical cetane number of the standard fuel satisfies Equation 1: CN=CN1 V1+CN2 V2 type 1 Wherein, CN represents the theoretical cetane number of the standard fuel; CN1 represents the tested cetane number of the low cetane number positive standard fuel; V1 represents the volume percentage of the low cetane number positive standard fuel in the standard fuel; CN2 represents the tested cetane number of the high cetane number positive standard fuel; and V2 represents the volume percentage of the high cetane number positive standard fuel in the standard fuel.

2. The application according to claim 1, wherein, The purity of the hanging tetrahydrodicyclopentadiene is ≥95%.

3. The application according to claim 2, wherein, The purity of the hanging tetrahydrodicyclopentadiene is ≥98.5%.

4. The application according to claim 1, wherein, The purity of the n-dodecane is ≥97%; the purity of the n-decane is ≥97%; and the purity of the n-tetradecane is ≥97%.

5. The application according to claim 4, wherein, The purity of the n-dodecane is ≥99%; the purity of the n-decane is ≥99%; the purity of the n-tetradecane is ≥99%.

6. The application according to claim 1, wherein, The high cetane number standard fuel is n-dodecane.

7. The application according to claim 1, wherein, The error between the theoretical cetane number and the tested cetane number of the standard fuel is ≤0.9 cetane number units.

8. The application according to claim 7, wherein, The error between the theoretical cetane number and the tested cetane number of the standard fuel is ≤0.75 cetane number units.

9. The application according to claim 7 or 8, wherein, After being placed at room temperature for 5-10 days, the change in the test cetane number of the standard fuel is ≤0.6 cetane number units.

10. The application according to claim 9, wherein, After being placed at room temperature for 5-10 days, the change in the test cetane number of the standard fuel is ≤0.35 cetane number units.

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