Freezing point standard substance for aviation fuel and preparation method of freezing point standard substance

Abstract

The invention belongs to the field of stoichiometric science, relates to an aviation fuel standard substance preparation technology, and particularly provides an aviation fuel freezing point standard substance and a preparation method thereof.The aviation fuel is treated through activated clay, and base oil with the low water content and the freezing point smaller than-60 DEG C is prepared; and mixing the base oil with n-dodecane, decane and cyclohexane, and standing to obtain the freezing point standard substance. The obtained freezing point standard substance takes jet fuel as a raw material, the quantity value is accurate and stable, and hydrocarbon crystals are obvious; according to the preparation method, standard substances with different freezing points are prepared by using different matrix jet fuels, the freezing points are stable, the deviation is small, and the preparation method is simple.

Description

Technical Field

[0001] The invention belongs to the field of chemical metrology science, and specifically relates to a preparation technology of aviation fuel standard substances, and provides an aviation fuel freezing point standard substance and a preparation method thereof. Background Art

[0002] Aviation fuel freezing point standard materials are used to calibrate aviation fuel freezing point test instruments. The existing freezing point standard materials in China are two types from the China Institute of Metrology, which use naphtha and mineral oil as raw materials and adopt different preparation ratios to obtain freezing point standard materials with nominal values ​​of -45℃±1℃ and -56℃±1℃.

[0003] The design of the freezing point test instrument for aviation fuel is based on GB / T 2430-2008 "Freezing point determination method for aviation fuel" or SH / T 0770-2018 "Freezing point determination method for aviation fuel (automatic phase conversion method)", and the lowest temperature at which hydrocarbon crystals disappear is measured as the freezing point. The objects measured by the above two instruments are jet fuels, and as mentioned above, the raw materials of domestic freezing point standard materials are naphtha and mineral oil, which have different technical indicators and hydrocarbon compositions from jet fuels. In order to ensure the consistency of the freezing point measurement results of jet fuel, this field urgently needs to develop a freezing point standard material with jet fuel as the raw material. Summary of the invention

[0004] In order to solve the current situation that the matrix of freezing point standard materials in the prior art is not jet fuel, and to ensure that the standard materials used to calibrate the freezing point measuring instrument are consistent with the measuring object of the instrument, the present invention proposes an aviation fuel freezing point standard material and a preparation method thereof. First, aviation fuel is treated with activated white clay to prepare a base oil with low water content and a freezing point less than -60°C, and then the base oil is mixed with n-dodecane, decane, and cyclohexane and allowed to stand to obtain a freezing point standard material. The obtained freezing point standard material uses jet fuel as a raw material, has an accurate and stable value, and obvious hydrocarbon crystallization; through the preparation method, different freezing point standard materials are prepared using different matrix jet fuels, and the freezing point is stable, the deviation is small, and the preparation method is simple.

[0005] The technical solution of the present invention is as follows: The inventor first provides an aviation fuel freezing point standard substance, whose raw materials include base oil, cyclohexane, n-dodecane and decane, the volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:(2.5-9):(2.5-9):(2.5-9), and the freezing point of the aviation fuel freezing point standard substance is -56~-45℃.

[0006] The preparation method of the base oil is as follows: First, select 100-300 mesh activated clay, dry it at 100℃-140℃ for at least 2h, add it to No. 3 jet fuel at a ratio of 10%-20% of the fuel mass, stir for at least 30min, stir at 20-60 rpm, stir evenly, let it stand for 2-4 days, filter to completely remove the activated clay, collect the filtered fuel to obtain the base oil, and store it away from light.

[0007] The water content of the above base oils was measured by Karl Fischer titrator, and the water content was less than 0.004%. The fuel freezing point of the base oils was measured in accordance with GB / T 2430 "Aviation Fuel Freezing Point Determination Method" or SH / T 0770 "Aviation Fuel Freezing Point Determination Method (Automatic Phase Conversion Method)", and the freezing point value was measured to be less than -60°C.

[0008] If the base oil has a high water content, the trace water in the base oil will crystallize at low temperatures, affecting the determination of the freezing point. Because the freezing point is the temperature at which crystals disappear, the crystals caused by the presence of water may not be hydrocarbon crystals, which can easily lead to misjudgment of the freezing point value. The freezing point of the base oil can be controlled below -60°C, and the freezing point of the base oil can be increased by adding different alkanes to obtain a freezing point standard substance.

[0009] On the basis of the above basic formula range, the inventors prefer that the volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:9:9:9, and the freezing point of the aviation fuel freezing point standard substance is -45°C±1°C.

[0010] Preferably, the volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:5:5:5, and the freezing point of the aviation fuel freezing point standard substance is -50°C±1°C.

[0011] Preferably, the volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:2.5:2.5:2.5, and the freezing point of the aviation fuel freezing point standard substance is -56°C±1°C.

[0012] The present invention further provides a method for preparing the aviation fuel freezing point standard substance, which comprises adding cyclohexane, n-dodecane and decane to the base oil, shaking manually or on a shaker, mixing evenly and standing for at least 12 hours to obtain the aviation fuel freezing point standard substance, which is stored in a brown glass bottle.

[0013] The beneficial effects of the present invention are as follows: the preparation method is simple and can obtain a freezing point standard substance with jet fuel as raw material, accurate and stable value and obvious hydrocarbon crystallization; through the present method, different freezing point standard substances are prepared by using different matrix jet fuels, and the freezing point is stable and the deviation is small, and the freezing point can be controlled within a smaller range. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1This is a diagram of hydrocarbon crystallization phenomenon when measuring the freezing point of the freezing point standard substance in Example 1; Figure 2 This is a diagram of hydrocarbon crystallization phenomenon when measuring the freezing point of the freezing point standard substance in Example 4; Figure 3 This is a diagram of hydrocarbon crystallization phenomenon when measuring the freezing point of the freezing point standard substance in Example 7; Figure 4 This is a diagram of hydrocarbon crystallization phenomenon when measuring the freezing point of the freezing point standard substance in Comparative Example 1; Figure 5 This is a diagram of the hydrocarbon crystallization phenomenon when measuring the freezing point of the freezing point standard substance in comparative example 2. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the technical solution of the present invention in more detail and should not be construed as limiting the protection scope of the present invention.

[0016] The manufacturer of the No. 3 jet fuel used in the following examples is Jinan Oil Refinery, the manufacturer of No. 2 is China Petroleum Lanzhou Petrochemical Company, and the manufacturer of No. 3 is China Petroleum Qingdao Petrochemical Co., Ltd.; 100 mesh activated clay, cyclohexane (analytical grade), n-dodecane (analytical grade), and decane (analytical grade) are all common commercial products. The 100 mesh activated clay used was dried at 140°C for 2 hours before use.

[0017] Example 1-3: Preparation of standard substance with a nominal freezing point of -45°C ± 1°C (1) Processing of raw materials The No. 3 jet fuels are numbered 1#, 2# and 3# respectively. The above-mentioned 1# jet fuel, 2# jet fuel and 3# jet fuel are used as raw materials to prepare freezing point standard substances.

[0018] 100 mesh activated clay was added to three batches of jet fuel, and the activated clay addition ratio was 15% of the fuel mass. The mixture was stirred at 30 rpm for half an hour, and filtered after standing for 2 days. The filtered fuel was collected in a brown glass bottle and stored in the dark. The water content was measured with a Karl Fischer moisture meter according to GB / T 11133, and the freezing point was measured according to GB / T 2430 "Freezing Point Determination of Aviation Fuel". The measurement results are shown in Table 1. The treated jet fuel was used as the base oil, and the base oils of the jet fuels numbered 1#, 2#, and 3# were named 1# base oil, 2# base oil, and 3# base oil.

[0019] Table 1 Measurement results of three base oils .

[0020] (2) Preparation Use a measuring cylinder to measure 2000 mL of 1#, 2#, and 3# base oils respectively, and put them into 5 L brown glass bottles respectively. Add 180 mL of cyclohexane, 180 mL of n-dodecane, and 180 mL of decane respectively, mix well, and place in a sealed state at room temperature away from light for 72 hours to obtain the fuels of Examples 1-3 respectively.

[0021] (3) Fixed value GB / T 2430-2008 “Freezing point determination method for aviation fuel” and SH / T 0770-2018 “Freezing point determination method for aviation fuel (automatic phase conversion method)” are used to determine the value of the prepared fuel. The freezing points obtained by the two methods are shown in Table 2. The standard value of each standard substance is taken from the average value of the two determination methods.

[0022] Table 2 Freezing point measurement results .

[0023] The freezing point standard substances obtained in the above examples 1-3 have obvious fogging (hydrocarbon crystallization) phenomenon when measuring the freezing point, such as Figure 1 As shown, when measuring the freezing point of the freezing point standard substance prepared in Example 1, obvious hydrocarbon crystallization phenomenon can be observed.

[0024] Example 4-6: Preparation of standard substance with a nominal freezing point of -50°C ± 1°C (1) Processing of raw materials The same method as in Examples 1-3 was used to obtain base oil #1, base oil #2, and base oil #3.

[0025] (2) Preparation Use a measuring cylinder to measure 2000 mL of 1#, 2#, and 3# base oils respectively, and put them into 5 L brown glass bottles respectively. Add 100 mL of cyclohexane, 100 mL of n-dodecane, and 100 mL of decane respectively, mix well, and place in a sealed state at room temperature away from light for 72 hours to obtain the fuels of Examples 4-6 respectively.

[0026] (3) Fixed value GB / T 2430-2008 “Freezing point determination method for aviation fuel” and SH / T 0770-2018 “Freezing point determination method for aviation fuel (automatic phase conversion method)” are used to determine the value of the prepared fuel. The freezing points obtained by the two methods are shown in Table 3. The standard value of each standard substance is taken from the average value of the two determination methods.

[0027] Table 3 Freezing point measurement results .

[0028] The freezing point standard substances obtained in Examples 4-6 above have obvious fogging (hydrocarbon crystallization) phenomenon when measuring freezing point, such as Figure 2 As shown, when measuring the freezing point of the freezing point standard substance prepared in Example 4, obvious hydrocarbon crystallization phenomenon can be observed.

[0029] Example 7-9: Preparation of a standard substance with a nominal freezing point of -56°C ± 1°C (1) Processing of raw materials The same method as in Examples 1-3 was used to obtain base oil #1, base oil #2, and base oil #3.

[0030] (2) Preparation Use a measuring cylinder to measure 2000 mL of 1#, 2#, and 3# base oils respectively, and put them into 5 L brown glass bottles respectively. Add 50 mL of cyclohexane, 50 mL of n-dodecane, and 50 mL of decane respectively, mix well, and place in a sealed state at room temperature away from light for 72 hours to obtain the fuels of Examples 7-9 respectively.

[0031] (3) Fixed value GB / T 2430-2008 “Freezing point determination method for aviation fuel” and SH / T 0770-2018 “Freezing point determination method for aviation fuel (automatic phase conversion method)” are used to determine the value of the prepared fuel. The freezing points obtained by the two methods are shown in Table 4. The standard value of each standard substance is taken from the average value of the two determination methods.

[0032] Table 4 Freezing point measurement results .

[0033] The freezing point standard substances obtained in the above Examples 7-9 have obvious fogging (hydrocarbon crystallization) phenomenon when measuring the freezing point, such as Figure 3 As shown, when measuring the freezing point of the freezing point standard substance prepared in Example 7, obvious hydrocarbon crystallization phenomenon can be observed.

[0034] Comparative Example 1 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that in Comparative Example 1, decane was not added during the preparation, but 180 mL of cyclohexane and 180 mL of n-dodecane were added.

[0035] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -46.5℃.

[0036] like Figure 4 As shown, the freezing point standard substance prepared in Comparative Example 1 has no obvious hydrocarbon crystallization phenomenon when measuring the freezing point, which can easily lead to misjudgment of the freezing point.

[0037] Comparative Example 2 The 2# base oil obtained in Examples 1-3 was used to prepare the fuel and perform the calibration, except that in Comparative Example 2, decane was not added during the preparation, but 180 mL of cyclohexane and 180 mL of n-dodecane were added.

[0038] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -47.5℃.

[0039] like Figure 5 As shown, the freezing point standard substance prepared in Comparative Example 2 has no obvious hydrocarbon crystallization phenomenon when measuring the freezing point, which can easily misjudge the freezing point.

[0040] Comparative Example 3 The 3# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that in Comparative Example 3, decane was not added during the preparation, but 180 mL of cyclohexane and 180 mL of n-dodecane were added.

[0041] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -45.5℃.

[0042] Comparative Example 4 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that in Comparative Example 4, no n-dodecane was added during the preparation, but 180 mL of cyclohexane and 180 mL of decane were added.

[0043] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -63.0℃.

[0044] Comparative Example 5 The 2# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that in Comparative Example 5, no n-dodecane was added during the preparation, but 180 mL of cyclohexane and 180 mL of decane were added.

[0045] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -64.5℃.

[0046] Comparative Example 6 The 2# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that cyclohexane was not added during the preparation in Comparative Example 6, but 180 mL of n-dodecane and 180 mL of decane were added.

[0047] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -44.5℃.

[0048] Comparative Example 7 The 3# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that cyclohexane and decane were not added during the preparation in Comparative Example 7, but 180 mL of n-dodecane was added.

[0049] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -43.0℃.

[0050] Comparative Example 8 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that in Comparative Example 8, no n-dodecane and decane were added during the preparation, but 180 mL of cyclohexane was added.

[0051] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -62.0℃.

[0052] Comparative Example 9 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that cyclohexane and n-dodecane were not added during the preparation in Comparative Example 9, but 180 mL of decane was added.

[0053] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -61.0℃.

[0054] Comparative Example 10 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that cyclohexane and decane were not added during the preparation in Comparative Example 10, but 100 mL of n-dodecane was added.

[0055] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -48.5℃.

[0056] Comparative Example 11 The 1# base oil obtained in Examples 1-3 was used to prepare fuel and perform the calibration, except that cyclohexane and decane were not added during the preparation in Comparative Example 11, but 50 mL of n-dodecane was added.

[0057] When measuring the freezing point, a small amount of foggy crystals appeared, and the freezing point value was -51.5℃.

[0058] Analysis of the above data shows that: 1) By comparing Examples 1-9 with Comparative Examples 1-11, it can be seen that when the freezing point standard substance does not contain all three components of n-dodecane, cyclohexane and decane, the freezing point standard substances obtained using the same formula for different types of jet fuels have large deviations between the freezing points of the various groups. Only when n-dodecane, cyclohexane and decane are all added, the freezing point deviations between the freezing point standard substances obtained using different jet fuels are small, and the freezing point standard value can be controlled within a smaller range.

[0059] 2) By comparing Examples 1-9 and Comparative Examples 4-5, it can be seen that when the freezing point standard substance does not contain n-dodecane, the freezing point of the freezing point standard substance changes significantly.

[0060] 3) The instrument designed according to GB / T 2430-2008 "Freezing Point Determination of Aviation Fuel" requires manual determination of the end point of the disappearance of foggy crystals. It can be seen from the comparison between Examples 1-9 and Comparative Examples 1-11 that when the freezing point standard substance contains all three components of n-dodecane, cyclohexane and decane, the fogging phenomenon is obvious and the operator can clearly identify the freezing point temperature; when the foggy crystals are not obvious, the experimenter will continue to lower the temperature until the foggy crystals are found, and then raise the temperature to see the temperature at which the crystals disappear, which is easy to misjudge the freezing point.

[0061] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should fall within the protection scope determined by the claims of the present invention.

Claims

1. An aviation fuel freezing point standard material, comprising base oil, characterized in that: It also includes cyclohexane, n-dodecane and decane. The volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:(2.5-9):(2.5-9):(2.5-9). The freezing point of the aviation fuel freezing point standard substance is -56~-45℃.

2. The aviation fuel freezing point standard material according to claim 1, characterized in that: The preparation method of the base oil is as follows: firstly, 100-300 mesh activated clay is selected, dried at 100-140° C. for at least 2 hours, added into No. 3 jet fuel in a proportion of 10%-20% of the fuel mass, stirred for at least 30 minutes at a stirring speed of 20-60 rpm, stirred evenly, allowed to stand for 2-4 days, filtered to completely remove the activated clay, and the filtered fuel was collected to obtain the base oil.

3. The aviation fuel freezing point standard material according to claim 1 or 2, characterized in that: The volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:9:9:9, and the freezing point of the aviation fuel freezing point standard substance is -45°C±1°C.

4. The aviation fuel freezing point standard material according to claim 1 or 2, characterized in that: The volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:5:5:5, and the freezing point of the aviation fuel freezing point standard substance is -50°C±1°C.

5. The aviation fuel freezing point standard material according to claim 1 or 2, characterized in that: The volume ratio of the base oil to cyclohexane, n-dodecane and decane is 100:2.5:2.5:2.5, and the freezing point of the aviation fuel freezing point standard substance is -56°C±1°C.

6. The aviation fuel freezing point standard material according to claim 1 or 2, characterized in that: The water content of the base oil is lower than 0.004% and the freezing point is lower than -60°C.

7. The method for preparing the aviation fuel freezing point standard material according to any one of claims 1 to 6, characterized in that: Cyclohexane, n-dodecane and decane were added to the base oil, mixed evenly, and allowed to stand for at least 12 hours to obtain the aviation fuel freezing point standard material.

8. The preparation method according to claim 7, characterized in that: The mixing is carried out by shaking manually or on a shaker.

9. The preparation method according to claim 7, characterized in that: The prepared aviation fuel freezing point standard material was stored in a brown glass bottle.

Images