Method for measuring moisture of crude oil

Abstract

The invention relates to a method for measuring the water content or moisture of crude oil based on a temperature titration principle. The method is simple, convenient and rapid in measurement process, wide in water content measurement range, good in repeatability of measurement results, high in accuracy and capable of rapidly and accurately measuring the water content of the crude oil.

Description

Technical Field

[0001] The invention relates to a method for measuring the water content of crude oil, and in particular to a method for measuring the water content of crude oil based on the temperature titration principle. Background Art

[0002] Crude oil usually contains a certain amount of water. During the transportation stage of crude oil, the water in the crude oil will rub in the pipeline, reducing the transportation speed, and the water will also form acid with the acidic substances in the crude oil, corroding the pipeline; during the refining stage of crude oil, too high water content will increase energy consumption and lead to instability in the distillation process. However, the higher the degree of dehydration of crude oil, the higher the cost. In order to balance the interests of both parties in crude oil trading and ensure safe production, national standards and industry standards stipulate the limit of crude oil moisture. "GB 36170 Crude Oil" stipulates that the moisture content of paraffin-based or paraffin-intermediate crude oil shall not exceed 0.5% (mass fraction). "SN / T2999 Import Crude Oil Quality Evaluation Requirements" stipulates that imported crude oil is classified according to moisture content, and the moisture content of low-water crude oil shall not exceed 0.1%; the moisture content of water-containing crude oil shall not exceed 1.0%. Therefore, it is necessary to accurately measure the moisture content in crude oil.

[0003] There are many methods for measuring the water content in crude oil. The commonly used methods include distillation, Karl Fischer method, azeotropic distillation-Karl Fischer method and centrifugation.

[0004] The distillation method adds crude oil sample and xylene to the distillation flask, heats the mixture under reflux conditions, and the azeotrope of xylene and water is condensed by the condenser and flows into the receiver. Xylene and water are separated into layers, and water is retained at the bottom of the receiver. The volume of water (unit: ml) is read through the receiver scale, and the excess xylene flows back to the distillation flask. The distillation method has a wide range of water content measurement, from 0.05g to 5g, simple equipment, easy operation, and low cost. Therefore, as an international standard method and national standard method for crude oil water, it is widely used in the determination of water content in commercial crude oil and crude oil in production. However, the volume resolution of the receiver used in the distillation method is low, the sensitivity of the water content measurement result is low, and the repeatability is poor; the distilled water will adhere to the wall of the condenser tube, and the solvent and water in the receiver cannot be completely separated, resulting in low measurement results; the detection time is long (1-2h).

[0005] In an organic solvent system, iodine reacts with sulfur dioxide and water in a Karl Fischer reaction. The stoichiometric ratio of iodine to water is 1:1. Therefore, the water content of the sample can be calculated based on the amount of substance that consumes iodine. According to the different ways of adding iodine, it can be divided into Karl Fischer coulometric method and Karl Fischer volumetric method. Karl Fischer coulometric method has high sensitivity, and the detection limit of water content is as low as 0.01 mg; it has good repeatability and short measurement time (no more than 10 minutes). However, the water content measurement range of this method is low, generally not exceeding 10 mg, and can only be used for commercial crude oil with low water content; when measuring samples with high water content, the sampling volume is too small, the representativeness is insufficient, and the repeatability and accuracy are reduced; the crude oil sample may not be completely dissolved in the electrolyte, resulting in low results; in addition, crude oil often contains sulfur-containing reducing substances, which will react with iodine molecules and may cause high results. The water content measurement range of the Karl Fischer volumetric method is better than that of the Karl Fischer coulometric method, and the maximum water content can reach 100 mg; however, there are also problems such as incomplete dissolution of crude oil samples resulting in low results, and side reactions between reducing substances and iodine resulting in high results.

[0006] Azeotropic distillation - Karl Fischer method is to dissolve the crude oil sample in xylene solvent, heat the mixed solution to make the azeotrope of water and xylene pass into the titration cup of Karl Fischer coulometric moisture titrator along with the carrier gas, and measure the water content by Karl Fischer coulometric method to obtain the water content in the sample. Compared with Karl Fischer method, this method avoids the side reaction of reducing substances and electrolytes, and improves accuracy; compared with distillation method, the coulometric method is used instead of the naked eye to read the volume of water, and the sensitivity is improved. However, the water content measurement range of this method is low, not exceeding 10mg, and can only be used for commercial crude oil with low water content.

[0007] The density of crude oil is less than that of water, and the polarity of crude oil components is weak, while the polarity of water is strong. Therefore, when a water-containing crude oil sample is centrifuged at high speed, the emulsified water in the crude oil will turn into free water and settle. The water content of the crude oil can be calculated by reading the volume of water at the bottom of the container. The centrifugation method has a simple principle, fast measurement speed and high efficiency. However, oil and water cannot be completely separated under the action of centrifugal force, resulting in a water content lower than the actual value.

[0008] In summary, there is currently a lack of a method for measuring the moisture content of crude oil that is convenient, fast, has a large water content measurement range, and produces accurate and reliable results. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a method for measuring the water content or moisture content of crude oil based on the principle of temperature titration. When the reactant in the titrant (such as triethyl orthoformate (TEOF)) and the water in the crude oil sample undergo a hydrolysis reaction under the catalytic action of an acid (the reaction formula is shown below), heat will be absorbed, thereby causing the temperature of the solution to drop; when the water is completely consumed, the temperature of the solution will have an inflection point. By monitoring the temperature of the solution with a thermometer, the end point of the hydrolysis reaction can be accurately determined, and then the water content of the sample can be calculated based on the concentration of the reactant in the titrant, the volume of the consumed titrant, and the mass of the sample.

[0010]

[0011] According to one aspect of the present invention, the present invention provides a method for measuring the water content or moisture content of crude oil, comprising the following steps:

[0012] (1) Calibration:

[0013] The titration solvent and the catalyst are added into the titration cup of the thermometric titrator, and then different amounts of deionized water are added into the titration cup respectively, the cup is sealed and stirred, and after being uniformly mixed, a titrant is dripped into the titration cup, and the volume of the titrant dripped at the titration end point is determined by using the thermometric titrator, and a calibration curve is drawn with the mass of the deionized water as the abscissa and the volume of the titrant as the ordinate; the catalyst is dodecylbenzenesulfonic acid, and the titrant is triethyl orthoformate (TEOF) or a solution thereof;

[0014] Preferably, the volume percentage concentration of the triethyl orthoformate solution is at least 20%;

[0015] Preferably, the solvent of the triethyl orthoformate solution is selected from cyclohexane, isooctane, etc.; cyclohexane is most preferred;

[0016] Preferably, the titration solvent is selected from cyclohexane, isopropanol, methanol, xylene, etc. and any mixture thereof; further preferably, a mixture of cyclohexane, isopropanol and xylene, more preferably, the volume percentages of cyclohexane, isopropanol and xylene in the mixture are 30-50%, 5-10% and 40-60%, respectively; or, further preferably, a mixture of cyclohexane, methanol and xylene, more preferably, the volume percentages of cyclohexane, methanol and xylene in the mixture are 30-50%, 5-10% and 40-60%, respectively;

[0017] Preferably, the amount of the titration solvent is 40 to 60 mL; most preferably 50 mL;

[0018] Preferably, the volume ratio of the catalyst to the titration solvent is 1:60-75; more preferably 1:65-70; most preferably, the amount of the catalyst is 0.75 mL;

[0019] Preferably, the amount of deionized water added in different amounts is several points in 5-1500 mg, such as at least 3 points, preferably at least 5 points, such as 4 points, 5 points, 6 points, 7 points, 8 points, 9 points, 10 points, etc.; more preferably 8 points between 5-300 mg, such as about 5 mg, about 10 mg, about 20 mg, about 50 mg, about 100 mg, about 150 mg, about 200 mg, about 300 mg, or 5 points between 300-1500 mg, such as about 350 mg, 550 mg, 700 mg, 1050 mg and 1500 mg;

[0020] Preferably, the rate at which the titrant is dripped into the titration cup is 0.5 to 2.0 mL / min; most preferably 0.5 to 1.0 mL / min;

[0021] Those skilled in the art understand that as the titrant is added, a hydrolysis reaction occurs and heat is absorbed. However, because stirring generates heat, the solution temperature will first rise and then fall. When the solution temperature reaches an inflection point, it indicates that the water is completely consumed and the hydrolysis reaction is terminated, which is the titration endpoint. Preferably, the titration endpoint is when the second differential curve of the solution temperature measured by the temperature titrator reaches the vertex;

[0022] Preferably, the smoothing coefficient of the second differential curve of the solution temperature is 30 to 70; most preferably 55;

[0023] Preferably, a linear fit is performed on the calibration curve to obtain the following fitting formula:

[0024] y=ax+b

[0025] In the above formula, y is the volume of the titrant, in units such as mL; x is the mass of deionized water, that is, the water content of the sample, in units such as mg; a is the slope of the calibration curve; and b is the intercept.

[0026] (2) Measurement:

[0027] According to the operation of step (1), the deionized water is replaced by the crude oil sample, the volume of the titrant added at the titration endpoint is determined, i.e., the titrant volume, and the water content of the crude oil sample is determined according to the calibration curve;

[0028] Preferably, the mass of the crude oil sample is 0.4 to 10 g;

[0029] Preferably, the water content of the crude oil sample is determined according to a fitting formula;

[0030] Preferably, the water content of the crude oil sample is calculated according to the following formula:

[0031]

[0032] In the above formula, c is the water content of the crude oil sample, in units such as mg / g; xoil is the water content of the crude oil sample, in units such as mg; m oil is the mass of the crude oil sample, in units such as g.

[0033] Preferably, the above measurement method further comprises the following steps:

[0034] (3)Amendment:

[0035] According to the operation of step (1), the deionized water sample is measured once. The mass of the deionized water sample is equal to or close to the water mass of the crude oil sample that has been measured or to be measured. According to the mass of the deionized water sample and its measurement result, the water content recovery rate is calculated according to the following formula:

[0036]

[0037] In the above formula, Recovery is the water content recovery rate; x dionizied water is the mass measurement result of the deionized water sample, in units such as mg; m dioinzed water is the mass of the deionized water sample, in units such as mg;

[0038] According to the following formula, the water content or moisture content of the nearby crude oil sample that has been tested or is to be tested is corrected to obtain the corrected value of the water content or moisture content:

[0039]

[0040] In the above formula, x' and c' are the water content and moisture correction values ​​of the crude oil sample, respectively, and the units are, for example, mg or mg / g; x and c are the water content and moisture of the uncorrected crude oil sample, respectively, that is, the water content or moisture of the crude oil sample that has been tested or is to be tested, respectively, and the units are, for example, mg or mg / g.

[0041] Those skilled in the art will appreciate that the titration solvent, titrant, catalyst, etc. may change slightly over time, and the ambient humidity, etc. may also change over time, which may cause the calibration curve to drift. In order to eliminate the measurement error caused by the drift of the calibration curve, it is preferred to measure the deionized water sample once at a certain interval or a certain number of measurements, for example, every 2 or 4 measurements of the crude oil sample, to make corrections.

[0042] According to the present invention, the various solvents used are preferably analytically pure or chromatographically pure.

[0043] The measuring method of the present invention is simple, the single measuring time does not exceed 20 minutes, and it is relatively fast; the water content measuring range is (5mg-1500mg), and the range is wide; and the measuring result has good repeatability and high accuracy. Therefore, the method can be used to conveniently, quickly and accurately measure the water content of crude oil, and the water content range of the sample is relatively wide, which is suitable for both commercial crude oil with low water content and crude oil in production with high water content, and therefore has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The titrant volume-solution temperature curve and the titrant volume-solution temperature quadratic differential curve when measuring the sample moisture by the temperature titration method in Example 1 are

[0045] Left ordinate: temperature, unit: ℃; right ordinate: second derivative of temperature; horizontal axis: titrant volume, unit: mL. Black curve: titrant volume-solution temperature; red curve: second derivative curve of titrant volume-solution temperature.

[0046] Figure 2 The calibration curve of the thermometric titration method in Example 1 when the water content is relatively low (5-300 mg)

[0047] The horizontal axis is the water content of the sample, unit: mg; the vertical axis is the volume of the titrant, unit: mL.

[0048] Figure 3 This is the calibration curve of the temperature titration method when the water content range is relatively high (300-1400 mg) in Example 5. The horizontal coordinate is the sample water content, unit: mg; the vertical coordinate is the titrant volume, unit: mL. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content recorded in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the present invention equally.

[0050] Example 1. Measuring the water content and moisture content of light crude oil samples:

[0051] The reactant triethyl orthoformate (TEOF) is dissolved in chromatographically pure cyclohexane to a volume percentage concentration of 30% to obtain a titrant. 500 mL of the titrant is placed in a sealed glass bottle for storage, and the burette of the thermometric titrator draws the titrant from the glass bottle and drips it into the titration cup of the thermometric titrator.

[0052] Mix 420 mL of chromatographically pure cyclohexane, 80 mL of analytically pure isopropanol and 500 mL of analytically pure xylene to obtain a titration solvent. Place 1 L of the titration solvent in a glass bottle with a stirrer and a dispenser at the mouth of the bottle, and place the glass bottle on a magnetic stirring table for continuous stirring.

[0053] Add 50mL titration solvent and 0.75mL catalyst dodecylbenzenesulfonic acid to the titration cup of the thermometric titrator, then add 99.60mg deionized water to the titration cup, seal and stir. After 3min, drip the titrant into the titration cup at a rate of 1mL / min. The smoothing coefficient of the solution temperature quadratic differential curve of the thermometric titrator is 55. The titrant volume-solution temperature curve and the titrant volume-solution temperature quadratic differential curve are as follows: Figure 1 As shown, the inflection point of the titrant volume-solution temperature curve coincides with the vertex of the quadratic differential curve of the titrant volume-solution temperature, which is the titration end point. At this time, the titrant volume is 3.141 mL.

[0054] According to the above method, 4.94, 10.33, 20.60, 50.03, 99.60, 154.47, 201.30 and 301.83 mg of deionized water were added, and the titrant volumes were measured to be 0.405, 0.717, 1.005, 1.750, 3.141, 4.724, 6.073 and 8.971 mL, respectively. With the mass of deionized water as the abscissa and the volume of titrant as the ordinate, we get Figure 2 The calibration curve is shown. Further, the calibration curve is linearly fitted to obtain the following fitting formula:

[0055] y=0.0285x+0.3465

[0056] In the above formula, y is the volume of titrant, in mL; x is the mass of deionized water, i.e. the water content of the sample, in mg.

[0057] According to the above method, 8.7550g of light crude oil sample was added, and the volume of the titrant was measured to be 2.9100mL. According to the above fitting formula, the water content of the crude oil sample was 89.947mg. The water content of the crude oil sample (i.e., the mass fraction of water) was calculated to be 10.27mg / g according to the following formula:

[0058]

[0059] In the above formula, c is the water content of the crude oil sample, in mg / g; x oil is the water content of the crude oil sample, in mg; m oil is the mass of the crude oil sample in g.

[0060] Example 2. Measuring the water content and moisture content of light crude oil samples:

[0061] According to the method of Example 1, 8.3381 g of light crude oil sample was added, and the volume of the titrant was measured to be 2.750 mL. According to the fitting formula of Example 1, the water content of the crude oil sample was 84.333 mg, and the water content of the crude oil sample was calculated to be 10.11 mg / g.

[0062] According to the method of Example 1, 85.7 mg of deionized water sample was added, and the volume of the titrant was measured to be 2.8083 mL. According to the fitting formula of Example 1, the mass of the deionized water sample was measured to be 86.38 mg. The water content recovery rate (Recovery) was calculated to be 100.79% according to the following formula:

[0063]

[0064] In the above formula, Recovery is the water content recovery rate; x dionizied water is the mass measurement result of the deionized water sample, in mg; m dioinzed water is the mass of the deionized water sample in mg.

[0065] According to the above formula, the water content of the crude oil sample measured in this embodiment is corrected, and the corrected value of the water content is 10.03 mg / g.

[0066] Example 3. Measuring the water content of light crude oil samples:

[0067] Prepare 5 light crude oil moisture standard samples: Take dehydrated dry light crude oil and deionized water, weigh their masses respectively, and mix the two to obtain light crude oil moisture standard samples. According to the moisture and mass of the dry crude oil and the mass of deionized water, the moisture standard values ​​of the light crude oil moisture standard samples are calculated to be 1.12, 2.14, 3.14, 5.14 and 10.05 mg / g respectively.

[0068] According to the method of Example 1, the moisture content of 5 light crude oil moisture standard samples was measured respectively, each of which was measured 6 times, and the average value was calculated as the moisture measurement value. At the same time, the relative standard deviation, measurement result error, and relative error were calculated. The specific results are shown in Table 1.

[0069] Table 1. Results of measuring the water content of five light crude oil standard samples by thermometric titration

[0070]

[0071] As shown in Table 1, the relative standard deviation of the moisture measurement results of the five light crude oil standard samples does not exceed 0.92%, indicating that the measurement results have good repeatability; the relative error of the measurement results does not exceed -3.57%, indicating that the measurement results have high accuracy.

[0072] Example 4. Measuring the water content of heavy crude oil samples:

[0073] Prepare 5 kinds of heavy crude oil moisture standard samples: Take dehydrated and dried heavy crude oil and deionized water, weigh their masses respectively, and mix the two to obtain light crude oil moisture standard samples. According to the moisture and mass of the dried crude oil and the mass of deionized water, the moisture standard values ​​of the heavy crude oil moisture standard samples are calculated to be 1.13, 2.13, 3.15, 5.06 and 10.06 mg / g respectively.

[0074] According to the method of Example 1, the moisture content of 5 kinds of heavy crude oil moisture standard samples was measured respectively, and each kind was measured 6 times. The average value was calculated as the moisture measurement value. At the same time, the relative standard deviation, measurement result error and relative error were calculated. The specific results are shown in Table 2.

[0075] Table 2. Results of measuring the water content of five heavy crude oil standard samples by thermometric titration

[0076]

[0077] As shown in Table 2, the relative standard deviation of the moisture measurement results of the five heavy crude oil standard samples does not exceed 0.88%, indicating that the measurement results have good repeatability; the relative error of the measurement results does not exceed -1.98%, indicating that the measurement results have high accuracy.

[0078] Example 5. Measuring the water content and moisture content of a light crude oil sample with high water content:

[0079] 500 mL of the titrant reactant triethyl orthoformate (TEOF) was placed in a sealed glass bottle for storage, and the burette of the thermometric titrator extracted the titrant from the glass bottle and dripped it into the titration cup of the thermometric titrator.

[0080] Mix 420 mL of chromatographically pure cyclohexane, 80 mL of analytically pure methanol and 500 mL of analytically pure xylene to obtain a titration solvent. Place 1 L of the titration solvent in a glass bottle with a stirrer and a dispenser at the mouth of the bottle, and place the glass bottle on a magnetic stirring table for continuous stirring.

[0081] Add 50mL titration solvent and 0.75mL catalyst dodecylbenzenesulfonic acid to the titration cup of the thermometric titrator, then add 1042.10mg deionized water to the titration cup, seal and stir. After 3 minutes, drip the titrant into the titration cup at a rate of 0.5mL / min. The smoothing coefficient of the solution temperature quadratic differential curve of the thermometric titrator is 55. The inflection point of the titrant volume-solution temperature curve coincides with the vertex of the quadratic differential curve of the titrant volume-solution temperature, which is the titration endpoint. At this time, the titrant volume is 6.4175mL.

[0082] According to the above method, 350.80, 538.20, 697.80, 1042.10, and 1503.50 mg of deionized water were added, and the titrant volumes were measured to be 2.1783, 3.3725, 4.3375, 6.4175, and 9.0333 mL, respectively. With the mass of deionized water as the horizontal axis and the volume of titrant as the vertical axis, we get Figure 3 The calibration curve is shown. Further, the calibration curve is linearly fitted to obtain the following fitting formula:

[0083] y=0.0059x+0.1605

[0084] In the above formula, y is the volume of titrant, in mL; x is the mass of deionized water, i.e. the water content of the sample, in mg.

[0085] According to the above method, 9.7732g of light crude oil sample was added, and the volume of the titrant was measured to be 6.5350mL. According to the above fitting formula, the water content of the crude oil sample was 1080.4237mg. The water content of the crude oil sample was calculated to be 110.55mg / g according to the following formula:

[0086]

[0087] In the above formula, c is the water content of the crude oil sample, in mg / g; x oil is the water content of the crude oil sample, in mg; moil is the mass of the crude oil sample, in g.

[0088] In addition, three light crude oil moisture standard samples were prepared: dehydrated dry light crude oil and deionized water were taken, their masses were weighed respectively, and the two were mixed to obtain light crude oil moisture standard samples. According to the moisture and mass of the dry crude oil and the mass of deionized water, the moisture standard values ​​of the light crude oil moisture standard samples were calculated to be 48.58, 75.40 and 110.55 mg / g respectively.

[0089] According to the above method, the moisture content of three light crude oil moisture standard samples was measured respectively, and each sample was measured 6 times. The average value was calculated as the moisture measurement value. At the same time, the relative standard deviation, measurement result error and relative error were calculated. The specific results are shown in Table 3.

[0090] Table 3. Results of measuring the moisture content of three light crude oil standard samples by thermometric titration

[0091]

[0092]

[0093] As shown in Table 3, the relative standard deviation of the moisture measurement results of the three light crude oil standard samples does not exceed 0.97%, indicating that the measurement results have good repeatability; the relative error of the measurement results does not exceed 0.74%, indicating that the measurement results have high accuracy.

[0094] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the water content or moisture content of crude oil, characterized in that: The steps include: (1) Calibration: The titration solvent and the catalyst are added into the titration cup of the thermometric titrator, and then different amounts of deionized water are added into the titration cup respectively, the cup is sealed and stirred, and after being uniformly mixed, a titrant is dripped into the titration cup, and the volume of the titrant dripped at the titration end point is determined by using the thermometric titrator, and a calibration curve is drawn with the mass of the deionized water as the abscissa and the volume of the titrant as the ordinate; the catalyst is dodecylbenzenesulfonic acid, and the titrant is triethyl orthoformate (TEOF) or a solution thereof; (2) Measurement: According to the operation of step (1), the deionized water is replaced by the crude oil sample, the volume of the titrant added at the titration endpoint is determined, i.e., the titrant volume, and the water content of the crude oil sample is determined according to the calibration curve; or further, The water content of the crude oil sample is calculated according to the following formula: In the above formula, c is the water content of the crude oil sample; x oil is the water content of the crude oil sample; m oil is the mass of the crude oil sample.

2. The measuring method according to claim 1, characterized in that: The calibration curve was linearly fitted and the following fitting formula was obtained: y=ax+b In the above formula, y is the volume of titrant; x is the mass of deionized water, that is, the water content of the sample; a is the slope of the calibration curve; b is the intercept; And, the water content of the crude oil sample is determined according to the fitting formula.

3. The measuring method according to claim 1 or 2, characterized in that: Further comprising the steps of: (3)Amendment: According to the operation of step (1), the deionized water sample is measured once. The mass of the deionized water sample is equal to or close to the water mass of the crude oil sample that has been measured or to be measured. According to the mass of the deionized water sample and its measurement result, the water content recovery rate is calculated according to the following formula: In the above formula, Recovery is the water content recovery rate; x dioniziedwater is the mass measurement result of the deionized water sample; m dioinzedwater is the mass of the deionized water sample; And, according to the following formula, the water content or moisture content of the adjacent crude oil sample that has been tested or to be tested is corrected to obtain the corrected value of the water content or moisture content: In the above formula, x' and c' are the water content and moisture correction values ​​of the crude oil sample, respectively; x and c are the water content and moisture of the uncorrected crude oil sample, respectively, that is, the water content or moisture of the crude oil sample that has been tested or is to be tested.

4. The measuring method according to claim 1 or 2, characterized in that: In step (1), the volume percentage concentration of the triethyl orthoformate solution is at least 20%; the solvent of the triethyl orthoformate solution is selected from cyclohexane and isooctane.

5. The measuring method according to claim 1 or 2, characterized in that: In step (1), the titration solvent is selected from cyclohexane, isopropanol, methanol, xylene and any mixture thereof; the amount of the titration solvent is 40 to 60 mL; the volume ratio of the catalyst to the titration solvent is 1:60 to 75; and the rate at which the titrant is dripped into the titration cup is 0.5 to 2.0 mL / min.

6. The measuring method according to claim 5, characterized in that: The titration solvent is a mixture of cyclohexane, isopropanol and xylene, wherein the volume percentages of cyclohexane, isopropanol and xylene are 30-50%, 5-10% and 40-60% respectively; or a mixture of cyclohexane, methanol and xylene, wherein the volume percentages of cyclohexane, methanol and xylene are 30-50%, 5-10% and 40-60% respectively; the amount of the titration solvent is 50 mL; the amount of the catalyst is 0.75 mL; and the rate at which the titrant is dripped into the titration cup is 0.5-1.0 mL / min.

7. The measuring method according to claim 1 or 2, characterized in that: In step (1), the amount of deionized water added is several points in the range of 5-1500 mg.

8. The measuring method according to claim 1 or 2, characterized in that: In step (1), the titration endpoint is when the second differential curve of the solution temperature measured by the temperature titrator reaches the top; and the smoothing coefficient of the second differential curve of the solution temperature is 30 to 70.

9. The measuring method according to claim 8, characterized in that: The smoothing coefficient of the second derivative curve of solution temperature is 55.

10. The measuring method according to claim 1 or 2, characterized in that: In step (2), the mass of the crude oil sample is 0.4 to 10 g.

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