Standard substance for simulating acidity of product oil and preparation method thereof

Abstract

The standard substance for simulating the acidity of the product oil comprises benzoic acid and low-carbon alcohol, the purity of the benzoic acid is not lower than 99.8 wt%, and the low-carbon alcohol is one of methanol, ethanol or propanol; the concentration of the standard substance is 1 to 10 mgKOH / 100 mL, preferably 2 to 7 mgKOH / 100 mL. The acidity standard substance is good in accuracy, fills the blank that no acidity standard substance exists at present, and has wide application prospects in the aspects of calibration of a petroleum product acidity tester, confirmation of an acidity measuring method, instrument quality control and the like.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry, specifically relating to a standard substance for simulating the acidity of finished oil products and its preparation method. Technical Background

[0002] Generally, the more acidic substances a refined oil contains, the higher its acidity and the stronger its corrosiveness. Acidic substances in oil are formed during oxidation during storage and use, and their corrosiveness increases further when they absorb moisture from the air. For example, using diesel fuel with high acidity can corrode the fuel supply system, increase carbon deposits in diesel engines, leading to accelerated piston wear and nozzle corrosion and coking. Accurate measurement of petroleum product acidity is crucial for the production, use, storage, and transportation of refined oil. However, there is currently a lack of acidity standard materials. Both acid value and acidity are measured in KOH, but the difference between mg / g and mg / 100mL requires density conversion and is on the order of 100. Therefore, current calibration methods for petroleum product acid value analyzers and the existing acid value standard materials cannot calibrate these instruments due to differences in methods and values. To fill this gap in acidity standard materials, this invention uses high-purity organic acid standard materials as raw materials to formulate a simulated refined oil acidity standard material, which not only achieves traceability but also ensures measurement accuracy.

[0003] CN106370713A discloses a method for detecting arsenic content in light gaseous olefins. This method utilizes an acidic absorption solution composed of bromine water, hydrogen peroxide, hydrochloric acid, and nitric acid to enrich the arsenic in the olefins, followed by microcoulometric determination of the arsenic content. This method can rapidly and accurately detect the arsenic content in gaseous olefins, overcoming the shortcomings of existing methods such as long analysis times and inaccurate results. Summary of the Invention

[0004] The purpose of this invention is to provide a standard substance for simulating the acidity of finished oil and its preparation method, for the purpose of achieving accurate and rapid measurement of the acidity of finished oil.

[0005] A standard substance simulating the acidity of finished oil products includes benzoic acid as a solute and a low-carbon alcohol as a solvent. The benzoic acid is a nationally certified standard substance with a purity of not less than 99.8 wt%, and the low-carbon alcohol is one of methanol, ethanol, or isopropanol. The concentration of the standard substance is 1-10 mg KOH / 100 mL, preferably 2-7 mg KOH / 100 mL.

[0006] The method for preparing the simulated finished oil acidity standard material includes the following steps:

[0007] (1) Pretreatment of solute benzoic acid: Dry benzoic acid at 50-60℃ for 3-5 hours, and then place it in a desiccator to cool to room temperature.

[0008] (2) Keep the solvent low-carbon alcohol in a water bath at 20°C for 4-6 hours;

[0009] (3) Accurately weigh a certain mass of solute and add it to the solvent obtained in step (2), make up the volume, and mix thoroughly to prepare a simulated finished oil acidity standard substance.

[0010] The solvent in step (2) is a low-carbon alcohol, which is an organic solvent such as isopropanol, ethanol, or methanol, preferably isopropanol; the purity of the solvent is greater than 99.5 wt%, more preferably greater than 99.9 wt%.

[0011] In step (3), the acidity is calculated according to the following formula.

[0012]

[0013] X s =X×100 (3)

[0014] In the formula:

[0015] n—Amount of benzoic acid, in mol;

[0016] m1 — Mass of benzoic acid, mg;

[0017] ω — Purity of benzoic acid, %;

[0018] M1—Molecular weight of benzoic acid, g / mol, 122.12134 g / mol;

[0019] X — Acidity of the standard substance, mg / mL;

[0020] V—Preparation volume, mL;

[0021] M2—Molecular weight of potassium hydroxide, g / mol, 56.10564 g / mol;

[0022] 100 — Converted to the volume of the standard reference material specified in the standard, in mL

[0023] X s — Convert to the acidity unit of the standard substance specified in the standard, mg / 100mL.

[0024] After the simulated finished oil acidity standard substance solution is prepared, it is dispensed into 50mL to 100mL brown glass bottles and stored in a refrigerator at 4℃. Before use, it needs to be brought to room temperature, and the minimum sampling amount is 10mL to 30mL.

[0025] The accurate weighing should be performed using a balance of 0.01% or 0.01% based on the amount of the simulated finished oil acidity standard substance prepared. The volumetric flask should also be selected according to the amount of the simulated finished oil acidity standard substance prepared, choosing different models and specifications of Grade A volumetric flasks. Then, the calculation should be performed according to the formula in step (3) of this invention. When verifying the mass value of the simulated finished oil acidity standard substance, a calibrated sampler should be used for sampling, and the sampling temperature should be controlled at 20±3℃.

[0026] The beneficial effects of this invention are as follows:

[0027] The series of standard substances prepared by the method of this invention have low uncertainty and good accuracy, filling the current gap in the availability of acidity standard substances. They have broad application prospects in the calibration of petroleum product acidity analyzers, the confirmation of acidity measurement methods, and instrument quality control. Furthermore, this invention uses high-purity organic acid standard substances, ensuring traceability; and by using high-purity solvents, it avoids the drawbacks of complex matrix components and poor stability in petroleum products such as diesel oil, resulting in high accuracy and stability. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments.

[0029] Example 1

[0030] Before preparation, the benzoic acid purity standard material with a purity of 99.8% was dried in an oven at 60℃ for 4 hours, and then placed in a desiccator to cool to room temperature.

[0031] The high-purity isopropanol solvent was kept at a constant temperature in a water bath at 20°C for 4 hours.

[0032] Accurately weigh 0.00281 g of benzoic acid purity standard material with a purity of 99.8%, dilute it with high-purity organic solvent to a 100 mL volumetric flask, and calculate according to formula (1). Taking this 100mL standard solution as a unit, the standard solution consumes the same amount of potassium hydroxide. According to formula (2), the following can be calculated: X is obtained by converting according to formula (3). s =X×100=0.01288×100=1.288mg / 100mL, then the acidity of the prepared standard substance is 1.288mg / 100mL.

[0033] After preparation, dispense the contents into brown glass bottles and store them in a 4°C refrigerator. Before use, allow the contents to cool to room temperature, and the minimum sample size is 20 mL.

[0034] Uncertainty of the standard value of the acidity reference material for simulated finished oil products, u(X) s )

[0035] According to the aforementioned formulas (1), (2), and (3), since the input quantities in the measurement model of the measurand are multiplicative, the relative combined standard uncertainty can be expressed as:

[0036]

[0037] Right now:

[0038]

[0039] a. The component u introduced by weighing the standard substance r (m)

[0040] Weigh 0.00281 g of standard substance using an analytical balance with a range of 200 g and a graduation of 0.01 mg. The maximum permissible error of the balance is ±1.0e, which is 0.1 mg. Assuming uniform distribution, then:

[0041]

[0042] b. The component u introduced by the purity of the standard substance r (ω)

[0043] The expanded uncertainty and coverage factor of the standard value can be found on the certificate of the standard reference. The uncertainty U of the benzoic acid purity standard reference is also available. r =0.4% (k=2), then

[0044] u r (ω) = 0.4% / 2 = 0.2%

[0045] c. The component introduced by the molecular weight of benzoic acid, u r (M1)

[0046] The molecular formula of benzoic acid is C6H5COOH

[0047] Since M1 = 12.0107 × 7 + 1.00794 × 6 + 15.9994 × 2 = 122.12134

[0048]

[0049] According to the latest internationally published table of relative atomic masses of elements:

[0050] A r (C) = 12.0107(8), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0051] u[A r (C)]=0.0008,u[Ar (O)]=0.0003, u[A r [(H)] = 0.00007

[0052]

[0053] u r (M2)=0.0022 / 122.12134×100%=0.0018%

[0054] d. The component u introduced by the volumetric error of the volumetric flask r (V)

[0055] The maximum permissible error in volume of a Class A 100mL volumetric flask is ±0.1mL. Assuming it follows a triangular distribution, the standard uncertainty introduced by the volumetric flask volume is: The volumetric uncertainty introduced by temperature differences during volumetric flask and solution calibration, assuming a temperature difference of 2℃, is estimated to have an amplified coefficient of organic solvent volume expansion of 1.1 × 10⁻⁶. -3 / ℃, then the volume change is 100×2×1.1×10 -3 =0.22 mL. Assuming the effect of temperature change follows a normal distribution with a coverage probability of 95%, the standard uncertainty introduced by the resulting volume change is 0.22 / 1.96 = 0.11 mL.

[0056]

[0057] e. The component introduced by the molecular weight of potassium hydroxide, u r (M2)

[0058] Potassium hydroxide has the molecular formula KOH

[0059] Since M2 = 39.0983 + 15.9994 + 1.00794 = 59.10564

[0060]

[0061] According to the latest internationally published table of relative atomic masses of elements:

[0062] A r (K)=39.0983(1), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0063] u[A r (K)]=0.0001, u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0064]

[0065] u r (M2)=0.00032 / 56.10564×100%=0.00057%

[0066] f. Uncertainty of combined standard value u(X) s )

[0067] according to

[0068] u(X s )=1.288×2.2%=0.028mg / 100mL

[0069] g. Taking the coverage factor k = 2, the expanded uncertainty of the prepared 1.288 mg / 100 mL simulated finished oil acidity standard is:

[0070] Its value can be expressed as: 1.288mg / 100mL±0.056mg / 100mL. It can be seen that the prepared simulated oil acid value standard substance has low uncertainty and high accuracy.

[0071] (6) The results of the verification using a petroleum product acidity analyzer manufactured according to GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" are as follows:

[0072]

[0073] Since GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" does not specify the reproducibility and repeatability limits for fully automated instruments, according to the latest draft of GB / T 258, the reproducibility limit requirement for fully automated instruments is R = 0.6636·X. 0.24 At the measurement point of 1.288 mg / 100 mL (KOH), the reproducibility limit R is required to be 0.705 mg / 100 mL (KOH), and the indicated error is -0.178 mg / 100 mL (KOH), which is much less than 1 / 3·R. Therefore, it can be concluded that the prepared standard substance has an accurate value.

[0074] Example 2

[0075] Before preparation, the benzoic acid purity standard material with a purity of 99.8% was dried in an oven at 60℃ for 5 hours, and then placed in a desiccator to cool to room temperature.

[0076] The high-purity isopropanol solvent was kept at a constant temperature in a water bath at 20°C for 4 hours.

[0077] Accurately weigh 0.00711 g of benzoic acid purity standard material with a purity of 99.8%, dilute it with high-purity organic solvent to a 100 mL volumetric flask, and calculate according to formula (1). Taking this 100mL standard solution as a unit, the standard solution consumes the same amount of potassium hydroxide. According to formula (2), the following can be calculated: X is obtained by converting according to formula (3). s =X×100=0.03260×100=3.260mg / 100mL, then the acidity of the prepared standard substance is 3.260mg / 100mL.

[0078] After preparation, dispense the contents into brown glass bottles and store them in a 4°C refrigerator. Before use, allow the contents to cool to room temperature, and the minimum sample size is 20 mL.

[0079] Uncertainty of the standard value of the acidity reference material for simulated finished oil products, u(X) s )

[0080] According to the aforementioned formulas (1), (2), and (3), since the input quantities in the measurement model of the measurand are multiplicative, the relative combined standard uncertainty can be expressed as:

[0081]

[0082] Right now:

[0083]

[0084] a. The component u introduced by weighing the standard substance r (m)

[0085] Weigh 0.00711 g of standard substance using an analytical balance with a range of 200 g and a graduation of 0.01 mg. The maximum permissible error of the balance is ±1.0e, which is 0.1 mg. Assuming uniform distribution, then:

[0086]

[0087] b. The component u introduced by the purity of the standard substance r (ω)

[0088] The expanded uncertainty and coverage factor of the standard value can be found on the certificate of the standard reference. The uncertainty U of the benzoic acid purity standard reference is also available. r =0.4% (k=2), then

[0089] u r (ω) = 0.4% / 2 = 0.2%

[0090] c. The component introduced by the molecular weight of benzoic acid, u r (M1)

[0091] The molecular formula of benzoic acid is C6H5COOH

[0092] Since M1 = 12.0107 × 7 + 1.00794 × 6 + 15.9994 × 2 = 122.12134

[0093]

[0094] According to the latest internationally published table of relative atomic masses of elements:

[0095] A r (C) = 12.0107(8), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0096] u[A r (C)]=0.0008,u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0097]

[0098] u r (M2)=0.0022 / 122.12134×100%=0.0018%

[0099] d. The component u introduced by the volumetric error of the volumetric flask r (V)

[0100] The maximum permissible error in volume of a Class A 100mL volumetric flask is ±0.1mL. Assuming it follows a triangular distribution, the standard uncertainty introduced by the volumetric flask volume is: The volumetric uncertainty introduced by temperature differences during volumetric flask and solution calibration, assuming a temperature difference of 2℃, is estimated to have an amplified coefficient of organic solvent volume expansion of 1.1 × 10⁻⁶. -3 / ℃, then the volume change is 100×2×1.1×10 -3 =0.22 mL. Assuming the effect of temperature change follows a normal distribution with a coverage probability of 95%, the standard uncertainty introduced by the resulting volume change is 0.22 / 1.96 = 0.11 mL.

[0101]

[0102] e. The component introduced by the molecular weight of potassium hydroxide, u r (M2)

[0103] Potassium hydroxide has the molecular formula KOH

[0104] Since M2 = 39.0983 + 15.9994 + 1.00794 = 59.10564

[0105]

[0106] According to the latest internationally published table of relative atomic masses of elements:

[0107] A r (K)=39.0983(1), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0108] u[A r (K)]=0.0001, u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0109]

[0110] u r (M2)=0.00032 / 56.10564×100%=0.00057%

[0111] f. Uncertainty of combined standard value u(X) s )

[0112] according to

[0113] u(X s )=3.260×0.83%=0.027mg / 100mL

[0114] g. Taking the coverage factor k = 2, the expanded uncertainty of the prepared 3.260 mg / 100 mL simulated finished oil acidity standard is:

[0115] Its value can be expressed as: 3.260mg / 100mL±0.054mg / 100mL. It can be seen that the prepared simulated oil acid value standard substance has low uncertainty and high accuracy.

[0116] (6) The results of the verification using a petroleum product acidity analyzer manufactured according to GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" are as follows:

[0117]

[0118] Since GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" does not specify the reproducibility and repeatability limits for fully automated instruments, according to the latest draft of GB / T 258, the reproducibility limit requirement for fully automated instruments is R = 0.6636·X. 0.24 At the measurement point of 3.260 mg / 100 mL (KOH), the reproducibility limit R is required to be 0.881 mg / 100 mL (KOH), and the indicated error is -0.184 mg / 100 mL (KOH), which is much less than 1 / 3·R. Therefore, it can be concluded that the prepared standard substance has an accurate value.

[0119] Example 3

[0120] Before preparation, the benzoic acid purity standard material with a purity of 99.8% was dried in an oven at 60℃ for 4 hours, and then placed in a desiccator to cool to room temperature.

[0121] The high-purity isopropanol solvent was kept at a constant temperature in a water bath at 20°C for 4 hours.

[0122] Accurately weigh 0.0112 g of benzoic acid purity standard material (99.8%), dilute it with high-purity organic solvent to a 100 mL volumetric flask, and calculate according to formula (1). Taking this 100mL standard solution as a unit, the standard solution consumes the same amount of potassium hydroxide. According to formula (2), the following can be calculated: X is obtained by converting according to formula (3). s =X×100=0.05135×100=5.135mg / 100mL, then the acidity of the prepared standard substance is 5.135mg / 100mL.

[0123] After preparation, dispense the contents into brown glass bottles and store them in a 4°C refrigerator. Before use, allow the contents to cool to room temperature, and the minimum sample size should be greater than 10 mL.

[0124] Uncertainty of the standard value of the acidity reference material for simulated finished oil products, u(X) s )

[0125] According to the aforementioned formulas (1), (2), and (3), since the input quantities in the measurement model of the measurand are multiplicative, the relative combined standard uncertainty can be expressed as:

[0126]

[0127] Right now:

[0128]

[0129] a. The component u introduced by weighing the standard substance r (m)

[0130] Weigh 0.0112 g of standard substance using an analytical balance with a range of 200 g and a graduation of 0.1 mg. The maximum permissible error of the balance is ±1.0e, which is 1 mg. Assuming uniform distribution, then:

[0131]

[0132] b. The component u introduced by the purity of the standard substance r (ω)

[0133] The expanded uncertainty and coverage factor of the standard value can be found on the certificate of the standard reference. The uncertainty U of the benzoic acid purity standard reference is also available. r =0.4% (k=2), then

[0134] u r (ω) = 0.4% / 2 = 0.2%

[0135] c. The component introduced by the molecular weight of benzoic acid, u r (M1)

[0136] The molecular formula of benzoic acid is C6H5COOH

[0137] Since M1 = 12.0107 × 7 + 1.00794 × 6 + 15.9994 × 2 = 122.12134

[0138]

[0139] According to the latest internationally published table of relative atomic masses of elements:

[0140] A r (C) = 12.0107(8), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0141] u[A r (C)]=0.0008,u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0142]

[0143] u r (M2)=0.0022 / 122.12134×100%=0.0018%

[0144] d. The component u introduced by the volumetric error of the volumetric flask r (V)

[0145] The maximum permissible error in volume of a Class A 100mL volumetric flask is ±0.1mL. Assuming it follows a triangular distribution, the standard uncertainty introduced by the volumetric flask volume is: The volumetric uncertainty introduced by temperature differences during volumetric flask and solution calibration, assuming a temperature difference of 2℃, is estimated to have an amplified coefficient of organic solvent volume expansion of 1.1 × 10⁻⁶. -3 / ℃, then the volume change is 100×2×1.1×10 -3 =0.22 mL. Assuming the effect of temperature change follows a normal distribution with a coverage probability of 95%, the standard uncertainty introduced by the resulting volume change is 0.22 / 1.96 = 0.11 mL.

[0146]

[0147] e. The component introduced by the molecular weight of potassium hydroxide, u r (M2)

[0148] Potassium hydroxide has the molecular formula KOH

[0149] Since M2 = 39.0983 + 15.9994 + 1.00794 = 59.10564

[0150]

[0151] According to the latest internationally published table of relative atomic masses of elements:

[0152] A r (K)=39.0983(1), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0153] u[A r (K)]=0.0001, u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0154]

[0155] u r (M2)=0.00032 / 56.10564×100%=0.00057%

[0156] f. Uncertainty of combined standard value u(X) s )

[0157] according to

[0158] u(X s)=5.135×5.3%=0.272mg / 100mL

[0159] g. Taking the coverage factor k = 2, the expanded uncertainty of the prepared 5.135 mg / 100 mL simulated finished oil acidity standard is:

[0160] Its value can be expressed as: 5.135mg / 100mL±0.544mg / 100mL. It can be seen that the prepared simulated oil acid value standard substance has low uncertainty and high accuracy.

[0161] The petroleum product acidity analyzer, manufactured according to GB / T 258—2016 "Determination of Acidity of Light Petroleum Products", was validated, and the results are as follows:

[0162]

[0163] Since GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" does not specify the reproducibility and repeatability limits for fully automated instruments, according to the latest draft of GB / T 258, the reproducibility limit requirement for fully automated instruments is R = 0.6636·X. 0.24 At the measurement point of 5.135 mg / 100 mL (KOH), the reproducibility limit requirement R is 0.983 mg / 100 mL (KOH), and the obtained indication error is -0.211 mg / 100 mL (KOH), which is much less than 1 / 3·R. Therefore, it can be concluded that the prepared standard substance has an accurate value.

[0164] Example 4

[0165] Before preparation, the benzoic acid purity standard material with a purity of 99.8% was dried in an oven at 60℃ for 4 hours, and then placed in a desiccator to cool to room temperature.

[0166] The high-purity isopropanol solvent was kept at a constant temperature in a water bath at 20°C for 4 hours.

[0167] Accurately weigh 0.0157 g of benzoic acid purity standard material with a purity of 99.8%, dilute it with high-purity organic solvent to a 100 mL volumetric flask, and calculate according to formula (1). Taking this 100mL standard solution as a unit, the standard solution consumes the same amount of potassium hydroxide. According to formula (2), the following can be calculated: X is obtained by converting according to formula (3). s =X×100=0.07198×100=7.198mg / 100mL, then the acidity of the prepared standard substance is 7.198mg / 100mL.

[0168] After preparation, dispense the contents into brown glass bottles and store them in a 4°C refrigerator. Before use, allow the contents to cool to room temperature, and the minimum sample size should be greater than 5 mL.

[0169] Uncertainty of the standard value of the acidity reference material for simulated finished oil products, u(X) s )

[0170] According to the aforementioned formulas (1), (2), and (3), since the input quantities in the measurement model of the measurand are multiplicative, the relative combined standard uncertainty can be expressed as:

[0171]

[0172] Right now:

[0173]

[0174] a. The component u introduced by weighing the standard substance r (m)

[0175] Weigh 0.0157g of standard substance using an analytical balance with a range of 200g and a graduation of 0.1mg. The maximum permissible error of the balance is ±1.0e, which is 1mg. Assuming uniform distribution, then:

[0176]

[0177] b. The component u introduced by the purity of the standard substance r (ω)

[0178] The expanded uncertainty and coverage factor of the standard value can be found on the certificate of the standard reference. The uncertainty U of the benzoic acid purity standard reference is also available. r =0.4% (k=2), then

[0179] u r (ω) = 0.4% / 2 = 0.2%

[0180] c. The component introduced by the molecular weight of benzoic acid, u r (M1)

[0181] The molecular formula of benzoic acid is C6H5COOH

[0182] Since M1 = 12.0107 × 7 + 1.00794 × 6 + 15.9994 × 2 = 122.12134

[0183]

[0184] According to the latest internationally published table of relative atomic masses of elements:

[0185] A r (C) = 12.0107(8), Ar (O) = 15.9994(3), A r (H) = 1.00794(7)

[0186] u[A r (C)]=0.0008,u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0187]

[0188] u r (M2)=0.0022 / 122.12134×100%=0.0018%

[0189] d. The component u introduced by the volumetric error of the volumetric flask r (V)

[0190] The maximum permissible error in volume of a Class A 100mL volumetric flask is ±0.1mL. Assuming it follows a triangular distribution, the standard uncertainty introduced by the volumetric flask volume is: The volumetric uncertainty introduced by temperature differences during volumetric flask and solution calibration, assuming a temperature difference of 2℃, is estimated to have an amplified coefficient of organic solvent volume expansion of 1.1 × 10⁻⁶. -3 / ℃, then the volume change is 100×2×1.1×10 -3 =0.22 mL. Assuming the effect of temperature change follows a normal distribution with a coverage probability of 95%, the standard uncertainty introduced by the resulting volume change is 0.22 / 1.96 = 0.11 mL.

[0191]

[0192] e. The component introduced by the molecular weight of potassium hydroxide, u r (M2)

[0193] Potassium hydroxide has the molecular formula KOH

[0194] Since M2 = 39.0983 + 15.9994 + 1.00794 = 59.10564

[0195]

[0196] According to the latest internationally published table of relative atomic masses of elements:

[0197] A r (K)=39.0983(1), A r (O) = 15.9994(3), A r (H) = 1.00794(7)

[0198] u[A r (K)]=0.0001, u[A r (O)]=0.0003, u[A r [(H)] = 0.00007

[0199]

[0200] u r (M2)=0.00032 / 56.10564×100%=0.00057%

[0201] f. Uncertainty of combined standard value u(X) s )

[0202] according to

[0203] u(X s )=7.198×3.8%=0.274mg / 100mL

[0204] g. Taking the coverage factor k = 2, the expanded uncertainty of the prepared 7.198 mg / 100 mL simulated finished oil acidity standard is:

[0205] Its value can be expressed as: 7.198mg / 100mL±0.548mg / 100mL. It can be seen that the prepared simulated oil acid value standard substance has little uncertainty and high accuracy.

[0206] The petroleum product acidity analyzer, manufactured according to GB / T 258—2016 "Determination of Acidity of Light Petroleum Products", was validated, and the results are as follows:

[0207]

[0208] Since GB / T 258—2016 "Determination of Acidity of Light Petroleum Products" does not specify the reproducibility and repeatability limits for fully automated instruments, according to the latest draft of GB / T 258, the reproducibility limit requirement for fully automated instruments is R = 0.6636·X. 0.24 At the measurement point of 7.198 mg / 100 mL (KOH), the reproducibility limit R is required to be 1.066 mg / 100 mL (KOH), and the indicated error is 0.03 mg / 100 mL (KOH), which is much less than 1 / 3·R. Therefore, it can be concluded that the prepared standard substance has an accurate value.

[0209] The above embodiments are merely illustrative of the present invention, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art: the materials, reagents, etc. used are all commercially available.

Claims

1. A standard substance simulating the acidity of finished oil products, comprising benzoic acid as a solute and a low-carbon alcohol as a solvent, wherein the benzoic acid is a nationally certified standard substance with a purity of not less than 99.8 wt%, and the low-carbon alcohol is one of methanol, ethanol, or isopropanol; the concentration of the standard substance is 1-10 mg KOH / 100 mL, preferably 2-7 mg KOH / 100 mL.

2. A method for preparing a simulated finished oil acidity standard substance as described in claim 1, comprising the following steps: (1) Pretreatment of solute benzoic acid: Dry benzoic acid at 50-60℃ for 3-5 hours, and then place it in a desiccator to cool to room temperature. (2) Keep the solvent low-carbon alcohol in a water bath at 20°C for 4-6 hours; (3) Accurately weigh a certain mass of solute and add it to the solvent obtained in step (2), make up the volume, and mix thoroughly to prepare a simulated finished oil acidity standard substance.

3. The method according to claim 2, characterized in that, The solvent in step (2) is a low-carbon alcohol, which is an organic solvent such as isopropanol, ethanol, or methanol, preferably isopropanol; the purity of the solvent is greater than 99.5 wt%, more preferably greater than 99.9 wt%.

4. The method according to claim 2, characterized in that, In step (3), the acidity is calculated according to the following formula. X s =X×100 (3) In the formula: n—Amount of benzoic acid, in mol; m1 — Mass of benzoic acid, mg; ω — Purity of benzoic acid, %; M1—Molecular weight of benzoic acid, g / mol, 122.12134 g / mol; X — Acidity of the standard substance, mg / mL; V—Preparation volume, mL; M2—Molecular weight of potassium hydroxide, g / mol, 56.10564 g / mol; 100 — Converted to the volume of the standard reference material specified in the standard, in mL X s — Convert to the acidity unit of the standard substance specified in the standard, mg / 100mL.

5. The method according to claim 2, characterized in that... After the simulated finished oil acidity standard substance solution is prepared, it is dispensed into brown glass bottles and stored in a refrigerator at 4°C. Before use, it needs to be brought to room temperature, and the minimum sample volume is 10-20 mL.

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