石油产品酸值的测定 应用资料

石油产品酸值的测定 应用资料将试样溶解在滴定溶剂中，以氢氧化钾异丙醇标准溶液为滴定剂进行电位滴定，所用的电极对为玻璃指示电极与参比电极或者复合电极。自动绘制电位mV值对应滴定体积的电位滴定曲线，并将明显的突跃点作为终点。APAT-0184en京都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD. APAT-0184en Application Note Determination of the total acid number in petroleumproducts IndustryPetrochemicalsInstrumentAutomatic potentiometric titratorMeasurement methodPotentiometric titration /Neutralization titrationStandardsASTM D664， GB/T 7304 1.Scope Determining the total acid number of petroleum products is important in evaluating their quality，as it indicates factors such as their degree of degradation. This Application Note introduces anexample of the determination of the total acid number of petroleum products in accordance withASTM D664. Mineral oil was used as the analyte， as it is a standard material of known total acid value 2. Precautions 1) After each titration， make sure to immerse the electrode in an aqueous solution of hydrochloricacid solution (pH4.5~5.5) for 5 minutes in order to restore and maintain its proper workingsensitivity. 2) Potassium hydroxide 2-propanol solution should be standardized at intervals where the change inconcentration does not exceed 0.0005 mol/L. 3) To reduce the effect of carbon dioxide in the air， stirring with a stirrer should be controlled ata rotational speed that does not create a vortex on the liquid surface. 4)If the measurement results are not repeatable or the titration curve is unclear， it is possibly due tothe influence of carbon dioxide in the air. To avoid this effect， it is recommended to blow nitrogengas on the surface of the sample solution. 3.Post-measurement procedure After the measurement is completed， the sensitivity of the glass electrodes may have decreased.so perform the sensitivity recovery operation described in "2. Precautions 1)”. Seal the refill port for internal liquid of the reference electrode with a rubber plug so that theinternal liquid is prevented from leaking out or concentrating. Once done， store the electrode inaccordance with the following： ·For short-term storage (less than one month) store immersed in pure water. ·For long-term storage (longer than one month) store immersed in a solution of pH 4standard solution and 3.3 mol/L KCl solution mixed in an equal volume ratio. 4. Apparatus Equipment Automatic potentiometric titrator (preamplifier STD) Electrode Nonaqueous titration combined glass electrode (Electrode liquid 1 mol/L Lithium chloride in ethanol). 京都电子工业株式会社-可睦电子(上海)商贸有限公司电话：021-54488867 电邮： kemu-kem@163.com 5. Reagents Titrant 0.1 mol/L Potassium hydroxide in 2-propanol Solvent A solution of 500 mL of toluene，5 mL of water， and 495 mL of 2-propanol 6. Procedure -Measurement- 1) In accordance with its acid number， a specified quantity of sample (outlined in ASTM D644)is introduced into a beaker and the mass is measured. 2) Add 60 mL of titration solvent and titrate with 0.1 mol/L potassium hydroxide in 2-propanolsolution. 3) A separate blank test is performed to correct the titration volume during sample measurement. 7.Calculation Acid number (mgKOH/g)=(EP1-BL1)xTF×C1×K1/S EP1 Titration amount of sample (mL) BL1 Blank test (mL) =0.0606 Factor of titrant =1.0837 s Concentration conversion coefficient =5.61 mg/mL Unit conversion factor =1 Quantity of sample (g) 8. Example (Measurementor Parameter setting) Titration parameter— Auto Int. EP Stop Burette No.1Number of EP1一Max. Volume10(mL)End SenseSetChannel/Unit(Ctrl.)Chl，mVEP Sense (Potential)20(dE)Channel/Unit(ref.)offEP Sense (Differential)100 (dE/dmL)pH PolarityStandardGainType of TitrationNot checkData SamplingAutoEP DirectionNegativeCtrl. Speed ModesetWait Time10(S)Cut Off Time3(s)Dose ModeNonUnit Volume0.2(mL)Dispense Speed1(s/mL)Other ControlStandardStirrer Speed2 (Listed above are example settings.Availability of settings may vary by instrument model.) 一Measurement results 一 Table.Measurement results Sample Titration Acid number amount (g) (mgKOH/g) (mL) 1 5.0228 4.0973 4.89 2 5.0191 4.1074 4.90 3 5.0065 4.0809 4.88 Mean 4.89 SD 0.01 RSD(%) 0.21 9. Notes In this standard， the endpoint is defined as the point of inflection of the titration curve. If aninflection point cannot be obtained， the endpoint is defined as the point at which the potential ofthe non-aqueous buffer solution reaches the potential specified in the standard. Please contact usif you have any questions. 10. Reference ASTMD664 Standard Test Methods for Acid Number of Petroleum Products by PotentiometricTitration. 京都电子工业株式会社-可睦电子(上海)商贸有限公司电话： 021-54488867 电邮： kemu-kem@163.com 都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD.