石油产品中硫醇硫含量检测方案(自动电位滴定)

京都電子工業株式会社KYOTO ELECTRONICSAPAT-0130enMANUFACTURING CO.，LTD.Application Note APAT-0130er Mercaptan sulfur of petroleum products Industry Petroleum Instrument Automatic potentiometric titrator Measurement method Potentiometric titration/ Precipitation titration Related standard ASTM D3227，JIS K2276 1.Scope Test samples were prepared by dissolving octanethiol in toluene and mercaptan sulfur in thesamples were measured based on“ASTM D3227 Standard Test Method for (Thiol Mercaptan)Sulfur in Gasoline， Kerosene， Aviation Turbine， and Distillate Fuels (Potentiometric Method)”. A test sample dissolved in sodium acetate 2-propanol solution was potentiometrically titratedwith 0.01mol/L silver nitrate 2-propanol solution. An inflection point on the titration curve wasregarded as the endpoint. The quantity of mercaptan sulfur was calculated from the volume ofsilver nitrate 2-propanol solution used to titrate sample to endpoint. 2.Precautions 1) Prepare a fresh silver sulfide coating on the silver electrode each day by the methoddescribed in“6. Procedure， -Preparation of silver/silver-sulfide electrode-“. 2) After each measurement， soak the silver/silver-sulfide electrode into 100mL of titrationsolvent containing 0.5mL of 0.1mol/L silver nitrate 2-propanol solution for 5 minutes. 3) Clean the glass electrode at least once a week by stirring in cold chromic acid solution. 4) 0.1mol/L silver nitrate 2-propanol solution is standardized at an interval not shorter than theconcentration changes by more than 0.0005mol/L. 5) Prepare 0.01mol/L silver nitrate 2-propanol solution daily by diluting 0.1mol/L silver nitrate2-propanol solution by 10 times with 2-propanol. 6) If sample contains hydrogen sulfide (H2S)， remove H2S by the method described in ASTMD3227. 3.Post-measurement procedure 1) Clean the glass electrode with alcohol and keep lower half of the electrode immersedin water. 2) Clean the silver electrode with alcohol and wipe with a soft， clean tissue. Then，keep ina dry condition. 4. Apparatus Main unit Automatic potentiometric titrator (preamplifier： STD) Electrode Silver electrode (with silver sulfide coating) pH glass electrode 5. Reagents ·0.1mol/L silver nitrate 2-propanol solution ·0.01mol/L silver nitrate 2-propanol solution (titrant) ·Sodium acetate 2-propanol solution (titration solvent) Dissolve 1.6g of anhydrous sodium acetate in 25mL of water and pour into 975mL of 2-propanol. ·10g/L sodium sulfide(NazS) aqueous solutionDissolve 10g of anhydrous NazS or 30.6g of Na2S·9H2O in water and dilute to 1L with water. 6. Procedure -Preparation of silver/silver-sulfide electrode- 1) Burnish detection part of electrode with polishing paper. 2) Immerse the electrode in 100mL of titration solvent containing 8mL of sodium sulfidesolution， and then heat the solvent up to 60℃*. 3) Keep the temperature of the solvent at 60℃* and add slowly from a burette， with stirring，10mL of 0.1 mol/L silver nitrate 2-propanol solution over a period from 10 to 15min. 4) Wash the electrode with water and wipe off surplus silver sulfide with a soft， clean tissue.*Though heating operation is not described in the standard， good silver sulfidecoating is formed by this operation. -Blank test- 1) Add 100mL of the titration solvent into a 200mL beaker. 2) Titrate with 0.01mol/L silver nitrate 2-propanol solution to measure blank level. -Measurement- 1) Measure 20~50 mL of the sample with pipet and pour into a 200mL beaker. 2) Add 100mL of the titration solvent. 3) Titrate with 0.01mol/L silver nitrate 2-propanol solution to measure mercaptan sulfurconcentration. 7.Calculation Mercaptan sulfur (mass%)=(EP1-BL1)×TF×C1×K1/S EP1 Titer (mL) BL1 Blank level=0.0000mL Factor of titrant=0.9128 a HS Concentration conversion coefficient =0.32065mg/mL Unit conversion coefficient=0.1 Sample (g) 8.Example -Titration parameter- ： Auto Int.： EP StopNumber ofEP：1End Sense： AutoGain：Max. Volume：20(mL)Data Sampling： AutoChannel/Unit(Ctrl.)： Ch1， mVCtrl. Speed： Standard (Blank test， Sample ①)Channel/Unit(Ref.)：Off： Slow (Sample ②)pH Polarity： StandardOther Ctrl.： StandardTitr. Type Check： No CheckAuto Int. Mode： Blank (Blank test)Direction： Negative： Micro (Sample ①，②)Wait Time： 30(s)Micro Titr. Max.Vol.：1 (mL)Dose Mode： NoneMicro Titr. dE： 50.0 (dE)Micro Titr. dE/dmL：100.0 (dE/dmL)Stirrer Speed：3 (The measurement parameter and the titration curve are an example of our automatic potentiometric titrator.In some titrators， parameter item may be different or another parameter item may be added.) Sample ① -Titration curve- Sample Titer Mercaptan sulfur (mL) (g) (mL) (mass%) 1 20 17.338 5.0813 0.00858 2 20 17.338 5.0865 0.00859 3 20 17.338 5.1184 0.00864 Mean - - 0.00860 SD - - 0.00003 RSD (%) - - - 0.37364 Sample ② -Titration curve- Sample Titer Mercaptan sulfur (mL) (g) (mL) (mass%) 50 43.345 0.6242 0.00042 2 50 43.345 0.6317 0.00043 3 50 43.345 0.6430 0.00043 Mean - 0.00043 SD - - 0.00001 H RSD (%) - - - 1.35316 *Sample ： Sample was collected in fixed volume， and sample volume was converted into weightby the density of sample. 9. Summary Each sample was measured three times and good repeatability was obtained.In some samples， verification of the measurement capability is required. In such case， pleasecontact us. 10.References 1) ASTM D3227-13 Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline， Kerosene，Aviation Turbine， and Distillate Fuels (Potentiometric Method) 2) JIS K2276：2003 Petroleum products - Testing methods for aviation fuels 京都电子工业株式会社-可睦电子(上海)商贸有限公司 电邮： kemu-kem@163.com 都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD 石油产品硫醇硫的测定 应用资料(英文版)根据ASTM D3227 电位差法测定汽油、煤油航空汽轮机燃料及馏分燃料中硫醇态硫含量的试验方法进行测定。在乙酸钠的异丙醇滴定溶剂中溶解，用0.01mol/L硝酸银异丙醇溶液进行电位滴定。以滴定曲线上的一个拐点为终点。硫醇硫的含量由硝酸银异丙醇溶液的体积计算出硫的含量。