石油馏分及工业脂肪族烯烃中溴值检测方案(自动电位滴定)

APAT-0239en京都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD. APAT-0239er Application Note Bromine numbers of petroleum distillates andaliphatic olefins by potentiometric titration IndustryChemicalsInstrumentAutomatic potentiometric titratorMeasurement methodPotentiometric titrationStandardsASTMD1159-07 1. Scope Caution This measurement is performed using organic solvents and strong acids. When youfollow this application note， wear masks， gloves， protective equipments， etc. Theautomatic potentiometric titrator should be installed and used in fume hoods wherelocal exhaust ventilation is possible. The bromine number is the number of grams of bromine added to carbon-carbon unsaturatedbonds in 100 g of petroleum fraction， expressed as gBr2/100 g， and is measured as a valueindicating the number of unsaturated components contained in petroleum products. Thisapplication shows an example of bromine number measurement based on ASTM D1159-07(Note1). The measurement sample was prepared by dissolving cyclohexene in dichloromethane to aknown concentration (approximately 30 gBr2/100 g) (reaction formula (1)). 2.Precautions 1) To suppress side reactions during titration， cool the solution to 5 ℃ or less duringmeasurement. 2) Before starting measurements each day， purge the titrant several times between the reagentbottle and the burette to equalize the titrant concentration， then discharge about 10 mL of thetitrant between the burette and the titration nozzle. 3. Apparatus Main unit Automatic potentiometric titrator (Preamplifier POT)Electrode Blank test and measurement Twin platinum electrode (M-511)Temperature compensation electrode (T-171) 4.Reagents Titrant 0.25 mol/L Bromide-bromate standard solution (potassium bromide andpotassium bromate) Dissolve 51.0 g of potassium bromide (KBr) and 13.92 g of potassiumbromate (KBrO3) each dried at 105 ℃ for 30 min， in pure water and dilute to1L. Titration solvent A solution consisting of a mixture of 714 mL of acetic acid， 134 mL ofdichloromethane， 134 mL of methanol， and 18 mL of sulfuric acid (1+5). 5. Procedure -Preparation of sample solution- 1) Add 10 mL of dichloromethane into a 50 mL volumetric flask. 2) Add around 4-5 g of cyclohexene into the flask and measure the mass of it (approximately30 gBr2/100 g). 3) Add dichloromethane to the mark of the flask and mix it. -Setting of the constant current value- 1) Cool the solution to 0-5 ℃， then press [Calibration] button. 2) Set Channel/Unit to“Ch3/Pol”. 3) Press [Details] button and set as follows.Calibration Mode CurrentPolar Current 10.00 uA 4) Immerse the twin platinum electrode in titration solvent and perform calibration. -Blank test- 1) Collect 5 mL of dichloromethane and mix with 110 mL of the titration solvent. 2) Cool the solution to 0-5C， then titrate with 0.25 mol/L Bromide-bromate standard solution -Measurement- 1) Collect 5 mL of the sample solution* and mix with 110 mL of titration solvent. .2) Cool the solution to 0-5℃， then titrate with 0.25 mol/L Bromide-bromate standard solution . *1 To avoid phase separation， adjust the sample collection volume so that the titration volumeis less than 20 mL. 6. Calculation Bromine number (gBr2/100 g)=(EP1-BL1)×TF×C1×K1×R/S EP1 Titration amount (mL) BL1 Titration amount (mL) of blank test=0.0377(mL) Factor of titrant = 1.005 Concentration conversion coefficient=39.95 Unit conversion factor =0.1 0c Sample size=4.6716 (g) R Dilution coefficient (10) 7.Example 一Parameter —IntermitLevel StopEnd Point No0.End Level (mV)1110.0GainMax Volume0.15 (mL) (blank test)Data SamplingSetData Samplin4g.5 (mL)(sample)999.0Pot.(mV)Data Sampling VolChannel/Unit(Ctrl.)Ch3，mV0.0050 (blank test)(mL)Channel/Unit (Ref.)Off0.1000 (sample)pH PolarityStandardControl Speed ModeSetTitr. Type CheckNo CheckCut-Off time10DirectionAutoUnit Volume. 0.0050 (blank test)Wait Time0 (blank test)0.1000 (sample)30 (sample)Dispense SpeedDose ModeNoneOther ControlSetTitr. over vol.2.00 (blank test)End Time(S)30Stirrer Speed4 (The above condition is an example. The setting condition depends on the model.) 一Example of titration curve一 一Measurement results - Table 1 Measurement result Sample (g) Titration (mL) Bromine number (gBr2/100 g) 1 4.6716 3.4699 29.50 2 4.6716 3.5615 30.29 3 4.6716 3.5653 30.32 Average 30.04 SD 0.38 RSD(%) 1.26 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 8. Notes Note 1) The bromine produced at reaction formula (2) below is reacted with the carbon-carbonunsaturated bonds of the sample (formula (1) above). 5KBr + KBrO3+3H2SO4→3Br2+3K2SO4+3H2O (2) According to the standard， the endpoint of the titration is defined as the potential stable pointwhere the titration is stopped for 30 seconds after a drastic potential change at the equivalencepoint. 9. Reference ASTM D1159-07 Standard Test Method for Bromine Numbers of Petroleum Distillates andCommercial Aliphatic Olefins by Electrometric Titration / 京都电子工业株式会社-可睦电子(上海)商贸有限公司电话： 电邮： kemu-kem@com上海市徐汇区宜山路网址： http：//www.kem-china. com/京都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD. 石油馏分及工业脂肪族烯烃溴值的测定 应用资料(英文版)根据ASTM D1159 电化学滴定法测量石油馏分及商用脂族烯烃的溴值试验方法。将已知质量的试样溶解于温度维持在0ºC～5ºC的溶剂中，然后用溴化钾-溴酸钾标准溶液滴定。当溶液中出现的游离溴引起电位滴定仪的电位突然改变时，即表示达到滴定终点。