ASTM D2710-2009 Standard Test Method for Bromine Index of Petroleum Hydrocarbons by Electrometric Titration《电化学滴定法对石油烃溴指数的测试方法》.pdf

1、Designation: D2710 09Designation: 299/92 (98)Standard Test Method forBromine Index of Petroleum Hydrocarbons by ElectrometricTitration1This standard is issued under the fixed designation D2710; the number immediately following the designation indicates the year oforiginal adoption or, in the case of

2、 revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the amountof bromine-reactive material in petrole

3、um hydrocarbons and isthus a measure of trace amounts of unsaturates in thesematerials. It is applicable to materials having bromine indexesbelow 1000.1.2 This test method is applicable only to essentially olefin-free hydrocarbons or mixtures that are substantially free frommaterial lighter than iso

4、butane and have a distillation end pointunder 288C (550F).NOTE 1This procedure has been cooperatively tested on materialswith bromine indexes in the range from 100 to 1000. These materialsinclude petroleum distillates such as straight-run and hydrocrackednaphtha, reformer feed, kerosine, and aviatio

5、n turbine fuel.NOTE 2Materials with bromine index greater than 1000 should betested for bromine number using Test Method D1159/IP 130.NOTE 3Bromine index of industrial aromatic hydrocarbons should bedetermined using Test Method D1492 or D5776. The subcommittee iscurrently examining ways to achieve m

6、ore consistent end point values.1.3 The values stated in SI units are to be regarded asstandard. The values stated in inch-pound units are for infor-mation only.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us

7、er of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1159 Test Method for Bromine Numbers of PetroleumDistillates and Commercial Aliphatic Olefins by Electro-metri

8、c TitrationD1492 Test Method for Bromine Index of Aromatic Hydro-carbons by Coulometric TitrationD5776 Test Method for Bromine Index of Aromatic Hydro-carbons by Electrometric Titration3. Terminology3.1 Definitions:3.1.1 bromine indexthe number of milligrams of brominethat will react with 100 g of s

9、ample under the conditions of thetest.4. Summary of Test Method4.1 A known mass of the sample dissolved in a specifiedsolvent is titrated with standard bromide-bromate solution. Theend point is indicated by a dead stop electrometric titrationapparatus when the presence of free bromine causes a sudde

10、nchange in the electrical conductivity of the system.5. Significance and Use5.1 This test method provides a measure of trace amounts ofunsaturated hydrocarbons in petroleum distillates boiling up to288C (550F). An estimate of the quantity of these materialsis useful in assessing the suitability of t

11、he lighter fractions foruse as reaction solvents.6. Apparatus6.1 Electrometric End Point Titration ApparatusAny ap-paratus designed to perform titrations to pre-set end points (seeNote 4) may be used in conjunction with a high-resistancepolarizing current supply capable of maintaining approxi-mately

12、 0.8 V across two platinum electrodes and with asensitivity such that a voltage change of approximately 50 mVat these electrodes is sufficient to indicate the end point. Othertypes of commercially available electric titrimeters, includingcertain pH meters, have also been found to be suitable.NOTE 4P

13、re-set end point indicated with polarized electrodes providesa detection technique similar to the dead stop technique specified inprevious versions of this test method.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibili

14、ty of SubcommitteeD02.04.0D on Physical and Chemical Methods.Current edition approved Oct. 1, 2009. Published November 2009. Originallyapproved in 1968. Last previous edition approved in 2004 as D271099(2004)1.DOI: 10.1520/D2710-09.In the IP, this test method is under the jurisdiction of the Standar

15、dizationCommittee.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at t

16、he end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 Titration VesselA jacketed glass vessel of approxi-mately 150-mL capacity of such a form that can be conve-niently maintained at 0 to 5C (32 to 41F). A pair o

17、f platinumelectrodes spaced not more than 5 mm apart shall be mountedto extend well below the liquid level. Stirring shall be by amechanical or electromagnetic stirrer and shall be rapid, butnot so vigorous as to draw air bubbles down to the electrodes.6.3 Burets, 10 and 50-mL capacity.6.4 Iodine Nu

18、mber Flasks, glass-stoppered, 500-mL capac-ity.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the AmericanChemical Society where such specifications are available.3

19、Other grades may be used, providing it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water, or waterof eq

20、uivalent purity.7.3 Preparation and Standardization:7.3.1 Bromide-Bromate Standard Solution (0.05 N)Dissolve 5.1 g of potassium bromide (KBr) and 1.4 g potas-sium bromate (KBrO3) in water and dilute to 1 L. Standardizeto four significant figures as follows: Place 50 mL of glacialacetic acid (Warning

21、Poison. Combustible. May be fatal ifswallowed. Causes severe burns. Harmful if inhaled) and 1 mLof concentrated hydrochloric acid (HCl, sp gr 1.19)(WarningPoison. Corrosive. May be fatal if swallowed.Liquid and vapor cause severe burns. Harmful if inhaled.) in a500-mL iodine number flask. Chill the

22、solution in an ice bathfor approximately 10 min, and with constant swirling of theflask, add from a 50-mL buret 40 to 45 mL of bromide-bromatesolution, estimated to the nearest 0.01 mL, at a rate such thatthe addition takes between 90 and 120 s. Stopper the flaskimmediately, shake the contents, plac

23、e it again in the ice bath,and add 5 mL of potassium iodide (KI) solution in the lip of theflask.After 5 min, remove the flask from the ice bath and allowthe KI solution to flow into the flask by slowly removing thestopper. Shake vigorously, add 100 mL of water in such amanner as to rinse the stoppe

24、r, lip, and walls of the flask, andtitrate promptly with the standard sodium thiosulfate(Na2S2O3) solution. Near the end of the titration, add 1 mL ofstarch indicator solution and titrate slowly to the disappearanceof the blue color. Calculate the normality of the bromide-bromate solution as follows

25、:N15 A2N2/A1(1)where:N1= normality of the bromide-bromate solution,A1= millilitres of the bromide-bromate solution,N2= normality of the Na2S2O3solution, andA2= millilitres of the Na2S2O3solution required for titra-tion of the bromide-bromate solution.7.3.2 Potassium Iodide Solution (150 g/L)Dissolve

26、 150 gof KI in water and dilute to 1 L.7.3.3 Sodium Thiosulfate, Standard Solution (0.05 N)Dissolve 12.5 g of sodium thiosulfate pentahydrate (Na2S2O35H2O) in water and add 0.01 g of sodium carbonate (Na2CO3)to stabilize the solution. Dilute to 1 L and mix thoroughly byshaking. Standardize by any ac

27、cepted procedure that deter-mines the normality with an error not greater than 60.0002.Restandardize at intervals frequent enough to detect changes of0.0005 in normality.7.3.4 Starch Indicator SolutionMix5gofsoluble starchwith approximately 3 to 5 mL of water. If desired, add about0.65 g salicylic a

28、cid as preservative. Add the slurry to 500 mLof boiling water and continue boiling for 5 to 10 min. Allow tocool and decant the supernatant liquid into glass bottles andseal well. Starch solutions (some preserved with salicylic acid)are also commercially available and may be substituted.7.3.5 Sulfur

29、ic Acid (1+5)Carefully add 1 volume ofconcentrated sulfuric acid (H2SO4, sp gr 1.84) to 5 volumes ofwater and thoroughly mix. (WarningPoison. Corrosive.Strong oxidizer. Contact with organic material may cause fire.May be fatal if swallowed.)7.3.6 Titration SolventPrepare 1 L of titration solvent bym

30、ixing the following volumes of materials: 714 mL of glacialacetic acid, 134 mL of 1,1,1-trichloroethane or dichlo-romethane, 134 mL of methanol, and 18 mL of H2SO4(1+5)(see 7.3.5).7.4 Solvents:7.4.1 Acetic Acid, glacial. (WarningPoison. Combus-tible. May be fatal if swallowed. Causes severe burns. H

31、armfulif inhaled.)7.4.2 Methanol (WarningFlammable. Vapor harmful.May be fatal if swallowed. Causes severe burns. Harmful ifinhaled.)7.4.3 1,1,1-Trichloroethane (WarningHarmful if inhaled.High concentrations may cause unconsciousness or death.Contact may cause skin irritation and dermatitis.)7.4.4 D

32、ichloromethane (WarningHarmful if inhaled.High concentrations may cause unconsciousness or death.Contact may cause skin irritation and dermatitis.)NOTE 5The replacement of 1,1,1-trichloroethane, an ozone-depletingchemical, is necessary because its manufacture and import has beendiscontinued. Dichlor

33、omethane is temporarily being allowed as an alter-native to 1,1,1-trichloroethane until a permanent replacement can beidentified and adopted by ASTM.NOTE 6The user of this test method may choose to use either1,1,1-trichloroethane or dichloromethane to the exclusion of the othersolvent. The selected

34、solvent is to be used for all operations, including thepreparation of the titration solvent and the dilution of samples, ifapplicable.NOTE 7Commercially available reagents can be used in place oflaboratory preparations.8. Procedure8.1 Switch on the titrimeter and allow the electrical circuitsto stab

35、ilize in accordance with the manufacturers instructions.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd

36、., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D2710 0928.2 Cool the titration vessel to 0 to 5C (32 to 41F) bycirculating a suitable coolant through the jacketed titrationvessel.8.3 Introduce 110 mL of titra

37、tion solvent into the titrationvessel and pipet in a quantity of sample as indicated in Table 1.Switch on the stirrer and adjust to a rapid stirring rate, butavoid any tendency for air bubbles to be drawn down into thesolution. Allow the contents to cool to 0 to 5C (32 to 41F)and maintain at this te

38、mperature throughout the titration.(WarningHydrocarbon samples, particularly those boilingbelow 205C (400F), are flammable.)8.3.1 Frequently the order of magnitude of the bromineindex of a sample is unknown. In this case, a trial test isrecommended using an 8 to 10-g sample in order to obtain theapp

39、roximate magnitude of the bromine index. This exploratorytest should be followed with another determination using theappropriate sample size as indicated in Table 1.8.3.2 The sample mass can be determined by obtaining thedensity of the sample and calculating the mass of a measuredvolume.8.4 Set the

40、end point potential. With each instrument, themanufacturers instructions should be followed for end pointsetting and to achieve the sensitivity in the platinum electrodecircuit specified in 6.1.8.5 Depending on the titrator apparatus, add the bromide-bromate solution manually or by microprocessor co

41、ntrol insmall increments from the buret. The end point of the titrationis achieved when the potential reaches the pre-set value (see8.4) and persists for more than 30 s.8.6 BlanksMake duplicate blank titrations on each batchof titration solvent and reagents. Less than 1.0 mL of bromide-bromate solut

42、ion should be required.9. Calculation9.1 Calculate the bromine index as follows:Bromine index 5 A 2 B!N 3 7990/W (2)where:A = millilitres of bromide-bromate solution required fortitration of the sample,B = millilitres of bromide-bromate solution required fortitration of the blank,N = normality of br

43、omide-bromate solution, andW = grams of sample.10. Precision and Bias10.1 Precision:10.1.1 The precision of this test method as obtained bystatistical examination of interlaboratory test results is asfollows:10.1.1.1 RepeatabilityThe difference between successivetest results obtained by the same ope

44、rator with the sameapparatus under constant operating conditions on identical testmaterial would, in the long run, in the normal and correctoperation of the test method, exceed 14 in only one case intwenty.10.1.1.2 ReproducibilityThe difference between twosingle and independent results, obtained by

45、different operators,working in different laboratories on identical test material,would in the long run, in the normal and correct operation ofthe test method, exceed 118 in only one case in twenty.10.2 BiasThe procedure in this test method has no biasbecause the value of bromine index can be defined

46、 only interms of a test method.NOTE 8The precision for this test method was not obtained inaccordance with RR: D02-1007.NOTE 9It is not known whether the precision estimates are applicablewhen using dichloromethane as a constituent of the titration solvent.11. Keywords11.1 bromide-bromate solution;

47、bromine index; electromet-ric titration; hydrocarbons; petroleumANNEX(Mandatory Information)A1. RESULTS OF BROMINE INDEX COOPERATIVE PROGRAMTABLE 1 Sample SizeBromine Index Sample Size,g100 to 500 10 to 8Over 500 to 1000 8 to 4D2710 093SUMMARY OF CHANGESSubcommittee D02.04.0D has identified the loca

48、tion of selected changes to this standard since the last issue(D271099(2004)1) that may impact the use of this standard.(1) Revised 8.6.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this stan

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