ASTM D6470-1999(2010) 1875 Standard Test Method for Salt in Crude Oils (Potentiometric Method)《原油中盐的标准试验方法(电位滴定位)》.pdf

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1、Designation: D6470 99 (Reapproved 2010)Standard Test Method forSalt in Crude Oils (Potentiometric Method)1This standard is issued under the fixed designation D6470; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r

2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of salt incrude oils. For the purpose of this test method, salt is expressedas % (

3、m/m) NaCl (sodium chloride) and covers the range from0.0005 to 0.15 % (m/m).1.2 The limit of detection is 0.0002 % (m/m) for salt (asNaCl).1.3 The test method is applicable to nearly all of the heavierpetroleum products, such as crude oils, residues, and fuel oils.It may also be applied to used turb

4、ine oil and marine diesel fuelto estimate seawater contamination. Water extractable salts,originating from additives present in oils, are codetermined.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does not purport to address all of thesafety concerns, if any,

5、associated with its use. It is theresponsibility of the user 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:2D329 Specification for AcetoneD770 Specification for

6、Isopropyl AlcoholD843 Specification for Nitration Grade XyleneD1193 Specification for Reagent WaterD4006 Test Method for Water in Crude Oil by DistillationD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD437

7、7 Test Method for Water in Crude Oils by Potentio-metric Karl Fischer TitrationD4928 Test Methods for Water in Crude Oils by Coulom-etric Karl Fischer TitrationE200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical Analysis3. Summary of Test Method3

8、.1 After homogenizing the crude oil with a mixer, aweighed aliquot is dissolved in xylene at 65C and extractedwith specified volumes of alcohol, acetone, and water in anelectrically heated extraction apparatus. A portion of theaqueous extract is analyzed for total halides by potentiometrictitration.

9、4. Significance and Use4.1 A knowledge of water extractable inorganic halides inoil is important when deciding whether or not the oils needdesalting. Excessive halide, especially in crude oil, frequentlyresults in higher corrosion rates in refining units.5. Apparatus5.1 Extraction Apparatus, made of

10、 borosilicate glass, con-forming to the dimensions given in Fig. 1, and consisting of thefollowing component parts:5.1.1 Boiling Flask, 500 mL capacity.5.1.2 Hopkins Reflux Condenser, having a vapor outletconnected by a rubber tube to an outside vent or to a suctionhood.5.1.3 Thistle Tube, approxima

11、tely 70 mL capacity, with aline to indicate approximately the 50 mL level.5.1.4 Heating Tube, containing a chimney for increasingconvection in the liquid.5.1.5 Heating Coil, 250 W, consisting of a suitable gage ofNichrome wire.5.1.6 Rheostat, of suitable resistance and capacity, forregulating the he

12、ater.5.2 Safety Shield, colorless safety glass, or equivalent, to bemounted in front of the extraction apparatus (see 5.1).5.3 Sampling Tube, glass, length approximately 600 mm,I.D. approximately 5 mm, with a bulb having a volume of 100mL, or more, and drawn out at one end to an opening of insidedia

13、meter (I.D.) 2 to 3 mm. A pipette with cut-off tip makes asuitable sample tube.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved May 1, 2010. Publ

14、ished May 2010. Originallyapproved in 1999. Last previous edition approved in 2004 as D647099 (2004).DOI: 10.1520/D6470-99R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,

15、 refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Potentiometric Titration Equipment, with a measuringaccuracy of 6 2 mV, or better, provided with a silver indicating

16、and a glass reference electrode and 10 mL burette, preferablypiston type. If an automatic titrator is used, this shall be capableof adding fixed increments of titrant (see 9.3.3.2).5.5 Magnetic Stirrer, with polytetrafluoroethylene (PTFE)-coated stirring bar.5.6 Homogenizer. A mixer with counter-rot

17、ating bladesoperating at approximately 3000 r/min (50/s) is usually suitablefor homogenization of samples up to 500 mL. Other designscan also be used provided the performance conforms to therequirements described in Annex A1.5.7 Oven, explosion-proof, temperature 65 6 5C.5.8 Filter Paper, Whatman No

18、. 41, or equivalent.5.9 Stopwatch.6. Reagents and Materials6.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society where such specifications are available.36.2 Purity

19、of WaterFor all purposes where water ismentioned, reagent water of a suitable purity shall be used.Various types of reagent water are described in SpecificationD1193.6.3 Acetone (2-propanone), conforming to SpecificationD329.(WarningExtremely flammable. Vapors may causeflashfire.)6.4 Alcohol, for ex

20、ample, 95 % (V/V) ethanol, or propan-2ol (isopropyl alcohol), conforming to Specification D770.(WarningFlammable.)3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Soci

21、ety, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.NOTE 1Hopkins-type condenser is used.FIG. 1 Extraction ApparatusD6470 99 (2010)26.5 Barium Nitrate, A.R

22、., crystals. (WarningBariumcompounds and their solutions present a health risk if incor-rectly handled. Prevent all contact.)6.6 Hydrochloric Acid, 0.1 mol/L, aqueous. Add 9 mL ofA.R. concentrated hydrochloric acid (density 1.19 g/mL) to 1 Lwith water. (WarningCorrosive. Causes skin burns.)6.7 Nitri

23、c Acid, 5 mol/L, aqueous. Cautiously add 325 mLof A.R. concentrated nitric acid (density 1.42 g/mL) to 1 Lwater, while stirring. (WarningCorrosive. Causes skinburns.)6.8 Silver Nitrate Solution, standard, c(AgNO3) = 0.1mol/L, aqueous. Prepare, standardize and store as described inPractice E200 for 0

24、.1 N aqueous solution, reading concentra-tions in mol/L in place of normality. Restandardize regularly,but in any case before preparation of the standard 0.01 mol/Lsolution (see 6.9)NOTE 1Alternatively, ampoules containing concentrated solutions forpreparation of standard volumetric solutions are av

25、ailable from varioussuppliers. (WarningSilver compounds and their solutions present ahealth risk if incorrectly handled. Prevent all contact.)6.9 Silver Nitrate Solution, standard, c(AgNO3) = 0.01mol/L, aqueous. Prepare shortly before use by accuratelydiluting one volume of the recently restandardiz

26、ed 0.1 mol/Lsilver nitrate solution (Warningsee 6.8) to a tenfold volumewith water.6.10 Sodium Chloride Solution, approximately 1 mmol/L,aqueous. Dissolve 59 6 1 mg sodium chloride in 1 L water.6.11 Xylene, conforming to Specification D843.(WarningXylene presents a health risk if incorrectlyhandled.

27、 Avoid inhalation. Extract vapor by working in a fumecupboard.)6.12 Lead Acetate Paper.6.13 Polishing Paper, 800 grit, or finer, to polish the silverelectrode.7. Sampling and Sample Preparation7.1 Sampling is defined as all the steps required to obtain analiquot representative of the contents of any

28、 pipe, tank, or othersystem, and to place the sample into the laboratory samplecontainer. The laboratory sample container and sample volumeshall be of sufficient dimensions and volume to allow mixing,as described in 7.4.(WarningThe results of the round robinhave shown that for reliable results, stri

29、ct adherence to thesampling and mixing procedure is of the utmost importance.)7.2 Laboratory SampleThe sample of crude oil presentedto the laboratory or test facility for analysis by this test method.Only representative samples obtained as specified in PracticesD4057 and D4177 shall be used for this

30、 test method.7.3 Test SampleThe sample aliquot obtained from thelaboratory sample for analysis by this test method. Oncedrawn, the entire portion of the test sample will be used in theanalysis. Mix the laboratory sample properly, as described in7.4, prior to drawing the test sample.7.4 Homogenize th

31、e laboratory sample of crude oil imme-diately (within 15 min) before drawing the test sample toensure complete homogeneity. Mix the sample at room tem-perature (15 to 25C), or less, in the laboratory samplecontainer, and record the temperature of the sample in degreesCelsius immediately before mixin

32、g. Heat waxy samples, solidat room temperature, to 3C above their pour point in order tofacilitate test sample withdrawal. Select the type of mixerrelated to the quantity of crude oil in the laboratory samplecontainer. Before any unknown mixer is used, the specifica-tions for the homogenization test

33、 (see Annex A1) shall be met.Reevaluate the mixer for any changes in the type of crude, thequantity of crude, the shape of the sample container, or themixing conditions (such as mixing speed and time of mixing).7.5 For small laboratory sample containers and volumes, 50to 500 mL, a nonaerating, high

34、speed (3000 r/min), shear mixeris required. Use the mixing time, mixing speed, and heightabove the bottom of the container found to be satisfactory toAnnex A1. For larger containers and volumes, appropriatemixing conditions shall be defined by following a set ofprocedures similar to those outlined i

35、n Annex A1 and PracticeD4177 but modified for application to the larger containers andvolumes. Clean and dry the mixer between samples.7.6 Record the temperature of the sample immediately afterhomogenization. The rise in temperature between this readingand the initial reading prior to mixing (see 7.

36、4) shall not exceed10C, otherwise excessive loss of volatile vapors can occur orthe dispersion can become unstable.7.7 In order to ensure that crude oils with rapidly settlingimpurities are properly sampled, withdraw the test samplecontainer immediately after homogenization by lowering thetip of the

37、 sample tube (see 5.3) almost to the bottom of thecontainer, and withdrawing the test sample as quickly aspossible. Clean and dry the sample tube before and aftersampling.8. Preparation of Apparatus8.1 Extraction ApparatusTo reduce the risk of superheat-ing and the resulting hazards, introduce a gen

38、tle stream of airinto the bottom of the extraction apparatus. This can be done bypassing a length of hypodermic tubing through the bore of thetap so that the lower end reaches the bottom of the heatingtube, while the upper end of the tubing is passed through arubber bung in the top of the thistle tu

39、be. Place the extractionapparatus behind a safety screen. Shield all electrical resis-tances and devices; alternatively, remove them from theimmediate vicinity of the extraction apparatus.8.2 Potentiometric Titration Equipment:8.2.1 Glass ElectrodeBefore each titration (or each seriesof titrations),

40、 rinse the electrode with water and soak it for atleast 10 min in 0.1 mol/L hydrochloric acid (see 6.6). Thenrinse again with water. After titrations store the electrodeimmersed in reagent water.8.2.2 Silver ElectrodePolish the silver electrode beforeeach set of titrations with polishing paper (see

41、6.13) until aclean, polished metal surface is obtained.9. Procedure9.1 Extraction:9.1.1 Weigh about 40 g of sample, to the nearest 0.1 g, intoa 250 mL beaker and heat on a water bath or in an oven to 656 5C. Heat 40 6 1 mL of xylene to the same temperature andadd slowly to the sample while stirring

42、constantly untildissolution is complete. Transfer the solution quantitatively toD6470 99 (2010)3the extraction apparatus, rinsing the beaker with two separateportions of 15 6 1 mL of hot xylene and adding these rinsingsalso to the extraction apparatus.9.1.2 While the solution is still hot, add 25 6

43、1mLofethanol or isopropyl alcohol and 15 6 1 mL of acetone, usingthese portions for further rinsing of the beaker. Switch on theheating element of the extraction apparatus to full heat untilboiling begins, then adjust the rheostat to regulate the heat tomaintain boiling at a vigorous rate, but not a

44、t such a rate tocause bumping in the flask or to cause the condenser to flood.Allow to reflux for 2 min after the liquid starts boiling (see8.1). Switch off the heater. When boiling ceases, add 125 6 1mL of water and again bring the liquid to the boil and reflux fora further 15 min.9.1.3 Switch off

45、the heater, and allow the two phases toseparate for 5 to 10 min. Draw off the aqueous phase, filteringthrough a filter paper into a conical flask of suitable capacity,stopper the flask, and retain the contents for the total halidedetermination as described in 9.2 and 9.3.9.2 Removal of Sulfur-Contai

46、ning CompoundsPipet 50.0mL of the aqueous extract (see 9.1.3) into a beaker, and add 5mL of 5 mol/L nitric acid (see 6.7). Cover the beaker with awatch-glass, and bring the contents to the boil. Test the vaporsperiodically for hydrogen sulfide with lead acetate paper andcontinue boiling for a furthe

47、r 5 min after a negative result hasbeen obtained. Allow the contents of the beaker to cool andquantitatively transfer to a 250-mL titration vessel, rinsing thebeaker with water. (WarningHydrogen sulfide presents ahealth risk if incorrectly handled. Avoid inhalation. Extractescaping gas by working in

48、 a fume cupboard.)9.3 Salt Determination:9.3.1 Pipet 10.0 mL of the 1 mmol/L sodium chloridesolution (see 6.10; see Note 2) in the titration vessel (see 9.2).Adjust the volume of the sample solution in the vessel to 150mL with acetone (see Note 3). Add approximately 0.5 g ofbarium nitrate crystals.

49、Stir to dissolve the barium nitrate.NOTE 2To obtain a titration end point even for small amounts ofchloride, a fixed amount of sodium chloride is added to the blank andsample solution.NOTE 3Acetone is added to lower the solubility of the silver chlorideprecipitate.9.3.2 Fill the burette with 0.01 mol/L silver nitrate solution,place the beaker on a magnetic stirrer, and immerse theelectrodes in the sample solution. Immerse the tip of the buretteapproximately 25 mm below the liquid surface, and adjust themagnetic stirrer to produce vigorous stirring witho