ASTM D6470-1999(2015) 6388 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 2015)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 tu

4、rbine 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 fo

6、r 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 ProductsD4

7、377 Test Method for Water in Crude Oils by Potentiomet-ric Karl Fischer TitrationD4928 Test Method for Water in Crude Oils by CoulometricKarl 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 65 C 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 of100 mL, or more, and drawn out at one end to an opening ofinside dia

13、meter (I.D.) 2 mm to 3 mm. A pipette with cut-off tipmakes a suitable sample tube.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved

14、April 1, 2015. Published May 2015. Originallyapproved in 1999. Last previous edition approved in 2010 as D6470 99 (2010).DOI: 10.1520/D6470-99R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards

15、 volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.4 Potentiometric Titration Equipment, with a measuringaccuracy of 62 mV, or better, provided with a

16、 silver indicatingand 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 mixe

17、r with counter-rotating bladesoperating at approximately 3000 r min (50/s) is usually suit-able for homogenization of samples up to 500 mL. Otherdesigns can also be used provided the performance conforms tothe requirements described in Annex A1.5.7 Oven, explosion-proof, temperature 65 C 6 5 C.5.8 F

18、ilter Paper, Whatman No. 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

19、 available.36.2 Purity of WaterFor all purposes where water ismentioned, reagent water of a suitable purity shall be used.Various types of reagent water are described in SpecificationD1193.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Sug

20、gestions on the testing of reagents notlisted by the American Chemical Society, 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

21、 is used.FIG. 1 Extraction ApparatusD6470 99 (2015)26.3 Acetone (2-propanone) , conforming to SpecificationD329.(WarningExtremely flammable. Vapors may causeflashfire.)6.4 Alcohol, for example, 95 % (V/V) ethanol, or propan-2ol (isopropyl alcohol), conforming to Specification D770.(WarningFlammable.

22、)6.5 Barium Nitrate, A.R., 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) to1 L with water. (WarningCorrosive. Caus

23、es skin burns.)6.7 Nitric 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)=0.1 mol L, aqueous. Prepare, standardize and store as de-scrib

24、ed in Practice E200 for 0.1 N aqueous solution, readingconcentrations in mol/L in place of normality. Restandardizeregularly, but in any case before preparation of the standard0.01 mol L solution (see 6.9)NOTE 1Alternatively, ampoules containing concentrated solutions forpreparation of standard volu

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

26、 recently restandardized 0.1 mol Lsilver nitrate solution (Warning see 6.8) to a tenfold volumewith water.6.10 Sodium Chloride Solution, approximately 1 mmol L,aqueous. Dissolve 59 mg 6 1 mg sodium chloride in 1 Lwater.6.11 Xylene, conforming to Specification D843.(WarningXylene presents a health ri

27、sk if incorrectlyhandled. 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 representati

28、ve of the contents of any 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 f

29、or reliable results, strict 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 D41

30、77 shall be used for this 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

31、 sample.7.4 Homogenize the 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 C to 25 C), or less, in the laboratory samplecontainer, and record the temperature of the sample in degreesCels

32、ius immediately before mixing. Heat waxy samples, solidat room temperature, to 3 C 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-tion

33、s for the homogenization test (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,50 mL

34、 to 500 mL, a nonaerating, high speed (3000 r min),shear mixer is required. Use the mixing time, mixing speed,and height above the bottom of the container found to besatisfactory to Annex A1. For larger containers and volumes,appropriate mixing conditions shall be defined by following aset of proced

35、ures similar to those outlined in Annex A1 andPractice D4177 but modified for application to the largercontainers and volumes. Clean and dry the mixer betweensamples.7.6 Record the temperature of the sample immediately afterhomogenization. The rise in temperature between this readingand the initial

36、reading prior to mixing (see 7.4) shall not exceed10 C, 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 homogeni

37、zation by lowering thetip of the 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 re

38、sulting hazards, introduce a gentle 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 b

39、ung in the top of the thistle tube. 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 titratio

40、n (or each seriesof titrations), rinse the electrode with water and soak it for atleast 10 min in 0.1 mol L hydrochloric acid (see 6.6). ThenD6470 99 (2015)3rinse again with water. After titrations store the electrodeimmersed in reagent water.8.2.2 Silver ElectrodePolish the silver electrode beforee

41、ach set of titrations with polishing paper (see 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 to65 C 6 5 C. Heat 40 mL 6 1 mL of xylene to the samete

42、mperature and add slowly to the sample while stirringconstantly until dissolution is complete. Transfer the solutionquantitatively to the extraction apparatus, rinsing the beakerwith two separate portions of 15 mL 6 1 mL of hot xylene andadding these rinsings also to the extraction apparatus.9.1.2 W

43、hile the solution is still hot, add 25 mL 6 1mLofethanol or isopropyl alcohol and 15 mL 6 1 mL of acetone,using these portions for further rinsing of the beaker. Switch onthe heating element of the extraction apparatus to full heat untilboiling begins, then adjust the rheostat to regulate the heat t

44、omaintain boiling at a vigorous rate, but not at 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 mL 61 mL of water and again bring the liquid to the boi

45、l and refluxfor a further 15 min.9.1.3 Switch off the heater, and allow the two phases toseparate for 5 min to 10 min. Draw off the aqueous phase,filtering through a filter paper into a conical flask of suitablecapacity, stopper the flask, and retain the contents for the totalhalide determination as

46、 described in 9.2 and 9.3.9.2 Removal of Sulfur-Containing CompoundsPipet50.0 mL of the aqueous extract (see 9.1.3) into a beaker, andadd 5 mL of 5 mol L nitric acid (see 6.7). Cover the beakerwith a watch-glass, and bring the contents to the boil. Test thevapors periodically for hydrogen sulfide wi

47、th lead acetatepaper and continue boiling for a further 5 min after a negativeresult has been obtained. Allow the contents of the beaker tocool and quantitatively transfer to a 250 mL titration vessel,rinsing the beaker with water. (WarningHydrogen sulfidepresents a health risk if incorrectly handle

48、d. Avoid inhalation.Extract escaping gas by working in 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 to150 mL with acetone (see Note 3

49、). Add approximately 0.5 g ofbarium nitrate crystals. 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 s