1、Designation: D7157 12 (Reapproved 2018)Standard Test Method forDetermination of Intrinsic Stability of Asphaltene-ContainingResidues, Heavy Fuel Oils, and Crude Oils (n-HeptanePhase Separation; Optical Detection)1This standard is issued under the fixed designation D7157; the number immediately follo
2、wing the designation indicates the year oforiginal adoption or, in the case of 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. Scope1.1 This test method
3、covers a procedure for quantifying theintrinsic stability of the asphaltenes in an oil by an automaticinstrument using an optical device.1.2 This test method is applicable to residual products fromthermal and hydrocracking processes, to products typical ofSpecifications D396 Grades No. 5L, 5H, and 6
4、, and D2880Grades No. 3-GT and 4-GT, and to crude oils, providing theseproducts contain 0.5 % by mass or greater concentration ofasphaltenes (see Test Method D6560).1.3 This test method quantifies asphaltene stability in termsof state of peptization of the asphaltenes (S-value), intrinsicstability o
5、f the oily medium (So) and the solvency requirementsof the peptized asphaltenes (Sa).1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated
6、 with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recogniz
7、ed principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D396 Specification for F
8、uel OilsD2880 Specification for Gas Turbine Fuel OilsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4175 Terminology Relating to Petroleum Products, LiquidFuels, and LubricantsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD4870 Test Method for Determi
9、nation of Total Sediment inResidual FuelsD6560 Test Method for Determination of Asphaltenes (Hep-tane Insolubles) in Crude Petroleum and Petroleum Prod-uctsD6792 Practice for Quality Management Systems in Petro-leum Products, Liquid Fuels, and Lubricants TestingLaboratories3. Terminology3.1 Definiti
10、ons:3.1.1 For definitions of some terms used in this test method,refer to Terminology D4175.3.1.2 asphaltenes, n(rarely used in the singular), in petro-leum technology, represent an oil fraction that is soluble in aspecified aromatic solvent but separates upon addition of anexcess of a specified par
11、affinic solvent.3.1.2.1 DiscussionIn this test method, the aromatic sol-vent is toluene and the paraffinic solvent is n-heptane.3.1.3 compatibility, nof crude oils or of heavy fuel oils,the ability of two or more crude oils or fuel oils to blendtogether within certain concentration ranges without ev
12、idenceof separation, such as the formation of multiple phases.1This test method is under the jurisdiction of Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.14 on Stability, Cleanliness and Compatibility of Liquid Fuels.Current e
13、dition approved June 1, 2018. Published June 2018. Originallyapproved in 2005. Last previous edition approved in 2012 as D7157 12. DOI:10.1520/D7157-12R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
14、Standards 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 StatesThis international standard was developed in accordance with internationally recognized princ
15、iples on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.3.1 DiscussionIncompatible heavy fuel oils or crudeoils, when mixed or
16、blended, result in the flocculation orprecipitation of asphaltenes. Some oils may be compatiblewithin certain concentration ranges in specific mixtures, butincompatible outside those ranges.3.1.4 flocculation, nof asphaltenes from crude oils orheavy fuel oils, the aggregation of colloidally disperse
17、d as-phaltenes into visible larger masses which may or may notsettle.3.1.5 peptization, nof asphaltenes in crude oils or heavyoils, the dispersion of asphaltenes to produce a colloidaldispersion.3.1.6 stability reserve, nin petroleum technology, theproperty of an oil to maintain asphaltenes in a pep
18、tized stateand prevent flocculation of asphaltenes.3.1.6.1 DiscussionAn oil with a low stability reserve islikely to undergo flocculation of asphaltenes when stressed (forexample, extended heated storage) or blended with a range ofother oils. Two oils each with a high stability reserve are likelyto
19、maintain asphaltenes in a peptized state and not lead toflocculation when blended together.3.2 Definitions of Terms Specific to This Standard:3.2.1 intrinsic stability (S-value), n of refinery residualstreams, residual fuel oils and crude oils, an indication of thestability or available solvency pow
20、er of an oil with respect toprecipitation of asphaltenes.3.2.1.1 DiscussionSince the equation defining S-value is S=(1+Xmin), where Xminis the minimum volume (in mL) ofparaffinic solvent, n-heptane, to be added to1gofoiltoresultin flocculation of asphaltenes, the smallest S-value is 1, whichmeans th
21、e oil is unstable and can precipitate asphalteneswithout addition of any paraffinic solvent. A higher S-valueindicates that an oil is more stable with respect to flocculationof asphaltenes. S-value by this test method relates specificallyto toluene and n-heptane as the aromatic and paraffinicsolvent
22、s, respectively.3.2.2 inversion point, npoint in the n-heptane titrationcurve, where the onset of asphaltene flocculation leads toinversion of the light intensity.3.2.2.1 DiscussionAt the first stage of the addition ofn-heptane to a dilution of specimen and toluene, light intensityincreases through
23、dilution. When asphaltenes start toflocculate, there will be a point where the increase in lightintensity through dilution matches the light intensity decrease(inversion) as a result of coagulated asphaltenes obstructing thelight beam.3.2.3 Sa, nthe S-value of an asphaltene, which is thepeptizabilit
24、y or ability of an asphaltene to remain in a colloidaldispersion.3.2.3.1 DiscussionSa can also be described as one minusthe ratio of So to S. Sa is linked to the length and number ofaromatic chains within the asphaltenes.3.2.4 So, nthe S-value of an oil.3.2.4.1 DiscussionSo can also be described as
25、the aro-matic equivalent of the oil expressed as the ratio of thearomatic solvent to the aromatic plus paraffinic solvent mixturehaving the same peptizing power as the oil.3.2.5 solvent aromaticity, nof a binary mixture of aparaffnic and an aromatic solvent, the solvency power of thebinary mixture.3
26、.2.5.1 DiscussionFor the purpose of this test method,solvent aromaticity is defined as a ratio by volume of thearomatic solvent (toluene) to the paraffinic solvent (n-heptane).3.3 Symbols:FR = flocculation ratioFRmax= maximum flocculation ratioS = the intrinsic stability of an oilSa = the peptizabil
27、ity of an asphalteneSo = the peptizing power of an oilXmin= paraffinic solvent consumption of undiluted oil, inmL/g of oil4. Summary of Test Method4.1 This test method uses an integrated automated analyticalmeasurement system with an optical probe for the detection ofasphaltene precipitation from a
28、toluene solution of the sample.4.2 Three test specimens are dissolved in three differentquantities of toluene. The three specimen/toluene solutions areautomatically and simultaneously titrated with n-heptane tocause precipitation of the asphaltenes. The optical probemonitors the formation of floccul
29、ated asphaltenes during thetitration. Flocculated asphaltenes will alter the detected lightintensity. Start of flocculation is interpreted when the opticalprobe detects a significant and sustained decrease in rate-of-change of the light intensity.4.3 A computer routine calculates stability parameter
30、s andsubsequently the intrinsic stability of the oil from the addedn-heptane at the inversion point, the mass of specimen, and thevolume of toluene, for the three specimen/toluene solutions.5. Significance and Use5.1 This test method describes a sensitive method forestimating the intrinsic stability
31、 of an oil. The intrinsic stabilityis expressed as S-value. An oil with a low S-value is likely toundergo flocculation of asphaltenes when stressed (forexample, extended heated storage) or blended with a range ofother oils. Two oils each with a high S-value are likely tomaintain asphaltenes in a pep
32、tized state and not lead toasphaltene flocculation when blended together.5.2 This test method can be used by petroleum refiners tocontrol and optimize the refinery processes and by blenders andmarketers to assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.6. Interferenc
33、es6.1 High content of insoluble inorganic matter (sediment)has some interference in this test method. In this case, theinsoluble matter shall be removed by filtration according toTest Method D4870.6.2 Free water present in the oil can cause difficulties withthe optical detector and should be removed
34、 by any suitablemeans (for example, centrifugation) prior to testing.D7157 12 (2018)27. Apparatus7.1 General(See Fig. 1) This test method uses an inte-grated automated analytical measurement system3,4comprisedof a PC-based computer and three titration stations.7.1.1 Computer, PC-based computer with
35、associatedsoftware, capable of controlling up to three independenttitration stations, controlling test sequencing, and acquisition ofoptical probe signal data. The associated software also pro-vides for processing calculations and automatically produces areport of important test parameters.7.1.2 Tit
36、ration Stations:7.1.2.1 Titration Unit, automatic computer controlled, ad-justable motor-driven ceramic piston pump, capable of deliv-ering solvent at a rate of 0.01 mL s to 0.5 mL s, with a volumedispensing accuracy of 60.01 mL.7.1.2.2 Magnetic Stirrer, adjustable from 200 r min to400 r min.7.1.2.3
37、 Optical Probe, consisting of a system of three areasof light emitters (880 nm) and three areas of light receivers.The analytical measurement system will automatically selectthe optimum area, based on the level of translucency of thesample.7.1.2.4 Titration Cell, of borosilicate glass, flat bottom,o
38、utside diameter 30 mm 6 2 mm, volume 95 mL 6 15 mL,fitted with a tapered ground glass joint (female).7.2 Balance, capable of reading to 0.1 mg or better.7.3 Dispenser, capable of delivering up to 10 mL of toluenewith an accuracy of 60.1 mL.7.4 Condenser, double surface with a tapered ground-glassjoi
39、nt (male) at the bottom to fit the top of the titration cell.7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from100 r min to 1000 r min.7.6 Stirring Bar, magnetic, PFTE-coated, 20 mm in length.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.
40、Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh
41、purity to permit its use without lessening the accuracy ofthe determination.8.1.1 Toluene. (WarningFlammable. Health hazard. Va-por may cause flash fire.) (See Annex A1.)8.1.2 n-Heptane. (WarningFlammable. Vapor harmful.Vapor may cause flash fire.) (See Annex A1.)8.2 Quality Control SampleA stable a
42、nd homogeneousresidual fuel oil having physical and chemical propertiessimilar to those of typical sample fuels routinely tested.9. Sampling and Test Specimens9.1 Sampling:3The sole source of supply of the apparatus (Automated Stability Analyser)known to the committee at this time is Rofa France, 6
43、Rue Raymond Poincare,F-25300, LesAllies, France. If you are aware of alternative suppliers, please providethis information to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee,1whichyou may attend.4The Rofa stability
44、analyzer is covered by a patent; INPI, date 18/05/04,registration number 04.05406; Rofa France, 6 Rue Raymond Poincare, F-25300, LesAllies, France.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlis
45、ted 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.FIG. 1 Schematic Drawing of the Integrated Automated Stability Analyse
46、r SystemD7157 12 (2018)39.1.1 Obtain representative samples in accordance withrecognized sampling procedures such as Practices D4057 orD4177.9.1.2 Samples of very viscous materials may be warmeduntil they are reasonably fluid before they are sampled.9.1.3 Store samples prior to taking test specimens
47、 at ambi-ent temperatures.9.2 Test Specimen Preparation:9.2.1 Sample TemperatureIf necessary, warm viscoussamples until they can be mixed readily before opening thestorage container. For fuels with a high wax content (high pourpoint) the temperature must be at least 15 C above the pourpoint.9.2.2 Ma
48、nually shake the sample thoroughly. If the samplecontains high content of insoluble inorganic matter, filter thesample through a 47 mm diameter glass fiber filter medium(such as Whatman Grade GF/A), using the Test Method D4870filtration apparatus. Specimen should be representative of thewhole sample
49、.9.3 Preparation of Specimen DilutionsPrepare three dilu-tions of specimen in toluene in different ratios (see Table 1)asfollows:9.3.1 Place a magnetic stirrer bar into a clean titration cell.9.3.2 Add the required amount of specimen to the titrationcell and obtain the mass of the specimen to the nearest 0.001 g(Moil).9.3.3 Add the appropriate volume of toluene to the nearest0.1 mL to the titration cell.9.3.4 Stir dilutions of sample Type 1, without heating, for atleast two minutes. Obtain the mass of the specimen plustoluene to the nearest 0.001 g
