1、Designation: D 7157 05An American National StandardStandard Test Method forDetermination of Intrinsic Stability of Asphaltene-ContainingResidues, Heavy Fuel Oils, and Crude Oils (n-Heptane PhaseSeparation; Optical Detection)1This standard is issued under the fixed designation D 7157; the number imme
2、diately following 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 Thi
3、s test method 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 D 396 Grades No
4、. 5L, 5H, and 6, and D 2880Grades No. 3-GT and 4-GT, and to crude oils, providing theseproducts contain 0.5 mass% or greater concentration of as-phaltenes (see Test Method D 6560).1.3 This test method quantifies asphaltene stability in termsof state of peptization of the asphaltenes (S-value), intri
5、nsicstability of the oily medium (So) and the solvency requirementsof the peptized asphaltenes (Sa).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, associated with its use. It is theresponsibility of
6、 the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use2. Referenced Documents2.1 ASTM Standards:2D 396 Specification for Fuel OilsD 2880 Specification for Gas Turbine Fuel OilsD 4057 Practice for Manual
7、 Sampling of Petroleum andPetroleum ProductsD 4175 Terminology Relating to Petroleum, PetroleumProducts, and LubricantsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 4870 Test Method for Determination of Total Sediment inResidual FuelsD 6560 Test Method for Determination
8、of Asphaltenes(Heptane Insolubles) in Crude Petroleum and PetroleumProductsD 6792 Guide for a Quality System in Petroleum Productsand Lubricant Testing Laboratories3. Terminology3.1 Definitions:3.1.1 For definitions of some terms used in this test method,refer to Terminology D 4175.3.1.2 asphaltene,
9、 nin petroleum technology, a moleculeof high molecular mass, high carbon/hydrogen ratio, andcontaining hetero-atoms.3.1.2.1 DiscussionAsphaltenes are found largely in crudeoils and in heavy fuel oils containing residual fractions. Theyare insoluble in alkanes such as n-heptane and cetane, butsoluble
10、 in aromatic solvents such as benzene, toluene, and1-methylnaphthalene.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 evidenceof separation, such as the formation of multiple ph
11、ases.3.1.3.1 DiscussionIncompatible heavy fuel oils or crudeoils, when mixed or 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 asphal
12、tenes from crude oils orheavy fuel oils, the aggregation of colloidally dispersed 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,
13、nin petroleum technology, theproperty of an oil to maintain asphaltenes in a peptized stateand prevent flocculation of asphaltenes.1This test method is under the jurisdiction of Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.14 onStability and
14、Cleanliness of Liquid Fuels.Current edition approved May 1, 2005. Published May 2005.2For 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
15、page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.6.1 DiscussionAn oil with a low stability reserve islikely to undergo flocculation of asphaltenes when stressed (forexample, extended heated storage) or blen
16、ded with a range ofother oils. Two oils each with a high stability reserve are likelyto 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), nof refinery residualstreams, res
17、idual fuel oils and crude oils, an indication of thestability or available solvency power of an oil with respect toprecipitation of asphaltenes.3.2.1.1 DiscussionSince the equation defining S-value isS =(1+Xmin), where Xminis the minimum volume (in mL) ofparaffinic solvent, n-heptane, to be added to
18、1gofoiltoresultin flocculation of asphaltenes, the smallest S-value is 1, whichmeans the 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 me
19、thod relates specificallyto toluene and n-heptane as the aromatic and paraffinic sol-vents, 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 addi
20、tion ofn-heptane to a dilution of specimen and toluene, light intensityincreases through dilution. When asphaltenes start to floccu-late, there will be a point where the increase in light intensitythrough dilution matches the light intensity decrease (inver-sion) as a result of coagulated asphaltene
21、s obstructing the lightbeam.3.2.3 Sa, nthe S-value of an asphaltene, which is thepeptizability 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 th
22、e asphaltenes.3.2.4 So, nthe S-value of an oil.3.2.4.1 DiscussionSo can also be described as 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 bi
23、nary mixture of aparaffnic and an aromatic solvent, the solvency power of thebinary mixture.3.2.5.1 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 r
24、atioFRmax= maximum flocculation ratioS = the intrinsic stability of an oilSa = the peptizability of an asphalteneSo = the peptizing power of an oilXmin= paraffinic solvent consumption of undiluted oil,in mL/g of oil4. Summary of Test Method4.1 This test method uses an integrated automated analytical
25、measurement system with an optical probe for the detection ofasphaltene precipitation from a 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
26、 tocause precipitation of the asphaltenes. The optical probemonitors the formation of flocculated asphaltenes during thetitration. Flocculated asphaltenes will alter the detected lightintensity. Start of flocculation is interpreted when the opticalprobe detects a significant and sustained decrease i
27、n rate-of-change of the light intensity.4.3 A computer routine calculates stability parameters 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 a
28、nd Use5.1 This test method describes a sensitive method forestimating the intrinsic stability 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 (for ex-ample, extended heated storage) or blended with a r
29、ange ofother oils. Two oils each with a high S-value are likely tomaintain asphaltenes in a peptized 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
30、 assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.6. Interferences6.1 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 D 4870.6.2 Fre
31、e water present in the oil can cause difficulties withthe optical detector and should be removed by any suitablemeans (for example, centrifugation) prior to testing.7. Apparatus7.1 General(See Fig. 1) This test method uses an inte-grated automated analytical measurement system3,4comprisedof a PC-bas
32、ed computer and three titration stations.7.1.1 Computer, PC-based computer with associated soft-ware, capable of controlling up to three independent titrationstations, controlling test sequencing, and acquisition of optical3The sole source of supply of the apparatus (Automated Stability Analyser)kno
33、wn to the committee at this time is Rofa France, 6 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
34、committee,1whichyou may attend.4The Rofa stability analyzer is covered by a patent; INPI, date 18/05/04,registration number 04.05406. Interested parties are invited to submit informationregarding the identification of an alternative(s) to this patented item to the ASTMInternational Headquarters. You
35、r comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.D7157052probe signal data. The associated software also provides forprocessing calculations and automatically produces a report ofimportant test parameters.7.1.2 Titration Stations:
36、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 to 0.5 mL/s, with a volumedispensing accuracy of 60.01 mL.7.1.2.2 Magnetic Stirrer, adjustable from 200 to 400 r/min.7.1.2.3 Optical Probe, consisting
37、 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,outside diameter 30 6 2 mm,
38、 volume 95 6 15 mL, fitted witha 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-glassjoint (male) at the bottom to fit t
39、he top of the titration cell.7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from100 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. Unless otherwise indicated, it is inte
40、nded 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 purity to permit its use without lesse
41、ning 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 and homogeneousresidual fuel oil having p
42、hysical and chemical propertiessimilar to those of typical sample fuels routinely tested.9. Sampling and Test Specimens9.1 Sampling:9.1.1 Obtain representative samples in accordance withrecognized sampling procedures such as Practices D 4057 orD 4177.9.1.2 Samples of very viscous materials may be wa
43、rmeduntil they are reasonably fluid before they are sampled.9.1.3 Store samples prior to taking test specimens 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 fue
44、ls with a high wax content (high pourpoint) the temperature must be at least 15C above the pourpoint.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annu
45、al 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 Analyser SystemD71570539.2.2 Manually shake the sampl
46、e 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 MethodD 4870 filtration apparatus. Specimen should be representativeof the whole sample.9.3 Preparation of S
47、pecimen 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 0.001g(Moil).9.
48、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 (M1). Proceed with Section 12.9.3.5 For specimen dilutions of Type
49、2 and 3, place acondenser on the titration cell, place on the hot plate, and boilunder reflux, while stirring, for a minimum of 10 min forspecimens of Type 2 and for a minimum of 15 min forspecimens of Type 3.9.3.6 Discontinue heating and while stirring, allow thedilutions to cool to ambient temperature. Disconnect thecondenser and obtain the mass of specimen plus toluene to thenearest 0.001 g (M1). Proceed with Section 12.NOTE 1In this context, “liquid” means the minimum temperature atwhich the product has sufficient fluidity to be handled as a liquid.10. P
