1、Designation: D 7157 09An 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 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 asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if
6、any, 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 use2. Referenced Documents2.1 ASTM Standards:2D 396 Specification for Fuel OilsD 2880 Specifica
7、tion for Gas Turbine Fuel OilsD 4057 Practice for Manual 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 Sedime
8、nt inResidual FuelsD 6560 Test Method for Determination of Asphaltenes(Heptane Insolubles) in Crude Petroleum and PetroleumProductsD 6792 Practice for Quality System in Petroleum Productsand Lubricants Testing Laboratories3. Terminology3.1 Definitions:3.1.1 For definitions of some terms used in this
9、 test method,refer to Terminology D 4175.3.1.2 asphaltene, 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 ins
10、oluble in alkanes such as n-heptane and cetane, butsoluble 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 e
11、videnceof separation, such as the formation of multiple phases.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, butincomp
12、atible outside those ranges.3.1.4 flocculation, nof asphaltenes 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
13、to produce a colloidaldispersion.3.1.6 stability reserve, 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 dir
14、ect responsibility of Subcommittee D02.14 onStability and Cleanliness of Liquid Fuels.Current edition approved June 1, 2009. Published July 2009. Originally approvedin 2005. Last previous edition approved in 2005 as D 715705.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
15、tact 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 the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
16、t 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 blended with a range ofother oils. Two oils each with a high stability reserve are likelyto mainta
17、in 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, residual fuel oils and crude oils, an indication of thestability or available solvency power of a
18、n 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 to1gofoiltoresultin flocculation of asphaltenes, the smallest S-value is 1, whichmeans the oil i
19、s 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 paraffinic sol-vents, re
20、spectively.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 dilut
21、ion. 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 asphaltenes obstructing the lightbeam.3.2.3 Sa, nthe S-value of an asphaltene, which is thepeptizability
22、 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 t
23、he 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.
24、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 peptizabili
25、ty 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 analyticalmeasurement system with an optical probe for the detection ofasphaltene precipitation from a t
26、oluene 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 floccula
27、ted 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 parameters
28、 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
29、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 range ofother oils. Two oils each with a high S-value are likely tomaintain asphaltenes in a pe
30、ptized 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. Interferen
31、ces6.1 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 Free water present in the oil can cause difficulties withthe optical detector and should be remov
32、ed 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-based computer and three titration stations.7.1.1 Computer, PC-based computer with associated sof
33、t-ware, capable of controlling up to three independent titrationstations, controlling test sequencing, and acquisition of opticalprobe signal data. The associated software also provides for3The sole source of supply of the apparatus (Automated Stability Analyser)known to the committee at this time i
34、s 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 committee,1whichyou may attend.4Th
35、e Rofa stability 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.D7157092processing calculations and automatically produces a report ofimportant test parameters.7.1.2 Titration Stations:7.1.2.1 Titrati
36、on 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 of a system of
37、 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, volume 95 6 15
38、 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 the top of the t
39、itration 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 intended thatall re
40、agents 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 lessening the accura
41、cy 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 physical and che
42、mical 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 warmeduntil they
43、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 the5Reagent Chemicals, American Chemical Soc
44、iety 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., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacope
45、ial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Schematic Drawing of the Integrated Automated Stability Analyser SystemD7157093storage container. For fuels with a high wax content (high pourpoint) the temperature must be at least 15C above the pourpoint.9.2.2 Manually shake the sample thoroughly. I
46、f 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 Specimen Dilutio
47、nsPrepare 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).9.3.3 Add the app
48、ropriate 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 2 and 3, place
49、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. Preparation of
