1、Designation: D7157 09D7157 12 An American National StandardStandard 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 numb
2、er immediately 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*
3、1.1 This test method covers a procedure for quantifying the intrinsic stability of the asphaltenes in an oil by an automaticinstrument using an optical device.1.2 This test method is applicable to residual products from thermal and hydrocracking processes, to products typical ofSpecifications D396 G
4、rades No. 5L, 5H, and 6, and D2880 Grades No. 3-GT and 4-GT, and to crude oils, providing these productscontain 0.5 mass% or greater concentration of asphaltenes (see Test Method D6560).1.3 This test method quantifies asphaltene stability in terms of state of peptization of the asphaltenes (S-value)
5、, intrinsic stabilityof the oily medium (So) and the solvency requirements of the peptized asphaltenes (Sa).1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety co
6、ncerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use2. Referenced Documents2.1 ASTM Standards:2D396 Specification for Fuel OilsD2880 Spe
7、cification for Gas Turbine Fuel OilsD4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4175 Terminology Relating to Petroleum, Petroleum Products, and LubricantsD4177 Practice for Automatic Sampling of Petroleum and Petroleum ProductsD4870 Test Method for Determination of Total S
8、ediment in Residual FuelsD6560 Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum ProductsD6792 Practice for Quality System in Petroleum Products and Lubricants Testing Laboratories3. Terminology3.1 Definitions:3.1.1 For definitions of some terms used
9、in this test method, refer to Terminology D4175.3.1.2 asphaltene,asphaltenes, n(rarely used in the singular), in petroleum technology, a molecule of high molecular mass, highcarbon/hydrogen ratio, and containing hetero-atoms.represent an oil fraction that is soluble in a specified aromatic solvent b
10、utseparates upon addition of an excess of a specified paraffinic solvent.3.1.2.1 DiscussionAsphaltenes are found largely in crude oils and in heavy fuel oils containing residual fractions. They are insoluble in alkanes such1 This test method is under the jurisdiction of Committee D02 on Petroleum Pr
11、oducts and Lubricants and is the direct responsibility of Subcommittee D02.14 on Stabilityand Cleanliness of Liquid Fuels.Current edition approved June 1, 2009Nov. 1, 2012. Published July 2009February 2013. Originally approved in 2005. Last previous edition approved in 20052009 asD715705.09. DOI: 10
12、.1520/D7157-09.10.1520/D7157-12.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM
13、standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all
14、cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1as In this t
15、est method, the n-heptane and cetane, but soluble in aromatic solvents such as benzene, toluene, and1-methylnaphthalene. aromatic solvent 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 t
16、o blend togetherwithin certain concentration ranges without evidence of separation, such as the formation of multiple phases.3.1.3.1 DiscussionIncompatible heavy fuel oils or crude oils, when mixed or blended, result in the flocculation or precipitation of asphaltenes. Someoils may be compatible wit
17、hin certain concentration ranges in specific mixtures, but incompatible outside those ranges.3.1.4 flocculation, nof asphaltenes from crude oils or heavy fuel oils, the aggregation of colloidally dispersed asphaltenes intovisible larger masses which may or may not settle.3.1.5 peptization, nof aspha
18、ltenes in crude oils or heavy oils, the dispersion of asphaltenes to produce a colloidal dispersion.3.1.6 stability reserve, nin petroleum technology, the property of an oil to maintain asphaltenes in a peptized state and preventflocculation of asphaltenes.3.1.6.1 DiscussionAn oil with a low stabili
19、ty reserve is likely to undergo flocculation of asphaltenes when stressed (for example, extended heatedstorage) or blended with a range of other oils. Two oils each with a high stability reserve are likely to maintain asphaltenes in apeptized state and not lead to flocculation when blended together.
20、3.2 Definitions of Terms Specific to This Standard:3.2.1 intrinsic stability (S-value), n of refinery residual streams, residual fuel oils and crude oils, an indication of the stabilityor available solvency power of an oil with respect to precipitation of asphaltenes.3.2.1.1 DiscussionSince the equa
21、tion defining S-value is S = (1 + Xmin), where Xmin is the minimum volume (in mL) of paraffinic solvent, n-heptane,to be added to 1 g of oil to result in flocculation of asphaltenes, the smallest S-value is 1, which means the oil is unstable and canprecipitate asphaltenes without addition of any par
22、affinic solvent.Ahigher S-value indicates that an oil is more stable with respectto flocculation of asphaltenes. S-value by this test method relates specifically to toluene and n-heptane as the aromatic andparaffinic solvents, respectively.3.2.2 inversion point, npoint in the n-heptane titration cur
23、ve, where the onset of asphaltene flocculation leads to inversion ofthe light intensity.3.2.2.1 DiscussionAt the first stage of the addition of n-heptane to a dilution of specimen and toluene, light intensity increases through dilution. Whenasphaltenes start to flocculate, there will be a point wher
24、e the increase in light intensity through dilution matches the light intensitydecrease (inversion) as a result of coagulated asphaltenes obstructing the light beam.3.2.3 Sa, nthe S-value of an asphaltene, which is the peptizability or ability of an asphaltene to remain in a colloidaldispersion.3.2.3
25、.1 DiscussionSa can also be described as one minus the ratio of So to S.Sa is linked to the length and number of aromatic chains within theasphaltenes.3.2.4 So, nthe S-value of an oil.3.2.4.1 DiscussionSo can also be described as the aromatic equivalent of the oil expressed as the ratio of the aroma
26、tic solvent to the aromatic plusparaffinic solvent mixture having the same peptizing power as the oil.3.2.5 solvent aromaticity, nof a binary mixture of a paraffnic and an aromatic solvent, the solvency power of the binarymixture.D7157 1223.2.5.1 DiscussionFor the purpose of this test method, solven
27、t aromaticity is defined as a ratio by volume of the aromatic solvent (toluene) to theparaffinic solvent (n-heptane).3.3 Symbols:FR = flocculation ratioFRmax = maximum flocculation ratioS = the intrinsic stability of an oilSa = the peptizability of an asphalteneSo = the peptizing power of an oilXmin
28、 = paraffinic solvent consumption of undiluted oil, in mL/g of oil4. Summary of Test Method4.1 This test method uses an integrated automated analytical measurement system with an optical probe for the detection ofasphaltene precipitation from a toluene solution of the sample.4.2 Three test specimens
29、 are dissolved in three different quantities of toluene. The three specimen/toluene solutions areautomatically and simultaneously titrated with n-heptane to cause precipitation of the asphaltenes. The optical probe monitors theformation of flocculated asphaltenes during the titration. Flocculated as
30、phaltenes will alter the detected light intensity. Start offlocculation is interpreted when the optical probe detects a significant and sustained decrease in rate-of-change of the light intensity.4.3 A computer routine calculates stability parameters and subsequently the intrinsic stability of the o
31、il from the addedn-heptane at the inversion point, the mass of specimen, and the volume of toluene, for the three specimen/toluene solutions.5. Significance and Use5.1 This test method describes a sensitive method for estimating the intrinsic stability of an oil. The intrinsic stability isexpressed
32、as S-value. An oil with a low S-value is likely to undergo flocculation of asphaltenes when stressed (for example,extended heated storage) or blended with a range of other oils. Two oils each with a high S-value are likely to maintain asphaltenesin a peptized state and not lead to asphaltene floccul
33、ation when blended together.5.2 This test method can be used by petroleum refiners to control and optimize the refinery processes and by blenders andmarketers to assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.6. Interferences6.1 High content of insoluble inorganic ma
34、tter (sediment) has some interference in this test method. In this case, the insolublematter shall be removed by filtration according to Test Method D4870.6.2 Free water present in the oil can cause difficulties with the optical detector and should be removed by any suitable means(for example, centr
35、ifugation) prior to testing.7. Apparatus7.1 General(See Fig. 1) This test method uses an integrated automated analytical measurement system3,4 comprised of aPC-based computer and three titration stations.7.1.1 Computer, PC-based computer with associated software, capable of controlling up to three i
36、ndependent titration stations,controlling test sequencing, and acquisition of optical probe signal data. The associated software also provides for processingcalculations and automatically produces a report of important test parameters.7.1.2 Titration Stations:7.1.2.1 Titration Unit, automatic comput
37、er controlled, adjustable motor-driven ceramic piston pump, capable of deliveringsolvent at a rate of 0.01 to 0.5 mL/s, with a volume dispensing 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 three areas of light emitt
38、ers (880 nm) and three areas of light receivers. Theanalytical measurement system will automatically select the optimum area, based on the level of translucency of the sample.7.1.2.4 Titration Cell, of borosilicate glass, flat bottom, outside diameter 30 6 2 mm, volume 95 6 15 mL, fitted with a tape
39、redground glass joint (female).3 The sole source of supply of the apparatus (Automated Stability Analyser) known 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 provide this information to ASTM Intern
40、ational Headquarters. Your comments will receive carefulconsideration at a meeting of the responsible technical committee,1 which you may attend.4 The 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, Les
41、Allies,France.D7157 1237.2 Balance, capable of reading to 0.1 mg or better.7.3 Dispenser, capable of delivering up to 10 mL of toluene with an accuracy of 60.1 mL.7.4 Condenser, double surface with a tapered ground-glass joint (male) at the bottom to fit the top of the titration cell.7.5 Magnetic St
42、irrer/Hotplate, stirrer speed adjustable from 100 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 be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the speci
43、fications of the Committee on Analytical Reagents of the American Chemical Society where suchspecifications are available.5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.
44、8.1.1 Toluene. (WarningFlammable. Health hazard. Vapor 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 homogeneous residual fuel oil having physical and chemical properties sim
45、ilar tothose of typical sample fuels routinely tested.9. Sampling and Test Specimens9.1 Sampling:9.1.1 Obtain representative samples in accordance with recognized sampling procedures such as Practices D4057 or D4177.9.1.2 Samples of very viscous materials may be warmed until they are reasonably flui
46、d before they are sampled.9.1.3 Store samples prior to taking test specimens at ambient temperatures.9.2 Test Specimen Preparation:9.2.1 Sample TemperatureIf necessary, warm viscous samples until they can be mixed readily before opening the storagecontainer. For fuels with a high wax content (high p
47、our point) the temperature must be at least 15C above the pour point.9.2.2 Manually shake the sample thoroughly. If the sample contains high content of insoluble inorganic matter, filter the samplethrough a 47-mm diameter glass fiber filter medium (such as Whatman Grade GF/A), using the Test Method
48、D4870 filtrationapparatus. Specimen should be representative of the whole sample.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for L
49、aboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.FIG. 1 Schematic Drawing of the Integrated Automated Stability Analyser SystemD7157 1249.3 Preparation of Specimen DilutionsPrepare three dilutions 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 titration cell and obtain the mass of the specimen to the nea
