ASTM D6703-2007 923 Standard Test Method for Automated Heithaus Titrimetry《自动HEITHAUS滴定分析法用标准试验方法》.pdf

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1、Designation: D 6703 07Standard Test Method forAutomated Heithaus Titrimetry1This standard is issued under the fixed designation D 6703; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthe

2、ses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for quantifyingthree Heithaus compatibility parameters (1,2)2that estimate thecolloidal stability of asphalts and

3、 asphalt cross blends (1,2),aged asphalts (3), and pyrolyzed heavy oil residua and asphalt(4) using automated Heithaus titrimetry as a stability diagnostictool.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the use

4、r 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:3D 3279 Test Method for n-Heptane InsolublesD 4124 Test Methods for Separation of Asphalt into FourFractionsD 554

5、6 Test Method for Solubility of Asphalt Binders inToluene by CentrifugeE 169 Practices for General Techniques of Ultraviolet-Visible Quantitative Analysis3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 asphalt (5), na dark brown to black cementitiousmaterial, solid or semisoli

6、d in consistency, in which thepredominating constituents are bitumen, which occur in natureas such or are obtained as residue by the refining of petroleum.3.1.2 asphalt cross-blend, nany mixture of two or moreasphalts blended together to form a consistent material.3.1.3 asphaltene peptizability, nth

7、e tendency of asphalt-enes to exist as a stable dispersion in a maltene solvent,measured by the Heithaus parameter pa.3.1.4 asphaltenes, nthe high molecular weight hydrocar-bon fraction precipitated from asphalt by a designated paraf-finic naphtha solvent at a specified solvent-asphalt ratio.3.1.4.1

8、 DiscussionThe asphaltene fraction should beidentified by the solvent and solvent-asphalt ratio used.3.1.5 asphalt state of peptization, na measure of theability of the combination of a maltene solvent and dispersedasphaltenes to form a stable dispersed system. Equivalent tocompatibility of the syst

9、em.3.1.6 bitumen, na class of black or dark-colored (solid,semisolid, or viscous) cementitious substances, natural ormanufactured, composed principally of high-molecular weighthydrocarbons, of which asphalts, tars, pitches, and asphaltitesare typical.3.1.7 coke, nthe solid product resulting from the

10、 destruc-tive distillation of coal, petroleum residuum, or bitumen in anoven or closed chamber, or from imperfect combustion of thesematerials, consisting principally of carbon.3.1.8 colloidal suspension, nan intimate mixture of twosubstances, one of which, called the dispersed phase (orcolloid), is

11、 uniformly distributed in a finely divided statethrough the second substance, called the dispersion medium (ordispersing medium).3.1.9 compatibility, nthe state of peptization of an as-phalt, which is measured quantitatively by the Heithaus param-eter P.3.1.10 core asphalts, nthe eight asphalts sele

12、cted forintensive study in the Strategic Highway Research Program(SHRP).3.1.11 dispersed phase, none phase of a dispersion con-sisting of particles or droplets of one substance distributedthrough a second phase.3.1.12 dispersing medium, none phase of a dispersion thatdistributes particles or droplet

13、s of another substance, thedisperse phase.3.1.13 flocculation, nthe process of aggregation and coa-lescence into a flocculent mass.3.1.14 Heithaus compatibility parameters, nthree param-eters: asphaltene peptizability (pa), maltene peptizing power(po), and asphalt state of peptization (P), measured

14、usingHeithaus titration methods.3.1.15 maltene peptizing power, nthe ability of a maltenesolvent to disperse asphaltenes, measured by the Heithausparameter po.1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommitte

15、e D04.47 onMiscellaneous Asphalt Tests.Current edition approved Dec. 1, 2007. Published January 2008. Originallyapproved in 2001. Last previous edition approved in 2001 as D 6703 01.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For referenced ASTM s

16、tandards, 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 page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke

17、n, PA 19428-2959, United States.3.1.16 maltenes, na red-brown to black heavy oil materialderived from asphalt after precipitation with normal orbranched alkanes (for example, n-pentane, n-hexane,n-heptane, isooctane, and so forth), filtration of asphaltenes,and distillation of alkane precipitating a

18、gent from the filtrate.Equivalent to deasphaltened materials. Maltenes are the sol-vent moiety of an asphalt.3.1.17 oxidatively age-hardened asphalt, nan asphalt thathas reacted with oxygen at elevated temperatures in an oven,usually under greater than atmospheric oxygen pressure. Thereaction is run

19、 for a time sufficient to simulate asphalt aging inpavement.3.1.18 pyrolysis, nthe breaking apart of complex mol-ecules into simpler units by the use of heat, as in the pyrolysisof heavy oil to make gasoline.3.1.19 residuum, na quantity or body of matter remainingafter evaporation, combustion, or di

20、stillation.4. Summary of Test Method4.1 Three 30-mL reaction vials are tared. Three samples ofan asphalt (or a heavy oil residuum), one weighing 0.400 g, asecond weighing 0.600 g, and the third weighing 0.800 g, aretransferred to the reaction vials, one sample into each vial.Toluene (3.000 mL) is ad

21、ded to each of the reaction vials todissolve the asphalt (or heavy oil residuum). Each reaction vialcontains a solution which differs by concentration of asphalt(or heavy oil residuum) prepared in toluene. All solutions thatare prepared for a given asphalt material are titrated withisooctane (2,2,4-

22、trimethyl pentane) or some other titrant thatpromotes a flocculation of material within the solution (6)conducted at a constant titrant delivery rate. The titration isperformed by placing the reaction vials separately in theapparatus illustrated in Fig. 1. The apparatus depicted in Fig. 1consists of

23、 intersecting sample circulation and titration loops.4.2 Each reaction vial is separately placed into a 250-mL,water-jacketed reaction vessel (Fig. 1). Water-jacketing isrequired for temperature control of the system. Furthermore,the water-jacketed reaction vessel is filled with enough watersuch tha

24、t the reaction vial and temperature probe are 75 %immersed. Water flowing through the water jacket maintainsthe temperature of the water in the reaction vessel, whichfurther maintains the temperature of the solution in the reactionvial. The connection with the sample circulation loop is madeby cover

25、ing the reaction vial with a screw top TFE-fluorocarbon cover penetrated by three small bore TFE-fluorocarbon tubes (Fig. 2). A fourth hole in the coveraccommodates a temperature probe. One of these tubes(1.6-mm (116-in. diameter) leads to a short path length(0.2-mm) quartz flow cell housed in an ul

26、traviolet- (UV)visible spectrophotometer. A second tube (1.6-mm diameter)leads to a high flow rate metering pump and then to the quartzcell. This system is the sample circulation loop. The third tube(1.6-mm diameter) connects the reaction vial to the titrationloop and leads to a low flow rate meteri

27、ng pump and then toanother water-jacketed reaction vessel filled with titrant (usu-ally iso-octane). This reaction vessel is covered with anotherTFE-fluorocarbon cover penetrated by one TFE-fluorocarbontube. This TFE-fluorocarbon cover has the same dimensions asthe one illustrated in Fig. 2, but doe

28、s not require threadingbecause the cover fits directly over the reaction vessel and novial is screwed into it. Also it has only one hole. The secondreaction vessel is filled with titrant. While the sample solutioncirculates through the sample circulation loop, the titrant ispumped into the sample re

29、action vial at a constant rate usingthe low flow rate metering pump. During this process, theoutput signal from the spectrophotometer is recorded using anintegrator or some other data gathering device. The change inpercent transmittance (%T) of detected radiation at 740 nm (7)passing through the qua

30、rtz cell is plotted versus the time, t,during which the titrant is added to the sample reaction vial.4.3 The spectrophotometer output signal detects the onset ofturbidity of the sample solution. This is the flocculation onsetpoint, corresponding to the beginning of the precipitation ofasphaltenes fr

31、om the sample solution. Fig. 3 illustrates a typicalseries of plots of %T versus t for the three test solutions. Valuesof %T increase with time until maximum values of %T areobserved, after which values of %T decrease. The reason thatthe curves in Fig. 3 exhibit maxima is that, at the beginning ofea

32、ch titration, %T increases due to dilution with titrant. At theflocculation onset point, the formation of asphaltene particlescauses an immediate decrease in %T due to light scatteringeffects. The time required to reach the maximum in %T fromthe onset of titration of a sample is defined as the flocc

33、ulationtime, tf. When the value of tffor each sample is multiplied bythe titrant flow rate, the titrant volume, VT, required to causethe onset of flocculation for each sample is obtained.4.4 The weight of each asphalt (or heavy oil residuum)sample, Wa, the volume of toluene used to dissolve eachsamp

34、le, VS(2.00 mL in each case), and the volume of titrantrequired to cause the onset of flocculation, VTare recorded foreach sample solution. Values of these three quantities for eachset of three test sample solutions are used to calculate thequantities C (referred to as the dilution concentration) an

35、d FR(referred to as the flocculation ratio). C is defined as Wa/(VS+VT). FR is defined as VS/(VS+ VT). Values of C are plottedversus FR for each of the three recorded sets of values of Wa,VS, and VT(Fig. 4). Customarily, the C values are along thex-axis, and the FR values are the y-axis. The three d

36、ata pointsare connected by a line, and the line is extrapolated to bothaxes. The point at which the line intercepts the x-axis is definedas Cmin. The point at which the line intercepts the y-axis isdefined as FRmax. These two values are used to calculate thethree Heithaus compatibility parameters, d

37、esignated pa, po, andP. The parameter pa, the peptizability of asphaltenes, is definedas the quantity (1 FRmax). The parameter po, the peptizingpower of maltenes, is defined as the quantity FRmax(1/Cmin)+1. The parameter P, the overall compatibility of the system, isdefined as po/(1 pa), or (1/Cmin+

38、 1).5. Significance and Use5.1 This test method is intended primarily as a laboratorydiagnostic tool for estimating the colloidal stability of asphalt,asphalt cross blends, aged asphalt, pyrolyzed asphalt, andheavy oil residuum. Historically, asphalt and heavy oil residuahave been modeled as colloid

39、al suspensions (8,9) in which apolar, associated asphaltene moiety (the dispersed phase) issuspended in a maltene solvent moiety (the dispersing me-dium) (refer to test methods D 3279, D 4124, and D 5546 forD6703072FIG.1AutomatedTitrationApparatusD6703073further definition of asphalt fraction materi

40、als). The extent towhich these two moieties remain in a given state of peptizationis a measure of the compatibility of the suspension. Compat-ibility influences important physical properties of these mate-rials, including rheological properties, for example, phaseangle and viscosity (10,11). Compati

41、bility also influences cokeformation in refining processes (4). This test method and othersimilar test methods (7, 12-15), along with the classicalHeithaus test (1,2), measures the overall compatibility of acolloidal system by determining a designated parameter re-ferred to as the state of peptizati

42、on, P. The value of Pcommonly varies between 2.5 and 10 for unmodified or neatasphalts. Materials calculated to have low values of P aredesignated as incompatible, where as materials calculated tohave high P values are designated as compatible. Values of Pmay be calculated as a function of two other

43、 designatedparameters that relate to the peptizability of the asphaltenemoiety (the asphaltene peptizability parameter, pa) and thesolvent power of the maltene moiety (the maltene peptizingpower parameter, po). Values of paand poare calculated asFIG. 2 Reaction Vial (30 mL) with TFE-fluorocarbon Cov

44、er and Temperature ProbeD6703074functions of the quantities Cminand FRmax, the values of whichare obtained from three experimental variables, the weight ofresiduum or asphalt (Wa), the volume of solvent (VS), and thevolume of titrant added up to the flocculation point (VT).6. Apparatus6.1 UV-visible

45、 Spectrophotometer, wavelength scanningrange from 200 to 1000 nm, with adjustable aperture orattenuator.6.2 Digital Integrator, or data acquisition system (com-puter). One-millisecond data sampling rate.6.3 Water-Jacketed Reaction Vessel, 200-mL, two.6.4 TFE-fluorocarbon Covers, two.6.4.1 TFE-fluoro

46、carbon Cover No. 1, (see Fig. 2), threadedto hold a 30-mL reaction vial. Dimensions: thickness, 2.0 mm(916 in.); diameter, 70 mm (234 in.), threaded to 30-mL reactionvial. Three holes, 1.5 mm (116 in.) in diameter, concentric tothe covers center, are arranged in a triangle, are tapped to setwithin t

47、he inside diameter of the vial when attached to theTFE-fluorocarbon cover, with a distance between holesroughly equal to 10 mm (38 in.). One additional hole, 3.0 mm(18 in.), is tapped off center, positioned just to the outside ofwhere the reaction vial is positioned in the TFE-fluorocarboncover. Thi

48、s hole allows the temperature probe to be insertedinto the water-filled reaction vessel.6.4.2 TFE-fluorocarbon Cover No. 2, as a lid for the second200-mL, water-jacketed reaction vessel, containing titrant.Dimensions: thickness, 2.0 mm (916 in.); diameter, 70 mm (234in.). One hole 1.5 mm (116 in.) i

49、n diameter tapped through thecovers center. This cover is identical to the cover described in6.4.1 except for the number of holes, and is not threaded.6.5 High Flow Rate Metering PumpPiston diameter, 3.0mm (18 in.); piston displacement 80-mm (3-in.), probe contact diameter, 3.0mm(18 in.).6.19 Graduated Cylinders, two. Volumes: 1.000 6 0.001mL and 10.0 6 0.1 mL.6.20 Argon Gas Supply.6.21 Laboratory JacksLaboratory jacks are used as standsfor the metering pumps previously listed. The size require-ments of these laboratory jacks will vary d