ASTM D6703-2001 Standard Test Method for Automated Heithaus Titrimetry《自动HEITHAUS滴定分析法的标准试验方法》.pdf

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1、Designation: D 6703 01Standard 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 that estimate thecolloidal stability of asphalts and aspha

3、lt cross blends (1,2)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 user of

4、this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 asphalt (5), na dark brown to black cementitiousmaterial, solid or semisolid in consisten

5、cy, in which thepredominating constituents are bitumens, which occur in na-ture as such or are obtained as residue by refining petroleum.2.1.2 asphalt cross-blend, nany mixture of two or moreasphalts blended together to form a consistent material.2.1.3 asphaltene peptizability, nthe tendency of asph

6、alt-enes to exist as a stable dispersion in a maltene solvent,measured by the Heithaus parameter pa.2.1.4 asphaltenes, nthe high molecular weight hydrocar-bon fraction precipitated from asphalt by a designated paraf-finic naphtha solvent at a specified solvent-asphalt ratio.2.1.4.1 DiscussionThe asp

7、haltene fraction should beidentified by the solvent and solvent-asphalt ratio used.2.1.5 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 system.2.1.6 bitumen,

8、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.2.1.7 coke, nthe solid product resulting from the destruc-tive dist

9、illation of coal, petroleum residuum, or bitumen in anoven or closed chamber, or from imperfect combustion of thesematerials, consisting principally of carbon.2.1.8 colloidal suspension, nan intimate mixture of twosubstances, one of which, called the dispersed phase (orcolloid), is uniformly distrib

10、uted in a finely divided statethrough the second substance, called the dispersion medium (ordispersing medium).2.1.9 compatibility, nthe state of peptization of an as-phalt, which is measured quantitatively by the Heithaus param-eter P.2.1.10 core asphalts, nthe eight asphalts selected forintensive

11、study in the Strategic Highway Research Program(SHRP).2.1.11 dispersed phase, none phase of a dispersion con-sisting of particles or droplets of one substance distributedthrough a second phase.2.1.12 dispersing medium, none phase of a dispersion thatdistributes particles or droplets of another subst

12、ance, thedisperse phase.2.1.13 flocculation, nthe process of aggregation and coa-lescence into a flocculent mass.2.1.14 Heithaus compatibility parameters, nthree param-eters: asphaltene peptizability (pa), maltene peptizing power(po), and asphalt state of peptization (P), measured usingHeithaus titr

13、ation methods.2.1.15 maltene peptizing power, nthe ability of a maltenesolvent to disperse asphaltenes, measured by the Heithausparameter po.2.1.16 maltenes, na red-brown to black heavy oil materialderived from asphalt after precipitation with normal orbranched alkanes (for example, n-pentane, n-hex

14、ane,n-heptane, isooctane, and so forth), filtration of asphaltenes,and distillation of alkane precipitating agent from the filtrate.Equivalent to deasphaltened materials. Maltenes are the sol-vent moiety of an asphalt.2.1.17 oxidatively age-hardened asphalt, nan asphalt thathas reacted with oxygen a

15、t elevated temperatures in an oven,usually under greater than atmospheric oxygen pressure. Thereaction is run for a time sufficient to simulate asphalt aging inpavement.2.1.18 pyrolysis, nthe breaking apart of complex mol-ecules into simpler units by the use of heat, as in the pyrolysisof heavy oil

16、to make gasoline.2.1.19 residuum, na quantity or body of matter remaining1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.47 onMiscellaneous Asphalt Tests.Current edition approved Aug. 10, 2001. Publish

17、ed October 2001.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.after evaporation, combustion, or distillation.3. Summary of Test Method3.1 Three 30-mL reaction via

18、ls 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 (2.000 mL) is added to each of the reaction vials todissolve the asphalt (or hea

19、vy oil residuum). Thus, eachreaction vial contains a solution of different concentration ofasphalt (or heavy oil residuum) in toluene. Each of thesesolutions then is titrated with isooctane (2,2,4-trimethyl pen-tane) or some other titrant (6) at a constant titrant delivery rate.The titration is perf

20、ormed by installing the reaction vialsseparately in the apparatus illustrated in Fig. 1. Basically, thisapparatus consists of intersecting sample circulation and titra-tion loops.3.2 Each reaction vial is housed in a 200-mL, water-jacketed reaction vessel (Fig. 1). Water-jacketing is requiredbecause

21、 careful temperature control of the system is essential.The reaction vessel is filled with enough water such that thereaction vial and temperature probe are immersed. Waterflowing through the water jacket maintains the temperature ofthe water in the reaction vessel, which maintains the tempera-ture

22、of the solution in the reaction vial. The connection with thesample circulation loop is made by covering the reaction vialwith a screw top TFE-fluorocarbon cover penetrated by threesmall bore TFE-fluorocarbon tubes (Fig. 2). A fourth hole inthe cover accommodates a temperature probe. One of thesetub

23、es (1.6-mm (116-in. diameter) leads to a short path length(0.1-mm) quartz cell housed in a ultraviolet- (UV) visiblespectrophotometer. A second tube (1.6-mm diameter) leads toa high flow rate metering pump and then to the quartz cell. Thissystem is the sample circulation loop. The third tube (1.6-mm

24、diameter) connects the reaction vial to the titration loop andleads to a low flow rate metering pump and then to anotherwater-jacketed reaction vessel filled with titrant (usually iso-octane). This reaction vessel is covered with another TFE-fluorocarbon cover penetrated by one TFE-fluorocarbon tube

25、.This TFE-fluorocarbon cover has the same dimensions as theone illustrated in Fig. 2, but does not require threading becausethe cover fits directly over the reaction vessel and no vial isscrewed into it. Also it has only one hole. The second reactionvessel is filled with titrant. While the sample so

26、lution circulatesthrough the sample circulation loop, the titrant is pumped intothe sample reaction vial at a constant rate using the low flowrate metering pump. During this process, the output signal fromthe spectrophotometer is recorded using an integrator or someother data gathering device. The c

27、hange in percent transmit-tance (%T) of detected radiation at 740 nm (7) passing throughthe quartz cell is plotted versus the time, t, during which thetitrant is added to the sample reaction vial.3.3 The spectrophotometer output signal detects the onset ofturbidity of the sample solution. This is th

28、e flocculation onsetpoint, corresponding to the beginning of the precipitation ofasphaltenes from 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

29、 %T decrease. The reason thatthe curves in Fig. 3 exhibit maxima is that, at the beginning ofeach 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 req

30、uired to reach the maximum in %T fromthe onset of titration of a sample is defined as the flocculationtime, 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.3.4 The weight of

31、each asphalt (or heavy oil residuum)sample, Wa, the volume of toluene used to dissolve eachsample, 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

32、 solutions are used to calculate thequantities C (referred to as the dilution concentration) and 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

33、). Customarily, the C values are along thex-axis, and the FR values are the y-axis. The three data 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

34、 as FRmax. These two values are used to calculate thethree Heithaus compatibility parameters, designated 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

35、. The parameter P, the overall compatibility of the system, isdefined as po/(1 pa), or (1/Cmin+ 1).4. Significance and Use4.1 This test method is intended primarily as a laboratorydiagnostic tool for estimating the colloidal stability of asphalt,asphalt cross blends, aged asphalt, pyrolyzed asphalt,

36、 andheavy oil residuum. Historically, asphalt and heavy oil residuahave been modeled as colloidal suspensions (8,9) in which apolar, associated asphaltene moiety (the dispersed phase) issuspended in a maltene solvent moiety (the dispersing me-dium). The extent to which these two moieties remain in a

37、given state of peptization is a measure of the compatibility ofthe suspension. Compatibility influences important physicalproperties of these materials, including rheological properties,for example, phase angle and viscosity (10,11). Compatibilityalso influences coke formation in refining processes

38、(4). Thistest method and other similar test methods (7, 12-15), alongwith the classical Heithaus test (1,2), measures the overallcompatibility of a colloidal system by determining a designatedparameter referred to as the state of peptization, P. The valueof P commonly varies between 2.5 and 10 for u

39、nmodified orneat asphalts. 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 designatedparameters that relate to the peptizability of the

40、 asphaltenemoiety (the asphaltene peptizability parameter, pa) and thesolvent power of the maltene moiety (the maltene peptizingpower parameter, po). Values of paand poare calculated asD 67032FIG.1AutomatedTitrationApparatusD 67033functions of the quantities Cminand FRmax, the values of whichare obt

41、ained 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).5. Apparatus5.1 UV-visible Spectrophotometer, wavelength scanningrange from 200 to 1000 nm, with adjustable aperture orattenuat

42、or.5.2 Digital Integrator, or data acquisition system (com-puter). One-millisecond data sampling rate.5.3 Water-Jacketed Reaction Vessel, 200-mL, two.5.4 TFE-fluorocarbon Covers, two.5.4.1 TFE-fluorocarbon Cover No. 1, (see Fig. 2), threadedto hold a 30-mL reaction vial. Dimensions: thickness, 2.0 m

43、m(916in.); 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 the inside diameter of the vial when attached to theTFE-fluorocarbon cover, with a distance between hol

44、esroughly equal to 10 mm (38 in.). One additional hole, 3.0 mmFIG. 2 Reaction Vial (30 mL) with TFE-fluorocarbon Cover and Temperature ProbeD 67034(18 in.), is tapped off center, positioned just to the outside ofwhere the reaction vial is positioned in the TFE-fluorocarboncover. This hole allows the

45、 temperature probe to be insertedinto the water-filled reaction vessel.5.4.2 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.) in diameter tapped

46、 through thecovers center. This cover is identical to the cover described in5.4.1 except for the number of holes, and is not threaded.5.5 High Flow Rate Metering PumpPiston diameter, 3.0mm (18 in.); piston displacement 80-mm (3-in.), probe contact diameter, 3.0mm(18in.).5.19 Graduated Cylinders, two

47、. Volumes: 1.000 6 0.001mL and 10.0 6 0.1 mL.5.20 Argon Gas Supply.5.21 Laboratory JacksLaboratory jacks are used as standsfor the metering pumps previously listed. The size require-ments of these laboratory jacks will vary depending on the sizeto the metering pumps.5.22 Beakers, two. Volume: 500 mL

48、.5.23 Polypropylene Squirt Bottles, two. Volume: 200 mL.5.24 TFE-fluorocarbon Lined Caps, for closing reactionvials and storing solutions.6. Reagents and Materials6.1 Purity of ReagentsHPLC grade chemicals shall beused in all sample preparations and tests. Unless otherwiseindicated, it is intended t

49、hat all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society where such specifications areavailable4. Other grades may be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.6.2 isooctane (2,2,4-trimethylpentane), HPLC grade.6.3 Toluene, HPLC grade.6.4 Toluene, reagent grade, for cleaning.7. Assembly7.1 Installation Requirements:7.1.1 It is recommended that the following assembly becon