1、Designation: D4284 12Standard Test Method forDetermining Pore Volume Distribution of Catalysts andCatalyst Carriers by Mercury Intrusion Porosimetry1This standard is issued under the fixed designation D4284; the number immediately following the designation indicates the year oforiginal adoption or,
2、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. Scope1.1 This test method covers the determination of the porevolume distributions of cata
3、lysts and catalyst carriers by themethod of mercury intrusion porosimetry. The range of appar-ent diameters of pores for which it is applicable is fixed by theoperant pressure range of the testing instrument. This range istypically between apparent pore entrance diameters of about100 and 0.003 m (3
4、nm).1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 WARNINGMercury has been designated by manyregulatory agencies as a hazardous material that can causecentral nervous system, kidney and liver damage. Mercury, orits vapo
5、r, may be hazardous to health and corrosive tomaterials. Caution should be taken when handling mercury andmercury containing products. See the applicable product Ma-terial Safety Data Sheet (MSDS) for details and EPAswebsitehttp:/www.epa.gov/mercury/faq.htmfor addi-tional information. Users should b
6、e aware that selling mercuryand/or mercury containing products into your state or countrymay be prohibited by law.1.4 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate s
7、afety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardinformation is given in Section 8.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Qualit
8、y and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 apparent pore diameterthe diameter of a pore,assumed to be cylindrical, that is intruded at a pressure, P, andis calc
9、ulated with Eq 1.3.1.2 interparticle poresthose pores that occur betweenparticles when they are packed together and that are intrudedduring the test.3.1.3 intraparticle poresthose pores lying within the en-velopes of the individual catalyst particles and that are intrudedduring the test.3.1.4 intrud
10、ed pore volumethe volume of mercury that isintruding into the pores during the test after this volume hasbeen corrected, if necessary, per 13.3.2.4. Summary of Test Method4.1 When a liquid does not wet a porous solid it will notvoluntarily enter the pores in the solid by capillary attraction.The non
11、wetting liquid (mercury in this test method) must beforced into the pores by the application of external pressure.The size of the pores that are intruded is inversely proportionalto the applied pressure. When a cylindrical pore model isassumed, the relationship between pressure and size is:d 524gcos
12、u!P(1)where:d = apparent diameter of the pore being intruded,g = surface tension of the mercury,u = contact angle between the mercury and the solid, andP = absolute pressure causing the intrusion.4.2 The volume of the intruded pores is determined bymeasuring the volume of mercury that is forced into
13、 them atvarious pressures.Asingle-pore size distribution determinationinvolves increasing the pressure, either continuously or step-wise, and recording the measured intruded volume.1This test method is under the jurisdiction of ASTM Committee D32 onCatalysts and is the direct responsibility of Subco
14、mmittee D32.01 on Physical-Chemical Properties.Current edition approved May 1, 2012. Published July 2012. Originally approvedin 1983. Last previous edition approved in 2007 as D428407. DOI: 10.1520/D4284-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
15、 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 Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 This test me
16、thod is intended to determine the volumedistribution of pores in catalysts and catalyst carriers withrespect to the apparent diameter of the entrances to the pores.In general, both the size and volume of pores in a catalyst affectits performance. Thus, the pore volume distribution is useful inunders
17、tanding a catalysts performance and in specifying acatalyst that can be expected to perform in a desired manner.6. Limitations6.1 Mercury intrusion porosimetry, in common with manyother test methods, is only capable of sensing pores that areopen to the outside of a catalyst or catalyst carrier parti
18、cle, andwill not determine the volume of any pores that are completelyenclosed by surrounding solid. Also, the test method will onlydetermine the volume of intrudable pores that have an apparentdiameter corresponding to a pressure within the pressuringrange of the testing instrument.6.2 The intrusio
19、n process proceeds from the outside of aparticle toward its center. Comparatively large, interior porescan exist that have smaller pores as the only means of access.The test method will incorrectly register the entire volume ofthese “ink-bottle” pores as having the apparent diameter of thesmaller ac
20、cess pores.6.3 In the penetrometer, interparticle pores can be created inaddition to the intraparticle pores. (See Section 3 for terminol-ogy.) These interparticle pores will vary in size and volumedepending on the size and shape of the catalyst particles and onthe manner in which the particles are
21、packed together in the testchamber. It is possible that some of the interparticle pores willhave the same apparent diameter as some of the intraparticlepores. When this occurs, the test method cannot distinguishbetween them. Thus, the test method can yield an intruded porevolume distribution that is
22、 in part, dependent upon the packingof multi-particle samples. However, many catalysts have intra-particle pores that are much smaller than the interparticlepores. This situation leads to a bimodal pore size distributionand the distinction between the two classes of pores canfrequently be made.6.4
23、Mercury intrusion can involve the application of highpressures on the sample. This may result in a temporary, orpermanent, alteration in the pore geometry. Generally, catalystsand catalyst carriers are made from comparatively strong solidsand are less subject to these alterations than some othermate
24、rials. However, the possibility remains that the use of thetest method may alter the natural pore volume distribution thatit seeks to measure.7. Apparatus7.1 Mercury Intrusion Porosimeter, equipped with a sampleholder capable of containing one or several catalyst or catalystcarrier particles. This h
25、older is frequently called a penetrom-eter. The porosimeter shall have a means of surrounding thetest specimen with mercury at a low pressure, a pressuregenerator to cause intrusion, pressure transducers capable ofmeasuring the intruding pressure with an accuracy of at least61 % throughout the range
26、 of pressures over which the poresof interest are being intruded, and a means of measuring theintruded mercury volumes with an accuracy of at least 61mm3(6103cm3).7.2 Vacuum Pump, if not part of the porosimeter, to evacuatethe sample holder.7.3 Analytical Balance capable of measuring the samplesmass
27、 with an accuracy of at least 60.1 %. This usually meansthat the balance must be sensitive to 6107kg (60.1 mg).7.4 Mercury, with a purity equal to, or better than, doubledistilled.8. Hazards8.1 Samples that have been exposed to mercury are danger-ous. Apply the precautions that follow:8.1.1 Mercury
28、is a hazardous substance that can causeillness and death. Mercury can also be absorbed through theskin; avoid direct contact.8.1.2 Always store in closed containers to control its evapo-ration, and use it only in well-ventilated rooms.8.1.3 Wash hands immediately after any operation involvingmercury
29、8.1.4 Exercise extreme care to avoid spilling mercury. Cleanup any spills immediately using procedures recommendedexplicitly for mercury.8.1.5 Recycling of waste mercury is recommended and to beconducted in accordance with local government hazardouswaste regulations. Disposal of waste mercury and m
30、ercurycontaminated materials should be performed as mandated bylocal government hazardous waste regulations.9. Sampling9.1 The sample from which test material will be drawn shallbe representative of the catalyst or the catalyst carrier. Theactual amount of sample used in a test will depend on thesen
31、sitivity of the porosimeter and the porosity of the sample.10. Conditioning10.1 The ideal preconditioning for the test specimen is anoutgassing procedure that removes all foreign substances fromthe pores and pore walls of the catalyst, but does not alter thesolid catalyst in any way. If possible, th
32、e appropriate combi-nation of heat and vacuum and the required time of condition-ing shall be experimentally determined for the specific catalystor catalyst carrier under test. This outgassing technique shallthen be the one specified and used.10.2 Where the procedure described in 10.1 is not practic
33、al,outgas the sample in a vacuum of at least 1.3 Pa (10 mHg) ata temperature of 150C for at least 8 h.NOTE 1The procedure in 10.2 is unlikely to alter the pore structure ofa catalyst but it can severely change the pore structure of many othermaterials.11. Procedure11.1 Outgas the test sample in acco
34、rdance with 10.1 or 10.2.11.2 Weigh the outgassed specimen and record this weight.11.3 Place the outgassed catalyst in the penetrometer inaccordance with the manufacturers instructions.NOTE 2Since, when performing the operations described in 11.2 andD4284 12211.3, the outgassed catalyst is exposed t
35、o the laboratory atmosphere andcan readsorb vapors, carry these operations out as rapidly as possible.11.4 Place the penetrometer containing the sample in theappropriate chamber of the porosimeter, following the manu-facturers instructions, and evacuate to a pressure of at least1.3 Pa (10 m Hg).11.5
36、 Fill the penetrometer with mercury, in accordance withthe manufacturers instructions, by pressuring to some suitablylow pressure.NOTE 3The pressure required to fill the penetrometer with mercury isalso capable of filling sufficiently large pores of both the inter- andintra-particle classes. Thus, t
37、he filling process can fill some pores withmercury and the volume distribution of these pores cannot subsequentlybe determined. This fact should be recognized and, where possible, selecta filling pressure that will not intrude pores in the diameter range ofsubsequent interest.11.6 Place the filled p
38、enetrometer in the pressure vessel ofthe porosimeter and prepare the instrument for pressurizationand intrusion readings in accordance with the manufacturersinstructions.11.7 Raise the pressure, either continuously or step-wise,and record both the absolute pressure and the volume ofintruded mercury
39、until the maximum pressure of interest isreached.NOTE 4When raising the pressure incrementally, minimize the pres-sure drop during the pause. Certain modern instruments allow for anautomatic repressurization to the target pressure when the pressuredecreases. When samples with relatively narrow pore
40、size distribution areanalyzed, the extent of depressurization and repressurization may affecttest method precision and the measured pore volume.NOTE 5When testing some materials, the time required to achieveintrusion equilibrium will not be the same at all pressures. Often, theequilibrium time is ap
41、preciably longer at pressures that cause an abruptand large increase in intruded volume. Failure to record the equilibriumintrusion will result in some of the pore volume being incorrectly ascribedto smaller pore diameters. Assess the extent to which this may be aproblem by conducting two tests, eac
42、h at a different pressuring rate, andcompare the results. Measure recorded intrusion values at, essentially,equilibrium.NOTE 6Use of Eq 1 requires the absolute pressure, P. With someinstruments, it may not be possible to read the absolute pressure directly.In this case, record the gage pressure and
43、calculate the absolute pressuressubsequently.NOTE 7If incremental pressure steps are used, the choice of pressureintervals at which data are to be recorded will be specified by thosedirecting the test or, left to the judgement of the operator. A minimum of10 to 15 data points will be required to def
44、ine the pore volumedistribution. Frequently, 25 or more points are found to be helpful. Inselecting these pressure points, a rough idea of the expected distribution ishelpful, since the pressure intervals can be larger in regions where little orno intrusion occurs. The intervals should be smaller in
45、 regions where alarge volume of intrusion occurs abruptly.NOTE 8It is not necessary to continue the process up to the maximumpressuring capability of the instrument if all of the pores of interest in aparticular test have been intruded at a lesser pressure.11.8 Upon completion of the pressuring cycl
46、e, reduce thepressure and disassemble and clean the instrument in accor-dance with the manufacturers instructions.12. Blank Test for Corrections12.1 An intrusion test on a nonporous sample may berequired to obtain values to use in correcting intrusion data forcompressibilities and temperature change
47、s.12.2 Select a nonporous material for this test that hasapproximately the same compressibility and bulk volume asthe catalyst or catalyst carrier sample that is to be tested.12.3 Test the nonporous sample in exactly the same manneras outlined in Section 11. Raise the pressure in the samemanner as u
48、sed for the catalyst tests to ensure that temperaturechanges due to pressuring are the same.12.4 The results of this blank test are a series of measuredvolume changes that can also be expected to occur, along withactual pore intrusion, during a test on a catalyst or catalystcarrier. They are used to
49、 correct the intruded volumes asdiscussed in 13.3.2.12.5 The compressibilities of the various components in thesystem augment the measured intrusion values while thepressure-induced heating and consequent expansion of thesystem reduces the measured volumes. In a particular instru-ment, either one of these effects may be dominant. Hence, theresults of the blank test may be either an apparent intrusion(compressibility dominant) or an expulsion of mercury (heat-ing dominant).12.5.1 If the blank results show apparent intrusion, they areto be subtracted from
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