1、Designation: D 4567 03 (Reapproved 2008)Standard Test Method forSingle-Point Determination of Specific Surface Area ofCatalysts and Catalyst Carriers Using Nitrogen Adsorptionby Continuous Flow Method1This standard is issued under the fixed designation D 4567; the number immediately following the de
2、signation 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the
3、 single-point determinationof the surface area of catalysts and catalyst carriers that exhibitType II or Type IV nitrogen adsorption isotherms using anitrogen-helium flowing gas mixture. This test method isapplicable for the determination of total surface areas from 0.1to 300 m2, where rapid surface
4、 area determinations are desired.1.2 Because the single-point method uses an approximationof the BET equation, the multipoint BET method (Test MethodD 3663) is preferred to the single-point method.NOTE 1This is particularly true when testing microporous materials.1.3 The values stated in SI units ar
5、e to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of whoever uses this standard to consult andestablish appropriate safety and healt
6、h practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 3663 Test Method for Surface Area of Catalysts andCatalyst CarriersD 3766 Terminology Relating to Catalysts and CatalysisE 177 Practice for Use of the Terms Precision and
7、Bias inASTM Test MethodsE 456 Terminology Relating to Quality and StatisticsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsSee Terminology D 3766.3.2 Symbols:Acs= cross-sectional area of nitrogen, 16.2 3 1020m2.CI= integr
8、ator counts.CITa = integrator counts corrected for ambient tempera-ture.CIPa = integrator counts corrected for ambient pressure.N = Avogadros number, 6.02 3 1023, molecules/mole.P = partial pressure of nitrogen, torr.Pa= ambient pressure, torr.Po= saturated equilibrium vapor pressure of liquid ni-tr
9、ogen, torr.R = gas constant, 82.1 cm3atm/K mole.Ta= ambient temperature, K.V = volume of nitrogen adsorbed at ambient tempera-ture and pressure, cm3.W1= tare of sample cell, g.W2= sample mass + tare of sample cell after analysis, g.Ws= mass of sample, g.4. Summary of Test Method4.1 The sample is deg
10、assed by heating in a flow of inert gasto remove adsorbed vapors from the surface. The sample isthen immersed in a liquid nitrogen bath causing adsorption ofnitrogen from a flowing mixture of a fixed concentration ofnitrogen in helium. When adsorption is complete, the sample isallowed to warm to roo
11、m temperature causing desorption,which results in an increase in the nitrogen concentration in the1This test method is under the jurisdiction of Committee D32 on Catalysts andis the direct responsibility of Subcommittee D32.01 on Physical-Chemical Proper-ties.Current edition approved April 1, 2008.
12、Published April 2008. Originallyapproved in 1986. Last previous edition approved in 2003 as D 456703.2For referenced ASTM standards, 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 D
13、ocument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.flowing mixture. The quantity of nitrogen gas desorbed isdetermined by sensing the change in thermal conductivity.4.2 Calculation of the surface
14、area is based on a modifiedform of the BET equation.5. Significance and Use5.1 This test method is useful for determining the specificsurface area of catalysts and catalyst carriers for materialspecifications, manufacturing control, and research and devel-opment in the evaluation of catalysts.6. App
15、aratus6.1 Aschematic diagram of the apparatus is shown in Fig. 1.The apparatus may be constructed of glass or metal tubing. Ithas the following features:6.1.1 Differential Flow Controller from the gas inlet valveto a flow control valve to eliminate fluctuations in the gas flow.6.1.2 Two Thermal Cond
16、uctivity DetectorsA referencedetector (A) to sense the nitrogen-helium gas mixture and asecond detector (B) to sense changes in the gas mixture afterflowing through the sample cell. The two detectors are initiallybalanced to allow the detection of changes in the nitrogenconcentration.6.1.3 Flow-Thro
17、ugh Sample Cells, of various volumes andshapes depending on the application.6.1.4 Two Equilibration Tubes selected by a selector valve,between the sample cell and detector (B). The small volumetube has a volume of approximately 20 cm3and the largevolume tube has a 100 cm3capacity to allow for temper
18、atureand pressure equilibration of a wide range of volumes of gases.6.1.5 Flow Meter, to monitor the flow rate of the nitrogen-helium mixture maintained at approximately 20 cm3/min.6.1.6 Diffusion Baffle, to prevent air from diffusing back intothe system during cooling of the sample.6.1.7 Bridge Bal
19、ance Meter, to display balance or imbal-ance between detectors A and B.6.1.8 Digital Integrator, to measure the imbalance betweendetectors A and B and display the surface area of the sample.6.1.9 Septum or Fixed Loop, for injection of calibration gas.6.1.10 Degassing Station, for removal of adsorbed
20、 vaporsfrom the sample.6.1.11 Cold Trap, for removal of impurities in the gasmixture.6.1.12 Thermal Equilibration Tube, to allow the flowing gasmixture to reach temperature and pressure equilibration beforereaching detector (A).6.2 Heating Mantle.6.3 Dewar Flasks.6.4 Laboratory Balance with 0.1 mg (
21、107kg) sensitivity.6.5 Gas-Tight Syringe or Gas Sampling Loop, 1.00 cm3.7. Reagents7.1 Liquid Nitrogen, of such purity that the saturated equi-librium vapor pressure is not more than 20 torr above ambientpressure.7.2 Cylinder, with pressure regulator, of high purity 30mole % nitrogen in helium equiv
22、alent to a relative pressure ofapproximately 0.3, where the nitrogen concentration is knownto within 0.1 mole %. Concentrations lower than 30 mole %should be used for materials containing micropores, for ex-ample, zeolites.8. Calibration of the Apparatus8.1 If the gas mixture contains impurities, pl
23、ace a Dewarflask containing liquid nitrogen around the cold trap.8.2 Using a gas-tight syringe inject 1.00 cm3(or some otherknown volume) of air or nitrogen into the calibration septum.The digital integrator should display 2.84 6 0.03 counts (see11.3) for a 1.00-cm3injection (or a proportional numbe
24、r ofcounts for a different volume). If the counts are greater than2.84, increase the gas flow through the flow control valve. Ifthe counts are less than 2.84, decrease the gas flow and retest.FIG. 1 ApparatusD 4567 03 (2008)29. Preparation of Sample9.1 Weigh to 0.0001 g a clean, dry empty sample cel
25、l.Record the mass, W1.9.2 Place the catalyst sample into the sample cell. Choosethe sample size to provide an estimated surface area of 0.1 to300 m2.9.3 Attach the sample cell to the degassing station.9.4 Attach an empty cell to the sample station.9.5 Open the gas inlet valve and adjust the flow con
26、trolvalve to allow a gas flow of approximately 20 cm3/min.Observe the reading on the flow meter.9.6 Install a heating mantle around the sample cell and raisethe temperature to 300C (573 K).NOTE 2Certain materials will decompose at 300C (for example,alumina hydrates) or will sinter (for example, plat
27、inum black). Lowerdegassing temperatures are permitted for such materials. However, thedegassing temperature should be specified when reporting the results.9.7 Continue degassing at about 300C (573 K) for aminimum of 1 h. Overnight degassing is permissible. If lowertemperatures are used for degassin
28、g, longer times may berequired.9.8 Remove the heating mantle and allow the sample tocool.9.9 Remove the sample cell from the degassing station,protecting the sample from exposure to atmospheric contami-nants.9.10 Remove the empty cell from the sample station.10. Surface Area Determination10.1 Attach
29、 the sample cell to the sample station.10.2 Allow any air to be purged from the system by theflowing gas mixture. This condition can be ascertained byobserving that the bridge balance meter indicates a balance.10.3 To initiate adsorption, place a Dewar flask of liquidnitrogen around the sample cell
30、so that the liquid level isapproximately 2 to 3 cm from the top of the cell.10.4 When adsorption is complete, as indicated by thebridge balance meter and digital integrator, remove the Dewarflask.10.5 Clear the digital integrator.10.6 Immerse the sample cell in a beaker of room tempera-ture water un
31、til the gas flow returns to its original rate asindicated by the flow meter.NOTE 3If the flow meter does not return to its original value, obtainedbefore the digital integrator starts to count, either remove some of thesample or use the large volume equilibration tube (see Fig. 1) and repeatsteps 10
32、.2-10.6.10.7 When the counter stops counting, record the counterreading.10.8 Remove the sample cell from the sample station, drythoroughly and weigh. Record the mass, W2.11. Calculations11.1 Calculate the total surface area of the sample from amodified form of the BET equation as follows:Total surfa
33、ce area 5 PaVNAcs!/RTa!1 2 P/Po! (1)11.2 Using 30 mole % nitrogen as the adsorbate in helium atan ambient temperature of 22C (295 K) and a pressure of 1.0atm (760 torr) and assuming that Pois 775 torr,Total surface area 5 2.84 V (2)11.3 Thus, 2.84 m2of surface area corresponds to 1.00cm3of nitrogen
34、adsorbed.11.4 Calculate the mass of sample as follows:WS5 W22 W1(3)11.5 For ambient temperatures other than 295 K, multiplythe integrator counts (CI) by 295/Ta.CiTa 5 CI3 295/Ta (4)11.6 For ambient pressures other than 760 torr, multiply theintegrator counts (CI)byPa/760.CIPa 5 CI3 Pa/760 (5)11.7 Fo
35、r gas concentrations other than 30 mole %, multiplythe integrator counts by (1 P/Po)/0.706. The partial pressureP of the gas is the product of the mole fraction and ambientpressure. Pois assumed to be ambient pressure plus 15 torr.11.8 Calculate the specific surface area as follows:Specific surface
36、area 5 CI/WS(6)or if the corrections in 11.5, 11.6,or11.7, or combinationthereof, have been used:Specific surface area 5CIWS3295Ta3Pa76031 2 P/Po0.706(7)12. Presentation of Data12.1 Report the specific surface area in square metres pergram to three significant figures.13. Precision and Bias313.1 Tes
37、t ProgramAn interlaboratory study was con-ducted in which the named property was measured in threeseparate test materials in 22 separate laboratories. PracticeE 691, modified for nonuniform data sets, was followed for thedata reduction. Analysis details are in the research report.13.2 PrecisionPairs
38、 of test results obtained by a proce-dure similar to that described in the study are expected to differin absolute value by less than 2.772 S, where 2.772 S is the95 % probability limit on the difference between two testresults see Table 1, and S is the appropriate estimate ofstandard deviation. Def
39、initions and usage are given in Termi-nology E 456 and Practice E 177, respectively.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D32-1019.TABLE 1 Repeatability and ReproducibilityTest Result(Consensus),m2/g95% Repeatability
40、Limit(Within Laboratory),m2/g, (%)95% Reproducibility Limit(Between Laboratories),m2/g, (%)10.33 0.17 (1.7) 1.82 (17.6)153.2 2.66 (1.7) 22.24 (14.5)277.6 4.49 (1.6) 46.61 (16.8)D 4567 03 (2008)313.3 BiasThe test method described is without knownbias. Results from this single-point method are statist
41、icallycomparable to those of the multipoint method based on threesamples ranging in specific surface areas from 10 to 280 m2/g.NOTE 4No microporous materials were tested in the interlaboratorystudy supporting this test method. Microporous materials may producedifferent results.14. Keywords14.1 adsor
42、ption; catalyst carriers; catalysts; continuousflow; surface areaASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any su
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45、 fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4567 03 (2008)4
