ASTM D4567-2003(2013) Standard Test Method for Single-Point Determination of Specific Surface Area of Catalysts and Catalyst Carriers Using Nitrogen Adsorption by Continuous Flow M.pdf

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1、Designation: D4567 03 (Reapproved 2013)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 D4567; the number immediately following the desi

2、gnation 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. Scope1.1 This test method covers the si

3、ngle-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 ar

4、ea determinations are desired.1.2 Because the single-point method uses an approximationof the BET equation, the multipoint BET method (Test MethodD3663) is preferred to the single-point method.NOTE 1This is particularly true when testing microporous materials.1.3 The values stated in SI units are to

5、 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 health pr

6、actices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3663 Test Method for Surface Area of Catalysts andCatalyst CarriersD3766 Terminology Relating to Catalysts and CatalysisE177 Practice for Use of the Terms Precision and Bias in

7、ASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsSee Terminology D3766.3.2 Symbols:Acs= cross-sectional area of nitrogen, 16.2 1020m2.CI= integrator counts.

8、CITa = integrator counts corrected for ambient temperature.CIPa = integrator counts corrected for ambient pressure.N = Avogadros number, 6.02 1023, molecules/mole.P = partial pressure of nitrogen, torr.Pa= ambient pressure, torr.Po= saturated equilibrium vapor pressure of liquidnitrogen, torr.R = ga

9、s constant, 82.1 cm3atm/K mole.Ta= ambient temperature, K.V = volume of nitrogen adsorbed at ambient temperatureand 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 degassed by heating in

10、 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 room temperature causi

11、ng desorption,which results in an increase in the nitrogen concentration in theflowing mixture. The quantity of nitrogen gas desorbed isdetermined by sensing the change in thermal conductivity.4.2 Calculation of the surface area is based on a modifiedform of the BET equation.5. Significance and Use5

12、.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.1This test method is under the jurisdiction of Committee D32 on Catalysts andis th

13、e direct responsibility of Subcommittee D32.01 on Physical-Chemical Proper-ties.Current edition approved April 1, 2013. Published August 2013. Originallyapproved in 1986. Last previous edition approved in 2008 as D4567 03(2008).DOI: 10.1520/D4567-03R13.2For referenced ASTM standards, visit the ASTM

14、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S

15、tates16. Apparatus6.1 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

16、Thermal Conductivity 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

17、.3 Flow-Through 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 allo

18、w for temperatureand 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.

19、7 Bridge Balance Meter, to display balance or imbalancebetween 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 o

20、f adsorbed 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 wit

21、h 0.1 mg (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 he

22、lium equivalent 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, forexample, zeolites.8. Calibration of the Apparatus8.1 If the gas mixture contains impuri

23、ties, place 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 proportion

24、al number 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.9. Preparation of Sample9.1 Weigh to 0.0001 g a clean, dry empty sample cell.Record the mass, W1.9.2

25、 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.FIG. 1 ApparatusD4567 03 (2013)29.5 Open the gas inlet valve and adjust the f

26、low controlvalve 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 exampl

27、e, platinum 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 d

28、egassing, 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

29、 Attach 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 sampl

30、e cell 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 w

31、ater until 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 repeats

32、teps 10.2-10.6.10.7 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:Tota

33、l surface 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 ni

34、trogen 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 CI3295/Ta (4)11.6 For ambient pressures other than 760 torr, multiply theintegrator counts (CI)byPa/760.CIPa 5 CI3Pa/760 (5)11

35、.7 For 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 sur

36、face 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.

37、1 Test ProgramAn interlaboratory study was con-ducted in which the named property was measured in threeseparate test materials in 22 separate laboratories. PracticeE691, modified for nonuniform data sets, was followed for thedata reduction. Analysis details are in the research report.13.2 PrecisionP

38、airs of test results obtained by a proceduresimilar to that described in the study are expected to differ inabsolute value by less than 2.772 S, where 2.772 S is the 95 %probability limit on the difference between two test results seeTable 1, and S is the appropriate estimate of standard deviation.D

39、efinitions and usage are given in Terminology E456 andPractice E177, respectively.13.3 BiasThe test method described is without knownbias. Results from this single-point method are statisticallycomparable to those of the multipoint method based on threesamples ranging in specific surface areas from

40、10 to 280 m2/g.NOTE 4No microporous materials were tested in the interlaboratorystudy supporting this test method. Microporous materials may producedifferent results.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D32-1019.TABLE

41、 1 Repeatability and ReproducibilityTest Result(Consensus),m2/g95% Repeatability 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)D4567 03 (2013)314. Keywords14.1 adsorptio

42、n; 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 such p

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