1、Designation: D 3663 03 (Reapproved 2008)Standard Test Method forSurface Area of Catalysts and Catalyst Carriers1This standard is issued under the fixed designation D 3663; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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 determination of surfaceareas of catalyst and catalyst carriers that have Type II or IVn
3、itrogen adsorption isotherms, and at least 1 m2/g of area. Avolumetric measuring system is used to obtain at least four datapoints which fit on the linear BET2line.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This st
4、andard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user 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
5、 ASTM Standards:3D 3766 Terminology Relating to Catalysts and CatalysisE 177 Practice for Use of the Terms Precision and 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. Ter
6、minology3.1 Consult Terminology D 3766 for definitions of otherterms used.3.2 Definitions:3.2.1 surface area of a catalystthe total surface of thecatalyst. It is expressed in square metres per gram.3.3 Symbols:PH1= initial helium pressure, torrPH2= helium pressure after equilibration, torrTH1= tempe
7、rature of manifold at initial helium pres-sure, CTH2= temperature of manifold after equilibration, CP1= initial N2pressure, torrT1= manifold temperature at initial N2pressure, KT18 = manifold temperature at initial N2pressure, CP2= pressure after equilibration, torrP0= liquid nitrogen vapor pressure
8、, torrTs= liquid nitrogen temperature, KX = relative pressure, P2/P0Vd= volume of manifold, cm3Vx= extra volume bulb, cm3Vs= dead-space volume, cm3Ws= mass of sample, gW1= tare mass of sample tube, gW2= sample + tare mass of tube, gVds= volume of nitrogen in the dead-space, cm3V1= see 10.4.4V2= see
9、10.4.6Vt= see 10.4.7Va= see 10.4.9Vm= see 10.8T1x= initial extra-volume bulb temperature, KT1x8(i) = initial extra-volume bulb temperature, CT2x= extra-volume bulb temperature after equilibrium,KT2x8(i) = extra-volume bulb temperature after equilibrium,C4. Summary of Test Method4.1 The surface area
10、of a catalyst or catalyst carrier isdetermined by measuring the volume of nitrogen gas adsorbedat various low-pressure levels by the catalyst sample. Pressuredifferentials caused by introducing the catalyst surface area toa fixed volume of nitrogen in the test apparatus are measuredand used to calcu
11、late BET surface area.5. Apparatus45.1 Aschematic diagram of the apparatus is shown in Fig. 1.It may be constructed of glass or of metal. It has the followingfeatures:5.1.1 Distribution Manifold, having a volume between 20and 35 cm3,(Vd), known to the nearest 0.05 cm3. This volume1This test method i
12、s under the jurisdiction of ASTM Committee D32 onCatalysts and is the direct responsibility of Subcommittee D32.01 on Physical-Chemical Properties.Current edition approved April 1, 2008. Published April 2008. Originallyapproved in 1978. Last previous edition approved in 2003 as D 366303.2Brunauer, E
13、mmett, Teller, Journal of American Chemical Society, JACS, No.60, 1938, p. 309.3For 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 Document Summary page o
14、nthe ASTM website.4Automated equipment is commercially available.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.is defined as the volume between the stopcocks or valves andincludes the pressure gage.5.1.2 Vacuum System, capable of a
15、ttaining pressures below104torr (1 torr = 133.3 Pa). This will include a vacuum gage(not shown in Fig. 1). Access to the distribution manifold isthrough the valve V.5.1.3 Constant-Volume Gage or Mercury Manometer, ca-pable of measurements to the nearest 0.1 torr, in the range from0 to 1000 torr (1 t
16、orr = 133.3 Pa).NOTE 1See, for example, the article by Joy5for a description of aconstant-volume manometer.5.1.4 Valve (H), from the helium supply to the distributionmanifold.5.1.5 Valve (N), from the nitrogen supply to the distributionmanifold.5.1.6 The connection between the sample tube and the Sv
17、alve can be a standard-taper glass joint, a glass-to-glass seal,or a compression fitting.5.1.7 Extra Volume Bulb,(Vx), should be 100 to 150 cm3,known to the nearest 0.05 cm3. Vxincludes the volume of thestopcock bore in the glass apparatus.5.2 Sample Tubes, with volumes from 5 to 100 cm3depend-ing o
18、n the application. Markings should be placed on thesample tubes about 30 to 50 mm below the connectors toindicate the desired liquid nitrogen level.5.3 Heating Mantles or Small Furnaces.5.4 Dewar Flasks.5.5 Laboratory Balance, with 0.1-mg (107-kg) sensitivity.5.6 Thermometer or Thermocouple, for mea
19、suring the tem-perature of the distribution manifold T18(i)orT28(i) indegrees Celsius.5.6.1 It is preferred that the manifold be thermostated at aparticular temperature, a few degrees above ambient, to obviatethe necessity of recording this temperature at each reading.5.7 Thermometer, for measuring
20、the temperature of theliquid nitrogen bath Ts(i) in kelvins. This will preferably be anitrogen vapor-pressure thermometer, often referred to in acommercial instrument as a pressure saturation tube, fromwhich P0values may be derived.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beuse
21、d in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.6Other grades may beused, provided it is first ascertained that the reagen
22、t is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Helium GasA cylinder of helium gas at least 99.9 %pure.6.3 Liquid Nitrogen, of such purity that P0is not more than20 torr above barometric pressure. A fresh daily supply isrecommended.6.4 Nitroge
23、n GasA cylinder of nitrogen gas at least99.999 % pure.7. ProcedureSample Preparation and Degassing7.1 Select a sample tube of the desired size.A5-cm3sampletube is preferred for samples not exceeding about 1 g, tominimize the dead-space. However, a 25-cm3sample tube maybe preferred for finely powdere
24、d catalysts, to avoid “boiling”when degassing is started.7.2 Fill the sample tube with nitrogen or helium, at atmo-spheric pressure, after removing air by evacuation.This may bedone on the surface area unit, or on a separate piece ofequipment.7.3 Remove the sample tube from the system, cap, andweigh
25、. Record the mass as W1.7.4 Place the catalyst sample, whose mass is known ap-proximately, into the sample tube. Choose the sample size toprovide an estimated total sample surface area of 20 to 100 m2.7.5 Attach the sample tube to the apparatus. If other samplesare to be run, attach them at this tim
26、e to the other ports.7.6 Open the S valves where there are samples.7.7 It may be necessary to close the V valve systemperiodically to protect the diffusion pump fluid from exposureto pressures above 0.1 torr for periods of more than 30 s. Closethe valve off for 2 min.7.8 Install a heating mantle or
27、furnace around each sampleand raise the temperature to about 300C (573 K).NOTE 2Take special precautions if the moisture content exceeds5Joy, A. S., Vacuum, Vol 3, 1953, p. 254.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on
28、the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Schematic Diagram of Surface Area
29、 ApparatusD 3663 03 (2008)2approximately 5 % to avoid “bumping” of powdered catalyst, and to avoidsurface area loss by self-steaming. It is recommended that the heating ratenot exceed 100 K/h under these circumstances.7.9 Continue degassing at about 300C (573 K) for aminimum of 3 h, at a pressure no
30、t to exceed 103torr.Overnight degassing is permissible.NOTE 3Certain materials will decompose at 300C (for example,alumina hydrates) or will sinter (for example, platinum black). Lowerdegassing temperatures are permissible for such materials; however, thedegassing temperature should be specified whe
31、n reporting the results.7.10 Remove the heating mantles, and allow the samples tocool.7.11 Close the EV valve, if open.7.12 Close the S valve.7.13 It is permissible to exercise the option of preliminarydegassing on an external unit. In such a case, follow theprocedures of 7.4-7.11 and then repeat on
32、 the surface area unit,except that the degassing time in 7.9 should not exceed 1 h.7.14 If it is desired to weigh the sample after preliminarydegassing on an external unit, backfill with the same gas usedin 7.2 to above atmospheric pressure. Close the S valve.7.15 Detach the sample tube from the app
33、aratus, recap withthe stopper used previously, and weigh. Record the mass as W2.7.16 Remove the backfilled gas by evacuation to less than104torr at room temperature.8. ProcedureDead-Space Determination8.1 From this point on, each sample being tested for surfacearea must be run on an individual basis
34、. Thus each Step8.2-9.17 must be carried out separately for each tube in test.8.2 The “dead-space” is the void volume of the chargedsample tube, including the S valve, when the tube is immersedin liquid nitrogen to the proper depth (see 5.2).NOTE 4The dead-space may be determined after the nitrogen
35、adsorp-tion, if more convenient, as long as adequate degassing precedes it. In thatcase, replace the liquid nitrogen bath after Step 9.14 before proceedingwith Steps 8.3-8.9.8.3 Place a Dewar flask of liquid nitrogen around the sampleand adjust the liquid level to a fixed point on the sample tube.Ma
36、intain this level throughout the test.8.4 Zero the pressure gage.8.5 Admit the helium gas into the manifold to a pressure of600 to 900 torr by carefully opening the H valve. Record thispressure as PH1, and the manifold temperature, TH1.8.6 Open the S valve to admit helium to the sample.8.7 After abo
37、ut 5 min of equilibration, readjust the liquidnitrogen level, and record the pressure as PH2, and manifoldtemperature as TH2.8.8 Repeat 8.5-8.7 for each sample on the manifold.8.9 Open all S valves; then slowly open the V valve toremove the helium gas.8.10 When a pressure less than 0.01 torr has bee
38、n attained,close the S valve. This operation should take 5 to 10 min.9. ProcedureNitrogen Adsorption9.1 Close the V valve and open the EVvalve if the extra-volume bulb is to be used, when the surface area is known tobe high.9.2 Recheck the zero setting of the pressure gage.9.3 Admit nitrogen gas, an
39、d record the pressure as P1(1)(torr) and the temperature as T18(1) (degrees Celsius) and readthe temperature of the extra-volume bulb and record it asT1x(1). It is desirable, but not necessary, to choose P1(1) suchthat the first equilibrium adsorption pressure, P2(1), will beabout 40 torr equivalent
40、 to P2(1)/P0(1) of about 0.05. If thesurface area is small, it may be desirable to eliminate use of theextra-volume bulb by closing the EV valve.9.4 Open the S valve to admit nitrogen to the catalyst.9.5 Allow sufficient time for equilibration, readjusting theliquid nitrogen level when necessary. Eq
41、uilibrium shall beconsidered as attained when the pressure change is no morethan 0.02 torr/min.9.6 Record the equilibrium pressure as P2(1), manifoldtemperature T28(1), and the extra volume bulb temperatureT2x(1).9.7 Record the liquid nitrogen temperature Ts(1) or thenitrogen vapor pressure P0(1).9.
42、8 Close the S valve and close the EV valve; then admitnitrogen gas to increase the pressure by 100 to 200 torr,depending upon surface area. Record the pressure as P1(2), themanifold temperature as T18(2), and the extra-volume bulbtemperature as T1x8(2).9.9 Open the S valve to admit the new increment
43、 of nitrogento the catalyst.9.10 Allow sufficient time for equilibration, readjusting theliquid nitrogen level as necessary. The criterion for equilibriumis defined in 9.5.9.11 Record the equilibrium pressure as P2(2), and recordT28(2) and T2x8(2).9.12 Again record Ts(2) or P0(2).9.13 Repeat Steps 9
44、.8-9.12 until there are at least four pointsin the linear BET range. This will normally be fromP/Po= 0.04 to 0.20 or 0.25. Designate the pressures as P1(i)and P2(i), manifold temperature as T8(i), and the extra-volumetemperatures as T1x(i) and T2x(i). (i =3ton, where n is totalnumber of points.)9.14
45、 Slowly open the V valve, remove the Dewar flask, andallow the sample flask to come to room temperature.9.15 When frost has disappeared from the sample tube, wipeit dry.9.16 Backfill the sample tube with the same gas used in 7.2to about atmospheric pressure. Close the S valve.9.17 Detach the sample
46、tube from the apparatus, recap withthe stopper used previously, and weigh. Record the mass as W2.10. Calculations10.1 Calculate the mass of sample Ws, as follows:Ws5 W22 W1(1)10.2 Calculate the dead-space, Vsas follows:Vs5STsVdPH2DSPH1TH11 273.2!PH2TH21 273.2!D(2)NOTE 5The user should consult IUPAC7
47、for the latest value of7IUPAC Secretariat, PO Box 13757, Research Triangle Park, NC 27709-3757.D 3663 03 (2008)3absolute zero to use in these calculations, as 273.2 was current for thisrevision.10.3 For each point, i =1,2.n, the following measure-ments will have been recorded:10.3.1 For pressures P1
48、(i) and P2(i), see 5.1.3, 9.3, 9.6, 9.8,9.11, and 9.13.10.3.2 For vapor pressures Po(i), or liquid nitrogen tempera-tures, Ts(i), see 5.7, 9.7, and 9.12.10.3.2.1 If Po(i) is not measured directly, the values of Ts(i)can be converted to P0(i) by the following equation for 76 #Ts(i) # 80:P0i! 52107293
49、 1 4269.71Tsi!# 2 57.3616Tsi!#21 0.261431Tsi!#3(3)10.3.3 For manifold temperatures T18(i) and T28(i), see 5.6,9.3, 9.6, 9.8, 9.11, and 9.13.10.3.4 Determine whether valve EV is open. If not, Vx=0,see 5.1.7.10.3.5 For extra-volume bulb temperatures T1x8(i) andT2x8(i); see 9.3, 9.6, 9.8, and 9.11.10.4 For each point, i =1,2.n, calculate the following:10.4.1 X (i) = relative pressure = P2(i)/Po(i)10.4.2 Manifold and extra-volume bulb temperatures inkelvins:T1i! 5 T18i! 1 273.2 (4)T2i! 5 T28i!1 273.2T1xi! 5 T1x8i! 1 273.2T2xi! 5 T2x8i! 1
