1、Designation: D3663 03 (Reapproved 2015)Standard Test Method forSurface Area of Catalysts and Catalyst Carriers1This standard is issued under the fixed designation D3663; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 surfaceareas of catalyst and catalyst carriers that have Type II or IVnitr
3、ogen 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 BET2equation line.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 T
4、his standard 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 Docume
5、nts2.1 ASTM Standards:3D3766 Terminology Relating to Catalysts and CatalysisE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. T
6、erminology3.1 Consult Terminology D3766 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= temp
7、erature of manifold at initial helium pressure,CTH2= temperature of manifold after equilibration, CP1= initial N2pressure, torrT1= manifold temperature at initial N2pressure, KT1 = 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 10
9、.4.6Vt= see 10.4.7Va= see 10.4.9Vm= see 10.8T1x= initial extra-volume bulb temperature, KT1 x(i ) = initial extra-volume bulb temperature, CT2 x= extra-volume bulb temperature after equilibrium,KT2 x(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 calc
11、ulate 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:1This test method is under the jurisdiction of ASTM Committee D32 onCatalysts and is the direct responsibility of Subcommittee D32.0
12、1 on Physical-Chemical Properties.Current edition approved April 1, 2015. Published June 2015. Originallyapproved in 1978. Last previous edition approved in 2008 as D3663 03 (2008).DOI: 10.1520/D3663-03R15.2Brunauer, Emmett, Teller, Journal of American Chemical Society,JACS, No.60, 1938, p. 309.3For
13、 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 onthe ASTM website.4Automated equipment is commercially available.Copyright ASTM Int
14、ernational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.1.1 Distribution Manifold, having a volume between 20and 35 cm3,(Vd), known to the nearest 0.05 cm3. This volumeis defined as the volume between the stopcocks or valves andincludes the pressure gauge.5.
15、1.2 Vacuum System, capable of attaining pressures below104torr (1 torr = 133.3 Pa). This will include a vacuum gauge(not shown in Fig. 1). Access to the distribution manifold isthrough the valve V.5.1.3 Constant-Volume Gauge or Mercury Manometer, ca-pable of measurements to the nearest 0.1 torr, in
16、the range from0 to 1000 torr (1 torr = 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 b
17、etween the sample tube and the Svalve 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 vol
18、umes from 5 to 100 cm3depend-ing on 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 (107kg) sensitivity.5.6 The
19、rmometer or Thermocouple, for measuring the tem-perature of the distribution manifold T1(i)orT2(i) in degreesCelsius.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.
20、5.7 Thermometer, for measuring the temperature of theliquid nitrogen bath Ts(i) in kelvins. This will preferably bea nitrogen vapor-pressure thermometer, often referred to in acommercial instrument as a pressure saturation tube, fromwhich P0values may be derived.6. Reagents6.1 Purity of ReagentsReag
21、ent grade chemicals shall beused 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 fi
22、rst ascertained that the reagent 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 s
23、upply isrecommended.6.4 Nitrogen 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 may
24、be preferred for finely powdered 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
25、 from the system, cap, andweigh. Record the mass as W1.7.4 Place the catalyst sample, whose mass is knownapproximately, into the sample tube. Choose the sample size toprovide an estimated total sample surface area of 20 to 100 m2.5Joy, A. S., Vacuum, Vol 3, 1953, p. 254.6Reagent Chemicals, American
26、Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S
27、. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Schematic Diagram of Surface Area ApparatusD3663 03 (2015)27.5 Attach the sample tube to the apparatus. If other samplesare to be run, attach them at this time to the other ports.7.6 Open the S valves where there are samples.7.7 It may be
28、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 furnace around each sampleand raise the temperature to about 300C (573 K).NOTE 2T
29、ake special precautions if the moisture content exceedsapproximately 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 amini
30、mum of 3 h, at a pressure not 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 tempera
31、ture should be specified when 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
32、 7.4 7.11 and then repeat on the surface areaunit, except that the degassing time in 7.9 should not exceed 1h.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 t
33、he sample tube from the apparatus, 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
34、 run on an individual basis. Thus each Step 8.2 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 de
35、termined after the nitrogenadsorption, if more convenient, as long as adequate degassing precedes it.In that case, replace the liquid nitrogen bath after Step 9.14 beforeproceeding with Steps 8.3 8.9.8.3 Place a Dewar flask of liquid nitrogen around the sampleand adjust the liquid level to a fixed p
36、oint on the sample tube.Maintain this level throughout the test.8.4 Zero the pressure gauge.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
37、to the sample.8.7 After about 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
38、less than 0.01 torr has been 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 gaug
39、e.9.3 Admit nitrogen gas, and record the pressure as P1(1)(torr) and the temperature as T1(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
40、 beabout 40 torr equivalent 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 nitrog
41、en level when necessary. Equilibrium 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 T2(1), and the extra volume bulb temperatureT2x(1).9.7 Record the liquid nitrogen temperature Ts(1) or thenitrog
42、en vapor pressure P0(1).9.8 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 T1(2), and the extra-volume bulbtemperature as T1 x(2).9.9 Open the S valve t
43、o admit the new increment 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 recordT2(2) and T2x(2).9.12 Again record Ts(2) or P0
44、(2).9.13 Repeat Steps 9.8 9.12 until there are at least fourpoints in the linear BET range. This will normally be fromP/Po= 0.04 to 0.20 or 0.25. Designate the pressures as P1(i)D3663 03 (2015)3and P2(i), manifold temperature as T(i ), and the extra-volumetemperatures as T1x(i) and T2x(i). (i =3ton,
45、 where n is totalnumber of points.)9.14 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. Cl
46、ose the S valve.9.17 Detach the sample 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:Vs5STsVdPH2DSPH1TH11273.2!2PH2TH21273.2!D(
47、2)NOTE 5The user should consult IUPAC7for the latest value ofabsolute 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(i) and P2(i), see 5.1.3, 9.3, 9.6, 9.8,9.11, and 9
48、.13.10.3.2 For vapor pressures Po(i), or liquid nitrogentemperatures, 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! 5210729314269.71Tsi!# 2 57.3616Tsi!#2(3)10.261431Tsi!#310.3.3 Fo
49、r manifold temperatures T1(i) and T2(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 T1x(i) and T2x(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 T1i!1273.2 (4)T2i! 5 T2i!1273.2T1xi! 5 T1xi!1273.2T2xi! 5 T2xi!1273.210.4.3 Extra-volume bulb volum
