ASTM D4365-1995(2008) Standard Test Method for Determining Micropore Volume and Zeolite Area of a Catalyst《测定催化剂微孔体积和沸石面积的标准试验方法》.pdf

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1、Designation: D 4365 95 (Reapproved 2008)Standard Test Method forDetermining Micropore Volume and Zeolite Area of aCatalyst1This standard is issued under the fixed designation D 4365; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,

2、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 determination of totalsurface area and mesopore area. From these results are

3、calcu-lated the zeolite area and micropore volume of a zeolitecontaining catalyst. The micropore volume is related to thepercent zeolite in the catalyst. The zeolite area, a numberrelated to the surface area within the zeolite pores, may also becalculated. Zeolite area, however, is difficult to inte

4、pret inphysical terms because of the manner in which nitrogenmolecules pack within the zeolite.1.2 This 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 pr

5、actices and determine the applica-bility of regulatory limitations prior to use. For a specificprecautionary statement, see Note 3.2. Referenced Documents2.1 ASTM Standards:2D 3663 Test Method for Surface Area of Catalysts andCatalyst CarriersD 3906 Test Method for Determination of Relative X-rayDif

6、fraction Intensities of Faujasite-Type Zeolite-Containing MaterialsE 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. Termino

7、logy3.1 Definitions of Terms Specific to This Standard:3.1.1 mesopore area of a catalystthe area determinedfrom the slope of the t-plot.3.1.2 micropore volume of the catalystthe pore volume inpores having radii less than 1 nm, usually associated with thezeolite portion of the catalyst, and determine

8、d from theintercept of the t-plot.3.1.3 surface area of a catalystthe total surface of thecatalyst pores. It is expressed in square metres per gram.3.1.4 zeolite area of a catalystthe difference between totalsurface area and mesopore area.3.2 Symbols:PH1= initial helium pressure, torrPH2= helium pre

9、ssure after equilibration, torrSB= slope of BET plot, 11.7IB= intercept of BET plot, 11.7St= slope of t-plot, 11.13It= intercept of t-plot, 11.13TH1= temperature of manifold at initial helium pres-sure, CTH2= temperature of manifold after equilibration, CTx8(i) = extra volume bulb temperature, CTx(i

10、) = extra volume bulb temperature, KP1(i) = initial N2pressure, torrT1(i) = manifold temperature at initial N2pressure, KT18(i) = manifold temperature at initial N2pressure, CP2(i) = pressure after equilibration, torrT2(i) = manifold temperature after equilibration, KT28(i) = manifold temperature af

11、ter equilibration, CP0(i) = liquid nitrogen vapor pressure, torrTs(i) = liquid nitrogen temperature, KX = relative pressure, P2/P0Vd= volume of manifold, cm3Vx= extra volume bulb, cm3Vs= effective void volume, cm3Ws= weight of sample, gW1= tare weight of sample tube, gW2= weight of sample + tare wei

12、ght of tube, gVds= volume of nitrogen in the dead-space, cm3V1= see 11.4.3V2= see 11.4.4Vt= see 11.4.51This test method is 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

13、, 2008. Published May 2008. Originallyapproved in 1984. Last previous edition approved in 2007 as D 436595(2007)e1.2For 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 t

14、he standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Va= see 11.4.7Vm= see 11.8BET (i) = see 11.4.8t(i) = see 11.104. Summary of Test Method4.1 The volume of nitrogen gas adsorbed by t

15、he catalyst atliquid nitrogen temperature is measured at various low-pressure levels. This is done by measuring pressure differen-tials caused by introducing a fixed volume of nitrogen to thedegassed catalyst in the test apparatus. This procedure is thesame as Test Method D 3663, that gives total su

16、rface area, butextends the pressure range to permit calculation of microporevolume and matrix surface area, by the t-plot method. Zeolitearea is the difference between total area and matrix area.5. Significance and Use5.1 This gas adsorption method complements the X-rayprocedure of Test Method D 390

17、6. This test method will beuseful to laboratories that do not have X-ray diffractometers.Each test method can be calibrated by use of an appropriateseries of mechanical mixtures to provide what may be termedpercent zeolite. If there is disorder in the zeolite, the adsorptionmethod will yield higher

18、values than the X-ray method. Thereverse will be true if some zeolite pores (micropores) areblocked or filled.6. Apparatus6.1 Aschematic diagram of the apparatus is shown in Fig. 1.It may be constructed of glass or of metal. It has the followingfeatures:6.1.1 Distribution Manifold, having a volume b

19、etween 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 gage. It is preferred that this volume bethermostatted.6.1.2 Vacuum System, capable of attaining pressures below104torr (1 torr = 133.3 Pa). This will

20、 include a vacuum gage(not shown in Fig. 1). Access to the distribution manifold isthrough the valve V.6.1.3 Constant-Volume Gage or Mercury Manometer, ca-pable of measurements to the nearest 0.1-torr sensitivity in therange from 0 to 1000 torr (1 torr = 133.3 Pa).NOTE 1See, for example, the article

21、 by Joy for a description of aconstant-volume manometer.36.1.4 Valve (H), from the helium supply to the distributionmanifold.6.1.5 Value (N), from the nitrogen supply to the distributionmanifold.6.1.6 The connection between the sample tube and the Svalve can be a standard-taper glass joint, a glass-

22、to-glass seal,or a compression fitting.6.1.7 Extra Volume (EV) Bulb, may be attached throughvalve EV. Its volume (Vx) should be 100 to 150 cm3, known tothe nearest 0.05 cm3. Vxincludes the volume of the stopcockbore in the glass apparatus. It is preferred that this volume beheld at the same temperat

23、ure as that of the distributionmanifold.NOTE 2Modern commercial instruments automatically adjust theamounts dosed in order to produce data points at user-selected targetpressures. Hence, the use of an EV bulb is optional. Some instruments cananalyze multiple samples simultaneously and may use sample

24、 tubes withvolumes outside of the range specified in this test method.6.2 Sample Tubes, with volumes from 5 cm3to 25 cm3depending on the application. Markings should be placed onthe sample tubes about 30 to 50 mm below the connectors toindicate the desired liquid nitrogen level.6.3 Heating Mantles o

25、r Small Furnaces.6.4 Dewar Flasks.6.5 Laboratory Balance, with 0.1 mg (107kg) sensitivity.6.6 Thermometer, for measuring the temperature of thedistribution manifold, T18(i)orT28(i), in degrees Celsius.6.7 Thermometer, for measuring the temperature of theliquid nitrogen bath Ts(i) in kelvins. This wi

26、ll preferably be anitrogen vapor-pressure-thermometer that gives P0directly andhas greater precision, or a resistance thermometer from whichP0values may be derived.6.8 Thermometer, for measuring the temperature of the EVbulb, Tx8(i), if different from T18(i)orT28(i).7. Reagents7.1 Purity of Reagents

27、Reagent 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.4Other grades may beused, provided it i

28、s first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Helium GasA cylinder of helium gas at least 99.9 %pure.7.3 Liquid Nitrogen, of such purity that P0is not more than20 torr above barometric pressure. A fresh dai

29、ly supply isrecommended.7.4 Nitrogen GasA cylinder of nitrogen gas at least99.9 % pure.8. ProcedureSample Preparation and Degassing8.1 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 m

30、aybe preferred for finely powdered catalysts, to avoid “boiling”when degassing is started.8.2 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.3Joy, A. S., Vacuum, Vol

31、 3, 1953, p. 254.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United

32、States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 4365 95 (2008)28.3 Remove the sample tube from the system, cap, andweigh. Record the weight as W1.8.4 Place the catalyst sample, of which the weight is knownapproximately, into the sample tube. Choo

33、se the sample size toprovide an estimated total sample surface area of 20 to 100 m2.8.5 Attach the sample tube to the apparatus. If other samplesare to be run, attach them at this time to the other ports.8.6 Open the S valves where there are samples.8.7 Slowly open the V valve, monitoring the rate o

34、f pressuredecrease to avoid too high a rate, which could lead to excessivefluidization of powdered samples.8.7.1 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

35、for 2 min each time.8.8 Install a heating mantle or furnace around each sampleand raise the temperature to about 300C (573 K).NOTE 3Take special precautions if the moisture content exceedsapproximately 5 % to avoid “bumping” of powdered catalyst, and to avoidsurface area loss by self-steaming. It is

36、 recommended that the heating ratenot exceed 100C(K)/h under these circumstances.8.9 Continue degassing at about 300C (573 K) for aminimum of 3 h, at a pressure not to exceed 103torr.Overnight degassing is permissible.NOTE 4Zeolite-containing catalysts may contain large quantities ofwater. Pretreatm

37、ent of the sample in an oven at 400C in flowing nitrogenfor a couple of hours may be desirable.8.10 Remove the heating mantles, and allow the samples tocool.8.11 Close the EV valve, if open.8.12 Close the S valve.8.13 It is permissible to exercise the option of preliminarydegassing on an external un

38、it. In such a case, follow theprocedures of 8.4-8.11 and then repeat on the surface area unit,except that the degassing time in 8.9 should not exceed 1 h.8.14 If it is desired to weigh the sample after preliminarydegassing on an external unit, backfill with the same gas usedin 8.2 to above atmospher

39、ic pressure. Close the S valve.Otherwise, use the weight obtained in 10.18 and omit 8.15.8.15 Detach the sample tube from the apparatus, recap withthe stopper used previously, and weigh. Record the weight asW2.8.16 Remove the backfilled gas by evacuation to less than104torr at room temperature.9. Pr

40、ocedureDead-Space Determination9.1 From this point on, each sample being tested formicropore volume and surface area must be run on anindividual basis. Thus, each Step 9.2-10.17 must be carried outseparately for each tube in test.9.2 The “dead-space” is the void volume of the chargedsample tube, inc

41、luding the volume within the S valve, when thetube is immersed in liquid nitrogen to the proper depth.NOTE 5The dead-space may be determined after the nitrogen adsorp-tion, if more convenient, so long as adequate degassing precedes itsdetermination. In that case, replace the liquid nitrogen bath aft

42、er 10.14before proceeding with 9.3-9.9. Then, remove the Dewar flask beforecarrying out 10.15-10.17.9.3 Place a Dewar flask of liquid nitrogen around the sampleand adjust the liquid level to a fixed point on the sample tube.Maintain this level throughout the test.9.4 Zero the pressure gage.9.5 Admit

43、 the helium gas into the system to a pressure of600 to 900 torr by carefully opening the H valve. With H valveclosed, record this pressure, PH1, and the manifold temperature,TH1.9.6 Open the S valve to admit helium to the sample.9.7 After about 5 min of equilibration, readjust the liquidnitrogen lev

44、el, and record the pressure, PH2, and the manifoldtemperature, TH2.9.8 Repeat 9.5-9.7 for each sample cell attached to themanifold.9.9 Open all S valves; then slowly open the V valve toremove the helium gas.9.10 When a pressure less than 0.01 torr has been attained,close the S valve. This operation

45、should take 5 to 10 min.10. ProcedureNitrogen Adsorption10.1 Close the V valve and open the EV valve. (The extravolume bulb should be thermostatted at a particular tempera-ture, a few degrees above ambient.)10.2 Recheck the zero setting of the pressure gage.10.3 Admit nitrogen gas, and record the pr

46、essure as P1(1)(torr) and the temperature as T18 (1) (degrees Celsius). It isdesirable, but not necessary, to choose P1(1) such that the firstequilibrium adsorption pressure, P2(1) will be about 8 to 15torr, or P2(1)/P0of about 0.01 to 0.02. Record Tx8(1). Close theEV valve.10.4 Open the S valve to

47、admit nitrogen to the catalyst.FIG. 1 Schematic Diagram of Surface Area ApparatusD 4365 95 (2008)310.5 Allow sufficient time for equilibration, readjusting theliquid nitrogen level when necessary. Equilibrium shall beconsidered as attained when the pressure change is no morethan 0.1 torr in 5 min. I

48、f the equilibrium pressure is too low,open EV valve and re-equilibrate the system.10.6 Record the equilibrium pressure as P2(1), and manifoldtemperature T28(1).10.7 Record the liquid nitrogen temperature Ts(1) or thenitrogen vapor pressure P0(1).10.8 Close the S valve and close the EV valve; then ad

49、mitnitrogen gas to increase the pressure as needed (usually by 100to 200 torr), depending upon surface area. The incrementsshould be small (usually smaller than 100 to 200 torr) whenP/P0is less than 0.1. Record the pressure, P1(2), and thetemperature, T18(2).10.9 Open the S valve to admit the new increment ofnitrogen to the catalyst.10.10 Allow sufficient time for equilibration, readjusting theliquid nitrogen level as necessary. The criterion for equilibriumis defined in 10.5.10.11 Record the equilibrium pressure as P2(2), and recordT28(2).10.12 Again rec