ASTM D3663-03(2008)
(Test Method)Standard Test Method for Surface Area of Catalysts and Catalyst Carriers
Standard Test Method for Surface Area of Catalysts and Catalyst Carriers
ABSTRACT
This test method establishes the standard procedure for determining the surface areas of catalyst and catalyst carriers that have Type II or IV nitrogen adsorption isotherms, and specified minimum area. A volumetric measuring system is used to obtain at least four data points which fit on the linear BET line. The surface area of a catalyst or catalyst carrier is determined by measuring the volume of nitrogen gas adsorbed at various low-pressure levels by the catalyst sample. Pressure differentials caused by introducing the catalyst surface area to a fixed volume of nitrogen in the test apparatus are measured and used to calculate BET surface area.
SCOPE
1.1 This test method covers the determination of surface areas of catalyst and catalyst carriers that have Type II or IV nitrogen adsorption isotherms, and at least 1 m2/g of area. A volumetric measuring system is used to obtain at least four data points which fit on the linear BET line.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D3663 − 03(Reapproved 2008)
Standard Test Method for
Surface Area of Catalysts and Catalyst Carriers
This standard is issued under the fixed designation D3663; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
P = initial helium pressure, torr
1.1 This test method covers the determination of surface H
P = helium pressure after equilibration, torr
H
areas of catalyst and catalyst carriers that have Type II or IV
T = temperatureofmanifoldatinitialheliumpressure,
H
nitrogen adsorption isotherms, and at least 1 m /g of area. A
°C
volumetricmeasuringsystemisusedtoobtainatleastfourdata
2 T = temperature of manifold after equilibration, °C
H
points which fit on the linear BET line. 2
P = initial N pressure, torr
1 2
1.2 The values stated in SI units are to be regarded as the
T = manifold temperature at initial N pressure, K
1 2
standard. The values given in parentheses are for information
T ' = manifold temperature at initial N pressure, °C
1 2
only. P = pressure after equilibration, torr
P = liquid nitrogen vapor pressure, torr
1.3 This standard does not purport to address all of the
T = liquid nitrogen temperature, K
s
safety concerns, if any, associated with its use. It is the
X = relative pressure, P /P
2 0
responsibility of the user of this standard to establish appro-
V = volume of manifold, cm
d
priate safety and health practices and determine the applica- 3
V = extra volume bulb, cm
x
bility of regulatory limitations prior to use. 3
V = dead-space volume, cm
s
W = mass of sample, g
s
2. Referenced Documents
W = tare mass of sample tube, g
2.1 ASTM Standards: W = sample+tare mass of tube, g
V = volume of nitrogen in the dead-space, cm
D3766Terminology Relating to Catalysts and Catalysis
ds
V = see 10.4.4
E177Practice for Use of the Terms Precision and Bias in
V = see 10.4.6
ASTM Test Methods 2
V = see 10.4.7
E456Terminology Relating to Quality and Statistics t
V = see 10.4.9
a
E691Practice for Conducting an Interlaboratory Study to
V = see 10.8
m
Determine the Precision of a Test Method
T = initial extra-volume bulb temperature, K
1x
T '(i ) = initial extra-volume bulb temperature, °C
1 x
3. Terminology
T = extra-volume bulb temperature after equilibrium,
2 x
3.1 Consult Terminology D3766 for definitions of other
K
terms used.
T '(i ) = extra-volume bulb temperature after equilibrium,
2 x
°C
3.2 Definitions:
3.2.1 surface area of a catalyst—the total surface of the
4. Summary of Test Method
catalyst. It is expressed in square metres per gram.
4.1 The surface area of a catalyst or catalyst carrier is
3.3 Symbols:
determined by measuring the volume of nitrogen gas adsorbed
at various low-pressure levels by the catalyst sample. Pressure
differentials caused by introducing the catalyst surface area to
This test method is under the jurisdiction of ASTM Committee D32 on
a fixed volume of nitrogen in the test apparatus are measured
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
Chemical Properties.
and used to calculate BET surface area.
Current edition approved April 1, 2008. Published April 2008. Originally
approved in 1978. Last previous edition approved in 2003 as D3663–03. DOI:
5. Apparatus
10.1520/D3663-03R08.
5.1 AschematicdiagramoftheapparatusisshowninFig.1.
Brunauer, Emmett, Teller, Journal of American Chemical Society, JACS, No.
60, 1938, p. 309.
It may be constructed of glass or of metal. It has the following
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
features:
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Automated equipment is commercially available.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3663 − 03 (2008)
FIG. 1 Schematic Diagram of Surface Area Apparatus
5.1.1 Distribution Manifold, having a volume between 20 commercial instrument as a pressure saturation tube, from
3 3
and 35 cm,(V ), known to the nearest 0.05 cm . This volume which P values may be derived.
d 0
is defined as the volume between the stopcocks or valves and
6. Reagents
includes the pressure gage.
5.1.2 Vacuum System, capable of attaining pressures below
6.1 Purity of Reagents—Reagent grade chemicals shall be
−4
10 torr (1 torr=133.3 Pa). This will include a vacuum gage
used in all tests. Unless otherwise indicated, it is intended that
(not shown in Fig. 1). Access to the distribution manifold is
all reagents shall conform to the specifications of the Commit-
through the valve V.
tee onAnalytical Reagents of theAmerican Chemical Society,
5.1.3 Constant-Volume Gage or Mercury Manometer, ca-
where such specifications are available. Other grades may be
pableofmeasurementstothenearest0.1torr,intherangefrom
used, provided it is first ascertained that the reagent is of
0 to 1000 torr (1 torr=133.3 Pa).
sufficiently high purity to permit its use without lessening the
accuracy of the determination.
NOTE 1—See, for example, the article by Joy for a description of a
constant-volume manometer.
6.2 Helium Gas—A cylinder of helium gas at least 99.9%
5.1.4 Valve (H), from the helium supply to the distribution pure.
manifold.
6.3 Liquid Nitrogen, of such purity that P is not more than
5.1.5 Valve (N), from the nitrogen supply to the distribution
20 torr above barometric pressure. A fresh daily supply is
manifold.
recommended.
5.1.6 The connection between the sample tube and the S
6.4 Nitrogen Gas—A cylinder of nitrogen gas at least
valve can be a standard-taper glass joint, a glass-to-glass seal,
99.999% pure.
or a compression fitting.
5.1.7 Extra Volume Bulb, (V ), should be 100 to 150 cm ,
x
3 7. Procedure—Sample Preparation and Degassing
known to the nearest 0.05 cm . V includes the volume of the
x
stopcock bore in the glass apparatus. 7.1 Selectasampletubeofthedesiredsize.A5-cm sample
3 tube is preferred for samples not exceeding about 1 g, to
5.2 Sample Tubes,withvolumesfrom5to100cm depend-
minimizethedead-space.However,a25-cm sampletubemay
ing on the application. Markings should be placed on the
be preferred for finely powdered catalysts, to avoid “boiling”
sample tubes about 30 to 50 mm below the connectors to
when degassing is started.
indicate the desired liquid nitrogen level.
7.2 Fill the sample tube with nitrogen or helium, at atmo-
5.3 Heating Mantles or Small Furnaces.
sphericpressure,afterremovingairbyevacuation.Thismaybe
5.4 Dewar Flasks.
done on the surface area unit, or on a separate piece of
−7
equipment.
5.5 Laboratory Balance, with 0.1-mg (10 -kg) sensitivity.
7.3 Remove the sample tube from the system, cap, and
5.6 Thermometer or Thermocouple, for measuring the tem-
weigh. Record the mass as W .
peratureofthedistributionmanifold[T '(i)or T '(i)]indegrees
1 2 1
Celsius.
7.4 Place the catalyst sample, whose mass is known
5.6.1 It is preferred that the manifold be thermostated at a
approximately,intothesampletube.Choosethesamplesizeto
particulartemperature,afewdegreesaboveambient,toobviate
provideanestimatedtotalsamplesurfaceareaof20to100m .
the necessity of recording this temperature at each reading.
5.7 Thermometer, for measuring the temperature of the
Reagent Chemicals, American Chemical Society Specifications, American
liquid nitrogen bath [ T (i)] in kelvins. This will preferably be
s
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
a nitrogen vapor-pressure thermometer, often referred to in a
listed by the American Chemical Society, see Annual Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
Joy, A. S., Vacuum, Vol 3, 1953, p. 254. MD.
D3663 − 03 (2008)
7.5 Attachthesampletubetotheapparatus.Ifothersamples 8.5 Admit the helium gas into the manifold to a pressure of
are to be run, attach them at this time to the other ports. 600 to 900 torr by carefully opening the H valve. Record this
pressure as P , and the manifold temperature, T .
H1 H1
7.6 Open the S valves where there are samples.
8.6 Open the S valve to admit helium to the sample.
7.7 It may be necessary to close the V valve system
8.7 After about 5 min of equilibration, readjust the liquid
periodically to protect the diffusion pump fluid from exposure
nitrogen level, and record the pressure as P , and manifold
topressuresabove0.1torrforperiodsofmorethan30s.Close
H2
temperature as T .
the valve off for 2 min. H2
8.8 Repeat 8.5 – 8.7 for each sample on the manifold.
7.8 Install a heating mantle or furnace around each sample
and raise the temperature to about 300°C (573 K).
8.9 Open all S valves; then slowly open the V valve to
remove the helium gas.
NOTE 2—Take special precautions if the moisture content exceeds
approximately5%toavoid“bumping”ofpowderedcatalyst,andtoavoid
8.10 When a pressure less than 0.01 torr has been attained,
surfacearealossbyself-steaming.Itisrecommendedthattheheatingrate
close the S valve. This operation should take 5 to 10 min.
not exceed 100K⁄h under these circumstances.
7.9 Continue degassing at about 300°C (573K) for a
9. Procedure—Nitrogen Adsorption
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
9.1 Close the V valve and open the EVvalve if the extra-
Overnight degassing is permissible.
volume bulb is to be used, when the surface area is known to
be high.
NOTE 3—Certain materials will decompose at 300°C (for example,
alumina hydrates) or will sinter (for example, platinum black). Lower
9.2 Recheck the zero setting of the pressure gage.
degassing temperatures are permissible for such materials; however, the
degassing temperature should be specified when reporting the results.
9.3 Admit nitrogen gas, and record the pressure as P (1)
(torr) and the temperature as T '(1) (degrees Celsius) and read
7.10 Remove the heating mantles, and allow the samples to 1
the temperature of the extra-volume bulb and record it as
cool.
T (1). It is desirable, but not necessary, to choose P (1) such
1x 1
7.11 Close the EV valve, if open.
that the first equilibrium adsorption pressure, P (1), will be
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D3663–99 Designation: D 3663 – 03 (Reapproved 2008)
Standard Test Method for
Surface Area of Catalysts and Catalyst Carriers
This standard is issued under the fixed designation D3663; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of surface areas of catalyst and catalyst carriers that have Type II or IV nitrogen
adsorption isotherms, and at least 1 m /g of area.Avolumetric measuring system is used to obtain at least four data points which
fit on the linear BET line.
1.2This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D3766Terminology Relating to Catalysts and Catalysis
D3766 Terminology Relating to Catalysts and Catalysis
E177 Practice for Use of the Terms Precisions and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Consult Terminology D3766 for definitions of other terms used.
3.2 Definition: Definitions:
3.2.1 surface area of a catalyst—the total surface of the catalyst. It is expressed in square metres per gram.
3.3 Symbols:
P = initial helium pressure, torr
H
P = helium pressure after equilibration, torr
H
T = temperature of manifold at initial helium pressure, °C
H
T = temperature of manifold after equilibration, °C
H
P = initial N pressure, torr
1 2
T = manifold temperature at initial N pressure, K
1 2
T 8 = manifold temperature at initial N pressure, °C
1 2
P = pressure after equilibration, torr
P = liquid nitrogen vapor pressure, torr
T = liquid nitrogen temperature, K
s
This test method is under the jurisdiction of ASTM Committee D-32 on Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-Chemical
Properties.
e1
Current edition approved Oct. 10, 1999. Published December 1999. Originally published as D3663–78. Last previous edition D3663–92 (1999) .
This test method is under the jurisdiction of ASTM Committee D32 on Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-Chemical
Properties.
Current edition approved April 1, 2008. Published April 2008. Originally approved in 1978. Last previous edition approved in 2003 as D3663–03.
Brunauer, Emmett, Teller, Journal of American Chemical Society, JACS, No. 60, 1938, p. 309.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
, Vol 05.03.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 3663 – 03 (2008)
X = relative pressure, P /P
2 0
V = volume of manifold, cm
d
V = extra volume bulb, cm
x
V = dead-space volume, cm
s
W = weightmass of sample, g
s
W = tare weightmass of sample tube, g
W = sample+tare weightmass of tube, g
V = volume of nitrogen in the dead-space, cm
ds
V = see 10.4.4
V = see 10.4.6
V = see 10.4.7
t
V = see 10.4.9
a
V = see 10.8
m
T = initial extra-volume bulb temperature, K
1x
T 8(i ) = initial extra-volume bulb temperature, °C
1 x
T = extra-volume bulb temperature after equilibrium, K
2 x
T 8(i ) = extra-volume bulb temperature after equilibrium, °C
2 x
4. Summary of Test Method
4.1 The surface area of a catalyst or catalyst carrier is determined by measuring the volume of nitrogen gas adsorbed at various
low-pressure levels by the catalyst sample. Pressure differentials caused by introducing the catalyst surface area to a fixed volume
of nitrogen in the test apparatus are measured and used to calculate BET surface area.
5. Apparatus
5.1 A schematic diagram of the apparatus is shown in Fig. 1. It may be constructed of glass or of metal. It has the following
features:
3 3
5.1.1 Distribution Manifold, having a volume between 20 and 35 cm,( V ), known to the nearest 0.05 cm . This volume is
d
defined as the volume between the stopcocks or valves and includes the pressure gage.
−4
5.1.2 Vacuum System, capable of attaining pressures below 10 torr (1 torr=133.3 Pa). This will include a vacuum gage (not
shown in Fig. 1). Access to the distribution manifold is through the valve V.
5.1.3 Constant-Volume Gage or Mercury Manometer, capable of measurements to the nearest 0.1 torr, in the range from 0 to
1000 torr (1 torr=133.3 Pa).
NOTE1—See, for example, the article by Joy, A. S., Vacuum, Vol 3, 1953, p. 254, for a description of a constant-volume manometer. 1—See, for
example, the article by Joy for a description of a constant-volume manometer.
5.1.4 Valve (H), from the helium supply to the distribution manifold.
5.1.5 Valve (N), from the nitrogen supply to the distribution manifold.
5.1.6 The connection between the sample tube and the S valve can be a standard-taper glass joint, a glass-to-glass seal, or a
compression fitting.
3 3
5.1.7 Extra Volume Bulb,(V ),shouldbe100to150cm ,knowntothenearest0.05cm . V includesthevolumeofthestopcock
x x
bore in the glass apparatus.
5.2 Sample Tubes, with volumes from 5 to 25100 cm depending on the application. Markings should be placed on the sample
tubes about 30 to 50 mm below the connectors to indicate the desired liquid nitrogen level.
Annual Book of ASTM Standards, Vol 14.02.
Automated equipment is commercially available.
Automated equipment is commercially available.
Joy, A. S., Vacuum, Vol 3, 1953, p. 254.
FIG. 1 Schematic Diagram of Surface Area Apparatus
D 3663 – 03 (2008)
5.3 Heating Mantles or Small Furnaces .
5.4 Dewar Flasks.
−7
5.5 Laboratory Balance, with 0.1-mg (10 -kg) sensitivity.
5.6 ThermometerThermometer or Thermocouple , for measuring the temperature of the distribution manifold [T 8(i)or T 8(i)]
1 2
in degrees Celsius.
5.6.1 It is preferred that the manifold be thermostated at a particular temperature, a few degrees above ambient, to obviate the
necessity of recording this temperature at each reading.
5.7 Thermometer,formeasuringthetemperatureoftheliquidnitrogenbath[ T (i)]inkelvins.Thiswillpreferablybeanitrogen
s
vapor-pressurethermometerfromwhich )] in kelvins. This will preferably be a nitrogen vapor-pressure thermometer, often referred
to in a commercial instrument as a pressure saturation tube, from which P values may be derived.
6. Reagents
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
6.2 Helium Gas—A cylinder of helium gas at least 99.9% pure.
6.3 Liquid Nitrogen, of such purity that P is not more than 20 torr above barometric pressure. A fresh daily supply is
recommended.
6.4 Nitrogen Gas—A cylinder of nitrogen gas at least 99.999% pure.
7. Procedure—Sample Preparation and Degassing
7.1 Selectasampletubeofthedesiredsize.A5-cm sampletubeispreferredforsamplesnotexceedingabout1g,tominimize
thedead-space.However,a25-cm sampletubemaybepreferredforfinelypowderedcatalysts,toavoid“boiling”whendegassing
is started.
7.2 Fill the sample tube with nitrogen or helium, at atmospheric pressure, after removing air by evacuation. This may be done
on the surface area unit, or on a separate piece of equipment.
7.3 Remove the sample tube from the system, cap, and weigh. Record the weightmass as W .
7.4 Place the catalyst sample, whose weightmass is known approximately, into the sample tube. Choose the sample size to
provide an estimated total sample surface area of 20 to 100 m .
7.5 Attach the sample tube to the apparatus. If other samples are 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 necessary to close the Vvalve system periodically to protect the diffusion pump fluid from exposure to pressures
above 0.1 torr for periods of more than 30 s. Close the valve off for 2 min.
7.8 Install a heating mantle or furnace around each sample and raise the temperature to about 300°C (573 K).
NOTE 2—Take special precautions if the moisture content exceeds approximately 5% to avoid “bumping” of powdered catalyst, and to avoid surface
area loss by self-steaming. It is recommended that the heating rate not exceed 100K/h under these circumstances.
−3
7.9 Continuedegassingatabout300°C(573K)foraminimumof3h,atapressurenottoexceed10 torr.Overnightdegassing
is permissible.
NOTE 3—Certain materials will decompose at 300°C (for example, alumina hydrates) or will sinter (for example, platinum black). Lower degassing
temperatures are permissible for such materials; however, the degassing temperature should be specified when reporting the results.
7.10 Remove the heating mantles, and allow the samples to cool.
7.11 Close the EV valve, if open.
7.12 Close the S valve.
7.13 It is permissible to exercise the option of preliminary degassing on an external unit. In such a case, follow the procedures
of 7.4-7.11 and then repeat on 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 preliminary degassing on an external unit, backfill with the same gas used in 7.2
to above atmospheric pressure. Close the S valve.
7.15 Detach the sample tube from the apparatus, recap with the stopper used previously, and weigh. Record the weightmass as
W .
−4
7.16 Remove the backfilled gas by evacuation to less than 10 torr at room temperature.
8. Procedure—Dead-Space Determination
8.1 From this point on, each sample being tested for surface area must be run on an individual basis. Thus each Step 8.2-9.17
Reagent Chemicals, American Chemical Society Specifications, Am.American Chemical Soc.,Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals,,” BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and
National Formulary,, U. S. U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D 3663 – 03 (2008)
must be carried out separately for each tube in test.
8.2 The“dead-space”isthevoidvolumeofthechargedsampletube,includingthe Svalve,whenthetubeisimmersedinliquid
nitrogen to the proper depth (see 5.2).
NOTE 4—The dead-space may be determined after the nitrogen adsorption, if more convenient, as long as adequate degassing precedes it. In that case,
replace the liquid nitrogen bath after Step 9.14 before proceeding with Steps 8.3-8.9.
8.3 Place a Dewar flask of liquid nitrogen around the sample and adjust the liquid level to a fixed point on the sample tube.
Maintain this level throughout the test.
8.4 Zero the pressure gage.
8.5 Admit the helium gas into the manifold to a pressure of 600 to 900 torr by carefully opening the H valve. Record this
pressure as P , and the manifold temperature, T .
H1 H 1
8.6 Open the S valve to admit helium to the sample.
8.7 After about 5 min of equilibration, readjust the liquid nitrogen level, and record the pressure as P , and manifold
H2
temperature as T .
H2
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 to remove the helium gas.
8.10 When a pressure less than 0.01 torr has been attained, close the S valve. This operation should take 5 to 10 min.
9. Procedure—Nitrogen Adsorption
9.1 Close the V valve and open the EVvalve if the extra-volume bulb is to be used, when the surface area is known to be high.
9.2 Recheck the zero setting of the pressure gage.
9.3 Admit nitrogen gas, and record the pressure as P (1) (torr) and the temperature as T 8(1) (degrees Celsius) and read the
1 1
temperature of the extra-volume bulb and record it as T (1). It is desirable, but not necessary, to choose P (1) such that the first
1x 1
equilibrium adsorption pressure, P (1), will be about 40 torr equivalent to P (1)/P (1) of about 0.05. If the surface area is small,
2 2 0
it may be desirable to eliminate use of the extra-volume bulb by closing the EV valve.
9.4 Open the S valve to admit nitrogen to the catalyst.
9.5 Allowsufficienttimeforequilibration,readjustingtheliquidnitrogenlevelwhennecessary.Equilibriumshallbeconsidered
as attained when the pressure change is no more than 0.1 torr in 5 min. 0.02 torr/min.
9.6 Record the equilibrium pressure as P (1), manifold temperature T 8(1), and the extra volume bulb temperature T (1).
2 2 2x
9.7 Record the liquid nitrogen temperature [ T (1)] or the nitrogen vapor pressure [P (1)].
s 0
9.8 Close the S valve and close the EV valve; then admit nitrogen gas to increase the pressure by 100 to 200 torr, depending
upon surface area. Record the pressure as P (2), the manifold temperature as T 8(2), and the extra-volume bulb temperature as T
1 1 1
x8(2).
9.9 Open the S valve to admit the new increment of nitrogen to the catalyst.
9.10 Allow sufficient time for equilibration, readjusting the liquid nitrogen level as necessary. The criterion for equilibrium is
defined in 9.5.
9.11 Record the equilibrium pressure as P (2), and record T 8(2) and T 8(2).
2 2 2x
9.12 Again record T (2) or P (2).
s 0
9.13 Repeat Steps 9.8-9.12 until there are at least four points in the linear BET range.
...
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