ASTM D4780-12(2017)e1
(Test Method)Standard Test Method for Determination of Low Surface Area of Catalysts and Catalyst Carriers by Multipoint Krypton Adsorption
Standard Test Method for Determination of Low Surface Area of Catalysts and Catalyst Carriers by Multipoint Krypton Adsorption
SIGNIFICANCE AND USE
5.1 This test method has been found useful for the determination of the specific surface area of catalysts and catalyst carriers in the range from 0.05 to 10 m2/g for materials specification, manufacturing control, and research and development in the evaluation of catalysts. The determination of surface area of catalysts and catalyst carriers above 10 m2/g is addressed in Test Method D3663.
SCOPE
1.1 This test method covers the determination of the specific surface area of catalysts and catalyst carriers in the range from 0.05 to 10 m2/g. A volumetric measuring system is used to obtain at least three data points which fall within the linear BET region.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
´1
Designation: D4780 − 12 (Reapproved 2017)
Standard Test Method for
Determination of Low Surface Area of Catalysts and
Catalyst Carriers by Multipoint Krypton Adsorption
This standard is issued under the fixed designation D4780; 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.
ε NOTE—Subsesction 8.1 was corrected editorially in February 2017.
1. Scope
P = initial helium pressure, torr.
1.1 Thistestmethodcoversthedeterminationofthespecific
H1
P = helium pressure after equilibration, torr.
H2
surface area of catalysts and catalyst carriers in the range from
T = temperature of manifold at initial helium
H1
0.05 to 10 m /g. A volumetric measuring system is used to
pressure, °C.
obtainatleastthreedatapointswhichfallwithinthelinearBET
T = temperature of manifold after equilibration, °C.
H2
region.
P = initial Kr pressure, torr.
1.2 The values stated in SI units are to be regarded as
T' = manifold temperature at initial Kr pressure, K.
standard. No other units of measurement are included in this
T = manifold temperature at initial Kr pressure, °C.
standard. P = Kr pressure after equilibration, torr.
T' = manifold temperature at P,K.
2 2
1.3 This standard does not purport to address all of the
T = manifold temperature at P , °C.
2 2
safety concerns, if any, associated with its use. It is the
P = liquid nitrogen vapor pressure, torr.
o,N
responsibility of the user of this standard to establish appro-
P = calculated krypton vapor pressure, torr.
o,krypton
priate safety and health practices and determine the applica-
T' = liquid nitrogen temperature, K.
s
bility of regulatory limitations prior to use.
X = relative pressure, P /P .
2 o,krypton
V = volume of manifold, cm .
d
2. Referenced Documents
V = the apparent dead-space volume, cm .
s
W = weight of sample, g.
2.1 ASTM Standards:
s
W = tare weight of sample tube, g.
D3663Test Method for Surface Area of Catalysts and 1
W = weight of sample plus tare weight of tube, g.
Catalyst Carriers
V = volume of krypton in the dead space, cm.
ds
D3766Terminology Relating to Catalysts and Catalysis
V = See 11.3.5.
E177Practice for Use of the Terms Precision and Bias in
V = See 11.3.6.
ASTM Test Methods
V = See 11.3.7.
t
E456Terminology Relating to Quality and Statistics
V = See 11.3.9.
a
E691Practice for Conducting an Interlaboratory Study to
V = See 11.6.
m
Determine the Precision of a Test Method
4. Summary of Test Method
3. Terminology
4.1 A catalyst or catalyst carrier sample is degassed by
3.1 Definitions—Consult Terminology D3766.
heating in vacuum to remove absorbed vapors from the
surface. The quantity of krypton adsorbed at various low
3.2 Symbols:
pressure levels is determined by measuring pressure differen-
tials after introduction of a fixed volume of krypton to the
1 sampleatliquidnitrogentemperature.Thespecificsurfacearea
This test method is under the jurisdiction of ASTM Committee D32 on
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical- is then calculated from the sample weight and adsorption data
Chemical Properties.
using the BET equation.
Current edition approved Feb. 1, 2017. Published February 2017. Originally
approved in 1988. Last previous edition approved in 2012 as D4780–12). DOI:
5. Significance and Use
10.1520/D4780-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 This test method has been found useful for the determi-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
nation of the specific surface area of catalysts and catalyst
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. carriers in the range from 0.05 to 10 m /g for materials
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D4780 − 12 (2017)
−7
specification, manufacturing control, and research and devel- 6.1.10 Laboratory Balance with 0.1 mg (10 kg) sensitiv-
opment in the evaluation of catalysts. The determination of ity.
surface area of catalysts and catalyst carriers above 10 m /g is 6.1.11 Thermometer for measuring the temperature of the
addressed in Test Method D3663. liquid nitrogen bath (T' (i)) in kelvins. This will preferably be
s
a nitrogen vapor-pressure-thermometer that gives P directly
o,N
6. Apparatus
and has greater precision, or a resistance thermometer from
which P values may be derived.
o,N
6.1 AschematicdiagramoftheapparatusisshowninFig.1.
It may be constructed of glass or of metal and may operate
7. Reagents
manually or automatically. It has the following features:
7.1 Purity of Reagents—Reagent grade chemicals shall be
6.1.1 Vacuum System, capable of attaining pressures below
-4
used in all tests. Unless otherwise indicated, it is intended that
10 torr (1 torr=133.3 Pa). This will include a vacuum gage
all reagents shall conform to the specifications of the Commit-
(not shown in Fig. 1). Access to the distribution manifold is
tee onAnalytical Reagents of theAmerican Chemical Society,
through the valve V.
where such specifications are available. Other grades may be
6.1.2 Distribution Manifold, having a volume between 5
3 3
used, provided it is first ascertained that the reagent is of
and 40 cm (V ) known to the nearest 0.01 cm . This volume
d
sufficiently high purity to permit its use without lessening the
is defined as the volume between the stopcocks or valves and
accuracy of the determination.
it includes the volume within the pressure gage.
6.1.3 Constant Volume Gages,capableofmeasuring1to10
7.2 Helium Gas, at least 99.9% pure.
torr to the nearest 0.001 torr and 0 to 1000 torr to the nearest
7.3 Krypton Gas, at least 99.9% pure.
torr (1 torr=133.3 Pa).
7.4 Liquid Nitrogen, of such purity that the saturation vapor
6.1.4 Valve (H), from the helium supply to the distribution
pressure P is not more than 20 torr above barometric
manifold.
o,N
6.1.5 Valve (K), from the krypton supply to the distribution pressure. A fresh daily supply is recommended.
manifold.
8. Procedure—Sample Preparation and Degassing
6.1.6 Sample Tube(s), with volume between 5 cm and 25
3 3
cm , depending on the application.The sample tube(s) may be 8.1 Select a sample tube of the desired size.A5 cm tube is
connected to the distribution manifold with standard taper
preferred for small samples to minimize dead space. However,
joints, glass-to-glass seals, or compression fittings. larger tubes may be required for larger samples or for finely
powdered samples, to avoid elutriation of the powder when
NOTE 1—Modern commercial instruments may employ simple tubes
degassing is started.
withvolumesoutsideofthisrange,andmaybecapableoftestingmultiple
samples simultaneously rather than separately as stated in 9.1.
8.2 Evacuate the sample tube and then fill to atmospheric
6.1.7 Dewar Flask(s)forimmersionofthesampletube(s)in pressure with helium. This may be done on the surface area
liquidnitrogen.Thenitrogenlevelshouldbefixedataconstant
unit, or on a separate piece of equipment.
height by means of an automatic level controller or manually
8.3 Remove the sample tube, cap, and weigh. Record the
refilledtoapredeterminedmarkonthesampletube(s)about30
weight as W .
to 50 mm below the distribution manifold connectors.
8.4 Place the sample, whose weight is known
6.1.8 Thermometer for measuring the temperature of the
approximately, into the sample tube. If possible, choose the
distribution manifold (T (i)or T (i)) in degrees Celsius.
1 2
sample size to provide an estimated total surface area of 1 to 5
(Alternatively, the distribution manifold may be thermostatted
m .
a few degrees above ambient to obviate the necessity of
recording this temperature.)
8.5 Attachthesampletubetotheapparatus.Ifothersamples
6.1.9 Heating Mantle(s) or Small Furnace(s) for each
are to be run, attach them at this time to the other ports.
sample tube to allow outgassing samples at elevated tempera-
8.6 Open the S valves where there are samples.
tures.
8.7 Slowlyopenthe Vvalve,monitoringtherateofpressure
decreasetoavoidtoohigharate,whichmightleadtoexcessive
fluidization of powdered samples.
8.7.1 If a diffusion pump is used, it may be necessary to
close the V valve 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 each
time.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
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,
FIG. 1 Schematic Diagram of Surface Area Apparatus MD.
´1
D4780 − 12 (2017)
−3
8.8 Install a heating mantle or furnace around each sample 9.10 Close the S valve when a pressure below 10 torr has
andraisethetemperaturetoabout300°C(573K).(Warning— been attained. This should normally take 5 to 10 min.
Take special precautions if the moisture content exceeds
10. Procedure—Krypton Adsorption
approximately 5% to avoid “bumping” of powdered catalyst,
and to avoid surface area loss by self-steaming. It is recom-
10.1 Close the V valve.
mended that the heating rate not exceed 100 K/h under these
10.2 Admit krypton gas by opening the K valve and record
circumstances.)
pressure as P (1) and temperature as T (1). (It is desirable to
1 1
8.9 Continue degassing at about 300°C (573 K) for a
choose P (1) such that P (1)/P (1) is about 0.05.)
1 2 o
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
10.3 Open the S valve to admit krypton to the sample.
Overnight degassing is permissible.
10.4 Allow sufficient time for equilibration, readjusting the
NOTE 2—Certain materials decompose or sinter at 300°C. Lower
liquid nitrogen level periodically if needed. Equilibrium shall
degassing temperatures are permissible for such materials; however, the
be considered as attained when the pressure changes by no
degassing temperature should be specified when reporting the results.
more than 0.001 torr in 5 min.
8.10 Remove the heating mantl
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D4780 − 12 (Reapproved 2017)
Standard Test Method for
Determination of Low Surface Area of Catalysts and
Catalyst Carriers by Multipoint Krypton Adsorption
This standard is issued under the fixed designation D4780; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Subsesction 8.1 was corrected editorially in February 2017.
1. Scope
P = initial helium pressure, torr.
1.1 This test method covers the determination of the specific H1
P = helium pressure after equilibration, torr.
surface area of catalysts and catalyst carriers in the range from H2
2 T = temperature of manifold at initial helium
H1
0.05 to 10 m /g. A volumetric measuring system is used to
pressure, °C.
obtain at least three data points which fall within the linear BET
T = temperature of manifold after equilibration, °C.
H2
region.
P = initial Kr pressure, torr.
1.2 The values stated in SI units are to be regarded as
T' = manifold temperature at initial Kr pressure, K.
standard. No other units of measurement are included in this
T = manifold temperature at initial Kr pressure, °C.
standard. P = Kr pressure after equilibration, torr.
T' = manifold temperature at P , K.
2 2
1.3 This standard does not purport to address all of the
T = manifold temperature at P , °C.
2 2
safety concerns, if any, associated with its use. It is the
P = liquid nitrogen vapor pressure, torr.
o,N
responsibility of the user of this standard to establish appro-
P = calculated krypton vapor pressure, torr.
o,krypton
priate safety and health practices and determine the applica-
T' = liquid nitrogen temperature, K.
s
bility of regulatory limitations prior to use.
X = relative pressure, P /P .
2 o,krypton
V = volume of manifold, cm .
d
2. Referenced Documents
V = the apparent dead-space volume, cm .
s
W = weight of sample, g.
2.1 ASTM Standards: s
W = tare weight of sample tube, g.
D3663 Test Method for Surface Area of Catalysts and 1
W = weight of sample plus tare weight of tube, g.
Catalyst Carriers
V = volume of krypton in the dead space, cm.
ds
D3766 Terminology Relating to Catalysts and Catalysis
V = See 11.3.5.
E177 Practice for Use of the Terms Precision and Bias in
V = See 11.3.6.
ASTM Test Methods
V = See 11.3.7.
t
E456 Terminology Relating to Quality and Statistics
V = See 11.3.9.
a
E691 Practice for Conducting an Interlaboratory Study to
V = See 11.6.
m
Determine the Precision of a Test Method
4. Summary of Test Method
3. Terminology
4.1 A catalyst or catalyst carrier sample is degassed by
3.1 Definitions—Consult Terminology D3766.
heating in vacuum to remove absorbed vapors from the
3.2 Symbols: surface. The quantity of krypton adsorbed at various low
pressure levels is determined by measuring pressure differen-
tials after introduction of a fixed volume of krypton to the
1 sample at liquid nitrogen temperature. The specific surface area
This test method is under the jurisdiction of ASTM Committee D32 on
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical- is then calculated from the sample weight and adsorption data
Chemical Properties.
using the BET equation.
Current edition approved Feb. 1, 2017. Published February 2017. Originally
approved in 1988. Last previous edition approved in 2012 as D4780–12). DOI:
5. Significance and Use
10.1520/D4780-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 This test method has been found useful for the determi-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
nation of the specific surface area of catalysts and catalyst
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. carriers in the range from 0.05 to 10 m /g for materials
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D4780 − 12 (2017)
−7
specification, manufacturing control, and research and devel- 6.1.10 Laboratory Balance with 0.1 mg (10 kg) sensitiv-
opment in the evaluation of catalysts. The determination of ity.
surface area of catalysts and catalyst carriers above 10 m /g is 6.1.11 Thermometer for measuring the temperature of the
addressed in Test Method D3663. liquid nitrogen bath (T' (i)) in kelvins. This will preferably be
s
a nitrogen vapor-pressure-thermometer that gives P directly
o,N
6. Apparatus
and has greater precision, or a resistance thermometer from
which P values may be derived.
6.1 A schematic diagram of the apparatus is shown in Fig. 1. o,N
It may be constructed of glass or of metal and may operate
7. Reagents
manually or automatically. It has the following features:
7.1 Purity of Reagents—Reagent grade chemicals shall be
6.1.1 Vacuum System, capable of attaining pressures below
-4
used in all tests. Unless otherwise indicated, it is intended that
10 torr (1 torr = 133.3 Pa). This will include a vacuum gage
all reagents shall conform to the specifications of the Commit-
(not shown in Fig. 1). Access to the distribution manifold is
tee on Analytical Reagents of the American Chemical Society,
through the valve V.
where such specifications are available. Other grades may be
6.1.2 Distribution Manifold, having a volume between 5
3 3
used, provided it is first ascertained that the reagent is of
and 40 cm (V ) known to the nearest 0.01 cm . This volume
d
sufficiently high purity to permit its use without lessening the
is defined as the volume between the stopcocks or valves and
accuracy of the determination.
it includes the volume within the pressure gage.
6.1.3 Constant Volume Gages, capable of measuring 1 to 10
7.2 Helium Gas, at least 99.9 % pure.
torr to the nearest 0.001 torr and 0 to 1000 torr to the nearest
7.3 Krypton Gas, at least 99.9 % pure.
torr (1 torr = 133.3 Pa).
7.4 Liquid Nitrogen, of such purity that the saturation vapor
6.1.4 Valve (H), from the helium supply to the distribution
manifold. pressure P is not more than 20 torr above barometric
o,N
pressure. A fresh daily supply is recommended.
6.1.5 Valve (K), from the krypton supply to the distribution
manifold.
3 8. Procedure—Sample Preparation and Degassing
6.1.6 Sample Tube(s), with volume between 5 cm and 25
cm , depending on the application. The sample tube(s) may be
8.1 Select a sample tube of the desired size. A 5 cm tube is
connected to the distribution manifold with standard taper preferred for small samples to minimize dead space. However,
joints, glass-to-glass seals, or compression fittings.
larger tubes may be required for larger samples or for finely
powdered samples, to avoid elutriation of the powder when
NOTE 1—Modern commercial instruments may employ simple tubes
degassing is started.
with volumes outside of this range, and may be capable of testing multiple
samples simultaneously rather than separately as stated in 9.1.
8.2 Evacuate the sample tube and then fill to atmospheric
6.1.7 Dewar Flask(s) for immersion of the sample tube(s) in
pressure with helium. This may be done on the surface area
liquid nitrogen. The nitrogen level should be fixed at a constant unit, or on a separate piece of equipment.
height by means of an automatic level controller or manually
8.3 Remove the sample tube, cap, and weigh. Record the
refilled to a predetermined mark on the sample tube(s) about 30
weight as W .
to 50 mm below the distribution manifold connectors.
8.4 Place the sample, whose weight is known
6.1.8 Thermometer for measuring the temperature of the
approximately, into the sample tube. If possible, choose the
distribution manifold (T (i) or T (i)) in degrees Celsius.
1 2
sample size to provide an estimated total surface area of 1 to 5
(Alternatively, the distribution manifold may be thermostatted
m .
a few degrees above ambient to obviate the necessity of
recording this temperature.)
8.5 Attach the sample tube to the apparatus. If other samples
6.1.9 Heating Mantle(s) or Small Furnace(s) for each
are to be run, attach them at this time to the other ports.
sample tube to allow outgassing samples at elevated tempera-
8.6 Open the S valves where there are samples.
tures.
8.7 Slowly open the V valve, monitoring the rate of pressure
decrease to avoid too high a rate, which might lead to excessive
fluidization of powdered samples.
8.7.1 If a diffusion pump is used, it may be necessary to
close the V valve 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 each
time.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
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,
FIG. 1 Schematic Diagram of Surface Area Apparatus MD.
´1
D4780 − 12 (2017)
−3
8.8 Install a heating mantle or furnace around each sample 9.10 Close the S valve when a pressure below 10 torr has
and raise the temperature to about 300°C (573 K). (Warning— been attained. This should normally take 5 to 10 min.
Take special precautions if the moisture content exceeds
10. Procedure—Krypton Adsorption
approximately 5 % to avoid “bumping” of powdered catalyst,
and to avoid surface area loss by self-steaming. It is recom-
10.1 Close the V valve.
mended that the heating rate not exceed 100 K/h under these
10.2 Admit krypton gas by opening the K valve and record
circumstances.)
pressure as P (1) and temperature as T (1). (It is desirable to
1 1
8.9 Continue degassing at about 300°C (573 K) for a
choose P (1) such that P (1)/P (1) is about 0.05.)
1 2 o
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
10.3 Open the S valve to admit krypton to the sample.
Overnight degassing is permissible.
10.4 Allow sufficient time for equilibration, readjusting the
NOTE 2—Certain materials decompose or sinter at 300°C. Lower
liquid nitrogen level periodically if needed. Equilibrium shall
degassing temperatures are permissible for such materials; however, the
be considered as attained when the pressure changes by no
degassing temperature should be specified when reporting the results.
more than 0.001 torr in 5 min.
8.10 Remove the heating mantles, and allow the samples to
10.5 Record the equilibrium pressure, P (1), and manifold
cool.
temperature, T (1).
8.11 Close
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM 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.
´1
Designation: D4780 − 12 D4780 − 12 (Reapproved 2017)
Standard Test Method for
Determination of Low Surface Area of Catalysts and
Catalyst Carriers by Multipoint Krypton Adsorption
This standard is issued under the fixed designation D4780; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Subsesction 8.1 was corrected editorially in February 2017.
1. Scope
1.1 This test method covers the determination of the specific surface area of catalysts and catalyst carriers in the range from 0.05
to 10 m /g. A volumetric measuring system is used to obtain at least three data points which fall within the linear BET region.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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:
D3663 Test Method for Surface Area of Catalysts and Catalyst Carriers
D3766 Terminology Relating to Catalysts and Catalysis
E177 Practice for Use of the Terms Precision 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 Definitions—Consult Terminology D3766.
3.2 Symbols:
P = initial helium pressure, torr.
H1
P = helium pressure after equilibration, torr.
H2
T = temperature of manifold at initial helium pressure, °C.
H1
T = temperature of manifold after equilibration, °C.
H2
P = initial Kr pressure, torr.
T' = manifold temperature at initial Kr pressure, K.
T = manifold temperature at initial Kr pressure, °C.
P = Kr pressure after equilibration, torr.
T' = manifold temperature at P , K.
2 2
T = manifold temperature at P , °C.
2 2
P = liquid nitrogen vapor pressure, torr.
o,N
P = calculated krypton vapor pressure, torr.
o,krypton
T' = liquid nitrogen temperature, K.
s
X = relative pressure, P /P .
2 o,krypton
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 May 1, 2012Feb. 1, 2017. Published July 2012February 2017. Originally approved in 1988. Last previous edition approved in 20072012 as
D4780–95(2007).D4780–12). DOI: 10.1520/D4780-12.10.1520/D4780-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D4780 − 12 (2017)
V = volume of manifold, cm .
d
V = the apparent dead-space volume, cm .
s
W = weight of sample, g.
s
W = tare weight of sample tube, g.
W = weight of sample plus tare weight of tube, g.
V = volume of krypton in the dead space, cm.
ds
V = See 11.3.5.
V = See 11.3.6.
V = See 11.3.7.
t
V = See 11.3.9.
a
V = See 11.6.
m
4. Summary of Test Method
4.1 A catalyst or catalyst carrier sample is degassed by heating in vacuum to remove absorbed vapors from the surface. The
quantity of krypton adsorbed at various low pressure levels is determined by measuring pressure differentials after introduction of
a fixed volume of krypton to the sample at liquid nitrogen temperature. The specific surface area is then calculated from the sample
weight and adsorption data using the BET equation.
5. Significance and Use
5.1 This test method has been found useful for the determination of the specific surface area of catalysts and catalyst carriers
in the range from 0.05 to 10 m /g for materials specification, manufacturing control, and research and development in the
evaluation of catalysts. The determination of surface area of catalysts and catalyst carriers above 10 m /g is addressed in Test
Method D3663.
6. Apparatus
6.1 A schematic diagram of the apparatus is shown in Fig. 1. It may be constructed of glass or of metal and may operate
manually or automatically. It has the following features:
-4
6.1.1 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.
3 3
6.1.2 Distribution Manifold, having a volume between 5 and 40 cm (V ) known to the nearest 0.01 cm . This volume is defined
d
as the volume between the stopcocks or valves and it includes the volume within the pressure gage.
6.1.3 Constant Volume Gages, capable of measuring 1 to 10 torr to the nearest 0.001 torr and 0 to 1000 torr to the nearest torr
(1 torr = 133.3 Pa).
6.1.4 Valve (H), from the helium supply to the distribution manifold.
6.1.5 Valve (K), from the krypton supply to the distribution manifold.
3 3
6.1.6 Sample Tube(s), with volume between 5 cm and 25 cm , depending on the application. The sample tube(s) may be
connected to the distribution manifold with standard taper joints, glass-to-glass seals, or compression fittings.
NOTE 1—Modern commercial instruments may employ simple tubes with volumes outside of this range, and may be capable of testing multiple samples
simultaneously rather than separately as stated in 9.1.
6.1.7 Dewar Flask(s) for immersion of the sample tube(s) in liquid nitrogen. The nitrogen level should be fixed at a constant
height by means of an automatic level controller or manually refilled to a predetermined mark on the sample tube(s) about 30 to
50 mm below the distribution manifold connectors.
6.1.8 Thermometer for measuring the temperature of the distribution manifold (T (i) or T (i)) in degrees Celsius. (Alternatively,
1 2
the distribution manifold may be thermostatted a few degrees above ambient to obviate the necessity of recording this temperature.)
6.1.9 Heating Mantle(s) or Small Furnace(s) for each sample tube to allow outgassing samples at elevated temperatures.
FIG. 1 Schematic Diagram of Surface Area Apparatus
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D4780 − 12 (2017)
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6.1.10 Laboratory Balance with 0.1 mg (10 kg) sensitivity.
6.1.11 Thermometer for measuring the temperature of the liquid nitrogen bath (T' (i)) in kelvins. This will preferably be a
s
nitrogen vapor-pressure-thermometer that gives P directly and has greater precision, or a resistance thermometer from which
o,N
P values may be derived.
o,N
7. Reagents
7.1 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.
7.2 Helium Gas, at least 99.9 % pure.
7.3 Krypton Gas, at least 99.9 % pure.
7.4 Liquid Nitrogen, of such purity that the saturation vapor pressure P is not more than 20 torr above barometric pressure.
o,N
A fresh daily supply is recommended.
8. Procedure—Sample Preparation and Degassing
8.1 Select a sample tube of the desired size. A 5 cm tube is preferred for small samples to minimize dead space. However, larger
tubes may be required for larger samples or for finely powdered samples, to avoid percolationelutriation of the powder when
degassing is started.
8.2 Evacuate the sample tube and then fill to atmospheric pressure with helium. This may be done on the surface area unit, or
on a separate piece of equipment.
8.3 Remove the sample tube, cap, and weigh. Record the weight as W .
8.4 Place the sample, whose weight is known approximately, into the sample tube. If possible, choose the sample size to provide
an estimated total surface area of 1 to 5 m .
8.5 Attach the sample tube to the apparatus. If other samples are 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 of pressure decrease to avoid too high a rate, which might lead to excessive
fluidization of powdered samples.
8.7.1 If a diffusion pump is used, it may be necessary to close the V valve 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 each time.
8.8 Install a heating mantle or furnace around each sample and raise the temperature to about 300°C (573 K). (Warning—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 100 K/h under these circumstances.)
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8.9 Continue degassing at about 300°C (573 K) for a minimum of 3 h, at a pressure not to exceed 10 torr. Overnight degassing
is permissible.
NOTE 2—Certain materials decompose or sinter at 300°C. Lower degassing temperatures are permissible for such materials; however, the degassing
temperature should be specified when reporting the results.
8.10 Remove the heating mantles, and allow the samples to cool.
8.11 Close the S valves.
8.12 It is permissible to exercise the option of preliminary degassing on an external unit. In such a case, follow the procedures
of 8.4 – 8.11 and then repeat on the adsorption unit, except that the degassing on the adsorption unit can be at room temperature
and need not exceed 1 h.
8.13 If it is desired to weigh the sample after preliminary degassing on an external unit, backfill with helium to slightly above
atmospheric pressure. Close the S valve.
8.13.1 Detach the sample tube from the apparatus, recap with the stopper used previously, and weigh. Record the weight as W .
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8.13.2 Reattach the sample tube to the apparatus. Remove the backfilled gas by evacuation to less than 10 torr at room
temperature. This should normally take 5 to 10 min.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed by
the American Chemical Society, see Annual Standards for Lab
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