ASTM D3663-99
(Test Method)Standard Test Method for Surface Area of Catalysts and Catalyst Carriers
Standard Test Method for Surface Area of Catalysts and Catalyst Carriers
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. A volumetric measuring system is used to obtain at least four data points which fit on the linear BET line.
1.2 This standard does not purport to address all of the safety problems, 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: D 3663 – 99
Standard Test Method for
Surface Area of Catalysts and Catalyst Carriers
This standard is issued under the fixed designation D 3663; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope
T 8 5 manifold temperature at initial N pressure, °C
1 2
P 5 pressure after equilibration, torr
1.1 This test method covers the determination of surface 2
P 5 liquid nitrogen vapor pressure, torr
areas of catalyst and catalyst carriers that have Type II or IV 0
T 5 liquid nitrogen temperature, K
s
nitrogen adsorption isotherms, and at least 1 m /g of area. A
X 5 relative pressure, P /P
2 0
volumetric measuring system is used to obtain at least four data
V 5 volume of manifold, cm
d
points which fit on the linear BET line.
V 5 extra volume bulb, cm
x
1.2 This standard does not purport to address all of the
V 5 dead-space volume, cm
s
safety concerns, if any, associated with its use. It is the
W 5 weight of sample, g
s
responsibility of the user of this standard to establish appro-
W 5 tare weight of sample tube, g
priate safety and health practices and determine the applica-
W 5 sample + tare weight of tube, g
bility of regulatory limitations prior to use.
V 5 volume of nitrogen in the dead-space, cm
ds
V 5 see 10.4.4
2. Referenced Documents
V 5 see 10.4.6
2.1 ASTM Standards: V 5 see 10.4.7
t
D 3766 Terminology Relating to Catalysts and Catalysis V 5 see 10.4.9
a
V 5 see 10.8
E 177 Practice for Use of the Terms Precisions and Bias in
m
T 5 initial extra-volume bulb temperature, K
ASTM Test Methods
1x
T 8(i) 5 initial extra-volume bulb temperature, °C
E 456 Terminology Relating to Quality and Statistics 1x
T 5 extra-volume bulb temperature after equilib-
2x
E 691 Practice for Conducting an Interlaboratory Study to
4 rium, K
Determine the Precision of a Test Method
T 8(i) 5 extra-volume bulb temperature after equilib-
2x
3. Terminology rium, °C
3.1 Consult Terminology D 3766 for definitions of other
4. Summary of Method
terms used.
4.1 The surface area of a catalyst or catalyst carrier is
3.2 Definition:
determined by measuring the volume of nitrogen gas adsorbed
3.2.1 surface area of a catalyst—the total surface of the
at various low-pressure levels by the catalyst sample. Pressure
catalyst. It is expressed in square metres per gram.
differentials caused by introducing the catalyst surface area to
3.3 Symbols:
a fixed volume of nitrogen in the test apparatus are measured
and used to calculate BET surface area.
P 5 initial helium pressure, torr
H
5. Apparatus
P 5 helium pressure after equilibration, torr
H
T 5 temperature of manifold at initial helium pres-
5.1 A schematic diagram of the apparatus is shown in Fig. 1.
H
sure, °C
It may be constructed of glass or of metal. It has the following
T 5 temperature of manifold after equilibration,° C
H features:
P 5 initial N pressure, torr
1 2
5.1.1 Distribution Manifold, having a volume between 20
T 5 manifold temperature at initial N pressure, K 3 3
1 2
and 35 cm ,( V ), known to the nearest 0.05 cm . This volume
d
is defined as the volume between the stopcocks or valves and
includes the pressure gage.
This test method is under the jurisdiction of ASTM Committee D-32 on
5.1.2 Vacuum System, capable of attaining pressures below
−4
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
10 torr (1 torr 5 133.3 Pa). This will include a vacuum gage
Chemical Properties.
(not shown in Fig. 1). Access to the distribution manifold is
Current edition approved Oct. 10, 1999. Published December 1999. Originally
e1
published as D 3663 – 78. Last previous edition D 3663 – 92 (1999) .
through the valve V.
Brunauer, Emmett, Teller, Journal of American Chemical Society, JACS, No.
60, 1938, p. 309.
Annual Book of ASTM Standards, Vol 05.03.
4 5
Annual Book of ASTM Standards, Vol 14.02. Automated equipment is commercially available.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3663
FIG. 1 Schematic Diagram of Surface Area Apparatus
5.1.3 Constant-Volume Gage or Mercury Manometer, ca- sufficiently high purity to permit its use without lessening the
pable of measurements to the nearest 0.1 torr, in the range from accuracy of the determination.
0 to 1000 torr (1 torr 5 133.3 Pa). 6.2 Helium Gas—A cylinder of helium gas at least 99.9 %
pure.
NOTE 1—See, for example, the article by Joy, A. S., Vacuum, Vol 3,
6.3 Liquid Nitrogen, of such purity that P is not more than
1953, p. 254, for a description of a constant-volume manometer.
20 torr above barometric pressure. A fresh daily supply is
5.1.4 Valve (H), from the helium supply to the distribution
recommended.
manifold.
6.4 Nitrogen Gas—A cylinder of nitrogen gas at least
5.1.5 Valve (N), from the nitrogen supply to the distribution
99.9 % pure.
manifold.
5.1.6 The connection between the sample tube and the S
7. Procedure—Sample Preparation and Degassing
valve can be a standard-taper glass joint, a glass-to-glass seal,
7.1 Select a sample tube of the desired size. A5-cm sample
or a compression fitting.
tube is preferred for samples not exceeding about 1 g, to
5.1.7 Extra Volume Bulb,(V ), should be 100 to 150 cm ,
x
3 minimize the dead-space. However, a 25-cm sample tube may
known to the nearest 0.05 cm . V includes the volume of the
x
be preferred for finely powdered catalysts, to avoid “boiling”
stopcock bore in the glass apparatus.
3 when degassing is started.
5.2 Sample Tubes, with volumes from 5 to 25 cm depend-
7.2 Fill the sample tube with nitrogen or helium, at atmo-
ing on the application. Markings should be placed on the
spheric pressure, after removing air by evacuation. This may be
sample tubes about 30 to 50 mm below the connectors to
done on the surface area unit, or on a separate piece of
indicate the desired liquid nitrogen level.
equipment.
5.3 Heating Mantles or Small Furnaces.
7.3 Remove the sample tube from the system, cap, and
5.4 Dewar Flasks.
−7
weigh. Record the weight as W .
5.5 Laboratory Balance, with 0.1-mg (10 -kg) sensitivity.
7.4 Place the catalyst sample, whose weight is known
5.6 Thermometer, for measuring the temperature of the
approximately, into the sample tube. Choose the sample size to
distribution manifold [ T 8 (i)or T 8 (i)] in degrees Celsius.
1 2
provide an estimated total sample surface area of 20 to 100 m .
5.6.1 It is preferred that the manifold be thermostated at a
7.5 Attach the sample tube to the apparatus. If other samples
particular temperature, a few degrees above ambient, to obviate
are to be run, attach them at this time to the other ports.
the necessity of recording this temperature at each reading.
7.6 Open the S valves where there are samples.
5.7 Thermometer, for measuring the temperature of the
7.7 It may be necessary to close the V valve system
liquid nitrogen bath [ T (i)] in kelvins. This will preferably be
s
periodically to protect the diffusion pump fluid from exposure
a nitrogen vapor-pressure thermometer from which P values
to pressures above 0.1 torr for periods of more than 30 s. Close
may be derived.
the valve off for 2 min.
6. Reagents 7.8 Install a heating mantle or furnace around each sample
and raise the temperature to about 300°C (573 K).
6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
NOTE 2—Take special precautions if the moisture content exceeds
all reagents shall conform to the specifications of the Commit- approximately 5 % to avoid “bumping” of powdered catalyst, and to avoid
surface area loss by self-steaming. It is recommended that the heating rate
tee on Analytical Reagents of the American Chemical Society,
not exceed 100 K/h under these circumstances.
where such specifications are available. Other grades may be
used, provided it is first ascertained that the reagent is of
7.9 Continue degassing at about 300°C (573 K) for a
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
Overnight degassing is permissible.
Reagent Chemicals, American Chemical Society Specifications, Am. Chemical
NOTE 3—Certain materials will decompose at 300°C (for example,
Soc., Washington, DC. For suggestions on the testing of reagents not listed by the
alumina hydrates) or will sinter (for example, platinum black). Lower
American Chemical Society, see Analar Standards for Laboratory Chemicals,”
degassing temperatures are permissible for such materials; however, the
BDH Ltd., Poole, Dorset, U. K. and the United States Pharmacopeia and National
Formulary, U. S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD. degassing temperature should be specified when reporting the results.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3663
7.10 Remove the heating mantles, and allow the samples to 9.5 Allow sufficient time for equilibration, readjusting the
cool. liquid nitrogen level when necessary. Equilibrium shall be
7.11 Close the EV valve, if open. considered as attained when the pressure change is no more
7.12 Close the S valve. than 0.1 torr in 5 min.
7.13 It is permissible to exercise the option of preliminary 9.6 Record the equilibrium pressure as P (1), manifold
degassing on an external unit. In such a case, follow the temperature T 8 (1), and the extra volume bulb temperature T
procedures of 7.4-7.11 and then repeat on the surface area unit, 2 (1).
x
except that the degassing time in 7.9 should not exceed 1 h. 9.7 Record the liquid nitrogen temperature [ T (1)] or the
s
7.14 If it is desired to weigh the sample after preliminary nitrogen vapor pressure [P (1)].
degassing on an external unit, backfill with the same gas used 9.8 Close the S valve and close the EV valve; then admit
in 7.2 to above atmospheric pressure. Close the S valve. nitrogen gas to increase the pressure by 100 to 200 torr,
7.15 Detach the sample tube from the apparatus, recap with depending upon surface area. Record the pressure as P (2), the
the stop
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