ASTM D4365-95
(Test Method)Standard Test Method for Determining Micropore Volume and Zeolite Area of a Catalyst
Standard Test Method for Determining Micropore Volume and Zeolite Area of a Catalyst
SCOPE
1.1 This test method covers the determination of total surface area and mesopore area. From these results are calculated the zeolite area and micropore volume of a zeolite containing catalyst. The micropore volume is related to the percent zeolite in the catalyst. The zeolite area, a number related to the surface area within the zeolite pores, may also be calculated. Zeolite area, however, is difficult to intepret in physical terms because of the manner in which nitrogen molecules pack within the zeolite.
1.2 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. For specific precautionary statement, see Note 2.
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Designation: D 4365 – 95
Standard Test Method for
Determining Micropore Volume and Zeolite Area of a
Catalyst
This standard is issued under the fixed designation D 4365; 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 catalyst pores. It is expressed in square metres per gram.
3.1.4 zeolite area of a catalyst—the difference between total
1.1 This test method covers the determination of total
surface area and mesopore area.
surface area and mesopore area. From these results are calcu-
3.2 Symbols:
lated the zeolite area and micropore volume of a zeolite
containing catalyst. The micropore volume is related to the
percent zeolite in the catalyst. The zeolite area, a number
P 5 initial helium pressure, torr
H
related to the surface area within the zeolite pores, may also be
P 5 helium pressure after equilibration, torr
H
calculated. Zeolite area, however, is difficult to intepret in
S 5 slope of BET plot, 11.7
B
physical terms because of the manner in which nitrogen
I 5 intercept of BET plot, 11.7
B
molecules pack within the zeolite.
S 5 slope of t-plot, 11.13
t
1.2 This standard does not purport to address all of the I 5 intercept of t-plot, 11.13
t
safety concerns, if any, associated with its use. It is the T 5 temperature of manifold at initial helium pres-
H1
responsibility of the user of this standard to establish appro- sure, °C
T 5 temperature of manifold after equilibration, °C
priate safety and health practices and determine the applica-
H2
T 8(i) 5 extra volume bulb temperature, °C
bility of regulatory limitations prior to use. For specific
x
T (i) 5 extra volume bulb temperature, K
precautionary statement, see Note 2. x
P 5 initial N pressure, torr
1 2
2. Referenced Documents T 5 manifold temperature at initial N pressure, K
1 2
T 8 5 manifold temperature at initial N pressure,° C
1 2
2.1 ASTM Standards:
P 5 pressure after equilibration, torr
D 3663 Test Method for Surface Area of Catalysts
T 5 manifold temperature after equilibration, K
D 3906 Test Method for Relative Zeolite Diffraction Inten-
T 8 5 manifold temperature after equilibration, °C
sities
P 5 liquid nitrogen vapor pressure, torr
E 177 Practice for Use of the Terms Precision and Bias in
T 5 liquid nitrogen temperature, K
s
ASTM Test Methods
X 5 relative pressure, P /P
2 0
E 456 Terminology Relating to Quality and Statistics
V 5 volume of manifold, cm
d
E 691 Practice for Conducting an Interlaboratory Study to
V 5 extra volume bulb, cm
x
3 3
Determine the Precision of a Test Method V 5 effective void volume, cm
s
W 5 weight of sample, g
3. Terminology
W 5 tare weight of sample tube, g
W 5 weight of sample + tare weight of tube, g
3.1 Definitions of Terms Specific to This Standard:
V 5 volume of nitrogen in the dead-space, cm
3.1.1 mesopore area of a catalyst—the area determined ds
V 5 see 11.4.3
from the slope of the t-plot.
V 5 see 11.4.4
3.1.2 micropore volume of the catalyst—the pore volume in
V 5 see 11.4.5
t
pores having radii less than 1 nm, usually associated with the
V 5 see 11.4.7
a
zeolite portion of the catalyst, and determined from the
V 5 see 11.8
m
intercept of the t-plot.
BET (i) 5 see 11.4.8
3.1.3 surface area of a catalyst—the total surface of the
t(i) 5 see 11.10
4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D-32 on
4.1 The volume of nitrogen gas adsorbed by the catalyst at
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
Chemical Properties.
liquid nitrogen temperature is measured at various low-
Current edition approved Aug. 15, 1995. Published October 1995. Originally
pressure levels. This is done by measuring pressure differen-
e1
published as D 4365 – 84. Last previous edition D 4365 – 85 (1994) .
tials caused by introducing a fixed volume of nitrogen to the
Annual Book of ASTM Standards, Vol 05.03.
Annual Book of ASTM Standards, Vol 14.02. degassed catalyst in the test apparatus. This procedure is the
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 4365
NOTE 2—Modern commercial instruments automatically adjust the
same as Test Method D 3663, that gives total surface area, but
amounts dosed in order to produce data points at user-selected target
extends the pressure range to permit calculation of micropore
pressures. Hence, the use of an EV bulb is optional. Some instruments can
volume and matrix surface area, by the t-plot method. Zeolite
analyze multiple samples simultaneously and may use sample tubes with
area is the difference between total area and matrix area.
volumes outside of the range specified in this test method.
3 3
5. Significance and Use
6.2 Sample Tubes, with volumes from 5 cm to 25 cm
depending on the application. Markings should be placed on
5.1 This gas adsorption method complements the X-ray
the sample tubes about 30 to 50 mm below the connectors to
procedure of Test Method D 3906. This test method will be
indicate the desired liquid nitrogen level.
useful to laboratories that do not have X-ray diffractometers.
6.3 Heating Mantles or Small Furnaces.
Each test method can be calibrated by use of an appropriate
6.4 Dewar Flasks.
series of mechanical mixtures to provide what may be termed
−7
6.5 Laboratory Balance, with 0.1 mg (10 kg) sensitivity.
percent zeolite. If there is disorder in the zeolite, the adsorption
6.6 Thermometer, for measuring the temperature of the
method will yield higher values than the X-ray method. The
distribution manifold, T 8(i)or T 8(i), in degrees Celsius.
reverse will be true if some zeolite pores (micropores) are 1 2
6.7 Thermometer, for measuring the temperature of the
blocked or filled.
liquid nitrogen bath T (i) in kelvins. This will preferably be a
s
6. Apparatus
nitrogen vapor-pressure-thermometer that gives P directly and
has greater precision, or a resistance thermometer from which
6.1 A schematic diagram of the apparatus is shown in Fig. 1.
It may be constructed of glass or of metal. It has the following P values may be derived.
6.8 Thermometer, for measuring the temperature of the EV
features:
bulb, T 8(i), if different from T 8(i)or T 8(i).
6.1.1 Distribution Manifold, having a volume between 20
x 1 2
3 3
and 35 cm ,(V ), known to the nearest 0.05 cm . This volume
d
7. Reagents
is defined as the volume between the stopcocks or valves and
7.1 Purity of Reagents—Reagent grade chemicals shall be
includes the pressure gage. It is preferred that this volume be
used in all tests. Unless otherwise indicated, it is intended that
thermostatted.
all reagents shall conform to the specifications of the Commit-
6.1.2 Vacuum System, capable of attaining pressures below
−4 tee on Analytical Reagents of the American Chemical Society,
10 torr (1 torr 5 133.3 Pa). This will include a vacuum gage
where such specifications are available. Other grades may be
(not shown in Fig. 1). Access to the distribution manifold is
used, provided it is first ascertained that the reagent is of
through the valve V.
sufficiently high purity to permit its use without lessening the
6.1.3 Constant-Volume Gage or Mercury Manometer, ca-
accuracy of the determination.
pable of measurements to the nearest 0.1-torr sensitivity in the
7.2 Helium Gas—A cylinder of helium gas at least 99.9 %
range from 0 to 1000 torr (1 torr 5 133.3 Pa).
pure.
NOTE 1—See, for example, the article by Joy, A. S., Vacuum, Vol 3,
7.3 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
6.1.4 Valve (H), from the helium supply to the distribution
recommended.
manifold.
7.4 Nitrogen Gas—A cylinder of nitrogen gas at least
6.1.5 Value (N), from the nitrogen supply to the distribution
99.9 % pure.
manifold.
8. Procedure—Sample Preparation and Degassing
6.1.6 The connection between the sample tube and the S
8.1 Select a sample tube of the desired size. A 5-cm sample
valve can be a standard-taper glass joint, a glass-to-glass seal,
or a compression fitting.
6.1.7 Extra Volume Bulb, may be attached through valve
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
EV. Its volume (V ) should be 100 to 150 cm , known to the
x
3 listed by the American Chemical Society, see Analar Standards for Laboratory
nearest 0.05 cm . V includes the volume of the stopcock bore
x
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
in the glass apparatus. It is preferred that this volume be held
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
at the same temperature as that of the distribution manifold. MD.
FIG. 1 Schematic Diagram of Surface Area Apparatus
D 4365
tube is preferred for samples not exceeding about 1 g, to 9.2 The “dead-space” is the void volume of the charged
minimize the dead-space. However, a 25-cm sample tube may sample tube, including the volume within the S valve, when the
be preferred for finely powdered catalysts, to avoid “boiling” tube is immersed in liquid nitrogen to the proper depth.
when degassing is started.
NOTE 5—The dead-space may be determined after the nitrogen adsorp-
8.2 Fill the sample tube with nitrogen or helium, at atmo-
tion, if more convenient, so long as adequate degassing precedes its
spheric pressure, after removing air by evacuation. This may be
determination. In that case, replace the liquid nitrogen bath after 10.14
done on the surface area unit, or on a separate piece of
before proceeding with 9.3-9.9. Then, remove the Dewar flask before
carrying out 10.15-10.17.
equipment.
8.3 Remove the sample tube from the system, cap, and
9.3 Place a Dewar flask of liquid nitrogen around the sample
weigh. Record the weight as W .
and adjust the liquid level to a fixed point on the sample tube.
8.4 Place the catalyst sample, whose weight is known
Maintain this level throughout the test.
approximately, into the sample tube. Choose the sample size to
9.4 Zero the pressure gage.
provide an estimated total sample surface area of 20 to 100 m .
9.5 Admit the helium gas into the system to a pressure of
8.5 Attach the sample tube to the apparatus. If other samples
600 to 900 torr by carefully opening the H valve. Record this
are to be run, attach them at this time to the other ports.
pressure, P , and the manifold temperature, T .
H H
1 1
8.6 Open the S valves where there are samples.
9.6 Open the S valve to admit helium to the sample.
8.7 Slowly open the V valve, monitoring the rate of pressure
9.7 After about 5 min of equilibration, readjust the liquid
decrease to avoid too high a rate, which might lead to excessive
nitrogen level, and record the pressure, P , and the manifold
H
fluidization of powdered samples.
temperature, T .
H
8.7.1 It may be necessary to close the V valve system
9.8 Repeat 9.5-9.7 for each sample cell attached to the
periodically to protect the diffusion pump fluid from exposure
manifold.
to pressures above 0.1 torr for periods of more than 30 s. Close
9.9 Open all S valves; then slowly open the V valve to
the valve off for 2 min.
remove the helium gas.
8.8 Install a heating mantle or furnace around each sample
9.10 When a pressure less than 0.01 torr has been attained,
and raise the temperature to about 300°C (573 K).
close the S valve. This operation should take 5 to 10 min.
NOTE 3—Take special precautions if the moisture content exceeds
approximately 5 % to avoid “bumping” of powdered catalyst, and to avoid
10. Procedure—Nitrogen Adsorption
surface area loss by self-steaming. It is recommended that the heating rate
10.1 Close the V valve and open the EV valve. (The extra
not exceed 100°C(K)/h under these circumstances.
volume bulb should be thermostatted at a particular tempera-
8.9 Continue degassing at about 300°C (573 K) for a
ture, a few degrees above ambient.)
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
10.2 Recheck the zero setting of the pressure gage.
Overnight degassing is permissible.
10.3 Admit nitrogen gas, and record the pressure as P (1)
(torr) and the temperature as T 8 (1) (degrees Celsius). It is
NOTE 4—Zeolite-containing catalysts may contain large quantities of
water. Pretreatment of the sample in an oven at 400°C in flowing nitrogen desirable, but not necessary, to choose P (1) such that the first
for a couple of hours may be desirable.
equilibrium adsorption pressure, P (1) will be about 8 to 15
torr, or P (1)/P of about 0.01 to 0.02. Record T 8(1). Close the
8.10 Remove the heating mantles, and allow the samples to
2 0 x
EV valve.
cool.
10.4 Open the S valve to admit nitrogen to the catalyst.
8.11 Close the EV valve, if open.
10.5 Allow sufficient time for equilibration, readjusting the
8.12 Close the S valve.
8.13 It is permissible to exercise the option of preliminary liquid nitrogen level when necessary. Equilibrium shall be
considered as attained when the pressure change is no more
degassing on an external unit. In such a case, follow the
procedures of 8.4-8.11 and then repeat on the surface area unit, than 0.1 torr in 5 min. If the equilibrium pressure is too low,
open EV valve and re-equilibrate the system.
except that the degassing time in 8.9 should not exceed 1 h.
8.14 If it is desired to weigh the sample after preliminary 10.6 Record the equilibrium pressure as P (1), and manifold
temperature T 8(1).
degassing on an external unit, backfill with the same gas used
in 8.2 to above atmospheric pressure. Close the S valve. 10.7 Record the liquid nitrogen temperature T (1) or the
s
nitrogen vapor pressure P (1).
Otherwise, use the weight obtained in 10.18 and omit 8.15.
8.15 Detach the sample tube from the apparatus, recap with 10.8 Close the S valve and close the EV valve; then admit
nitrogen gas to increase the pressure as needed (usually by 100
the stopper used previously, and weigh. Record the weight as
W . to 200 torr), depending upon surface area. The increments
should be small (usually smaller than 100 to 200 torr) when
8.16 Remove the backfilled gas by evacuation to less than
−4
10 torr at room temperature. P/P is less than 0.1. Record the pressure, P (2), and the
0 1
temperature, T 8(2).
9. Procedure—Dead-Space Determination
10.9 Open the S valve to admit the new increment of
9.1 From this point on, each sample being tested for nitrogen to the catalyst.
micropore volume an
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