ASTM D4365-95(2007)e1
(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
SIGNIFICANCE AND USE
This gas adsorption method complements the X-ray procedure of Test Method D 3906. This test method will be useful to laboratories that do not have X-ray diffractometers. Each test method can be calibrated by use of an appropriate series of mechanical mixtures to provide what may be termed percent zeolite. If there is disorder in the zeolite, the adsorption method will yield higher values than the X-ray method. The reverse will be true if some zeolite pores (micropores) are blocked or filled.
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 a specific precautionary statement, see Note 3.
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Standards Content (Sample)
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e1
Designation:D4365–95 (Reapproved 2007)
Standard Test Method for
Determining Micropore Volume and Zeolite Area of a
Catalyst
This standard is issued under the fixed designation D4365; 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.
e NOTE—Editorial changes were made throughout in April 2007.
1. Scope 3.1.1 mesopore area of a catalyst—the area determined
from the slope of the t-plot.
1.1 This test method covers the determination of total
3.1.2 micropore volume of the catalyst—the pore volume in
surface area and mesopore area. From these results are calcu-
pores having radii less than 1 nm, usually associated with the
lated the zeolite area and micropore volume of a zeolite
zeolite portion of the catalyst, and determined from the
containing catalyst. The micropore volume is related to the
intercept of the t-plot.
percent zeolite in the catalyst. The zeolite area, a number
3.1.3 surface area of a catalyst—the total surface of the
relatedtothesurfaceareawithinthezeolitepores,mayalsobe
catalyst pores. It is expressed in square metres per gram.
calculated. Zeolite area, however, is difficult to intepret in
3.1.4 zeoliteareaofacatalyst—thedifferencebetweentotal
physical terms because of the manner in which nitrogen
surface area and mesopore area.
molecules pack within the zeolite.
3.2 Symbols:
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 appro-
P = initial helium pressure, torr
H
priate safety and health practices and determine the applica-
P = helium pressure after equilibration, torr
H
bility of regulatory limitations prior to use. For a specific
S = slope of BET plot, 11.7
B
precautionary statement, see Note 3.
I = intercept of BET plot, 11.7
B
S = slope of t-plot, 11.13
t
2. Referenced Documents
I = intercept of t-plot, 11.13
t
2.1 ASTM Standards: T = temperature of manifold at initial helium pres-
H1
D3663 Test Method for Surface Area of Catalysts and
sure, °C
T = temperature of manifold after equilibration, °C
Catalyst Carriers
H2
T 8(i) = extra volume bulb temperature, °C
D3906 Test Method for Determination of Relative X-ray
x
T (i) = extra volume bulb temperature, K
Diffraction Intensities of Faujasite-Type Zeolite- x
P (i) = initial N pressure, torr
Containing Materials 1 2
T (i) = manifold temperature at initial N pressure, K
1 2
E177 Practice for Use of the Terms Precision and Bias in
T 8(i) = manifold temperature at initial N pressure, °C
1 2
ASTM Test Methods
P (i) = pressure after equilibration, torr
E456 Terminology Relating to Quality and Statistics
T (i) = manifold temperature after equilibration, K
E691 Practice for Conducting an Interlaboratory Study to
T 8(i) = manifold temperature after equilibration, °C
Determine the Precision of a Test Method
P (i) = liquid nitrogen vapor pressure, torr
T (i) = liquid nitrogen temperature, K
s
3. Terminology
X = relative pressure, P /P
2 0
3.1 Definitions of Terms Specific to This Standard:
V = volume of manifold, cm
d
V = extra volume bulb, cm
x
V = effective void volume, cm
s
This test method is under the jurisdiction of ASTM Committee D32 on
W = weight of sample, g
s
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
W = tare weight of sample tube, g
Chemical Properties.
W = weight of sample+tare weight of tube, g
Current edition approved April 1, 2007. Published May 2007. Originally 2
approved in 1984. Last previous edition approved in 2001 as D4365–95(2001). V = volume of nitrogen in the dead-space, cm
ds
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
V = see 11.4.3
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
V = see 11.4.4
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.
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D4365–95 (2007)
the nearest 0.05 cm . V includes the volume of the stopcock
V = see 11.4.5
x
t
bore in the glass apparatus. It is preferred that this volume be
V = see 11.4.7
a
held at the same temperature as that of the distribution
V = see 11.8
m
BET (i) = see 11.4.8 manifold.
t(i) = see 11.10
NOTE 2—Modern commercial instruments automatically adjust the
amounts dosed in order to produce data points at user-selected target
4. Summary of Test Method
pressures.Hence,theuseofanEVbulbisoptional.Someinstrumentscan
4.1 The volume of nitrogen gas adsorbed by the catalyst at
analyze multiple samples simultaneously and may use sample tubes with
liquid nitrogen temperature is measured at various low- volumes outside of the range specified in this test method.
pressure levels. This is done by measuring pressure differen-
3 3
6.2 Sample Tubes, with volumes from 5 cm to 25 cm
tials caused by introducing a fixed volume of nitrogen to the
depending on the application. Markings should be placed on
degassed catalyst in the test apparatus. This procedure is the
the sample tubes about 30 to 50 mm below the connectors to
same as Test Method D3663, that gives total surface area, but
indicate the desired liquid nitrogen level.
extends the pressure range to permit calculation of micropore
6.3 Heating Mantles or Small Furnaces.
volume and matrix surface area, by the t-plot method. Zeolite
6.4 Dewar Flasks.
area is the difference between total area and matrix area.
−7
6.5 Laboratory Balance, with 0.1 mg (10 kg) sensitivity.
5. Significance and Use
6.6 Thermometer, for measuring the temperature of the
distribution manifold, T 8(i)or T 8(i), in degrees Celsius.
5.1 This gas adsorption method complements the X-ray 1 2
6.7 Thermometer, for measuring the temperature of the
procedure of Test Method D3906. This test method will be
liquid nitrogen bath T (i) in kelvins. This will preferably be a
useful to laboratories that do not have X-ray diffractometers.
s
nitrogenvapor-pressure-thermometerthatgivesP directlyand
Each test method can be calibrated by use of an appropriate
has greater precision, or a resistance thermometer from which
series of mechanical mixtures to provide what may be termed
P values may be derived.
percentzeolite.Ifthereisdisorderinthezeolite,theadsorption
method will yield higher values than the X-ray method. The 6.8 Thermometer, for measuring the temperature of the EV
reverse will be true if some zeolite pores (micropores) are bulb, T 8(i), if different from T 8(i)or T 8(i).
x 1 2
blocked or filled.
7. Reagents
6. Apparatus
7.1 Purity of Reagents—Reagent grade chemicals shall be
6.1 AschematicdiagramoftheapparatusisshowninFig.1.
used in all tests. Unless otherwise indicated, it is intended that
It may be constructed of glass or of metal. It has the following
all reagents shall conform to the specifications of the Commit-
features:
tee onAnalytical Reagents of theAmerican Chemical Society,
6.1.1 Distribution Manifold, having a volume between 20 4
where such specifications are available. Other grades may be
3 3
and 35 cm,(V ), known to the nearest 0.05 cm . This volume
d
used, provided it is first ascertained that the reagent is of
is defined as the volume between the stopcocks or valves and
sufficiently high purity to permit its use without lessening the
includes the pressure gage. It is preferred that this volume be
accuracy of the determination.
thermostatted.
7.2 Helium Gas—A cylinder of helium gas at least 99.9%
6.1.2 Vacuum System, capable of attaining pressures below
pure.
−4
10 torr (1 torr=133.3 Pa). This will include a vacuum gage
7.3 Liquid Nitrogen, of such purity that P is not more than
(not shown in Fig. 1). Access to the distribution manifold is
20 torr above barometric pressure. A fresh daily supply is
through the valve V.
recommended.
6.1.3 Constant-Volume Gage or Mercury Manometer, ca-
7.4 Nitrogen Gas—A cylinder of nitrogen gas at least
pable of measurements to the nearest 0.1-torr sensitivity in the
99.9% pure.
range from 0 to 1000 torr (1 torr=133.3 Pa).
NOTE 1—See, for example, the article by Joy for a description of a
8. Procedure—Sample Preparation and Degassing
constant-volume manometer.
8.1 Selectasampletubeofthedesiredsize.A5-cm sample
6.1.4 Valve (H), from the helium supply to the distribution
tube is preferred for samples not exceeding about 1 g, to
manifold. 3
minimizethedead-space.However,a25-cm sampletubemay
6.1.5 Value (N),fromthenitrogensupplytothedistribution
be preferred for finely powdered catalysts, to avoid “boiling”
manifold.
when degassing is started.
6.1.6 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.
6.1.7 Extra Volume (EV) Bulb, may be attached through
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
valve EV. Its volume (V ) should be 100 to 150 cm , known to
x
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. Pharmacopeial Convention, Inc. (USPC), Rockville,
Joy, A. S., Vacuum, Vol 3, 1953, p. 254. MD.
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D4365–95 (2007)
FIG. 1 Schematic Diagram of Surface Area Apparatus
8.2 Fill the sample tube with nitrogen or helium, at atmo- 8.15 Detach the sample tube from the apparatus, recap with
sphericpressure,afterremovingairbyevacuation.Thismaybe the stopper used previously, and weigh. Record the weight as
done on the surface area unit, or on a separate piece of W .
equipment. 8.16 Remove the backfilled gas by evacuation to less than
−4
10 torr at room temperature.
8.3 Remove the sample tube from the system, cap, and
weigh. Record the weight as W .
9. Procedure—Dead-Space Determination
8.4 Place the catalyst sample, of which the weight is known
9.1 From this point on, each sample being tested for
approximately,intothesampletube.Choosethesamplesizeto
micropore volume and surface area must be run on an
provideanestimatedtotalsamplesurfaceareaof20to100m .
individualbasis.Thus,eachStep9.2-10.17mustbecarriedout
8.5 Attachthesampletubetotheapparatus.Ifothersamples
separately for each tube in test.
are to be run, attach them at this time to the other ports.
9.2 The “dead-space” is the void volume of the charged
8.6 Open the S valves where there are samples.
sampletube,includingthevolumewithintheSvalve,whenthe
8.7 SlowlyopentheVvalve,monitoringtherateofpressure
tube is immersed in liquid nitrogen to the proper depth.
decreasetoavoidtoohigharate,whichcouldleadtoexcessive
fluidization of powdered samples. NOTE 5—The dead-space may be determined after the nitrogen adsorp-
tion, if more convenient, so long as adequate degassing precedes its
8.7.1 It may be necessary to close the V valve system
determination. In that case, replace the liquid nitrogen bath after 10.14
periodically to protect the diffusion pump fluid from exposure
before proceeding with 9.3-9.9. Then, remove the Dewar flask before
topressuresabove0.1torrforperiodsofmorethan30s.Close
carrying out 10.15-10.17.
the valve off for 2 min each time.
9.3 PlaceaDewarflaskofliquidnitrogenaroundthesample
8.8 Install a heating mantle or furnace around each sample
and adjust the liquid level to a fixed point on the sample tube.
and raise the temperature to about 300°C (573 K).
Maintain this level throughout the test.
NOTE 3—Take special precautions if the moisture content exceeds
9.4 Zero the pressure gage.
approximately5%toavoid“bumping”ofpowderedcatalyst,andtoavoid
9.5 Admit the helium gas into the system to a pressure of
surfacearealossbyself-steaming.Itisrecommendedthattheheatingrate
600to900torrbycarefullyopeningthe Hvalve.With Hvalve
not exceed 100°C(K)/h under these circumstances.
closed,recordthispressure,P ,andthemanifoldtemperature,
H
8.9 Continue degassing at about 300°C (573 K) for a
T .
H
−3
minimum of 3 h, at a pressure not to exceed 10 torr.
9.6 Open the S valve to admit helium to the sample.
Overnight degassing is permissible.
9.7 After about 5 min of equilibration, readjust the liquid
nitrogen level, and record the pressure, P , and the manifold
H
NOTE 4—Zeolite-containing catalysts may contain large quantities of
temperature, T .
H
water.Pretreatmentofthesampleinanovenat400°Cinflowingnitrogen 2
9.8 Repeat 9.5-9.7 for each sample cell attached to the
for a couple of hours may be desirable.
manifold.
8.10 Remove the heating mantles, and allow the samples to
9.9 Open all S valves; then slowly open the V valve to
cool.
remove the helium gas.
8.11 Close the EV valve, if open.
9.10 When a pressure less than 0.01 torr has been attained,
8.12 Close the S valve.
close the S valve. This operation should take 5 to 10 min.
8.13 It is permissible to exercise the option of preliminary
10. Procedure—Nitrogen Adsorption
degassing on an external unit. In such a case, follow the
proceduresof8.4-8.11andthenrepeatonthesurfaceareaunit,
10.1 Close the V valve and open the EV valve. (The extra
except that the degassing time in 8.9 should not exceed 1 h. volume bulb should be thermostatted at a particular tempera-
8.14 If it is desired to weigh the sample after preliminary ture, a few degrees above ambient.)
degassing on an external unit, backfill with the same gas used 10.2 Recheck the zero setting of the pressure gage.
in 8.2 to above atmospheric pressure. Close the S valve. 10.3 Admit nitrogen gas, and record the pressure as P (1)
Otherwise, use the weight obtained in 10.18 and omit 8.15. (torr) and the temperature as T 8 (1) (degrees Celsius). It is
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D4365–95 (2007)
desirable, but not necessary, to choose P (1) such that the first 11. Calculations
equilibrium adsorption pressure, P (1) will be about 8 to 15
11.1 Calculate the weight of sample W , as follows:
s
torr,orP (1)/P ofabout0.01to0.02.RecordT 8(1).Closethe
2 0 x
W 5W 2W (1)
s 2 1
EV valve.
11.2 Calculatetheeffectivevoidvolumeofthesampletube,
10.4 Open the S valve to admit nitrogen to the catalyst.
V , as follows:
10.5 Allow sufficient time for equilibration, readjusting the s
liquid nitrogen level when necessary. Equilibrium shall be
P P
T Vd
H H
s 1 2
V 5 – (2)
s FS D S DG
considered as attained when the pressure change is no more
P ~T 1273.2! ~T 1273.2!
H H H
1 2
than 0.1 torr in 5 min. If the equilibrium pressure is too low,
...
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