ASTM D4365-95(2008)
(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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Designation: D4365 − 95(Reapproved 2008)
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 (´) indicates an editorial change since the last revision or reapproval.
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
surface area and mesopore area. From these results are calcu-
3.1.2 micropore volume of the catalyst—the pore volume in
lated the zeolite area and micropore volume of a zeolite
pores having radii less than 1 nm, usually associated with the
containing catalyst. The micropore volume is related to the
zeolite portion of the catalyst, and determined from the
percent zeolite in the catalyst. The zeolite area, a number
intercept of the t-plot.
relatedtothesurfaceareawithinthezeolitepores,mayalsobe
3.1.3 surface area of a catalyst—the total surface of the
calculated. Zeolite area, however, is difficult to intepret in
catalyst pores. It is expressed in square metres per gram.
physical terms because of the manner in which nitrogen
3.1.4 zeoliteareaofacatalyst—thedifferencebetweentotal
molecules pack within the zeolite.
surface area and mesopore area.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.2 Symbols:
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
P = initial helium pressure, torr
H
bility of regulatory limitations prior to use. For a specific 1
P = helium pressure after equilibration, torr
H
precautionary statement, see Note 3. 2
S = slope of BET plot, 11.7
B
I = intercept of BET plot, 11.7
B
2. Referenced Documents
S = slope of t-plot, 11.13
t
2.1 ASTM Standards:
I = intercept of t-plot, 11.13
t
D3663Test Method for Surface Area of Catalysts and
T = temperatureofmanifoldatinitialheliumpressure,
H1
Catalyst Carriers
°C
D3906Test Method for Determination of Relative X-ray
T = temperature of manifold after equilibration, °C
H2
Diffraction Intensities of Faujasite-Type Zeolite- T `(i) = extra volume bulb temperature, °C
x
T (i) = extra volume bulb temperature, K
Containing Materials
x
P (i) = initial N pressure, torr
E177Practice for Use of the Terms Precision and Bias in 1 2
T (i) = manifold temperature at initial N pressure, K
ASTM Test Methods 1 2
T `(i) = manifold temperature at initial N pressure, °C
1 2
E456Terminology Relating to Quality and Statistics
P (i) = pressure after equilibration, torr
E691Practice for Conducting an Interlaboratory Study to
T (i) = manifold temperature after equilibration, K
Determine the Precision of a Test Method
T `(i) = manifold temperature after equilibration, °C
P (i) = liquid nitrogen vapor pressure, torr
3. Terminology
T (i) = liquid nitrogen temperature, K
s
3.1 Definitions of Terms Specific to This Standard:
X = relative pressure, P /P
2 0
V = volume of manifold, cm
d
V = extra volume bulb, cm
x
This test method is under the jurisdiction of ASTM Committee D32 on
V = effective void volume, cm
s
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
W = weight of sample, g
s
Chemical Properties.
W = tare weight of sample tube, g
Current edition approved April 1, 2008. Published May 2008. Originally
ϵ1 W = weight of sample+tare weight of tube, g
approved in 1984. Last previous edition approved in 2007 as D4365–95(2007) .
V = volume of nitrogen in the dead-space, cm
DOI: 10.1520/D4365-95R08.
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
V = see 11.4.5
t
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4365 − 95 (2008)
FIG. 1 Schematic Diagram of Surface Area Apparatus
NOTE 1—See, for example, the article by Joy for a description of a
V = see 11.4.7
a
constant-volume manometer.
V = see 11.8
m
6.1.4 Valve (H), from the helium supply to the distribution
BET(i) = see 11.4.8
t(i) = see 11.10
manifold.
6.1.5 Value (N), from the nitrogen supply to the distribution
4. Summary of Test Method manifold.
6.1.6 The connection between the sample tube and the S
4.1 The volume of nitrogen gas adsorbed by the catalyst at
valve can be a standard-taper glass joint, a glass-to-glass seal,
liquid nitrogen temperature is measured at various low-
or a compression fitting.
pressure levels. This is done by measuring pressure differen-
6.1.7 Extra Volume (EV) Bulb, may be attached through
tials caused by introducing a fixed volume of nitrogen to the
valve EV. Its volume (V ) should be 100 to 150 cm , known to
x
degassed catalyst in the test apparatus. This procedure is the
the nearest 0.05 cm . V includes the volume of the stopcock
x
same as Test Method D3663, that gives total surface area, but
bore in the glass apparatus. It is preferred that this volume be
extends the pressure range to permit calculation of micropore
held at the same temperature as that of the distribution
volume and matrix surface area, by the t-plot method. Zeolite
manifold.
area is the difference between total area and matrix area.
NOTE 2—Modern commercial instruments automatically adjust the
amounts dosed in order to produce data points at user-selected target
5. Significance and Use
pressures.Hence,theuseofanEVbulbisoptional.Someinstrumentscan
5.1 This gas adsorption method complements the X-ray
analyze multiple samples simultaneously and may use sample tubes with
procedure of Test Method D3906. This test method will be volumes outside of the range specified in this test method.
3 3
useful to laboratories that do not have X-ray diffractometers.
6.2 Sample Tubes, with volumes from 5 cm to 25 cm
Each test method can be calibrated by use of an appropriate
depending on the application. Markings should be placed on
series of mechanical mixtures to provide what may be termed
the sample tubes about 30 to 50 mm below the connectors to
percentzeolite.Ifthereisdisorderinthezeolite,theadsorption
indicate the desired liquid nitrogen level.
method will yield higher values than the X-ray method. The
6.3 Heating Mantles or Small Furnaces.
reverse will be true if some zeolite pores (micropores) are
blocked or filled. 6.4 Dewar Flasks.
−7
6.5 Laboratory Balance, with 0.1 mg (10 kg) sensitivity.
6. Apparatus
6.6 Thermometer, for measuring the temperature of the
6.1 AschematicdiagramoftheapparatusisshowninFig.1.
distribution manifold, T `(i)or T `(i), in degrees Celsius.
1 2
It may be constructed of glass or of metal. It has the following
6.7 Thermometer, for measuring the temperature of the
features:
liquid nitrogen bath T (i) in kelvins. This will preferably be a
s
6.1.1 Distribution Manifold, having a volume between 20
3 3
nitrogenvapor-pressure-thermometerthatgivesP directlyand
and 35 cm,(V ), known to the nearest 0.05 cm . This volume
d
has greater precision, or a resistance thermometer from which
is defined as the volume between the stopcocks or valves and
P values may be derived.
includes the pressure gage. It is preferred that this volume be
thermostatted. 6.8 Thermometer, for measuring the temperature of the EV
6.1.2 Vacuum System, capable of attaining pressures below
bulb, T `(i), if different from T `(i)or T `(i).
x 1 2
−4
10 torr (1 torr=133.3 Pa). This will include a vacuum gage
7. Reagents
(not shown in Fig. 1). Access to the distribution manifold is
7.1 Purity of Reagents—Reagent grade chemicals shall be
through the valve V.
6.1.3 Constant-Volume Gage or Mercury Manometer, ca- used in all tests. Unless otherwise indicated, it is intended that
pable of measurements to the nearest 0.1-torr sensitivity in the
range from 0 to 1000 torr (1 torr=133.3 Pa). Joy, A. S., Vacuum, Vol 3, 1953, p. 254.
D4365 − 95 (2008)
NOTE 4—Zeolite-containing catalysts may contain large quantities of
all reagents shall conform to the specifications of the Commit-
water.Pretreatmentofthesampleinanovenat400°Cinflowingnitrogen
tee onAnalytical Reagents of theAmerican Chemical Society,
for a couple of hours may be desirable.
where such specifications are available. Other grades may be
8.10 Remove the heating mantles, and allow the samples to
used, provided it is first ascertained that the reagent is of
cool.
sufficiently high purity to permit its use without lessening the
accuracy of the determination.
8.11 Close the EV valve, if open.
7.2 Helium Gas—A cylinder of helium gas at least 99.9%
8.12 Close the S valve.
pure.
8.13 It is permissible to exercise the option of preliminary
7.3 Liquid Nitrogen, of such purity that P is not more than
degassing on an external unit. In such a case, follow the
20 torr above barometric pressure. A fresh daily supply is
proceduresof8.4-8.11andthenrepeatonthesurfaceareaunit,
recommended.
except that the degassing time in 8.9 should not exceed 1 h.
7.4 Nitrogen Gas—A cylinder of nitrogen gas at least
8.14 If it is desired to weigh the sample after preliminary
99.9% pure.
degassing on an external unit, backfill with the same gas used
in 8.2 to above atmospheric pressure. Close the S valve.
8. Procedure—Sample Preparation and Degassing
Otherwise, use the weight obtained in 10.18 and omit 8.15.
8.1 Selectasampletubeofthedesiredsize.A5-cm sample
8.15 Detach the sample tube from the apparatus, recap with
tube is preferred for samples not exceeding about 1 g, to
the stopper used previously, and weigh. Record the weight as
minimizethedead-space.However,a25-cm sampletubemay
W .
be preferred for finely powdered catalysts, to avoid “boiling” 2
when degassing is started.
8.16 Remove the backfilled gas by evacuation to less than
−4
10 torr at room temperature.
8.2 Fill the sample tube with nitrogen or helium, at atmo-
sphericpressure,afterremovingairbyevacuation.Thismaybe
9. Procedure—Dead-Space Determination
done on the surface area unit, or on a separate piece of
equipment.
9.1 From this point on, each sample being tested for
8.3 Remove the sample tube from the system, cap, and micropore volume and surface area must be run on an
weigh. Record the weight as W .
individualbasis.Thus,eachStep9.2-10.17mustbecarriedout
separately for each tube in test.
8.4 Place the catalyst sample, of which the weight is known
approximately,intothesampletube.Choosethesamplesizeto
9.2 The “dead-space” is the void volume of the charged
provideanestimatedtotalsamplesurfaceareaof20to100m .
sampletube,includingthevolumewithintheSvalve,whenthe
tube is immersed in liquid nitrogen to the proper depth.
8.5 Attachthesampletubetotheapparatus.Ifothersamples
are to be run, attach them at this time to the other ports.
NOTE 5—The dead-space may be determined after the nitrogen
adsorption,ifmoreconvenient,solongasadequatedegassingprecedesits
8.6 Open the S valves where there are samples.
determination. In that case, replace the liquid nitrogen bath after 10.14
8.7 SlowlyopentheVvalve,monitoringtherateofpressure
before proceeding with 9.3-9.9. Then, remove the Dewar flask before
carrying out 10.15-10.17.
decreasetoavoidtoohigharate,whichcouldleadtoexcessive
fluidization of powdered samples.
9.3 PlaceaDewarflaskofliquidnitrogenaroundthesample
8.7.1 It may be necessary to close the V valve system
and adjust the liquid level to a fixed point on the sample tube.
periodically to protect the diffusion pump fluid from exposure
Maintain this level throughout the test.
topressuresabove0.1torrforperiodsofmorethan30s.Close
9.4 Zero the pressure gage.
the valve off for 2 min each time.
9.5 Admit the helium gas into the system to a pressure of
8.8 Install a heating mantle or furnace around each sample
600to900torrbycarefullyopeningtheHvalve.WithHvalve
and raise the temperature to about 300°C (573 K).
closed,recordthispressure,P ,andthemanifoldtemperature,
H
NOTE 3—Take special precautions if the moisture content exceeds
T .
H
approximately5%toavoid“bumping”ofpowderedcatalyst,andtoavoid
surfacearealossbyself-steaming.Itisrecommendedthattheheatingrate
9.6 Open the S valve to admit helium to the sample.
not exceed 100°C(K)/h under these circumstances.
9.7 After about 5 min of equilibration, readjust the liquid
8.9 Continue degassing at about 300°C (573 K) for a
nitrogen level, and record the pressure, P , and the manifold
−3
H
minimum of 3 h, at a pressure not to exceed 10 torr.
temperature, T .
H
Overnight degassing is permissible.
9.8 Repeat 9.5-9.7 for each sample cell attached to the
manifold.
Reagent Chemicals, American Chemical Society Specifications, American
9.9 Open all S valves; then slowly open the V valve to
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
remove the helium gas.
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
9.10 When a pressure less than 0.01 torr has been attained,
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. close the S valve. This operation should take 5 to 10 min.
D4365 − 95 (2008)
NOTE 6—For an introduction to BET and t-plot theories and
10. Procedure—Nitrogen Adsorption
5 6
applications, see Lowell and Shields, Lippens and de Boer, and
10.1 Close the V valve and open the EV valve. (The extra Johnson.
volume bulb should be thermostatted at a particular
10.14 SlowlyopentheVvalve,removetheDewarflask,and
temperature, a few degrees above ambient.)
allow the sample tube to warm to room temperature.
10.2 Recheck the zero setting of the pressure gage.
10.15 If the sample was weighed in 8.15, go to Section 11.
10.3 Admit nitrogen gas, and record the pressure as P (1)
10.16 When frost has disappeared from the sample tube,
(torr) and the temperature as T ` (1) (degrees Celsius). It is
wipe it dry.
desirable, but not necessary, to choose P (1) such that the first
10.17 Backfillthesampletubewiththesamegasusedin8.2
equilibrium adsorption pressure, P (1) will be about 8 to 15
to about atmospheric pressure. Close the S valve.
torr,orP (1)/P ofabout0.01to0.02.RecordT `(1).Closethe
2 0 x
10.18 Detach the sample tube from the apparatus, recap
EV valve.
withthestopperusedpreviously,andweigh.Recordtheweight
10.4 Open the S valve to admi
...
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