ASTM D3908-99
(Test Method)Standard Test Method for Hydrogen Chemisorption on Supported Platinum on Alumina Catalysts and Catalyst Carriers By Volumetric Vacuum Method
Standard Test Method for Hydrogen Chemisorption on Supported Platinum on Alumina Catalysts and Catalyst Carriers By Volumetric Vacuum Method
SCOPE
1.1 This test method covers the determination of the chemisorption of hydrogen at 298 K (25°C) on supported platinum catalysts that have been reduced in flowing hydrogen at 723 K (450°C). It incorporates a static volumetric vacuum technique at constant volume.
1.2 The test method is intended for use on unused supported platinum on alumina catalysts of loadings greater than 0.3 weight %. Data on other supports and lower platinum loadings were not tested.
1.3 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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.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.
Designation: D 3908 – 99
AMERICAN SOCIETY FOR TESTING AND MATERIALS
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Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Hydrogen Chemisorption on Supported Platinum on
Alumina Catalysts and Catalyst Carriers By Volumetric
Vacuum Method
This standard is issued under the fixed designation D 3908; 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
P 5 equilibrium pressure after expansion for
e
x
generating X equilibrium point, torr
1.1 This test method covers the determination of the chemi-
V 5 volume of calibrated bulb, cm
sorption of hydrogen at 298 K (25°C) on supported platinum
c
V 5 volume of manifold between stopcocks 12
m
catalysts that have been reduced in flowing hydrogen at 723 K
and 2 with only 4 and 1 open, cm
(450°C). It incorporates a static volumetric vacuum technique
V 5 volume of dead space in sample cell con-
d
at constant volume.
taining catalyst (volume between 2 and 3),
1.2 The test method is intended for use on unused supported
cm
platinum on alumina catalysts of loadings greater than 0.3
V (STP) 5 volume of gas adsorbed at STP, cm
ads x
weight %. Data on other supports and lower platinum loadings
V ( STP) 5 cumulative volume of gas adsorbed
ads cx
were not tested.
through X,cm
1.3 This standard does not purport to address all of the
T 5 temperature representative of the manifold
m
Ax
safety concerns, if any, associated with its use. It is the
prior to expansion into the sample cell, K
responsibility of the user of this standard to establish appro-
T 5 temperature representative of the entire
m
Bx
priate safety and health practices and determine the applica-
system after equilibrium pressure (P ) has
e
x
bility of regulatory limitations prior to use.
been established, K
T 5 temperature of manifold prior to expan-
m
2. Referenced Documents
sion into sample cell for dead space deter-
2.1 ASTM Standards:
mination, K
E 691 Practice for Conducting an Interlaboratory Study to
T 5 temperature of entire system after equilib-
m
2 D
Determine the Precision of a Test Method
rium pressure has been established for
dead space determination, K
3. Symbols
T 5 average manifold temperature for a given
3.1 The following symbols are used:
dose, K
5 (T + T )/2
m m
Ax Bx
W 5 weight of catalyst, g
cat
P 5 pressure of gas in calibrated bulb, torr
c
P 5 pressure of gas in calibrated bulb and
mc
4. Significance and Use
manifold, torr
4.1 This test method sets forth a procedure by which
P 5 pressure in manifold, torr
m
duplicate catalyst samples can be compared either on an
P 5 pressure in manifold and dead space, torr
md
interlaboratory or intralaboratory basis. It is anticipated that
P 5 pressure in manifold prior to expansion
m
x
catalyst producers and users will find this test method of value.
into sample tube for X equilibration point,
4.2 Discrimination of the samples for which this procedure
torr
is recommended must be exercised when considering carrier
(support) materials that ad(ab)sorb appreciable quantities of
hydrogen or could cause an alteration of the state of the catalyst
during pretreatment, or both, (that is, sintering or metal
occlusion). These materials must be identified by the user and
This test method is under the jurisdiction of ASTM Committee D-32 on
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
experimented with to determine the most significant conditions
Chemical Properties.
of measurement.
Current edition approved April 10, 1999. Published June 1999. Originally
e1
4.3 This test method provides a measure of the total
published as D 3908 – 80. Last previous edition D 3908 – 88 (1993) .
Annual Book of ASTM Standards, Vol 14.02.
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 3908
hydrogen uptake (mL(at standard conditions (STP)H /g of
catalyst)) without specifying the nature of the hydrogen-
platinum interaction. Persons interested in using hydrogen
uptake data to calculate percent platinum (dispersion) in a
specific catalyst should be aware of carrier (support) interac-
tions, spill-over effects, and other phenomena related to the
hydrogen uptake capabilities of the catalyst in question.
5. Apparatus
5.1 Gas-Handling System as shown in Fig. 1. The compo-
nents may be either glass or metal. Commercial metal instru-
ments are available. The following components are to be
included in the glass system:
5.1.1 Vacuum System capable of attaining pressures below
−5
1 mPa (1 3 10 torr). The vacuum can be monitored with any
suitable vacuum gage. A diffusion pump backed by a mechani-
cal pump must be isolated from the system by a trap held at
liquid nitrogen temperature. High-vacuum stopcocks using a
low-vapor pressure grease can be employed.
5.1.2 Pressure-Measuring Device that operates at constant
volume and that is capable of reading in the range from 0 to
66.7 kPa (0 to 500 torr) to the nearest 0.01 kPa (0.1 torr).
5.1.3 Calibration Bulb whose volume has been carefully
determined to within 0.1 % prior to attachment to the main
manifold. Typically one fills the bulb and stopcock bore with
mercury, weighs it, and calculates the volume of the bulb from
the density of mercury at the temperature of the measurement.
Following careful cleaning, the bulb is attached to the main
manifold. One should make sure that the glass blowing is
sufficiently far removed from the calibrated volume to avoid
distortion.
5.1.4 Flow-Through Cell that can be evacuated and that can
be detached from the main manifold as, for example, see Fig.
2. This is accomplished by including a removeable joint, if
FIG. 2 A Suitable Sample Cell
glass, a male cone joint, on the manifold end of the tube. (Other
types of joints, that is, Swagelok with TFE-fluorocarbon
fittings, etc., are suitable.) Its mate is attached to the main maintaining the furnace at temperatures in the range from 673
manifold by a glass vacuum stopcock. A stopcock is also to 773 6 10 K (400 to 500° C).
included on the vent side of the cell to allow for vacuum and 5.1.7 Thermometer or Thermocouple to monitor the fur-
flow-through procedures. nace temperature to within 65 K and two thermometers to
5.1.5 Catalyst Sample, secured by a quartz wool plug register the temperature of the manifold system and sample cell
upstream of the catalyst and another quartz wool plug down- during uptake determination to the nearest 60.1 K.
stream (Fig. 2). The sample should be in the form of an 5.1.8 Balance measuring to the nearest 1 mg (60.001 g).
extrudate, pellets, or powder greater than 20 mesh. 5.1.9 Flowmeter for hydrogen capable of measuring a flow
5.1.6 Furnace capable of maintaining a heating rate of 5 rate of between 10 and 25 6 3cm (STP) gas per gram of
deg/min and a temperature-control mechanism capable of catalyst per minute.
FIG. 1 Schematic: Static Vacuum System
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 3908
5.2 Gas Purification Facilities for helium and hydrogen. known since a final weight after hydrogen uptake determina-
tion will be made. It may, however, be useful for the determi-
6. Reagents
nation of volatile or combustible matter present, or both, on the
6.1 High-Purity Helium purified by passing through a trap unused catalyst.
9.1.1 Plugs of quartz wool are to be charged to the cell as
containing activated (Note 1) molecular sieve of the A type or
13X type, maintained at liquid nitrogen temperature. shown in Fig. 2. Weigh the cell and wool plug(s).
9.1.2 Charge at least1gof catalyst to the cell.
NOTE 1—Activation as suggested by manufacturer.
9.1.3 Connect the cell to the main manifold at stopcock 2
6.2 High-Purity Hydrogen purified by passing first through
and vent.
an oxygen removal catalyst or palladium thimble and then
9.1.4 Secure the thermocouple to the glass along the outside
through a trap containing activated molecular sieve of the A
of the center of the catalyst bed (Fig. 2).
type or 13X type maintained at liquid nitrogen temperature.
6.3 High-Purity Cylinder Air purified by passing through a 10. Air Calcination
trap containing activated molecular sieve of the A series.
10.1 To ensure removal of adsorbed hydrocarbons from the
catalyst surface due to ambient contamination a calcination in
7. Safety Hazards
purified air is recommended.
7.1 Follow the usual precautions associated with handling
10.1.1 Close all stopcocks except 3, 2, and 1. Establish a
hydrogen gas. Adequatel
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