ASTM D4926-89(2001)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact ASTM
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Designation:D4926–89(Reapproved 2001)
Standard Test Method for
Gamma Alumina Content in Catalysts Containing Silica and
Alumina by X-Ray Powder Diffraction
This standard is issued under the fixed designation D 4926; 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 interference, such as alpha-quartz and zeolite Y, as well as
aluminum-containing spinels formed at elevated temperatures.
1.1 This test method covers the determination of gamma
If the presence of interfering material is suspected, the diffrac-
alumina and related transition aluminas in catalysts containing
tion pattern should be examined in greater detail. More
silica and alumina by X-ray powder diffraction, using the
significant interference may be caused by the presence of large
diffracted intensity of the peak occurring at about 67°2u when
amounts of heavy metals or rare earths, which exhibit strong
copper Ka radiation is employed.
X-ray absorption and scattering. Comparisons between similar
1.2 This standard does not purport to address all of the
materials, therefore, may be more appropriate than those
safety concerns, if any, associated with its use. It is the
between widely varying materials.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 X-Ray Powder Diffractometer Unit, with standard
2. Referenced Documents sample mount, Cu Ka radiation, monochromator, wide diver-
gence and receiving slits (for example, 3° and 0.15°, respec-
2.1 ASTM Standards:
tively), goniometer speed of 0.5°/min or equivalent, chart
E 691 Practice for Conducting an Interlaboratory Study to
speed of about 0.5 cm/min or equivalent, and scale or gain
Determine the Precision of a Test Method
factors to provide conveniently measurable peaks.
3. Summary of Test Method
NOTE 1—For diffractometers employing step scanning, convenient
3.1 A sample of catalyst is calcined and ground, and an
corresponding conditions include a step size of 0.02° and a counting time
X-ray powder diffraction pattern is obtained under specified of 2.4 s/step, which is equivalent to a scanning rate of 0.5°/min.
conditions over the approximate range from 52 to 76°2u. The
5.2 Calcination Furnace.
diffracted intensity above background for the peak occurring at
5.3 Grinding Equipment, suitable for preparing samples for
about 67°2u is compared to that of a reference sample, after
mounting in the sample holder.
appropriate adjustments are made for scale settings and peak
half-widths. 6. Procedure
6.1 Calcine the catalyst sample for3hat 500°C.
4. Significance and Use
6.2 Grind the sample sufficiently (for example, 200 to 400
4.1 This test method is for estimating the relative amount of
mesh) to enable it to be packed into a standard X-ray powder
gamma alumina in calcined catalyst samples, assuming that the
diffractometer sample holder and mounted on the diffractome-
X-ray powder diffraction peak occurring at about 67°2u is
ter.
attributable to gamma alumina. Gamma alumina is defined as
6.3 Obtain diffraction patterns for three samples over the
a transition alumina formed after heating in the range from 500
approximate range from 52 to 76°2u, using the conditions
to 550°C, and may include forms described in the literature as
described in 5.1.
eta, chi, and gamma aluminas. Delta alumina has a diffraction
6.4 Measure the height of the 67°2u peak above background
peak in the same region, but is formed above 850°C, a
for the sample and the reference material to give H (sample)
temperature to which most catalysts of this type are not heated.
and H (reference), respectively.
There are other possible components which may cause some
NOTE 2—Reference material may be prepared by calcining a high-
purity sample of fine-particle boehmite for3hat 550°C.
This test method is under the jurisdiction of ASTM Committee D32 on
Catalysts and is the direct respon
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