ASTM D3943-00
(Test Method)Standard Test Method for Total Molybdenum in Fresh Alumina-Base Catalysts
Standard Test Method for Total Molybdenum in Fresh Alumina-Base Catalysts
SCOPE
1.1 This test method covers the determination of molybdenum in alumina-base catalysts and has been cooperatively tested at molybdenum concentrations from 8 to 18 weight%, expressed as MoO 3 . Any component of the catalyst other than molybdenum such as iron, tungsten, etc., which is capable of being oxidized by either ferric or ceric ions after being passed through a zinc-amalgam reductor column (Jones reductor) will interfere.
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.
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Designation: D 3943 – 00
Standard Test Method for
Total Molybdenum in Fresh Alumina-Base Catalysts
This standard is issued under the fixed designation D 3943; 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 ferroin indicator. The indicator undergoes a color change (pink
to colorless or very faint blue-green) in the presence of excess
1.1 This test method covers the determination of molybde-
+2
ceric ion. The amount of Fe titrated in the reaction
num in alumina-base catalysts and has been cooperatively
1 2 1 4 1 3 1 3
tested at molybdenum concentrations from 8 to 18 weight %,
Fe 1 Ce → Fe 1 Ce (2)
expressed as MoO . Any component of the catalyst other than
+6
is a direct measure of Mo concentration.
molybdenum such as iron, tungsten, etc., which is capable of
being oxidized by either ferric or ceric ions after being passed
4. Significance and Use
through a zinc-amalgam reductor column (Jones reductor) will
4.1 This test method sets forth a procedure by which
interfere.
catalyst samples can be compared either on an interlaboratory
1.2 This standard does not purport to address all of the
or intralaboratory basis. It is anticipated that catalyst producers
safety concerns, if any, associated with its use. It is the
and users will find this method of value.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Interferences
bility of regulatory limitations prior to use.
5.1 Elements such as As, Sb, Cr, Fe, Ti, V, U, or W can
interfere in this analysis. If serious interference occurs, it will
2. Referenced Documents
be necessary to isolate the molybdenum from the interfering
2.1 ASTM Standards:
species prior to measurement.
D 1193 Specification for Reagent Water
5.2 Organics and nitrates can interfere or react with the
E 173 Practice for Conducting Interlaboratory Studies of
zinc-amalgam if the sulfuric acid treatment is not properly
Methods for Chemical Analysis of Metals
carried out as described in 9.1.
E 507 Test Method for Aluminum in Iron Ores by Atomic
Absorption Spectroscopy
6. Apparatus
6.1 Beakers, 250-mL.
3. Summary of Test Method
6.2 Jones Reductor Column, 30-cm long by 2 cm in outer
3.1 The catalyst is digested in hot sulfuric acid to dissolve
diameter, with a 100-mL reservoir. Attach a piece of vinyl
molybdenum, destroy organic matter, and to expel nitrates if
tubing to the end of the delivery tube long enough to extend to
present. The acid solution is diluted and passed through an
the bottom of the filtering flask (see Test Method E 507).
amalgamated zinc column (Jones reductor) into a receiving
6.3 Vacuum Filtering Flask, heavy-walled, 1000-mL.
flask contaning an excess of ferric ammonium sulfate. The
6.4 Buret, 50-mL, Class A (0.1-mL divisions).
+6
column quantitatively reduces the molybdenum (Mo to
6.5 Stirring Motor, magnetic, and TFE-fluorocarbon-
+3
Mo ) which in turn is reoxidized in the receiving flask
5 9
covered stirring bars, 7.9 by 14.2 mm ( ⁄16 by 1 ⁄16 in.).
according to the reaction:
1 3 1 3 1 6 1 2
7. Reagents
Mo 1 3Fe → Mo 1 3Fe (1)
+3 7.1 Purity of Reagents—Reagent grade chemicals shall be
3.2 The ferrous ion produced (three per Mo oxidized) is
used in all tests. Unless otherwise indicated, it is intended that
titrated with standard ceric sulfate solution in the presence of
all reagents shall conform to the specifications of the Commit-
tee on Analytical Reagents of the American Chemical Society,
This test method is under the jurisdiction of ASTM Committee D32 on
Catalysts and is the direct responsibility of Subcommittee D 32.03 on Chemical
Composition. Part No. 8035-J10. The sole source of supply of this apparatus known to the
Current edition approved April 10, 2000. Published May 2000. Originally committee at this time is Arthur H. Thomas Co. If you are aware of alternative
e1
published as D 3943 – 80. Last previous edition D 3943 – 86 (1994) . suppliers, please provide this information to ASTM Headquarters. Your comments
Annual Book of ASTM Standards, Vol 11.01. will receive careful consideration at a meeting of the responsible technical
3 1
Annual Book of ASTM Standards, Vol 03.05. committee which you may attend.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 3943
where such specifications are available. Other grades may be is presumed that parties using this test method for comparison
used provided it is first ascertained that the reagent is of purposes will have agreed on the selection of an analytical
sufficiently high purity to permit its use without lessening the sample which is appropriate to their needs.
accuracy of the determination. 8.2 Pulverize the analytical sample to pass a 150-μm (No.
7.2 Purity of Water—Unless otherwise indicated, references 100) sieve. Ignite the pulverized sample for 30 min at 550°C in
to water shall be understood to mean reagent water conforming a muffle furnace. Allow to cool in a desiccator.
to Specification D 1193.
7.3 Ceric Sulfate, 0.10 N standardized using sodiummo- 9. Procedure
lybdate following the procedure given in Annex A1.
9.1 Transfer a 0.75-g specimen, weighed to the nearest 1
7.4 Ferric Ammonium Sulfate Solution — [FeNH (SO ) ·12
4 4 2 mg, into a 250-mL beaker. Add 20 mL of 1 + 1 H SO solution
2 4
H O]—Dissolve 200 g of [FeNH (SO ) ·12 H O] in 1000 mL
2 4 4 2 2
and heat to fumes on a hot plate. Cool, rinse down with 10 mL
of water containing 20 mL of concentrated sulfuric acid. Add
of water and take to fumes again. Cool, add 100 mL of water
potassium permanganate solution dropwise until a pink color
and heat to dissolve. Cool to room temperature.
persists for 1 min.
9.2 Activate the Jones reductor by passive five 25-mL
7.5 Ferroin Indicator, 0.025 M solution of 1, 10-
portions (1 min/25 mL of solution passed) of the 1 + 19H SO
2 4
phenanthroline ferrous sulfate complex.
through the column, using slight vacuum. Do not allow the
7.6 Jones Reductor Amalgam.
amalgam to become exposed to air. Test the column by passing
7.7 Molybdenum Standard Solution—Dissolve 1.0 g,
a blank of 25 mL of 1 + 19 H SO through the reductor into a
2 4
weighed to the nearest 0.1 mg, of sodium molybdate dihydrate
receiver containing 15 mL of ferric ammonium sulfate solu-
(Na MoO ·2H O) in water containing 10 mL of H SO ,
2 4 2 2 4 tion. Add 2 to 3 drops of ferroin indicator and 10 mL of
transfer to a 1-L volumetric flask, dilute to volume, and mix (1
concentrated H PO and titrate with 0.1 N ceric sulfate
3 4
mL 5 0.5948 mg MoO ).
3 solution until the pink indicator color completely disappears
7.8 Phosphoric Acid (H PO ), concentrated—Mix 130 mL
3 4
and is replaced by a colorless to faint blue green color which
of concentrated H SO with 250 mL of water. Add the acid
2 4 persists for at least 15 s. If more than 1 or 2 drops of ceric
slowly with constant stirring. Ad
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