ASTM D4824-03

Standard Test Method for Determination of Catalyst Acidity by Ammonia Chemisorption

SIGNIFICANCE AND USE
This test method can be used to determine the acidity of catalysts and catalyst carriers by ammonia chemisorption for materials specifications, manufacturing control, and research and development in the evaluation of catalysts.
SCOPE
1.1 This test method covers the determination of acidity of catalysts and catalyst carriers by ammonia chemisorption. A volumetric measuring system is used to obtain the amount of chemisorbed ammonia.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 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.

General Information

• Status: Historical
• Publication Date: 30-Sep-2003
• Technical Committee: D32 - Catalysts
• Drafting Committee: D32.01 - Physical-Chemical Properties

Relations

• Replaces: ASTM D4824-94(1999) - Standard Test Method for Determination of Catalyst Acidity by Ammonia Chemisorption
• Effective Date: 01-Oct-2003
• Replaced By: ASTM D4824-03(2008) - Standard Test Method for Determination of Catalyst Acidity by Ammonia Chemisorption
• Effective Date: 01-Apr-2008

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D4824–03
Standard Test Method for
Determination of Catalyst Acidity by Ammonia
1
Chemisorption
This standard is issued under the fixed designation D4824; 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.
INTRODUCTION
This test method involves the measurement of total catalyst acidity by chemisorption of ammonia
in a static volumetric system. Acidity is a very important parameter in determining catalyst activity
and selectivity in many commercial reactions. Zeolite based catalysts used in the petroleum industry
for catalytic cracking are a prime example. This test method describes a simple procedure employing
inexpensive equipment that could readily be assembled in most laboratories.
3
1. Scope
V = calibrated expansion volume, cm .
k
T = temperature of V at initial ammonia pressure, K.
1.1 This test method covers the determination of acidity of 1 k
T = temperature of V at final ammonia pressure, K.
catalysts and catalyst carriers by ammonia chemisorption. A 2 k
P = initial ammonia pressure, torr.
1
volumetric measuring system is used to obtain the amount of
P = final ammonia pressure, torr.
2
chemisorbed ammonia.
W = mass of sample, g.
s
1.2 The values stated in SI units are to be regarded as the
W = tare of sample tube, g.
1
standard. The values given in parentheses are for information
W = sample mass plus tare of tube, g.
2
only.
P = initial ammonia pressure corrected to standard tem-
1T
1.3 This standard does not purport to address all of the
perature, torr.
safety concerns, if any, associated with its use. It is the
P = final ammonia pressure corrected to standard tem-
2T
responsibility of the user of this standard to establish appro-
perature, torr.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 4. Summary of Test Method
4.1 Asample is degassed by heating in a vacuum to remove
2. Referenced Documents
adsorbed vapors from the surface. The sample is then exposed
2
2.1 ASTM Standards:
to an excess of gaseous ammonia and the excess ammonia is
D3766 Terminology Relating to Catalysts and Catalysis
removed by freezing it into a trap cooled with liquid nitrogen.
E691 Practice for Conducting an Interlaboratory Study to
The chemisorbed ammonia is calculated as the difference
Determine the Precision of a Test Method
between the volume of ammonia before exposure and the
volume recovered in the liquid nitrogen trap.
3. Terminology
3.1 Definitions—See Terminology D3766.
5. Significance and Use
3.2 Symbols:
5.1 This test method can be used to determine the acidity of
catalysts and catalyst carriers by ammonia chemisorption for
materials specifications, manufacturing control, and research
and development in the evaluation of catalysts.
1
This test method is under the jurisdiction of ASTM Committee D32 on
6. Apparatus
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
6.1 Aschematic diagram of one type of apparatus is shown
Chemical Properties.
Current edition approved Oct. 1, 2003. Published October 2003. Originally
in Fig. 1. It may be constructed of glass or metal and may
approved in 1988. Last previous edition approved in 1999 as D4824–94 (1999).
operate manually or automatically. It has the following fea-
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tures:
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
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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D4824–03
FIG. 1 Apparatus
6.1.1 Vacuum System, capable of attaining and maintaining 8. Procedure
−4
pressures below 10 torr (0.01 Pa) in the absence of catalyst.
8.1 Weigh sample tubes to 0.1 mg and record as W . Place
1
6.1.2 Expansion Vessel, having a volume between 300 to
approximately2gof sample into the sample tube.
3 3
500 cm (V ) known to the nearest 0.01 cm (Note 1). This
k 8.2 Attach the sample tube to the apparatus.
volume is defined as the volume between stopcocks V and V
7 8 8.3 Open the sample valves (V or V , or both).
5 6
and includes the pressure gage and ammonia bulb.
8.4 Slowly open the valve to the vacuum system (V ),
4
monitoring the rate of pressure decrease to avoid too high a
NOTE 1—An expansion vessel of smaller volume is recommended for
rate, which might lead to excessive fluidization of powdered
materials of low surface area or smaller sample size.
samples.
6.1.3 Constan
...