ASTM D4365-19

Standard Test Method for Determining Micropore Volume and Zeolite Area of a Catalyst

SIGNIFICANCE AND USE
5.1 This gas adsorption method complements the X-ray procedure of Test Method D3906. 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 interpret in physical terms because of the manner in which nitrogen molecules pack within the zeolite.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific precautionary statement, see Note 3.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2019
• ICS: 71.040.30 - Chemical reagents
• Technical Committee: D32 - Catalysts
• Drafting Committee: D32.01 - Physical-Chemical Properties

Relations

• Replaces: ASTM D4365-13 - Standard Test Method for Determining Micropore Volume and Zeolite Area of a Catalyst
• Effective Date: 01-Jul-2019
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D3906-19 - Standard Test Method for Determination of Relative X-ray Diffraction Intensities of Faujasite-Type Zeolite-Containing Materials
• Effective Date: 01-Apr-2019
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E177-14 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2014
• Refers: ASTM D3906-03(2013) - Standard Test Method for Determination of Relative X-ray Diffraction Intensities of Faujasite-Type Zeolite-Containing Materials
• Effective Date: 01-Dec-2013
• Refers: ASTM E456-13ae3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13a - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae2 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13ae1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013
• Refers: ASTM E456-13 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Aug-2013
• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E177-13 - Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
• Effective Date: 01-May-2013
• Refers: ASTM E456-12e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-May-2012

Overview

ASTM D4365-19 is the standard test method for determining micropore volume and zeolite area of a catalyst using gas adsorption. Developed by ASTM International, this method is a key analytical technique for characterizing catalysts containing zeolites. By measuring nitrogen adsorption at liquid nitrogen temperature and analyzing the data using BET and t-plot methods, laboratories can accurately calculate total surface area, mesopore (matrix) area, micropore volume, and zeolite area of catalysts.

This standard provides an alternative to X-ray diffraction techniques, such as ASTM D3906, and is particularly valuable for laboratories lacking specialized X-ray equipment. The results obtained support quality control, R&D, and comparative studies in catalyst manufacturing and performance evaluation.

Key Topics

• Micropore Volume: Measurement of the volume within pores of radius less than 1 nm, typically corresponding to zeolites’ microporous structures. This value relates directly to the percent zeolite present in the catalyst.
• Zeolite Area: Determination of the internal surface area within zeolite pores, calculated as the difference between the total surface area and the mesopore area.
• Total Surface Area & Mesopore Area: Determined using nitrogen gas adsorption and calculated via the BET method and t-plot analysis.
• Gas Adsorption Analysis: Application of nitrogen adsorption at cryogenic temperatures for accurate surface and pore volume measurements.
• Sample Preparation: Includes degassing procedures to ensure removal of moisture and contaminants before analysis.
• Precision and Reproducibility: The method includes guidelines for interlaboratory studies, ensuring reliable comparison of results.

Applications

ASTM D4365-19 is widely used in the chemical, petrochemical, and catalyst manufacturing industries for:

• Catalyst Quality Control: Measurement of zeolite content and surface properties ensures catalyst batches meet performance specifications.
• R&D in Catalyst Development: Supports the screening and optimization of new zeolite-based catalyst formulations by providing detailed information about microporosity and surface structure.
• Process Optimization: Helps determine the suitability of catalysts for specific chemical reactions by understanding pore architecture and surface area.
• Comparison of Analytical Techniques: Provides a complementary method to X-ray diffraction (ASTM D3906), especially in cases where crystallographic disorder or pore blockage may affect measurement results differently.

The test method is critical for any laboratory or manufacturing operation seeking to optimize catalyst selection and performance based on surface and micropore properties.

Related Standards

• ASTM D3663 – Test Method for Surface Area of Catalysts and Catalyst Carriers: Focuses on total surface area measurement.
• ASTM D3906 – Test Method for Determination of Relative X-ray Diffraction Intensities of Faujasite-Type Zeolite-Containing Materials: Provides X-ray diffraction-based measurements of zeolite content.
• ASTM E177 – Practice for Use of the Terms Precision and Bias in ASTM Test Methods: Defines precision parameters for laboratory analysis.
• ASTM E456 – Terminology Relating to Quality and Statistics: Offers standard definitions for reporting analytical results.
• ASTM E691 – Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method: Guidance on evaluating method reproducibility.

Practical Value

Implementing ASTM D4365-19 enables organizations to:

• Evaluate catalyst materials for micropore structure and zeolite content
• Complement or replace X-ray diffraction techniques when not available
• Ensure consistency and reproducibility in catalyst surface area measurements
• Meet international quality standards and regulatory requirements

This test method is essential for reliable zeolite-containing catalyst characterization, supporting innovation, consistency, and efficiency in catalyst-related processes.

Keywords: catalyst, zeolite area, micropore volume, nitrogen adsorption, t-plot, BET surface area, catalyst characterization, ASTM D4365-19, gas adsorption, catalyst testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4365 − 19
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 Containing Materials
E177Practice for Use of the Terms Precision and Bias in
1.1 This test method covers the determination of total
ASTM Test Methods
surface area and mesopore area. From these results are calcu-
E456Terminology Relating to Quality and Statistics
lated the zeolite area and micropore volume of a zeolite
E691Practice for Conducting an Interlaboratory Study to
containing catalyst. The micropore volume is related to the
Determine the Precision of a Test Method
percent zeolite in the catalyst. The zeolite area, a number
relatedtothesurfaceareawithinthezeolitepores,mayalsobe
3. Terminology
calculated. Zeolite area, however, is difficult to interpret in
physical terms because of the manner in which nitrogen 3.1 Definitions of Terms Specific to This Standard:
molecules pack within the zeolite.
3.1.1 micropore volume of the catalyst, n—the pore volume
inporeshavingradiilessthan1nm,usuallyassociatedwiththe
1.2 The values stated in SI units are to be regarded as
zeolite portion of the catalyst, and determined from the
standard. No other units of measurement are included in this
intercept of the t-plot.
standard.
3.1.2 surface area of a catalyst, n—the total surface of the
1.3 This standard does not purport to address all of the
catalyst obtained from the BET method.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.1.2.1 Discussion—Surface area may be used interchange-
priate safety, health, and environmental practices and deter-
ably with BET area. It is expressed in square meters per gram.
mine the applicability of regulatory limitations prior to use.
3.1.3 t-area of the catalyst, n—theareadeterminedfromthe
For a specific precautionary statement, see Note 3.
slope of the t-plot.
1.4 This international standard was developed in accor-
3.1.3.1 Discussion—t-area may be used interchangeably
dance with internationally recognized principles on standard-
with matrix area or external surface area. It is expressed in
ization established in the Decision on Principles for the
square meters per gram.
Development of International Standards, Guides and Recom-
3.1.4 zeolite area of a catalyst, n—the difference between
mendations issued by the World Trade Organization Technical
total surface area and mesopore area.
Barriers to Trade (TBT) Committee.
3.1.4.1 Discussion—The zeolite area may be used inter-
2. Referenced Documents
changeably with micropore area. It is expressed in square
2.1 ASTM Standards:
meters per gram.
D3663Test Method for Surface Area of Catalysts and
3.2 Symbols:
Catalyst Carriers
D3906Test Method for Determination of Relative X-ray
P = initial helium pressure, torr
Diffraction Intensities of Faujasite-Type Zeolite-
H
P = helium pressure after equilibration, torr
H
S = slope of BET plot, 11.7
B
This test method is under the jurisdiction of ASTM Committee D32 on I = intercept of BET plot, 11.7
B
Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-
A = BET area, 11.9
B
Chemical Properties.
N = Avogadro’s number
CurrenteditionapprovedJuly1,2019.PublishedJuly2019.Originallyapproved
A = Cross-sectional area of adsorbed nitrogen mol-
CS
in 1984. Last previous edition approved in 2013 as D4365–13. DOI: 10.1520/
ecule
D4365-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
S = slope of t-plot, 11.13
t
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
I = intercept of t-plot, 11.13
t
Standards volume information, refer to the standard’s Document Summary page on
A = t-area
t
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4365 − 19
FIG. 1 Schematic Diagram of Surface Area Apparatus
Each test method can be calibrated by use of an appropriate
T = temperatureofmanifoldatinitialheliumpressure,
H1
series of mechanical mixtures to provide what may be termed
°C
percentzeolite.Ifthereisdisorderinthezeolite,theadsorption
T = temperature of manifold after equilibration, °C
H2
T '(i) = extra volume bulb temperature, °C method will yield higher values than the X-ray method. The
x
T (i) = extra volume bulb temperature, K reverse will be true if some zeolite pores (micropores) are
x
P (i) = initial N pressure, torr
blocked or filled.
1 2
T (i) = manifold temperature at initial N pressure, K
1 2
T '(i) = manifold temperature at initial N pressure, °C
1 2
6. Apparatus
P (i) = pressure after equilibration, torr
6.1 AschematicdiagramoftheapparatusisshowninFig.1.
T (i) = manifold temperature after equilibration, K
It may be constructed of glass or of metal. It has the following
T '(i) = manifold temperature after equilibration, °C
P (i) = liquid nitrogen vapor pressure, torr features:
T (i) = liquid nitrogen temperature, K
6.1.1 Distribution or Dosing Manifold, having a volume
s
3 3
P = nitrogen critical pressure
c between 18cm and 40 cm,(V ), known to the nearest
d
T = nitrogen critical temperature
c 0.05cm . This volume is defined as the volume between the
X = relative pressure, P /P
2 0
stopcocks or valves and includes the pressure gauge.
V = volume of manifold, cm
d
6.1.2 Vacuum System, with a pump capable of attaining
V = extra volume bulb, cm
-3 -3
x
3 pressures below4×10 hPa (3 × 10 torr). This can include
V = effective void volume, cm
s
a vacuum gauge (not shown in Fig. 1).Access to the distribu-
W = weight of sample, g
s
tion manifold is through the valve V.
W = tare weight of sample tube, g
6.1.3 Pressure Sensing Devices or Pressure Transducer,
W = weight of sample+tare weight of tube, g
V = volume of nitrogen in the dead-space, cm capable of measurements to the nearest 0.1torr sensitivity in
ds
V = see 11.4.3 the range from 0torr to 1000 torr (1 torr=133.3 Pa).
V = see 11.4.4
2 6.1.4 Valve (H), from the helium supply to the distribution
V = see 11.4.5
t
manifold.
V = see 11.4.7
a
6.1.5 Valve (N), from the nitrogen supply to the distribution
V = see 11.8
m
manifold.
BET(i) = see 11.4.8
6.1.6 The connection between the sample tube and the S
t(i) = see 11.10
valve can be a standard-taper glass joint, a glass-to-glass seal,
4. Summary of Test Method or a compression fitting.
6.1.7 Extra Volume (EV) Bulb, if employed, may be at-
4.1 The volume of nitrogen gas adsorbed by the catalyst at
tachedthroughvalveEV.Itsvolume(V )shouldbe100cm to
x
liquid nitrogen temperature is measured at various low-
3 3
150cm , known to the nearest 0.05 cm . V includes the
x
pressure levels by the catalyst sample at liquid nitrogen
volume of the stopcock bore in the glass apparatus. It is
temperature. This is done by measuring pressure differentials
preferred that this volume be held at the same temperature as
resulting from introducing a fixed volume of nitrogen to the
that of the distribution manifold.
degassed catalyst in the test apparatus. This procedure is the
same as Test Method D3663, that gives total surface area, but
NOTE 1—Modern commercial instruments automatically adjust the
extends the pressure range to permit calculation of micropore
amounts dosed in order to produce data points at user-selected target
pressures.Hence,theuseofanEVbulbisoptional.Theymayalsoinclude
volume and matrix surface area, by the t-plot method. Zeolite
additional Pressure Transducers in addition to the one shown in Fig. 1.
area is the difference between total area and matrix area.
3 3
6.2 Sample Tubes, with volumes from 5 cm to 25 cm
5. Significance and Use
depending on the application. Markings should be placed on
5.1 This gas adsorption method complements the X-ray the sample tubes about 30mm to 50 mm below the connectors
procedure of Test Method D3906. This test method will be toindicatethedesiredliquidnitrogenlevelifautomaticcontrol
useful to laboratories that do not have X-ray diffractometers. of liquid nitrogen level is not available.
D4365 − 19
NOTE 2—Some instruments can analyze multiple samples simultane-
8.2 Fill the sample tube with nitrogen or helium, at baro-
ously and may use sample tubes with volumes outside of the range
metric pressure, after removing air by evacuation.This may be
specified in this test method.
done on the surface area unit, or on a separate piece of
6.3 Heating Mantles or Small Furnaces.
equipment.
6.4 Dewar Flasks.
8.3 Remove the sample tube from the system, cap, and
-7
weigh. Record the weight as W .
6.5 Laboratory Balance, with 0.1 mg (10 kg) sensitivity.
6.6 Thermometer or Thermocouple, for measuring the tem- 8.4 Place the catalyst sample, of which the weight is known
approximately,intothesampletube.Choosethesamplesizeto
perature of the distribution manifold, T '(i)or T '(i), in degrees
1 2
Celsius or T (i) or T (i) in kelvin. provide an estimated total sample surface area of 20m to
1 2
100m , or follow instrument manufacturer’s guidelines.
6.6.1 The manifold may be thermostated at a particular
temperature, a few degrees above ambient, to obviate the
8.5 Attach the sample tube(s) to the Sample Preparation
necessity of recording this temperature at each reading.
unit.
6.7 Pressure Saturation Tube from which P values may be
8.6 Slowly evacuate the sample tube(s), monitoring the rate
measured directly, or Thermometer or Thermocouple, for
of pressure decrease to avoid too high a rate, which could lead
measuring the temperature of the liquid nitrogen bath T (i)in
s
to excessive fluidization of powdered samples.
kelvins from which P values may be derived.
8.6.1 Follow pump manufacturer’s recommendations re-
6.8 Thermometer or Thermocouple, for measuring the tem-
garding maximum pressure and gas volume capacity to avoid
perature of the EV bulb, T '(i), if different from T '(i)or T '(i).
any potential damage to the pump.
x 1 2
6.9 Sample Preparation Unit (not shown) for degassing the
8.7 If provided, fill cold trap with liquid nitrogen.
sample(s) prior to analysis. Can be integral to the surface area
8.8 Install a heating mantle or furnace around each sample
apparatus or can be a separate external unit.
and raise the temperature to about 300°C (573 K).
6.9.1 The Sample Preparation Unit may be equipped with a
cold trap to improve elimination of evolved moisture from the
NOTE 3—Take special precautions if the moisture content exceeds
approximately5%toavoid“bumping”ofpowderedcatalyst,andtoavoid
vacuum system.
surfacearealossbyself-steaming.Itisrecommendedthattheheatingrate
not exceed 100°C(K)⁄h under these circumstances.
7. Reagents
8.9 Continue degassing at about 300°C (573 K) for a
7.1 Purity of Reagents—Reagent grade chemicals shall be
minimum of 3 h, at a pressure not to exceed -0.01 torr.
used in all tests. Unless otherwise indicated, it is intended that
Overnight degassing is permissible.
all reagents shall conform to the specifications of the Commit-
tee onAnalytical Reagents of theAmerican Chemical Society,
NOTE 4—Zeolite-containing catalysts may contain large quantities of
water. Pretreatment of the sample in an oven at 150°C for a couple of
where such specifications are available. Other grades may be
hours may be desirable.
used, provided it is first ascertained that the reagent is of
sufficiently high purity to permit its use without lessening the
8.10 Remove the heating mantles, and allow the samples to
accuracy of the determination. cool.
7.2 Helium Gas—Acylinder of helium gas at least 99.99%
8.11 Close off the vacuum.
pure.
8.12 Backfill the sample tube(s) to barometric pressure. If
7.3 Liquid Nitrogen, of such purity that P is not more than
it is desired to weigh the sample after preliminary degassing,
20 torr above barometric pressure. A fresh daily supply is
backfill with the same gas used in 8.2. Close the valve to the
recommended.
sample tube(s).
7.4 Nitrogen Gas—A cylinder of nitrogen gas at least
8.13 Detach the sample tube from the apparatus, recap with
99.99% pure.
the stopper used previously, and weigh. Record the weight as
W . Otherwise, use the weight obtained in 10.18.
8. Procedure—Sample Preparation and Degassing
8.14 Attach the sample tube, uncapped, to an analysis port
8.1 Selectasampletubeofthedesiredsize.A5cm sample
on the surface area apparatus. Remove the backfilled gas by
tube is preferred for samples not exceeding about 1 g, to
evacuation to less than 0.01 torr at room temperature.
minimizethedead-space.However,a25cm sampletubemay
8.15 Optionally repeat degassing and/or evacuation on the
bepreferredforfinelypowderedcatalysts,toavoid“bumping”
surface area unit, except that this supplementary degassing
when degassing is started.
time in should not exceed 1 h.
9. Procedure—Dead-Space Determination
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
9.1 From this point on, each sample being tested for
listed by the American Chemical Society, see Analar Standards for Laboratory
micropore volume and surface area must be run on an
Chemicals, BDH Ltd., Poole, Dor
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4365 − 13 D4365 − 19
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. 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 intepretinterpret in physical terms because of the manner in which nitrogen molecules pack within the
zeolite.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For a specific precautionary statement, see Note 3.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D3663 Test Method for Surface Area of Catalysts and Catalyst Carriers
D3906 Test Method for Determination of Relative X-ray Diffraction Intensities of Faujasite-Type Zeolite-Containing Materials
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 mesopore (matrix) area of a catalyst—the area determined from the slope of the t-plot.
3.1.1 micropore volume of the catalyst—catalyst, n—the pore volume in pores having radii less than 1 nm, usually associated
with the zeolite portion of the catalyst, and determined from the intercept of the t-plot.
3.1.2 surface area of a catalyst—catalyst, n—the total surface of the catalyst pores. It is expressed in square metres per
gram.obtained from the BET method.
This test method is under the jurisdiction of ASTM Committee D32 on Catalysts and is the direct responsibility of Subcommittee D32.01 on Physical-Chemical
Properties.
Current edition approved April 1, 2013July 1, 2019. Published August 2013July 2019. Originally approved in 1984. Last previous edition approved in 20082013 as
D4365 – 95D4365 – 13.(2008). DOI: 10.1520/D4365-13.10.1520/D4365-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 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.
3.1.2.1 Discussion—
Surface area may be used interchangeably with BET area. It is expressed in square meters per gram.
3.1.3 t-area of the catalyst, n—the area determined from the slope of the t-plot.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4365 − 19
3.1.3.1 Discussion—
t-area may be used interchangeably with matrix area or external surface area. It is expressed in square meters per gram.
3.1.4 zeolite area of a catalyst—catalyst, n—the difference between total surface area and mesopore area.
3.1.4.1 Discussion—
The zeolite area may be used interchangeably with micropore area. It is expressed in square meters per gram.
3.2 Symbols:
P = initial helium pressure, torr
H
P = helium pressure after equilibration, torr
H
S = slope of BET plot, 11.7
B
I = intercept of BET plot, 11.7
B
A = BET area, 11.9
B
N = Avogadro’s number
A = Cross-sectional area of adsorbed nitrogen molecule
CS
S = slope of t-plot, 11.13
t
I = intercept of t-plot, 11.13
t
A = t-area
t
T = temperature of manifold at initial helium pressure, °C
H1
T = temperature of manifold after equilibration, °C
H2
T '(i) = extra volume bulb temperature, °C
x
T (i) = extra volume bulb temperature, K
x
P (i) = initial N pressure, torr
1 2
T (i) = manifold temperature at initial N pressure, K
1 2
T '(i) = manifold temperature at initial N pressure, °C
1 2
P (i) = pressure after equilibration, torr
T (i) = manifold temperature after equilibration, K
T '(i) = manifold temperature after equilibration, °C
P (i) = liquid nitrogen vapor pressure, torr
T (i) = liquid nitrogen temperature, K
s
P = nitrogen critical pressure
c
T = nitrogen critical temperature
c
X = relative pressure, P /P
2 0
V = volume of manifold, cm
d
V = extra volume bulb, cm
x
V = effective void volume, cm
s
W = weight of sample, g
s
W = tare weight of sample tube, g
W = weight of sample + tare weight of tube, g
V = volume of nitrogen in the dead-space, cm
ds
V = see 11.4.3
V = see 11.4.4
V = see 11.4.5
t
V = see 11.4.7
a
V = see 11.8
m
BET(i) = see 11.4.8
t(i) = see 11.10
4. Summary of Test Method
4.1 The volume of nitrogen gas adsorbed by the catalyst at liquid nitrogen temperature is measured at various low-pressure
levels by the catalyst sample at liquid nitrogen temperature. This is done by measuring pressure differentials resulting from
introducing a fixed volume of nitrogen to the degassed catalyst in the test apparatus. This procedure is the same as Test Method
D3663, that gives total surface area, but extends the pressure range to permit calculation of micropore volume and matrix surface
area, by the t-plot method. Zeolite area is the difference between total area and matrix area.
5. Significance and Use
5.1 This gas adsorption method complements the X-ray procedure of Test Method D3906. 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
D4365 − 19
FIG. 1 Schematic Diagram of Surface Area Apparatus
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.
6. Apparatus
6.1 A schematic diagram of the apparatus is shown in Fig. 1. It may be constructed of glass or of metal. It has the following
features:
3 3
6.1.1 Distribution or Dosing Manifold, having a volume between 2018 cm and 3540 cm , (V ), known to the nearest 0.05
d
cm0.05 cm . This volume is defined as the volume between the stopcocks or valves and includes the pressure gage. It is preferred
that this volume be thermostatted.gauge.
−4-3 -3
6.1.2 Vacuum System, with a pump capable of attaining pressures below 4 × 10 torr (1 torr = 133.3 hPa (3 × 10 Pa). torr).
This willcan include a vacuum gagegauge (not shown in Fig. 1). Access to the distribution manifold is through the valve V.
6.1.3 Pressure Sensing Devices or Pressure Transducer, capable of measurements to the nearest 0.1-torr0.1 torr sensitivity in
the range from 00 torr to 1000 torr (1 torr = 133.3 Pa).
NOTE 1—See, for example, the article by Joy for a description of a constant-volume manometer.
6.1.4 Valve (H), from the helium supply to the distribution manifold.
6.1.5 ValueValve (N), from the nitrogen supply to the distribution manifold.
6.1.6 The connection between the sample tube and the S valve can be a standard-taper glass joint, a glass-to-glass seal, or a
compression fitting.
6.1.7 Extra Volume (EV) Bulb, if employed, may be attached through valve EV. Its volume (V ) should be 100100 cm to 150
x
3 3
cm150 cm , known to the nearest 0.05 cm . V includes the volume of the stopcock bore in the glass apparatus. It is preferred that
x
this volume be held at the same temperature as that of the distribution manifold.
NOTE 1—Modern commercial instruments automatically adjust the amounts dosed in order to produce data points at user-selected target pressures.
Hence, the use of an EV bulb is optional. Some instruments can analyze multiple samples simultaneously and may use sample tubes with volumes outside
of the range specifiedThey may also include additional Pressure Transducers in addition to the one shown in Fig. 1this test method.
3 3
6.2 Sample Tubes, with volumes from 5 cm to 25 cm depending on the application. Markings should be placed on the sample
tubes about 3030 mm to 50 mm below the connectors to indicate the desired liquid nitrogen level if automatic control of liquid
nitrogen level is not available.
NOTE 2—Some instruments can analyze multiple samples simultaneously and may use sample tubes with volumes outside of the range specified in
this test method.
6.3 Heating Mantles or Small Furnaces.
6.4 Dewar Flasks.
−7-7
6.5 Laboratory Balance, with 0.1 mg (10 kg) sensitivity.
6.6 Thermometer or Thermocouple, for measuring the temperature of the distribution manifold, T '(i) or T '(i), in degrees
1 2
Celsius.Celsius or T (i) or T (i) in kelvin.
1 2
6.6.1 The manifold may be thermostated at a particular temperature, a few degrees above ambient, to obviate the necessity of
recording this temperature at each reading.
6.7 Pressure Saturation Tube from which P values may be measured directly, or Thermometer or Thermocouple, for measuring
the temperature of the liquid nitrogen bath T (i) in kelvins from which P values may be derived. This will preferably be a nitrogen
s 0
vapor-pressure-thermometer, often referred to in a commercial instrument as a pressure saturation tube, from which P values may
be measured directly with greater precision, or a resistance thermometer from which P values may be derived.
Rouquerol, J., Llewellyn, P., and Rouquerol, F., Stud. Surf. Sci. Catal., 160, 49, 2007.
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6.8 Thermometer or Thermocouple, for measuring the temperature of the EV bulb, T '(i), if different from T '(i) or T '(i).
x 1 2
6.9 Sample Preparation Unit (not shown) for degassing the sample(s) prior to analysis. Can be integral to the surface area
apparatus or can be a separate external unit.
6.9.1 The Sample Preparation Unit may be equipped with a cold trap to improve elimination of evolved moisture from the
vacuum system.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
7.2 Helium Gas—A cylinder of helium gas at least 99.9 %99.99 % pure.
7.3 Liquid Nitrogen, of such purity that P is not more than 20 torr above barometric pressure. A fresh daily supply is
recommended.
7.4 Nitrogen Gas—A cylinder of nitrogen gas at least 99.9 %99.99 % pure.
8. Procedure—Sample Preparation and Degassing
8.1 Select a sample tube of the desired size. A 5-cm5 cm sample tube is preferred for samples not exceeding about 1 g, to
minimize the dead-space. However, a 25-cm25 cm sample tube may be preferred for finely powdered catalysts, to avoid
“bumping” when degassing is started.
8.2 Fill the sample tube with nitrogen or helium, at barometric pressure, after removing air by evacuation. This may be done
on the surface area unit, or on a separate piece of equipment.
8.3 Remove the sample tube from the system, cap, and weigh. Record the weight as W .
8.4 Place the catalyst sample, of which the weight is known approximately, into the sample tube. Choose the sample size to
2 2 2
provide an estimated total sample surface area of 2020 m to 100100 m m, or . follow instrument manufacturer’s guidelines.
8.5 Attach the sample tube to the apparatus. If other samples are to be run, attach them at this time to the other ports.tube(s)
to the Sample Preparation unit.
8.6 Open the S valves where there are samples.
8.6 Slowly openevacuate the Vsample valve,tube(s), monitoring the rate of pressure decrease to avoid too high a rate, which
could lead to excessive fluidization of powdered samples.
8.6.1 It may be necessary to close the Follow V valve system periodically to protect the vacuum pump from exposure to
pressures above 0.1 torr for periods of more than 30 s. Close the valve off for 2 min each time.pump manufacturer’s
recommendations regarding maximum pressure and gas volume capacity to avoid any potential damage to the pump.
8.7 If provided, fill cold trap with liquid nitrogen.
8.8 Install a heating mantle or furnace around each sample and raise the temperature to about 300°C300 °C (573 K).
NOTE 3—Take special precautions if the moisture content exceeds approximately 5 % to avoid “bumping” of powdered catalyst, and to avoid surface
area loss by self-steaming. It is recommended that the heating rate not exceed 100°C(K)/h100 °C(K) ⁄h under these circumstances.
−3
8.9 Continue degassing at about 300°C300 °C (573 K) for a minimum of 3 h, at a pressure not to exceed 10-0.01 torr.
Overnight degassing is permissible.
NOTE 4—Zeolite-containing catalysts may contain large quantities of water. Pretreatment of the sample in an oven at 400°C in flowing nitrogen 150 °C
for a couple of hours may be desirable.
8.10 Remove the heating mantles, and allow the samples to cool.
8.11 Close off the EVvacuum. valve, if open.
8.12 Close the S valve.
8.13 It is recommended to exercise the option of preliminary degassing on an external unit. In such a case, follow the procedures
of 8.4 – 8.11 and then optionally repeat on the surface area unit, except that the supplementary degassing time in 8.9 should not
exceed 1 h.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
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8.12 Backfill the sample tube(s) to barometric pressure. If it is desired to weigh the sample after preliminary degassing on an
external unit, degassing, backfill with the same gas used in 8.2 to barometric pressure. . Close the Svalve valve. Otherwise, use
the weight obtained in to the sample tube(s).10.18 and omit 8.15.
8.13 Detach the sample tube from the apparatus, recap with the stopper used previously, and weigh. Record the weight as W .
Otherwise, use the weight obtained in 10.18.
8.14 Attach the sample tube, uncapped, to an analysis port on the measurement surface area apparatus. Remove the backfilled
−4
gas by evacuation to less than 100.01 torr at room temperature.
8.15 Optionally repeat degassing and/or evacuation on the surface area unit, except that this supplementary degassing time in
should not exceed 1 h.
9. Procedure—Dead-Space Determination
9.1 From this point on, each sample being tested for micropore volume and surface area must be run on an individual basis.
Thus, each Step 9.2 – 10.17 must be carried out separately for each tube in test.
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