PDF GB/T 19587-2017 English (GB/T 19587-2004: Older version)
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Determination of the specific surface area of solids by gas adsorption using the BET method
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Determination of the specific surface area of solids by gas adsorption using the BET method
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GB/T 19587-2017: PDF in English (GBT 19587-2017) GB/T 19587-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.160
H 16
GB/T 19587-2017 / ISO 9277-2010
Replacing GB/T 19587-2004
Determination of the specific surface area of solids by gas
adsorption using the BET method
(ISO 9277:2010, IDT)
ISSUED ON: SEPTEMBER 29, 2017
IMPLEMENTED ON: APRIL 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Symbols ... 9
5 Principle ... 10
6 Procedure ... 12
7 Evaluation of adsorption data ... 20
8 Test report ... 23
9 Use of reference materials... 24
Annex A (Informative) Cross-sectional areas of some frequently used adsorptives .. 25
Annex B (Informative) Certified reference materials for the BET method ... 26
Annex C (Informative) Surface area of microporous materials ... 29
References ... 34
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 19587-2004, Determination of the specific surface area
of solids by gas adsorption using the BET method.
Compared with GB/T 19587-2004, the major changes of this Standard are as follows:
⎯ ADD types of adsorption isotherms to which the BET method is applicable and
relevant content of chemisorption;
⎯ ADD terms such as volume adsorbed, macropore, mesopore and micropore;
⎯ REMOVE some symbols in Table 1;
⎯ MODIFY the Principle to a large extent;
⎯ ADD Figure 1 IUPAC classification of adsorption isotherms;
⎯ REMOVE Figure 2, Figure 6, Figure 7 and relevant notes in the original standard,
and MODIFY some figures;
⎯ CHANGE the clauses of the standard.
⎯ ADD “9 Use of reference materials”.
This Standard is identical to ISO 9277:2010 Determination of the specific surface area
of solids by gas adsorption - BET method by using the translation method.
This Standard was proposed by the China Nonferrous Metals Industry Association.
This Standard shall be under the jurisdiction of National Technical Committee on
Nonferrous Metals of Standardization Administration of China (SAC/TC 243) and
National Technical Committee 168 on Screening and Particles Screen Analysis of
Standardization Administration of China (SAC/TC 168).
Drafting organizations of this Standard: Guangzhou Institute of Nonferrous Metals,
Xi’an Sailong Metal Materials Co., Ltd., Beijing JWGB Sci.& Tech. Co., Ltd.,
Northwest Institute for Non-ferrous Metal Research, Beijing Society for Powder
Technology, National Center for Nanoscience and Technology, China Productivity
Center for Machinery.
Main drafters of this Standard: Tan Lixin, Liu Xin, Cai Yixiang, Wang Li, He Weiwei,
Gao Yuan, Zhou Suhong, Chen Jinmei, Gao Jie, Yan Xiaoying, Hou Changge.
The previous version replaced by this Standard is:
Determination of the specific surface area of solids by gas
adsorption using the BET method
1 Scope
This Standard specifies the determination of the overall (see Note) specific external and
internal surface area of disperse (e.g., nano-powders) or porous solids by measuring the
amount of physically adsorbed gas according to the Brunauer, Emmett and Teller (BET)
method [1].
Note: For solids exhibiting a chemically heterogeneous surface, e.g., metal-carrying
catalysts, the BET method gives the overall surface area, whereas the metallic
portion of the surface area can be measured by chemisorption methods.
The BET method is applicable only to adsorption isotherms of type II (disperse,
nonporous or macroporous solids) and type IV (mesoporous solids, pore diameter
between 2 nm ~ 50 nm). Inaccessible pores are not detected. The BET method cannot
reliably be applied to solids which absorb the measuring gas.
A strategy for specific surface area determination of microporous materials (type I
isotherms) is described in Annex C.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 8213, Chemical products for industrial use – Sampling techniques – Solid
chemical products in the form of particles varying from powders to coarse lumps
ISO 14488, Particulate materials – Sampling and sample splitting for the
determination of particulate properties
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
adsorption
Adsorption isotherms may be obtained by volumetric, gravimetric, calorimetric or
spectroscopic measurement or by the carrier gas method using continuous or
discontinuous operation (see 6.3).
6 Procedure
6.1 Sample preparation
Sampling shall be carried out in accordance with ISO 8213 and ISO 14488. Prior to the
determination of an adsorption isotherm, remove physically adsorbed material from the
sample surface by degassing, while avoiding irreversible changes to the surface.
Ascertain the maximum temperature at which the sample is not affected by
thermogravimetric analysis (see Figure 3), by spectroscopic methods, or by trial
experiments using different degassing conditions of time and temperature. When
vacuum conditions are used, degassing to a residual pressure of approximately 1 Pa or
better is usually sufficient. Degassing of the sample can also be performed at elevated
temperature by flushing with an inert gas (e.g., helium). Degassing is complete when a
steady value of the residual gas pressure p, of its composition or of the sample mass is
reached.
Using the vacuum technique, isolate the heated sample container from the pump and
trap (at time ti in Figure 4). If the pressure is nearly constant over a period of 15 min ~
30 min, degassing is complete. Almost invariant pressure also confirms the absence of
leaks. The specific surface area should be related to the mass of the degassed sample.
After degassing, the sample container is cooled to the measuring temperature. It should
be noted that, at low gas pressures, the temperature of the sample needs some time to
equilibrate due to the reduced thermal conductivity within the sample cell.
For sensitive samples, a pressure-controlled heating (see Figure 5) is recommended.
This procedure consists in varying the heating rate in relationship to the gas pressure
evolved from a porous material during the degassing under vacuum conditions. When
a fixed pressure limit, pL (usually around 7 Pa ~ 10 Pa), is surpassed due to the desorbed
material from the sample surface, the temperature increase is stopped and the
temperature is kept constant until the pressure falls below the limit. At that point, the
system continues the temperature ramp. This procedure is particularly suitable for
avoiding structural changes in microporous materials, when fast heating rates can
damage fragile structures due to a vigorous vapour release. In addition, the method is
very safe in preventing sample elutriation when water or other vapours are released
from the pores in very fine powder materials.
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