GB/T 5816-1995 Method for Determining the Surface Area of Catalysts and Adsorbents
The surface area of catalysts and adsorbents is a measure of the internal surface area of the intact material. This surface area is an important parameter for predicting the effect of catalytic and adsorptive processes and for assessing the performance of catalysts and adsorbents. This standard (GB/T 5816-1995) specifies the determination methods of physical adsorption, chemisorption, nitrogen adsorption and other methods for determining the surface area of catalysts and adsorbents.
1Scope
This standard specifies physical adsorption, chemisorption, nitrogen adsorption and other methods for determining the surface area of catalysts and adsorbents, and provides a method for determining the surface area of porous materials, suspensions and colloids.
2Normative references
The refrences in this standard are all mandatory.
GB/T 5009.11 Analytical Method for Determination of Carbon Dioxide content of Gases
3Terminology
3.1 Wilhelmy Balance
A new balance for measuring the surface tension of liquid, in which the surface tension force is directly measured by a mechanical device with laser reflection, instead of using the traditional glass tube or platinum plate.
3.2 Chemisorption
Chemisorption is a kind of adsorption, which is caused by chemical interactions, such as electrostatic attraction, hydrogen bonding and other types of interactions, between the surface of the adsorption material and the adsorbed molecule.
3.3 Physical Adsorption
Physical adsorption is a kind of adsorption, which is caused by the weak forces, such as Van der Waals force and intermolecular force.
3.4 Nitrogen Adsorption
Nitrogen adsorption is a kind of adsorption, which is caused by the electrostatic and Van der Waals forces between the adsorbed molecule and the adsorbed surface.
4Methods for Determining the Surface Area of Catalysts and Adsorbents
4.1 Physical Adsorption
4.1.1 Prerequisites
The adsorption material must meet the following requirements:
(1) It must be able to withstand the operation temperature of the adsorption media.
(2) The particle size must be evenly distributed.
(3) The surface area must be higher than 0.5 m²/g.
(4) The surface properties must be stable.
4.1.2 Principle
Physical adsorption is based on the principle that the surface area of a material can be determined by measuring the amount of adsorbed gas on its surface. The surface area of a material is proportional to the amount of adsorbed gas.
The amount of gas adsorbed is proportional to the pressure. The amount of gas adsorbed can be calculated from the pressure of the adsorbed gas.
4.1.3 Apparatus
4.1.3.1 Adsorption measuring device: The device must be capable of measuring the pressure of the adsorbed gas.
4.1.3.2 Vacuum pump: The vacuum pump must be capable of reaching the required pressure.
4.1.4 Sample Preparation
The samples must be prepared according to the method specified by the manufacturer.
4.1.5 Procedure
(1) Place the sample in the adsorption measuring device.
(2) Evacuate the device to the required pressure.
(3) Measure the pressure of the adsorbed gas.
(4) Calculate the surface area of the material.
4.2 Nitrogen Adsorption
4.2.1 Principle
Nitrogen adsorption is based on the principle that the surface area of a material can be determined by measuring the amount of nitrogen that is adsorbed onto its surface. The surface area of a material is proportional to the amount of adsorbed nitrogen.
4.2.2 Apparatus
4.2.2.1 Adsorption measuring device: The device must be capable of measuring the pressure of the adsorbed nitrogen.
4.2.2.2 Vacuum pump: The vacuum pump must be capable of reaching the required pressure.
4.2.2.3 Nitrogen tank: The nitrogen tank must be capable of supplying the required amount of nitrogen.
4.2.3 Sample Preparation
The samples must be prepared according to the method specified by the manufacturer.
4.2.4 Procedure
(1) Place the sample in the adsorption measuring device.
(2) Evacuate the device to the required pressure.
(3) Introduce nitrogen into the device.
(4) Measure the pressure of the adsorbed nitrogen.
(5) Calculate the surface area of the material.
4.3 Chemisorption
4.3.1 Principle
Chemisorption is based on the principle that the surface area of a material can be determined by measuring the amount of a chemical that is adsorbed onto its surface. The surface area of a material is proportional to the amount of adsorbed chemical.
4.3.2 Apparatus
4.3.2.1 Adsorption measuring device: The device must be capable of measuring the pressure of the adsorbed chemical.
4.3.2.2 Vacuum pump: The vacuum pump must be capable of reaching the required pressure.
4.3.2.3 Chemisorption medium: The chemisorption medium must be capable of providing the required amount of chemical.
4.3.3 Sample Preparation
The samples must be prepared according to the method specified by the manufacturer.
4.3.4 Procedure
(1) Place the sample in the adsorption measuring device.
(2) Evacuate the device to the required pressure.
(3) Introduce the chemisorption medium into the device.
(4) Measure the pressure of the adsorbed chemical.
(5) Calculate the surface area of the material.
4.4 Other Methods
4.4.1 Wilhelmy Balance
The Wilhelmy balance is based on the principle of measuring the surface tension of liquids. It is used to measure the amount of liquid that can be adsorbed on a solid surface. The surface area of the solid is proportional to the amount of liquid that can be adsorbed.
4.4.2 Carbon Dioxide Content
The surface area of a material can be determined by measuring the carbon dioxide content of a gas that is adsorbed onto its surface. The surface area of the material is proportional to the amount of adsorbed gas.
5Calculation and Expression of Results
5.1 The surface area of catalysts and adsorbents shall be calculated in accordance with the formula specified by the method used for the determination.
5.2 Results shall be reported in m²/g form.
5.3 Results shall be expressed with one significant figure after the decimal point and preceded by the letters SA, e.g. SA=2.7 m²/g.
6Test Report
A test report shall be issued in accordance with the requirements of GB/T 5005.
