Specific surface area calculation method - Database & Sql Blog Articles

1.

Specific surface area of the catalyst

:

Refers to the total internal and external surface area per unit mass of a porous material.

Unit:

m²/g

2.

For porous catalysts or carriers

:

Measurable method	Total specific surface area	Active specific surface area
BET method, chromatography	BET method, chromatography

3. BET Adsorption isotherm equation —— BET Specific surface (currently recognized as the standard method for measuring the specific surface area of solids)

(2) A common method for determining the amount of gas adsorbed: 1. Volumetric method — The specific surface area is measured by calculating the difference in volume of gas before and after adsorption. The sample is degassed first, then adsorption is performed. 2. Gravimetric method — This method uses a high-sensitivity quartz spring scale to measure the elongation caused by gas adsorption. It can handle multiple samples at once but has lower accuracy compared to the volumetric method. 3. Gas chromatography — This method does not require a high vacuum system and is faster and more sensitive, making it suitable for industrial use. When using chromatography, the stationary phase is the solid itself, and gases like N₂, H₂, etc., are used as carriers. 4. Determining different surface areas in complex catalysts — Physical adsorption methods only measure the total surface area, while chemical adsorption is used to determine the active surface area of individual components. For example, in Pt/Al₂O₃ or Pt/SiO₂-Al₂O₃ catalysts, H₂, O₂, or CO can be used to measure the exposed Pt surface. 5. Surface area measurement below 1 m²/g — Low-temperature nitrogen adsorption has limitations for very low surface areas. Helium adsorption is more accurate for such cases. 6. Active surface area determination — Using selective chemisorption, such as hydrogen peroxide titration, allows for measuring the active surface area. 7. Langmuir Adsorption isotherm — Describes monolayer adsorption with assumptions about uniform surface energy and no interaction between adsorbed particles. The equation helps calculate the specific surface area based on adsorption data.