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Methode voor Specifiek Oppervlak Meting van Microporeuse Materialen (Type I Isotherm) What are the problems?

In the literature, it is said that BET theory should not be applied to Type I isotherm. However, the surface area is an important parameter for the characterization of materials, and actually, the surface areas of microporous materials are often calculated. Then what are the problems and how can we evaluate the surface area?

Problems:

Adsorption image into the micropore

Adsorption image into the micropore

2. Since there is a big curvature in micropores, the use of cross sectional area to calculate the surface area underestimates the value.

Evaluation of surface area in the micropore

Evaluation of surface area in the micropore

Solutions:
1. BET-plot should be applied to the low relative pressure range (0.05 - 0.1) because in this range, multi-layer adsorption of BET theory occurs and there is linearity in the plot. In this case, C parameter must be positive.

Type I isotherm and BET-plot

Type I isotherm and BET-plot


2.De berekende oppervlakte van type I isotherm moet beschouwd worden als het BET specifiek oppervlak en niet het aktuele geometrische specifiek oppervlak.

Dit BET specifiek oppervlak heeft een goede overeenkomst met de adsorptie hoeveelheid en reactiviteit. Het is dus niet noodzakelijk om het geometrisch specifiek oppervlak te evalueren voor de aktuele toepassingen.

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