Low-temperature physisorption

Although the physisorption of hydrogen on zeolites has been studied for 40 years or more (Basmadjian, 1960), early work focused on separation phenomena 

Dubinin model was taken by the authors as evidence that hydrogen displays a fluid behaviour when adsorbed in NaA and an estimate of accessible pore volume led them to infer that all three molecules could enter the smaller P-cages. 

3 Relationship between hydrogen adsorption at 77 K and 15 bar and BET surface area (N2) for zeolites and carbon materials large deviations from the trend at low surface area may be ascribed to blocking effects (see text). 

Zecchina et al. (2005a) studied the adsorption of hydrogen at 77 K and pressures up to 1 bar on a number of different zeolites with the chabazite structure (CHA). Based on previous work and their own observations they identified three characteristics deemed important in hydrogen uptake (i) 

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The low-temperature physisorption (type I isotherm) of hydrogen in zeolites is in good agreement with the adsorption model mentioned above for nanostructured carbon. The desorption isotherm followed the same path as the adsorption, which indicates that no pore condensation occurred. The hydrogen adsorption in zeolites depends linearly on the specific surface areas of the materials and is in very good agreement with the results on carbon nanostructures [24]. 

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