(725a) Characterization of Hydorophilicity/Hydrophobicity of Zeolites By High-Resolution Gas and Water Vapor Adsorption

Zeolites are crystalline microporous materials and widely used as catalysts in chemical industries. It is very important to establish a methodology for evaluating porous structure and surface hydrophobicity/hydrophilicity of these materials in order to eclucidate their catalitic activity and adsorption behavior.

In this study, we report the characterization of meso- and micro- porous structure of zeolite with different Si/Al ratio using high resolution gas and water vapor adosption. The gas adsorption isotherms were measured using Belsorp-max in the pressure range of p/p_o = 10⁻⁸ – 0.995 at 77.4K for N₂ , 87.3K for Ar.  The water vapor adsorption isotherms were measured in the pressure range of p/p_o = 10⁻⁵ – 0.95 and 298.15K for water vapor. 

To our best knowledge, this is the first report of the adsorption isotherms of water vapor in the above-mentioned pressure range. At very low pressure regions, the uptake of nitrogen and water vapor was quite sensitive to the Si/Al ratio of zeolites. The relationship between the amount and location of Al site in zeolites and water uptake at a very low relative poressre region will be discussed.