Hydrophilicity of Mordenites with Different SiO2/Al2O3 Molar Ratio

Hydrophicility of H-mordenites with SiO2/Al2O3 molar ratio (MR) varying in the range from 10 up to 206 was investigated by IR spectroscopy, TPD of ammonia and thermogravimetry methods. It was found that dealuminated mordenite retains affinity for water in the entire MR range, in contrast to published results for synthetic pentasil zeolites. In H-mordenites extra-framework aluminum exists in the form of dimers of aluminum hydroxide, those presumably are stabilized in the channels of mordenite. An inversely proportional correlation between the water content in pores and the concentration of channel Lewis sites was observed.