Abstract
The amount and the characteristics of silanol groups, which were formed by hydrothermal and acidic treatments of H-type faujasites, were investigated by in situ IR spectroscopy, thermogravimetry in vacuo and mesurements of immersional heats.
The amount of the silanol groups which formed “hydroxy nest” decreased with an increase in the evacuation temperature. The amount of the silanol groups on meso pore surface and outside the crystal, which did not form “hydroxy next”, was almost constant in the temperature range between 298 and 873K.
The influence of the formation of “hydroxy nest” on the polarity of zeolite surface was investigated by measurements of immersional heats into water and some organic liquids. The immersional heats of H-Y770 into polar liquids were almost constant irrespective of the difference in the amount of silanol groups of zeolites. Therefore, the silanol groups which formed “hydroxy nest” were linked each other by hydrogen bonds and became inactive to approaching molecules.
