SYNTHESIS AND PHYSICOCHEMICAL PROPERTIES OF DEEPLY DEALUMINATED Y-ZEOLITES

The effect of treatment of zeolite Y with a solution of (NH4)(2)SiF6 o n the zeolite framework, its composition, and the state of the element s were studied by IR spectroscopy, X-ray diffraction analysis, and X-r ay photoelectron spectroscopy. Aluminum was shown to expel from the st ructure via the formation of the so-called subframework aluminum. As t he degree of dealumination increases, the concentration of terminal no nbridging Si-OH and Al-OH groups increases, and the rate of defect for mation in the zeolite structure exceeds the rate of silicon insertion. Dealumination in the presence of ammonium acetate favors the more com plete removal of the subframework aluminum due to which silicon can oc cupy free vacancies.