EFFECT OF ALKALINE MODIFICATION OF PRODUCTS OF THERMAL VACUUM AND HYDROTHERMAL TREATMENT OF NH4NA-Y ZEOLITE ACCORDING TO THE IR SPECTRAL DATA

The effect of alkaline modification on the structure of the products o f heat treatment of NH4Na-Y zeolite (53% NH4+, Si/Al - 2.37) in a vacu um at 573 K and in water vapors at 873 K was investigated with the IR spectrum of vibrations of the zeolite framework in the 400-1200 cm-1 r egion. It was shown that the high-frequency shift of the bands in the spectra of the products obtained, the stretching vibration of (nu)as(T O4) tetrahedrons in particular (T = Si, Al) al 1023 cm-1 by 6 and 19 c m-1, is determined by a decrease in the excess negative charge of the framework due to weakening and hydrolytic splitting of Al-O bonds of t he deammoniated units with the formation of bridging =Si-O(H)...Al= an d terminal =Si-OHHO-Al= hydroxyl groups. Treatment of these samples wi th an aqueous solution of KOH (pH congruent-to 13.4) at 293 and 353 K restores the normal framework =Si-O-Al= bonds at the sites of formatio n of bridging and terminal hydroxyl groups. In the second case, restor ation is hindered by substitution of H+ by K+ with some silanol groups .