Factors Affecting the Formation of Extra-Framework Species and Mesopores During Dealumination of Zeolite Y

Abstract

The dealumination of HY, LiY and NaY zeolites with SiCl4 is interpreted as a two-step process. The first step is the formation of chloride salt of the charge compensating cations and of SiCl3 species probably bound to the framework. This reaction takes place at reaction temperatures as low as 423 K. The second step is the Al, Si exchange. Changes in the degree of dealumination between HY, LiY and NaY are tentatively explained on the basis of cation distributions. Cloro-aluminium complexes formed from AlCl3 and the chloride salt during the second step give rise to 27Al MASNMR resonances at ca. 100 ppm. The micropore system can be preserved if the alkali-chloro-aluminium complexes are not decomposed before washing. No additional dealumination was observed during washing. The extracted aluminium can only be removed partially from the samples.