Dealuminated H−Y Zeolites: Influence of the Degree and the Type of Dealumination Method on the Structural and Acidic Characteristics of H−Y Zeolites

Abstract

Dealuminated zeolite samples prepared by different methods are characterized by different techniques, and the structural and acidic characteristics are investigated in an effort to identify the parameters that decide their structural and acidic characteristics. The investigation gave evidence that the structure breakdown of the parent type-Y zeolite is mainly dependent on the degree of dealumination, but the nature of extraframework aluminum (EFAl) species formed is dependent on the type of dealumination procedure. Monomeric Al species and oligomeric Si,Al species were formed by steam treatment at relatively low and high temperatures, respectively. Aluminosilicate phases of Si/Al ratios 2.0−4.0 and 8.0 were found in SiCl4-treated and ammonium hexafluorosilicate (AHFS)-treated samples, respectively. EFAl species of octahedral and tetrahedral coordination were observed by NMR spectra in steam and SiCl4-treated samples. High degrees of dealumination within each type of treatment resulted in loss of microporo...