Physico—chemical characterization of pentasil type materials: II. Thermal analysis of the precursors

Abstract

The zeolitic samples synthesized by the A- and G-type syntheses were investigated by thermal analysis. They behave identically in most of their properties: the hydrophobicity of the channels, the presence of two types of tetrapropylammonium (TPA) ions and the diffusion of n-pentane. The TPA ions which are desorbed at higher temperatures (460°–485°C) are attributed those neutralizing partially the framework negative charges. The other type of TPA ions, which are desorbed at lower temperatures (410°–440°C), corresponds to TPAOH. The total amount of TPA decreases with increasing AI concentration. The only difference between the A- and G-type samples concerns the variation of the relative amount of the high temperature peak with the framework charge balance, expressed as the difference (AlNa), for negative (AlNa) values. The difference between the zeolitic samples stems probably from the higher Al content of the Asamples for similar (AlNa) values.