Zeolite Beta: The relationship between calcination procedure, aluminum configuration, and Lewis acidity

摘要

Zeolite Beta was calcined under a variety of carefully controlled conditions to study the influence of (hydro)thermal treatments on the catalytic activity of zeolite Beta in the Lewis acid-catalyzed Meerwein-Ponndorf-Verley reduction of ketones, The activity of (H)Beta can be increased by several orders of magnitude by mild steaming. The catalytic activity of the materials following reactivation can be diminished again by adsorption of ammonia followed by an induction period. For these changes, an explanation is offered in term of Lewis acidic framework aluminum atoms which undergo a change of configuration depending on the ligands present, rather than becoming extraframework aluminum. FTIR, Si-29, and Al-27 MAS NMR spectroscopy were applied to investigate the changes induced by the (hydro)thermal procedures. (C) 1998 Academic Press. [References: 35]