The effect of flexible lattice aluminium in zeolites during the nitration of aromatics

摘要

The nitration of toluene with nitric acid and acetic anhydride with zeolite catalysts wasstudied by means of multi-nuclear solid-state NMR spectroscopy in order to explain theenhanced para-selectivity observed with zeolite beta. The reversible transformation offramework aluminium from a tetrahedral into an octahedral environment was revealed by ~(27)AlNMR upon interaction of the zeolite with the different components of the nitrating system.The octahedral co-ordination complex between lattice aluminium and acetyl nitrate mightexplain the surface-catalyzed para-selective nitration reaction. The flexibility of the latticeseems to play an important role in the regio-selectivity of nitration catalyzed by zeolites.