Proton mobility in H-ZSM5 studied by impedance spectroscopy

The electrical properties of dehydrated zeolite H-ZSM5 with different SiO2/ Al2O3 ratios (30, 50, 80, 150, 280, and 1000) were examined by complex impe dance spectroscopy. We determined the activation energy for proton relaxati on, which depends an the spatial distance of the aluminum sites. Classical hopping theory as well as Debye-Huckel theory are in agreement with the exp erimental data implying that the relaxation originates from translational p roton hopping instead of local reorientational motion, as assumed from H-1- MAS-NMR as well as from quantum-chemical calculations. (C) 1999 Elsevier Sc ience BN; All rights reserved.