Thermal activation of ammonium forms of Y zeolites. I. T.p.d., i.r., and catalytic investigations of the deammoniation of NH 4NaY zeolites

Abstract

The deammoniation of a series of NH 4NaY zeolites of various exchange degrees has been studied thermodesorptometrically using different methods in order to obtain independent statements about the kinetics of the desorption process. In all cases at least two overlapping NH 3 peaks have been observed, the separation of which was possible by means of a temperature stop method. These two peaks could be ascribed to the desorption of NH 3 from OH groups of different kinds. The assignment of the peaks was possible by comparison of the desorptogrammes with i.r. spectra in the range of the OH stretching vibrations and with results of catalytic but-1-ene isomerization measurements. The calculated activation energies for NH 3 desorption seem to be suitable for the characterization of the acid strength of the OH groups. They were compared with partial charges of the hydrogen, calculated by means of the Sanderson electronegativity concept.