Functions of energy distributions of acid sites on HY zeolite

Abstract

The complex thermodesorption spectra of pyridine were resolved into independent parallel desorption steps. Distribution of activation energies was introduced and Dirac, Gauss and Weibull probability density functions were applied. Assignment of the acid sites as weak Lewis (S1), and weak (S2) and strong (S3) Bronsted sites was established. Application of the Dirac function on desorption from sites S1, S2 and S3 fitted only for very low values of the pre-exponential factors, i.e. 104 s-1. The Gauss function provided results similar to those of the asymmetrical Weibull function. © 1987 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division).