TEMPERATURE-PROGRAMMED DESORPTION (TPD) OF N-METHYL-PYRROLIDINE ON HNAY ZEOLITES

Temperature-programmed desorption of an amount of N-methyl-pyrrolidine which corresponds to the content of isolated bridging SiOHAl groups located in the supercage of a HNaY zeolite results in a non-structured desorption curve. By means of kinetic analysis using various methods it could be shown that the course of desorption is well described by a rate equation of first order considering a dependence of the desorption energy on the degree of coverage or by introducing a density distribution function for the desorption energy. The shape of the desorption energy distribution calculated by the regularization method agrees well with the distribution function which was obtained for temperature-programmed desorption of ammonia. Therefore, this shape of the energy distribution represents a suitable quantitative measure for the acid strength distribution of isolated SiOHAl groups in the HNaY zeolite.