Characterization of basicity in alkaline cation faujasite zeolites—An XPS study using pyrrole as a probe molecule

Abstract

An X-ray photoelectron spectroscopic method is proposed for the characterization of Lewis basic sites in alkali-cation faujasite zeolites. The method consists of deconvoluting the N 1 s XPS line of chemisorbed pyrrole and measuring the relative intensities of the peak components. It was found that whenever the zeolite sample contains two kinds of alkali cation, two different deconvoluted N 1 s peaks corresponding to pyrrole chemisorbed on these two sites are obtained. Combined with previous infrared observations, the results offer further evidence for the basic sites being the framework oxygens adjacent to the alkali cations in faujasite zeolites. The stronger the basic site, the lower the N 1 s binding energy level of the corresponding peak component is. An N 1 s peak corresponding to polymerized pyrrole species was also detected in the cases of LiY and NaY zeolites.