Adsorption of pyrrole derivatives in alkali metal cation-exchanged faujasites: comparative studies by surface vibrational techniques, X-ray diffraction and temperature-programmed desorption augmented with theoretical studies Part II. Methylated pyrrole derivatives as probe molecules

Abstract

The nature and strength of interaction of methylated pyrrole derivatives (N-methylpyrrole, 2-methylpyrrole and 2,5-dimethylpyrrole) adsorbed in alkali metal cation-exchanged faujasites have been investigated by the joint use of temperature-programmed desorption (TPD), infrared spectroscopy and X-ray diffraction accompanied by quantum mechanical studies. It was found that successive methylation of pyrrole leads to an enhancement of the electron donor properties by which the effective strength of interaction can be subtly tuned. However, a complex adsorption behaviour dependent on the kind of cation, the degree of ion exchange and the Si/Al ratio of the zeolites was observed. The results indicate that obviously different kinds of interaction occur simultaneously. To discriminate between different adsorption sites of the probes the experimentally obtained results were verified by quantum mechanical abinitio calculations.