SPECTROSCOPIC EVIDENCE FOR THE FORMATION OF CARBENIUM IONS ON H-ZSM-5ZEOLITES

The formation of alkenyl and alkylaromatic cations from methanol, olef in, diene and compounds with a single aromatic ring on H-ZSM-5 zeolite s has been detected using IR and UV-Vis spectroscopy. The formation of alkenyl cations can be characterized reliably by the appearance of nu (CCC)as bands at 1490-1530 cm-1 in IR spectra and bands at 290-310 (al lyl), 350-380 (dienyl) and 430-450 (trienyl cations) nm in UV-Vis spec tra. The formation of alkylaromatic cations can be characterized by th e appearance of stretching vibrations of the aromatic ring at 1500 and 1600 cm-1 and bands at 320-330 and 400-440 nm, taking into account th e thermal stability of surface complexes.