In situ FTIR studies on the conversion of methanol over acidic forms of various zeolites

In situ investigations of the interaction of methanol on zeolites of the faujasite, pentasil and mordenite types were performed. We suppose that CH₃)- or (CH₃)₂O… species exist on the surface of the H-ZSM-5 zeolite in the temperature range between 380 and 470 K which desorb above 470 K and form dimethyl ether (DME). The band at 1502 cm⁻¹ represents aromatics being intermediates in the aromatization of methanol. The band at 1595 cm⁻¹ is due to polymeric “coke” which cannot be removed from the zeolite up to 670 K. In the case of the H-Y zeolite no band at 1500 cm⁻¹ assigned to aromatics could be observed.