Temperature-programmed desorption study of molecular oxygen adsorbed on MFI-type zeolites

Abstract

The adsorption of molecular oxygen at room temperature on the proton form of MFI zeolites with different Si/Al ratios has been investigated by temperature-programmed desorption (TPD). The internal Si-OH defects (silanol groups) in these zeolites are found to serve as O-2 adsorption sites. The apparent activation energies (17.5-21.8 kcal . mol(-1)) of desorption determined from O-2 TPD measurements reveal that the extent of interactions between the Si-OH defects and the adsorbed O-2 molecules becomes weaker with decreasing Al content in the zeolite.