Extraframework Fe-Al-O species occluded in MFI zeolite as the active species in the oxidation of benzene to phenol with nitrous oxide

Iron and aluminum are required for the formation of active sites in MFI-type zeolites for benzene oxidation to phenol by nitrous oxide. We propose that the active species are extraframework Fe---Al---O species. These species produce characteristic IR bands around 1625 and 1635 cm-1 after exposure to NO which are different from those found in Fe-substituted silicalite-1 and HZSM-5. While we only observe negligible benzene oxidation activities for these latter materials, a MFI zeolite containing Fe and Al shows good performance. Additionally, we found that postsynthesis dispersion of aluminum to Fe-substituted silicalite-1 offers an alternative preparation route to an active material.