IR STUDY OF NITROTOLUENE ADSORPTION ON OXIDE SURFACES

IR spectra of 4-nitrotoluene on silica, titania, zirconia, silica-alum ina, mordenite and sulfated zirconia, are reported. Ligation to Lewis acidic surface sites was the dominant mode of adsorption for all oxide s except silica for which hydrogen bonding between silanol groups and nitro groups occurred. Zirconia and sulfated zirconia catalysed the sl ow reductive dimerisation of adsorbates to the corresponding azoxybenz enes. There was no detectable IR evidence for adsorbate protonation, e ven for the highly acidic mordenite and sulfated zirconia surfaces. Co lour changes accompanying adsorption may not necessarily imply that pr otonation has occurred.