ON THE ADSORPTION AND SURFACE-REACTIONS OF NITROBENZENE AND NITROSOBENZENE ON OXIDES - AN IR STUDY

Selective catalytic reduction of nitrobenzene to nitrosobenzene is a useful way to prepare the latter compound by a waste-free (lean) process. Since very little is known about the selective removal of oxygen from oxygen-containing compounds, surface reactions of nitro- and nitrosobenzene have been studied, here on SiO2, γ-Al2O3, and α-Mn3O4 by Fourier transform infrared spectroscopy and by mass spectrometry. α-Mn3O4 is the most active catalyst for the selective reduction of nitrobenzene. However, the study has been extended to SiO2 and γ-Al2O3, which are not active in a steady-state reaction, and the results obtained with the latter two oxides are used to better understand the adsorption and reactions on α-Mn3O4. On SiO2 only weak adsorption of nitro- and nitrosocompounds is observed. On γ-Al2O3 complex surface reactions are observed, with products not very different from those on α-Mn3O4. However, it is argued that the redox mechanism (i.e., a mechanism involving the lattice oxygen) operates on α-Mn3O4, since this is the only oxide from the three mentioned before which produces nitrosobenzene. The IR spectra of adsorbed species on surfaces heated to 573 K indicate that the steady-state reaction runs on a surface covered by a complex mixture of adsorbed species. © 1993 Academic Press, Inc.