The interaction of Pt and SbOx in the selective oxidation of isobutylene to methacrolein Original Research Article

New Pt/SbOx catalysts active for the selective oxidation of iso-C4H10 and iso-C4H8 to methacrolein were investigated by pulse reactivity measurements, X-ray diffraction (XRD) analysis, and Raman spectroscopy. XRD revealed that the main oxide phase in Pt/SbOx catalysts after calcination or reaction condition was Sb6O13 whereas Raman spectroscopy also showed the presence of Sb2O3 (senarmontite). As a result of the interaction between Pt and SbOx the total oxidation chemistry of Pt was shut down, and instead a selective oxidation behavior appeared. Investigation of iso-C4H8 oxidation by lattice oxygen in Pt/SbOx revealed that Pt was essential for SbOx to undergo redox cycles, and that without Pt, not much SbOx was reoxidized under reaction conditions. The overall results were consistent with small Sb2O3 oxide crystallites forming on or around Pt particles, with small highly dispersed antimony species, possibly O=SbOy decorating the surface. These species were responsible for breaking up large Pt ensembles and suppressing the total oxidation reaction.