Cobalt and bismuth molybdates catalysts prepared by three different me
thods (coprecipitation, mechanical mixing and dispersion in n-pentane)
, have been studied by Laser Raman spectroscopy before and after testi
ng the catalysts in the selective oxidation of isobutene to methacrole
in. Raman bands ascribed to the component phases are observed in the s
pectra before test, while a phase transformation is detected after tes
t.