CeO₂-TiO₂ catalyst prepared by physical mixing for NH₃ selective catalytic reduction: Evidence about the migration of sulfates from TiO₂ to CeO₂ via simple calcination

A mechanical mixture of CeO₂ and TiO₂ powder with a small amount of sulfate was applied for the selective catalytic reduction (SCR) of NO with NH₃. After calcination at 500 oC, the mixed sample showed significantly enhanced activity and selectivity compared to the uncalcined one and, moreover, demonstrated even higher activity than the conventional V₂O₅/TiO₂ catalyst above 300 °C. Combined characterization results revealed that the main active sites were newly formed sulfate species on CeO₂, the number of which increased with calcination. Temperatureresolved DRIFT spectra provided convincing evidence about the migration of sulfate species from TiO₂ to CeO₂, as confirmed from the shift of v(S=O) band as a result of the mechanical mixing and the subsequent calcination.