"Sulphated-ZrO2 prepared by impregnation with ammonium, sodium, or copper sulphate: catalytic activity for NO abatement with propene in the presence of oxygen"

Sulphated zirconia samples were prepared by impregnation of hydrous zirconia dried at 383 K or calcined at 823 K (monoclinic ZrO2) with aqueous solutions of (NH4)2SO4, Na2SO4, or CuSO4. After calcining at 823 K, samples prepared with hydrous zirconia dried at 383 K were tetragonal. At the same sulphate content, (NH4)2SO4/ZrO2 and CuSO4/ZrO2 contained sulphates of the same type. As the total sulphate content increased, IR indicated an increasing (polynuclear)/(mononuclear) sulphates ratio. (NH4)2SO4/ZrO2 and CuSO4/ZrO2 were both active for the abatement of NO with propene in the presence of oxygen. (NH4)2SO4/ZrO2 had several drawbacks: (i) CO formed in large amounts, (ii) N2O formed, (iii) the catalyst surface coked, and (iv) catalytic activity changed as a function of time on stream. CuSO4/ZrO2 catalysts had practically none of these unfavourable features. For a comparison, some catalytic experiments were also run using propane or methane as reducing agent.