Catalytic activity and some related spectral features of yttria-stabilisedcubic sulfated zirconia

Cubic sulfated zirconia (c-SZ) was prepared by sulfating phase-stabilised c -ZrO2. and its properties are compared with those of tetragonal (t-SZ) and monoclinic (m-SZ) systems. ZrO2 crystalline phases have been identified by XRD and, far more efficiently, by Raman spectroscopy. c-sZ exhibits better catalytic activity (n-butane isomerization at 423 K) than t-SZ, whereas m-S Z is virtually inactive. The better activity of c-SZ is not ascribable to c hanges of surface functionalities, but probably derives from a better stabi lization of the high symmetry crystalline form (i.e., from a more favourabl e distribution of surface sulfates among regular and defective crystal term inations).