C. Morterra et al., CRYSTAL PHASE, SPECTRAL FEATURES, AND CATALYTIC ACTIVITY OF SULFATE-DOPED ZIRCONIA SYSTEMS, Journal of catalysis, 157(1), 1995, pp. 109-123
Several sulfate-doped ZrO2 catalysts (s.d.-ZrO2) have been prepared by
sulfating, with either sulfuric acid or ammonium sulfate, samples of
monoclinic ZrO2, Y2O3-stabilized tetragonal ZrO2, and amorphous Zr hyd
roxide, and by calcining the sulfated precursors at T greater than or
equal to 673 K. We then examined (by TEM, XRD, FTIR, and catalytic tes
ts) the effect of sulfation on ZrO2 crystal phase and morphology, the
effect of ZrO2 crystal phase on the spectroscopic features of the surf
ace sulfate groups, and the catalytic behaviour of the three families
of s.d.-ZrO2 systems in the isomerization of n-butane. It could be con
cluded that the sulfated monoclinic ZrO2 phase is catalytically not ve
ry active (if at all), the nonstabilized tetragonal ZrO2 phase is unst
able to the sulfation process, and the sulfated tetragonal ZrO2 phase
is catalytically active, no matter what the preparative route has been
, provided that the sulfated system is calcined at T greater than or e
qual to 823 K. The latter condition is discussed in terms of the struc
tural and spectroscopic features of the surface sulfate layer. (C) 199
5 Academic Press, Inc.