Titania-magnesia mixed oxides, with magnesia concentrations between 10 and
90 wt %, were prepared by using the sol-gel method with titanium n-butoxide
and magnesium ethoxide as precursors. The mixed oxides were characterized
with X-ray powder diffraction, BET nitrogen adsorption isotherms, electron
spin resonance (ESR), and by testing their catalytic activity for 2-propano
l and a-butanol. dehydration. Samples contained periclase, anatase, karooit
e (MgTi2O5), geikielite (MgTiO3), and qandilite (Mg2TiO4) The BET specific
surface area varied with magnesia concentration; the samples with 50 wt % M
gO had the highest area, 211 m(2)/g. Samples had paramagnetic centers that
produced complex ESR spectra when many crystalline phases coexisted. For 2-
propanol and 2-butanol decomposition, the activity and selectivity patterns
of the mixed oxides were substantially different to those observed in pure
TiO2 and pure MgO. This singular behavior should be a result of the struct
ural defects created by the substitution of Mg2+ ions by Ti4+ cations in ti
tania lattice, as well as by the interfaces created when several crystallin
e phases coexisted.