Generation of Strong Acid Sites on Yttrium-Doped Tetragonal ZrO2-Supported Tungsten Oxides: Effects of Dopant Amounts on Acidity, Crystalline Phase, Kinds of Tungsten Species, and Their Dispersion

A tungsten oxide catalysts supported on yttrium- or ytterbium-doped crystalline zirconium oxide (WOx/Y(Yb)-ZrO2) with different dopant concentrations but the same tungsten loadings and calcination temperatures were prepared to investigate the mechanism responsible for the strong solid acidity of so-called tungstated zirconia. The surface acid–base properties of WOx/Y(Yb)-ZrO2 and the support were characterized by catalyses of n-butane skeletal isomerization, alkylation of anisole with benzyl alcohol, and 2-butanol decomposition. The structural characterization and quantitative analysis were conducted by XRD, XAFS, and UV–Vis techniques. Crystalline zirconium oxides were effective as the starting material for tungsten–zirconium-based strong solid acid catalysts instead of amorphous Zr(OH)x if the crystalline form was tetragonal. Tetragonal-phase Y(Yb)-ZrO2 substitutional solid solutions with dopant concentrations of 3–5 mol % was a suitable support for stabilization of active small WO3 clusters. Tungsten s...