Structural effect of tungsten oxides on selective oxidation of cyclopentene to glutaraldehyde

Tungsten oxides with different chemical structures, such as hydrated tungsten oxide (WO3 · H2O or WO3 · 0.33H2O), tungstic acid hydrate (H2WO4 · H2O), and amorphous tungsten oxide, were prepared starting from ammonium tungstate and using nitric, hydrochloric, acetic, and sulfuric acids as precipitating reagents, respectively. Amorphous and less hydrated tungsten oxides exhibited higher catalytic activities than tungstic acid hydrate and tungsten oxide monohydrate did in the catalytic oxidation of cyclopentene to glutaraldehyde with aqueous H2O2. The weak interaction between H2O2 and amorphous or less hydrated tungsten oxide was beneficial to the formation of glutaraldehyde.