Multiphase W–V–Hf-Ta Mixed-Metal Oxides for Catalytic Oxidation of Toluene

Multiphase mixed-metal oxides (MMOs) containing W, V, Hf, Ta, and either Fe or Ti were synthesized by coprecipitation and evaluated as catalysts for toluene oxidation. Structural analysis determined the formation of multiphase crystalline systems, while energy-dispersive X-ray spectroscopy pointed out to homogeneous elemental distribution. X-ray photoelectron spectroscopy confirmed that all elements are present in oxidized states, consistent with the formation of mixed-metal oxides. The catalytic activity of the prepared MMO was tested in a fixed-bed reactor in the toluene degradation process. A one-dimensional pseudohomogeneous model assuming first-order kinetics successfully described the experimental data. The Ti-containing catalyst showed slightly higher activity, achieving a lower toluene removal temperature and having a lower activation energy (139.27 kJ mol–1) in comparison to the Fe-containing catalyst (145.41 kJ mol–1). The obtained results demonstrate that the investigated multiphase MMOs are promising candidates for volatile organic compounds removal.