Effect of Nb on catalyst nanoparticle sizes and catalytic activities of H₂O₂-mediated oxidative dehydrogenation of C_α–OH lignin model compounds

Nb-modified Mo–V–Nb tri-component oxides were synthesized for catalytic oxidative dehydrogenation of C_α–OH lignin model compounds. Nb–O octahedron as the nucleation center refined the Mo–V–Nb oxide particles with TiO₂ as the support and changed the selective oxidation performance of the catalyst to a certain extent. However, the conversion of C_α–OH lignin model compounds was significantly reduced under the catalysis of Mo–V–Nb–O with too much Nb content. The experimental results showed that the effect of Nb in the three-component oxides not only reduced the crystal size of the catalyst, but also more importantly adjusted the valence state of vanadium. The valence state of vanadium in vanadyl octahedron formed based on Nb nucleation center was adjusted. The ratio between tetravalent vanadium and pentavalent vanadium was directly proportional to the conversion rate. The catalytic mechanism was that there were oxygen vacancies at the catalytic active sites of V⁴⁺, which provided a basis for the generation of reactive oxygen species in the oxidative dehydrogenation reaction.