The Role of V-Species and O-Species on Controlled-Hydrogen-Reduction VOx Surfaces in Cyclohexane Oxidation

A series of controlled-hydrogen-reduction VOx (CHR-VOx) were prepared after our controllable hydrogen treatment, and CHR-VOx were controlled to be reduced to the states dominated by V5+ and V4+ species, subsequently the catalytic roles of V-species and O-species for cyclohexane (CHA) oxidation were explored. As expected, the surface properties of CHR-VOx have occurred remarkable change resulting in a significantly improvement on catalytic performance determined by V-species and O-species. The reduction behavior of the properties was recognized by XPS and Raman. Generally, the moderate-reduced CHR-VOx which possessed most 78.7 % multi-liganded-oxygen (O-L) performed the best conversion for CHA (11.8 %), and the over-reduced CHR-VOx with a large content of V4+ species (33 %) performed a best selectivity for adipic acid (44.3 %). In this case, O-L sites were regarded as the active site to accelerate the activation of CHA, while V4+ species were regarded as the oxygen vacancies (OVs) through V4+-OV to contribute to the further oxidation to adipic acid.