Hierarchical VAPO-5 Catalysts Prepared from Different Vanadium Sources in Fluoride Medium and Their Performance in Toluene Oxidation

Abstract Hierarchical VAPO-5 molecular sieves were prepared with different vanadium resources in the absence/presence of fluorine and characterized by XRD, SEM, N 2 adsorption-desorption, and NH 3 -TPD. The catalytic performances of hierarchical VAPO-5 molecular sieves were evaluated using toluene oxidation as the probe reaction and the corresponding mechanism was further proposed. The sample D-AFI-2(F) synthesized in a fluorine system with NH 4 VO 3 as metal sources show better catalytic performance than other samples in toluene oxidation, which is ascribed to the hierarchically porous structure and more acidic sites. The optimized condition of toluene oxidation was attained at the reaction temperature of 60°C, the reaction time of 5 h, the molar ratio of H 2 O 2 to toluene 2 : 1, the mass ratio of acetonitrile to toluene 6 : 1, and the mass ratio of catalyst to toluene 10%. In this case, the toluene conversion was 21.0%, and the selectivity of benzaldehyde, benzyl alcohol, and cresol was 43.3, 11.4, and 26.2%, respectively.