Controlled Synthesis of Spherical Vanadium–Phosphorus Composite Oxides With Glucose Additive and the Excellent Performance for Ammoxidation of 2,6-Dichlorotoluene

Controlled synthesis of catalysts with a regulated structure has attracted a great deal of interest in the field of heterogeneous catalysis research. In this study, microporous spherical vanadium–phosphorus (VPO) composite oxide catalysts were successfully fabricated through a hydrothermal method with glucose as the assisting agent. The catalysts were characterized using XRD, SEM, TEM, FT-IR, XPS, BET, H 2 -TPR, NH 3 -TPD, and N 2 adsorption–desorption measurements. It was found that the morphology and structure of the as-obtained VPO_G x catalysts were strongly influenced by the amount of glucose used during the synthesis process. All VPO_G x catalysts exhibited a pure orthorhombic VOPO 4 phase regardless of the presence or absence of glucose. The VPO_G 0 catalyst, synthesized without the addition of glucose, consisted of irregular micron-sized particles lacking surface pores. In contrast, the VPO_G 0.5 catalyst, prepared with glucose addition at a 0.5 molar ratio of C 6 H 12 O 6 to V 2 O 5 , formed nearly uniform porous microspheres with an approximate size of 20 μm. Compared with the VPO_G 0 catalyst, the VPO_G 0.5 catalyst displayed the lowest crystallinity of the VOPO 4 phase, accompanied by a 20-fold enhancement in a specific surface area and a fivefold increase in pore volume. Moreover, the VPO_G 0.5 catalyst demonstrated an almost 90°C lower reduction temperature for pentavalent vanadium and possessed nearly 10 times the amount of total acidic sites. Simultaneously, it exhibited a high stability in morphology and structure. These modifications collectively played a crucial role in enhancing the catalytic performance. As a result, the VPO_G 0.5 catalyst exhibited optimal catalytic activity and selectivity for the ammoxidation of 2,6-dichlorotoluene to 2,6-dichlorobenzonitrile when compared with the VPO_G 0 and other VPO_G x catalysts. Specifically, it reached a nearly 10% increase in yield and a 5% increase in selectivity relative to the VPO_G 0 catalyst. The VPO_G 0.5 catalyst was one of the most active catalysts among all reported VPO composite oxides.