Effect of Metal Oxide Contents on the Structure and Performance of Spray Dried CrVO4/SiO2 Catalysts for the Ammoxidation of Chlorotoluenes

This work aims at developing a customized ammoxidation catalyst through optimizing the metal oxide content in CrVO4/SiO2 catalysts. Various amounts of Cr-V-O with 1:1 molar ratio of Cr/V were successfully loaded on SiO2 via spray drying method with colloidal silica as the binder. Polarized light microscope (PLM) illustrated that the CrVO4/SiO2 particles presented as well dispersed microspheres in the micro size (20-80 μm). X-ray diffraction spectroscopy (XRD) confirmed the formation of monoclinic CrVO4 phase wherein the metal oxide content was ranged from 30 to 70 weight percent. FT-IR spectra indicated that the introduction of metal oxide had no obvious effects on the skeletal structure of SiO2. X-ray photoelectron spectroscopy (XPS) analysis revealed that the valence state of V and Cr was hardly affected with increasing the metal oxide content. Performances of the obtained CrVO4/SiO2 catalysts with different metal oxide contents were investigated via the ammoxidation of a model compound namely; para-chlorotoluene. As a result of catalytic test, the CrVO4/SiO2 catalyst with 60% metal oxide content exhibited the best catalytic performance. In addition, this catalyst was an efficient and selective catalyst toward ammoxidation reactions of toluene, ortho- and meta-chlorotoluenes.