Effect of metal oxide contents on the structure and performance of spray dried CrVO4/SiO2 catalysts for the ammoxidation of chlorotoluenes

Abstract 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.