Effect of supports on the structure and activity of vanadium-chromium oxide catalysts for ammoxidation of 3-picoline

Abstract

Bulk and Nb 2 O 5 -, MgF 2 -, TiO 2 -, and SiO 2 -supported vanadium-chromium oxide catalysts were prepared by the incipient wetness impregnation method and investigated for the ammoxidation of 3-picoline to nicotinonitrile at 310–400 °C. The physical and chemical properties of the catalysts were assessed by X-ray diffraction, N 2 adsorption-desorption, H 2 -temperature-programmed reduction, and NH 3 -temperature-programmed desorption. The surface area of the supports influenced the formation of the active components of the catalysts: high surface area encouraged the formation of monoclinic CrVO 4 whereas low surface area favored the formation of orthorhombic CrVO 4 . The high reducibility of vanadium in the catalyst and the large number of surface active sites resulted in higher 3-picoline conversion efficiencies. The high selectivity was attributed to the low surface acidity of the catalysts. Reaction temperature showed a positive effect on the catalytic performance for it could increase 3-picoline conversion and maintain nicotinonitrile selectivity. Highly efficient vanadium-chromium oxide catalysts for ammoxidation of 3-picoline have been prepared. The acidity and reducibility had great influence on the catalytic activity and selectivity.