Oxidative Dehydrogenation of Propane to Propylene over Mesoporous Alumina Supported Ni-Co Oxide Catalysts

Abstract

A series of mesoporous alumina supported nickel oxide, cobalt oxide, and bimetallic nickel-cobalt oxide catalysts were synthesized by a one-pot method, using nonionic triblock copolymer as a template and aluminum isopropoxide as the source of aluminum. For comparison, an additional supported Ni-Co oxide catalyst was prepared by impregnation, using mesoporous alumina as the support. The catalysts were tested for the oxidative dehydrogenation of propane, and their structure and properties were characterized by N-2 adsorption-desorption, high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), temperature-programmed H-2 reduction (H-2-TFR), and laser Raman spectroscopy (LRS). All samples synthesized by the one-pot method had large surface area, highly ordered mesoporous structure, and highly dispersed supported oxide species. However, in the sample prepared by impregnation, the mesostructure of the carrier was destroyed with the formation of Co3O4 phase. Among the catalysts studied, the mesoporous alumina supported Ni-Co oxide catalyst from one-pot synthesis showed the best catalytic performance for propane oxidation to propylene. On this catalyst a 10.3% propylene yield was obtained at 450 degrees C, C3H8:O-2:N-2 molar ratio of 1:1:4, and gas hourly space velocity (GHSV) of 10000 mL.h(-1).g(-1). This result was much higher than the yield of 2.4% obtained from the catalyst prepared by impregnation. Combining the results of characterization and catalytic reaction, the relationship between structure and performance of the catalysts was discussed. The large difference observed in catalytic performance between catalysts prepared by one-pot and impregnation methods was attributed to their different structures, including textural structure, and dispersion of the supported metal oxide species.