The oxidative dehydrogenation of n-Hexane and n-Octane over vanadium magnesium oxide catalysts.

Abstract

Vanadium magnesium oxide (VMgO) catalysts with different vanadium loadings were synthesized and tested for catalytic activity using pure «-hexane and «-octane as feeds. High surface area catalysts were obtained by the wet impregnation of magnesium oxide with an aqueous ammonium metavanadate solution. The optimum loading of vanadium was shown to be 19 % (calculated as weight % of V205). Catalysts were characterized by x-ray diffraction (XRD), inductively coupled plasma - atomic emission spectroscopy (ICP-AES), Brunauer-Emmet-Teller (BET) surface area, differential scanning calorimetry - thermogravimetric analysis (DSC-TGA), Fourier transform infrared spectroscopy (FTIR), laser Raman spectroscopy (LRS), x-ray induced photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM). Magnesium oxide (MgO) and magnesium orthovanadate (Mg3(V04)2 were the only phases observed in each catalyst. VMgO catalysts were tested under both oxygen-rich and oxygen-lean conditions. «-Hexane as feed yielded benzene, 1-hexene, 2-hexene, propane, propene, carbon oxides and water as products, n- Octane as feed yielded styrene, ethylbenzene, xylene, benzene, octenes, carbon oxides and water. 19VMgO was promoted with different loadings of molybdenum oxide (M0O3), cesium oxide (Cs20), antimony oxide (Sb20s), niobium oxide (Nb205), bismuth oxide (Bi203) and tellurium oxide (Te02). The promoted catalysts were tested in specially designed and constructed parallel fixed bed continuous flow reactors.