Oxidative dehydrogenation of n-octane using vanadium-based hydrotalcite-like compounds.

Abstract

The oxidative dehydrogenation of alkanes provides a potential route to higher value products such as olefins and aromatic compounds. Alkanes are of low environmental impact and their increasing availability has prompted extensive research in the field of alkane activation. The use of hydrotalcite-type compounds (HTlc), to achieve such reactions, has received much attention over recent years. Specifically, hydrotalcites and hydrotalcite-like compounds are promising catalysts because they provide a route to mixed-metal oxides with variable composition and significantly high metal-oxide distribution. Vanadium containing hydrotalcite-like catalysts were synthesized via the co-precipitation route and doped with either barium, cesium or boron using the wet impregnation method. These catalysts were characterized using electron microscopy, inductively coupled plasma - optical emission spectroscopy, X-Ray diffraction, differential thermal analysis, BET surface area measurements and infrared spectroscopy. The catalysts were then tested in a fixed bed reactor using n-octane as the feed and air as the oxidant. The effect of fuel-air ratios and contact time was studied on the unpromoted Mg-V-HTlc. The conversion of n-octane and the selectivity and yields to the products were quantified using gas chromatography and used to determine optimum reaction conditions. The effect of promoters on the conversion of n-octane and the selectivity of the catalyst in terms of products was determined under the optimum reaction conditions.