Dehydrocyclization of n-octane over boron- and barium-doped V-Mg-O catalysts: influence of n-octane/oxygen ratios

Abstract

Boron- and barium-doped vanadium–magnesium oxide catalysts (BVMgO and BaVMgO) were synthesized by the wet impregnation method and were used for the oxidative dehydrogenation of n-octane at different n-octane/O2 molar ratios. The catalysts were characterized by ICP-OES, in situ XRD, 51V MAS NMR, SEM, EDX and TGA-DSC. The catalytic tests were carried out in a continuous flow fixed bed reactor. The incorporation of boron and barium as dopants into the VMgO system resulted in catalysts with some differences in properties, such as the details of phase transformations, porosity and degree of hydration. The catalytic performance was affected by the strength of the oxidative environment. Moreover, incorporation of barium enhanced the catalytic performance of VMgO, while the addition of boron adversely affected the performance of VMgO over all n-octane/O2 molar ratios with regard to both activity and oxidative dehydrogenation selectivity.