Influence of vanadium in iron-based zeolites and silicalites in oxidation of n-octane to C-8 oxygenates

Abstract

Modified ZSM-5 and silicalites catalysts were prepared to evaluate the influence of vanadium in a bimetallic system (V, Fe) using the sol-gel [1.7Fe-silicalite, 1.8V-silicalite, 0.9Fe0.8V-silicalite and 0.3Fe1.3V-silicalite] and ionic exchange [1.6Fe-ZSM-5(IE), 1.7V-ZSM-5(IE), 1.1Fe0.8V-ZSM-5(IE) and 0.4Fe1.2V-ZSM-5(IE)] methods. Powder XRDoutcomes displayed that a single phase of ZSM-5 was obtained for all the prepared catalysts. All synthesized catalysts were used in the activation of n-octane via oxidation with H₂O₂ as the oxidant in MeCN at 80 °C. Only C8 oxygenate products were obtained. The introduction of vanadium to the Fe-ZSM-5 catalyst via ion exchange enhanced the conversion, while the terminal selectivity was reduced. However, for the silicalite catalysts, there was no relationship observed from the introduction of vanadium to the Fe-silicalite with respect to the terminal selectivity. The highest conversion achieved was 6.6 % with selectivity to terminal oxygenates of 12 % using 1.7V-ZSM-5(IE) and the highest terminal selectivity achieved was 31%at a conversion of 1.7%using 1.7Fe-ZSM-5(IE). In contrast to the two above mentionedZSM-5catalysts, 1.8V-silicalite gave the highest terminal selectivity of 22%and the lowest conversion of 1.5 %, while 1.6Fe-silicalite gave the highest conversion of 2.9 % with relatively low terminal selectivity of 17 %.