The oxidative aromatization of n-hexane over VMgO catalysts

Abstract

Vanadium magnesium oxide (VMgO) catalysts with different vanadium loadings were synthesized and tested for catalytic activity in the oxidative dehydrogenation of n-hexane. High surface area catalysts were obtained by the wet impregnation technique. Magnesium oxide (MgO) and magnesium orthovanadate [Mg3(VO4)2] were the only phases observed in each catalyst. All the catalysts were tested at 0.6–7.8 % of n-hexane in air within a temperature range of 350–550 °C, varying the gas hourly space velocities. Catalytic testing conducted below the lower flammability limit (0.6 % n-hexane in air) showed only benzene and carbon oxides in the product stream, whereas for experiments done above the upper flammability limit (7.8 % n-hexane in air), hexenes, in addition to benzene and carbon oxides were observed. Decreasing the feed composition from 7.8 to 5.5 % resulted in higher yields towards benzene and total dehydrogenated products. The effect of variations in the gas hourly space velocity investigated using the 19 wt% vanadium catalyst and a feed concentration of 7.8 % showed that the selectivity to benzene increased slightly with an increase in the gas hourly space velocity.