Alumina-supported chromium-based mixed-oxide catalysts in oxidative dehydrogenation of isobutane to isobutene

The effect of various metal additives on the catalytic performance of a chromium-based alumina-supported catalyst in oxidative dehydrogenation of isobutane was investigated in the low reaction temperature range 200–350 °C and at atmospheric pressure. Various parameters such as Cr wt.% in Cr–M–O system, different iC4H10:O2 ratios at a total flow rate of 75 cm3/min, and contact time on the activity and selectivity of the catalysts were varied in this study. For the binary catalysts, the addition of Co and Ni enhanced the overall activity while W and Mo improved the catalyst selectivity to iC4H8. The presence of V and Li deteriorated significantly the catalyst activity and selectivity. Increasing the percent of Cr in Cr–M–O increased iC4H10 and O2 conversion at the expense of selectivity. Tertiary systems such as Cr–W–Co–O, Cr–W–Ni–O and Cr–Ni–Co–O gave a much better overall performance compared with Cr–O alone. In particular, Cr–W–Co–O improved the overall activity of Cr–O catalyst by 17% while its iC4H8 selectivity improved by 15%. The low temperature activity of these catalysts makes them important candidates for further investigations.