Oxidative dehydrogenation of isobutane on chromium oxide-based catalyst

Isobutane oxidative dehydrogenation offers a prospect of cheaper and environment friendly route to isobutene. The reaction has been studied at 250 °C, 1 atm and feed flow rate of 75 cm3/min over supported chromium oxide-based catalysts. Effects of various supports (Al2O3, MgO, TiO2 and SiO2), catalyst precursors (K2Cr2O7, CaCr2O7•H2O, CrO3, CrK(SO4)2•12H2O and Cr(NO3)3•9H2O) and binary mixed metal oxide catalysts of the form Cr-M-oxide/γ-Al2O3 (where M is V, Ni, Co, Mo, W, Ho, La, Li or Bi) were investigated. The supported catalysts are ranked (based on isobutene yields at 250 °C) as; Cr-Mg-O (3.4%) = Cr-Si-O (3.4%) < Cr-Ti-O (4.5%) < Cr-Al-O (6.0%). The performances of the catalysts showed strong dependence on the precursor used. The 10 wt.% Cr-Al-O prepared using K2Cr2O7 and CrK(SO4)2•2H2O exhibited the lowest isobutene yields of 0.14 and 0.3%, respectively. Partial substitution of chromium ions with nickel or tungsten exhibited minor increase in selectivity to isobutene of about 6% at comparable isobutane conversions. Substitution with other metals show similar or inferior performance compared with the base catalyst. Thus, showing that chromium oxide-based catalysts are active for the reaction and their performance could be improved by appropriate choice of active component precursor, support and additives.