Abstract
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 cm 3/min over supported chromium oxide-based catalysts. Effects of various supports (Al 2O 3, MgO, TiO 2 and SiO 2), catalyst precursors (K 2Cr 2O 7, CaCr 2O 7·H 2O, CrO 3, CrK(SO 4) 2·12H 2O and Cr(NO 3) 3·9H 2O) and binary mixed metal oxide catalysts of the form Cr-M-oxide/γ-Al 2O 3 (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 K 2Cr 2O 7 and CrK(SO 4) 2·2H 2O 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.
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More From: Chemical Engineering & Processing: Process Intensification
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