Oxidative Dehydrogenation of Isobutane to Isobutene on Metal-Doped MCM-41 Catalysts

Abstract

MCM-41 (#41 Mobil Composition of Matter) is a favorable material for heterogeneous reactions because of its unique porous structure. However, the catalytic activity of MCM-41 for the oxidative dehydrogenation (ODH) of isobutane to isobutene is known to be quite low. In the present study, a metal-doping method was employed to improve this catalytic activity. Doping of Cr, Co, Ni, or Mo into MCM-41 resulted in a great improvement in the catalytic activity. Since chromium-doped MCM-41 (Cr-MCM-41) showed the greatest catalytic activity among these catalysts, its redox property was further analyzed via XPS, XAFS and H₂-TPR techniques. The XPS spectrum of Cr-MCM-41 suggested that it has Cr³⁺ and Cr⁶⁺ species on its surface. Also, a pre-edge peak due to Cr⁶⁺ species was confirmed in the XANES spectrum of Cr-MCM-41. In H₂-TPR measurement, Cr-MCM-41 was more reducible than crystalline Cr₂O₃, which showed low catalytic activity for the ODH of isobutane. The reducible Cr⁶⁺ species on Cr-MCM-41 contributed to an improvement in the catalytic activity of MCM-41.