Catalytic oxidation of toluene over manganese oxide octahedral molecular sieves (OMS-2) synthesized by different methods

Manganese oxide octahedral molecular sieves (OMS-2) catalysts for the catalytic oxidation of toluene were prepared by a solid-state reaction and a refluxing method. The effect of the synthesis method on the catalytic activity was investigated. XRD patterns revealed that both OMS-2 materials had the typical cryptomelane-type structure. OMS-2 by the refluxing method exhibited the higher catalytic activity than that by the solid-state reaction method, on which the complete oxidation of toluene was achieved at 240 degrees C. According to the results of temperature programmed desorption (TPD) and thermogravimetric analysis (TGA), it was apparent that more available lattice oxygen and higher oxygen mobility were attributed to the catalytic activity of OMS-2 from the refluxing method. Furthermore, OMS-2 pretreated at 250 degrees C exhibited the best catalytic performance and good stability for toluene oxidation without the coke formation during 30 h. (C) 2011 Elsevier B.V. All rights reserved.