Liquid-phase catalytic oxidation of p-chlorotoluene to p-chlorobenzaldehyde over manganese oxide octahedral molecular sieves

• MnO2 (OMS-2) is highly active for p-chlorotoluene liquid-phase partial oxidation.
• The catalyst also shows excellent recyclability and reusability.
• Catalytic activity is related to abundant lattice oxygen and high oxygen mobility.

Manganese oxide octahedral molecular sieves (OMS-2) show much higher catalytic activities in the liquid-phase catalytic oxidation of p-chlorotoluene than MnO2, Mn3O4, Mn(OAc)2 as well as than some other transition metal oxides such as Co2O3, V2O5 and Fe2O3. Based on temperature-programmed desorption and thermogravimetric results, it is deduced that the catalytic activity of OMS-2 can be ascribed to the abundance and mobility of lattice oxygen. We investigated the effects of reaction temperature, reaction time, catalyst amount, and initial water amount on the reaction. Under optimal reaction conditions, p-chlorotoluene conversion and p-chlorobenzaldehyde selectivity are respectively 86.0% and 68.7%. The catalysts can be easily recovered by centrifugation, and reused. According to the results of X-ray diffraction and N2 adsorption/desorption analyses, there is no significant change in major characteristics of the catalyst after 4 cycles of reaction.

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