Selective oxidation of p-chlorotoluene to p-chlorobenzaldehyde with molecular oxygen over zirconium-doped manganese oxide materials

• Zr-OMS-2 is highly active for p-chlorotoluene liquid-phase partial oxidation.
• 86% selectivity along with 79.6% yield to p-chlorobenzaldehyd was obtained.
• As a clean oxidation, oxygen is employed in the reaction.
• The catalyst also shows excellent recyclability and reusability.

Nano-fibrous zirconium-doped manganese oxide octahedral molecular sieves (denoted as Zr-OMS-2) were prepared and characterized by XRD, SEM, EDXS, FTIR, NH3-TPD, and N2 adsorption-desorption techniques. The materials were used as catalysts for liquid-phase aerobic oxidation of p-chlorotoluene to p-chlorobenzaldehyde. The Zr-OMS-2 catalysts show much higher catalytic activities than OMS-2, and the Zr-OMS-2 with 6 wt% Zr content shows the highest activity, giving approximately 93% p-chlorotoluene conversion and 86% p-chlorobenzaldehyde selectivity in 10 h at 100 °C. The promotion effect of Zr is deduced to be related with the suitable acidity and the enhancement of specific surface area. In addition, effects of reaction parameters such as catalyst amount, oxygen flow, temperature and time were studied.

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