The role of m-ZrO2 in the selective oxidation of ethanol to acetic acid employing PdO/m-ZrO2

• PdO/ZrO2 is active and selective for the generation of acetic acid from ethanol.
• m-ZrO2 works together with PdO generating a active system for ethanol oxidation.
• m-ZrO2 is more than a support as it shows active sites for acetic acid synthesis.

Catalysts based on Pd (0.6 wt.% of PdO) supported on ZrO2 and α-Al2O3 (powder and pellets) were prepared by impregnation. Their performances were evaluated in the oxidation of ethanol to acetic acid employing a Berty reactor. The N2 physisorption, H2 chemisorption, cyclohexane dehydrogenation reaction, temperature programmed reduction, UV–vis diffuse reflectance spectroscopy, temperature programmed desorption of ethanol and optical microscopy were employed to characterize these catalysts. The PdO/Al2O3 catalyst was used as a reference. It was verified that PdO/m-ZrO2 reaches high selectivity to acetic acid at high conversion. The PdO sites are the active ones for PdO/Al2O3, whereas in the case of PdO/m-ZrO2 catalyst both PdO and m-ZrO2 are in charge of this synthesis. The catalytic behavior of m-ZrO2 can be associated with the adsorption and spillover of the oxygenate species from this oxide to PdO and vice-versa. Moreover, the oxidation of acetaldehyde (intermediate of the reaction) occurs on PdO and also on m-ZrO2. The results show that m-ZrO2 is more than a support. Indeed, this oxide works together with PdO generating a very active system for ethanol oxidation to acetic acid.

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