Selective oxidation of alcohols to aldehydes or ketones is a fundamental process in organic chemistry and the development of green and sustainable transformations are strongly required. Herein, we focused on the development of Ru-based catalysts deposited over ceria-zirconia supports (CZRu) for the solvent free oxidation of benzyl alcohol using air as oxidant, which is a cheap and safe process and meets to the atom economy and environment requirements. XPS characterization of the material reveals that the formation of RuO2 on the surface is necessary to achieve higher catalytic activity. The activity is strongly related to the reducibility of the material and to the close interaction between ceria-zirconia and RuO2, with the likely formation of Ru-O-Ce arrangements. The greater mobility of oxygen due to the formation of bridging oxygens in Ru-O-Ce and to the formation of superoxide species (O2−) over Ce3+ sites, significantly boosts the selective oxidation of alcohols. CZRu is a promising material with a remarkable 61% alcohol conversion at 90 °C without solvents; it also exhibits high activity (55% conversion) and complete selectivity (100%) for the selective oxidation of 1-phenylethanol to acetophenone. Overall, the formulation is among the most active reported so far under solvent free conditions and molecular oxygen. In addition, the reaction over CZRu exhibits an environmental factor (E-factor) lower than 1 (0.95) confirming the sustainability of the proposed process.
Solvent-free selective oxidation of benzyl alcohol using Ru loaded ceria-zirconia catalysts
Segato J.;Zuccaccia D.;Baratta W.;
2023-01-01
Abstract
Selective oxidation of alcohols to aldehydes or ketones is a fundamental process in organic chemistry and the development of green and sustainable transformations are strongly required. Herein, we focused on the development of Ru-based catalysts deposited over ceria-zirconia supports (CZRu) for the solvent free oxidation of benzyl alcohol using air as oxidant, which is a cheap and safe process and meets to the atom economy and environment requirements. XPS characterization of the material reveals that the formation of RuO2 on the surface is necessary to achieve higher catalytic activity. The activity is strongly related to the reducibility of the material and to the close interaction between ceria-zirconia and RuO2, with the likely formation of Ru-O-Ce arrangements. The greater mobility of oxygen due to the formation of bridging oxygens in Ru-O-Ce and to the formation of superoxide species (O2−) over Ce3+ sites, significantly boosts the selective oxidation of alcohols. CZRu is a promising material with a remarkable 61% alcohol conversion at 90 °C without solvents; it also exhibits high activity (55% conversion) and complete selectivity (100%) for the selective oxidation of 1-phenylethanol to acetophenone. Overall, the formulation is among the most active reported so far under solvent free conditions and molecular oxygen. In addition, the reaction over CZRu exhibits an environmental factor (E-factor) lower than 1 (0.95) confirming the sustainability of the proposed process.
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