Is mechanochemical activation always an asset? The case of Pd/CeO2 catalysts for glycerol selective oxidation

Abstract

Mechanochemical activation was assessed using Pd-based catalysts supported on high-energy ball milled ceria. By means of different milling conditions, improved physicochemical properties were achieved, including defects introduction, surface area increase and redox development that remained even after palladium impregnation and thermal steps of synthesis. Furthermore, palladium particles were effectively added to supports’ surface in small metal domains with Pd0 predominance. Strong metal-support interaction was also attained, including the formation of Pd–O–Ce solid solutions and interfacial sites. However, distinctive acid-base properties and oxygen vacancies achieved in the supports were at certain degree lost during catalysts preparation, having a main impact on catalytic activity. Glycerol selective oxidation tests showed an unexpected catalytic behavior for Ce5002 support by itself, achieved by a simple mechanochemical activation, and comparable to Pd/Ce00 catalyst. Therefore, high-energy ball milling gives new approaches of design for catalysts and robust supports that can act as catalysts by themselves.