Synthesis and characterization of Zn-modified MnCO3 catalysts for application in aromatic alcohol oxidation

PABLO J. LUGGREN; JUAN ZELIN; HERNÁN DUARTE; MARÍA EUGENIA SAD; VERONICA DIEZ; J. ISABEL DI COSIMO

Santa Fe

Workshop; French Argentinean Workshop on Heterogeneous Catalysis; 2023

Benzaldehyde (B) is an important intermediate widely used in pharmaceutical, dye, food,perfumery and agrochemical industries. Traditional synthesis of aldehydes via alcoholoxidation implies methods involving toxic homogeneous catalysts such as chromium(VI)-basedreactants or nitric acid and inorganic oxidants (H2O2, dimethyl sulfoxide, permanganates), withthe consequent environmental concerns because of disposal issues. The use of solid catalystsand O2 overcome the problems associated with traditional processes, the catalyst may berecovered and reused. Both noble and non-noble metal catalysts have been tested in oxidationreactions. In recent years, much attention has been paid to MnCO3 because of its accessiblecost and abundance in nature. Thus, MnCO3, MnO2, Mn2O3 and Mn3O4 have been shown tobe active and selective to aldehyde formation by alcohol oxidation because their redoxproperties. The catalytic activity of these materials is usually improved by adding promoterssuch as ZnO, CeO2, CuO and Fe2O3. It was previously reported that the promoter nature aswell as catalyst synthesis method can strongly influence the solid particle size and the surface,structural and redox properties of the Mn species [1,2]. In this work, we focus on the synthesisand characterization of Zn-modified MnCO3 solids. The evolution of the solid physicochemicalproperties such as Mn oxidation state changes and the development of different surface andtridimensional Mn and/or Zn containing species upon increasing the Zn content was elucidated.The knowledge acquired from solid characterization allowed us to interpret results obtainedduring selective liquid-phase oxidation of benzyl alcohol (BA) using O2 as oxidant.