Valorization of Vanillyl Alcohol by Pigments: Prussian Blue Analogue as a Highly-Effective Heterogeneous Catalyst for Aerobic Oxidation of Vanillyl Alcohol to Vanillin

Abstract

Prussian blue analogues (PBA), a class of metal-coordinated frameworks, are proposed in this study for aerobic oxidation of a lignin model compound, vanillyl alcohol (VAL), to the valuable product, vanillin (VN). While different metals and hexacyano-metalates are used to prepare various PBAs, the prototype PBA (Fe3[Fe(CN)6]2 abbreviated as “FeFe”) exhibited the highest catalytic activity towards VAL conversion to VN. The kinetics of VAL conversion is determined and the production of VN is also analyzed using the pseudo first order rate law. In addition, FeFe exhibits the highest catalytic activity to convert VAL to VN with the highest production and selectivity compared to the reported heterogeneous catalysts. FeFe can be also re-used to catalyze conversion of VAL to VN without significant activity loss. These features indicate that FeFe, as an easy-to-obtain and non-toxic pigment, is a promising catalyst for aerobic oxidation of VAL.