Palladium on Zirconia-Titania Catalyst for Reductive Amination of Furfural

[EN] The valorisation of furfural through reductive amination is a sustainable alternative for producing secondary aromatic amines; however, this process holds relevant scientific challenges associated to reaction conditions, catalytic materials as well as on the understanding of reaction mechanisms. This study systematically investigates the effect of the solvent and N-substrates nature on the reductive amination of furfural using a bifunctional palladium on zirconia-titania catalyst. The catalyst presented an anatase titania phase, high palladium dispersion (22%) and a predominance of weak Lewis's acid sites. The solvent screening demonstrated that methanol provided a balance of hydrogen-bonding ability and dielectric constant, which favour hydrogen dissociation at metal sites and imine adsorption at acid sites, thus favouring N-furfurylaniline selectivity. Among the tested substrates the 3-fluoroaniline resulted in the highest yield and selectivity to secondary amine N-furfurylaniline (Y FFA = 76%; S FFA = 82%), due to increased electrophilicity of the C=N group, while ortho substituents generated hysteric hindrance, limiting N-furfurylaniline formation. These findings could contribute to the rational design of catalysts and the selection of more suitable reaction systems for the reductive amination of furfural.