Conversion of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Au-based catalysts: Optimization of active phase and metal-support interaction

tIn the present work, a series of Au- and Au–Cu-containing catalysts based on different carriers such as TiO2and CeO2were studied with a view to increasing the activity and selectivity in 5-hydroxymethylfurfuraloxidation by optimizing the interaction both between the metals and with the support. The resultsobtained demonstrated the high activity in HMF oxidation of gold supported on ceria and titania. Never-theless, although the particle size of gold on both supports was comparable, Au/CeO2showed significantlyhigher activity than Au/TiO2, thus corroborating the theory that not only the gold particle size, but thesupport also, plays a key role in HMF oxidation in the aqueous phase. Indeed, pre-made uniform nanopar-ticles, used for catalyst preparation, were surface-bound by poly(N-vinyl-2-pyrrolidone) – the stabilizerused during nanoparticle synthesis – whose presence proved to prevent the interaction of active phaseswith CeO2, while worsening the catalytic activity of both monometallic and bimetallic systems. Thepre-treatment of the prepared catalysts was necessary to activate the materials, by maximizing the con-tact between the metal and the support and thus suggesting an important role of the ceria defects on5-hydroxymethylfurfural oxidation to 2,5-furandicarboxylic acid.