Continuous flow synthesis of bimetallic AuPd catalysts for the selective oxidation of 5‐hydroxymethylfurfural to 2,5‐furandicarboxylic acid

The production of 2,5‐furandicarboxylic acid (FDCA) from the selective oxidation of 5‐hydroxymethylfurfural (HMF) is a critical step in the production of biopolymers from biomass‐derived materials. In this study, we report the catalytic performance of monometallic Au and Pd, and bimetallic AuPd nanoparticles with different Au:Pd molar ratios synthesised under continuous flow conditions using a millifluidic set‐up and subsequently deposited onto titanium dioxide as the chosen support. This synthetic technique provided a better control over mean particle size and metal alloy composition, that resulted in higher FDCA yield when the catalysts were compared to similar batch‐synthesised materials. A 99 % FDCA yield was obtained with the millifluidic‐prepared AuPd/TiO2 catalyst (Au:Pd molar composition of 75:25) after being calcined and reduced at 200 °C. The heat treatment caused a partial removal of the protective ligand (polyvinyl alcohol) encapsulating the nanoparticles and so induced stronger metal‐support interactions. The catalyst reusability was also tested, and showed limited particle sintering after five reaction cycles.