Support for base-free: Pt supported on various activated carbon and carbon black materials was prepared and tested for the base-free, selective air-oxidation of 5-(Hydroxymethyl)furfural to 2,5-Furandicarboxylic acid. Depending on the chemical properties (graphitization degree, O-containing functional groups) of the supports as determined by comprehensive characterization, highly active and selective catalysts were found due to the active role of the support.

Abstract

The selective oxidation of 5-(Hydroxymethyl)furfural (HMF) to 2,5-Furandicarboxylic acid (FDCA) is highly attractive for the production of renewable monomers as substitute for fossil-based monomers. To achieve a sustainable synthesis, we report on advances for a base-free approach, reducing waste from the process, using air as oxidant and heterogeneous catalysts. Various Carbon-based supports, which can be bio-sourced and cost-efficient, for Pt particles were investigated as they allow for an easy reuse and at the end-of-life Pt can be recycled to enable a closed cycle. Commercially available supports with varying properties, which might replace the base, were studied with Pt particles of similar size and loading. Significant differences in the catalytic activity were observed, which were correlated with the O-functionalities and graphitization degree of the supports derived from Raman spectroscopy, temperature-programmed desorption, and X-ray photoelectron spectroscopy. An activated carbon (Norit ROX) rich in quinone/pyrone-type groups and a carbon black-based catalyst with graphene-layers pushed the efficiency with enhanced FDCA-yields enabling the complete substitution of the homogeneous base. This allows to circumvent the base in this process which together with high selectivity, air as oxidant, a reusable catalyst, and the use of bio-based feedstock contributes to the sustainability of the production of renewable monomers.