Pushing the Efficiency of the Selective and Base‐Free Air‐Oxidation of HMF by Varying the Properties of Carbon‐Based Supports

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.

Continuous flow oxidation of HMF using a supported AuPd-alloy

“…Nevertheless, AC-ROX was shown in the literature to play an active role in the base-free HMF-oxidation, possessing good adsorption properties for HMF, which potentially increases the catalytic activity in continuous flow oxidation under alkaline conditions. 51…”

“…This proves the superior intrinsic catalytic activity of AuPd/AC-ROX over a broad LHSV range. The higher catalytic activity might originate from the superior adsorption properties of AC-ROX, 51 particularly for HMF, which was not adsorbed on the surfaces of TiO 2 and ZrO 2 (Table S2†). AC-ROX thus proved to be the most suitable support material for further testing, offering the potential to enhance the productivity of FDCA further.…”