Continuous Flow: etherification of Bio-Based Furanic Compounds

The ultimate goal of the Biorefinery is to move away from a fossil-based business towards a more sustainable industry centred on the use of renewable feedstocks, capable of respecting the principle of the circular economy[1,2]. In this perspective, the so-called Bio-Based Platform Chemicals play an important role. Among them, 5-hydroxymethylfurfural (HMF) and 2,5-bis(hydroxymethyl)furan (BHMF) - achieved by HMF hydrogenation - are two of the most studied representatives. The etherification of these molecules with different alcohols yields 5-(alkoxymethyl)furfurals (AMFs) and 2,5-bis(alkoxymethyl) furans (BAMFs) respectively, both demonstrating potential application as fuel additives [3]. In addition, HMF, when subjected to self-etherification, leads to 5,5′-[oxybis(methylene)]bis-2-furfural (OBMF), another bio-based monomer of growing interest [4]. The presented work focuses on the etherification of HMF and BHMF promoted by a commercially available ion exchange resin - Purolite CT275DR, using a continuous flow apparatus. The reaction conditions were optimized by evaluating key parameters, including catalyst type and quantity, reaction media, temperature, and flow rate for the etherification of BHMF with ethanol and then extended to achieve a library of BAMFs. HMF self-etherification to form OBMF was conducted in the presence of both heterogeneous (CT275DR) and homogeneous acid (methanesulfonic acid - MSA) catalysts using dimethyl carbonate (DMC) as green solvent, with the latter being the most effective. Finally green metrics were calculated for the optimized etherification of BHMF with ethanol and the values were compared to previously published procedures.