Biomass to plastics: From HMF to fructose for the synthesis of 2,5-furandicarboxylic acid over Au/TiO2

Abstract

This study focuses on the catalytic synthesis of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF). The influences of temperature, O₂ pressure, initial HMF concentration (i.e., catalytic loading), and NaOH:HMF ratio are studied. A minimum temperature is required to promote oxidation, but it also favors the humins formation. The HMF degradation is identified as the bottleneck of this approach, requiring working with a minimum O₂ pressure and a high catalytic loading to prevent the humins formation. At 80ºC, a NaOH/HMF ratio of 2:1, and 25 bar oxygen pressure, FDCA selectivity reached 87 % after 8 hours, with minimal humins formation. This result represents an improvement in the sustainability of typical conditions proposed in the literature, mainly because of the minimum NaOH excess used. Additionally, the study explored a one-pot process integrating fructose dehydration and HMF oxidation. While promising, challenges arose in preventing HMF degradation during the process. Nonetheless, these findings highlight viable pathways for sustainable FDCA production, emphasizing the importance of optimizing reaction conditions to balance FDCA yield and humins prevention.