Unraveling theEvolutionary Pathways of Major Productsfrom the Thermal Conversion of 5-Hydroxymethylfurfural

Abstract

Abstract Thermosensitive 5-hydroxymethylfurfural (HMF) serves as a bridge between biochemical and petrochemical industries, and research into its thermal conversion inherent characteristics is crucial for the preparation of HMF and its derivatives. This study systematically analyzes the structures of the major products of HMF thermal conversion at 150 °C and proposes their major product evolutionary pathways. The results indicate that there are five major products of thermal conversion, with the HMF furan ring skeleton remaining stable and its hydroxymethyl and aldehyde groups serving as the primary active sites. Among these, 5,5′-(oxybis(methylene))-bis(furan-2-carbaldehyde) (OBMF), formed by the etherification of the hydroxymethyl group, is the main product, accounting for an average of 65.96 ± 7.78 wt % of the total HMF conversion products. The water generated during etherification leads to the hydrolysis of HMF into levulinic acid and formic acid, which in turn triggers subsequent reactions such as esterification, etherification, and aldehyde–aldehyde condensation reactions, resulting in the formation of dimers, trimers, and tetramers. Ultimately, the tetramer undergoes a Knoevenagel reaction with levulinic acid and an esterification reaction with formic acid to form a hexamer.