Direct Hydroxymethylation of Furaldehydes with Aqueous Formaldehyde over a Reusable Sulfuric Functionalized Resin Catalyst

Transformation of C5 furaldehydes to the corresponding C6 furaldehydes over a heterogeneous catalyst is a versatile but demanding reaction process. This report describes our discovery that Amberlyst-15, a conventional sulfuric functionalized resin, affords a 43.1% yield for 5-hydroxymethyl-2-furaldehyde (HMF) production with 57.5% selectivity via direct hydroxymethylation of 2-furaldehyde (furfural) with an aqueous formaldehyde reagent. This report is the first to describe an important achievement on the heterogeneous acid catalyst-assisted HMF production from furfural via direct hydroxymethylation in a batch reactor system. The Amberlyst-15 was also reusable and applicable for C5 furaldehyde upgrading of various types: furfuryl alcohol, furfurylamine, and furoic acid toward the corresponding C6 furaldehydes. Results show that a liquid flow system becomes an advanced tool for the continuous production of upgrading furaldehydes through a fixed Amberlyst-15 catalyst bed. Accordingly, the sulfuric functionalized resin-catalyzed direct hydroxymethylation of furaldehydes with aqueous formaldehyde in both batch and flow reactor systems is worthwhile and opens up new avenues for biomass transformations in particles, an important area of inedible biomass utilization.