A solid iron salt catalyst for selective conversion of biomass-derived C₅ sugars to furfural

Salt is widely applied as catalyst but it is difficult to separate the soluble salt from the reaction medium. To solve this issue, in this study, a solid salt catalyst (FeCl_x-D008) was prepared by using a solid acidic resin (D008) and FeCl₃ via a partial ion exchange method as the demonstration of proof of concept. The introduction of FeCl₃ onto D008 replaced some Brønsted acid sites with newly generated Lewis acid sites. The synergistic effect of the Brønsted and Lewis acidic sites rendered the catalyst with excellent catalytic selectivity for the production of furfural from C₅ sugars (highest yield: 96.3%). The kinetic study showed that the introduction of FeCl_x onto D008 enhanced the activation energy (AE) from xylose to polymer while lowered the AE from xylose to furfural. The FeCl_x species could strongly coordinate with the -SO₃⁻ group in D008 with the high resistivity to leaching. The successful immobilization of FeCl_x species on D008 solved the issue for separation of soluble salts from the reaction medium, which is also an attempt for application of resin-based solid salt as the catalyst in acid-catalyzed reactions.