Starbon/High-Amylose Corn Starch-Supported N-Heterocyclic Carbene-Iron(III) Catalyst for Conversion of Fructose into 5-Hydroxymethylfurfural

Iron-N-heterocyclic carbene complexes (Fe-NHCs) have come to prominence because of their applicability in diverse catalytic reactions, ranging from C-C cross-coupling and C-X bond formation to substitution, reduction, polymerization, and dehydration reactions. The detailed synthesis, characterization, and application of novel heterogeneous Fe-NHC catalysts immobilized on mesoporous expanded high-amylose corn starch (HACS) and Starbon 350 (S350) for facile fructose conversion into 5-hydroxymethylfurfural (HMF) is reported. Both catalyst types showed good performance for the dehydration of fructose to HMF when the reaction was tested at 100 degrees C with varying time (10 min, 20 min, 0.5 h, 1 h, 3 h and 6 h). For Fe-NHC/S350, the highest HMF yield was 81.7% (t = 0.5h), with a TOF of 169 h(-1), fructose conversion of 95%, and HMF selectivity of 85.7%, whereas for Fe-NHC/expanded HACS, the highest yield was 86% (t = 0.5h), with a TOF of 206 h(-1), fructose conversion of 87%, and HMF selectivity of 99%. Iron loadings of 0.26 and 0.30 mmolg(-1) were achieved for Fe-NHC/expanded starch and Fe-NHC/S350, respectively.