Selective hydrodeoxygenation of biomass derived 5-hydroxymethylfurfural over silica supported iridium catalysts

Catalytic performance of iridium supported on SiO2 was investigated for 5-hydroxymethylfurfural (HMF) transformation. Ir/SiO2 catalysts exhibiting different metal loading (1, 3, and 5 wt.%) were tested in the preliminary experiments in the hydrogenation of two probe molecules, e.g. ethyl pyruvate (EP) and ketopantolactone (KP) to evaluate the Ir dispersion on the catalyst activity in CO hydrogenation. In the transformation of HMF the influence of metal dispersion, iridium precursor and addition of H2SO4 were studied revealing that 2,5-bis-(hydroxymethyl)furan (BHMF) was the main product with 83% selectivity at 70% conversion of HMF over chlorine free Ir/SiO2 together with H2SO4 at 333 K in THF under 10 bar H2 pressure. On the other hand, one-pot synthesis of HMF to 2,5-dimethylfuran (DMF) was promoted in the presence of chlorine containing 1%Ir/SiO2(Cl) and H2SO4. Both of these products are considered high value-added chemicals from biomass-derived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF.