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Catalytic transformation of biomass-derived 5-hydroxymethylfurfural over supported bimetallic iridium-based catalysts

Abstract:

5-Hydroxymethylfurfural (HMF) is a biobased platform chemical that can be valorized into a spectrum of valuable products. In this report, supported Ir, Ir-Co, Ir-Ni, and Ir-Ru catalysts were investigated for this purpose. Only hydrogenation of HMF to 2,5-bis-(hydroxymethyl)furan (BHMF) occurred over all catalysts. The effect of the second metal (Co, Ni, and Ru) on Ir/SiO2was reflected by the kinetic constants being in the order Ir-Ni/SiO2> Ir-Co/SiO2> Ir-Ru/ SiO2. The oxophilic nature of the secondary metal improved the catalytic performance of the bimetallic catalysts compared to the monometallic iridium catalyst (Ir/SiO2). Addition of HCOOH and H2SO4 as cocatalysts is a strategy to reach one-pot conversion of HMF to 2,5-di-methylfuran (DMF). Over-hydrogenolysis products such as 2,5-dimethyltetrahydrofuran were formed when only H2SO4 was added, giving higher activity compared to addition of HCOOH. Simultaneous presence of acids gave the highest HMF conversion, promoting esterification to 5-formyloxymethyl furfural and allowing the one-pot transformation of HMF to DMF. Thermodynamic analysis of HMF transformations revealed that both hydrogenation and dehydration steps are feasible.