Catalytic performance of iridium supported on SiO2 was investigated for 5hydroxymethylfurfural (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 C=O 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 hydrogen. On the other hand, one-pot synthesis of HMF to 2,5dimethylfuran (DMF) was promoted in the presence of chlorine containing Ir/SiO2(Cl) and H2SO4. Both of these products are considered high value-added chemicals from biomassderived 5-hydroxymethylfurfural. The exposed iridium atoms together with the total acid sites are an important catalytic descriptor for hydrogenation of HMF to BHMF.

Direct amination of 1-dodecanol with NH3 and H2 over Rh, Pt, Ir, Ru, Ni, Cu, and Co catalysts on SiO2 has been studied. Catalyst synthesis was performed to allow high metal dispersion. The catalysts were characterized by TPO/TPR-MS, N2 physisorption at 77 K, transmission electron microscopy, ICP analysis, and XPS. Through this characterization it was possible to relate the physical properties of the catalysts with activity and selectivity in 1-dodecanol amination. Iridium and ruthenium catalysts showed the highest conversion, about 77% after 24 h, and the selectivity of 78% and 81%, respectively, toward the desired product 1-dodecylamine. The Ru catalyst exhibited the highest yield of the desired product. In the conditions studied, the conversion increased in the order Cu < Ni < Rh < Pt < Co < Ir < Ru, and the selectivity was the highest for Ni and Co after 24 h. Both activity and selectivity of an oxidized Ir/SiO2 catalyst increased considerably as the reaction progressed showing clearly that in situ catalyst reduction occurs being beneficial for dodecanol amination. High activity of Ir was also related to high metal dispersion.

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/SiO2 was 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.