Selective hydrodeoxygenation of phenolic compounds by oxide-supported iridium nanoparticles

Abstract

As more focus is placed on renewable energy to combat climate change and to meet the increasing energy demand, research into new energy sources has become more relevant than ever. A promising source of renewable energy as well as valuable platform-chemicals is lignin, which comprises around 40% of the energy stored in tree-derived biomass. To utilize lignin in energy production, lignin is first depolymerized into a bio-oil. As the lignin-derived bio-oil has a high oxygen content, which can lead to polymerization and cause poor fuel combustion, removal of oxygen-groups via catalytic hydrodeoxygenation (HDO) is necessary. For this purpose, supported metal catalysts have been developed to selectively yield aromatic products. A largely underexplored metal for HDO is iridium, which is a novel candidate for new catalysts. In this thesis optimization was performed for finding the combination of iridium and oxide-support that is most active and selective towards HDO. The hydrodeoxygenation of an alkylated phenol, catalyzed by iridium nanoparticles, was investigated on different supports (Nb2O5, TiO2, ZrO2, Al2O3, MgAl2O4, and SiO2-Al2O3) under mild conditions (200 – 275˚C, 2.5 bar). The surface chemistry, nanoparticle-size and -dispersion of the catalysts was characterized. The Ir/Al2O3-catalyst was tested in a recycling experiment to observe the HDO-activity over multiple catalytic runs.