Tomography Analysis of Ru Supported on Micro and Mesoporous Carbon: A Correlation Between Morphology and Catalytic Activity

Ruthenium (Ru) based catalysts effectively hydrogenate aromatic compounds, olefins, aldehydes, ketones and other carbonyl compounds. Ru/C reached conversion and selectivity over 90 % for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). However, solvents and supports greatly affect activity and selectivity. Ru/graphite, Ru/zeolite, or a mixture of Ru/graphite and zeolite showed very different GVL yields. Depositing Ru on four graphitized carbon materials differing in their surface area, different Ru dispersion has been produced which lead to different catalytic activities in CO methanation, as reported by Truszkiewicz et al. However, even if the control of selectivity has been roughly achieved, the stability of Ru-based catalysts is still insufficient. Villa et al. studied the hydrogenation of levulinic acid at 70°C by Ru supported on functionalized mesoporous carbons, showing a good stability. On the contrary the same catalysts showed a decreased activity after three consecutive cycles when the reaction was performed at higher temperature (200°C). Deactivation mainly has been addressed to Ru leaching, Ru particle aggregation or carbon deposition on them. Therefore, characterization analyses of the support morphology and surface, as well as of the metal particle size, shape and dispersion, are critical to understand how certain factors can modulate the catalytic properties. Here, we synthesized Ru nanoparticles supported on two different types of carbon, i.e. ordered mesoporous carbon (OMC) and activated carbon (AC). STEM tomography analyzed Ru particles size and distribution, showing different NPs confinement inside the pores. HAADF STEM electron tomography sets the material 3D structure and improved the identification of the preferential NPs allocation which strongly affects catalytic activity.