Surface Interactions with the Metal Oxide Surface Control Ru Nanoparticle Formation and Catalytic Performance

Here, we report the development of novel Ru-containing catalysts based on porous metal oxide supports such as SnO2, Nb2O5, and Nb2Sn5O15. We assessed structure, porosity, acidity and morphology of both supports and catalysts and established a relationship between surface interactions and catalytic performance in hydrogenation of biomass based levulinic acid (LA) to γ-valerolactone (GVL). All metal oxide supports stabilize small Ru-containing nanoparticles (NPs), whose makeup includes a prevailing fraction of Ru(OH)3. Yet, Nb2O5 stabilizes ∼1 nm Ru-containing NPs which are homogeneously distributed on the metal oxide surface, while for SnO2 and Nb2Sn5O15, sub-nanometer NPs are formed, which are prone to aggregation to minimize surface energy. These differences are assigned to nucleation of NPs on support oxygen vacancies, whose amounts vary and are consistent with NP characteristics. The catalytic testing shows that the 100 % conversion and selectivity as well as high turnover frequency are achieved for Ru/Nb2O5, whose surface morphology includes well-dispersed 1 nm Ru-containing NPs. These and high stability of catalytic performance upon multiple reuse, make Ru/Nb2O5 promising for practical applications. Furthermore, this work validates the usefulness of surface interactions on metal oxides in development of efficient catalytic systems.