RESUMO
We report a novel method for development of magnetically recoverable catalysts prepared by thermal decomposition of palladium acetylacetonate in the presence of iron oxide nanoparticles (NPs). Depending on conditions, the reaction results either in a dispersed mixture of Pd and iron oxide NPs or in their aggregates. It was demonstrated that the Pd loading, reaction temperature, solvent, and iron oxide NP size and composition are crucial to control the reaction product including the degree of aggregation of Pd and iron oxide NPs, and the catalyst properties. The aggregation controlled by polarization and magnetic forces allows faster magnetic separation, yet the aggregate sizes do not exceed a few hundred nanometers, making them suitable for various catalytic applications. These NP mixtures were studied in a selective hydrogenation of 2-methyl-3-butyn-2-ol to 2-methyl-3-buten-2-ol, demonstrating clear differences in catalytic behavior depending on the catalyst structure. In addition, one of the catalysts was also tested in hydrogenation of 3-methyl-1-pentyn-3-ol and 3-methyl-1-nonyn-3-ol, indicating some specificity of the catalyst toward different alkyne alcohols.
RESUMO
We report a novel method for synthesis of alloy PtFe nanoparticles (NPs) of different compositions using γ-Fe2O3 NPs as an iron source. We show here other growth mechanisms than conventional nucleation on a NP surface leading to core-shell NP or seeded NP growth. Depending on reaction conditions, different compositions of PtFe NPs can be obtained. PtFe NPs may coexist with γ-Fe2O3 NPs in the reaction product. This mixture obtained in situ allows much higher catalytic activity in hydrogenation of methyl-3-buten-2-ol than that of only PtFe nanoparticles or merely mixed PtFe and γ-Fe2O3 NPs. The presence of both PtFe and γ-Fe2O3 NPs allows formation of dense and stable NP arrays which hold promise for catalytic applications in microreactors or other reactor designs where a catalytic film is favoured.
