(350d) Synthesis, Charaterization of Bimetallic Ruthenium-Rhenium Catalysts By Strong Electrostatic Adsorption for Hydrogenation of Levulinic Acid to Gamma-Valerolactone
With the worldwide petroleum resources dwindling, it is urgent to look for renewable fuels to replace petroleum. As the one of major products of plant biomass, γ-valerolactone (GVL) is renewable, safe to store and could be used as a liquid fuel, food additive, green solvent and an intermediate in the synthesis of many value added chemicals. The synthesis of γ-valerolactone (GVL) is commonly employed by hydrogenation of levulinic acid (LA) using Ru based catalysts. In this work, we studied the catalytic activity of Ru C and Ru γ-Al2O3 catalysts prepared by strong electrostatic adsorption (SEA), in comparison to catalysts prepared by the conventional catalyst preparation method, dry impregnation (DI) for the LA hydrogenation into GVL. Ru C and Ru γ-Al2O3 catalysts prepared by SEA favored the formation of metallic Ru with the size of 1.3nm and 0.9nm (STEM), respectively. Due to the formation of more well dispersed particles, catalysts prepared by SEA show higher catalytic activities than those prepared at the same weight loading by DI. Furthermore, the presence of K promoter significantly enhanced the catalytic activity for this reaction. Bimetallic RuRe/C and RuRe/ γ-Al2O3 catalysts with different metal composition were also prepared by Co-SEA method those are more active than either K dopant catalyst or the monometallic Ru catalysts we mentioned above. The metal content, particle size, dispersion and reduction characteristics of supported Ru catalysts were characterized by ICP-AES, XRD, STEM, TPR-H2 and XPS. After reaction, all samples were analyzed by XRD, the data indicated the sintering of metal particle occurs for all catalysts prepared by DI, which are not observed for the catalysts prepared by SEA.