Preparation of well-crystallized Pd2oTe7 alloy nanoparticulate catalyst highly active for 1,4-DABE synthesis by butadiene acetoxylation

摘要

The synthesis system of uniform and well-crystallized alloy nanoparticulate catalyst has been studied based on the calculation of pH dependent metal complex concentration in an aqueous solution. Results of both the prediction based on calculation and EXAFS analysis clearly demonstrated that [Pd~(2+)(EDTA)] and Te-citric acid complex species were generated independently in the solution. Since the formation of metal complexes are restricted to [Pd~(2+)(EDTA)] and Te-citric acid complexes in the pH range between 5 and 10, only Pd_(20)Te7 was successfully synthesized when the reducing agent was introduced into [Pd~(2+)(EDTA)] complex/Te-citric acid complex system at room temperature. Moreover, PdTe nanoparticles can be synthesized predominantly in pores of silica-gel, by controlling the temperature of the Pd-EDTA/Te-citric acid/hydrazine mixed solution with a metal loading of 0.5 wt% Pd. Main phase of the well-crystallized alloy nanoparticles formed in the pores was Pd_(20)Te7, leadiug to remarkable stability in catalytic activity, compared with the conventional catalysts.