The double complex salt [Pd(NH3)4](ReO4)2 was employed as a precursor of supported bimetallic catalysts for selective hydrogenation of furfural. Direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 in flowing H2 at 400°C yields bimetallic nanoparticles 2-3 nm in size that exhibit significant interaction between the metals, as evidenced by temperature-programmed reduction (TPR), temperature-programmed hydride decomposition (complete suppression of β-PdHx formation), extended x-ray absorption fine structure (EXAFS) spectroscopy at the Pd K and Re LIII edges (Figure 1, Pd-Re distance = 2.72 Å), and scanning transmission electron microscopy (STEM) with energy dispersive x-ray (EDX) analysis. In contrast, calcination of [Pd(NH3)4](ReO4)2 on γ-Al2O3 at 350°C in O2 and subsequent reduction in H2 at 400°C results in metal segregation and formation of large (&gt;30 nm) supported Pd particles; Re covers the Pd particles and the γ-Al2O3 support non-selectively. A 1:2 PdRe catalyst prepared by sequential impregnation and calcination using HReO4 and [Pd(NH3)4](NO3)2 precursors exhibits a similar morphology. The catalyst derived via direct reduction of supported [Pd(NH3)4](ReO4)2 exhibits remarkably high activity for selective hydrogenation of furfural to FAL at 150°C and 1 atm. Suppression of H2 chemisorption and a high linear-to-bridging ratio in CO diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) correlate with high FAL selectivity.

Catalysts for selective hydrogenation of furfural derived from [Pd(NH3)4](ReO4)2 on γ-Al2O3: Advanced characterization by EXAFS, STEM-EDX, and complementary techniques

253rd National Meeting (2017)

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