Fig. 5: DRIFTS characterization under reaction conditions.
From: Dynamic behavior of molecular Pd-acetate trimers and dimers in heterogeneous vinyl acetate synthesis
a, b Deconvoluted in situ DRIFTS spectra in the 2000 – 1100 cm−1 acetate region of the PdOAc/SiO2 (a) and PdOAc/KOAc/SiO2 (b) catalysts after 180 min time-on-stream. A KOAc-free PdCl2/SiO2 sample was used as background for spectra in (a, b). c, d Normalized integrated DRIFTS intensities of Pd-acetate trimers and dimers for the PdOAc/SiO2 (c) and PdOAc/KOAc/SiO2 (d) catalysts during in situ experiments with exposure to reaction conditions. All intensities in (c, d) are normalized by the integrated DRIFTS intensities of the respective species on the fresh catalysts (values shown in Supplementary Fig. 4). Species present in (a–d) include monomeric AcOH gas (light gray, 1800 and 1770 cm−1), AcOH hydrogen-bound to SiO2 surface hydroxyls (blue, 1745 cm−1), dimeric AcOH gas (dark gray, 1730 cm−1), KH(OAc)2 dimer (light blue, 1715 cm−1), acetate adsorbed on surface Pd in terminal monodentate mode (dark red, 1680 cm−1), KnPd2(OAc)n+2 dimer (orange, 1640 – 1620 cm−1), Pd3(OAc)6 trimer (purple, 1610 cm−1), KOAc (green, 1580 cm−1), Pd2(OAc)4 dimer (pink, 1570 cm−1), and bridged silyl acetate (gold, 1540 cm−1). Analysis conditions for experiments in (a–d): 1 atm; 150 °C; 50 sccm; 15:5:2 vol% C2H4/AcOH/O2 (bal. He).
