Variation in the Structure and Activity of Commercial Palladium on Carbon Catalysts

Abstract

<p>Palladium catalysed hydrogenolysis is often the final step in challenging natural product total synthesis and a key step in industrial processes towards fine chemicals. Here we demonstrate that there is wide variability in quality of commercial sources of palladium on carbon (Pd/C), which results in differences in selectivity, reaction times, and yields. This is established through a combination of XRD, XPS, BET and TEM analysis, this will serve as a template for others to quickly identify a high-quality source of Pd/C catalyst — meaning less time spent on time consuming reaction optimisation studies. Key indicators of a high-quality catalyst include: small particle sizes, large surface area, and the presence of both Pd<sup>0</sup> and Pd<sup>2+ </sup>active species (not present in all commercial sources). Further this work will enable the design and synthesis of new high-quality Pd/C catalysts.</p>

Screening of Palladium/Charcoal Catalysts for Hydrogenation of Diene Carboxylates with Isolated-Rings (Hetero)aliphatic Scaffold

“…Furthermore, deposition of hydrated PdO followed by in situ reductions with H 2 (changes of Pd(OH) 2 system caused by hydrogenation were shown by TEM, Figures S2 and S3 in Supplementary Materials ) provided the most efficient composites, whereas deposition of hydrated PdO followed by reduction with formaldehyde led to the formation of the least active systems. Though the majority of Pd/Support composites contain Pd in the oxidation states 0 and +2 simultaneously [ 44 , 45 , 46 , 47 , 48 ], the action of hydrogen at the beginning of the hydrogenation process results in a reduction of Pd 2+ [ 44 , 49 ] (similar reduction of Pd 2+ to Pd 0 was observed under the action of CO [ 50 ]). Thus, different activity of the composites can be explained by in situ formation of the NPs, which have a different shape (different crystallographic planes exposed to the surface) or content of defects.…”