Matching Relationship Between Carbon Material and Pd Precursor

Stable and Versatile Pd Precursors for the Preparation of Robust Pd Catalysts Under Continuous-Flow

To achieve global sustainability, the chemical and engineering communities require the development of versatile precursors that can be used to synthesize robust catalysts. To meet this demand, we developed a new Pd precursor for highly efficiently incorporating fine Pd-metal into supports. An atmospherically stable Pd precursor (Pd-80) was prepared by thermally promoting the aerobic oxidation of tetrakis(triphenylphosphine)palladium. The physical properties of Pd-80 were investigated by NMR spectroscopy, SEM, XPS, solvent-relaxation NMR spectroscopy, and dynamic light scattering (DLS) experiments. We also prepared a cordierite-supported Pd catalyst (Pd/cordierite) by stirring Pd-80 and cordierite powder in chloroform at room temperature. Pd/cordierite selectively catalyzed the hydrogenation of various reducible functional groups, including alkynes, azides, nitro groups, olefins, CO2Bn, N-Cbz, O-Bn, aromatic ketones, and styrene oxide, in continuous-flow hydrogenation reactions. The Pd/cordierite-catalyzed continuous-flow hydrogenation of nitrobenzene derivatives afforded the corresponding anilines, with catalytic activities maintained for over 250 h of continuous operation with a turnover number (TON) of 61,090.

Hydrogen production from the catalytic dehydrogenation of dodecahydro-N-ethylcarbazole: effect of Pd precursor on the catalytic performance of Pd/C catalysts

In this paper, Pd/C catalysts are synthesized via Ar glow-discharge plasma reduction using activated carbon as the support and Pd(acac)₂, Pd(NO₃)₂, K₂PdCl₄, and H₂PdCl₄ as the Pd precursors, and their catalytic performances are investigated by hydrogen production from dodecahydro-N-ethylcarbazole (H12-NEC). Pd/C-A, prepared from Pd(acac)₂, which has the smallest palladium nanoparticles (1.7 nm), the highest dispersion (34%) and no residue of inorganic ions, exhibits the best catalytic activity with a hydrogen release of 5.28 wt.%, which is 2.2 times that of Pd/C-H. The order of the apparent activation energies of the prepared Pd/C catalysts, according to the kinetics of the H12-NEC dehydrogenation reaction, is as follows: Pd/C-A ≈ Pd/C-N < Pd/C-K < Pd/C-H. When Pd(acac)₂ with a large ligand acts as a cation Pd precursor, the effect of coulombic attraction to Pd²⁺ during the plasma reduction process makes it difficult for Pd nanoparticles (NPs) to migrate, which leads to the formation of ultrafine Pd NPs.