Multifunctional Catalytic Properties of Pd/CNT Catalysts for 4‐Nitrophenol Reduction

Hydrogenation Reactions with Synergistic Catalysis of Pd single atoms and nanoparticles under Near-Ambient Conditions

Due to the limited resources and high cost of noble metals, boosting their catalytic activities is highly desired in the current catalysis industry. Here, we report a synergetic catalyst, combining Pd²⁺ and Pd⁰ species in a nitrogen-doped porous carbons (NPC), which shows boosted catalytic activities in hydrogenation reactions of organic nitro compounds (nitrobenzene, 4-nitrophenol, 1-nitronaphthalene and 1-nitropropane) under near ambient conditions. This synergetic catalyst NPC-[Pd] was synthesized by partial reduction of a palladium-loaded NPC. The catalytic activities and selectivity of NPC-[Pd] for hydrogenation were enhanced significantly compared with those of NPC-Pd²⁺ or NPC-Pd⁰ nanoparticles. Theoretical calculations show that H₂ preferentially dissociates on Pd nanoparticles, and then organic molecules (nitrobenzene) can be captured and react with the dissociated H atom on Pd²⁺ sites. Similar reaction procedure also occur on Pt or Rh. Hydrogenation of different aromatic compounds with different functional groups (naphthalene, 4-nitrochlorobenzene, benzaldehyde and acetophenone) confirmed the broad excellent catalytic activity of this synergistic catalyst.

Solvent-Free Hydrogenation of Squalene Using Parts per Million Levels of Palladium Supported on Carbon Nanotubes: Shift from Batch Reactor to Continuous-Flow System

The transition from batch catalytic processes to continuous flow processes requires highly active and stable catalysts that still need to be developed. The preparation and characterization of catalysts where palladium single atoms and nanoparticles are simultaneously present on carbon nanotubes were recently reported by us. These catalysts are considerably more active than commercial or previously described catalysts for the liquid phase hydrogenation of terpenes. Herein is shown that under solvent-free conditions, squalene (SQE) could be converted into squalane (SQA,>98 %) using only 300 ppm of Pd in less than 1.4 h at 20 bar H₂ and 120 °C. Catalyst stability was assessed in a lab-scale flow reactor, and long-term experiments led to turnover number (TON) higher than 300000 without any detectable loss in the activity. Then, the implementation of this catalyst in a commercial intensified continuous-flow milli-reactor pilot was achieved. High purity SQA (>98 %) could be obtained by continuous hydrogenation of solvent-free SQE at 180 °C and 30 bar H₂ with a contact time below 15 min. A production capacity of 3.6 kg per day of SQA could be obtained with an effective reactor volume (V_R ) of 43.2 mL for this complex 3 phase reaction. Large-scale production can now be foreseen thanks to seamless scale-up provided by the continuous flow pilot supplier.