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 (VR ) 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.

Ru single atoms and nanoparticles on carbon nanotubes as multifunctional catalysts.

In the last decade we have witnessed increasing interest in the production of renewable energy and value-added chemicals through sustainable and low-cost technologies where catalysts play a crucial role. Herein, we report the application of a Ru/CNT material containing a mixture of Ru single atoms and Ru nanoparticles as a multifunctional catalyst for both the catalytic reduction of nitroarenes and the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The catalytic activity of the Ru-CNT material was evaluated in the reduction of 4-nitrophenol (4-NP), 4-nitroaniline (4-NA) and 2-nitrophenol (2-NP) in the presence of sodium borohydride as a reducing agent at room temperature, showing high catalytic activity with normalized rate constants (knor) of 19.0 × 103, 57.7 × 103 and 16.6 × 103 min-1 mmol-1 respectively. Furthermore, the catalyst could be reused in at least 10 cycles without catalytic activity loss, confirming the high stability and robustness of the material. The Ru/CNT material also showed good ORR electrocatalytic activity in alkaline medium with Eonset of 0.76 V vs. RHE, a diffusion-limited current density of 3.89 mA cm-2 and ñO2 of 3.3. In addition, Ru/CNT was remarkably insensitive to methanol with a current retention of 93% (51% for Pt/C) and competitive electrochemical stability of 80% after 20 000 s. Moreover, Ru/CNT was active for the OER with jmax = 29.5 mA cm-2 at E = 1.86 V vs. RHE, η10 = 0.50 V and good stability (η10 changed to 0.01 V and jmax only decreased by ≈12% after 500 cycles).