No abstract

Biomass‐based amines have received a lot of attention due to their sustainability and carbon economy. Herein, the roles of the metal sites (Rh0 or Pd0) and operating conditions on the kinetics and reaction pathways of the heterogeneous catalytic amination of cyclohexanone with aniline have been discussed. Rh/C provides secondary amines with remarkable selectivity toward the hydrogenation product (ΣSi=72 %). The hydrogenation rate over Rh0 is 1.5‐fold higher than that observed over Pd0, while its dehydrogenation capacity diminished (rD_Rh ¡=0.74 h−1 and rD_Pd=1.32 h−1). This difference in the hydrogenation/dehydrogenation performance allows control over the selectivity via disproportionation of an imine intermediate. The kinetic observations can be represented using the Langmuir‐Hinshelwood model, indicating that the formation of the aminal intermediate is the rate‐limiting step. The apparent activation energy for this step on Rh/C (55 kJ/mol) was higher than that previously reported for Pd/C (48 kJ/mol).

We report for the first time Pd nanoparticles (NPs) supported on natural halloysite as catalysts for selective production of p-cymene from waste tire pyrolysis (WTP). The catalysts were prepared by dispersing Pd NPs on either the inner (PdHin, 3.4 nm) or outer surface (PdHout, 1.6 nm) of halloysite nanotubes to produce different acid–base properties. The performance of these catalysts for WTP was studied by micropyrolysis coupled to mass spectrometry (Py-GC/MS) between 400 and 500 °C and for discrete times (2, 12, 20, and 40 s). PdHin exhibited twice the selectivity (42%) of PdHout, which was attributed to its higher acidity (1.74 mequiv g–1) and its bifunctionality established between the support’s acidity and the Pd0 sites. From discrete time-dependent experiments, we estimated activation energies for waste tire conversion (72.8 kJ/mol) and p-cymene production on PdHin (101.0 kJ/mol) under a kinetically controlled regime (Biot ∼3.1, PyI ≫1, and PyII ≫1).

The validation of protocols for carrying out the experimental analysis of amination reactions is of paramount importance to enhance the scientific knowledge and reproducibility of results. Accordingly, in the present paper, a protocol has been proposed for the study of the amination of cyclohexanone-to-secondary amines (Diphenylamine and N-Cyclohexylaniline) over heterogeneous catalysts. The results of activity and selectivity, and the elucidation of a plausible reaction pathway were described in a parent paper. Therefore, the purpose of this document is to inform about the details of the experimental setups, the methods, and the analytical techniques to identify and quantify the reaction products. Finally, some practical and safety considerations are also included. One-pot catalytic amination of cyclohexanone with aniline was performed efficiently in liquid phase on Pd/C. Stirring, He atmosphere and temperature control were critical to achieve reproducible activity results. Ultra-High Performance Liquid Chromatography allows identifying products and reaction intermediates, while nonane performed well as internal standard for GC-FID quantification.