Palladium N-doped carbon as catalyst for green process

Abstract

This thesis work involved the development of metal-based heterogeneous catalysts for the formation of new C-C bonds, including Heck and Suzuki-Miyaura cross-coupling reactions. In this regard, a new class of nitrogen-doped carbon-based materials were synthesized starting from chitin as both carbon and nitrogen precursors. More in detail, the synthesis of N-doped carbons-supported Pd nanoparticles was performed through two different approaches, i.e. impregnation and solution method. For each method three catalysts were formed with different amount of Pd (1%, 2.5%, 5%). The resulting catalytic materials were characterized for their structural and morphological properties with different techniques, including XPS, XRD, SEM, TEM, ICP-MS and N2-physisorption. Catalytic tests for the above-mentioned cross-coupling reactions were performed both under batch conditions and in pressurized reactors (autoclaves). In both reactions were tested all catalysts and the best one was used to optimize experimental conditions, including temperature, base quantity, reaction time and catalyst amount. Different substrates were then tested, and a catalyst recycling study was carried out at the end. The reaction outcome, in terms of conversion and selectivity, was checked by 1H NMR and GC-FID in order to verify reproducibility. On the other hand, GC-MS and NMR spectroscopy (1H NMR, 13C NMR and bi-dimensional NMR) were employed for the products identification. In the final stage of this Thesis work, the synthesis and the applications of the aforementioned catalytic materials was accomplished also through a mechanochemical approach, by using an extruder available in GOST laboratory. Even more important, with this technique both the synthesis of the catalytic materials and their application were performed under solvent free and continuous conditions, improving not only the sustainability of the whole process but also the reaction productivity.