Development of metal nanoparticles supported materials as efficient catalysts for reductive amination reactions using high-throughput experimentation

Substituted amines and N-heterocycles, useful intermediates in industry, can be synthesized by reductive amination of ketones with amines in the presence of metal supported catalysts. In this work, multi-functional catalysts based on Pt, Pd, and Au nanoparticles supported on different metal oxides capable to efficiently catalyze the liquid phase selective reductive amination of ketones have been developed. Catalytic screening performed by HT experimentation showed that Pt-catalysts are more active than the corresponding Pd counterparts, while Au-based materials present very low activities. Excellent results were obtained with Pt/TiO2 (52% of amine conversion with selectivity >95%, TON = 2033) followed by Pt/MgO, Pt/CaO, and also Pt/Al2O3. Increase in the reduction temperature pre-treatment of Pt-catalysts improved the catalytic activities (≈65% of amine conversion with selectivity >95%, TON = 2541 for Pt/TiO2), these values being quite superior to those observed with Pt/C and Pt/Al2O3 commercial catalysts. With the appropriate treatment of support prior to metal impregnation efficient Pt/Al2O3 materials can also be obtained (TON = 1685). The results suggest that Pt and Pd catalysts activities can be enhanced by appropriate tailoring the physical and chemical properties of oxide supports depending on the type of metal, this favouring a strong metal-support interaction (SMSI) on solids.