Pt and Pd nanoparticles supported on structured materials as catalysts for the selective reductive amination of carbonyl compounds

Abstract

Metal catalysts based on Pt and Pd nano-particles supported on structured microporous Beta zeolites and mesoporous MCM-41 materials, as well as specially designed γ-Al2O3 samples, were synthesized following a simple and economic procedure. Physico-chemical characterization of metal-composites (by XRD, IR spectroscopy, TEM, N2 adsorption, ICP, among others) indicated that both Pt and Pd nano-particles were adequately supported and homogeneously dispersed on supports. These metal/solid acid composites were applied as efficient catalysts under mild reaction conditions in the selective reductive amination of ketones, a useful industrial reaction for the synthesis of substituted amines and N-heterocycles. Results obtained showed that Pt/Al-Beta catalyst possesses the best catalytic activity (TON=1610, with amine selectivities >95%) superior to that observed with commercial Pt/C and Pt/Al2O3 (TON≈1000). Enhancements in Pt/Al-Beta samples were achieved by optimizing the Pt loading, and mainly the Si/Al molar ratio in solids. On the contrary, inferior catalytic activities were encountered with the Pt/Si-MCM-41 and Pt/Al-MCM-41 materials. The Pd incorporation on MCM-41 materials produced more active catalysts than the commercial Pd/C and Pd/Al2O3 samples. Finally, the study of Pt/ and Pd/γ-Al2O3 materials demonstrated that the treatments of support prior to the metal impregnation and the posterior calcinations processes were essentials to obtain efficient catalysts.