Reactions of catalytic amination of carbonyl compounds are widely used for the production of amines. In particular, the interaction of benzaldehyde with aliphatic amines in presence of H2 can lead to N-benzyl-N-alkylamines. Such reactions are usually catalyzed by compounds containing platinum group metals (PGM). The search for PGM-free catalysts for such transformations is an important task of modern physical chemistry. This study aimed to check the catalytic activity of the composites containing Co oxides and N-doped carboneous materials in the catalytic reductive amination of benzaldehyde with i-propylamine. Similar systems were researched previously and showed high activity in hydrogenation of heterocyclic compounds and amination of carbonyl compounds. The composites were prepared by pyrolysis Co(II) complexes with imidazole or o-phenylenediamine on aerosil (highly disperse SiO2) and mordenite. It was shown by transmission electronic microscopy that in all cases, the nanocomposites contained Co nanoparticles and carboneous species with the size of ca. 10-50 nm. From the analysis of the Raman spectra, it was concluded that the carboneous component had a graphene-like structure and the particles had more than 8 carbon monolayers. The catalytic activity of the obtained nanocomposites in the reaction of p-methoxybenzaldehyde with di-(i-propyl)amine under H2 pressure (30 atm, 150 °C) was studied. In the case of the composite, prepared by pyrolysis of Co(II) imidazolate on aerosil, the yield of N-(p-methoxybenzyl)-N,N-di-(i-propyl)amine was ca. 80 % when acetonitrile was used as a solvent, while in dioxane the only reduction of p-methoxybenzaldehyde to corresponding benzylic alcohol took place. The composite prepared by decomposition of Co(II) complex with o-phenylenediamine on aerosol and mordenite was not active in reductive amination. As a result, the perspective of using Co-based nanocomposites for the reductive amination of carbonyl compounds was shown and the high impact of such catalytic systems was demonstrated.

Catalytic activity of co-based composites in the reductive amination

ACS Fall 2021

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