Key Parameters for the Synthesis of Active and Selective Nanostructured 3d Metal Catalysts Starting from Coordination Compounds – Case Study: Nickel Mediated Reductive Amination

Mara Klarner,Rhett Kempe,Haiko Wittkämper,Niels De Jonge,Christian Papp,Patricia Blach

doi:10.1002/cctc.202100562

Abstract

AbstractThe design of nanostructured catalysts based on earth‐abundant metals that mediate important reactions efficiently, selectively and with a broad scope is highly desirable. Unfortunately, the synthesis of such catalysts is poorly understood. We report here on highly active Ni catalysts for the reductive amination of ketones by ammonia employing hydrogen as a reducing agent. The key functions of the Ni‐salen precursor complex during catalyst synthesis have been identified: (1) Ni‐salen complexes sublime during catalyst synthesis, which allows molecular dispersion of the metal precursor on the support material. (2) The salen ligand forms a nitrogen‐doped carbon shell by decomposition, which embeds and stabilizes the Ni nanoparticles on the γ‐Al2O3 support. (3) Parameters, such as flow rate of the pyrolysis gas, determine the carbon supply for the embedding process of Ni nanoparticles.

Highlights

Reductive amination is a very important reaction because the products, alkyl amines, are used intensively as fine and bulk chemicals, pharmaceuticals, and agrochemicals.[1]
We presented a nanostructured Ni catalyst for the synthesis of primary amines by reductive amination, using ammonia dissolved in water.[5]
Thereby, the key functions of the Ni-salen precursor complex during catalyst synthesis have been identified: (1) The volatility of Ni-salen complexes allows the molecular dispersion of the metal precursor on the support material, which enables an optimal bottom-up approach for the preparation of catalytically active metal sites

Summary

Introduction

Reductive amination is a very important reaction because the products, alkyl amines, are used intensively as fine and bulk chemicals, pharmaceuticals, and agrochemicals.[1]. (2) The salen ligand forms a nitrogendoped carbon shell by decomposition, which embeds and stabilizes the Ni nanoparticles on the γ-Al2O3 support. Thereby, the key functions of the Ni-salen precursor complex during catalyst synthesis have been identified: (1) The volatility of Ni-salen complexes allows the molecular dispersion of the metal precursor on the support material, which enables an optimal bottom-up approach for the preparation of catalytically active metal sites.

Results

Conclusion