Natural attapulgite supported nano-Ni catalysts for the efficient reductive amination of biomass-derived aldehydes and ketones

Abstract

The efficient synthesis of useful primary amines via reductive amination of biomass-based aldehydes and ketones over earth-abundant base metal catalysts is an attractive biomass value-adding technology yet facing lots of challenges. Herein, natural attapulgite (ATP) was applied as support for the fabrication of active Ni catalysts with different Ni loadings (5–30 ​wt%) by the deposition-precipitation method. The Ni/ATP-550 catalyst with 10–15 ​wt% Ni loadings was found to present the highest catalytic performance for the synthesis of valuable 5-amino-1-pentanol (5-AP) via reductive amination of biofurfural-derived 2-hydroxytetrahydropyran among a variety of commonly used oxide supports loaded Ni catalysts, as well as ATP supported nickel catalysts with other loadings, achieving 5-AP yield up to 94%. The intrinsic activity of the Ni/ATP catalysts was found to depend strongly on the Ni0 crystallite size and Ni0 fraction of the catalysts, which generally increased with increasing Ni0 crystallite size and fraction, owing probably to the hydrogenation of imine intermediate is a structure-sensitive reaction. The efficient 10Ni/ATP-550 catalyst also exhibited good activity and stability in the reductive amination of several other biomass-derived aldehydes and ketones to their corresponding primary amines with good to excellent yields (81%–99%). This work provided a clean and efficient natural ATP-supported non-noble metal nickel-based catalytic system for the reductive amination of aldehydes and ketones to synthesize high-value-added primary amines, which could be a promising candidate for the industrial production of amines.