Lanthanum-modified Hydroxyapatite-Supported Cobalt for Highly Selective Synthesis of Primary Amines via Ethylene Glycol Amination

Abstract

Alcohol amination, which produces water as the sole by-product and utilizes biomass-derived feedstocks, represents an environmentally benign alternative for amines synthesis. However, achieving efficient alcohol activation under mild conditions while suppressing over-alkylation (e.g., secondary or cyclic amines) remains challenging. Although cobalt (Co) -based catalysts are widely used in alcohol amination, controlling primary amine selectivity persists as a key research challenge. This study employs structurally tunable hydroxyapatite (HAP) as a catalyst support and enhances catalytic performance via a metal-ion pre-modification strategy. The experimental results show that lanthanum (La) -modified Co/La-HAP exhibits superior primary amine selectivity in ethylene glycol (EG) amination, affording an EG conversion of 28.7% and a primary amine selectivity of 65.5%. In comparison with unmodified Co/HAP, the primary amine yield increased from 10.5% to 21.2%. Systematic characterization reveals that La modification not only enhances the acid-base synergy of HAP but also weakens the strong Co-HAP interaction, thereby suppressing the formation of difficult-to-reduce Co species. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) further confirms that Co/La-HAP promotes EG dehydrogenation more effectively and stabilizes the key glycolaldehyde (GA) intermediate.