Ag nanoparticles on mixed Al2O3–Ga2O3 supports as catalysts for the N-alkylation of amines with alcohols

• Active Ag nanoparticles are developed for alcohol amination reactions.
• Immobilization onto mixed Ga2O3–Al2O3 supports strongly boosts activity and stability.
• The modified Lewis acidity of the support is responsible for this observation.
• The catalysts are heterogeneous and operate under mild reaction conditions (110 °C).

The combination of AgNO3 with NaH results in Ag nanoparticles that can selectively perform alcohol aminations under mild reaction conditions (110 °C). NaH not only serves as a reducing agent for the Ag salt, but also activates the alcohol for dehydrogenation to the corresponding ketone/aldehyde. The stability of the particles can be improved by immobilizing them onto mixed Al2O3–Ga2O3 supports; the combination of Ga and Al provides materials with stronger Lewis acidic sites compared to pure alumina or gallium oxide supports. This leads to catalysts with enhanced activities, without the necessity of adding external Lewis acids. Detailed TEM characterization also reveals a close interaction between the Ag NPs and the gallium oxide phase. The obtained catalysts are recyclable and show activity for the alcohol amination using a variety of aliphatic and aromatic amines under mild conditions.

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