The sustainable and catalytic synthesis of N,N-alkylated fatty amines from fatty acids and esters†
Abstract
The reductive amination of fatty acids (FAs) and fatty acid methyl esters (FAMEs) has been identified as a green and effective method to produce N,N-dimethylalkylamines (ADMAs). With current technology, this reaction requires at least two reaction steps. Here, we report a heterogeneous catalytic system for the one-pot synthesis of ADMAs from FA(ME)s, utilizing solely H2 and methylamines (i.e. di- and trimethylamine). The reaction requires two recyclable catalysts: ortho-Nb2O5 for the amidation of FA(ME)s and PtVOx/SiO2 for the hydrogenation of the in situ generated fatty amide to ADMAs. The developed system has a wide range of applicability: it is able to convert all natural FAs to ADMAs (yields up to 90%) and also other tertiary amines were synthesized. Aside from the development of a sustainable and industrially applicable process (e.g. utilizing benign solvents or performing solventless reactions), a kinetic model was developed that describes the reaction rate's relationship with key process parameters such as the H2 pressure and water content. By tuning the reaction conditions, different ratios of primary, secondary and tertiary fatty amines can be obtained.