Upcycling used cooking oil into bio-based amines: Precursors for sustainable polymer materials

The increasing demand for sustainable polymer materials has driven research toward renewable and waste-derived feedstocks capable of replacing fossil-based chemicals. Used cooking oil (UCO) is an abundant waste resource with significant potential as a bio-based precursor for functional intermediates in polymer synthesis. UCO is investigated as a feedstock for the preparation of multifunctional bio-based amines. Despite extensive research on the functionalization of vegetable oils, the synthesis and detailed structural characterization of UCO-derived amidoamines remain insufficiently explored. Here, we present a synthesis route for the preparation of bio-based amines under solvent-free conditions using commonly employed zinc(II) perchlorate hexahydrate as a Lewis acid catalyst. UCO was first epoxidized using the Prilezhaev reaction and afterwards reacted with aliphatic and aromatic amines, including 1,6-hexanediamine (HDMA), m-xylylenediamine (m-XDA), and tris(3-aminoethyl)amine (TREN) to ensure oxirane ring-opening and aminolysis of ester bonds. The synthesized HMDA/EUCO, m-XDA/EUCO and TREN/EUCO bio-based amines had total amine values ranging from 280 mg KOH/g to 468 mg KOH/g and viscosities ranging from 12,000 mPa·s to 90,000 mPa·s. The chemical structures of the obtained products were investigated using nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy, confirming the formation of β-amino alcohol structures resulting from oxirane ring opening, along with aminolysis of ester bonds yielding amide derivatives. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was applied to provide detailed insight into the molecular species present in these systems, revealing that the products are mixtures of monomeric, dimeric, and trimeric species. The combined analytical results establish the chemical structure and molecular composition of the obtained UCO-derived bio-based amines, confirming the formation of multifunctional products containing amide, β-amino alcohol, and amine functionalities. The work demonstrates a viable route for the valorization of waste cooking oil into multifunctional bio-based amines and contributes to the development of sustainable polymer precursors within a circular bioeconomy.