Sustainable synthesis of amino acids by catalytic fixation of molecular dinitrogen and carbon dioxide

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2018, Vol.2 (3), p.685-693
• Main Authors: Rivas, Manuel, del Valle, Luís J, Turon, Pau, Alemán, Carlos, Puiggalí, Jordi
• Format: Article
• Language: English
• Subjects: Alanine; Amino acids; Aminoàcids; Carbon dioxide; Carbon dioxide emissions; Carbon dioxide removal; Catalysis; Chemical synthesis; Enginyeria química; Environmental impact; Gas mixtures; Glycine; Green chemistry; High temperature; Hydroxyapatite; Impact analysis; Irradiation; Light irradiation; Methane; Nitrogen; Nitrogen fixation; Photosynthesis; Temperature effects; Temperature requirements; Ultraviolet radiation; Àrees temàtiques de la UPC
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c7gc02911j

The industrial process of nitrogen fixation is complex and results in a huge economic and environmental impact. It requires a catalyst and high temperature and pressure to induce the rupture of the strong N-N bond and subsequent hydrogenation. On the other hand, carbon dioxide removal from the atmosphere has become a priority objective due to the high amount of global carbon dioxide emissions ( i.e. 36 200 million tons in 2015). In this work, we fix nitrogen from N 2 and carbon from CO 2 and CH 4 to obtain both glycine and alanine ( d / l racemic mixture), the two simplest amino acids. The synthesis, catalyzed by polarized hydroxyapatite under UV light irradiation and conducted in an inert reaction chamber, starts from a simple gas mixture containing N 2 , CO 2 , CH 4 and H 2 O and uses mild reaction conditions. At atmospheric pressure and 95 °C, the glycine and alanine molar yields with respect to CH 4 or CO 2 are about 1.9% and 1.6%, respectively, but they grow to 3.4% and 2.4%, when the pressure increases to 6 bar and the temperature is maintained at 95 °C. Besides, the minimum temperature required for the successful production of detectable amounts of amino acids is 75 °C. Accordingly, an artificial photosynthetic process has been developed by using an electrophotocatalyst based on hydroxyapatite thermally and electrically stimulated and coated with zirconyl chloride and a phosphonate. The synthesis of amino acids by direct fixation of nitrogen and carbon from gas mixtures opens new avenues regarding the nitrogen fixation for industrial purposes and the recycling of carbon dioxide. The industrial process of nitrogen fixation is complex and results in a huge economic and environmental impact.