Thermodynamic approach to foresee experimental CO2 reduction to organic compounds

Abstract

Anaerobic gas fermentation is a promising approach to transform carbon dioxide (CO2) into chemical building blocks. However, the main operational conditions to enhance the process and its selectivity are still unknown. The main objective of this study was to trigger chain elongation from a joint perspective of thermodynamic and experimental assessment. Thermodynamics revealed that acetic acid formation was the most spontaneous reaction, followed by n-caproic and n-butyric acids, while the doorway for alcohols production was bounded by the selected conditions. Best parameters combinations were applied in three 0.12L fermenters. Experimentally, n-caproic acid formation was boosted at pH 7, 37°C, Acetate:Ethanol mass ratio of 1:3 and low H2 partial pressure. Though these conditions did not match with those required to produce their main substrates, the unification of both perspectives yielded the highest n-caproic acid concentration (> 11 g L-1) so far from simple substrates, accounting for 77% of the total products

The authors acknowledge funding from the Agency for Business Competitiveness of the Government of Catalonia (ACCIÓ; COMRDI16-1-0061) and the Spanish Ministry of Science and Innovation (RTI2018-098360-B-100 and PLEC2021-007802). LEQUIA (http://www.lequia.udg.edu/) has been recognized as a consolidated research group by the Catalan Government (2017-SGR-1552). L.R.-A. acknowledge the support by the Catalan Government (2018 FI-B 00347) in the European FSE program (CCI 2014ES05SFOP007). M.R.-C. is grateful for the support of the Spanish Government (FPU20/01362). S.P is a Serra Hunter Fellow (UdG-AG-575) and acknowledges the funding from the ICREA Academia award

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