Work

Advancing CO2 utilisation via suspension-based carboxylation of single and mixed biomass-derived phenolics to produce high-value hydroxybenzoic acids

Year: 2025

Type: article

Abstract: Production of organic chemicals from CO 2 and biomass-derived feedstocks can combine the twin advantages of reducing carbon emissions and promote sustainable bioeconomy. This study explores a suspension-based Kolbe–Schmitt reaction for transforming CO 2 into valuable hydroxybenzoic acids (HBAs). Using sodium salts of biomass-derived phenolic compounds (phenol, 2-cresol, guaiacol, syringol, and catechol) four carboxylation scenarios at 225 °C for 2 h under pCO 2 = 30 bar were investigated. The reaction mixture and products were characterised in detail by high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR), revealing previously unreported species, which helped to elucidate the mechanisms of aromatic C-H activation for CO 2 insertion. Mechanistic insights were validated by introducing precursor phenolic compounds, which dramatically enhanced the yields of salicylic acid (97.9 %), 2-cresotic acid (89.2 %), and guaiacol (89.9 %), while enhancing the purity of these main products. Notably, adding precursor phenolic compounds in carboxylation of catechol boosted the yield of 2,3-dihydroxybenzoic acid by up to 96 % and improved selectivity by 52.5 %, in 2 h of reaction. Furthermore, the study demonstrates that phenolic salts can act as carboxylating agents via sodium-proton substitution to facilitate new carboxylation possibilities. For example, reacting a mixture of the five phenolics favoured formation of dicarboxylation products, including industrially relevant 2,3-dihydroxyterephthalic acid and 2-hydroxyisophthalic acid. The results of this work underline the promise of integrating advanced reaction engineering with CO 2 valorisation, as a sustainable circular economy pathway for carbon capture utilisation and storage (CCUS). Efficient production of different HBAs can drive their demand, ensuring rapid process development for enhanced CO 2 utilisation

Source: Chemical Engineering Journal

DOI: 10.1016/j.cej.2025.163498

Authors: Omar Mohammad, Jude A. Onwudili, Qingchun Yuan, Robert Evans

Institution: Aston University

Language: English

Topic: Carbon dioxide utilization in catalysis

Subfield: Process Chemistry and Technology

Field: Chemical Engineering

Domain: Physical Sciences

SDGs: Climate action, Responsible consumption and production, Affordable and clean energy

Open Access status: hybrid

Estimated APC paid: $4,830