Investigation into Lewis and Brønsted acid interactions between metal chloride and aqueous choline chloride-oxalic acid for enhanced furfural production from lignocellulosic biomass

• Published in: The Science of the total environment 2022-06, Vol.827, p.154049-154049, Article 154049
• Main Authors: Lee, Cornelius Basil Tien Loong, Wu, Ta Yeong, Yong, Khai Jie, Cheng, Chin Kui, Siow, Lee Fong, Jahim, Jamaliah Md
• Format: Article
• Language: English
• Subjects: Biomass valorization; Biorefinery; Metal chloride; Oil palm fronds; Wood technology
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.154049

Furfural has been identified as a valuable biobased platform chemical that can be further converted into bioenergy and biochemicals. Furfural is derived from lignocellulosic biomass and can also be regarded as a sustainable alternative to petrochemical products. Herein, the performance of trivalent metal chlorides (FeCl3, AlCl3) and tetravalent metal chlorides (SnCl4, TeCl4) as Lewis acidic cocatalysts was investigated in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent (DES) system for producing furfural from oil palm fronds (OPFs). The metal chlorides with greater electrical field gradients were stronger Lewis acids that enhanced both furfural production and degradation reactions. The main degradation product in this reaction system was humin, and this result was confirmed by FTIR analysis. By subjecting OPFs to an aqueous DES reaction (120 °C, 45 min) with SnCl4 (2.50 wt%), a furfural yield of 59.4% was obtained; without incorporated metal chlorides, the furfural yield was 46.1%. Characterization studies showed synergistic Lewis and Brønsted acid interactions between metal chlorides and DES components. Overall, the residual OPFs showed high glucan content, which led to the production of glucose (71.4%) as a byproduct via enzymatic hydrolysis. Additionally, the aqueous DES system was recycled and reused for several additional runs. The proposed aqueous DES system presents a promising biorefinery approach for the conversion of OPFs to biochemicals. [Display omitted] •Lewis and Brønsted acid interaction in ChCl-oxalic acid enhanced furfural yield.•Metal chlorides .with greater χ/r2 values were stronger Lewis acidic co-catalysts•Furfural yield reached 59.4% with SnCl4 (2.50 wt%) at 120 °C for 45 min.•The reacted biomass was used to produce glucose (71.4%) as a by-product.•The deep eutectic solvent system showed appreciable yields for 3 recycle runs.