Microwave-assisted extraction of lignin from coconut coir using deep eutectic solvents and its valorization to aromatics

• Published in: Bioresource technology 2022-02, Vol.345, p.126528-126528, Article 126528
• Main Authors: Mankar, Akshay R., Pandey, Ashish, Pant, K.K.
• Format: Article
• Language: English
• Subjects: Biomass; Catalytic transfer hydrogenation; Cocos; Deep Eutectic Solvents; Lignin; Lignin - analogs & derivatives; Microwave; Microwaves; Pretreatment; Solvents
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2021.126528

[Display omitted] •Effective delignification of coconut coir using deep eutectic solvent was achieved.•ChCl: LA (1:4) gave the highest lignin yield of 82% with >95% purity.•Extraction ability of DES was correlated with Kamlet Taft parameters and pKa values.•H factor for process was 55.5 due to efficient microwave heating at 150 °C, 20 min.•CTH of extracted lignin gave bio-oil yield of 38.8% using Ru/C and isopropanol. Lignin is a rich renewable source of aromatics present in lignocellulosic biomass (LCB). The extraction of lignin from the intricate LCB network is a challenging task for successful commercialization of sustainable biorefineries. In the present study, a series of choline chloride (ChCl)-carboxylic acid based deep eutectic solvents (DESs) were used for the extraction of lignin from coconut coir under microwave irradiation. Among the synthesized DESs, ChCl: lactic acid (LA) (1:4) gave the highest lignin yield of 82% with >95% purity. Interestingly, the severity factor (H factor) for the pretreatment process was found to be a significantly lower (55.5) as compared to reported studies due to efficient microwave heating. Moreover, the DES showed good recyclability for four recycle runs thus making it a promising candidate for the delignification of LCB. Finally, the extracted lignin was converted to aromatics via catalytic transfer hydrogenation (CTH) using Ru/C and isopropanol as in-situ hydrogen donor.