Thermocatalytic depolymerization of Kraft lignin to guaiacols using HZSM-5 in alkaline water-THF co-solvent: A realistic approach

Raikwar, Deepak and Majumdar, Saptarshi and Shee, Debaprasad (2019) Thermocatalytic depolymerization of Kraft lignin to guaiacols using HZSM-5 in alkaline water-THF co-solvent: A realistic approach. Green Chemistry. ISSN 1463-9262

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Abstract

Lignin is recognized as a renewable and rich source of aromatics, which could be an alternative to the fossil fuel-based petrochemicals. However, the development of an efficient catalyst and industrially scalable process for lignin depolymerization remains a challenge. Present work is therefore dedicated towards a one-pot approach for depolymerization of commercial Kraft lignin in a batch reactor with higher loading using the water-THF solvent mixture over HZSM-5 and NaOH catalytic system. Process parameters such as time, temperature, lignin-to-solvent (w/v), water-to-THF (v/v), NaOH-to-lignin (w/w), catalyst-to-lignin (w/w), and Si/Al mole ratio of HZSM5 was chosen carefully and optimized using statistical analysis- response surface methodology (RSM). A significant yield of 61% for a particular single ring aromatic compound (i.e. guaiacols) was obtained under the optimized reaction conditions: Reaction Time=2h, Temperature=533 K, Lignin-to-solvent ratio=0.060 (1:16.6), Water-to-THF ratio=0.86:1, Catalyst-to-lignin ratio=1:6 (0.16), NaOH-to-lignin ratio=0.1 and Si/Al ratio=280. Around 77% of lignin was selectivity converted to guaiacols (79%) with minimal char formation (7.7%). The Hansen solubility parameter and RSM studies indicate that the obtained results were significantly related with the solubility of lignin and guaiacol at different water-THF ratio. FT-IR and 1H-NMR studies were also performed to correlate process outcome with the presence of functional groups in identified EtOAc soluble products. A plausible mechanism for catalytic depolymerization of lignin has been proposed considering the product distribution obtained under varying process parameters.

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IITH Creators:
IITH CreatorsORCiD
Majumdar, SaptarshiUNSPECIFIED
Shee, DebaprasadUNSPECIFIED
Item Type: Article
Subjects: Chemical Engineering
Divisions: Department of Chemical Engineering
Depositing User: Team Library
Date Deposited: 19 Jun 2019 04:29
Last Modified: 19 Jun 2019 04:29
URI: http://raiith.iith.ac.in/id/eprint/5504
Publisher URL: http://doi.org/10.1039/C9GC00593E
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