Catalytic depolymerization of organosolv lignin to phenolic monomers and low molecular weight oligomers

The lignin-first strategy provides significant potential for producing value-added phenolics and high-quality biofuels. In this contribution, stepwise extraction and depolymerization of lignin in corncob residue towards the production of phenolic monomers, lignin-derived dimers and trimers was inves...

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Bibliographic Details
Published in:Fuel (Guildford) 2019-05, Vol.244, p.247-257
Main Authors: Liu, Xudong, Jiang, Zhicheng, Feng, Shanshan, Zhang, Hui, Li, Jianmei, Hu, Changwei
Format: Article
Language:English
Subjects:
Alcohol
Alcohols
Biofuels
Butanol
Calorific value
Catalysis
Catalysts
Catalytic depolymerization
Cellulose
Cellulose pulp
Cleavage
Degradation
Depolymerization
Dimers
Guaiacol
Intermediates
Lignin
Low molecular weights
Molecular weight
Monomers
Oligomers
Phenolic compounds
Phenolic monomers
Phenols
Pulp
Selectivity
Solvolytic fractionation
Trimers
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Summary:The lignin-first strategy provides significant potential for producing value-added phenolics and high-quality biofuels. In this contribution, stepwise extraction and depolymerization of lignin in corncob residue towards the production of phenolic monomers, lignin-derived dimers and trimers was investigated. H2O/n-butanol (4:6, v/v) co-solvent could extract 87.1% of lignin in corncob residue, retaining a high-purity (86.0%) cellulose pulp. Ni/HZSM-5 catalysts with different Ni loadings were prepared and applied for further degradation of organosolv lignin. Over 5% Ni/HZSM-5, the highest yield of phenolic monomer was 19.5% with the selectivity of 66.7% towards 4-ethyl phenols (4-ethyl phenol and 4-ethyl guaiacol) at 300 °C, and liquid products with higher heating value (HHV) of 29.2 MJ kg−1 were obtained. The 5% Ni/HZSM-5 catalyst promoted the cleavage of intramolecular β-O-4 and Cβ-Cγ linkages, resulting in substantially decreased weight-average molecular weight (Mw)/number-average molecular weight (Mn) of the organosolv lignin from 2541/1064 Da to 562/391 Da, which implied the degradation of high-Mw oligomers to dimers and trimers. The catalyst also contributed to the hydrogenation of CαCβ bonds in unsaturated intermediates (coniferyl alcohol and coumaryl alcohol). The possible cleavage mechanism for the degradation of lignin-derived oligomers was also proposed.
ISSN:0016-2361
1873-7153
DOI:10.1016/j.fuel.2019.01.117