Predicting lignin depolymerization yields from quantifiable properties using fractionated biorefinery lignins

Thanaphong Phongpreecha

doi:10.1039/c7gc02023f

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Predicting lignin depolymerization yields from quantifiable properties using fractionated biorefinery lignins

2017-01-01

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Thanaphong Phongpreecha

DOI：10.1039/c7gc02023f

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Abstract

En 中文

Lignin depolymerization to aromatic monomers with high yields and selectivity is essential for the economic feasibility of many lignin-valorization strategies within integrated biorefining processes. Importantly, the quality and properties of the lignin source play an essential role in impacting the conversion chemistry, yet this relationship between lignin properties and lignin susceptibility to depolymerization is not well established. In this study, we quantitatively demonstrate how the detrimental effect of a pretreatment process on the properties of lignins, particularly beta-O-4 content, limit high yields of aromatic monomers using three lignin depolymerization approaches: thioacidolysis, hydrogenolysis, and oxidation. Through pH-based fractionation of alkali-solubilized lignin from hybrid poplar, this study demonstrates that the properties of lignin, namely beta-O-4 linkages, phenolic hydroxyl groups, molecular weight, and S/G ratios exhibit strong correlations with each other even after pretreatment. Furthermore, the differences in these properties lead to discernible trends in aromatic monomer yields using the three depolymerization techniques. Based on the interdependency of alkali lignin properties and its susceptibility to depolymerization, a model for the prediction of monomer yields was developed and validated for depolymerization by quantitative thioacidolysis. These results highlight the importance of the lignin properties for their suitability for an ether-cleaving depolymerization process, since the theoretical monomer yields grows as a second order function of the beta-O-4 content. Therefore, this research encourages and provides a reference tool for future studies to identify new methods for lignin-first biomass pretreatment and lignin valorization that emphasize preservation of lignin qualities, apart from focusing on optimization of reaction conditions and catalyst selection.

Keywords:

C-O BONDS

MODEL COMPOUNDS

AEROBIC OXIDATION

KRAFT LIGNIN

ARYL ETHERS

CONDENSATION-REACTIONS

ENZYMATIC-HYDROLYSIS

CATALYTIC-OXIDATION

ALKALINE OXIDATION

MONOMER PRODUCTION