Toward Sustainable and Complete Wood Valorization by Fractionating Lignin with Low Condensation Using an Acid Hydrotrope at Low Temperatures (≤80 °C)

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Poplar wood was fractionated under a range of conditions using an inexpensive and recyclable commercial aromatic acid, p -toluenesulfonic acid ( p -TsOH), as an acid hydrotrope (AH). The fractionated cellulose-rich solid fraction demonstrated excellent physical and optical properties as papermaking fibers. The dissolved xylose can be dehydrated into furfural using the p -TsOH in the spent liquor without additional catalysts. The acid hydrotrope dissolved lignin (AHL) has high β-aryl ether linkage content (∼60%) and high molecular weight (∼4000 Da), similar to that of mill wood lignin (MWL). Increasing acid hydrotrope fractionation (AHF) severity increased AHL yield, but reduced β-aryl ether bonds, decreased molecular weight and increased AHL glass transition temperature. An AHL yield of 50% can be obtained while retaining approximately half of the β-O-4 linkages, beneficial for lignin valorization as a polymer in composites as well as for production of monomers or aromatics through subsequent depolymerization.