Toward sustainable and complete wood valorization by fractionating lignin with low condensation using an acid hydrotrope at low temperatures (≤80 °C)

Abstract

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.

Citation

Cheng, Jinlan; Hirth, Kolby; Ma, Qianli; Zhu, Junjun; Wang, Zhaojiang; Zhu, J. Y. 2019. Toward sustainable and complete wood valorization by fractionating lignin with low condensation using an acid hydrotrope at low temperatures (≤80 °C). Industrial & Engineering Chemistry Research. 58(17): 7063-7073.