Here we present the discovery of the hydrotropic properties of a recyclable aromatic acid, p-toluenesulfonic acid (p-TsOH), for potentially low-cost and efficient fractionation of wood through rapid and near-complete dissolution of lignin. Approximately 90% of poplar wood (NE222) lignin can be dissolved at 80 °C in 20 min. Equivalent delignification using known hydrotropes such as aromatic salts can be achieved only at 150 °C or higher for over 10 h, or at 150 °C for 2 h with alkaline pulping. The dissolved lignin are relatively native state and can be easily precipitated as lignin nanoparticles simply by diluting the spent acid liquor to below the minimal hydrotrope concentration. Our NMR analyses of the dissolved lignin revealed that p-TsOH can depolymerize lignin via ether bond cleavage and separate carbohydrate-free lignin from the wood. p-TsOH has a relatively low water solubility, which can facilitate efficient recovery simply using commercially proven crystallization technology by cooling the concentrated spent acid solution to ambient temperatures to achieve environmental sustainability through recycling of p-TsOH.

Producing lignin nanoparticles directly from raw lignocelluloses at ≤ 80 °C in an aqueous system using a recyclable acid hydrotrope

255th National Meeting (2018)

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