(202a) Rapid and near-complete dissolution of wood lignin at ? 80°C using a recyclable acid hydrotrope for sustainable production of high-value building blocks

Here we report the discovery of the hydrotropic properties of a recyclable aromatic acid, p-toluenesulfonic acid (p-TsOH), for 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 for 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 170°C for 2 h with alkaline pulping. p-TsOH fractionated wood into two fractions: (1) a primarily carbohydrate-rich water-insoluble solid fraction that can be used for sustainable production of high-value building blocks, such as dissolving pulp fibers and lignocellulosic nanomaterials, and/or sugars through subsequent enzymatic hydrolysis, and (2) a spent acid liquor stream containing mainly dissolved lignin that can be easily precipitated as lignin nanoparticles simply by diluting the spent acid liquor to below the minimal hydrotrope concentration. p-TsOH has a low water solubility, which facilitates efficient recovery simply using commercially proven crystallization technology by cooling concentrated spent acid solution to ambient temperatures to achieve environmental sustainability.