Chemical and thermal analysis of lignin streams from Robinia pseudoacacia L. generated during organosolv and acid hydrolysis pre-treatments and subsequent enzymatic hydrolysis. uri icon

abstract

  • Lignin streams produced in biorefineries are commonly used to obtain energy. In order to increase the competitiveness of this industry, new lignin valorization routes are necessary, for which a depth characterization of this biological macromolecule is essential. In this context, this study analyzed lignin streams of Robinia pseudoacacia L generated during organosolv and acid hydrolysis pre-treatments and during the subsequent enzymatic hydrolysis. These lignins included dissolved lignins from pre-treatment liquors and saccharification lignins from pretreated materials. Chemical composition and structural features were analyzed by analytical standard methods and Fourier Transform Infrared spectroscopy (FTIR), size exclusion chromatography (SEC), C-13 solid state nuclear magnetic resonance (C-13 NMR) and H-1-C-13 two-dimensional nuclear magnetic resonance (2D NMR); while thermal characterization included thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In general, all studied lignins contained a predominance of beta-O-4' aryl ether linkages, followed by resinol (beta-beta') and phenylcoumaran (beta-5'), with a predominance of syringyl over guaiacyl and hydroxyphenyl units. Nevertheless, the dissolved lignins revealed a removal of linkages, especially beta-O-4', leading to an enrichment of phenolic groups. Moreover, high thermal stability and good thermoplasticity were characteristics of these lignins. Contrary, the saccharification lignins exhibited a more intact structure, but with an important remaining carbohydrates content. (C) 2019 Elsevier B.V. All rights reserved.

publication date

  • 2019
  • 2019