Analysis of wheat straw lignin by thermogravimetry and pyrolysis–gas chromatography/mass spectrometry

The thermogravimetric characteristics of wheat straw enzymatic acidolysis lignin (EMAL) were analyzed. At a temperature above 200 °C, the pyrolysis rate of wheat straw EMAL was clearly accelerated, since all DTG curves and the maximum temperature corresponding to pyrolysis shifted to high temperature areas, two maxima being also recorded on the DTG curves. The thermogravimetric dynamics parameters of wheat straw EMAL were calculated by the methods of Kissinger and Ozawa, respectively; the activation energy of wheat straw EMAL was of 103.92 and 107.69 kJ mol−1, respectively, and the frequency factor, ln A, of 19.21 and 20.60 min−1. Pyrolysis–gas chromatography mass spectrometry (Py–GC/MS) was applied to analyze wheat straw EMAL at 500 °C for investigating fast thermal degradation products of lignin. The identified key marker compounds were the derivatives of the three kinds of lignin basic units (guaiacyl, syringyl, and hydroxyphenyl units), but the guaiacyl units dominated over the lignin-derived products.