Catalytic effect of metal chlorides on analytical pyrolysis of alkali lignin

Abstract

The effect of KCl, CaCl2 and FeCl3 as additives on pyrolysis performance of alkali lignin was examined using thermogravimetric analyzer/Fourier transform infrared spectrometer (TG-FTIR) and pyrolysis–gas chromatography/mass spectrometry (PGC/MS). Notable differences of catalytic effects were observed after different metal chlorides were added. The yield of residual carbon and gases with low molecular weight increased remarkably with the addition of KCl. FeCl3 and CaCl2 had a promoting influence on the thermal cracking of alkali lignin, resulting in a decrease of the residual carbon formation by 2.7% and 3.5%. All additives played an active role in promoting the content of active phenols obtained from pyrolyzing the alkali lignin. During the catalytic pyrolysis process, the yields of small-molecule gases were in the order of CO2>H2O>CH4>CO, the capability of catalytic thermal cracking of alkali lignin by three metal additives was ranked as such: Fe3+>Ca2+>K+, and the ability of generating small-molecule gases by the additives was in the order of K+>Fe3+>Ca2+.