Pyrolysis Properties of Lignins Extracted from Different Biorefinery Processes

Abstract

The non-isothermal and isothermal pyrolysis properties of H lignin and P lignin extracted from different biorefinery processes (such as supercritical water hydrolysis and fast pyrolysis) were studied using thermogravimetry analysis (TGA) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). The lignins were characterized by ultimate/proximate analysis, FT-IR and GPC. Based on the thermogravimetry (TG) and derivative thermogravimetry (DTG) curves, the thermal decomposition stages were obtained and the pyrolysis products were analyzed at each thermal decomposition stage of non-isothermal pyrolysis. The isothermal pyrolysis of lignins was also carried out at 400, 500, and $600^{\circ}C$ to investigate the pyrolysis product distribution at each temperature. In non-isothermal pyrolysis, P lignin recovered from a fast pyrolysis process started to decompose and produced pyrolysis products at a lower temperature than H lignin recovered from a supercritical water hydrolysis process. In isothermal pyrolysis, guaiacyl and syringyl type were the major pyrolysis products at every temperature, while the amounts of p-hydroxyphenyl type and aromatic hydrocarbons increased with the pyrolysis temperature.

Fig. 1. FT-IR spectra of lignins.

Fig. 3. Chromatograms of non-isothermal pyrolysis of lignins.

Fig. 2. (a) TG and (b) DTG curves of H lignin and P lignin.

Table 1. Ultimate and proximate analysis of H lignin and P lignin

Table 2. Molecular weight and poly dispersity of lignins.

Table 3. Thermal decomposition stages and pyrolysis char yield

Table 4. Pyrolysis products of H lignin and P lignin (H: p-hydroxyphenyl type, G: guaiacyl type, S: syringyl type, C: catechol)

Table 5. Product distribution of non-isothermal pyrolysis of lignins

Table 6. Product distribution of isothermal pyrolysis of lignins