The influence of extraction method and structure type on the pyrolysis behavior of lignin was investigated. The functional groups and pyrolysis characteristics of Klason lignin extracted from cotton stalk and walnut shell by the Klason method (labeled as KCSL and KWSL

respectively)

and milled wood lignin extracted from walnut shell via the Björkman method (labeled as BWSL)

were analyzed with Fourier transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). The results were compared with commercial alkali lignin (CAL). The FTIR results revealed that alkali lignin

cotton stalk lignin and walnut shell lignins were Type G

Type GS and Type HGS

respectively. The pyrolysis results from Py-GC/MS suggested that the products distribution of various lignins were affeted by material type and extraction method greatly. The contents of catechol derivatives obtained from KCSL

KWSL and BWSL were 28.18%

18.12% and 35.11%. Meanswhile modification of BWSL was mainly attributed to the breakage of benzyl aryl ether linkages

whereas cleavage of ether bonds at the α-and β-positions on the propanoid side chain was the marked feature of Klason lignin.