Comparative analysis of micro-crystal structures and bio-oils from pyrolyisis of two barks

Using softwood bark of Chinese fir and hardwood bark of eucalyptus as raw materials, the variation of their micro-crystal structures before and after pyrolysis was compared using X-ray diffraction. The components of bio-oils from 2 barks were analyzed contrastively with gas chromatograph-mass spectrometer and gel permeation chromatography. The results show that fiber structures and fatty chain structures in the bark are decomposed and destroyed. The main components of bio-oils, containing acids, ketones, phenols, alcohols, aldehydes, sugars and esters, are similar between the Chinese fir bark and eucalyptus bark, but the relative concentrations are different. On the contrary, the pyrolysis of eucalyptus bark produces more acids and ketones than Chinese fir bark, but phenols, alcohols and sugars are just the reverse. The phenols account for a large proportion of bio-oils, especially phenol and catechol. The molecular weight of bio-oils obtained from the bark is mainly concentrated from 300 to 500 g/mol; however, the relative concentration of eucalyptus bark (48.18%) is less than that of Chinese fir bark (61.14%).