Experimental Study Of Lignin Pyrolysis

As one of the technologies that can convert biomass into liquid fuels, biomass pyrolysis has aroused great attention worldwide in recent decades. However, the diffusion of the technology has been habited due to the complex composition of bio-oil and its unstable properties, which may be attributed to the lack of the sound understanding and deep research of the pyrolysis mechanism of biomass, especially of the physiochemical properties and related reaction mechanism of lignin. Supported by relevant national research programs, an integrated research of lignin properties and pyrolysis mechanism is presented in this thesis.Different kinds of Lignin were extracted from Manchurish ash (hardwood) and Mongolian Scots pine (softwood) using Bjorkman and Kalson procedures. Elemental analysis,'H-NMR spectrum analysis and FTIR analysis of lignins was carried out to have a understanding on difference of structure characteristics such as content of function group and elemental composition. The ash lignin has both syringl and guaiacyl units, showing the characteristics of lignin in hardwood, while the pine lignin only has guaiacyl units.The pyrolysis behavior of MWL and KL from different wood was studied by TG-FTIR, and obvious diversities were found. The formation mechanisms of the main products were investigated. The fast pyrolysis of MWLs was performed on a fast pyrolysis apparatus. Higher yield of bio-oil was achieved during the pyrolysis of ash MWL, while more char was obtained during the pyrolysis of pine MWL. The yield of alcohols is related to the content of methoxyl groups, while the contents of guaiacol and syringol could be used to distinguish the lignin species.In order to investigate the interaction between lignin and other components, four synthesized samples were prepared and pyrolysis behaviors were studied on both TG-FTIR and a fast pyrolysis apparatus. The interactions between lignin and other components result in lower bio-oil yield and higher gas and char yield. Both cellulose and hemicellulose restrained the formation of hydrocarbons gases during lignin pyrolysis. Lignin has little influence on the fonnation of 2,5-diethoxy-tetrahydrofuran and levoglucosan during cellulose pyrolysis while hemicellulose strongly promotes 2,5-diethoxy-tetrahydrofuran and depressed that of levoglucosan. Lignin intensively restrained formation of acetic acid and furfural during hemicellulose pyrolysis, while cellulose promotes them. Cellulose and hemicellulose has positive effect on the formation of the phenols during the lignin pyrolysis.