Kinetic Modeling Study Of Lignin Pyrolysis

Lignin is an important component of lignocellulosic biomass,and is a polymer composed of benzene ring,multiple bridge bonds and side chains.The main bridge bonds of lignin are β-O-4,β-β and β-5 bonds.In recent years,lignin has been used as raw material in the field of biomass oil because of its renewable,high yield and high fuel value of aromatic products pyrolysis.In the study of lignin pyrolysis,the accuracy of the model is the key factor to accurately describe the pyrolysis process of lignin and predict the pyrolysis products in the pyrolysis numerical calculation.In this paper,the lignin structure and thermogravimetric experimental data which were published by scientists previously were used to verify the model proposed in this article.At the same time,thermogravimetric/photoionization mass spectrometry experimental platform was used to detect the important pyrolysis products of lignin βO-4 dimer model compounds in real time,and the quantitative measurement of the main products was realized.In the measurement of mass loss,the components of escaped products were detected online and in real time by photoionization time-of-flight mass spectrometry,and the multi-mass spectra changing with time and temperature were obtained to quantitatively detect the pyrolysis products of dimer.In terms of lignin pyrolysis model,this paper developed lignin macromolecular pyrolysis model including bridge bond and side chain;and developed ODEs method for calculating solid pyrolysis.Based on this method,lignin pyrolysis reaction mechanism including 103 species and 204 reactions was established.The experimental results were used to verify the model,and the results showed that the lignin pyrolysis model developed in this paper could well predict the pyrolysis behavior of lignin and its model compounds in the pyrolysis process.In addition,the pyrolysis process was quantitatively calculated by reaction path analysis.The results show that the three bridge bonds are mainly decomposed by hydrogen extraction and β bond breaking reaction.In summary,the lignin pyrolysis model developed in this paper can well predict the pyrolysis process of lignin and its dimer model compounds,which indicates that the accuracy and applicability of the model will provide theoretical guidance for the for future lignin pyrolysis research.