Extraction Of Lignin From Corncob Using High Boiling Solvent And Study On Thermal Ananlysis Kinetics

As people continue to strengthen the understanding of the problem of environmental pollution and the increasing scarcity of fossil energy,natural polymer with renewable,biodegradable,non-toxic and good safety features has attracted more and more attention.Lignin is the only renewable aromatic natural macromolecule material,the research of lignin attracted people's attentions.In this study,lignin was extracted from corncob using high boiling solvents(1,4-butanediol,ethylene glycol and glycerol)with little of sulfuric acid or hydrochlorie acid as eatalyst.The effects of reaction temperature,extraction agent concentration,solid-liquid ratio and reaction time on the yield of lignin were investigated in order to obtain the optimal extracting condition.The optimal condition using 1,4-butanediol as an extraction solvent is:reaction temperature 200?,solid-liquid ratio 1:10,1,4-butanediol concentration 90%,reaction time lh,a small amount of sulfuric acid as catalyst,and the yield of lignin reached 37.03%.The optimal condition using ethylene glycol as an extraction solvent is:reaction temperature 190?,solid-liquid ratio 1:10,ethylene glycol concentration 90%,reaction time lh,a small amount of hydrochloric acid as catalyst,and the yield of lignin reached 36.37%.The optimal condition using glycerol as an extraction solvent is:reaction temperature 200°C,solid-liquid ratio 1:10,glycerol concentration 90%,reaction time lh,a small amount of hydrochloric acid as catalyst,and the yield of lignin was 35.75%.The extracted HBS(high boiling solvent)lignin was characterized by the elemental analysis,IR spectra,and dissolution properties.The result of FTIR showed that the HBS lignin preserved many active functional groups,had the higher chemical activity.The modified lignin derivatives will have wide application prospect.The extracted HBS lignin was characterized by the thermal analysis.HBS lignin pyrolysis includes three main processes of intramolecular dehydration process,thermal cracking,coking.HBS lignin pyrolysis gas products are numerous and complex.Through analysis of the infrared spectra of gas,gas products are mainly water vapor,methane,carbon dioxide,carbon monoxide,aldehydes,ketones,carboxylic acids and other substances.Through the research of HBS lignin pyrolysis kinetics by Coats-Redfem method,activation energy and pre-exponential factor of HBS lignin pyrolysis was calculated.The activation energy E is in the range of 20.89 kJ/mol?30.15kJ/mol.The pre-exponential factor A ranges from 1.78 to 74.75 min-1.