Extraction Of Lignin From Walnut Shell With Tetrahydrofurfuryl Alcohol

Lignin has a wide range of applications in the preparation of aromatic compounds,carbon fibers,resins,and polymer.Its application mainly depends on the quality of the lignin produced.In the commonly used extraction methods such as alkali precipitation,acid precipitation,organic solvents,and high boiling alcohol,the lignin prepared by the high boiling alcohol method is characterized with higher purity,better dispersibility,and more active groups,which is beneficial to subsequent processing.In this study,acidified tetrahydrofurfuryl alcohol was used to extract lignin from walnut shells under milder conditions mainly including the following three aspects:(1)Optimization of lignin extraction from walnut shells by acidified tetrahydrofurfuryl alcohol.The effect of acid concentration on lignin extraction with acidified tetrahydrofurfuryl alcohol was firstly explored.Subsequently,different factors such as solid-liquid ratio,reaction time and temperature were investigated.The results show that the optimal reaction solid-liquid ratio is 20 %.The reaction time and temperature are positively correlated with the lignin yield.With time increasing from 1 h to 4 h,the yield increased from 34 % to 55 %;as the temperature increased from 105 ? to 135 ?,the yield increased from 30 % to 78 %.(2)Investigation of the effect of water content on lignin extraction with acidified tetrahydrofurfuryl alcohol.Under certain temperature,the presence of water is conducive to the degradation of hemicellulose in biomass,thereby promoting the dissolution of lignin.Through the influence of different water content on the extraction of lignin with acidified tetrahydrofurfuryl alcohol,the optimal water content was determined to be 85 %.Next,the effects of solid-liquid ratio,reaction time,and temperature on the extraction of lignin with aqueous acidified tetrahydrofurfuryl alcohol were studied.The results show that the optimal solid-liquid ratio is 20 %,the reaction time and temperature are positively correlated with the yield,and the reaction temperature has a greater influence on the yield.Under the conditions of 120 ?,1 h,20 % solid-liquid ratio,175 m M acid concentration,and85 % tetrahydrofurfuryl alcohol purity,the purity of lignin was 95.20 %.(3)Dissolution kinetics study and stepwise lignin extraction at different temperatures.In order to investigate the lignin dissolution at different condition,the lignin dissolution kinetics was carried out at at 120 ? and 135 ?.In the meantime,the walnut shells were subjected to stepwiseextraction at intervals of 0.50 h through continuous replacement of new solution.The results show that the dissolution rate of lignin at 135 ? is significantly higher than 120 ?.The optimal extraction condition of lignin is 135 ?,1.50 h,20 % solid-liquid ratio,175 m M acid concentration,99.80 % tetrahydrofurfuryl alcohol.The purity of the obtained lignin was 89 % and the yield was 69.30 %.