| With the rapid development of the society,the renewable lignocellulosic biomass as raw material has attracted increasing attention.However,how to effectively separate biomass resources and make full use of them is still a difficult problem at present.If the three major components of biomass can be effectively separated and converted into energy or high value-added products that are easy to store and use,then the global energy crisis and environmental deterioration problems can be possiblely solved.China is a large coconut producer,especially in hainan and guangdong.Coir fiber is a by-product of coconut fruit.It is not only rich in reserves,but also inexpensive and widely used.The lignin in coconut fiber is relatively high,and the content is about 31%～36%.If the coconut shell fiber can be reasonably used,it will be able to alleviate the above problems.In this article,the separation of coir fibers was studied under the condition of low temperature(90 degree)and microwave heating,based on the main line of high boiling alcohol-ethylene glycol as solvent.The main contents run as follow:1.The coir fiber was used as the experimental material and ethylene glycol(EG)as the solvent to separate the components under the acid condition,and the ethylene carbonate(EC)was added for the first time to make the whole reaction at a lower temperature(90 degrees C).Firstly,different mole ratio of ethylene glycol(EG)and ethylene carbonate(EC)was researched to compare the pretreatment effect,it was found that under the same reaction conditions,delignification of cellulosic material isolated by EG/EC(4:1)was the highest value,which was 49.87%and the lignin yield was 17.22%at the same time.Then the orthogonal test was designed with the reaction temperature,reaction time and acid concentration as three factors,and the change of lignin yield was observed,and the optimal experimental scheme was selected.After pretreatment,the content of hemicellulose and lignin in the fiber is obviously decreased,and the crystallinity of cellulose was not destroyed,it is still a typical I type crystal structure and the lignin was typicle HGS.When the molar ratio of ethylene glycol/ethylene carbonate was 4:1,the weight average molecular weight and the polydispersity coefficient(9.73)of the lignin are the smallest,which is beneficial to the application of the lignin.2.Using microwave heating method to separate the coir fiber and study the effect of catalyst on the yield of lignin.Firstly,ethylene glycol was only used as solvent and changed the acid type to explore the yield change of lignin.The results showed that when H2SO4 and HCl were used as catalysts,the yield of lignin was relatively large,which was 4.05%and 7.22%respectively.Secondly,when the molar ratio of ethylene glycol/ethylene carbonate was 4:1,adding H2SO4 and HCl as the catalyst,the yield of lignin has no obviously change.Finally,using ionic liquid as catalyst,the yield of lignin increased significantly.When using ethylene glycol alone,the yield of lignin and delignification rate were the largest,which were 27.18%and 89.12%respectively.3.Under microwave assisted heating and ethylene glycol as solvent,study on the effects of reaction power,reaction time,ethylene glycol concentration and ionic liquid on the yield of lignin.The orthogonal test was designed to determine the best reaction conditions was microwave power at 0.4KW,microwave heating time at 25min,volume fraction of ethanol at 95%,ionic liquid dosage at 1g and the lignin yield average value was 27.31%and the product obtained was characterized with infrared spectrum analysis,UY and FT-IR.It can be concluded that the content of lignin and hemicellulose in the fibers treated by ethylene glycol is greatly reduced,and the yield of lignin can reach 27.65%under the best condition.UV and infrared spectrum analysis showed that the lignin retained the original structure.Electrochemical studies were carried out by measurement of cyclic voltammetry(CV)and AC impedance tests about lignin,coir fiber and the alkali lignin.The results demonstrate that capacitive performance of ethylene glycol lignin and coir fiber are better than alkali lignin,have bright prospects in future research and application in electrode materials. |
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