Study On Dissolution And Separation Of Corn Straw By Ionic Liquid System

Lignocellulosic materials are the most abundant renewable resources and are difficult to dissolve in conventional organic solvents,but ionic liquids are excellent solvents for lignocellulosic materials.In view of the distribution characteristics of lignin,cellulose and hemicellulose in lignocellulose,this paper proposes to destroy the protective layer of lignin hemicellulose composite by introducing additive to achieve rapid dissolution of lignocellulose in ionic liquids.The research of reclaiming high-purity cellulose materials and the degradation inhibition of cellulose in the process of ionic liquid dissolution were studied.On this basis,the one-step direct spinning of corn stalks was realized.The main findings are as follows:(1)A method for extracting high-purity cellulose from corn straw in one step was proposed and the separation mechanism was obtained.Studies have shown that in the ionic liquid-sulfamic acid(1-butyl-3-methylimidazolium chloride[C4mim]Cl-AS)binary system,corrn straw can be extracted in 1 h under 100? with a purity of 99%.The degree of polymerization of cellulose decreased slightly,and the crystal structure changed from type ? to type ?.The addition of sulfamic acid will increase the hydrogen bond alkalinity ? value of the solvent system,which is beneficial to the removal of lignin.The additive does not destroy the microporous structure of the regenerated cellulose,nor does it destroy the basic skeleton of the ionic liquid.There is a series of{[C4mim]nCln+i}-ionic cluster structure in[C4mim]Cl.When sulfamic acid is added,Cl' will be substituted by sulfamic acid.The substituted Cl-is freed from the binding of cations making it easier to enter the interior of the cellulose backbone to destroy hydrogen bonds,thereby promoting the dissolution and separation of corn straw;(2)Study on the inhibition of cellulose degradation in ionic liquids by amino acids.The results show that amino acids can effectively inhibit the degradation of cellulose when dissolved in ionic liquids.The system composed of amino acids and ionic liquids can be recycled.It shows that cellulose does not react with L-arginine,and the addition of L-arginine can significantly improve the mechanical properties of cellulose spinning.L-arginine forms hydrogen bonds with the hydroxyl group of the cellulose to occupy at least one of the hydroxyl groups(OH2?OH3?OH6')and(OH6?OH2'?OH3').This will prevent[Bmim]Cl from simultaneously forming hydrogen bonds with the hydroxyl groups(OH2?OH3?OH6')or(OH6?OH2'?OH3')of cellulose,which successfully leads to inhibiting the degradation of cellulose;(3)It was studied to completely dissolve corn stalks and directly spun to obtain cellulose fiber materials with good mechanical properties.Studies have shown that when the amount of L-arginine is 0.30 g,the dissolution temperature is 150?,and the time is 11.5 h,the corn stover can be fully dissolved and spun at this time.The addition of L-arginine can increase the hydrogen bond basicity ? of the solvent system from 0.89 to 0.96,which is beneficial to delignification and dissolution of cellulose;(4)The[C2mim][BF4]-L-arginine system was designed to extract lignin from straw,and good extraction effect was obtained.Studies have shown that when the amount of L-arginine is 0.40 g,the cellulose yield is 97%,and the lignin removal rate is 84%.After the reaction is stopped,the[C2mim][BF4]-L-arginine can be quickly recovered.During the extraction process,the lignin hemicellulose complex LCCPL was selectively depolymerized into small pieces,but the cellulose in the straw did not degrade and the crystal structure did not change.Four cycles of experiments show that[C2mim][BF4]-L-arginine system has good recyclability.