Design And Screening Of Ionic Liquids And Their Application In Biomass Dissolutio

Due to the consumption of petroleum energy,the utilization of biomass resources has attracted more and more attention.Lignocellulose mainly includes cellulose,hemicellulose and lignin,which is an important component of plant cell wall and contains abundant biomass energy.However,due to the complex composition and abundant bond types,it is difficult to effectively extract various components in lignocellulose.Ionic liquids are excellent solvents for lignocellulose pretreatment.However,due to the wide variety of ionic liquids,how to screen ionic liquids to efficiently dissolve biomass is a bottleneck.Studies have shown that computational chemistry methods built using accurate solute models have proven effective in solvent screening.The main contents of the paper include:1.We established 6 hemicellulose models through COSMO-RS,and obtained the optimal hemicellulose model(Intermediate dimers of xylan chains,MDXC)by fitting the solubility prediction of the model in various ionic liquids with the experimental data reported in the literature.The effects of ionic liquids on the dissolution of hemicellulose were studied in terms of anions and cations,and it was found that compared with cations,the interaction between anions and hemicelluloses played a major role in the dissolution process.With the increase of dissolution temperature,the effect of cations on the dissolution of hemicellulose was gradually significant.The ionic liquids whose anions are Ac~-,Cl~-,HCOO~-,Gly~-and DMSO~-have advantages in the dissolution of hemicellulose.In addition,theσ-profile method was found to be very efficient for large-scale ionic liquid screening.2.Cellulose and lignin models were constructed and optimized.It was found that the intermediate monomer model of cellotriose and the lignin model composed of6 monomer molecules according to a specific ratio were the optimal models for cellulose and lignin,respectively.The solute model can objectively reflect the chemical environment of the solute in the ionic liquid system.Through the analysis of solubility prediction data,it is found that activity coefficient and excess enthalpy are reliable parameters to evaluate the solubility of ionic liquids.In the dissolution of lignocellulose in ionic liquids,hydrogen bonding interactions play a major role,followed by mis-fit energy and van der Waals energy.3.After combining the three optimal models of lignocellulose and the prediction data of solubility,the scheme exploration and economical discussion on the separation of lignocellulose mixed components by ionic liquid were carried out.A two-step strategy for separating lignin first and then cellulose was finally determined.Several potential ionic liquids,such as[Ampyrr][HCOO],[Ampyrr][Br],were found to be useful for efficient separation of lignin-cellulose,hemicellulose components.In the separation of cellulose-hemicellulose mixed components,[EMmor][PG],[Ampyrr][PG]and other ionic liquids have better results.The economic analysis and discussion are beneficial to the continuous advancement of the experimental research and industrial production of ionic liquids in dissolving and separating lignocellulose components from the application point of view.This study explains the thermodynamic behavior of lignocellulose and ionic liquid solvent systems,which is important for screening and predicting ionic liquid solvent systems.