Study On Lignocellulosic Biomass Pretreatment Using Ionic Liquids And Preparation And Application Of Lignin Nanoparticles

Lignocellulosic biomass has attracted more and more attention because of its renewability and carbon neutrality in the transformation process.Lignocellulosic biomass is composed of lignin,cellulose and hemicellulose.It is the largest renewable carbon source and does not compete with food reserves.The polysaccharides（cellulose and hemicellulose）can be converted into biomass energy such as ethanol.Lignin can make small aromatics and advanced materials because of its aromatic structure and many unique properties.Focusing on the three components of lignocellulose biomass,this paper studied the sugar conversion of biomass pretreated with ionic liquid and the high-value application of lignin.1.A distillation ventilation device is designed for biomass pretreatment in diluted ionic liquid aqueous solution and circulating ionic liquid solutions.Four biomass types were studied:switchgrass,miscanthus,sorghum and pine.X-ray diffraction（XRD）was used to measure the interaction between biomass and IL.Small angle neutron scattering（SANS）was used to monitor the changes of pore structure in wet biomass samples.The enzymatic hydrolysis was tested by high performance liquid chromatography（HPLC）.2.Lignin from different biomass was extracted by enzymatic mild acidolysis lignin（EMAL）,including switchgrass,miscanthus,sorghum,pine,corncob and Eucalyptus.The interactions between these lignin and different solvents DMSO-d6,0.1 N Na OD solution and EG-d6 were studied by small angle neutron scattering（SANS）and ³¹P NMR.Aggregates were observed in DMSO and EG solutions.The degree of aggregation is determined by the ratio of aliphatic and phenolic hydroxyl content.In 0.1 N Na OD,another factor is the ionization of carboxyl and phenolic hydroxyl groups,which is involved in the dissolution and aggregation of lignin.3.Lignin nanoparticles（LNPs）were prepared by anti solvent/solvent exchange method.The microstructure was observed by dynamic light scattering（DLS）,small angle neutron scattering（SANS）and atomic force microscope（AFM）.Size,shape and compactness are important factors affecting the use of LNPs.These LNPs were obtained from sans data.It is found that there is a difference in the radius between SANS and DLS,which indicates that there is a large hydrated shell around LNPS in aqueous solution.4.The applications of lignin and LNPs were explored.The cytotoxicity of corncob lignin and corncob LNPS was studied and compared.It was proved that LNPS could reduce the cytotoxicity of lignin.Six kinds of grass lignin,including Miscanthus,sorghum and corncob,and six kinds of lignin,including Kraft,pine and eucalyptus,were separated by acetone,and the antibacterial properties of original lignin,acetone soluble lignin and acetone insoluble lignin were studied.