| With the continuous progress and development of society,the fossil resources become increasingly poor,and the environmental pollution caused by them can not be underestimated,so the development of new energy becomes more and more important.There is a rich renewable energy in nature-biomass energy,which is a energy that can be used to replace fossil fuels,and can be converted into biofuels and chemical products.The three major components of biomass are cellulose,hemicellulose and lignin.Among them,lignin is a kind of aromatic phenolic macromolecular compound,which can be degraded to produce aromatic chemical products,which has broad development and utilization prospects.Moreover,pyrolysis is one of the technique for the utilization of biomass.The discussion on the pyrolysis mechanism of biomass will help to better explore efficient pyrolysis technology of directional products.The structure of lignin obtained from different biomass is huge and different,and it is difficult to ensure that its primary structure is completely extracted.Therefore,it is difficult to study the microscopic mechanism of lignin directly from biomass,so people usually use various lignin models to carry out related research.This paper mainly discusses the degradation of lignin in the paper mulberry and the theoretical study on the pyrolysis of lignin model compounds.The results are as follows:Firstly,the lignin of paper mulberry was degraded in the mixed solvent of[BMIM]Cl-ethanol-water.The first step is the synthesis and characterization of[BMIM]Cl.The structure of[BMIM]Cl was confirmed by NMR,IR and quantum calculation.The solvent system of[BMIM]Cl-ethanol-water was used to optimize the catalytic degradation process of paper mulberry lignin.Degradation process optimized by orthogonal experiment:the ratio of ethanol/water was 1:1,reaction temperature was 70℃,the ratio of raw material/[BMIM]Cl was 5:4 and reaction time was 6 h..Secondly,in order to characterize the structure and morphology appearance of the materials before and after degradation,a variety of characterization methods are used,such as SEM,FT-IR,and XRD.The results showed that lignin in paper mulberry bark was dissolved.GC-MS analysis of the extract liquids showed that lignin was degraded into many small molecules containing methoxyl group,and some characteristic small molecules such as acetovanillin and 2-ethoxy-4-(2-propenyl)phenol were also detected.Thirdly,using acetophenone as raw material,syringone was synthesized by iodine substitution and methoxyl substitution on benzene ring.Followed by bromination of hydrogen atom on acetyl group to produceα-bromo syringone,and finally reacted with guaiacol to produceβ-O-4 lignin model compoundα-(2-methoxyphenoxy)-syringone.The structure of each product was confirmed by NMR analysis.The degradation of the model compound was studied in the solvent system of[BMIM]Cl-ethanol-water,and the small molecular compounds in the degradation solution were analyzed by GC-MS and many phenolic compounds were obtained.Finally,the enthalpy ofβ-O-4 bond lignin model compound-2,6-dimethoxy-4-(2-(2-methoxyphenoxy)ethyl)phenol at 298.15 K and 101.325 k Pa was calculated by density functional theory method,and the pyrolysis path of the model compound was Inferred.The results show that the thermal competition of the dimer is C_β-O hemolysis>C_β-O concerted decomposition>C_α-C_βhomolysis.Based on the theoretical analysis of the three pathways,it is concluded that the main pyrolysis products of the model compound are eugenol,catechol,phenol,2-methoxyphenol and4-ethyl-2,6-dimethoxyphenol. |
