The Catalyzing Liquefaction Of Kraft Lignin In Iminazolium Ionic Liquid [BMIm]Cl

Kraft lignin (or alkali lignin) is a major constituent part of pollutants in black liquor produced from paper and pulping industry. Its structure is rich in benzene ring which is an ideal raw material for produce value-added chemicals. The conversion and degradation of lignin is a hotspot but an aporia in the reasearch of biomass energy utilization all the time. The appearance of ionic liquids made it become an effective tool as a new class of green solvent in lignin decomposition of macromolecule depolymerization. This dissertation carried out a series of studis on the catalyzing liquefaction of Kraft lignin in iminazolium ionic liquid [BMIm]Cl after summarized related literature, and divided into four parts as follow.Firstly, the essential ionic liquid [BMIm]Cl was synthetized from N-methylimidazole and n-chlorobutane at70?and rinsed by ethyl acetate. The characterizations from'H NMR, FT-IR and GC-MS shown that the water content of synthetic [BMIm]CI is under1%.Secondly, a series of [BMIm]Cl aqueous solution from0.043mol·L-1to2.152mol·L-1were prepared by progressive dilution method, and the relationships of density, viscosity, pH value, surface tensions and conductivity to the concentrations and temperatures from25?to55?were measured. The results of data fitting and theoretical derivation shown as follow.(1) The temperature has linear reduce models on the density and pH value, yet linear increase models on molar conductivity. The relationship between temperature and viscosity is according with Vogel-Tammann-Fulchers equation.(2) The water content of [BMIm]Cl(as concentration in experiments) has linear reduce models on the density, and its impact is higher than the temperature. As on the viscosity has parabola relevant models. While the concentration is.just under0.5mol·L-1, the pH value may be affected a little diversity. A new relation was found between surface tensions and concentrations as a l/?-c([BMIm]Cl) linear increase model. But there is an exponential model between molar conductivitys and concentrations, or an alternating Kohlrausch quasi-parabola model can be used. However, the common laws of strong electrolyte dissolving in water were inaccuracy.(3) Theoretical calculation about conductivity shown that a positive adsorption was occurred during [BMIm]Cl contacted the water surface, and the [BMIm]Cl molecule has a shifting trend in water because of the attract of stronger polarity in water molecule. In addition tests,[BMIm]Cl-AlCl3was found as a instable structure in aqueous solution.Thirdly, a succession of experiments exploring the theory on the catalyzing liquefaction of Kraft lignin dissolving in [BMIm]Cl aqueous solution based on the above quantitative relations.(1) The partial solubility parameters were calculated using Hansen solution theory. The results shown that common iminazolium ionic liquid can catalytic dissolve lignin in theory, and the dissolving capacity is as [BMIm]PF6>[BMIm]BF4>[BMIm]Cl, better than most organic solvents.(2) The solubility experiments shown that the equilibrium solubility of Kraft lignin will increase as exponential model with the concentration of [BMIm]Cl aqueous solution. It will be deacrease conversely if the [BMIm]Cl concentration too low as below0.0005g-L-'. Quantum chemistry computing data accounted for this phenomenon, strong intramolecularly hydrogen bonds formed in [BMIm]Cl molecule lead to electron polarization in aqueous solution.(3) The polarity change of [BMIm]Cl aqueous solution will affect the solubility of Kraft lignin. Dielectric constant grown made the solubility reduce in proportion, the partial solubility parameters has oppositive effect yet. The melting points and solubility of pyrocatechol, resorcinol and hydroquinone as the model lignans of lignin shown that, stable para-position functional groups in lignin is the key difficulty of liquefaction about Kraft lignin dissolving in water, and the intramolecularly hydrogen bonds of ortho-position structures blocked the interaction with water make the very low lignin solubility. Different para-position substituent groups were also be tested using acetanilide derivatives as model compounds. While the para-position substituent groups have hydrophobicity, the solubility will be decrease, but hydrophilicity makes increase.(4) Using DSC curve to calculate the fusion temperature of Kraft lignin is Tm=706.22K, the specific mass enthalpy is122.42J·g-1. The solubility of Kraft lignin at any temperature and [BMIm]Cl concentration can be calculated using non-regular solution theory based on these parameters.Finally, to confirm the catalytic action on the Kraft lignin structure of [BMIm]Cl, catalyzing oxidating degradation experiments of Kraft lignin were proceeded in [BMIm]Cl-30%H2O2aqueous solution.(1) The structure of regenerated lignin treated from liquefaction of [BMIm]Cl-H2O2was changed. FT-IR shown that ortho-position bi-substituents in benzene rings increased, the structure of Kraft lignin was depolymerization partly and generated side chains of benzene rings. XRD shows a little crystalling impurities were clean in Kraft lignin after treatment, some catalyzing oxidating degradation were occured. SEM shown the crystalling Kraft lignin was transformed into porous layered stripping structure.(2) The Kraft lignin total weight loss is43.93%at700?, but the one of regenerated lignin is60.77%, and thermoanalysis shown that the temperature of the lignin after treated maximum decompose velocity is reduced nearly40?than before. A first order reaction was used in modeling simplification. Coats and Redfern method was used to analyze the kinetic parameters in the temperature range of pyrolysis kinetic control process about the lignin before and after treatment. The activation energy of the regenerated lignin is2.2times greater than the non-treated one.(3) Some stable and easily pyrolytic chemical structures were generated after catalyzing oxidating degradation in [BMIm]Cl-H2O2mixed solution from pyrolysis kinetics model which was confirmed with coupled FT-IR. The IR spectra shows the concentration of CO2in pyrolysis gases from regenerated lignin is limited, the grown of aromatic series with ortho-disubstitution and para-disubstitution functional groups is signify both in quantity and variety.(4) The solubility experiments shown that influence factor can be sorted in variance ratio as [BMIm]Cl dosage>solid-to-liquid ratio>liquefaction temperature. The structure of lignin was activated in the progress of oxidating degradation with the [BMIm]Cl, which made chromophores decrease and has some hydrolyzing catalytic action.