Study On Catalytic Degradation Of Lignin In Ionic Liquid [BMIm]Cl Composited Hydrochloric Acid

Though lignin is the second kind of organic polymer compounds which can replace fossil fuels such as oil and coal to produce aromatic compounds, the researchers pay little attention to the conversion of lignin and discover its potential value and added value because of the complexity of the lignin molecular structure. In order to broaden the routes of the use of lignin, there are three aspects of work in this paper.First, the modification of lignin was investigated. Primarily, hydrochloric acid in ionic liquid [BMIm]Cl was used to modify lignin; Next, the modern chemical analysis instruments like FT-IR, SEM and TGA were applied to characterize the structure and thermal stability of lignin and modified lignin; Finally, the reactivity of modified lignin was tested which is applied to synthesize the epoxy resin. The analysis of FT-IR shows the structure of lignin molecular changes, such as that the content of O-H is increased and that C=C, C-O-C and C=O included in lignin molecular break. The analysis of SEM shows the structure and morphology of lignin molecular are transformed from the amorphous, non-crystal structure of the original lignin molecular into the block, crystal structure of the modified lignin molecular and that the molecular aggregation size is increased. The analysis of TGA shows that the thermal stability of modified lignin is decreased, however, its hydrophilicity is enhanced. The experiment of modified lignin used in the synthesis of epoxy resin shows the reactivity of modified lignin is enhanced, which can make modified lignin to be able to replace the toxic reagent, Bisphenol A.Second, the degradation of lignin was investigated. Ionic liquid [BMIm]Cl composited hydrochloric acid was employed to catalytically degradate lignin, analyses of the GCMS spectra of degradation products of lignin was conducted, the distribution rule of degradation products of lignin with the different solvent volume ration, reaction temperature and reaction time was obtained, the mechanism of the distribution of the degradation products of lignin influenced by the three factors solvent volume ration, reaction temperature and reaction time were discussed, and the optimum process conditions of lignin degradation was given. Adopting the single factor control variable method, the effect of solvent volume ration, reaction temperature and reaction time on the lignin degradation was discussed and it is found the influence order of three factors is reaction temperature> reaction time> solvent volume ratio, reaction temperature and reaction time should be controlled in 105-155 "C and 4-6h respectively and that ionic liquid [BMIm]Cl composited hydrochloric acid plays a synergistic effect role in lignin degradation.Third, the degradation mechanism of lignin was discussed. On the basis of experiments, the three representative degradation mechanism of lignin was discussed, a new kind of the degradation mechanism of lignin was put forward and the rationality of the new degradation mechanism of lignin was verified by analyzing the GCMS spectra of degradation products of lignin, which is of great significance to research the degradation mechanism of lignin.From three aspects of lignin modification, lignin degradation and the degradation mechanism of lignin, the system of ionic liquid [BMIm]Cl composited hydrochloric used to degradate lignin was studied, a chemical method of lignin modification was given, a route of lignin degradation was given and degradation mechanism of lignin was explored.