Research On Separation And Conversion Of Pine Components In The Ionic Liquid System

The main ingredients in the plant consist of cellulose, lignin and hemicellulose. They areall rich renewable energy on earth. These three components are very complex structures in theplant skeleton, lignin is a kind of amorphous polymer macromolecules, which is connected byhydrogen bond with cellulose, and cellulose is a linear crystal type macromolecule, there are alarge number of hydrogen bonds among the molecules and in the molecules. Above all, thekey of this paper is to separate the main ingredients effectively. On the basis of the method ofconventional ethanol autocatalytic pulping, a new solvent system——ionic liquid aqueousethanol solution was construct in this thesis. Among them, the ionic liquid [Bmim]Br wasa new solvent,which can dissolve biomass completely. Then the natural pine wood was usedas raw material in this paper, the optimal separation conditions of lignin and cellulose inthe new solvent system were researched and controllable separation had been realized.Moreover, the separation of transformation products （cellulose and hemicellulose） and therecycling of ionic liquid were studied, the main experimental conclusions are as follows:1. In the study, the ionic liquid [Bmim]Br was synthetized by the raw material ofN-methylimidazole and1-butyl bromide. The results of the research are as follows: the ratioof N-methylimidazole to1-butyl bromide was1:1.1（n/n）, reaction temperature60℃,reaction time5hours, stirring speed110r/min, on the above conditions, the final ionic liquidwere of high purity and stable property, the thermal decomposition would notoccur in less than228℃.2. Moreover, in the paper, a new solvent system was used in the dissolution process ofpine wood powder, experiments showed that lignin and cellulose could be effectivelyseparated by the method. The optimal experimental conditions were as follows: the reactiontemperature170℃, reaction time120min, ratio of [Bmin] Br to C₂H₆O was3:7（v/v） andH₂O to [Bmin]Br （v/v） was in the range of20%-30%. On the above conditions, dissolutionrates of wood powder reached more than60%, at the same time, not only lignin could beseparated from the pine wood, but cellulose could be reserved to a greater degree. The purityof separated crude lignin and cellulose could respectively reach to more than89.6%and92.1%. Moreover, existence of the impurities had no effects on the dissolution of wood flour. 3. The final aqueous solution （ionic liquid recovered solution） was recycled after theprocess of wood powder separation. In addition to the main component [Bmin]Br, many othermonosaccharides products were contained in the recovered solution, such as glucose,etc.They were all derived from hemicellulose and some cellulose degradation products, so theyshould be separated from the system in order to ensure effective recycling and reuse of ionicliquid. Sugar components in the model solution were separated in this study by the method ofchromatography, and investigated the application of the common glucose, Results showed thatglucose could be converted into5-HMF by catalyst CrCl₃·6H₂O in IL, and a higher yield of5-HMF（27.78%） was obtained.