| Fibrous cell wall structure of biomass was complex, with various types of chemical bonds and hydrogen bonds between components, resulting in difficulty separation. Currently conventional separation methods could only separate one or two of cellulose, hemicellulose and lignin, limiting its utilization in energy, chemicals, fine chemicals and so on. Therefore,seeking a green solvent to efficiently dissolve lignocellulose and a method for effective separation of components is particularly urgent. For the characteristic of ionic liquids’ structure can be designed, synthesized an ionic liquid with a strong coordination ability named 1,3-dimethyl-imidazole dimethyl phosphate salt [Mmim]DMP. Studied ionic liquids’ solubility of biomass, and found three components’ change rule in dissolution, to achieve its application in pulping and biomass.Firstly studied on the stability of [Mmim]DMP aqueous solution, and results showed that[Mmim]DMP aqueous solution was stable within 24 h after preparation. Ionic liquid concentration and absorbance had a good linear relationship at the maximum absorption wavelength 211 nm. Measured the standard curve equation was y=0.0194x+0.0107, the correlation coefficient R was 0.9991. Using this standard curve to assayed lab-made[Mmim]DMP samples’ purity and analyzed spiked recoveries. The results showed that UV spectrophotometry measured [Mmim]DMP’s purity quickly and accurately, and spiked recoveries of the method were 97% to 103%.By controlling three factors including ratio of reactants, reaction temperature and time,studied their effects on the ionic liquid yield. Optimized conditions of synthesizing[Mmim]DMP was a mole ratio(trimethyl phosphate:N-methylimidazole) of 1.2:1,temperature of 110 ℃, reaction time of 10 h. Under this condition the yield of ionic liquid could reach more than 97.5%.Secondly, used [Mmim]DMP to respectively have a general dissolution of Eucalyptus,Chinese silver grass and Bagasse. The results showed that: [Mmim]DMP’s solubilities of three materials were 6.34%, 9.24% and 19.36%. Infrared spectra and composition analysis of raw materials, residues and precipitates indicated that compared with Chinese silver grass and Bagasse, Eucalyptus’ s lignin was more soluble in the ionic liquid. The ionic liquid had aneffect of dissolving Eucalyptus’ s lignin similarly in microwave dissolution. Acid-insoluble lignin was converted to acid-soluble lignin, with partly lignin degradation or modification. So[Mmim]DMP can be used in pretreatment of Eucalyptus’ s pulping for lignin extraction.Used Eucalyptus chips as the raw material and [Mmim]DMP as the pretreatment agent of kraft pulping. By analyzing component quantity in the dissolution tests as choosing indicators of pretreatment conditions, obtained the condition of ionic liquid pretreated Eucalyptus was100 ℃, 10 min and 1:30. After cooking yield of pulp with pretreatment of the ionic liquid was44.92% and the blank sample’s yield was 40.88%. Potassium permanganate value of pulp with ionic liquid pretreatment was 12.97, while the blank’s was 14.62, indicating pulp with ionic liquid pretreatment had a lower lignin and higher cellulose content having a low stiffness and better performance. Beating Eucalyptus pulp by PFI grind, selected samples with five beating degrees to make papers and measured their properties. The results showed that pulp with ionic liquid pretreatment had a greatly improved property, including bursting,folding and tensile strength enhanced most obviously.By orthogonal design studied three factors melting temperature, time and solid-liquid ratio how to affect wood powder’s solubilites under microwave conditions, determining optimized condition was 170 ℃, 20 min and a solid-liquid ratio of 1:25. Sequence from the degree of influence was dissolution temperature, dissolving time and solid-liquid ratio. Solubility under this conditions was up to 94.91%.Finally, used three methods to separate components of Eucalyptus dissolving liquid. When the content of water in water separation method was less than 10%, the precipitated material was mainly cellulose with yield of 60%. When the water content was more than 16%,precipitate was mainly lignin with yield of 55%. By organic solvent separation method,selecting an organic solvent aqueous system with an acetone-water ratio of 1:1(V/V) was the most beneficial. Lignin yield was 26.6% and purity was 83.4%, while cellulose yield was70.1% and purity was 73.1%. Yield and purity of precipitated lignin from NaOH separation method were the highest, followed by hemicellulose, cellulose lowest. In NaOH alkaline separation process three components were degradative. |
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