Study Of Lignin Extraction Using Ionic Liquids

With oil, natural gas and other non-renewable resources being consumed, the developmentand utilization of biomass was widely concerned. As a large agricultural country, there areabundant straw and other agricultural waste in china, but most of them were burned, whichcause a serious problem of wasteing resources and environmental pollution. Lignin, as animportant component of straw, is the third largest resources of natural polymer. An efficientmethod of extraction and application of lignin, which is an important direction ofdevelopment of lignocellulosic, should be established with good social and economicbenefits.In this paper, a new method of biomass components separation, which based on dealingwith straw by a green solvent-imidazole ionic liquid/water system, was proposed. The mainprocess include: aiming at weight loss and the composition of the residuals after treated,effects of temperature, duration, pressure, ionic liquid/water ratio and type of ionic liquid(anion: Cl-,Br-and cation: C2~C10) on the treating process of legume straw (40~60mesh)were investigated to determine the optimum process parameters.. The samples obtained in thisprocess were charateritized by Fourier transform infrared spectroscopy (FT-IR), nuclearmagnetic resonance (NMR), thermogravimetric analysis (TGA), X-ray diffraction (XRD),scanning electron microscopy SEM, etc. The results show that there no great influence ofduration (0~4h) on the process; with increasing temperature from50oC to150oC, the weightloss of legume straw increases; with increasing temperature from150oC to170oC, itdecreases slightly; with the increase of pressure (up to1MPa), the weight loss increases, butits composition keep constant; effects of cations and anions of ionic liquids on theexperimental results are similar; influence of the mass ratio ionic liquid/water on the processwas obvious; the suitable amount of water not only favors increasing the weight loss oflegume straw, but also significantly changes the composition of the residuals. Moreover, theresults show that the obtained lignin keeps the original structure and purity perfectly. Underexperimental results and economic considerations, the optimal treatment conditions are asfollows: temperature is150℃; duration is2h; mass ratio of [C4mim]Cl/water is3:2, mass ratio of liquor to solid is20:1. The extraction yield is up to24.3%, and the holocellulose is upto75.6%. Dissolved lignin accounted for48.2%of the total amount of straw lignin, therecovery is32.4%. The method of dealing with legume straw in ionic liquid/water system isthe highlight in this paper. Furthermore, a new components separation technique oflignocellulosic biomass was proposed. The addition of water decreases the cost of ionicliquids and improves practical application. This work will favor establishing a new andefficient biomass conversion technology.