25第五节 木素物理性质与其利用课件.pptVIP

第五节 木素的物理性质及其利用Section 5 Physical Properties and Utilization of Lignin; Physical properties of lignin;（一）General physical properties;2、Relative density The value is different because of the different determination and preparation methods Most of the lignin isolated from lignified plant is amorphous powder and its relative density is between 1.3 and 1.5 The relative density of Klason lignin of pine is 1.451 determined by water and it is 1.436 determined by benzene 云杉二氧六环木素用水测定的是1.330，用二氧六环测定的是1.391，用比重计法测定的则是1.361 ;3、Optics property The lignin has not optical activity because of the shortage of symmetrical(对称的) carbon atom 4、Combustion value Relatively high，for example： The combustion value of hydrochloric acid lignin of Spruce without ash is 110.0kJ/g The combustion value of Kalson lignin is 109.6kJ/g 5、Solubility Protolignin usually does not dissolve in any solvent 6、Viscosity The viscosity of lignin solution is low and it is only one-forth of synthetic polymers;（二）Molecular weight of lignin and the form of lignin molecule;X-射线衍射图表明，木素的结构是无定型的，分离出的木素大都是无定型的粉末。 用电子显微镜研究木素的超分子结构状态表明，木素是： 以球状质点状态或 块状质点状态聚集存在的 ; Average molecular weight of MWL;Because of the high molecular weight and the absence of hydrophilic groups; it leads to the low solubility of proto lignin in water or usual solvents, even insolubilization. The isolated lignin has certain solubility, but it is variable according to plant species, separation method and solvent Whether it can dissolve in certain solvent lies on the isolated lignin properties , the solubility parameters of solvents and the binding energy of hydrogen bond. Brauns lignin and organic solvent lignin can dissolve in dioxane（二氧六环）、pyridine、methanol、ethanol、acetone and diluted alkaline solution, but some water must be added. Otherwise, they are nearly insoluble. ;Basis of lignin release during pulping;（四）Thermal property of lignin;Utilization of lignin;1 Utilization of lignin degraded products;甲硫醇;2 Utilization of lig