25第五节 木素的物理性质及其利用

《25第五节 木素的物理性质及其利用》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、第五节木素的物理性质及其利用Section5PhysicalPropertiesandUtilizationofLigninPhysicalpropertiesofligninUtilizationofligninPhysicalpropertiesofligninPhysicalpropertiesofligninarevariableandcomplicatedformanyfactors.Physicalpropertiesoflignindependnotonlyontheorigin(kindsofplant),butalsoonthemetho

2、dsofligninseparation（一）Generalphysicalproperties1、ColorProtoligninisawhitematerialornearlyachromaticityThecolorofligninformedwhentheligninwasseparatedandprepared.Thedifferentofcolor(highorlow)isduetothedifferentmethodsofseparationandpreparationThelignincolourcanberemovedbychemical

3、methodandsoon.ColorofligninResiduallignininpulpandthatinblackliquorisdeeplybrownResiduallignininbleachedpulpisprimroseyellow(淡黄色)2、RelativedensityThevalueisdifferentbecauseofthedifferentdeterminationandpreparationmethodsMostoftheligninisolatedfromlignifiedplantisamorphouspowderand

4、itsrelativedensityisbetween1.3and1.5TherelativedensityofKlasonligninofpineis1.451determinedbywateranditis1.436determinedbybenzene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1.3613、OpticspropertyTheligninhasnotopticalactivitybecauseoftheshortageofsymmetrical(对称的)carbonatom4、Combus

5、tionvalueRelativelyhigh，forexample：ThecombustionvalueofhydrochloricacidligninofSprucewithoutashis110.0kJ/gThecombustionvalueofKalsonligninis109.6kJ/g5、SolubilityProtoligninusuallydoesnotdissolveinanysolvent6、ViscosityTheviscosityofligninsolutionislowanditisonlyone-forthofsynthetic

6、polymers（二）MolecularweightofligninandtheformofligninmoleculeRelativemolecularweight木素是一种高分子化合物，原本木素的分子量可高达几十万分离木素的分子量要低得多，一般仅有几千到几万磨木木素也只是原本木素中的低分子量部分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制浆过程中木素大分子降解溶出的模型AveragemolecularweightofMWLsampl

7、e重均分子量Mw数均分子量MnMw/MnSprucePineAspenReed705066505140535041203760344033001.711.771.491.62TheratioofMw/Mnreflectsthedistributionnatureofligninanditshowsthatthemolecularweighthascertainnonuniformity重均分子量与数均分子量之比，体现了木素的多分散性，说明木素分子量存在一定的不均一性。Becauseofthehighmolecularweightandtheabsenceo

8、fhydrophilicgroups;itleadstothelo