新型转极性离子化合物对香樟木屑的溶解和再生性能研究

摘要

为实现生物质的溶解,同时克服传统离子液体溶解生物质的缺点,制备了新型转极性离子化合物1,8-二氮杂二环十一碳-7-烯(DBU)/CH3OH/CO2(DCC)的甲醇溶液,考察了不同温度、时间和溶液浓度对香樟木屑的溶解性能和再生效果,分析了溶解前后香樟木屑中纤维素、半纤维素和木质素的溶解率及结晶度的变化,并对溶解前后的木屑进行FT-IR、XRD和SEM表征,对溶解液中再生的物质进行FT-IR和UV分析。结果表明：较高温度(≥120℃)下,香樟木屑在DCC的甲醇溶液中的溶解率随温度升高和时间延长而有所增加；DCC甲醇溶液对半纤维素和木质素的溶解能力较强,对纤维素的溶解能力较弱；2.5 mol/L的DCC甲醇溶液在溶解温度180℃,溶解时间6 h时,木屑溶解率达到48.6%,半纤维素溶解率达62.4%,木质素溶解率为55.7%,纤维素溶解率为19.6%,溶解效果与传统离子液体相当。 FT-IR、XRD和SEM分析表明,DCC甲醇溶液溶解木屑时,主要溶解木屑中无定形的半纤维素、木质素和少量非晶态的纤维素。 FT-IR和UV分析表明溶解液中再生的物质是木质素,其质量分数在90%以上。 DCC甲醇溶液重复使用3次时,每溶解一次其溶解能力下降2~3个百分点。%New switchable ionic solution, 1,8-diazabicyclo[5. 4. 0]undec-7-ene(DBU)/CH3OH/CO2(DCC), is superior to the traditional ionic liquids in dissolving biomass. In present study, methanol solution of DCC was used to dissolve the camphor sawdust. The effects of temperature,dissolving time and the concentration of DCC on the dissolution and regeneration of biomass were investigated. The solubility and crystalline of cellulose,hemicellulose and lignin in the materials were analyzed. FT-IR,XRD, SEM and UV were used to characterize the properties of the raw materials and the dissolved materials. The results showed that at higher temperatures(≥120 ℃) ,the dissolution of camphor wood sawdust in DCC methanol solution increased with the increase of temperature and time. The DCC methanol solution showed good dissolution ability for hemicellulose and lignin,while it was very poor for cellulose dissolution. The dissolution ratio of sawdust in 2. 5 mol/L DCC methanol solution was 48. 6% after 6 h at 180 ℃. At the same time, the detailed dissolution ratio of hemicellulose,lignin and cellulose were 62. 4%,55. 7% and 19. 6%, respectively. FT-IR,XRD and SEM analysis showed that dissolved composition was mainly composed by amorphous hemicellulose, lignin and small amounts of amorphous cellulose. FT-IR and UV analysis showed that lignin with mass fraction above 90% could be regenerated from methanol solution of DCC when water was added. The dissolution abitity of methanol solution of DCC reduced 2 3 percentage point each time as it was used repeatedly 3 times.