离子液体预处理对桉木热解半焦结构和反应性的影响

Effect of ionic liquid pretreatment on eucalyptus char structure and its reactivity

生物质是可再生能源的理想原料,由于生物质有坚硬的木质素外壳保护而难以被有效利用。离子液体(IL)是一种绿色溶剂,可用于木质纤维素预处理从而提高其利用的效率。为了研究IL水溶液预处理对桉木热解产半焦的结构及其反应性的影响,将桉木粉经2%、4%和8%(质量)离子液体([Bmim]Cl、[Bmim]OAc和[Bmim]H_(2)PO_(4))水溶液在120℃下预处理2 h,然后将预处理后的桉木粉在650℃下热解。采用SEM、FTIR、XRD和Raman分析表征热解半焦的结构变化,利用热重分析仪(TGA)测定半焦与空气在450℃下的反应性。结果表明,随着预处理IL浓度的增加,半焦产率下降,半焦的晶化程度提高,在拉曼光谱中,ID1/IG变小,IG/Iall变大,这表明IL预处理使半焦结构有序增大,并促进半焦中小芳香环向大芳香环聚并,因而降低了半焦的反应性。IL预处理可便捷调节热解半焦的反应性,为生物质的高值化利用提供有效的制备方法。

Biomass is an ideal raw material for renewable energy,and it is difficult to use effectively because of its hard lignin shell protection.Ionic liquid(IL)was a green solvent which could be used in pretreating and improving the use efficiency of the biomass.To investigate the effects of IL on the pyrolytic char structure and its reactivity,eucalyptus powder was pyrolyzed in quartz reactor under 650℃.After being pretreated by IL([Bmim]Cl,[Bmim]OAc and[Bmim]H_(2)PO_(4))with a concentration of 2%,4%,8%at 120℃for 2 h,the structure of char obtained was characterized by SEM,FTIR,XRD and Raman spectrum.The reactivity of char with air at 450℃was also evaluated with thermal gravimetric analysis(TGA).The results showed that the yield of the char decreased with the increasing of the IL concentration,while the crystallinity was enhanced.The decrease in I_(D1)/I_(G) and an increase of I_(G)/I_(all)in Raman spectrum indicated an improvement in the order of the char structure,and the promotion of the transformation of small aromatic ring system into the large one,which led to a decrease reactivity of the biochar.IL pretreatment can adjust the reactivity of the pyrolytic biochar conveniently,and can provide effective way in using biomass with high value added.