木聚糖对生物质组分水热碳化特性的影响研究

摘要

为了研究木聚糖的水热碳化特性,在间歇式反应釜中,进行反应温度为160 ～ 240℃、停留时间为120 min条件下的水热碳化实验研究,同时在220℃、120 min的反应条件下,考察了木聚糖对纤维素和木质素水热碳化过程的影响.研究发现,200℃时,木聚糖水热焦开始出现,随反应温度的升高,木聚糖水热焦产率逐渐增加,至240℃时,产率达13％;以小麦秸秆中半纤维素与纤维素和木质素混合水热碳化,木聚糖对纤维素水热焦产率影响不大,而碳质量分数从纯纤维素水热焦的42％增加至纤维素和木聚糖混合物水热焦的48％,与纯木质素水热焦相比,木聚糖和木质素混合物水热焦产率减少了23个百分点,碳质量分数变化不大;木聚糖水热焦中特征官能团随温度升高而减少,而C=C、C=O和芳香特征峰红外吸收逐渐增强,同时热重分析表明木聚糖水热焦热稳定性较好.傅里叶红外光谱、X射线衍射分析及热重分析表明,在水热碳化过程中,木聚糖可以促进纤维素和木质素分子结构的断裂、聚合和芳香化反应,提高水热焦的芳香特性.%Hemicellulose,cellulose and lignin are the main components of biomass.Different structures and components of the three components may have important effects on the product properties and reaction process of biomass hydrothermal carbonization.However,in the past few years,there were limited reports on HTC of xylose and its effect on the structure changes of cellulose and lignin during HTC.In order to study the hydrothermal carbonation characteristics of xylan,hydrothermal carbonation experiment was carried out in the batch reactor at 160 ～240℃ for 120 min.The effects of xylan on the hydrothermal process of cellulose and lignin were investigated at 220℃ for 120 min.It was found that the xylan hydrochar appearred at 200℃,and its yield was gradually increased with the increase of reaction temperature.When the temperature reached 240℃,the yield reached 13％.Xylose was also mixed with cellulose and lignin respectively according to the proportion of three components in wheat straw,and the mixture was hydrothermally treated at the temperature of 220℃ for 120 min.The results showed that xylan had little effect on the yield of cellulose hydrochar,while the carbon mass fraction was increased from 42％ of the cellulose hydrochar to 48％ of the cellulose and xylose hydrochar.The yield of xylan and lignin hyrchar was decreased by 23 percentage points and the carbon mass fraction changed little compared with those of lignin hydrochar.The functional groups were decreased with the increase of temperature,while the C =C,C =O and aromatic peaks were gradually enhanced,and the thermogravimetric analysis presented a good thermal stability of xylan.Fourier transform infrared spectroscopy,X-ray diffraction analysis and thermogravimetric analysis showed that xylan can promote the fracture,polymerization and aromatization of the molecular structures for cellulose and lignin during hydrothermal carbonization,and improve the aromatic properties of hydrochars.