不同热预处理对栎木木质纤维素降解的影响

Effect of different heat pretreatment on lignocellulose degradation of oak

【目的】为破坏木质生物质天然抗降解屏障,促进木质生物质高效转化利用,筛选出适宜的热预处理方式。【方法】以栎木为研究对象,利用质量法/体积法、范式抽提法对高温蒸汽处理、固态汽爆处理和挤压膨化处理栎木的物理性质、木质纤维素含量进行测定,采用傅里叶变换红外光谱、X-射线衍射法对其木质官能团和纤维素相对结晶度进行分析。【结果】挤压膨化处理可显著改变栎木的形貌,持水力和比孔隙率分别为对照的3.2倍和4.71倍,容重降低至对照的1/4。各热预处理均可显著降低栎木木质纤维素含量,挤压膨化处理后木质纤维素含量显著下降,纤维素、半纤维素和木质素含量分别比对照组降低了22.60%、15.85%和7.9%。傅里叶变换红外光谱显示,各热预处理栎木均具有木质特征官能团,挤压膨化处理I_(898)/I_(1 509)比值显著增大,说明纤维素被富集。经不同热预处理后栎木仍具有典型的纤维素X-射线衍射特征,晶体结构峰形未发生改变,但强度不同程度变弱;相对结晶度不同程度增大,固态汽爆处理和挤压膨化处理后相对结晶度显著升高,表明结晶区的纤维素被更多地暴露出来。【结论】挤压膨化处理可显著改变栎木物理性质,降低木质纤维素含量,暴露结晶区纤维素,有利于木质生物质的高效转化利用。

【Objective】In order to destroy the natural anti-degradation barrier,promote efficient conversion efficiency and utilization of woody biomass,finally select a suitable heat pretreatment method.【Method】Taking oak as the research object,the physical properties and lignocellulose content of oak treated by high-temperature steam,solid-state steam explosion and extrusion were determined by mass method/volume method and Van Soest method,and its functional groups and relative crystallinity of cellulose were analyzed by Fourier transform infrared spectroscopy and X-ray diffraction.【Result】The extrusion treatment could significantly change the morphology of oak,the water-holding capacity and specific porosity were 3.2 times and 4.71 times higher than that of untreated wood,respectively,and the volumetric weight was reduced to 1/4 of untreated wood.All heat pretreatments significantly reduced the content of lignocellulose in oak.Lignocellulose content was significantly reduced after extrusion.The contents of cellulose,hemicellulose and lignin were reduced by 22.60%,15.85%and 7.9%respectively compared with control group.Fourier transform infrared spectroscopy(FT-IR)showed that all the heat pretreatment oak had wood characteristic functional groups,and the ratio of I898/I1509 increased significantly after extrusion,indicating that cellulose was enriched.After different heat pretreatments,the wood still had typical cellulose X-ray diffraction characteristics,and the peak shape of crystal structure did not changed,but the intensity was weakened.The relative crystallinity increased after different heat pretreatments,and the relative crystallinity increased significantly after solid-state steam explosion treatment and extrusion treatment,which indicated that the cellulose in the crystallization area was more exposed.【Conclusion】The extrusion treatment can significantly change the physical properties of oak,reduce the lignocellulose content and expose the cellulose in the crystallization zone,which is beneficial to the conversion efficiency and utilization of woody biomass.