稀硫酸预处理对毛竹竹黄木质素结构的影响

以毛竹竹黄为原料,研究其木质素在稀酸预处理过程中的结构变化。依据Bj？rkman的方法分离纯化得到竹黄和稀酸预处理竹黄的磨木木质素,采用红外光谱(FT-IR)和核磁共振定量13C谱对两个木质素样品结构进行分析。FT-IR和定量13C谱图表明:在酸性条件下,竹黄木质素紫丁香基单元中醚化的联接键发生断裂,S/G比值由1.3降低为1.1。木质素在稀硫酸预处理过程中发生缩合反应,主要发生在愈创木基单元上。木质素芳环上C―O键含量由196.1/100C9降低为187.7/100C9,C―H键含量由219.4/100C9降低为205.7/100C9, C―C键含量由179.6/100C9提高为190.3/100C9,缩合度由31.4%提高为35.2%。
The effect of dilute acid pretreatment on the lignin structure of Moso bamboo inner skin was investigated. The bamboo inner skin ball-milled lignins(MWLs)were isolated before and after dilute sulfuric acid pretreatment, according to the isolation method developed by Bj？rkman. The structures of the MWLs were characterized by fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance(NMR). The 13C-NMR spectra showed that the etherified linkages in syringyl units were depolymerized during the acid pretreatment. After pretreatment, the S/G ratio of lignin was reduced from 1.3 to 1.1. Meanwhile, some lignins were condensed during the acid pretreatment, inducing the condensation degree increased from 31.4% to 35.2%. The amount of C―O and C―H linkages in the lignin were reduced from 196.1/100C9 and 219.4/100C9 to 187.7/100C9 and 205.7/100C9, respectively. While, the C―C linkages in the lignin were increased from 179.6/100C9 to 190.3/100C9