不同超声波处理方式对纤维素酸水解选择性的影响

Effect of different ultrasonic treatments on selective acid hydrolysis of cellulose

研究超声波预处理和协同酸水解共处理两种不同方式对纤维素酸水解选择性的影响,对提高微晶纤维素产品质量具有重要的意义.本文通过纤维质量分析仪、X射线衍射仪(XRD)、扫描电镜(SEM)、傅里叶红外光谱(FTIR)及其二阶导数的分峰拟合等表征手段对不同超声处理方式下水解纤维素的尺寸分布、微观形貌、聚合度、比表面积、结晶结构、化学结构及氢键类型等的变化进行了对比研究,探讨了不同超声波处理方式对纤维素酸水解选择性的作用效果.结果表明:超声辅助酸水解提高了纤维素酸水解对无定形区的选择性,保护了结晶区,水解纤维素结晶度显著增加;与纤维素分子内氢键相比,超声辅助酸水解对纤维素分子间氢键的断裂具有更好的选择性;另外,超声处理有利于降低水解纤维素的聚合度和平均长度,提高尺寸均一性和比表面积,而纤维素的化学结构和晶型不发生变化.

The different ultrasonic treatments including pretreatment and synergy with acid were not only influence the selective hydrolysis of cellulose,but also had important significance in improving the quality of microcrystalline cellulose product.The effect of selectivity of acid hydrolysis on cellulose under different ultrasonic treatment was discussed in this paper.Characterization methods such as fiber quality analyzer,X-ray diffraction（XRD）,scanning electron microscope（SEM）,fourier infrared spectrometer（FTIR）and peak fitting were used to analyze the size distribution,micro morphology,degree of polymerization,specific surface area,crystalline structure,chemical structure and types of hydrogen bond of hydrocellulose under different ultrasonic treatment.The results showed that it could improve the selectivity of amorphous region and protect the crystalline region of cellulose,as a result to improve the crystallinity of hydrocellulose under the synergistic effect of ultrasonic treatment,which also had better selectivity of rupturing the intermolecular hydrogen bond of cellulose.Moreover,not only lower degree of polymerization and average length,but also higher size uniformity and specific surface area of hydrocellulose were obtained by acid hydrolysis of cellulose under ultrasonic treatment without changing the chemical structure and crystal type of cellulose.