杨木纤维组织的微爆处理及其对木素的增效溶出机制

In our previous study of “effect of pretreatment on pulping and enzymatic hydrolysis properties of Poplar”, the authors found that the high temperature and dipping effect of hot water extraction caused micro-structure expansion and deformation in wood chips during partly hemicellulose and lignin dissolving, so called “microexplosion effect”. Results showed that the microexplosion could enhance delignification process of pulping, increase enzymatic efficiency, reduce chemical dosage and improve bleachibility of pulp. However, the changes of lignocellulosic structure and strengthening Dissolved Mechanism of lignin effect was un-clear for the microexplosion and/or various intensity.The theory of lignocellulose microexplosion reaction was investigated in this proposal using cellulose, hemicellulose, lignin of Poplar and corresponding model as started materials. The properties of wood fiber components and product material were characterized by modern analysis technologies such as NMR, LCMS, HPLC, HPIC, CP-GC-MS, FTIR, et al. The reaction kinetic of various target materials at micro-explosion reaction was built. The correlation between micro-structure changes and lignin effect-strengthening dissolution mechanism was investigated, thus clarifying the mechanism of those reactions. The results of this study could build a novelty lignin Effect-Strengthening Dissolved technology for hardwood, while lowering chemical consumption in pulping and improving bleachibility. Finally, those achievements could benefit for the further exploration of more effective cleaning pulping and papermaking production technology.

本项目申请者研究预处理对杨木制浆性能与酶解效果的影响与提高时，发现把杨木片进行高温热水处理，木质纤维在溶出部分半纤维素和少量木素的同时，整个木片的微观组织结构产生了一定程度的膨胀变形，此现象可称之为微爆。微爆的产生能提高生物酶的可及度和作用效率，并能使制浆过程中木素增效溶出。但微爆对杨木制浆过程中木质纤维组织结构的改变及木质素增效溶出机理并不清楚。本项目拟以杨木纤维组分和模型物为研究对象，采用NMR、LCMS、HPLC、HPIC等现代分析手段对各目标物及反应产物进行表征分析，弄清各目标物在微爆时的反应动力学，探究微爆对杨木木质纤维微观组织的改变与木素增效溶出机制的关联作用，阐明其对木素的增效溶出机理，研究结果可构建一种新型阔叶材木素增效溶出处理技术，减少制浆过程化学试剂用量，提高酶对纸浆的作用效率，为制浆造纸工业实现清洁生产提供理论指导，丰富预处理技术克服木质纤维素结构顽抗性的理论体系。

本项目探究微爆对杨木木质纤维微观组织的改变与木素增效溶出机制的关联作用，在高温水热预处理过程中以综合强度因子（CSF）作为宏观变量来研究不同CSF下原料微爆现象的产生、各组分的降解规律，并以此为基础确定微爆与各组分降解溶出的构效关系及对后续化学浆性能的影响。. 利用综合强度因子（CSF）作为高温水热预处理的严重程度来平衡纤维素的酶糖化和木质素结构性质。并通过FTIR，TGA，31 P- NMR和2D HSQC NMR表征提取的木质素。得出：最佳CSF为8.37，半纤维素脱除率达到74.71%，预水解液中葡萄糖浓度为1.19 g/L。随后将预处理底物酶水解，酶糖化产率为83.92%。木质素结构性能优异，如高羟基含量（2.34 mmol/g的脂肪族羟基和2.43 mmol/g的酚羟基）和27.86%的β-O-4芳基醚键。.在高温水热预处理过程中微爆程度与宏观变量CSF间存在构效关系。杨木经高温水热预处理，随CSF的变化，杨木微观结构形态也随之变化，即产生微爆现象。我们以微爆系数ŋ来衡量微爆程度大小。研究发现，随着CSF逐渐增大，微爆系数ŋ存在明显的变化规律：ŋ≤0，ŋ从0逐渐增大至最大值，ŋ达到最大值后又逐渐降低，据此我们将微爆程度划分为三个等级：轻微微爆、严重微爆和抑制微爆，并将ŋ=0定义为微爆临界点。经验证，微爆临界点在CSF为5.32～5.81之间较小的范围内。当ŋ≤0时，经高温水热预处理的杨木原料处于轻微微爆等级，此状态下杨木各组分脱除量较低，预水解液中各成分含量基本为零；当ŋ超过0至最大值期间即在微爆严重级时，杨木三大组分的脱除率、纤维素结晶度、预水解液中的五种单糖以及乙酸浓度等均出现显著变化，杨木各组分进入大量降解阶段。当在微爆抑制级时，微爆系数降低，木质素及其衍生物的再沉积、纤维塌陷等因素对微爆产生负作用，各组分的溶出呈缓慢增长或下降趋势。.本项目的研究结果可构建新型阔叶材木素增效溶出处理技术，减少制浆过程化学试剂用量，提高酶对纸浆的作用效率，为制浆造纸工业实现清洁生产提供理论指导，丰富预处理技术克服木质纤维素结构顽抗性的理论体系。