甲酸分离甘蔗渣组分的过程控制及机理研究

As an abundant, cheap and renewable resource in Guangxi provice, sugarcane bagasse is mainly used for pulping and papermaking. Amounts of hemicellulose and a great deal of lignin were let out with the waste water during the traditional pulping processes, which brings about the resource waste and environmental pollution. In order to comprehensive utilize each component of suggarcane bagasse, organic acid pretreatment coupled with membrane separation maybe helpful to obtain the easy enzymatic hydrolysised cellulose and lignin byproducts with high purity. This work intend to use formic acid for lignocellulose fractional pretreatment. Binding with the inner/outer diffusion and the inhibition of the dissolved lignin on the delignification, it is feasible to build formic acid delignification and xylan degradation kinetic models which more in line with the actual process. Analysis of formic acid delignification mechanism can be performed based on the kinetic model, the chemical and physical structure of other lignin products andmodel compounds of the formic acid pretreatment. Research on the change of chemical and physical structure of the raw materials during the formic acid pretreatment process and their impact on the performance of cellulase will also be carried out by the chemical structure analysis and the enzymatic performance testing of the obtained cellulose solid. That can reveal the impact of the formation and delivery mechanism of the proton in formic acid pretreatment process to the generated process inhibitors such as furfural enzymatic. Meanwhile, This work can provide an effective separation process of the pretreated bagasse components and theoretical guidance for the design of clean and cheap process of lignin separation.

甘蔗渣作为一种丰富的可再生资源，目前其主要用于制浆造纸，但制浆过程木素及半纤维素水解后随废水排放，造成了环境污染和资源浪费。以综合利用甘蔗渣各组分为目的，采用有机酸预处理与膜分离藕合的方法可获得易于酶解的纤维素及高纯度的木素产品。本项目拟采用甲酸水溶液对木质纤维素进行分级预处理，考虑内、外扩散的影响及溶解了的木素对脱木素过程的抑制作用，建立更符合实际过程的甲酸脱木素和木聚糖降解动力学模型；并根据动力学模型、甲酸预处理木素模型化合物及木素产品的化学与物理结构分析研究甲酸脱木素机理；对所获得的纤维素固体进行化学结构分析和酶解性能测试，研究甲酸预处理过程中原料的化学和物理结构变化及其对纤维素酶解性能的影响；揭示甲酸预处理过程中质子的形成及传递机制对生成糠醛等酶解过程抑制物的影响；同时构建预处理后甘蔗渣各组分的有效分离工艺，为开发清洁廉价的木质纤维素组分分离提供理论指导和实践基础。

本研究从原料组分分离和综合利用的角度出发，以甲酸预处理甘蔗渣为例，研究甲酸预处理木质纤维素的反应机理，考察甲酸浓度，反应时间等因素对甲酸预处理过程的影响。通过X射线衍射、红外光谱和扫描电镜等方法研究了甘蔗渣在酸脱木素过程中的化学组成和物理结构变化及其对纤维素酶解性能的影响，结果表明，基于甲酸脱木素的预处理工艺可以实现甘蔗渣中纤维素和木素的有效分离，所获得的纤维素固体酶解性能良好，酶解性能提高的原因是由于木素和半纤维素的脱除致使纤维素纤维得以解离和分散，从而显著提高了比表面积和纤维素的可及度，相对而言，提高纤维素酶解性能的更有效方法是去除木素。在动力学方程中引入了甲酸浓度、已脱除木素和聚糖水解程度等因素，以更为准确地描述甘蔗渣的脱木素和聚糖水解动力学行为。