【作者】 李兵；

【导师】 康勇；

【作者基本信息】 天津大学 ， 化工过程机械， 2012， 硕士

【摘要】 利用木质纤维素生产纤维素燃料乙醇，是当前世界生物能源产业的主流技术路线，但天然木质纤维原料具有抵抗微生物和酶降解的特性，所以必须开发有效的预处理技术来克服这一障碍，促进纤维质燃料乙醇经济高效转化。综合氨循环渗透法（ARP）和氨纤维爆破法（AFEX）的优点，本文提出了氨水循环爆破（RAAE）法，利用氨水替代液氨，在流化状态下生物质原料与氨水充分接触、增强传热和传质效果，有利于消除局部过热，减少抑制物的形成；加速木质素的溶解和从物料表面的去除。论文系统研究了预处理温度、预处理时间、含湿量、氨流速和流化时间对预处理后物料组份和酶解率的影响，并通过SEM、XRD和FTIR来探究预处理过程中的物理和化学变化。随预处理温度升高和时间的延长，纤维素和半纤维的回收率降低，但超过91.48%的纤维素和82.58%的半纤维素被保留，木质素去除率不断增加，18.66%-46.23%的木质素被去除；随预处理温度升高，葡聚糖和木聚糖酶解率逐渐增加，在85℃时，均达到最大分别为87.1%和84.1%，总糖转化率为77.31%；随预处理时间的延长，葡聚糖和木聚糖酶解率不断增加，但从25到35min过程中，增加趋势变缓，总糖转化率仅从72.68%增加到75.17%。因此确定最优预处理温度和时间水平分别为85℃和25min。含湿量对各组份的影响很小，超过96.36%的纤维素和近90%以上的半纤维素得到很好的保留；当含湿量为60%时葡聚糖酶解率最大为79.89%，随含湿量增加木聚糖酶解率和总糖得率总体上呈下降趋势，综合考虑葡聚糖酶解率和总糖得率确定含湿量最优水平为60%。随氨流速增加，木质素去除率从23.01%增加到38.86%；葡聚糖酶解率逐渐增加，当氨流速超过3L/min时，葡聚糖酶解率仅从87.68%增加到88.15%，而且此时木聚糖酶解率和总糖得率均达到最大值分别为91.03%和75.05%，综合考虑确定最优氨流速为3L/min.随流化时间的延长，木质素去除率不断增加，最大值为39.86%；纤维素相对含量从42.69%增加到45.67%；葡聚糖酶解率不断增加，但是当流化时间超过9min时，增加趋势变缓，此时总糖得率达到最大值80.14%，因此确定流化时间最优水平为9min.SEM表明预处理有效地打断了高粱秸秆的交联结构，使更多的纤维暴露出来，增加了纤维素与酶的接触面积；XRD分析表明随预处理温度和时间增加，秸秆的结晶度指数增加，主要是由于去除了较多的无定形组织（木质素和半纤维素）；FTIR表明预处理过程中分子结构的改变。木质素的去除率与葡聚糖和木聚糖酶解率呈正线性相关，当添加浓度为0.05g/g底质的PEG6000,对葡聚糖酶解率促进作用最大。更多还原

【Abstract】 Currently, cellulosic ethanol production from the abundant and renewablelignocellulosic biomass is a leading and dominant technology route in globalbioenergy industry. However, the plant cell walls naturally resist decompositionmicrobes and enzymes, so the breakthrough technologies have to be developed toovercome barriers, which can implement economical feasibility and efficiency ofbioconversion. Based on combination of advantages of the ammonia recycledpercolation (ARP) and the ammonia fiber explosion (AFEX), a new pretreatmentmethod named the reflowed aqua ammonia explosion (RAAE) pretreatment wasdeveloped. The sorghum stalk in circulated and fluidized state could adequatelycontact with aqueous ammonia, which enhanced the effect of mass and heat transfer,so as to eliminated local overheating of reaction and reduced the formation ofinhibitory compounds. In this circulated flowthrough system, lignin was dissolved andswept from the pretreated samples. The pretreatment effect was influenced by somerelated factors such as temperature, pretreatment time, moisture, the ammonia flowrate and time. A series of experiments were carried out to explore how these factorsaffect the composition and enzymatic digestibility of treated samples. The treatedsamples were then further examined and analyzed by SEM, X-Ray crystallography,and FTIR to explore changes of physical characteristics and chemical composition inpretreatment.With the increasing of temperature and pretreatment time, although the recoveryof glucan and xylan decreased, more than91.48%glucan and82.58%xylan based onthe raw sample were preserved, and the amount of lignin removal gradually increasedfrom18.66%to46.23%. The enzymatic digestibility of glucan and xylan bothincreased with temperature increasing. The maximum enzymatic digestibility ofglucan and xylan were respectively for87.1and84.1%, and the total sugar yield was77.31%, all of which were achieved at temperature of85℃. With pretreatment timeincreasing, the glucan enzymatic digestibility steadily increased. However, whenpretreatment time exceeded25min, the glucan enzymatic digestibility increased moreslowly, and the total sugar yield only increased from72.68%to75.17%whenpretreatment time increased from25min to35min. So the optimum pretreatment temperature and time were selected as85℃and25min, respectively.With moisture content increasing, the composition of the pretreated sorghumstalk was almost unchanged, and the recovery of glucan and xylan were more than96.36%and90%respectively. The maximum glucan enzymatic digestibility was79.46%at moisture content of60%, while the enzymatic digestibility of xylan and thetotal sugar yield decreased with the increase of moisture. Synthetically consideringthe glucan enzymatic digestibility and total sugar yield, the optimal moisture contentcondition was selected as60%.With flow rate increasing, the amount of lignin removal increased from23.01%to38.86%, and the glucan enzymatic digestibility also increased gradually, but thistrend slowed down when the flow rate increased over3L/min. The maximum xylanenzymatic digestibility and total sugar yield were respectively for91.03%and75.05%at flow rate of3L/min. So the optimal flow rate was selected as3L/min.With flow time increasing, the lignin removal increased, and the maximum valuewas39.86%. Meanwhile, the cellulose content increased from42.69%to45.67%, andthe enzymatic digestibility of glucan also increased. However, when flow time wasexceeded9min, the glucan enzymatic digestibility increased more slowly. Themaximum total sugar yield was80.14%, achieved at flow time of9min.The SEM analysis indicated that the rigid biomass structure was deformed andmore cellulosic fibers were exposed after pretreatment. The crystallinity indexincreased with pretreatment temperature and time increasing, because part of theamorphous portion (lignin and hemicellulose) of biomass was removed. Chemicalchange was further confirmed by FTIR analysis.A positive linear correlation was observed between lignin removal andglucan/xylan enzymatic digestibility. When PEG6000with concentration of0.05g/gsubstrate was added in enzymatic hydrolysis, the glucan enzymatic digestibility wassignificantly improved.更多还原