【作者】 麻越佳；

【导师】 王子忱；

【作者基本信息】 吉林大学 ， 物理化学， 2011， 博士

【摘要】 20世纪以来,现代工业和交通运输等行业的迅速发展,导致了全球性能源、粮食和环境危机的日趋严重,这使得人类在迈入21世纪后面临着前所未有的挑战。世界许多国家为了应对化石资源的日益枯竭和环境的逐渐恶化,将目光逐渐转移到了大规模开发利用作为清洁能源的可再生资源。第一代燃料乙醇主要以玉米、小麦等粮食作物作为生产原料,日趋严峻的世界粮食安全形势让其渐失优势。而以非粮作物乙醇、纤维素乙醇和生物柴油等为代表的第二代生物燃料,遵循“不与粮争地、不与人争食”的路线,成为未来生物质能源产业发展的方向。纤维素乙醇被认为是最好的替代液体燃料,它的生态效益,使得它成为工业生物技术研究的重点中心,取得的研究和工业性试验结果给人类发展纤维素乙醇带来了希望。但是,纤维素的水解效率问题、水解废渣污染环境问题、水解糖液中有害物质影响酵母菌活性的问题、生产过程的能耗问题……,这一系列问题,导致纤维素乙醇生产成本过高,无法实现工业化生产,致使纤维素乙醇的研究与产业化开发的努力处于低潮状态。针对生物质乙醇目前存在的诸多问题,本论文企图找到生产生物质乙醇的新途径。采用稀酸水解半纤维素制备木糖和废渣(Ⅰ),解决了木糖影响酵母菌活性问题；采用常压低温液相浓酸水解废渣(Ⅰ)中纤维素制备糖酸溶液和废渣(Ⅱ),解决了纤维素的水解效率问题；碱溶稻壳灰中二氧化硅制备硅酸钠溶液和废渣(Ⅲ),硅酸钠溶液用于中和糖酸溶液,使水解糖液处理后可以直接用于发酵制备乙醇,同时制备出纳米二氧化硅,解决中和酸所带来的成本问题；废渣(Ⅱ)和(Ⅲ)热解制备出纳米二氧化硅,使最后的废渣得到充分利用,从而获得了一套完整的绿色环保低碳的稻壳制备燃料乙醇及综合利用的新工艺。主要内容如下：1.首先以生物质稻壳为原料,通过预处理及浓硫酸水解纤维素方法的系统研究得到葡萄糖溶液。预处理的最佳条件是：稀硫酸的浓度为6%(m/m),稀硫酸溶液与稻壳的液固比(v/m)为10∶1,在沸腾状态连续水解5小时,半纤维素得率达到18.6%(m半纤维素/m稻壳)。纤维素的最佳水解条件为：硫酸浓度为72%(m/m),温度为50℃,硫酸溶液的体积(毫升)与稻壳的质量(克)的比例为10∶1,时间为5分钟,葡萄糖产率可以达到45.6%(m纤维素/m稀酸水解后稻壳)。2.为了获得发酵用糖溶液,论文采用离子排斥色谱法和中和法对糖酸分离效果进行了研究。离子排斥色谱法适宜的操作条件如下：离子交换柱中填充的树脂选用强酸性阳离子树脂,颗粒直径为0.1-0.2 mm,树脂柱高度为1 m；进料和洗脱时流速为10 mL/min,使葡萄糖和硫酸得到一定程度的分离,反应温度为80℃时,葡萄糖回收率为96%,硫酸回收率为65%。中和法中用到的碱性溶液为硅酸钠溶液,制作方法如下：氢氧化钠溶液浓度为10%(m/m),氢氧化钠溶液与稻壳灰的液固比(v/m)为5∶1,加热至沸腾后持续2小时,二氧化硅水解率为64%。将糖酸溶液以1 mL/min的流速滴加入碱性溶液中,试验中碱性溶液与糖酸溶液的用量为2∶1(v/v),葡萄糖回收率为95%。两种方法得到的葡萄糖溶液的浓度经紫外分光(紫外可见)光度计测量可达0.1 g/mL3.对糖酸分离过程中得到的二氧化硅、木质素和硫酸钠晶体分别进行了研究。对纳米级二氧化硅主要考察了其粒径、形貌及分散性。在最佳水解条件下,残渣热解制备出的二氧化硅粉体粒径约为100 nm,球形,单分散；而中和后形成的二氧化硅粉体粒径约为30 nm,球形,分散性更好。硫酸水解纤维素过程中析出少量酸溶性木质素,通过酚化反应改性后,酚羟基的数量得到增加,使木质素有更多的活性点与苯酚反应。当木质素和苯酚质量比为1∶6、硫酸与水体积比为9∶6、反应温度80℃、反应时间达到4 h时,木质素酚的产量可达104%(m木质素酚/m苯酚)。用其制得的酚醛树脂在耐红外、耐紫外、疏水防潮、耐热等性能方面表现良好。硫酸钠作为中和试验中的副产物,主要考察了其晶体形态与形成过程的关系。4.将纤维素水解得到的葡萄糖溶液进行发酵制得乙醇溶液。试验中选择了市售安琪酵母作为发酵菌,考察了葡萄糖溶液浓度、酵母浓度、反应时间和温度对乙醇产率的影响,最佳反应条件为葡萄糖的浓度为10%(m/v),m葡萄糖∶m酵母=10∶1,选择体系pH=6.8,反应温度为34℃,反应时间为60 h,此时可以得到乙醇产率最高为67.0%(m乙醇∶m葡萄糖)。5.论文对稻壳综合利用的方案进行了归纳总结,并推广此方案应用于米糠综合利用,并与稻壳试验进行了系统对比,证明了此方法可在相似生物质中进行推广应用。更多还原

【Abstract】 Since the 20th century, the rapid development of modern industry and transp ortation industry, driving global energy, food and growing environmental crisis, which makes human beings in the 21st century faces unprecedented challenges. Facing the increasing depletion of conventional fossil energy and the rapid deterioration of the environment, many countries shift their focus on large-scale development and utilization of clean energy as a renewable resource. The first generation of fuel ethanol primarily produced from corn, wheat and other grain crops as raw material, gradually loses its advantage by a tightening situation of world food security. The second generation of biofuel, such as the non-grain ethanol, cellulosic ethanol and biodiesel, becomes the direction of biomass energy industry development in the future, as it follows the line of "not fight for ground with food, not fight for food with people".Cellulosic ethanol is considered to be the best alternative liquid fuel, and becomes the focus of industrial biotechnology research by its ecological benefits. At the present stage, the results of research and industrial test bring human beings the hope of developping cellulosic ethanol. However, a series of problems, such as the efficiency of cellulose hydrolysis, hydrolysis waste pollution, harmful substances affecting the activity of yeast in hydrolysis liquid, energy consumption of the production process......., lead to the high cost of cellulosic ethanol production, troubles in industrial production, and result in a low state of cellulosic ethanol research and industrial development.In this paper, I attempt to find a new way to product biomass ethanol to solve existing problems. The method of preparing xylose and residues (Ⅰ) by hydrolyzing hemicellulose solves the problem of the yeast activity affected by xylose. The way to obtain glucose and residue (Ⅱ) by hydrolyzing from residues (Ⅰ) with concentrated acid under normal pressure and low temperature, can inprove the efficiency of cellulose hydrolysis. Silica from rice hull ash can be dissolved in alkali liquid to preparate sodium silicate solution and residue (Ⅲ), which is used in neutralizing sugar and acid solution. The neutralization can solve the cost problem by producing glucose solution, which can be directly fermented to ethanol, and collecting nano-silica. Incineration of residue (Ⅱ) and (Ⅲ) to preparate nano-silica, can make the final residue being fully utilized. In this way, we obtain a new comprehensive, low-carbon and green technology of preparating fuel ethanol and utilizing rice hulls.The major elements are as follows:Firstly, I obtained glucose solution from the agricultural waste rice hull, through a pretreatment of dilute sulphuric acid and the hydrolysis of concentrated sulphuric acid. The suitable condition of the pretreatment is in the boiling solution with 6% dilute sulphuric acid for 5 h, and the ratio of H2SO4 solution volume (mL) to the rice hull mass (g) is 10:1, hemicellulose hydrolysis rate is 18.6%(mhemicellulose/mrice hull) The optimum hydrolysis conditions are as follows:the concentration of H2SO4 is 72% (wt.%), the temperature is 50℃, the ratio of H2SO4 solution volume(mL) to the rice hull mass(g) is 10:1 and the time is 5 minutes, the glucose yield rate reaches 45.6% (mcellulose/mrice hull afer pretreatment)Secondly, I studied the influence on the separation of the solution with the sugar and acid through the ion exclusion chromatography and neutralization. The ion exclusion chromatography is represented as a small pilot phase of separation of sugar and acid experimental methods. The suitable operating conditions are as follows:the resin used in the column is cation ion-exchange resin, with particle diameter 0.1-0.2 mm, and the resin column height of 1 m. When the feeding and elution flow speed are both 10 mL/min, the glucose rate is 96% and the sulphuric acid rate is 65% at 80℃. In neutralization, the alkaline solution is sodium silicate solution, and the methods are as follows:the concentration of sodium hydroxide solution was 15%(wt.%), and the liquid (sodium hydroxide solution) to solid (rice hull ash) ratio (v/m) was 5:1, the boiling time is 2 hours, the silica rate is 64%. The acid solution is dropped into the flask which contained alkaline solution with a speed of 1 mL/min, the ratio of the amount of alkaline solution to sugar and acid solution is approximately 2:1 (v/v), and the glucose rate is 95%. The concentration of glucose solution from these two methods are measured by ultraviolet spectrophotometer (UV-VIS) could be up to 0.1 g/mL.Thirdly, I studied silica, lignin and sodium sulfate crystals from the hydrolysis of concentrated sulphuric acid and the separation of the sugar and acid separately. This experimental is mainly designed to study the size, shape and dispersion of the nano-silica. With the optimum acid hydrolysis conditions, the silica particle incinerated from hydrolyzed residue is spherical, monodisperse with the size about 100nm; while, after neutralization the silica particle is with the size about 30nm, spherical, and better dispersion. There is a small amount of acid soluble lignin precipitated from the sulphuric acid hydrolysis process of cellulose. The increase of phenolic hydroxyl number after phenolation of rice hull acid-insoluble lignin proved more active site of lignin to react with phenol. When the weight rate of lignin and phenol is 1:6, the volume rate of H2SO4 and water is 9:6, reaction temperature is 80, and reaction time is 4 hours, the highest yield of lignin/phenol is 104%(m lignin/phenol /m pheno).The phenolic resin obtained by modified lignin performed well in the infrared, ultraviolet-resistant, hydrophobic moisture, heat and other properties. The by-product sodium sulfate is test the relationship of the crystal morphology and the formation.Fourthly, the glucose solution hydrolyzed from cellulose is eventually fermented to be ethanol. The fermentation bacteria selected in this experiment is Angel Yeast, which is a kind of commercial yeast. The optimal situations are as follows:the concentration of glucose solution is 10%, m glucose:m yeast=10:1, pH=6.8, reaction time is 60 h, and temperature is 34℃, the ethanol rate is 67.0%(m ethanol= m glucose)Finally, I summarize a method to comprehensively utilize rcie hull. The systematic comparison of rice hulls and rice bran proved that this method can be carried out in a similar application of biomass.更多还原