【作者】 庞春生；

【导师】 林鹿；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2012， 博士

【摘要】 随着工业的发展，人类对能源和材料的需求量日益增加，石油等矿物资源的消耗日趋加快，价格不断上涨，而且按目前的消耗速度，石油将在几十年后被基本耗尽。进入后石油时代，人类迫切需要替代能源和材料，世界各国也在制订相关政策和措施应对即将到来的无石油时代。届时，可再生的植物生物质资源无疑将成为人类唯一的有机碳源，那么如何清洁、有效的利用植物生物质生产人类所需的能源和材料在未来将成为评判国家竞争力大小的重要标准之一，也是国家能源安全的重要保证，本论文正是基于此思想开展了卓有成效的研究工作。此外，我国森林资源相对匮乏，以农业为主，每年产生大量的农业废弃物，有代表性的如玉米秸秆。本论文选取了玉米秸秆作为研究对象，目的是试图将尚未得到充分利用的玉米秸秆用于高附加值产品的生产，进而推动农业的发展，提高农民收入。本论文研究了一种新型的玉米秸秆蒸煮预处理工艺—固体碱活性氧蒸煮工艺。该蒸煮工艺能够有效脱除木素，用于植物生物质组分的分离。该蒸煮工艺中活性氧来自于O₂和H₂O₂，固体碱是MgO基的，是一种环境友好型的方法，生产过程使用了绿色的化学品，易于回收再利用，对环保具有重大意义。该蒸煮方法有别于传统的氧脱木素工艺，体现在新的蒸煮方法采用了难溶于水的固体碱替代传统氧脱木素使用的水溶性强碱，从而构建了一个新的氧脱木素介质体系。本论文研究了玉米秸秆固体碱活性氧蒸煮法的工艺条件，并得出较佳的蒸煮工艺条件为：蒸煮温度165℃，固体碱量15.4%，氧气初始压力1.0MPa，过氧化氢添加量3.0%，固液比为1:6，保温时间2h。在此蒸煮条件下，玉米秸秆的木素脱除率可达82.1%，浆得率为50.7%。研究结果表明，固体碱是本蒸煮工艺不可缺少的因素，它具有保护碳水化合物的功能，也有利于提高木素脱除率；氧气是脱木素的主要因素，而氧气和过氧化氢的联合蒸煮提高了木素脱除率。对玉米秸秆固体碱活性氧蒸煮后的浆料表面形貌和化学特性研究表明，玉米秸秆变成纤维化，浆表面的O/C值上升，XPS谱图中的C1下降，而C2、C3和C4含量均上升，表明浆料表面主要是纤维素和半纤维素，并有部分有机物被氧化。AFM研究则表明，蒸煮后的浆表面具有“点蚀”现象，而经碱法蒸煮所得浆的表面却呈现光滑现象，说明固体碱活性氧比碱法蒸煮更能有效脱除原料表面的抽出物和木素，对浆料表面的破坏比碱法的强。TEM的研究也表明，即固体碱活性氧蒸煮法的宏观作用机制是由表及里，蚕食并分离了纤维细胞的胞间层；碱法蒸煮则无法完全分离胞间层，而是采取渗透的方法脱木素。研究结果表明，固体碱对纤维素的保护功能来自Mg²⁺或含镁基团，而且必须在碱性条件下此保护功能才会启动。固体碱提高脱木素率的原因可能主要来自于其自身能提供电子对的缘故。对脱脂棉和微晶纤维素进行固体碱蒸煮的研究表明，固体碱能有效保护纤维素免于被碳化，但蒸煮后纤维素结晶结构发生变化，聚合度降低，尤其是低聚合度的微晶纤维素受影响更大。根据实验结果，本论文对Mg²⁺或含镁基团的纤维素保护功能在OH^-参与下的保护途径进行了讨论。固体碱活性氧蒸煮升温过程是大量脱木素阶段，脱木素率随着保温时间的增加而增加。固体碱活性氧蒸煮作用部位主要发生在胞间层，木素中的苯基是主要反应中心，蒸煮后木素的苯基被大量脱除，尤其是带有双键共轭结构的苯基。研究结果表明，固体碱活性氧蒸煮可以作为植物生物质精炼的预处理工序，它能有效的提高可酶解性，有利于后续的处理。更多还原

【Abstract】 With the development of society, oil is fast consumed due to the increased demand.Mankind is facing a difficult situation to look for a substitute for the future because the oilwill be used up for decades afterward according to the present rate of consumption. The plantbiomass will be the only carbon resources on the earth when the oil is used up in future,meaning that every country needs more investigation on the utilization of biomass, whichrelates to the development and safety of the country. The research in this dissertation wasperformed based on this situation and some meaningful results were obtained. In China, agreat amount of agricultural wastes was produced every year, especially for corn stalk.Therefore, corn stalk selected as a research object has the great significance for thesustainable development of agriculture.A novel method of cooking of corn stalk with active oxygen and a solid alkali wasstudied in this dissertation. Lignin can be removed by this method, and it can be used in theprocess of separation of lignocellulose. The active oxygen comes from O₂and H₂O₂, and thesolid alkali is MgO. This method is considered as a clean process for using the green chemicaland the solid alkali can be recycled. Otherwise, this method is different from the traditionaloxygen delignification, that is, a new medium system is built by the novel cooking methodthrough the substitute for the soluble alkali with the insoluble solid alkali.The process condition of the novel cooking was studied, and the optimum condition wasobtained: cooking temperature of165°C, solid alkali of15.4%, initial oxygen pressure of1.0MPa, H₂O₂of3.0%, solid-to-liquor ratio of1:6and keeping time of2h. Under the optimumcondition, the rate of delignification was82.1%, and the yield of pulp was50.7%. The resultsshowed that the solid alkali is an indispensable factor because it can protect the carbohydrateand increase the rate of delignification; the main factor of delignification was O₂, but thecombination of O₂and H₂O₂can obviously increase the rate of delignification.The results showed that the corn stalk became fibration after cooking and the ratio of O/Con the pulp surface increased. In the XPS after cooking, the intensity of C1decreased, but thatof C2, C3, C4increased showing that cellulose and hemicellulose are the main componentson the surface of pulp, and small amounts of carbohydrate are oxidized. In the pictures ofAFM, the pitting corrosion was observed on the surface of pulp cooked by active oxygen andthe solid alkali, but the surface of pulp cooked by alkaline cooking was glossy, meaning thatthe damage on the surface of pulp cooked by active oxygen and a solid alkali is more seriousthan that of alkaline cooking. TEM showed that the middle layer （ML） of fibrocyte was destroyed completely by active oxygen and the solid alkali cooking, but the alkaline cookingwas less efficient.The results showed that the protection of solid alkali resulted from Mg²⁺or its ionicgroup that must be put into the alkaline condition. The reason of the increase ofdelignification rate by solid alkali was possibly from its capacity that could provide duplet.The results from the cooking of absorbent cotton and microcrystalline cellulose showed thatthe solid alkali could protect cellulose from carbonization, but its crystal structure changedand the degree of polymerization （DP） decreased, especially for the low DP cellulose. Thepossible protective pathways of Mg were discussed in the dissertation.The results showed that a great amount of lignin was removed in the temperature riseperiod, and the rate of delignification increased with the increase of keeping time. The part ofdelignification was in the ML, and the reactive center was the benzene ring of lignin. Thebenzene ring of lignin was largely removed after the cooking with active oxygen and a solidalkali, especially for the benzene rings that contain conjugate double bond.The results indicate that the cooking with active oxygen and a solid alkali can be apretreatment of biorefinery because it can improve the rate of enzymolysis of cellulose.更多还原