【作者】 乔小青；

【导师】 马润宇；

【作者基本信息】 北京化工大学 ， 生物化工， 2009， 硕士

【摘要】 我国是农业大国,农作物秸秆年产量超过6亿吨,其中玉米秸秆占很大部分,但利用率较低,仅有少部分用作饲料或作为造纸和生产化工产品的原料,大量秸秆被用于薪柴或腐烂废弃,既浪费了资源,又污染了大气。玉米秸秆结构复杂,纤维素、半纤维素不但被木质素包裹,而且半纤维素部分共价和木质素结合,纤维素具有高度有序晶体结构,使得玉米秸秆难以利用。必须经过预处理,使得纤维素、半纤维素、木质素分离开,切断它们的氢键破坏晶体结构,降低聚合度。玉米秸秆中的半纤维素虽然相对于糠醛生产的传统原料玉米芯等含量较低,但是具有价格低廉,来源广泛等不可比拟的优点。随着玉米芯等传统原料的价格不断上涨,怎样环保有效的分离且利用玉米秸秆中的半纤维素成了一个需要解决的问题。针对目前糠醛生产中玉米芯原料有限,用酸量大及糠醛渣难以综合利用等问题,本文以玉米秸秆为原料,探索了汽爆水提液制备糠醛新工艺。首先,使用蒸汽爆破技术预处理玉米秸秆,使得其中大部分的半纤维素降解分离。汽爆完毕水提处理,以提取出汽爆过程中玉米秸秆中的半纤维素降解成的木糖,再利用水提液中的木糖在高温高压条件下进一步转化为糠醛,从汽爆条件的优化、水提条件优化、制备糠醛条件的优化以及反应中焦化的现象等方面进行了研究,为开发一种新的糠醛生产工艺奠定了基础。首先对汽爆条件和水提条件进行了考察。在汽爆压力1.4MPa下,维压时间4min,汽爆效果较好。这个条件下汽爆物料组织结构松散,且水提液中木糖的溶出率最高可达3.25%。玉米秸秆中的几种组份有较大变化,其中半纤维素有大幅下降,从最初的23.7%最多下降至5.55%。对水提条件也进行了考察,80℃热水水提,1:6的固液比下水提效果较好,水提时间对水提液中木糖浓度影响不大。考虑到下一步的利用,我们采用80℃热水水提,1:4的固液比下处理15分钟,水提液呈酸性,且含有大量糖分和酸类。考察了反应温度、盐酸浓度和反应时间对糠醛收率的影响并对焦化问题进行了分析。实验结果表明:汽爆玉米秸秆水提液制糠醛的最优条件是反应温度180℃,2%盐酸添加量,反应时间2h;进一步通过红外光谱分析了汽爆玉米秸秆水提液制糠醛过程中焦化现象产生的原因。本文的优势在于玉米秸秆原料价格低廉,来源广泛,糠醛收率高(76.6%),便于物料的综合利用。更多还原

【Abstract】 In China more than 6 billion tons of agricultural waste was generated every year. However, few of them was used as feed and raw material of paper and chemical industrial product while most of them was burnt. The structure of corn stalk was complex , cellulose and hemicellulose were bounding by lignin, hemicellulose covalent binding with lignin, cellulose has high orderd crystal structure, all of that made corn stalk hard to use.Some pre-treatment, for example steam-exploded, can be used to destroy the crystal structure of lingnocellulose, which makes the substrate easy to be divided and iridized. In this study,corn stalk was pretreatment by steam-explodsion to degraded most of hemicellulose. And then, water was used for extracting the generated xylose. In the conditions of high temperature and press, the xylose was converted to furfural.Some conditions such as explosion, water extraction and furfural production were optimized. The cocking during the process of furfural production was investigated. This study can be a basis of new process of furfural production.At first, some condition such as explosion, water extraction and furfural production were optimized. The results showed that the best condition was 1.4Mpa(press) and 4 min(maintaining time). In this condition, hemicellulose in corn stalk reduced from 23.7% to 5.55% and a water extraction was 80℃and 6 ml water per g substrate.Then, some factors such as temperature, Hcl concentration and reaction time of furfural production using the water extraction of steam-exploded stalk were investigated. The best condition was 180℃,2%Hcl, and 2h. The reasons of cocking during the process of furfural production were also investigated using infrared spectrum. The advantage of this process was low cost substrate and high yield(76.6%)更多还原