【作者】 宋华民；

【导师】 张百良；

【作者基本信息】 河南农业大学 ， 农业生物环境与能源工程， 2008， 博士

【摘要】 当前,国际原油价格持续上涨,燃油供应紧张,对我国经济建设产生较大影响,因此,液体代用燃料的研究得到广泛开展。生物柴油是以天然植物、动物油脂和短链醇进行酯交换反应得到的环境友好的替代液体燃料,其成分是多种脂肪酸甲酯的混合物,具有可再生、可替代、无毒、可生物降解等优点。许多研究表明,生物柴油的特性非常接近柴油燃料,因此,柴油机无需或稍作改进,就可以直接使用生物柴油作为燃料。固体酸（碱）指能够化学吸附碱（酸）的固体,定义为能够给出（接受）质子或接受（给出）电子对的固体,采用固体酸碱催化酯交换反应可以有效避免传统均相酸碱催化酯交换工艺中存在的产品分离困难和废催化剂的二次污染问题,研究非均相固体碱催化剂、酯交换反应过程对生物柴油的生产技术进步和应用推广,尤其是对正在兴起的中国生物柴油产业具有重要的意义。固体碱非均相催化生产生物柴油是一种新型的生产工艺,国内未发现规模化生产的报道。本课题首先从制备高活性、高选择性的固体碱催化剂出发,然后分析该催化剂中毒、失活的原因,从而探索提高固体碱稳定性、增加固体碱重复使用次数的新途径。本文对固体碱Cs2O/γ-Al2O3催化剂制备、使用及失活和重复使用性能进行了较深入的研究,并取得了阶段性的结论和成果。主要包括以下几个方面:1.本文对四种铯的化合物（Cs2CO3, CsC2H3O2, CsNO3和CsCl）负载制备固体碱催化剂进行了研究,考察了不同载体对催化剂性能的影响,发现以Cs2CO3、CsC2H3O2作为催化剂前躯体,以γ-Al2O3和CaO、MgO作为载体,均能制备出固体超强碱。通过试验研究,选取Cs2CO3作为前躯体,γ-Al2O3作为载体制备固体催化剂最合适。该催化剂制备方法简单,碱强度大。使用水做浸渍溶剂,在N₂气氛下煅烧获得Cs₂O/γ-Al₂O₃催化剂,其碱强度Hammett值大于37,采用相同方法,比使用K、Na、Ca元素制备的催化剂碱强度高。2.采用比表面积、X射线衍射、X射线荧光和红外吸收光谱等对Cs₂O/γ-Al₂O₃催化剂进行表征,证明在反应中起着重要作用的催化活性物质是负载在载体上的Cs2O,所制备的固体碱存在三个碱性中心。3.使用负载量为2.5mmol/g的Cs₂O/γ- Al₂O₃固体碱催化剂催化菜籽油与甲醇进行酯交换反应,最高酯交换率为95.5%;催化牛油与甲醇进行酯交换反应,最高酯交换率为93.7%;使用纳米γ-Al₂O₃作载体时,负载量可以达到4 mmol/g,在催化菜籽油与甲醇进行酯交换反应时,可以减少甲醇的使用量,缩短反应时间,酯交换率达到98.5%以上,80%以上的转化率可以重复使用10次以上。4.对催化剂中毒、失活的原因进行了试验研究,提出在氮气条件下重新煅烧是恢复中毒催化剂活性的有效方法;补充催化剂的活性组分是使失活催化剂恢复活性的有效方法。更多还原

【Abstract】 Currently, the research on alternative liquid fuel has been carried out extensively as a result of rising price of international crude oil and tension of oil supply, which will bring great effects on our country’s economy construction.Biodiesel, a mixture of methyl esters of fatty acids, is an environment-friendly transportation fuel produced by transesterification reaction of vegetable oils or animal fat with a short-chain alcohol in the presence of catalyst. Biodiesel is a renewable, alternative, non-toxic and biodegradable diesel fuel. Many studies have shown that the properties of biodiesel are very close to diesel fuel. Therefore, biodiesel can be used in diesel engines with little or no modification.Solid acid （base） refers to solids that can adsorb base （acid）, or be defined as solids that give （accept） proton or accept （give） electron. The transesterification reactions catalyzed by solid base may avoid the problems in traditional homogeneous acid/base catalyzing process that the separation of transesterification products with used catalyst is very difficult and discharge of waste catalyst induces environmental problems, it is meaningful for both the production and application of biodiesel, especially for the rising biodiesel industry to study heterogeneous base catalysts and transesterification process.Biodiesel production using heterogeneous base catalyst is a new process, which is little reported home and abroad. The purpose of this paper is to prepare highly-activated and highly-selective solid alkali catalyst and explore new methods of increasing stability and reusable times of solid base by analyzing the reason for which catalysts lost activity and got toxic.The preparation, application and reutilization of Cs2O/γ-Al2O3 catalyst were investigated in this paper. The main results are as follows:1. The preparation of solid base catalysts with four kinds of compounds based on cesium of Cs₂CO₃, CsC₂H₃O₂, CsNO₃ and CsCl and the effects of different kinds of supports on performance of catalysts were studied. The results show that solid super-base catalysts can be prepared with Cs₂CO₃ or CsC₂H₃O₂ loading onγ-Al₂O₃, CaO and MgO. It is the most suitable for preparation of catalysts to select Cs2CO3 as precursor andγ-Al₂O₃ as support due to simplicity of preparation technology and high base strength. Cs₂O/γ-Al₂O₃ catalyst, prepared by immersing Cs₂CO₃ into water, then loading onγ-Al₂O₃, finally calcining in nitrogen atmosphere, whose Hammett value is more than 37, which is higher than those of catalysts prepared with potassium, sodium and calcium under the same conditions.2. Cs2O/γ-Al2O3 catalyst was characterized by BET, XRD, XRF and FTIR. The results suggest that significant catalytic activity substance is Cs₂O dispersing over the support and prepared solid base has three alkali centers.3.The highest transesterification rate of 95.5% was obtained in ester-exchange reactions of rapeseed oil and methanol catalyzed by Cs₂O/γ- Al₂O₃ solid base whose loading amount was 2.5mmol/g, and the transesterification rate amounted to 93.7% in catalyzing ester-exchange reactions of tallow and methanol with the catalyst. The loading amount of 4 mmol/g could be achieved when using nano-γ-Al2O3 as support and the less methanol dosage, the shorter reaction time and 98.5% transesterification rate could be obtained in catalyzing ester-exchange reactions of rapeseed oil and methanol, and the transesterification rate was over 80% when this catalyst was used more than ten times.4. The reasons for toxicosis and loss of activity of catalyst were investigated. It’s suggested that the effective detoxifcation method is to calcine toxic catalyst again in nitrogen atmosphere and the method of resuming activity of catalyst is to supply activated components.更多还原