【作者】 文振中；

【导师】 涂善东；

【作者基本信息】 华东理工大学 ， 化工过程机械， 2010， 博士

【摘要】 随着化石能源的日益枯竭和环境问题的突显,寻求可再生能源作为补充越来越受到世界各国的重视。生物柴油作为一种可再生能源,具有来源广泛、对环境友好、可生物降解,以及能够与当前的柴油混合使用或直接使用而不需要对发动机做改进的诸多优点。目前大部分生物柴油都是在均相催化作用下通过间歇式搅拌反应器制备的。使用间歇式搅拌反应器不仅生产时间长,而且效率低,不能实现连续化生产。除此之外,使用均相催化剂会造成额外的环境问题,这与发展绿色能源的初衷相悖。除此之外,生物柴油的最终价格和其原料来源的关系极大。因此,寻求价格相对低廉的原料来发展生物柴油有利于降低成本。基于上述考虑,本文的主要研究内容与创新成果有以下几个方面：(1)微槽道反应器强化合成生物柴油的研究设计了应用于强化生物柴油合成的Zigzag型微槽道反应器,研究不同的微槽道尺度和形状对两相不相溶液体混合的影响,初步探讨了其强化传质的相关机理。微槽道当量直径的减小和流道弯曲数的增加将会形成更小的混合液滴粒径,从而使得生物柴油产率提高。与普通的间歇式搅拌反应器相比,Zigzag型微槽道反应器能够在28s的停留时间下达到99.5%的生物柴油产率,而间歇式搅拌反应器则需要1h以上。此外,研究了微槽道反应器和间歇式搅拌反应器之间的能耗比较,发现使用微槽道合成单位质量的生物柴油所需要的能耗约为间歇式搅拌反应器的1/3。这些结果表明Zigzag型微槽道反应器可作为小型紧凑分布式能源制备系统来发展。(2)泡沫金属反应器强化合成生物柴油的研究鉴于微槽道反应器的生产容量小的弱点,设计使用泡沫金属反应器作为强化传质工具来进行生物柴油的合成。研究了20PPI、30PPI和50PPI三种不同规格的泡沫金属反应器对甲醇/豆油两相不相溶液体之间的混合效果。实验结果表明使用50PPI的泡沫金属反应器得到最小的混合液滴粒径,从而得到最高的生物柴油产率。与间歇式搅拌反应器和微槽道反应器相比,50PPI的泡沫金属展现出更小的能耗,在生产单位质量生物柴油所需能耗仅为1.14 Jg-1,约为微槽道反应器的1.69%和间歇式搅拌反应器的0.77%。因此,泡沫金属反应器有望能够成为小型高效的生物柴油制备系统被广泛应用。(3) Li掺杂MgO固体催化剂合成生物柴油的研究使用浸渍法设计了应用于酯交换制备生物柴油的Li掺杂MgO系列固体碱催化剂,研究不同的制备条件如Li/Mg摩尔比和煅烧温度对催化剂性能的影响。研究发现,Li的掺杂造成了MgO晶格的畸变,从而使得该催化剂能够在较温和的条件下能够达到高的生物柴油产率,而MgO本身在温和条件下几乎为惰性。除此之外,研究了催化剂的反应工艺参数和可再利用性。实验结果表明该催化剂在甲醇中易流失活性组分,因此形成了部分均相催化行为,催化剂的稳定性需要做更多的改进以便应用于规模化的生物柴油生产。(4) CaO-CeO2混合氧化物催化转化黄连木油为生物柴油的研究设计了CaO-CeO2混合氧化物催化剂,应用于催化转化黄连木油为生物柴油。催化剂的活性和稳定性与Ce/Ca摩尔比以及煅烧温度密切相关。与纯CaO催化剂相比,Ce的加入显著地提高了催化剂的稳定性。催化剂的表征表明该类催化剂的良好的活性和稳定性源自于Ce取代CaO中的Ca离子,从而形成了晶格缺陷,这些缺陷对于非均相催化是有利的。该系列中的最佳催化剂在重复利用性能上也有着良好表现,重复使用四次之后,仍然能够达到80%以上的生物柴油产率,而当催化剂在清洗煅烧再生后再次使用时,生物柴油的产率达到了91.1%,接近催化剂初始使用的水平。(5) TiO2-MgO混合氧化物催化转化废弃煎炸油为生物柴油的研究使用价格低廉的废弃煎炸油作为原料,设计了非均相固体催化剂TiO2-MgO混合氧化物催化剂用于转换其为生物柴油,研究不同的Mg/Ti摩尔比以及煅烧温度对于催化剂性能的影响。当使用纯MgO作为催化剂时,金属离子的流失是很严重的,而通过Ti的加入,则显著地提高了催化剂的稳定性。当Mg/Ti的摩尔比为1,煅烧温度为923 K时,催化剂的活性和稳定性达到最佳。生物柴油的产率随着重复利用次数的增加而逐次降低,但是当催化剂经过煅烧再生后,生物柴油的产率却比第一次使用时高,主要是源自于其更高的比表面积、孔容以及平均孔径。这些结果表明TiO2-MgO混合氧化物催化剂作为规模化生产生物柴油时具有良好的前景。更多还原

【Abstract】 Due to the depletion of petroleum-based sources and environmental concern, alternative renewable energy sources have attracted more attention in many countries. Biodiesel is non-toxic, bio-degradable and can be used directly or blended with conventional diesel, without modification of current engine systems. Generally, biodiesel is produced by a batch stirred reactor via homogeneous catalysis, which needs a long time of reaction leading to low efficiency and batch production. Using homogeneous catalysts would bring new environmental issue, e.g. waste water that will not fit the philosophy of "Green energy" Besides, the feedstock of biodiesel plays an important role since the price of biodiesel is closely related to the feedstock. Therefore, seeking for low-price feedstock is significant for reducing the cost of biodiesel. production. Considering of these points, the main contents and novel results are as follows:(1) Intensification of biodiesel synthesis using zigzag micro-channel reactorsZigzag micro-channel reactors have been fabricated and used for continuous biodiesel production. The influences of main geometric parameters on the performance of the micro-channel reactors were experimentally studied. It has been found that the zigzag micro-channel reactor with small channel size and more turns produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared to conventional batch stirred reactor, the zigzag micro-channel reactor could get the biodiesel yield of 99.5% in residence time of 28 s. Besides, the energy consumption of micro-channel reactor was 1/3 of that originated by batch stirred reactor. These results indicate micro-channel reactors can be designed as compact mini-fuel processing plant for distributive applications.(2) Intensification of biodiesel synthesis using metal-foam reactorsAs the production volume of micro-channel reactor is low, it is necessary to design a new continuous reactor for synthesizing biodiesel. Here, the metal-foam reactor was firstly designed as a tool for continuous biodiesel production. Three types (20PPI,30PPI,50PPI) of metal foam reactors were evaluated according to the mixing result of methanol/oil. It has been found that the metal foam reactor with the higher pore density produces smaller droplets which result in higher efficiency of biodiesel synthesis. Compared with the batch stirred reactor and micro-channel reactor, the metal foam reactor (50PPI) exhibited lower energy consumption per gram biodiesel of 1.14 J g-1, only 1.69% and 0.77% those of micro-channel reactor and batch stirred reactor.(3) Synthesis of biodiesel catalyzed by Li-doped MgO catalystsThe Li-doped MgO catalysts were prepared by incipient wetness impregnation method and used for biodiesel synthesis. The Li/Mg molar ratios and calcination temperatures on the performance of catalysts were investigated. It has been found that the catalytic activity is improved by Li doping, which is attributed by the defects of MgO lattice. The active sites were leached into the reactants leading to the deactivation of catalysts, indicating more studies are needed to stabilize the catalysts for its large-scale application.(4) Transesterification of Pistacia chinensis oil for biodiesel catalyzed by CaO-CeO2 mixed oxidesCaO-CeO2 mixed oxides were prepared for producing biodiesel from Pistacia chinensis oil. The molar ratios of Ce/Ca and calcination temperatures of catalysts were optimized. It has been found the replacing of Ca2+ for Ce4+ would enhance the stability of catalyst due to the defects. After the fourth reuse, the biodiesel yield exceeded 80% yet. Interestingly, after calcination of the used catalyst, the biodiesel yield could still reached 91.1%, which is close to the level of fresh use.(5) Biodiesel production from waste cooking oil catalyzed by TiO2-MgO mixed oxidesMixed oxides of TiO2-MgO were used as solid catalysts to convert waste cooking oil into biodiesel. The preparation parameters such as Mg/Ti molar ratios and calcination temperatures were studied. The metal leaching was serious when using MgO as catalyst. However, the catalyst stability was improved by Ti addition. The optimal result was obtained as the Mg/Ti molar ratio of 1 and calcination temperature of 923 K. The biodiesel yield reduced as the reuse time increased. Nevertheless, the biodiesel yield could exceed the fresh use after regeneration, which might be attributed to its larger BET surface area, pore volume and average pore diameter. The mixed oxides catalyst, TiO2-MgO, showed good potential in large-scale biodiesel production from waste cooking oil.更多还原