ZnO的均匀沉淀法制备及其在费托反应中的应用

发布时间：2018-06-10 16:19

本文选题：氧化锌 + 均匀沉淀法　；参考：《浙江工业大学》2015年硕士论文

【摘要】：费托合成(Fischer-Tropsch Synthesis)是将煤、天然气和生物质中得到的合成气转化为液体燃料及高附加值的化工原料的重要手段,对解决能源问题具有至关重要的作用。钴基催化剂活性和重质烃选择性高、稳定性好,水煤气变换活性低,是最有发展前景的费托合成催化剂。本文将均匀沉淀法制备的碱式碳酸锌经焙烧后形成的Zn O作为Co基催化剂的载体,重点考察了碱式碳酸锌的形成过程,以及均匀沉淀温度与反应溶液中乙醇含量对Co/ZnO催化剂的费托合成反应性能的影响,并添加Al助剂提高了催化剂的活性和稳定性。通过X射线衍射(XRD)、程序升温还原(TPR)、扫描电镜(SEM)等表征手段,得到了以下结果:(1)采用均匀沉淀法制备了碱式碳酸锌,随着沉淀过程中温度升高、尿素量增多、反应时间延长,Zn原子利用率均得到提升;反应初期产物中发现棒状ZnO晶体,但它在40 min后消失;反应40 min和1h生成产物中只检测到Zn4CO3(OH)6·H2O和Zn5(CO3)2(OH)6晶体,并存在着前者向后者转化的现象,焙烧后的ZnO保留了母体的多孔片组装的球形结构,且随着焙烧温度的增加,Zn O晶粒长大。(2)考察了不同均匀沉淀反应温度和均匀沉淀溶剂中乙醇含量对ZnO及Co/Zn O费托催化剂的影响,发现提高均匀沉淀温度,ZnO晶粒变小,组装的片层状六角花微粒长大,同时结构发生变化,使费托性能产生差异,90°C是最适宜的合成温度;增加乙醇含量使ZnO微粒由六角花型趋近于球形,组装微粒片层结构的ZnO晶粒先变小后变大,添加20%(体积分数)乙醇可以将Co/Zn O的反应活性提高22%。(3)制备的Co/ZnO催化剂主要由于反应过程中Co的烧结导致失活。添加助剂Al有效改善了催化的烧结现象,解决了费托反应失活问题,提高了催化剂的稳定性。Al含量为0.1%时,不仅明显改善催化剂的反应稳定性,还提高了催化剂的费托反应活性。
[Abstract]:Fischer-Tropsch Synthesis is an important method for converting syngas from coal, natural gas and biomass into liquid fuel and high value-added chemical raw materials, which plays an important role in solving energy problems. Cobalt based catalyst with high selectivity, good stability and low water gas shift activity is the most promising catalyst for Fischer synthesis. In this paper, the basic zinc carbonate prepared by homogeneous precipitation method was calcined to form Zno as the carrier of Co based catalyst, and the formation process of basic zinc carbonate was investigated. The effects of homogeneous precipitation temperature and ethanol content in the reaction solution on the performance of Fischer-Tropsch synthesis of Co / ZnO catalyst were investigated. The activity and stability of the catalyst were improved by adding Al promoter. By means of X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM), the following results were obtained: 1) basic zinc carbonate was prepared by homogeneous precipitation method. With the increase of temperature, the amount of urea increased. In the initial product of the reaction, the rod-like crystal was found in the initial product, but it disappeared after 40 min. In the reaction product of 40 min and 1 h, only Zn _ 4CO _ 3H _ 3O _ 2O and Zn _ 5o _ 3CO _ 3O _ 2O _ H _ (6) crystals were detected. The calcined ZnO retained the spherical structure of the porous lamellar assembly. With the increase of calcination temperature, the effects of different homogeneous precipitation reaction temperature and ethanol content in homogeneous precipitation solvent on ZnO and Co / Zn O Fischer catalyst were investigated. The optimum synthesis temperature is 90 掳C due to the growth of the assembled lamellar hexagonal particles and the change of the structure, and the increase of ethanol content makes the ZnO particles become spherical from hexagonal flowers. The ZnO grains of the assembled particle lamellar structure first become smaller and then bigger. Adding 20% ethanol can increase the reaction activity of Co / Zn O and increase the reaction activity of Co / Zn O.) the Co / ZnO catalyst is mainly deactivated due to Co sintering during the reaction. The addition of Al can effectively improve the sintering phenomenon of the catalyst, solve the deactivation problem of the Fischer reaction, and improve the stability of the catalyst when the content of Al is 0.1, which not only improves the stability of the catalyst, but also improves the stability of the catalyst. The catalytic activity of the catalyst was also improved.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ132.41;TQ529.2

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