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题名	高选择性制备汽柴油的钴基费托合成催化剂的研究
作者	吴黎阳
学位类别	博士
答辩日期	2015-05
授予单位	中国科学院大学
授予地点	北京
导师	张东柯 ; 吴晋沪
关键词	费托合成 钴基催化剂 ZSM-5/SBA-15复合载体 SiC载体 汽柴油馏分
学位专业	化学工程
中文摘要	Fischer-Tropsch合成(F-T合成)技术是将煤、天然气、生物质等含碳资源转化为无硫、无氮和低芳烃的优质液体燃料的重要途径。目前，国内外的合成油工艺一般需要经过重质烃，然后加氢精制获得柴油，路线较长且能耗、水耗极高，这是由F-T反应特点所决定的：产物碳数分布遵循Anderson-Schultz-Flory（ASF）分布。如何最大限度的抑制甲烷及轻质烷烃的生成和提高中间馏分油（汽油和柴油馏分）的比例，是改进费托合成技术的重要方向之一，也是F-T合成研究中最有挑战性的科学技术与问题。在F-T合成催化剂中Co基催化剂以其高活性、高稳定性、高重质烃选择性及低水煤气变换等特点被认为是最佳的合成中间馏分油的F-T合成催化剂。 本论文以钴基催化剂为研究对象，分别考察了SBA-15、ZSM-5、SiC、无定形SiO2等载体的性质，添加Zr、Ca、Mn等助剂以及制备方法对催化剂结构、表面物理化学性质及费托合成产物分布的影响。主要研究内容包括以下几个方面： 以P123为模板剂，合成了具有六方孔道结构的SBA-15介孔分子筛，随后采用等体积浸渍法在SBA-15上负载钴作为费托合成催化剂。考察了孔径大小对费托合成反应性能的影响，结果发现，随着SBA-15载体孔径和孔容的增大，催化剂中的Co3O4颗粒也随之增大，钴和载体之间的相互作用减弱，还原度提高，使得CO的转化率提高，汽柴油馏分选择性增加。 采用共浸渍法、分步浸渍法和原位合成法引入Zr助剂，制备了系列Co/Zr/SBA-15费托合成催化剂。其中，共浸渍法制备的催化剂钴锆作用较强，钴颗粒较小，还原度低；而分步浸渍法制备的催化剂孔径较大，钴颗粒较大，钴锆相互作用较弱，还原度较高。对原位合成法制备的Co/ZrSBA-15催化剂，考察了反应工艺条件对其催化性能的影响。结果表明，CO转化率随着温度的提高而增大；随着压力增大气态烃选择性降低，重质烃选择性增加；CO转化率和C5+选择性随着空速的增加而降低。 通过对比分子筛加入方式以及分子筛种类（ZSM-5、USY和H-β）对制备的复合载体负载的Co基催化剂的催化性能的影响，确定了以SBA-15和ZSM-5复合作载体然后浸渍Co来制备费托合成催化剂的制备方法。该方法制备的催化剂钴颗粒大小适中，与载体相互作用适中并具有一定的酸性，具有最佳的汽柴油馏分选择性。随后，考察了ZSM-5在复合载体中的含量对催化剂的结构、表面物理化学性质和产物分布的影响，发现ZSM-5含量为20%时催化剂的孔容最大，钴颗粒分散度最高，同时催化剂适中的还原度和酸性使得产物中汽柴油馏分的选择性最高。对该催化剂进行的600 h连续性实验表明，该催化剂经过50 h的诱导期后，CO转化率和C5+选择性保持稳定，且随着反应的进行产物中正构烷烃的比例逐渐增大。 通过对比SiC、无定形SiO2和SBA-15分子筛负载的Co基催化剂F-T合成产物分布，发现SiC负载的Co基催化剂在高温时具有较高的催化活性且产物分布向长链烃方向偏移，柴油馏分选择性较高。加入1%的Zr，Ca或Mn助剂时，助剂与钴和载体间形成难还原的物种，导致催化剂的还原度降低，反应活性变差，且产物主要为气态烃类。适当增加Zr或Mn助剂含量为5%时，催化剂氢气吸附量增大，还原度提高，酸性增强，C5+选择性提高，其中加入5%Zr助剂的催化剂具有最高的汽柴油馏分选择性。
英文摘要	Fischer-Tropsch (F-T) synthesis F-T synthesisis an important means to convert coal, natural gas, biomass and other carbonaceous resources into high quality liquid hydrocarbon fuels free of sulfur and nitrogen and low in aromatics. At present, however, the F-T synthesis generally produces excess amount of heavy hydrocarbons, which have to go through further hydro-processing and refining to produce middle distillates such as gasoline and diesel required by the market. The over process is therefore long and complex with high energy (and water) consumption. This is determined by the F-T synthesis characteristics. A such key feature is that the carbon number distribution of the product follows the Anderson-Schultz-Flory (ASF) distribution. How to suppress the formation of methane and light hydrocarbons and increase the proportion of middle distillates (gasoline and diesel fractions) is not only one of the most important direction to improve the F-T synthesis technology, but also the most difficult challenges in the F-T synthesis research. In the F-T synthesis Co-based catalyst is considered to be the best for middle distillate synthesis due to its high activity, high stability, high selectivity towards high alkanes, with low water-gas shift reaction propensity. This PhD thesis details a systematic investigation into the cobalt-based F-T synthesis catalysts with an overall aim to develop highly selective catalysts for gasoline and diesel production. The focuses were placed on the influences of support properties, promoters and preparation methods on the structure, surface physical and chemical properties of the catalyst and product distribution were investigated. The main bodies of the work included the following aspects: SBA-15 with mesoporous hexagonal pore structure was synthesized using P123 as the structure-directing template. Cobalt based Fischer-Tropsch synthesis catalysts were prepared using the impregnation method with SBA-15 as the support. The effect of pore size of SBA-15 on the performance of Fischer-Tropsch synthesis was studied. It was found that increasing pore diameter and pore volume of the SBA-15 support, the Co3O4 particle size also increased, the interaction between cobalt and the support was weakened and thus the degree of reduction of cobalt increased, resulting in increased CO conversion and selectivity to the gasoline and diesel fractions. A series of Co/Zr/SBA-15 catalysts for Fischer-Tropsch synthesis were prepared using the co-impregnation method, stepwise impregnation method and in-situ synthesis method to incorporate Zr as a promoter. Among them, the interaction between cobalt and zirconium was stronger on the catalysts prepared by co-impregnation method, where the cobalt particles were small and the degree of reduction was low. Conversely, larger pores, the larger particles of cobalt, weaker interaction between cobalt and zirconium were observed on the catalysts prepared by stepwise impregnation method. For the Co/ZrSBA-15 catalysts synthesized in-situ, the effect of reaction conditions on the catalytic performance was investigated. The results showed that the CO conversion increased with increasing temperature, the selectivity towards the gaseous hydrocarbons decreased while the selectivity to heavier hydrocarbons increased with increasing pressure, CO conversion and the C5+ selectivity decreased with increasing space velocity. The effect of addition of several molecular sieves including ZSM-5, USY and H-β, and how they were added, on the catalytic performance of the so-called composite supported Co-based catalysts was also studied and compared. The results showed that the SBA-15 and ZSM-5 composite as a support to impregnate Co was a good way to prepare F-T synthesis catalysts. The catalysts prepared by this method showed a moderate size of cobalt particles, favourable cobalt-support interaction and moderate acidity, leading to the best gasoline and diesel distillate selectivity. The influence of the amount of ZSM-5 addition in the composite support on the structure, surface physicochemical properties of the catalyst and the product distribution was subsequently studied. It was found that the maximum pore volume, degree of cobalt particle dispersion, and the moderate reduction of the catalyst and acidity were shown to make the product selectivity of gasoline and diesel fractions the highest on the catalyst with 20% ZSM-5. A 600hr continuous experimental run showed that for this catalyst, the CO conversion and C5+ selectivity remained stable after a 50hr induction period, and the ratio of n-alkanes in the product was gradually increased. The F-T synthesis product distribution over the SiC, amorphous SiO2 and SBA-15 molecular sieve supported Co-based catalysts was found to be contravertial. The SiC supported catalysts had high catalytic activity and the product distribution was shifted to long-chain hydrocarbons at high temperatures, while the diesel distillate selectivity was higher. When adding 1% Zr, Ca or Mn as modifiers, respectively, species, such as CO(OH)O and MnxCo3-xO4, which are difficult to reduce, were formed among promoter, cobalt and support. These led to a decreased degree of the catalyst reductions. The reactivity also deteriorated with gaseous hydrocarbons becoming the dominant product. When the Zr or Mn promoter was appropriately increased to, say, 5%, the hydrogen adsorption capacity, acidity and reduction degree of the catalysts all increased, while the C5+ selectivity was enhanced too. The catalyst with 5% Zr added was shown to possess the highest selectivity toward gasoline and diesel fraction.
语种	中文
学科主题	工学
公开日期	2020-09-30
内容类型	学位论文
源URL	[http://ir.qibebt.ac.cn/handle/337004/8082]
专题	青岛生物能源与过程研究所_热化学转化事业部
作者单位	1.中国科学院青岛生物能源与过程研究所 2.中国科学院大学
推荐引用方式 GB/T 7714	吴黎阳. 高选择性制备汽柴油的钴基费托合成催化剂的研究[D]. 北京. 中国科学院大学. 2015.

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