【作者】 丁兰；

【导师】 王旭珍；

【作者基本信息】 大连理工大学 ， 物理化学， 2010， 硕士

【摘要】 我国是以煤炭为主要能源的国家,整体煤气化联合发电(IGCC)技术由于高效率、低污染等特点成为当前最有前景的洁净燃煤发电技术之一,其中煤气脱硫净化是关键环节。煤气中的有机硫(主要是羰基硫,COS)脱除相对比较困难。加氢转化法脱除有机硫精度高、操作简单,设备投资低,而且可以直接利用煤气中的H2而无需外加气源,是加氢脱除煤气中COS的有效手段,开发高效加氢脱硫催化剂一直是本领域的研究热点。近年来,纳米科技的发展为催化剂的研究带来了新的机遇,纳米材料的优异催化性能受纳米晶的暴露晶面、形状、表面缺陷等参数的影响。因此,本论文将通过形貌控制合成,制备具有不同形貌、特定晶面的纳米材料,用作COS加氢脱除的非负载催化剂,探讨其对反应性能的影响。主要研究内容如下：(1)纳米氧化铈的控制合成及脱除COS性能采用水热合成法,通过调控反应参数,制备得到不同形貌的Ce02纳米多面体和一维纳米棒,与商业级Ce02对比,考察了它们在强还原气氛中对COS的加氢转化与脱除效果。结果表明,二者均优于商业级Ce02,Ce02纳米多面体颗粒比纳米棒可保持长时间的高活性及稳定性,分析了Ce02在不同温度下对COS的脱除机理。(2)纳米氧化钴的控制合成及脱除COS性能乙二醇法合成了不同形貌的Co3O4纳米棒和纳米多面体,在相同的预硫化和加氢脱硫反应条件下,一维纳米棒的活性显著优于纳米多面体。通过TEM、BET、XRF、H2-TPR等表征手段分析表明,二者主要暴露晶面不同：棒状Co3O4主要暴露晶面为活泼的(110)面,而多面体Co3O4为稳定的(111)晶面；影响催化活性的主要因素是催化剂的晶面效应,Co3O4纳米棒更容易被H2S气体预硫化,所形成的金属-硫键较活泼,容易形成硫空位,从而获得较高的加氢脱硫活性。此外,鉴于Pd基催化剂优异的加氢性能,进一步研究了负载型Pd基催化剂对COS的加氢脱除性能。分别以上述制备的纳米Ce02和不同种类的炭质材料为载体,采用超声辅助浸渍法制备了负载型Pd基催化剂,发现载体是影响催化效果的主要因素之一。相对于非负载Ce02,Pd／Ce02催化剂对COS的催化活性有所提高；以椰壳炭(AC)、超高比表活性炭(SAC)和碳纳米管(CNTs)为载体制备的催化剂,在相同反应条件下,对COS的加氢脱除性能依次为：Pd／CNTs＞Pd／SAC＞Pd／AC,Pd／CNTs表现出显著的高脱硫活性和稳定性。更多还原

【Abstract】 Coal is the main source of energy in our country. Due to high efficiency and low pollution, Integrated Gasification Combined Power Generation (IGCC) technology has become the one of the most promising clean coal power generation technology, in which gas desulfurization is the key point. The organic sulfur gas (mainly carbonyl sulfide, COS) removal is relatively difficult. Because of high precision removal of gaseous organic sulfur, simple operation, low investment in equipment, and the H2 source in coal gas can be used directly without the additional gas source, hydrodesulphurization (HDS) is the effective means for COS removal. The exploitation of high efficiency catalysts for the HDS of COS becomes an interesting task.In recent years, the development of nano-technology has brought new opportunities for catalyst research, and the excellent catalytic properties of nanometer materials is effected by parameters such as nanocrystalline exposed, shape and the surface defects. Based on the background of the subject, the main aim of our work is focused on the shape-control synthesis of nanocrystals and their properties as unsupported catalysts for COS hydrogenation. The contents are as follows:(1) Shape-control synthesis of cerium oxide nanocrystals and its performance for COS removal. CeO2 nanocrystals with different shape of nanopolyhedra and one dimensional nanorods have been obtained through hydrothermal route by controlling the reaction parameters. Compared with commercial grade CeO2, the COS conversion over the as-prepared products in strong reduction atmosphere is investigated. Results show that CeO2 nanopolyhedra can keep higher activity and stability for a long time than CeO2 nanorods and commercial CeO2. The COS removal mechanism of CeO2 nanopolyhedra under different temperatures has been discussed.(2) Shape-control synthesis of cobalt oxide nanocrystals and its performance for COS removal. CO3O4 nanocrystals, i.e. nanorods and nanopolyhedra, have been synthesized by a facile ethylene glycol route. After in situ presulfidation, the HDS activity of COS is conducted on these unsupported catalysts with unchanged morphology. Under the same reaction condition, the catalytic activity of the nanorods is more than four times of the nanopolyhedra at low temperature of 200℃. By the help of TEM、BET、XRF、H2-TPR technologies, it is found that the catalytic properties of the as-made nanocrystals are dependent on the nature of their surface, exposed facets, and the crystal plane of Co3O4 plays an important role in determining its degree and easiness of presulfidation and consequently HDS performance for COS.In addition, considering palladium is one of the most active components in hydrogenation reaction, we further study the performance of Pd-supported catalysts for the HDS of COS. Adopting the above-mentioned CeO2 nanopolyhedra and several carbon materials as supports, including coconut active carbon (AC), high surface active carbon (SAC) and carbon nanotubes (CNTs), the activities of Pd/CeO2 and Pd/C catalysts for the hydrogenation of COS are determined. It is clear that Pd/CeO2 is superior to CeO2 itself, and the activity order of Pd/C is as follows:Pd/CNTs>Pd/SAC>Pd/AC under the same reaction condition, so the nature of support is a crucial factor for the COS hydrodesulphurization.更多还原