INVESTIGATION OF FACTORS AFFECTING ADSORPTION CAPACITY AND SELECTIVITY OF ACTIVATED CARBON IN HIGHLY EFFICIENT DESULFURIZATION OF DIESEL FUEL

Bandosz最近的环境法规将汽油中的硫限制在30ppm，柴油中的硫限制在15ppm(2006)。尽管越野燃料中500ppm的硫磺仍然是一个可以接受的水平，但到2010年，限制将设定为15ppm。加氢脱硫(HDS)是一种能够脱除化石燃料中大部分含硫化合物的方法。尽管HDS具有高效率和公认的技术重要性，但它不能完全去除二苯并噻吩类化合物。特别是4，6-二甲基二苯并噻吩类化合物被认为对任何化学反应都具有抵抗力。在这里提出的研究计划中，我们试图确定控制深度脱硫过程的碳质吸附剂的特性，并开发高效的柴油脱硫介质。我们的目标脱除过程是基于从极低浓度的20ppm硫磺中反应吸附DBT和4，6-DMDBT。在“最好的情况下”，噻吩类分子将首先被特异性地吸附在催化金属中心/含杂原子的基团上，然后碳硫键将发生断裂，硫保留在表面，碳氢分子返回燃料流。在“最坏的情况”中，DBT和4，6-DMDBT分子将被特异性地吸附在金属氧化物、硫化物、硫、氮、磷或含氧中心的孔系统中。可以存在中间交互的各种场景。我们将提供制备最有效的去除介质的详细实验程序(从容量、选择性和再生可行性的角度)以及该过程的机理。吸附剂在液相脱硫中的性能与其表面特性密切相关。这将为设计更高效、更具成本效益的吸附剂和催化剂开辟新的途径。我们对文献和研究经验的回顾引出了以下与实现我们的目标和开发新技术相关的研究问题：1)什么温度的碳化会导致最有效的吸附剂/催化剂？2)哪些杂原子确实提高了吸附的能力和选择性？3)哪些金属/表面基团或它们的组合是最有效的脱硫剂？4)哪种金属含量的金属容量最高？5)表面反应的产物(如果有)是什么？6)吸附的机理是什么？7)我们能有效地再生用过的吸附剂吗？8)我们能否设计一种具有表面特征的吸附剂(基于商用碳质前体)，从而有效地深度脱除柴油中的硫？建议的研究直接关系到开发新材料和改进柴油和其他重油馏分的脱硫技术。由于新的环境法规，不仅在美国，而且在世界范围内，石化、化工和发电行业对从噻吩类物种中脱除硫的新型吸附剂和催化剂产生了极大的兴趣。所开发的技术除了降低未来低硫燃料的成本外，还可能对燃料电池这一前沿技术的发展起到重要作用，因为由于硫化合物对重整催化剂的毒害，无硫氢源是重整催化剂的首要任务。这项研究还将导致一类新的吸附剂和催化剂，这可能会在涉及分子分离的其他科学挑战中得到应用。此外，广泛应用的表面表征方法将对更好地理解碳和碳质吸附剂的表面化学产生影响。这项拟议的研究与当代社会面临的环境问题有关。首先，它将开发符合环境法规的相对简单的技术，并将在不久的将来开始。通过降低燃料中的硫含量，减少二氧化硫的排放，从而减少酸雨事件及其对环境和人类健康的不利影响。此外，昂贵的汽车尾气催化剂的使用寿命将会延长。一名研究生和一名本科生将参与该项目。由于CCNY是一所为少数群体服务的机构，来自代表性不足群体的学生很有可能参与到这项研究中。这将对少数群体环境意识的发展产生积极的影响。其他重要的教育方面是新环境的发展。本科生参与研究的化学实验(独立研究型本科项目)和研究生-本科生团队的工作方法，包括研究/解决问题的所有步骤，包括搜索文献资源，熟悉科学仪器的操作原理，以及概述研究论文和研究计划的能力。

0930858BandoszRecent environmental regulations set the limits of sulfur in gasoline to 30 ppm and in diesel fuel to 15 ppm (2006). Even though in the off-road fuel 500 ppm of sulfur is still an acceptable level, the limits are set to be 15 ppm by 2010. Hydrodesulfurization (HDS) is a method, which is able to remove the majority of sulfur-containing compounds from fossil fuel. In spite of the high efficiency and established technological importance of HDS it is not able to remove completely dibenezothiophenes. Especially 4,6 - dimethyldibezothiophene is considered as resistant to any chemical reactions. In the research program proposed here we seek to define the features of carbonaceous adsorbents that govern the deep desulfurization process and to develop efficient diesel fuel desulfurization media. The removal process we target is based on reactive adsorption of DBT and 4, 6-DMDBT from very low concentration of 20 ppm sulfur. In the "best case scenario", thiophenic molecules will first be specifically adsorbed on the catalytic metal center/ heteroatom containing groups and then the breaking of the carbon sulfur bond will occur with retention of sulfur on the surface and a return of the hydrocarbon molecule to the fuel stream. In the "worse case scenario", the DBT and 4,6-DMDBT molecules will be specifically adsorbed in the pore system on metal oxides, sulfides, sulfur, nitrogen, phosphorus or oxygen containing centers. Various scenarios of the in-between interactions can exist. We will provide the detailed experimental procedure for the preparation of the most efficient removal media (from the point of view of the capacity, selectivity and regeneration feasibility) along with the mechanism of the process. The performance of adsorbents in desulfurization from liquid phase will be linked to their surface features. This will open new routes for designing more efficient and cost effective adsorbents and catalysts. Our review of the literature and research experience lead to the following research questions related to achieving our objectives and to the development of new technology: 1) Which temperature of carbonization does lead to the most effective adsorbent/catalyst? 2) Which heteroatoms do enhance the capacity and selectivity of adsorption? 3) Which metals/ surface groups or their combinations are the most effective desulfurization catalysts? 4) Which content of metal does result the highest capacity? 5) What are the products of surface reactions (if any)? 6) What is the mechanism of adsorption? 7) Can we efficiently regenerate the spent adsorbents? 8) Can we design an adsorbent (based on the commercial carbonaceous precursors) with the surface features leading to the effective deep desulfurization of diesel fuel? The proposed research is directly relevant to developing new materials and improving technologies of desulfurization of diesel fuel and other heavy fuel fractions. Due to new environmental regulations, not only in the US but also worldwide, there is a great interest in petrochemical, chemical and power generating industries in new adsorbents and catalysts for withdrawal of sulfur from thiophenic species. The technology developed besides lowering the cost of future low sulfur level fuel, may also prove to be important for development of fuel cell, cutting edge of technology, where sulfur free hydrogen source is the first priority due to the poisoning of the reforming catalysts by sulfur compounds. The research will also lead to a new class of adsorbents and catalysts, which may find application in other scientific challenges where the separation of molecules is involved. Moreover, the broad spectrum of surface characterization methods applied will have an impact on better understanding the surface chemistry of carbon and carbonaceous adsorbents in general. The proposed research is relevant to environmental problems facing contemporary society. First, it will develop the relatively simple technology in compliance with environmental regulations to be commenced in the near future. By decreasing the level of sulfur in fuel, the emissions of SO2 will be reduced, which will lead to the reduction in acid rain incidents and their detrimental effects on the environments and human health. Moreover, the lifetime of the automobile exhaust expensive catalyst will be prolonged. One graduate student and one undergraduate student will work on the project. Since CCNY is a minority serving institution there is a high probability that students from underrepresented groups will be involved in the research. This will have a positive effect on the development of environmental awareness in the minority group. Other important educational aspects are the development of new environ./phys. chemistry experiments by the undergraduate student involved in the research (independent research undergraduate project) and the graduate ?undergraduate teem working approach with all steps of research/problem solving including searching literature resources, familiarity with the principles of operation of scientific instruments and the ability to outline research theses and research plans.