Mechanism of Epoxidation of Propylene with H2/O2 Mixtures

H2/O2 混合物环氧化丙烯的机理

• 批准号: 0651238
• 负责人: S. Ted Oyama
• 金额: --
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0651238&HistoricalAwards=false
• 关键词: Mechanism; Epoxidation; Propylene; H2; O2

PROPOSAL NUMBER: 0651238PRINCIPAL INVESTIGATOR: Oyama, S. TedINSTITUTION: Virginia Polytechnic Institute and State UniversityScientific Merit. The epoxidation reaction of propylene with gas-phase hydrogen and oxygen mixtures is of considerable importance as a possible replacement for current processes employing hydrogen peroxide or organic peroxides. Although the reaction is of commercial significance, the mechanism by which it operates has not been clarified, and a deeper understanding will lead to improved catalysts. Existing catalysts consists of nano-sized gold particles dispersed on a titanosilicate support. The oxidant mixture of oxygen and hydrogen is believed to form hydrogen peroxide on the gold particles, which then migrates to titanium centers to form hydroperoxides, which are responsible for the epoxidation reaction. We plan to study this catalytic system using several in situ techniques, including ultraviolet-visible (UV-vis) absorption spectroscopy, laser Raman spectroscopy (LRS), Fourier transform infrared spectroscopy (FTIR), and extended and near-edge x-ray absorption spectroscopy (EXAFS, XANES) to study the structure and function of working catalysts so as to obtain insight on the mechanism by which they operate. The studies will be supported by ab initio Hartree-Fock calculations to describe active sites and adsorbates. Study of the catalysts at reaction conditions using in situ UV-vis and LRS will give information about the hydroperoxide adsorbed intermediate and the nature of the ratedetermining step (rds). FTIR will probe the nature of adsorbed organic moieties. The adsorbed intermediates will be studied using transient techniques to determine whether they respond to perturbations at a rate consistent with the overall rate of reaction, and thus, to establish whether they are reactive participants or merely spectators. In situ EXAFS will be used to study the coordination of the Ti centers, and in situ XANES will probe the oxidation state of the gold at reaction conditions. The best reported catalyst is gold supported on the microporous zeolite TS-1. Work will be carried out to improve the catalyst by creating mesoporous structures with TS-1 building blocks. The mesoporosity will give the reactants better access to the active sites, while the microporosity will protect the sites from deactivation by adsorption of products of reaction. The effect of the particle size of the gold will be studied by varying the pH of deposition. The catalysts will also be studied in a membrane reactor to allow the safe mixing of the hydrogen and oxygen components. The separate feed of these reactants will allow the use of concentrations within the explosive regime, without the danger of detonation. The higher levels of hydrogen and oxygen should lead to higher rates.Broader Impact. The proposed project has broad aspects of benefit to society. First, the research will not only advance understanding of the epoxidation reaction, but will also develop general techniques for use in other systems to study catalysts in their working state. Second, the project has a strong international component, as part of the research will involve use of facilities at a National Institute in Japan (Advanced Industrial Science and Technology-AIST). Funds for living costs for the PI and students have already been approved from the Institute. Third, the project will have an emphasis in the training and education of minority and women students. In the past our laboratory has successfully recruited members from underrepresented groups and this will be continued. Fourth, a substantive collaboration will be initiated with a faculty member from a local undergraduate school (Radford Univ.) to promote personal growth of the individual, as well as to stimulate the participation of students from that school in higher education.

提案编号：0651238原理调查员：Oyama，S。Tedinstitution：弗吉尼亚理工学院和州立大学得科的优点。丙烯与气相氢和氧混合物的环氧化反应非常重要，因为可能替代使用过氧化氢或有机过氧化氢的当前过程。尽管反应具有商业意义，但其运作的机制尚未澄清，并且更深入的了解将导致催化剂的改善。现有的催化剂由分散在钛硅酸盐支撑上的纳米大小的金颗粒组成。氧化物和氢的氧化剂混合物被认为在金颗粒上形成过氧化氢，然后将其迁移到钛中心以形成氢过氧化物，这些氢过氧化物是造成环氧化反应的原因。我们计划使用几种原位技术研究这种催化系统，包括紫外线可见（UV-VIS）吸收光谱，激光拉曼频谱（LRS），傅立叶变换红外光谱谱（FTIR），以及扩展和近乎边缘的X射线吸收光谱（Exafs），XANES和XAN的功能，以及X射线的范围，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及XAN的功能，以及Xanes的功能，以及在Xanes上的工作，以及Xanes的功能，以及XaneS的功能，以及XaneS的工作，以及XaneS的启示范围，以下是XaneS的工作，以及XaneS的启示范围和功能。它们运行的​​机制。这些研究将由Hartree-fock计算的主张支持，以描述活跃的地点和吸附物。使用原位UV-VIS和LRS对催化剂的研究将提供有关吸附的氢过氧化物中间体的信息以及评分序列步骤（RDS）的性质。 FTIR将探究吸附的有机部分的性质。将使用瞬态技术对吸附的中间体进行研究，以确定它们是否以符合整体反应速率一致的速率对扰动做出反应，从而确定它们是反应性参与者还是仅仅是观众。原位EXAF将用于研究TI中心的配位，原位Xanes将在反应条件下探测黄金的氧化态。最好的报道催化剂是在微孔沸石TS-1上支撑的金。将通过创建具有TS-1构件的介孔结构来进行改善催化剂的工作。中膜性将使反应物更好地进入活性位点，而微孔力将通过吸附反应产物来保护位点免于失活。通过改变沉积的pH，将研究金的粒径的影响。还将在膜反应器中研究催化剂，以使氢和氧成分的安全混合。这些反应物的单独饲料将允许在爆炸性方面使用浓度，而不会出现爆炸的危险。较高水平的氢和氧应导致更高的速率。拟议的项目对社会有利。首先，这项研究不仅将提高对环氧化反应的理解，而且还将开发出在其他系统中使用的通用技术来研究其工作状态的催化剂。其次，该项目具有强大的国际组成部分，作为研究的一部分，将涉及日本国家研究所（先进的工业科学和技术劳动）的设施。 PI和学生的生活费用资金已经获得该研究所的批准。第三，该项目将重点放在少数民族和女学生的培训和教育上。过去，我们的实验室已成功招募了代表性不足的团体的成员，这将继续。第四，将与当地本科学校（拉德福大学）的一名教职员工开始实质性合作，以促进个人的个人成长，并刺激该学校的学生参与高等教育。