Understanding Structure-Function Relationships and Dynamical Restructuring in Near Surface Alloy Catalysts for Selective Oxidations

了解选择性氧化的近表面合金催化剂的结构-功能关系和动态重构

• 批准号: 2034911
• 负责人: Prashant Deshlahra
• 金额: $ 56.12万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2034911&HistoricalAwards=false
• 关键词: Understanding; Structure; Function; Relationships; Dynamical

The partial oxidation of hydrocarbons can generate compounds that contain oxygen atoms (oxygenates). Oxygenates are high-value chemicals that are essential intermediates in industrial processes and important ingredients in many consumer products. Partial oxidation reactions require efficient catalysts that selectively yield the desired oxygenate without completely oxidizing the compound to carbon dioxide. The development of more efficient and selective catalysts than those used in current chemical manufacturing is essential for decreasing manufacturing costs while reducing energy consumption and environmental impacts. Improved catalysts and catalytic processes also will enhance the competitiveness and sustainability of the U.S. chemical industry. This research project will study a new class of catalysts comprised of a single layer of silver atoms on inexpensive copper nanoparticles. Such catalysts hold significant promise for the selective partial oxidation of unsaturated hydrocarbons to epoxide-type oxygenates. The researchers will use experimental and computational methods to prepare the catalysts, to evaluate their performance, and to understand how the structure and electronic properties of the catalyst influence its reactivity and selectivity. The knowledge gained from this research will pave the way for the design of a next generation of partial oxidation catalysts for chemical manufacturing processes. The project also includes an outreach program to a local high school in which graduate students will assist high-school students in preparing their presentations for a local science fair. The project participants also will collaborate with a neighboring university on an Upward Bound Math Science program to provide early research experiences to low-income and first-generation college bound students.Near-surface alloys have been predicted by theory to have unique electronic structures that lead to deviations from scaling relationships that limit traditional catalysts. However, such catalysts exhibit intrinsic disorder and inhomogeneity introduced by segregation and restructuring that occur under relevant reaction conditions. This research project aims to develop an atomic-level understanding of AgCu near-surface alloys using surface science model studies, density functional theory simulations, and steady-state catalysis kinetics. A silver -terminated, AgCu near-surface alloy has been chosen for study due to its promising catalytic properties for partial oxidation reactions, which require both efficient activation of molecular oxygen and weak surface binding of intermediates. Preliminary data shows that these near-surface alloys enhance molecular oxygen activation by electronic modification of the silver layer by the underlying copper. Under reaction conditions isolated copper atoms are dynamically exposed, which further increases the molecular oxygen activation rate while maintaining a majority of silver sites at the surface. The silver sites promote selective oxidation via a bifunctional mechanism. The preliminary data also includes evidence for dynamic restructuring of AgCu near-surface alloys in response to surface oxidation. This restructuring yields highly active and selective model catalytic surfaces displaying 100% selective butadiene epoxidation. Building on these preliminary data, this research project will study the structural evolution and epoxidation reactions on model AgCu near-surface alloys and use density functional theory to enhance understanding of the structure, energetics, and electronic properties of the near-surface alloys. New AgCu near-surface alloy epoxidation catalysts will be synthesized and tested.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

碳氢化合物的部分氧化可生成含有氧原子(含氧化合物)的化合物。含氧物是一种高价值的化学品，是工业过程中必不可少的中间体，也是许多消费品的重要成分。部分氧化反应需要有效的催化剂，在不将化合物完全氧化成二氧化碳的情况下，选择性地产生所需的含氧物。开发比目前化学制造中使用的催化剂更有效和更有选择性的催化剂，对于降低制造成本，同时减少能源消耗和环境影响至关重要。改进的催化剂和催化工艺也将增强美国化学工业的竞争力和可持续性。这项研究项目将研究一种由廉价的铜纳米颗粒上的单层银原子组成的新型催化剂。这类催化剂在不饱和碳氢化合物选择性部分氧化成环氧化物型含氧物方面具有重要的应用前景。研究人员将使用实验和计算方法来制备催化剂，评估其性能，并了解催化剂的结构和电子性质如何影响其反应性和选择性。这项研究所获得的知识将为设计下一代用于化工生产的部分氧化催化剂铺平道路。该项目还包括一项针对当地一所高中的外展计划，在该计划中，研究生将帮助高中生准备他们在当地科学博览会上的演讲。项目参与者还将与邻近的一所大学合作开展向上绑定数学科学项目，为低收入和第一代大学毕业生提供早期研究经验。理论预测，近表面合金具有独特的电子结构，导致偏离限制传统催化剂的比例关系。然而，这类催化剂表现出内在的无序性和不均一性，这是由于在相应的反应条件下发生的分离和重组所引起的。本研究项目旨在通过表面科学模型研究、密度泛函理论模拟和稳态催化动力学，在原子水平上理解AgCu超表面合金。一种银端的AgCu近表面合金因其对部分氧化反应具有良好的催化性能而被选作研究对象，该反应需要分子氧的有效活化和中间体的弱表面结合。初步数据显示，这些近表面合金通过底层铜对银层的电子修饰来增强分子氧的活化。在反应条件下，孤立的铜原子被动态暴露，这进一步提高了分子氧的活化速度，同时保持了表面上的大多数银位置。银位通过双功能机制促进选择性氧化。初步数据还包括银铜近表面合金因表面氧化而发生动态重组的证据。这种重组产生了高活性和选择性的模型催化剂表面，显示出100%选择性的丁二烯环氧化反应。在这些初步数据的基础上，本研究项目将研究模型AgCu近表面合金的结构演变和环氧化反应，并使用密度泛函理论来加深对近表面合金的结构、能量和电子性质的理解。新的AgCu近表面合金环氧化催化剂将被合成和测试。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Detailed Kinetic Modeling of NO x -Mediated Oxidative Dehydrogenation of Propane

NO x 介导的丙烷氧化脱氢的详细动力学模型

• DOI: 10.1021/acs.iecr.1c02635
• 发表时间: 2021
• 期刊: Industrial & Engineering Chemistry Research
• 影响因子: 4.2
• 作者: Yu, Peng;Liu, Yilang;Deshlahra, Prashant;Wong, Hsi-Wu
• 通讯作者: Wong, Hsi-Wu

Selective Epoxidation of 1,3-Butadiene on AgCu Near-Surface Alloys

AgCu 近表面合金上 1,3-丁二烯的选择性环氧化

• DOI: 10.1021/acs.jpcc.2c01912
• 发表时间: 2022
• 期刊: The Journal of Physical Chemistry C
• 作者: Cramer, Laura A.;Daniels, Avery S.;Çinar, Volkan;Deshlahra, Prashant;Sykes, E. Charles
• 通讯作者: Sykes, E. Charles

Comparison of 2D crystals formed by dissociative adsorption of fluorinated and nonfluorinated alkyl iodides on Cu(111)

• DOI: 10.1116/6.0001316
• 发表时间: 2021-12-01
• 期刊: JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
• 影响因子: 2.9
• 作者: Balema，Tedros A.;Larson，Amanda M.;Sykes，E. Charles H.
• 通讯作者: Sykes，E. Charles H.