Molecular Structure and Reactivity of Model Mn/Na2WO4/SiO2 Oxidative Coupling of Methane Catalyst under Operating Conditions

Mn/Na2WO4/SiO2 型甲烷氧化偶联催化剂在操作条件下的分子结构和反应活性

• 批准号: 1706581
• 负责人: Jonas Baltrusaitis
• 金额: $ 45万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1706581&HistoricalAwards=false
• 关键词: Molecular; Structure; Reactivity; Model; Mn

This research project addresses the direct catalytic conversion of methane, the primary component of natural gas, to value-added chemical feedstocks. In particular, the research provides fundamental insight into the mechanisms of how two methane molecules couple together to form various molecules with two carbon atoms, the OCM reaction. The latter types of molecules are chemicals and fuels of interest to chemical industries. The OCM reaction is of current industrial interest as a more economical alternative to large-scale, capital-intensive routes for methane conversion, especially for remotely located methane reservoirs whose methane cannot be economically transported to centralized chemical plants. The project combines research, teaching and an outreach plan focused on understanding limitations of the best performing OCM catalyst, and exploring options for improving its activity and selectivity beyond current levels. This research is being showcased in annual summer workshops at the Lehigh Valley Da Vinci Science Center where visitors of all ages will be exposed to the new technologies being developed that convert methane to chemicals. Workshops, curricula development, and research integration into a senior Chemical Engineering Project Design capstone course will impact approximately180 middle-, high-school and undergraduate students of diverse socioeconomic backgrounds per year. The research is being conducted in collaboration with international researchers, which will allow access to cutting edge research facilities not available at Lehigh, enhance visibility of the research, and expose the participating students to the research culture in leading international laboratories.The project is built on the hypothesis that the active site for OCM by supported Mn/Na2WO4/SiO2 catalysts is an isolated surface WOx species anchored to the silica support. The investigators' preliminary studies have identified, for the first time, the presence of unpromoted and promoted isolated surface WOx sites during OCM that catalyze this reaction. The objectives of the project are to (1) establish the fundamental catalyst structure-activity relationships by application of modern in situ and operando spectroscopy during OCM combined with kinetic studies and density functional theory (DFT), and (2) apply the new fundamental insights to guide rational design of advanced active and selective OCM catalysts functioning at lower temperatures. Various permutations of unpromoted and Na-, Mn- and Na/Mn-promoted SiO2-supported WOx sites are being synthesized. The silica support is also being surface-modified with sodium metal and nanolinkers (TiOx, ZrO2, Al2O3) that will increase the number of isolated surface WOx sites and tune their reducibility and acid-base characteristics. The promoters-to-W ratios is being systematically varied to explore their effects on both the number and structure of the WOx sites and OCM activity/selectivity. The catalysts are being characterized as prepared and during OCM reaction conditions with in situ and operando spectroscopy (Raman, UV-vis and NAP-XPS) to determine the molecular and electronic structures of the WOx sites on silica. Experimental findings are being complemented with molecular level DFT calculations to provide additional insights into structure-activity relationships. Corresponding kinetic studies with isotopic CH4/CD4 and 16O2/18O2 are addressing the rate-determining-step and relative participation of different WOx sites, respectively, - the latter via time-resolved Raman-Mass Spectroscopy. Information about gas phase radicals and their relationship to specific catalyst structures is being obtained with Molecular Beam Mass Spectroscopy through collaboration with European partners. The new insights will lead to conceptually new and realistic catalyst models that will have the potential to enable development of one-step OCM catalytic processes. Successful execution of the proposed research has the potential to lead to economically viable production of C2 hydrocarbons from cheap, abundant, yet difficult and costly to transport methane, and thus move the US closer to energy independence while also providing a longer timeframe to transition into sustainable chemicals. The project will involve collaborations with two companies, Siluria and SABIC, that will facilitate transfer of new catalysts to the chemical industry.

该研究项目致力于将天然气的主要成分甲烷直接催化转化为附加值的化学原料。特别是，这项研究为两个甲烷分子如何结合在一起形成具有两个碳原子的不同分子的机制提供了基本的见解，即OCM反应。后一类分子是化学工业感兴趣的化学品和燃料。OCM反应目前在工业上是一种比大规模、资本密集型甲烷转化路线更经济的替代方案，特别是对于偏远的甲烷储存库，这些储气库的甲烷无法经济地运输到集中化工厂。该项目结合了研究、教学和推广计划，重点是了解性能最好的OCM催化剂的局限性，并探索在现有水平上提高其活性和选择性的备选方案。这项研究在利哈伊谷达芬奇科学中心的年度夏季研讨会上展示，所有年龄段的参观者都将接触到正在开发的将甲烷转化为化学品的新技术。研讨会、课程开发和研究整合到高级化学工程项目设计顶峰课程，每年将影响大约180名来自不同社会经济背景的初中生、高中生和本科生。这项研究是与国际研究人员合作进行的，这将允许访问利哈伊没有的尖端研究设施，提高研究的可见性，并使参与研究的学生接触到领先的国际实验室的研究文化。该项目建立在这样的假设基础上，即负载型Mn/Na2WO4/SiO_2催化剂对OCM的活性中心是固定在二氧化硅载体上的孤立的表面WOX物种。研究人员的初步研究首次证实，在OCM过程中，存在催化这一反应的未促进和促进的孤立表面WOX位点。该项目的目标是(1)在OCM过程中应用现代原位光谱和操纵谱，结合动力学研究和密度泛函理论(DFT)，建立催化剂的基本结构-活性关系，以及(2)应用新的基本见解来指导合理设计在较低温度下工作的先进的活性和选择性OCM催化剂。人们正在合成各种未促进和Na-、Mn-和Na/Mn促进的二氧化硅负载的WOX中心的排列。二氧化硅载体也正在用金属钠和纳米链接剂(TiOx、ZrO2、Al2O3)进行表面修饰，这将增加孤立的表面Wox位的数量，并调整它们的还原能力和酸碱特性。正在系统地改变启动子与水的比例，以探索它们对WOX位点的数量和结构以及OCM活性/选择性的影响。在OCM反应条件下和制备的催化剂进行了表征，并用原位和操纵面光谱(拉曼光谱、紫外可见光谱和NAP-XPS)确定了二氧化硅上WOX中心的分子结构和电子结构。实验结果与分子水平的密度泛函计算相辅相成，以提供对结构-活性关系的更多见解。同位素CH4/CD4和16O2/18O2的相应动力学研究分别解决了不同WOX位置的速率决定步骤和相对参与-后者通过时间分辨拉曼-质谱学进行。通过与欧洲合作伙伴的合作，正在使用分子束质谱学获得关于气相自由基及其与特定催化剂结构的关系的信息。新的见解将导致概念上的新的和现实的催化剂模型，将有可能使一步OCM催化过程的开发。这项拟议研究的成功实施，有可能导致从廉价、丰富但困难且成本高昂的甲烷运输中生产C2碳氢化合物在经济上是可行的，从而使美国更接近能源独立，同时也为过渡到可持续化学品提供了更长的时间框架。该项目将涉及与Siluria和SABIC两家公司的合作，这将促进将新催化剂转移到化学工业。

项目成果

Resolving the Types and Origin of Active Oxygen Species Present in Supported Mn-Na 2 WO 4 /SiO 2 Catalysts for Oxidative Coupling of Methane

解析甲烷氧化偶联负载型Mn-Na 2 WO 4 /SiO 2 催化剂中活性氧的类型和来源

• DOI: 10.1021/acscatal.1c02315
• 发表时间: 2021
• 期刊: ACS Catalysis
• 影响因子: 12.9
• 作者: Sourav, Sagar;Wang, Yixiao;Kiani, Daniyal;Baltrusaitis, Jonas;Fushimi, Rebecca R.;Wachs, Israel E.
• 通讯作者: Wachs, Israel E.

A Spectroscopic Study of Supported‐Phosphate‐Catalysts (SPCs): Evidence of Surface‐mediated Hydrogen‐Transfer

负载型磷酸盐催化剂 (SPC) 的光谱研究：表面介导的氢转移的证据

• DOI: 10.1002/cctc.202001897
• 发表时间: 2021
• 期刊: ChemCatChem
• 影响因子: 4.5
• 作者: Kiani, Daniyal;Baltrusaitis, Jonas
• 通讯作者: Baltrusaitis, Jonas

Synthesis and molecular structure of model silica-supported tungsten oxide catalysts for oxidative coupling of methane (OCM)

• DOI: 10.1039/d0cy00289e
• 发表时间: 2020-05-21
• 期刊: CATALYSIS SCIENCE & TECHNOLOGY
• 影响因子: 5
• 作者: Kiani, Daniyal;Sourav, Sagar;Baltrusaitis, Jonas
• 通讯作者: Baltrusaitis, Jonas

Surface chemistry of hydroxyapatite for sustainable n-butanol production from bio-ethanol

• DOI: 10.1016/j.checat.2021.06.005
• 发表时间: 2021-07
• 作者: Daniyal Kiani;J. Baltrusaitis

Molecular Structure and Catalytic Promotional Effect of Mn on Supported Na2WO4/SiO2 Catalysts for Oxidative Coupling of Methane (OCM) Reaction

• DOI: 10.1016/j.cattod.2022.07.005
• 发表时间: 2022-07
• 期刊: Catalysis Today
• 影响因子: 5.3
• 作者: S. Sourav;Daniyal Kiani;Yixiao Wang;J. Baltrusaitis;R. Fushimi;I. Wachs