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增值化学原料。特别是，该研究为两个甲烷分子如何耦合在一起形成具有两个碳原子的各种分子（OCM 反应）的机制提供了基础见解。 后一类型的分子是化学工业感兴趣的化学品和燃料。 OCM 反应作为大规模、资本密集型甲烷转化路线的更经济替代方案，在当前工业界具有重要意义，特别是对于那些无法将甲烷经济地运输到集中化工厂的偏远甲烷储层。该项目结合了研究、教学和推广计划，重点是了解性能最佳的 OCM 催化剂的局限性，并探索将其活性和选择性提高到超出当前水平的方案。 这项研究正在利哈伊谷达芬奇科学中心的年度夏季研讨会上展示，所有年龄段的游客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点课程中，每年将影响大约 180 名不同社会经济背景的初中生、高中生和本科生。 该研究是与国际研究人员合作进行的，这将允许他们使用理海大学不具备的尖端研究设施，提高研究的知名度，并使参与的学生接触到领先国际实验室的研究文化。该项目建立在假设负载型 Mn/Na2WO4/SiO2 催化剂的 OCM 活性位点是固定在二氧化硅载体上的孤立表面 WOx 物质。研究人员的初步研究首次发现，在 OCM 过程中存在未促进和促进的孤立表面 WOx 位点，可催化该反应。该项目的目标是（1）通过在 OCM 过程中应用现代原位和操作光谱结合动力学研究和密度泛函理论（DFT）建立基本的催化剂结构-活性关系，以及（2）应用新的基本见解指导在较低温度下运行的先进活性和选择性 OCM 催化剂的合理设计。正在合成未促进的以及Na-、Mn-和Na/Mn-促进的SiO2负载的WOx位点的各种排列。二氧化硅载体还用钠金属和纳米连接剂（TiOx、ZrO2、Al2O3）进行表面改性，这将增加孤立表面 WOx 位点的数量并调整其还原性和酸碱特性。正在系统地改变启动子与 W 的比率，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。使用原位和操作光谱（拉曼、紫外-可见和 NAP-XPS）对制备的催化剂和 OCM 反应条件进行表征，以确定二氧化硅上 WOx 位点的分子和电子结构。实验结果与分子水平 DFT 计算相补充，为结构-活性关系提供更多见解。同位素 CH4/CD4 和 16O2/18O2 的相应动力学研究分别解决了不同 WOx 位点的速率决定步骤和相对参与，后者通过时间分辨拉曼质谱进行。通过与欧洲合作伙伴的合作，利用分子束质谱法获得了有关气相自由基及其与特定催化剂结构的关系的信息。这些新见解将带来概念上新颖且现实的催化剂模型，这些模型将有可能促进一步式 OCM 催化过程的开发。成功执行拟议的研究有可能通过廉价、丰富但运输困难且成本高昂的甲烷来经济可行地生产 C2 碳氢化合物，从而使美国更接近能源独立，同时也为过渡到可持续发展提供更长的时间。化学品。该项目将涉及 Siluria 和 SABIC 两家公司的合作，这将促进新催化剂向化学工业的转移。

项目成果

Existence and Properties of Isolated Catalytic Sites on the Surface of β-Cristobalite-Supported, Doped Tungsten Oxide Catalysts (WO x /β-SiO 2 , Na-WO x /β-SiO 2 , Mn-WO x /β-SiO 2 ) for Oxidative Coupling of Methane (OCM): A Combined Periodic DFT and Exp

β-方英石负载的掺杂氧化钨催化剂（WO x /β-SiO 2 、Na-WO x /β-SiO 2 、Mn-WO x /β-SiO 2 ）表面孤立催化位点的存在和性质

• DOI: 10.1021/acscatal.9b05591
• 发表时间: 2020-04
• 期刊: ACS Catalysis
• 影响因子: 12.9
• 作者: Kiani, Daniyal;Sourav, Sagar;Taifan, William;Calatayud, Monica;Tielens, Frederik;Wachs, Israel E.;Baltrusaitis, Jonas
• 通讯作者: Baltrusaitis, Jonas

New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na 2 WO 4 /SiO 2 Catalysts

负载型 Na 2 WO 4 /SiO 2 催化剂上甲烷氧化偶联 (OCM) 的新机理和反应途径见解

• DOI: 10.1002/anie.202108201
• 发表时间: 2021-08
• 期刊: Angewandte Chemie International Edition
• 作者: Sourav, Sagar;Wang, Yixiao;Kiani, Daniyal;Baltrusaitis, Jonas;Fushimi, Rebecca R.;Wachs, Israel E.
• 通讯作者: Wachs, Israel E.

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

用于生物乙醇可持续生产正丁醇的羟基磷灰石表面化学

• DOI: 10.1016/j.checat.2021.06.005
• 发表时间: 2021-07-06
• 作者: Daniyal Kiani;J. Baltrusaitis
• 通讯作者: J. Baltrusaitis

Molecular structure and catalytic promotional effect of Mn on supported Na2WO4/SiO2 catalysts for oxidative coupling of methane (OCM) reaction

Mn在负载型Na2WO4/SiO2催化剂上甲烷氧化偶联(OCM)反应的分子结构及催化促进作用

• 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: Sourav, Sagar;Kiani, Daniyal;Wang, Yixiao;Baltrusaitis, Jonas;Fushimi, Rebecca R.;Wachs, Israel E.
• 通讯作者: Wachs, Israel E.

Elucidating the Effects of Mn Promotion on SiO 2 -Supported Na-Promoted Tungsten Oxide Catalysts for Oxidative Coupling of Methane (OCM)

阐明 Mn 促进对 SiO 2 负载的 Na 促进的氧化钨催化剂甲烷氧化偶联 (OCM) 的影响

• DOI: 10.1021/acscatal.1c01392
• 发表时间: 2021-08
• 期刊: ACS Catalysis
• 影响因子: 12.9
• 作者: Kiani, Daniyal;Sourav, Sagar;Baltrusaitis, Jonas;Wachs, Israel E.
• 通讯作者: Wachs, Israel E.