EAGER: GOALI: Explicating the gas-surface coupled reaction in oxidative coupling of methane via reaction kinetics, operando spectroscopy, photoionization spectrometry

甲烷是天然气的主要成分，虽然长期以来一直在寻找将其直接转化为高价值碳氢化合物的催化剂和工艺，但尚未实现广泛的工业应用。这项探索性研究早期概念资助（EAGER）项目旨在解决其中一项技术——甲烷氧化偶联（OCM）——以产生有可能克服商业化障碍的基本见解。OCM提供了可扩展的技术，可以更有效地利用甲烷，并且比现有技术的净碳排放量更低，从而支持美国向可持续能源过渡，同时确保能源安全。除技术方面外，该项目还包括在调查机构进行的几项教育和外联活动。该项目解决了催化OCM技术的几个知识空白：1)与气相反应相反，缺乏对催化剂如何与反应物偶联以激活甲烷并产生自由基的理解，2)哪种反应模式（多相或气相）控制所需产物与不需要产物的选择性，以及3)将甲烷选择性地转化为增值乙烷和乙烯（即C2）产物的首选催化剂和反应器设计。与桑迪亚国家实验室的科学家合作是解决这些挑战的关键。具体来说，研究人员将利用桑迪亚国家实验室的一个新型反应室来探测催化剂近表面区域的自由基。该仪器先前已用于纯气相燃烧研究中气相自由基的鉴定（利用真空紫外光电离质谱法（VUV-PIMS））。高温OCM反应的动力学和机理细节，由于缺乏实验能力，无法定量地询问催化剂和气相物种之间的耦合，这些耦合与自由基物种的表面生成以及这些物种在气相中的后续反应有关。桑迪亚仪器有潜力将催化OCM的机理和动力学方面提升到新的水平。动力学数据（与表面和气相反应相关）将被输入到反应器设计模型中（由国家可再生能源实验室（NREL）的合作者开发），以确定有利于甲烷选择性转化为C2碳氢化合物的催化剂和反应器设计。另外，GOALI合作伙伴PCI公司将在工业操作条件下对最先进的催化剂进行1000小时耐久性评估。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Methane is the major component of natural gas, and while catalysts and processes that convert it directly to higher-value hydrocarbons have long been sought, none have achieved widespread industrial application. This Early-concept Grant for Exploratory Research (EAGER) project addresses one of those technologies – Oxidative Coupling of Methane (OCM) – to generate fundamental insights that have potential to overcome barriers to commercialization. OCM offers scalable technology that would utilize methane more efficiently, and with lower net carbon emissions than current technology, thus supporting the U.S. transition to sustainable energy, while ensuring energy security. Beyond the technical aspects, the project includes several on-going educational and outreach activities at the investigators’ institution. The project addresses several knowledge gaps in catalytic OCM technology: 1) lack of understanding of how the catalyst, as opposed to the gas phase reactions, couples with the reactant species to activate methane and generate radical species, 2) which reaction mode (heterogeneous or gas phase) controls selectivity to desired versus undesired products, and 3) what are preferred catalyst and reactor designs for converting methane selectively to value-added ethane and ethylene (i.e., C2) products. Collaboration with scientists at Sandia National Labs is key to addressing those challenges. Specifically, the investigators will utilize a novel reaction chamber at Sandia National Labs for probing radical species in the near-surface region of a catalyst. The instrumentation has previously been used for identification of gas phase radical species in pure gas phase combustion studies (utilizing vacuum-ultraviolet photoionization mass spectrometry (VUV-PIMS)). Kinetic and mechanistic details of the high-temperature OCM reaction have eluded prior investigators because of lack of experimental capability to quantitatively interrogate the coupling between the catalyst and gas phase species as related to the surface generation of radical species and subsequent reaction of those species in the gas phase. The Sandia instrumentation has the potential to take mechanistic and kinetic aspects of catalyzed OCM to new levels of understanding. The kinetic data (as related to both surface and gas-phase reactions) will be fed into reactor design models (developed by a collaborator at the National Renewable Energy Laboratory (NREL) to identify catalyst and reactor designs that favor high conversion of methane selectively to C2 hydrocarbon species. In a separate thrust the GOALI partner PCI, Inc will conduct a thousand-hour durability evaluation of the state-of-the-art catalyst under industrial operating conditions.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.