Understanding the Role of Activated Oxygen Species in the Room Temperature Conversion of Methane to Methanol

在化石资源中，天然气-特别是甲烷（其主要成分）-是生产各种碳氢化合物化学品的最有吸引力的原料。 作为世界领先的甲烷生产国，美国拥有巨大的页岩甲烷储量，以及未来大量沼气甲烷的可用性，美国有能力在甲烷到化学品的革命中引领世界。 不幸的是，现有的甲烷转化方法在能量上是低效的，导致显著的二氧化碳（CO2）排放。 现有甲烷活化方法的一种有前景的替代方法是由催化剂促进的低温水性电化学转化。 当与风能和太阳能等可再生能源相结合时，电催化过程理论上可以实现完全无二氧化碳的甲烷化学品和燃料生产。 为此，该项目将研究各种电催化甲烷反应途径，最终目标是开发廉价、高效和经济的燃料和化学品，如甲醇。具体而言，该项目将结合联合收割机两个高水平的科学目标，研究五种已知的途径，以产生甲烷至甲醇反应所需的表面活性氧物种。第一个目标是确定活性氧物种的类型和电化学电位对反应选择性和活性的影响。 对于每一个活性氧途径，第二个目标侧重于确定的速率决定步骤相结合，在反应过程中与电化学数据的表面物种的原位表征。这两个目标一起将标准电化学技术与表面增强红外光谱、同位素标记和GC/MS产物表征结合联合收割机，以揭示每个途径的速率、选择性和反应顺序。为了实现这五种途径，只需要3种不同的催化剂：氧化的多晶Pt、RuO 2和NiO：ZrO 2。 催化剂化学性质和形状因子的数量被有意地限制，以促进理解的深度，其可以告知对甲烷活化具有甚至更大活性和对甲醇形成的选择性的另外的催化剂的进一步开发。通过科学目标产生的基本理解将直接提供给两个本科生领导的工程活动，使研究和教育的强有力的整合。以实验室为基础的本科生研究将侧重于将向下选择的催化剂整合到新的反应器方案中。此外，本科生高级设计团队将专注于设计新反应堆周围的支持工厂平衡，并对各种配置进行初步的技术经济评估。 最后，该项目将通过几个实践推广计划来平衡，这些计划针对的是代表性不足的高中生。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Among fossil resources, natural gas - especially methane (its chief component) – is the most attractive feedstock for producing a wide range of hydrocarbon-based commodity chemicals. As the world’s leading methane producer, and with vast reservoirs of shale methane, as well as the future availability of a significant amount of biogas methane, the U.S. is in position to lead the world in a methane-to-chemicals revolution. Unfortunately, existing methane conversion processes are energetically inefficient, resulting in significant carbon dioxide (CO2) emissions. One promising alternative to existing processes for methane activation is low temperature, aqueous electrochemical conversion as promoted by catalysts. When paired with renewable energy sources, like wind and solar, electrocatalytic processes can theoretically achieve completely CO2-free production of chemicals and fuels from methane. To that end, the project investigates various electrocatalytic methane reaction pathways, with the eventual goal of enabling the development of inexpensive, efficient, and economical fuels and chemicals, such as methanol.Specifically, the project will combine two high-level scientific aims to investigate five known pathways to create the surface-active oxygen species needed to enable the methane-to-methanol reaction. The first aim focuses on identifying the types of activated oxygen species and the effects of electrochemical potential on reaction selectivity and activity. For each active oxygen pathway, the second aim focuses on identifying the rate determining step by combining in-situ characterization of the surface species during reaction with electrochemical data. Together the two aims combine standard electrochemical techniques with surface enhanced infrared spectroscopy, isotope labeling and GC/MS product characterization to uncover the rate, selectivity, and reaction order for each pathway. To enable the five pathways, only 3 different catalysts are needed: oxidized polycrystalline Pt, RuO2 and NiO:ZrO2. The number of catalyst chemistries and form factors are purposely limited, to promote a depth of understanding that can inform further development of additional catalysts that have even greater activity towards methane activation and selectivity for methanol formation. The fundamental understanding generated through the scientific aims will be fed directly to two undergraduate-led engineering activities, allowing for strong integration of research and education. Laboratory-based undergraduate research will focus on integrating down-selected catalysts into new reactor schemes. Additionally, undergraduate senior design teams will focus on designing the supporting balance-of-plant around the new reactors, and performing preliminary techno-economic assessments of various configurations. Finally, the project will be balanced by several hands-on outreach programs to under-represented high-school students.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.