Electronic Metal-Support Interactions in Fischer-Tropsch Catalysis

费托合成(FTS)是一种广泛使用的化工生产工艺，主要用于将蒸汽重整的天然气转化为适用于燃料、润滑油和其他化工产品的长链烃或有机分子。FTS反应通常在高压下进行，在高压下一氧化碳(CO)和氢(H2)之间的催化反应更受欢迎。如此高的压力要求极大的反应堆和相关的化工厂，以实现成本效益高的制造所需的规模经济。该项目研究了FTS的另一种方法，即调整催化剂的性质，以促进在较低压力下的反应。较低的压力反过来又可能为小型工厂提供具有成本效益的FTS打开大门，这些工厂可以靠近偏远或搁浅的天然气来源或分散的可再生生物质来源。随着我国向制造燃料和化学品的净零碳排放技术过渡，低压分布式FTS的一个关键好处在于它能够确保化学制造的安全。该项目通过一个中心假设来探索电子金属-载体相互作用(EMSI)，即碱性载体将向其上支撑的金属团簇注入电子密度，而这种电子给予将反过来导致CO更强地结合到金属表面。具体地说，研究人员将合成并评估以通式为MgxAlyO的混合金属氧化物为载体的Ru(Ru)和Co(Co)催化剂。镁铝比将控制载体的碱性，进而控制向载体Co和Ru的电子给予的程度。这些金属的电子结构的变化将由L边缘X射线吸收光谱(XAS)来监测。实验数据(包括通过傅里叶变换红外光谱(FTIR)和CO程序升温脱附(TPD)对CO结合强度的直接评估)将通过密度泛函理论(DFT)计算和Bader分析进行验证，以确认金属/载体和吸附对电子结构和电荷转移的影响。在表征和计算分析之后，将在实验室反应器中对实际操作条件下的FT反应进行动力学研究。更广泛地说，该项目通过减少滞留天然气升级为液体燃料的资本和运营费用，可能会为美国带来经济效益。该项目还将对研究生、本科生和高中生进行与化学过程工程相关的催化方面的培训。该奖项反映了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。

Fischer-Tropsch synthesis (FTS) is a widely employed chemical manufacturing process, primarily used to convert steam-reformed natural gas to long-chain hydrocarbons or organic molecules suitable for fuels, lubricants, and other chemical products. The FTS reaction is typically run at high pressures where the catalyzed reaction between carbon monoxide (CO) and hydrogen (H2) is favored. Such high pressures demand extremely large reactors and associated chemical plants to achieve the economies of scale needed for cost-effective manufacturing. The project investigates an alternative approach to FTS in which the catalyst properties are tuned to promote reaction at lower pressures. The lower pressures, in turn, potentially open the door to cost-effective FTS in smaller scale plants that can be located close to remote or stranded sources of natural gas or distributed sources of renewable biomass. A key benefit of low-pressure, distributed FTS resides in its capability to ensure security in chemical manufacturing as our nation transitions to net-zero carbon emission technologies for manufacturing fuels and chemicals. The project explores Electronic Metal-Support Interactions (EMSI) through the central hypothesis that a basic support will inject electron density into the metal clusters supported on them, and this electron donation will, in turn, result in stronger binding of CO onto the surface of the metal. Specifically, the investigators will synthesize and evaluate ruthenium (Ru) and cobalt (Co) catalysts supported on mixed metal oxides of the general formula MgxAlyO. The Mg:Al ratio will control the basicity of the supports and, in turn, the extent of electron donation into the supported Co and Ru. Changes in the electronic structure of the metals will be monitored by L-edge X-ray absorption spectroscopy (XAS). The experimental data (including direct assessment of CO binding strength via Fourier Transform Infrared Spectroscopy (FTIR) and CO temperature-programmed desorption (TPD)) will be validated with density functional theory (DFT) calculations and Bader analysis to confirm metal/support and adsorbate effects on the electron structure and charge transfer. The characterization and computational analyses will be followed by kinetic studies of the FT reaction under realistic operating conditions in a laboratory reactor. More broadly, the project will potentially lead to economic benefits for the U.S. by reducing capital and operating expenses for stranded natural gas upgrading to liquid fuels. The project will also train graduate, undergraduate, and high-school students in aspects of catalysis as related to chemical process engineering.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.