Understanding and Exploiting the Favorable Role of Non-Stoichiometric Oxygen in Bulk Metal Oxide Catalyzed Partial Oxidation of Light Alkanes

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Our Nation’s transition to clean energy requires more efficient utilization of fossil fuels combined with a transition to sustainable or biorenewable fuels generated through alternative energy sources such electricity produced from solar or wind energy. The current chemical market relies heavily on ethene – produced from the steam cracking of ethane (from natural gas) - to manufacture a wide range of commodity chemicals. Steam cracking is an energy-intensive process. The project explores an alternative, less energy-intensive, process for ethene manufacture via the oxidative dehydrogenation of ethane (ODHE). Controlled introduction of oxygen – in ways that promote ethene production without deeper oxidation to waste products such as carbon monoxide (CO) and carbon dioxide (CO2) – has been a major impediment to the commercial introduction of ODHE technology. The project addresses this technology gap by exploring a novel catalytic approach for enhancing ethene production while decreasing energy consumption. New catalyst synthesis techniques will be combined with reaction engineering concepts to achieve optimal supply of oxygen. In addition to facilitating the clean energy transition, the project includes educational and outreach efforts that raise awareness of the need for clean energy as related to carbon emissions and climate impact, while also training future scientists and engineers. Introduction of excess, non-stoichiometric oxygen in light-alkane ODH, while favorable for producing exothermicity and lowering the reaction temperature, has traditionally been avoided due to lower olefin selectivity associated with production of CO and CO2. The project seeks a paradigm shift in the study and design of bulk metal oxide catalysts by evidencing and exploiting a potentially favorable role of oxygen present in excess of that stipulated by metal oxide catalyst stoichiometry. Novel methods for assessing active site requirements on oxide surfaces, involving a range of kinetic, isotopic, and spectroscopic tools to assess the mechanistic function of non-stoichiometric oxygen, will be combined with advanced synthetic strategies for manipulating the catalytic function of surface oxygen moieties through control over dopant distribution and crystal habit. This synergistic approach - combining mechanistic investigations and advanced crystallization techniques such as molten salt syntheses - although applied specifically to nickel oxide catalyzed ODHE, may prove broadly applicable to high temperature catalytic partial oxidation reactions of industrial importance. Catalysts developed as part of the proposed work could form the basis for an inexpensive, energy-efficient route to producing ethene due to significantly lower operation temperatures compared to conventional processes. The investigators will use the findings of these studies in graduate-level courses at their institution, while continuing on-going STEM outreach activities in the Houston area including UH Energy Day and Chevron Girls Engineering the Future Day, providing high school students with hands-on research experience (Project ACS SEED), and mentoring undergraduate researchers.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.