CAREER: Theory-guided design of a novel chemical looping process for methane coupling using hydrogen storage materials

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1454384 - GrabowAn economically viable process to transform abundant natural gas, primarily composed of methane (CH4), to higher value products (e.g. ethane or ethylene) could revolutionize the chemical industry. The prevailing challenge in all processes using CH4 feedstock is activating the strong C-H bond, which is typically done in the presence of an oxidizing agent and requires high temperatures for activation coincidentally leading to unselective reaction pathways. The primary goal of this project is to develop a new chemical looping process for selective CH4 coupling in the absence of oxygen using hydrogen storage materials. First principles calculations will guide the selection of promising hydrogen storage materials and subsequent reaction/diffusion modeling will further narrow down the group of candidate materials. Laboratory scale experimental testing is used to verify the model predictions and to optimize the operating conditions. Recent technological developments in hydraulic fracturing (fracking) to produce shale gas provide a huge incentive to develop commercially viable methane conversion processes to benefit the U.S. economy. Utilization of large shale and tight gas reservoirs in the U.S. and many other parts of the world have led to an increased interest in its main component, methane (CH4). As of 2011 the proven natural gas reserves total 208.4 trillion cubic meters worldwide, of which 7.72 trillion cubic meters are located in the U.S. Natural gas is also a significant byproduct during oil production and an estimated 150 billion cubic meters are being flared annually.Traditional uses of methane include electricity generation (combustion) and conversion to syngas, a mixture of CO and H2, using steam reforming over Ni-based catalysts.However, the potential for methane as a feedstock for the production of liquid hydrocarbons and useful chemicals has not yet been fully realized and an economically viable methane to higher value chemicals upgrade process could revolutionize the energy sector and chemical industry. The pervasive challenge of using CH4 as feedstock is activating the very strong C-H bond (435 kJ/mol). Currently implemented processes utilizing CH4 require high temperatures and the presence of oxygen-containing species (e.g. O2, H2O, CO2). These processes work well for the generation of syngas, which can subsequently be converted to higher hydrocarbons in a Fischer-Tropsch synthesis reactor. However, the direct conversion of CH4 to C2+ species remains one of the grand challenges in the chemical industry. Oxidative coupling of methane (OCM), could potentially address this challenge, but decades of intensive research have not been able to solve the issue of carbon selectivity. The competing combustion reaction consumes a large fraction of the CH4 feedstock and the high reactivity of the CH3 intermediates in the presence of O2 presents an insurmountable obstacle. In this research project a new process for methane coupling is proposed, which uses chemical looping and hydrogen storage materials to separate the carbon and oxygen atoms in order to avoid the formation of undesired carbon monoxide (CO) or carbon dioxide (CO2). The proposed research activities will be integrated with broad-reaching educational efforts at the K-12, undergraduate, graduate and professional level to broaden the participation of minority students and increase the retention of at-risk students. Partnerships with Marlo Diosomito and two economically disadvantaged Title-1 high schools in the Cypress Fairbanks ISD that the PI supervises will be leveraged to generate more interest in STEM disciplines and increase the representation of students from low-income families. UH is a designated Hispanic-Serving Institution and has the most ethnically balanced student body of all major research institutions in the U.S.