Density Functional Theory Study of Dry Reforming of Methane
AuthorMoussa, Abdraman Mahamat
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the recent years, the global warming effects are being catastrophic and they start hitting new areas. These effects have a direct relation with the amount of greenhouse gases emitted into the atmosphere. CO2 and other greenhouse could be utilized as energy sources by capturing and utilizing them. Dry reforming of methane is one of them and it has economic feasibility that can be commercialized. In this study, density functional theory calculations were performed to study the promising dry reforming process on Ni111 surface by using SIESTA simulation package. SIESTA is considered to be fast reliable way to perform DFT calculations. Moreover, counterpoise correction was used in order to improve the accuracy. The calculations were performed for different potential active sites and orientations. The dissociation of CH4 and CO2 and their possible pathways were investigated in order to understand the kinetic of the process. The first CH4 dissociation was found to be the hard step to begin with. Horizontal CO2 is more favorable for its adsorption on Ni111. In this study, the adsorption energies were calculated using SIESTA and the results were tuned up using van der Waal counterpoise correction. Four different sites and orientations were selected to study the adsorption and know the most active site among them. To produce syngas from DRM, there are a lot of transitional molecules that need to be studied to determine the rate-determining step and these molecules affect the pathway of the reaction. This study shows that carbon can be adsorbed on the surface and that limits the active sites and deactivating the catalyst. This study has found that Ni-based catalysts can be considered as the optimum metals to be used in DRM among the transition metals. Noble metals were not considered due to their lack of economic feasibility even though they give more favorable results.
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