Graduate Thesis Or Dissertation
 

An Investigation into the Production of Longer Hydrocarbons, Synthesis Gas, and Ammonia via a Nonthermal Plasma Microreactor

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  • Nonthermal electrical plasmas can allow energy intensive reactions to occur without the use of high operating temperatures or pressures. This is because the collisions of electrons accelerated through an electric field with molecules is the cause of reactions as opposed to thermal collisions between molecules. In this study, the production of larger hydrocarbons and synthesis gas from methane and the production of ammonia from nitrogen and hydrogen were investigated experimentally and then empirically modeled. It was found that selectivity and energy efficiency of methane dry reforming was greatly impacted by increasing the pressure of the reactor. Carbon dioxide, air, or a combination of the two had to be added to the methane mixture in order to mitigate carbon deposition within the reactor. Methods to mitigate or eliminate deposition were examined with longevity studies to understand how long-term operation of the reactor would affect product distribution and discharge stability. Ammonia production was possible in the electrical plasma despite the high bond energy of nitrogen. Product yields were much lower when compared to methane reforming. It was found that electron current was much more important for this process compared to composition, confirming that the electrons are the main driver of this reactor. A microreactor was used because shorter discharges require less voltage, allowing reactions to occur with a relatively small voltage (~500 V) compared to reactors with larger distances between electrodes. This microreactor had the same geometry for all experiments. This allowed direct comparisons between the methane reaction system and the production of ammonia, which gave insights into how these reactions proceed in the plasma. From these studies, it is possible there may be future opportunities to tune the product distribution in methane dry reforming. With a higher energy efficiency at higher pressures, plasma processes may be made more economically viable. Conversion and selectivity in the plasma can be held constant over longer time periods if efforts to mitigate deposition in the reactor and on the electrodes are taken. While it was shown that ammonia could be produced in the plasma microreactor at ambient pressure, improvements will be need to be made to improve the efficiency of the process to make it more economically viable.
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  • Pending Publication
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  • 2020-09-17 to 2022-10-17

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