Natural gas is widely used for combustion to generate heat and electricity. Each natural gas drilling site produces stranded gas, and the producers flare the stranded gas at the site due to economic reasons. To reduce the waste of this natural resource, it is worthwhile to utilize the stranded natural gas to produce value-added chemicals. One of the challenges in direct methane utilization is low single-pass conversion due to the difficult C-H bond activation. This presentation provides a route to improve methane conversion: applying microwave (MW) radiation into the reactor design, that can be applied to the individual wellhead to upcycle the stranded gas.<br/>Many research works have discovered that microwave radiation can assist chemical reactions and improve catalyst performance. The numerical simulation of the MW reactor is one of the main directions of reactor development and mechanistic study. Several physics are involved in a microwave-assisted gas-solid catalytic process. The involvement of electromagnetic waves will affect heat transfer and bring other effects. These physics make the mechanistic study of MW-assisted reactions complicated. In this presentation, the authors study the catalytic performance of methane dehydroaromatization experimentally and utilize finite-element simulation to investigate the microwave-material interaction.<br/>The results show that the methane conversion can reach 18% at 550 °C under microwave radiation, while a temperature higher than 800 °C is required to achieve the same level of conversion in a thermal reactor. The microwave radiation facilitates this catalytic process both thermally and non-thermally. Thermal effect, as known as “hot spots”, can be characterized experimentally, and the result indicates the hot spot temperature can reach 800 °C while the bulk temperature stays at 550 °C. The simulation results show the electric field on the catalyst bed is at a level of 10<sup>4</sup> V/m, and the model shows the existence of high electric field spots between spherical catalyst particles. Under this level of external electric field, methane activation on the catalyst surface is possible through molecular deformation and polarization. The outcome of this research suggests new avenues for the understanding of microwave-dielectric material interaction as well as optimization of catalytic processes via combination of experimental microwave-assisted operation and finite-element simulation.

Combined experimental and modeling study of microwave-assisted methane dehydroaromatization process

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ACS Fall 2022

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