(732g) Microwave Catalysis for Process Intensified Modular Production of Value-Added Chemicals from Natural Gas

"The microwave-assisted catalytic conversion of methane to value-added chemicals was explored over a 4-wt% Mo/ZSM-5 catalyst premixed with 40-wt% SiC powder. A benzene yield of 3.5% was achieved at a catalyst surface temperature of 550℃. Regeneration experiments were performed under 2% O2/N2 under microwave at 100 W/500℃. Benzene yields dropped after the first regeneration cycle but stayed constant for the subsequent two cycles. The design of an H-Field cavity increased the testing capacity to a maximum of 20g of catalyst. A linear increase in yield with the increase in catalyst mass suggests that at the current rate of aromatics + C2 production could be produced at 2043 g/day.kg-1catalyst. Process simulation and technoeconomic analysis results indicate that energy efficiency improvement of 58% can be achieved compared to the base case. The energy penalty for the new MW-assisted catalysis process is about 2x times less than the base case. The technoeconomic analysis resulted in a positive net present value for the microwave-assisted plant-wide model.

To further increase the efficiency of the microwave, a microwave-sensitive SiC@Fe-ZSM-5 core@shell catalyst was designed to enhance the direct heating of the zeolite. It was found that the Core@ Shell design increased the heat transfer to the Fe/ZSM-5 more efficiently than the physically mixed SiC catalyst. The temperature of the zeolite phase in the core@shell catalyst was higher than that of the physically mixed catalyst, thus resulting in a higher C6 yield. A temperature-indicating probe molecule was used to estimate the catalyst's temperature distribution and metal site temperature under microwave heating. The scaled-up production of the microwave-sensitive Fe-ZSM-5 catalyst was also explored through the design of a continuous zeolite synthesis system. The designed synthesis system yielded a 100x increase in the space-time yield of zeolite produced compared to lab-scale batch processing of six 50-mL batches per 6 days.
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