Microwave heated chemical looping ammonia synthesis over Fe and CoMo particles

Chemical looping ammonia synthesis (CLAS) materials were subjected to a three cycle ammonia synthesis test under both conventional thermal heating and microwave heating. Microwave heating was found to outperform conventional heating for the first cycle on both Fe and CoMo materials. Principles of microwave catalysis and the heating of metallic particles may be generalized from this study; the dielectric loss tangent for optimum heating must fall within a realtively small range, similar to 0.8-1.4, and the penetration depth of the microwave into the particle must be considered and optimized for efficient heating, penetration depth should be on the same order as the particle size. The active phases of both catalysts, Fe4N and Co3Mo3N, were found to be responsive to microwave irradiation. Finally, the deactivation and regeneration of the materials was studied by examining the BET surface areas by reforming surfaces with a low concentration gas phase oxidation reaction. This study sheds light on more general principles of microwave catalysis and on the scale-up of CLAS reactions.

Automated summary

This study investigates the performance of chemical looping ammonia synthesis (CLAS) materials under traditional thermal heating and microwave heating, and finds that microwave heating outperforms traditional heating for Fe and CoMo materials. The study also generalizes the principles of microwave catalysis and the heating of metallic particles, and examines the deactivation and regeneration of the materials.