Ethylene epoxidation in microwave heated structured reactors

• An efficient MW dielectric heating of a monolithic structured reactor is demonstrated.
• Good selectivities and conversions to ethylene epoxide are achieved at temperatures below 275 °C.
• The formation of hot spots affects the selectivity of the ethylene epoxidation reaction under MW irradiation.
• MW induced temperature measurements are more reliable with a combined use of Fiber Optics and IR thermography.

In the present work we show the microwave-induced heating of monolithic reactors containing a thin-layered catalyst that exhibits a strong and selective heating susceptibility under microwave irradiation. The combination of microwave radiation and structured reactors has been successfully applied for the intensification of the selective oxidation of ethylene to ethylene oxide (epoxidation) while operating at lower power consumptions and with higher energy efficiencies than in conventional heating conditions. The microwave radiation selectively heats the catalyst and the monolith walls while maintaining a relatively colder gas stream thereby creating a gas/solid temperature gradient of up to ∼70 °C at a reaction temperature of 225 °C. Moreover, the influence of different parameters such as the distribution of the catalyst onto the structured monoliths or the temperature measurement techniques employed to determine the heating profiles (Optic Fibers and/or IR thermography) have been also thoroughly evaluated to justify the obtained catalytic results.

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