(379f) Outperformance of a Microwave-Heated Reactor over a Conventional Reactor in Steam and Sorption Enhanced Reforming of Ethanol over Ni-Silica-Aerogel Catalysts.

The use of microwave as an alternative energy source in solid-catalyzed reactions was shown to improve the catalyst performance and the thermal efficiency of the process significantly. Steam reforming (SRE) and sorption enhanced reforming of ethanol (SESRE) were investigated in the microwave and conventionally-heated reactors. Ni-impregnated (10%Ni) silica-aerogel catalysts (10Ni-SA) were synthesized, characterized, and tested in both SRE and SESRE. This material has a mesoporous pore structure with a surface area of 610 m²/g and a mean pore diameter of 9 nm. In the microwave-heated reactor, the catalyst was mixed with mesoporous carbon to enhance microwave absorption capacity of the bed.

Results proved highly stable performance of 10Ni-SA catalyst in SRE, giving almost complete ethanol conversion. Significantly higher hydrogen concentrations were obtained in the MW-heated reactor than the conventional one. While the product stream contained 61.7% H₂ at 500^oC in the conventional system, this value increased to 71.1% in the microwave-heated reactor. Hydrogen yield values achieved in the conventionally-heated system at 600^oC and the MW-heated system at 400^oC were about the same, indicating the outperformance of the MW-heated system at a much lower temperature. Another significant superiority of the MW reactor is the formation of much less CH₄ (2.6%), while the corresponding value was 15.1% (at 500^oC) in the product stream of the conventionally-heated system. Results also proved much less coke formation in the microwave-heated system. In the case of SESRE tests, almost complete removal of CO₂ and CO (by CaO mixed with catalyst), with a significant increase of hydrogen yield, was achieved in the MW reactor at 400^oC. Results proved that much higher hydrogen yields together with lower coke and methane formation could be achieved in the microwave-heated reactor than the conventionally-heated one, mainly due to the formation of instantaneous microplasmas and volumetric heating of the catalyst bed.