Assessment of two atmospheric-pressure microwave plasma sources for H2 production from ethanol decomposition

H2 is considered as a sustainable fuel despite being obtained from other raw sources. Plasma technology can be used to produce it from alcohol decomposition as an excellent alternative technique to those habitually utilized. In the present study, two atmospheric-pressure microwave plasma sources, namely Torche a` Injection Axiale sur Guide d'Ondes (TIAGO) and surfatron, have been assessed for hydrogen production through ethanol decomposition, including for the first time both an analysis of the influence of operational conditions and energetic performance. Gaseous by-products are studied by Mass Spectrometry in a wide range of experimental conditions, focusing on the discharge capability to withstand and decompose ethanol and produce H2. Surfatron discharges exhibit a good capability to produce H2 with significant selectivity for low Ar flow rates, which is reduced for larger flow rates due to a decrease in the residence time of ethanol in the discharge. Besides, its capability to withstand the alcohol is limited due to the maximum power that can be applied to maintain the plasma. However, TIAGO torch plasmas surpass the performance of surfatron for H2 production, being able to withstand the introduction of larger ethanol flow rates. This fact allows for higher H2 production with higher selectivity, showing an almost complete (>99%) ethanol decomposition in a wide range of working conditions. Furthermore, the torch shows a better energetic performance than the surfatron for larger ethanol flows, providing with larger H2 production rates of 0.61 g kW-1h- 1 with relatively low specific energies required for ethanol processing (0.17 kWh g-1).