Pathways of hydrogen-rich gas produced by microwave discharge in ethanol-water mixtures

The ethanol decomposition process for hydrogen-rich gas synthesis via microwave discharge in ethanol-water mixtures was investigated in this study. Excited active species and gas-phase products based on ethanol’s varying volume fraction were detected via optical emission spectroscopy (OES) and mass spectrometry (MS). The correlation between the spectrum signal of the active species and the mass spectrum signal of the gas phase products was quantitatively analyzed. The experimental results showed that the intermediate active species mainly consisted of OH, C2, CH2, CH, C, and H, and the gas phase products mainly included H2, CH4, C2H2, CO, C2H4, and CO2. There were significantly positive linear relationships between H or CH2 and H2, demonstrating that both H and CH2 were important radicals for generating H2. Based on the experimental results and analyzed from the perspective of thermodynamics, the reactions of H + H (+M) → H2 (+M) and H + H + H2→H2 + H2, H + H + H2O → H2 + H2O, CH2 + CH2→ H2 + C2H2 were all likely to produce hydrogen. •There were significantly positive linear relationships between H or CH2 and H2.•H and CH2 were important radicals for generating H2.•Possible reaction path of microwave discharge in ethanol solution was given.