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Abstract
Water vapor plays a central role in plasma-assisted methane conversion for hydrogen production. As a reactant, it participates in methane steam reforming and the water–gas shift reaction. Its presence can also influence the formation of reactive species, the distribution of gaseous products, carbon deposition, and plasma discharge stability. However, these effects vary with the steam-to-methane ratio, reactor design, discharge power, gas temperature, residence time, and catalyst configuration.
This review examines published experimental and kinetic studies to assess how water vapor affects methane conversion and hydrogen production in plasma-assisted systems. The studies indicate that an adequate steam supply can suppress soot formation and maintain stable operation in certain microwave plasma reactors. Additional steam beyond the amount required for stability, however, does not necessarily increase hydrogen production or improve energy yield. In catalytic nonthermal plasma systems, changes in water feed and operating conditions can also alter CO and CO₂ selectivity.
The analysis shows that the effect of water vapor cannot be described by a single optimum applicable to all plasma reactors. Evaluating its contribution requires methane conversion to be considered alongside hydrogen yield, product composition, carbon formation, and energy consumption. Consistent measurement and reporting of these indicators are essential for comparing reactor systems and identifying operating conditions suitable for hydrogen production.
References
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