Bi-reforming of methane in a carbon deposit-free plasmatron with high operational adaptability

An atmospheric plasmatron reactor with two-stage inlets was developed for bi-reforming of methane (CO2/CH4/H2O) to produce syngas (H2 + CO) and value-added liquid products. The influence of CH4 inlet position, gas flow rate and reactant composition were investigated. The results showed that the two-stage-inlet design allows for a wide range of operational conditions in terms of the CO2/CH4/H2O ratio (2–7:0–6:0–3) and total flow rate (4.5-11 L/min). A CO2 and CH4 conversion of 24% and 12.9%, respectively, was obtained at flow rates of up to 7-8 L/min, with no observable carbon deposit formed. A closer injection of CH4 to the core plasma area was more beneficial for both reactant conversion and syngas selectivity. Interestingly, value-added oxygenated products (e.g., methanol, ethanol, acetic acid) were produced simultaneously, offering a promising power-to-liquid (PtL) route. In particular, the direct synthesis of acetic acid from CH4 and CO2 was achieved, which is infeasible in thermocatalytic processes. A small addition of H2O (14.3%) favorably enhanced the formation of acetic acid by up to 160%, likely due to the improved generation of CH3 and COOH intermediates. Overall, this work offers a promising route for syngas and oxygenated products generation in a scalable plasmatron reactor with high operational adaptability.