Methane pyrolysis rate measurement using electromagnetic levitation techniques for turquoise hydrogen production: Liquid In, Ga, Bi, Sn, and Cu as catalysts

•Experimental techniques and indices of pyrolysis assessment in literature were reviewed.•New experimental techniques (electromagnetic levitation) were employed to selectively measure the catalytic reaction rate.•Hydrogen generation rate on liquid In, Ga, Bi, Sn, and Cu were measured.•The catalytic forward rate constant per catalytic site was evaluated along with the first ionization energy. Turquoise hydrogen production is a promising technology because hydrocarbons are pyrolyzed into hydrogen and carbon without the generation of carbon dioxide. A high-temperature bubble column reactor with molten catalytic metal is suitable for this technology. However, the production efficiency of a reactor depends on various factors. A research methodology to assess the catalytic performance of molten metal catalysts is presented by employing an electromagnetic levitation technique. The catalytic reaction rate was selectively measured, which is independent of the motion of the bubbles in the bubble column reactor. Therefore, the proposed methodology is suitable for selecting an optimum molten-metal catalyst based on its catalytic properties. The hydrogen production rate per unit area of the molten metal catalyst (rH2) was measured for Bi, Cu, Ga, In, and Sn. The highest reaction rate above 1100 °C was obtained for Bi, while the highest reaction rate below 1000 °C was obtained for Ga. The reaction rate was inversely proportional to the first ionization energy of the metals. This study provides quantitative data on methane pyrolysis via in the presence of molten pure-metal catalysts using a reliable experimental technique.