The Investigation of Methane Pyrolysis and Its Carbon Products Utilizing Molten Metal/Molten Salt Composite Reactors

Methane pyrolysis for turquoise hydrogen production faces dual challenges of reactor clogging and carbon contamination, particularly the difficulty in extracting high-purity carbon from molten media. While most existing studies focus on two-phase systems, carbon products are inevitably contaminated by the medium. This work presents a novel dual-layer bubble column reactor (Cu0.45Bi0.55 alloy/NaCl salt) operating at 900–1100 °C. The system achieved continuous operation for over 72 h without clogging. Crucially, the selected NaCl salt offers distinct advantages: its low cost, non-toxicity and high water solubility facilitate effective carbon separation strategies. This configuration reduced metal contamination in carbon from 52.4 wt% to below 4.0 wt%, with post-treatment achieving ultralow metal content below 1.5 wt%. Moreover, the molten salt environment induced valuable structural modifications in the carbon. This work provides an economically viable process for co-producing clean hydrogen and high-value carbon, addressing key technical barriers in molten media reactors.