Multiscale carbon characterization obtained from methane pyrolysis in a pilot-scale molten metal reactor

Hydrogen can be produced by CH 4 pyrolysis without process-intrinsic CO 2 formation, but solid carbon must be valorized to avoid becoming waste. Unlike laboratory-scale products, pilot-scale molten-metal carbons remain scarcely characterized. Here we show that as-collected powder from a quasi-continuously operated molten-Sn pilot reactor is a heterogeneous C-Sn material with a turbostratic sp 2 framework. Combustion analysis measured 48.15 ± 0.26 wt.-% carbon. CO 2 -TGA left 54.77 ± 0.21 wt.-% recovered post-test residue, while SEM-EDX showed local Sn/O association in the fibrous and bottom residues without resolving Sn oxidation state or bulk composition. Raman spectroscopy, XRD and high-resolution electron microscopy reveal short, curved sp 2 layers without extended graphitic stacking. XRD positively identifies crystalline β-Sn, and SEM/STEM-EDX show Sn-rich features from micrometre to nanometre scales. The BET surface area is 11.88 ± 0.32 m 2 g −1 . These findings establish a multiscale pilot benchmark and identify quantitative bulk-metal analysis and controlled purification as necessary next steps.