Characterization of solid carbon from hydrocarbon pyrolysis in molten aluminum

Abstract

This study analyzed the synthesized solid carbon from the pyrolysis of methane, ethane, propane, and natural gas using molten aluminum at 1000 °C. Microscopic examination revealed the formation of spherical structures and capped-carbon nanotubes with average primary particle sizes of 0.18–1.29 μm for the spheres and 0.31–0.39 μm for the capped-carbon nanotubes. Methane and ethane pyrolysis generated spherical carbon exclusively, while propane and natural gas pyrolysis produced spheres and capped-carbon nanotubes. The analysis of interlayer spacing indicated the presence of nanocrystalline properties in all carbon samples. X-ray diffraction analysis indicated broad graphitic phases in methane, ethane, and natural gas-derived carbon, and a broad and sharp graphitic carbon peak in propane-derived carbon. Raman spectroscopy confirmed the presence of graphitic structures and disorder, with capped-carbon nanotubes demonstrating more ordered structures than spheres. The thermogravimetric analysis uncovered differences in oxidation behavior, with the mixture of spherical carbon and capped-carbon nanotubes resulting from propane pyrolysis displaying superior thermal stability compared to samples composed solely of spherical carbon. Additionally, the solid carbon samples from the pyrolysis of methane, ethane, and natural gas displayed a final decomposition curve corresponding with commercial carbon black N991. The surface area analysis unveiled that carbon samples derived from ethane and natural gas exhibited surface areas that were 2.4–5.2 times larger than those of commercial carbon black N991 and graphite flakes. These findings underscore the adaptability of tailoring solid carbon materials by selecting the appropriate feed gas to suit specific applications.