Morphology of Carbon Formed from High-Molecular Hydrocarbons on the Iron Group Metals Supported on the Carbon Material Sibunit

Abstract

The properties of iron group metals (Fe, Co, Ni) supported on mesoporous carbon Sibunit are studied regarding the carbon formation during catalytic pyrolysis of high-molecular alkanes (hexane, undecane, hexadecane). With the catalyst NiO/Sibunit, the rate of the carbon formation at 500–600 °C decreases in the series hexane > undecane > hexadecane. The carbon is deposited as carbon nanofibers. The series of the activity of the reduced catalyst to the carbon production is: 10%NiО/Sibunit > 10%CoO/Sibunit > 10%Fe₂О₃/Sibunit. The morphology of carbon produced over the 10%CoO/Sibunit catalyst depends on the metal particle dispersion: multilayer carbon nanotubes (MCNT) grow on 10–30 nm particles and carbon nanofibers on the particles larger than 30 nm in size. XRD studies of the Fe₂O₃/Sibunit catalyst after the reaction showed that the active component can be in the form of iron metal and iron carbide, the proportion of each phase being dependent on the dispersion of the active phase particles. The particles of 10–30 nm in size produce iron metal, and the larger particles give iron carbide. It is concluded that the iron carbide particles are responsible for the formation of carbon nanofibers and iron particles for the formation of MCNT.