Production of carbon nanofibers from C2-C4 hydrocarbons over highly efficient NiSn catalysts prepared by mechanochemical alloying

Abstract

A series of nickel‑tin alloys was prepared by mechanochemical alloying of nickel and tin metal powders in a planetary mill. The evolution of morphology and phase composition of these alloys depending on the tin content and the duration of the alloying procedure was studied using X-ray diffraction analysis and scanning electron microscopy. The conditions providing the formation of Ni_1-xSn_x solid solutions based on the face-centered cubic lattice of nickel were determined. Based on the obtained results, the main stages of the mechanochemical alloying process have been proposed. The prepared nickel‑tin alloys were tested as catalysts for the production of carbon nanofibers via catalytic chemical vapor deposition of C2-C4 hydrocarbons at 650 °C. An optimal value of the mechanochemical alloying duration in terms of carbon yield was found to be 5 min. Another key factor affecting the catalytic performance is the tin content in the alloy composition. Thus, when tin was introduced in the amount of 0.5–3 at.%, the carbon yield after 30 min of reaction exceeded 120 g/g_cat. Moreover, the tin content also influences the morphology and the diameter of carbon nanofibers, as well as the character of their growth. Depending on the tin content, the carbon filament diameter can be varied in the range from 20 to 500 nm. All carbon materials synthesized using NiSn alloys possess a high specific surface area of ≥250 m²/g and a total pore volume > 0.4 cm³/g. Such textural characteristics make these materials attractive for use as sorbents or catalyst supports.