Mn/Ni/TiO2 Catalyst for the Production of Hydrogen and Carbon Nanotubes from Methane Decomposition

The decomposition of methane into carbon and hydrogen over 15 mol % MnO x /20 mol %NiO/TiO2 catalysts was investigated. The effects of catalyst synthesis and pretreatment of 15 mol % MnO x /20 mol % NiO/TiO2 catalysts for the activity and morphology of carbon from methane decomposition were identified, based on the parameters studied. The catalysts were characterized using X-ray diffractometry (XRD), temperature-programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption. The activity tests were performed at atmospheric pressure in a stainless-steel fixed-bed reactor at a temperature of 725 °C and gas hourly space velocity (GHSV) of 2700 h-1. The 15 mol % MnO x /20 mol % NiO/TiO2 catalyst that was prepared using the impregnation method without any pretreatment showed high activity for the methane decomposition reaction at 725 °C and GHSV = 2700 h-1. The regenerated samples showed no significant decrease in methane conversion after up to six cycles of decomposition and regeneration. The XRD patterns of the regenerated samples indicated that no apparent structural change occurred. Although different types of filamentous carbon formed on the various 15 mol % MnO x /20 mol % NiO/TiO2 catalysts prepared by different methods, an attractive carbon nanotube was observed in the case of the 15 mol % MnO x /20 mol % NiO/TiO2 catalyst prepared via the impregnation method and tested without any pretreatment.