Methane conversion to hydrogen and nanotubes on Pt/Ni catalysts supported over spinel MgAl2O4.

Abstract

Methane decomposition is an endothermic process. Therefore a high temperature increases the methane conversion and improves the carbon accumulation. Nevertheless at high temperature conditions a faster deactivation of catalyst is generally observed. To keep the stability of the catalyst, lower reaction temperatures can be used as well as methane dilution but the catalytic activity is lowered. The aim of the present work consists in the study of the catalytic properties of Ni–Pt supported over MgAl2O4 for the selective conversion of methane into hydrogen and carbon nanotubes. The addition of a small amount of Pt to a nickel–MgAl2O4 catalyst promotes the formation of carbon nanotubes with a significant selectivity to MWCNT. The interest of using a bimetallic (Pt–Ni) catalyst is to favour the reduction of the Ni precursor (and the formation of small nickel particles). For the catalyst that we prepared methane is mainly transformed into structured MWCNTs if the reduction is complete while graphitization is observed over partially reduced catalysts. A fine characterization of the catalyst surface after each step of the preparation and use is currently under investigation in order to progress in the relationships between the surface composition and the CNTs formation.