Modelling the activity–stability pattern of Ni/MgO catalysts in the pre-reforming of n-hexane Original Research Article

The activity–stability pattern of a 19 wt.% Ni/MgO catalyst in the pre-reforming (T, 450 °C; P, 10 bar) of n-hexane with steam (S/C, 1.5–3.5) in absence and presence of H2 (H/C, 2) has been investigated. Deactivation profiles of the kinetics of CH4 and CO/CO2 formation indicate that the activity, selectivity and stability are closely related. Hydrogenation of carbon species to methane is a critical step involving the occurrence of coking in the pre-reforming of hexane. Thermodynamic analysis of the outlet reaction stream signals that the net coking rate depends upon the relative kinetics of carbon methanation (MET, C+2H2⇄CH4) and gasification/water–gas-shift (GAS, C+H2O⇄H2+CO; WGS, CO+H2O⇄CO2+H2) reactions, while negligible appears the contribution of the Bouduard reaction path (DISP, 2CO⇄C+CO2).