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

The activity-stability pattern of a 19 wt.% Ni/MgO catalyst in the pre-reforming (T,450degreesC;P, 10 bar) of n-hexane with steam (S/C, 1.5-3.5) in absence and presence of H-2 (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 + 2H(2)reversible arrowCH(4)) and gasification/water-gas-shift (GAS, C + H(2)Oreversible arrowH(2) + CO; WGS, CO + H(2)Oreversible arrowCO(2) + H-2) reactions, while negligible appears the contribution of the Bouduard reaction path (DISP, 2COreversible arrow2C + CO2). (C) 2004 Elsevier B.V. All rights reserved.