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Unformatted text preview: ully oxidised ones. Dissanayake et al. investigated an industrial Ni/Al steam reforming catalyst after CPOM
by means of XRD and XPS  and Basile et al. a hydrotalcite-type derived Ni/Mg/Al
catalyst after CPOM employing XRD and Scanning electron microscopy energy
dispersive spectroscopy (SEM-EDS) . Both authors found that Ni in the head of the
catalyst was completely oxidised and in the tail of the catalytic beds they both found Ni
only in the metallic state. However, they observed different Ni phases in the middle part
of the bed. Basile et al. observed NiO and Ni, whereas Dissanayake et al. observed
surface NiO on Al2O3, which they regarded to be catalytically more active than NiAl2O4
found in the Head, The low activity of NiAl2O4 was also reported by Choudhary et al.
[105, 106]. Dissanayake et al. also observed that the proportion of the 3 sections of the
catalyst bed (head, middle and tail) changed with the reaction temperature and also the
contact time. The amount of the tail (metallic Ni) decreases with decreasing reaction
temperature and also by decreasing contact time, whereas the head (NiAl2O4) and the
middle (NiO/Al2O3) increased. A catalyst consisting only of NiAl2O4 was the final result
of even further decrease of the temperature. The results show that the phase composition of the catalyst changes along the catalyst
bed due to the oxidative character of the reaction mixture. The authors linked this to the 1. Introduction 42 ytrtrghrhrhhrhrhhffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
decrease in the O2 due to its consumption by the formation of H2O and CO2. However,
they did not discuss the possibility that the oxidative character of the mixture may not
only be changed by reduction of the O2 content, but also by the simultaneous formation
of reducing CO and H2 (direct syngas formation, pyrolysis mechanism and parallel
pathway). 18.104.22.168. Influence of the reaction conditions Dissanayake et al. investigated their Ni catalyst a...
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