Synthesis, characterisation and performance evaluation of spinel-derived Ni/Al2O3 catalysts for various methane reforming reactions

The catalytic performance of bulk nickel aluminate catalysts synthesised by co-precipitation (NiAl 2 O 4 -CP) and co-dissolution (NiAl 2 O 4 -D) was examined for various methane reforming reactions, namely partial oxidation, steam reforming and oxidative steam reforming. The calcined and reduced spinels were thoroughly characterised by a wide number of analytical techniques including WDXRF , N 2 physisorption, XRD, UV–visible–NIR DRS, XPS, TEM, H 2 -TPR and NH 3 -TPD. The characterisation results of the calcined samples at 850 °C showed that nickel aluminate phase was mainly obtained on the NiAl 2 O 4 -CP near-surface together with a small NiO excess. By contrast, a large amount of NiO phase was formed on NiAl 2 O 4 -D and deposited on the spinel surface. The reduction at 850 °C of the two samples produced monodispersed Ni particles (10.6 nm) in the NiAl 2 O 4 -CP while larger metallic nickel (17.7 nm) was deposited on the NiAl 2 O 4 -D. In the three investigated reforming reactions the NiAl 2 O 4 -CP catalyst proved to be highly active, stable and resistant toward carbon deposition. Moreover, the performances of the NiAl 2 O 4 -CP catalyst appeared to be generally comparable with that of a commercial 1%Rh/Al 2 O 3 catalyst. The difference in catalytic behaviour between the two nickel aluminates was related to the Ni dispersion, its particle size and its capacity to minimise the acid character of the alumina by covering a large part of its surface.