Insights into the regeneration performance of Ni1-xMgxAl2O4 and Ni/MgAl2O4 catalysts in the ethanol steam reforming

A good regeneration capacity of the catalyst is key to progress on the scale-up of the ethanol steam reforming (ESR) process, for which the catalyst formulation plays a fundamental role. This work explores the performance of Ni-based catalysts obtained by reducing Ni 1-x Mg x Al 2 O 4 (prepared by coprecipitation, with x = 0, 0.3 and 0.5) and NiO/MgAl 2 O 4 (by wet impregnation) precursors in the ESR process operating under reaction-regeneration cycles. The precursors and catalysts were characterized by temperature programed reduction, X-ray diffraction and N 2 physisorption. The ESR reaction was performed at 500 °C and low space time to accelerate the deactivation, whereas the regeneration was carried out with air at 850 °C for 4 h. The catalysts derived from Ni 1-x Mg x Al 2 O 4 with low Mg content showed the highest activity in the first reaction with H 2 yields close to 40 %, but they were unable to recover their initial activity after being regenerated because they suffer severe particle fragmentation due to abundant filamentous carbon deposition, which hinders the complete recovery of the initial spinel structure. Instead, the catalysts derived from NiO/MgAl 2 O 4 showed a poor activity and stability in the first reaction, but interestingly their activity was improved after successive reaction-regeneration cycles tending to a reproducible performance that seems to be more rapid when calcined at 600 °C than at 850 °C. Consequently, the NiO/MgAl 2 O 4 catalyst calcined at 600 °C reached H 2 yields close to 30 % and kept a reproducible behavior from the second reaction cycle onwards. This phenomenon is associated with the formation of a reproducible Ni spinel phase during the regeneration process.