Synthesis, characterization and performance evaluation of Ni/Al2O3 catalysts for reforming of crude ethanol for hydrogen production

The effects of catalyst synthesis method (i.e. precipitation (PT), coprecipitation (CP) and impregnation (IM)), Ni loading and reduction temperature on the characteristics and performance of Ni/Al2O3 catalysts were evaluated for the reforming of crude ethanol for H2 production. The results showed that in the calcined PT catalysts, no NiAl2O4 species were observed whereas this was a major species in CP and IM catalysts. As a result, PT catalysts were more reducible than CP and IM catalysts. PT catalysts exhibited slightly lower crystallite sizes of NiO species than the corresponding CP catalysts. On the other hand, IM catalysts had extremely large crystallite sizes except IM10 (IM catalyst with 10% Ni loading) which had the smallest crystallite size. A combination of small crystallite size and high reducibility for PT catalysts resulted in higher crude ethanol conversions for the PT catalysts. In contrast, the IM catalysts with larger crystallite sizes and lower reducibility yielded the lowest crude ethanol conversions. Catalysts with 15% Ni loading gave the best crude ethanol conversions for each method of synthesis with PT15 giving the best overall crude ethanol conversion of 85 mol% again because of its smaller crystallite size and higher reducibility. In terms of H2 yield, CP15 was the optimum catalyst because of its higher H2 selectivity as compared to PT15 and IM15 catalysts. Coking was observed at the onset of the reaction but stabilized after 180 min TOS.