Decomposition of ethanol over Ni/Al2O3 catalysts to produce hydrogen and carbon nanostructured materials

γ-Alumina-supported 10, 20 and 33 wt.% nickel catalysts were prepared and used to investigate the decomposition of ethanol to hydrogen and carbon materials at 500 and 700 °C. It was verified that the ethanol conversion was complete for all nickel loadings at 500 and 700 °C. A low nickel loading (10 and 20%) favored the formation of the very stable spinel phase NiAl2O4, which has low activity in the production of solid carbon. The maximum hydrogen and carbon production was obtained using a nickel loading of 33%: more than 6 g of solid carbon per gram of catalyst (gC/gcat) was produced at 700 °C and 22.2 gC/gcat when the reaction was performed at 500 °C. At 500 °C, nanofibers were mainly formed, while at 700 °C the production of multiwalled nanotubes was favored. The selectivity in terms of the gaseous products was dependent on the nickel loading and temperature used. At high temperature the partial thermal decomposition of ethanol was favored leading, mainly, to the production of hydrogen, methane, and carbon monoxide. At 500 °C, there was the production of ethylene on the Al2O3 surface with low nickel loading. With high nickel loading (33%) ethanol decomposition to hydrogen and nanostructured carbon was favored

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► 10, 20, 33 wt.% Ni/Al2O3 for the decomposition of ethanol to H2 and carbon materials.
► Spinel phase NiAl2O4 formed with low nickel loading: 10, 20%.
► Maximum hydrogen and carbon production with 33 wt.% Ni/Al2O3.
► At 500 °C: nanofibers mainly formed, at 700 °C: production of MWCNTs favored.