Opposite effects of self-growth amorphous carbon and carbon nanotubes on the reforming of toluene with Ni/α-Al2O3 for hydrogen production

Ni-based catalysts are prone to be deactivated by carbon deposition . This study aims to investigate the influence mechanism of different types of carbon deposition on the activity of Ni/α-Al 2 O 3 catalyst at various steam-to-carbon (S/C) ratios during steam reforming of toluene for hydrogen production . At a low S/C ratio of 1, the catalytic activity of Ni/α-Al 2 O 3 was inhibited due to the covering and blocking of Ni active sites by the formation of amorphous carbon on the Ni surface . While at a high S/C ratio of 3, more than 80 wt% of carbon deposition was found to be self-growth carbon nanotubes (CNTs) with an average diameter of around 15 nm. The activity of Ni/α-Al 2 O 3 in steam reforming of toluene was unusually promoted, which can be attributed to the tip-growth mechanism of CNTs, whereby the Ni particles migrated to the tip or the surface of CNTs, resulting in the improved active site dispersion.