Behaviour of nickel–alumina spinel (NiAl2O4) catalysts for isooctane steam reforming

Abstract

The suitability of NiAl2O4-based catalysts for steam reforming of isooctane, which is used here as a surrogate for gasoline, was examined at moderate temperatures (600–700 °C) during a relatively prolonged time on stream (about 30 h). A series of catalysts with a varying nickel loading in the 10–33 wt.% range were prepared by co-precipitation. This synthesis route was shown to be adequate to produce nickel/alumina catalysts with a small Ni particle size (8–10 nm). The catalytic behaviour and the extent of the observed loss of conversion were mainly controlled by the available metallic surface area. Coke formation in the form of both amorphous and graphitic filamentous carbon was identified as the main reason for deactivation. Thus, the best catalytic results corresponded to a 17 wt.Ni% loading since it showed the lowest specific carbon deposition per surface area of metallic sites. At elevated reforming temperatures (650 and 700 °C) noticeably higher conversion values were obtained and the stability was enhanced, which suggested that coking did not induce a marked effect on the catalytic behaviour.