Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/gamma-Al2O3-based mixed oxides on hydrogen production

Abstract

Autothermal reforming (ATR) of iso-octane in the presence of Rh-based catalysts (0.5 wt% of Rh) supported onto gamma-Al2O3, CeO2, and ZrO2 were initially carried out at 700 degrees C with a S/C ratio of 2.0, an O/C ratio of 0.84, and a gas hourly space velocity (GHSV) of 20,000 h(-1). The activity of Rh/gamma-Al2O3 was found to be higher than Rh/CeO2 and Rh/ZrO2, with H-2 and (H-2 + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/gamma-Al2O3 material, however, was potentially susceptible to carbon coking and produced 3.5 wt% of carbon deposits following the reforming reaction, as evidenced by C, H, N, and S elemental analysis. In contrast, Rh/CeO2 catalyst exhibited lower activity but higher stability than Rh/gamma-Al2O3, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/gamma-Al2O3 with high stability from Rh/CeO2, Rh/CeO2/gamma-Al2O3 catalysts with different CeO2 contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/gamma-Al2O3, the newly prepared Rh/CeO2/gamma-Al2O3 catalysts (0.5 wt% of Rh and 20 wt% of CeO2) showed even enhanced activity during 10 h, and H-2 and (H-2 + CO) yields were calculated to be 2.08 and 2.62 mol/mol C, respectively. In addition, as observed with Rh/CeO2, the catalyst was further found to be stable with less than 0.3 wt% of carbon deposition after 10 h. The Rh/gamma-Al2O3 and Rh/CeO2/gamma-Al2O3 catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/gamma-Al2O3 catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO2/gamma-Al2O3 catalyst proved to be excellent in terms of stability against coke formation as well as activity towards the desired reforming reaction, maintaining its ability for H-2 production for 100 h. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.