Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/γ-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 γ-Al2O3, CeO2, and ZrO2 were initially carried out at 700 °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/γ-Al2O3 was found to be higher than Rh/CeO2 and Rh/ZrO2, with H2 and (H2 + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/γ-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/γ-Al2O3, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/γ-Al2O3 with high stability from Rh/CeO2, Rh/CeO2/γ-Al2O3 catalysts with different CeO2 contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/γ-Al2O3, the newly prepared Rh/CeO2/γ-Al2O3 catalysts (0.5 wt% of Rh and 20 wt% of CeO2) showed even enhanced activity during 10 h, and H2 and (H2 + 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/γ-Al2O3 and Rh/CeO2/γ-Al2O3 catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/γ-Al2O3 catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO2/γ-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 H2 production for 100 h.