Rh/Ce_0.25Zr_0.75O₂ Catalyst for Steam Reforming of Propane at Low Temperature

Abstract

Solid oxide fuel cells (SOFCs) show high energy-conversion efficiency and thus emit less CO 2 than conventional combustion engines. Although SOFCs can directly convert hydrocarbons such as liquefied petroleum gas, these fuels readily induce coking on the electrodes of fuel cell stacks. To avoid coking, hydrocarbons can be subjected to a preliminary endothermic steam-reforming step at a relatively low temperature using waste heat from the stack. Herein, we report that a Rh/ Ce 0.25 Zr 0.75 O 2 catalyst exhibited higher propane-steam-reforming activity than other Rh/Ce 1À x Zr x O 2 catalysts and Rh/γ-Al 2 O 3 . Catalyst characterization revealed that Rh/Ce 0.25 Zr 0.75 O 2 had excellent redox property and high H 2 O-adsorption activity, which contributed to the activation of steam and thus enhanced the propane-steam-reforming activity of this catalyst. Results and DiscussionThe temperature dependences of the catalytic activities of Rh/ Ce 1À x Zr x O 2 and Rh/γ-Al 2 O 3 are shown in Figure 1a. At 200°C, no propane consumption was observed over Rh/γ-Al 2 O 3 , and conversion was low over all the Rh/Ce 1À x Zr x O 2 catalysts. At 250°C, some of the propane was consumed, and the propaneconversion activities of the catalysts decreased in the order Rh/ Ce 0.25 Zr 0.75 O 2 > Rh/Ce 0.5 Zr 0.5 O 2 > Rh/Ce 0.75 Zr 0.25 O 2 > Rh/CeO 2 > Rh/ ZrO 2 > Rh/γ-Al 2 O 3 . At the target temperature for this study (300°C), Rh/Ce 0.25 Zr 0.75 O 2 showed the best activity: the propane conversion reached 55 %, which was 6 times that over Rh/γ-Al 2 O 3 . At 300°C, the catalyst activities for propane conversion decreased in the order Rh/Ce 0.25 Zr 0.75 O 2 > Rh/Ce 0.5 Zr 0.5 O 2 > Rh/ ZrO 2 > Rh/Ce 0.75 Zr 0.25 O 2 > Rh/CeO 2 (Figure 1b). At 350°C, propane conversion over Rh/Ce 0.25 Zr 0.75 O 2 and Rh/ZrO 2 reached 100 %, and the activities of the other catalysts decreased in the [a] L.

Support Effects on the Activity of Ni Catalysts for the Propane Steam Reforming Reaction

“…Moreover, the addition of manganese oxide on Ni/Al 2 O 3 was found to act as an oxygen donor that is transferred to Ni particles leading to rapid decomposition and oxidation of C 3 H 8 and CH 4 or C 2 H 4 that may be produced under reaction conditions, resulting in further H 2 production and improvement of the catalyst lifetime [ 9 ]. It has been also found that activation of steam followed by H 2 formation may be favored over metal catalysts supported on “reducible” metal oxides through generation of oxygen defects, resulting in improved propane steam reforming activity and resistance to coke formation [ 3 , 13 , 31 ]. Based on previous studies, the reducibility of the supports used in the present study is expected to vary significantly.…”

“…Supported noble metal (Rh, Ru, Pt, Pd) catalysts have been proposed to efficiently catalyze the production of H 2 via propane steam reforming exhibiting high resistance to coke formation [ 3 , 11 , 13 , 14 ]. However, the high cost and low availability of noble metals are major drawbacks restricting their use in practical applications [ 15 , 16 , 17 ].…”

Propane Steam Reforming over Catalysts Derived from Noble Metal (Ru, Rh)-Substituted LaNiO3 and La0.8Sr0.2NiO3 Perovskite Precursors

“…Consequently, research efforts currently focus on the development of novel catalytic systems, with improved resistance against coke deposition and metal particle agglomeration [21]. In this respect, noble metals such as Rh, Ru, Pt, and Ir have been studied either alone or in combination with Ni because of their lower tendency to form coke [14,[26][27][28][29][30]. The addition of promoters such as alkali metals in the form of oxides has also been shown to suppress coke deposition, but results in generally inferior catalytic activity [10,22].…”