Catalytic H2O and CO2 reforming of CH4 over perovskite-based La0.8Sr0.2Cr0.9Ni0.1O3: Effects of pre-treatment and co-reactant/CH4 on its reforming characteristics

The H2O and CO2 reformings of CH4 over perovskite-based La0.8Sr0.2Cr0.9Ni0.1O3 prepared by precipitation, sol-gel and surfactant-assisted methods (calcined with air, nitrogen and hydrogen) were studied under solid oxide fuel cell (SOFC) conditions. It was found that the catalyst prepared by the surfactant-assisted method and calcined with hydrogen provided the highest specific surface area and reforming reactivity. Under typical conditions (H2O/CH4 and CO2/CH4 of 1.0), the reforming reactivity of La0.8Sr0.2Cr0.9Ni0.1O3 was comparable to that of Ni/Al2O3 but relatively less than that of precious-metal Rh/Al2O3. Nevertheless, at specific condition (H2O/CH4 and CO2/CH4 of 0.5-0.7), its activity dramatically increased to the same level as that of Rh/Al2O3. According to the study on the kinetic dependencies of La0.8Sr0.2Cr0.9Ni0.1O3, the reforming rate was proportional to CH4 partial pressure with the reaction order increased from 0.50 (at co-reactant/CH4 ratio of 1.0-3.0) to 0.95 (at co-reactant/CH4 ratio of 0.5). In addition, the rate was inhibited by H-2 addition at high inlet co-reactant/CH4 ratio; however the inhibitory effect becomes less pronounced at an inlet coreactant/CH4 ratio less than 0.7. It is suggested that one of two reforming mechanisms occurred depending on the operating conditions applied. La0.8Sr0.2Cr0.9Ni0.1O3 behaves like an oxide-based catalyst at high coreactant/CH4 ratio, whereas it tends to behave more like a metallic-based catalyst at low co-reactant/CH4 ratios resulting in the high reforming reactivity. The study has shown that high surface area perovskite-based La0.8Sr0.2Cr0.9Ni0.1O3 catalyst has great potential to be applied as a steam reforming catalyst since it requires low inlet steam content, which provides significant benefits in terms of minimizing the water management in reformer and SOFC systems. (C) 2010 Elsevier B.V. All rights reserved.