Study On Co(Ni)/LaMnO₃ Catalysts For Steam Reforming Of Ethanol

Steam reforming of ethanol (SRE) is an attractive route for hydrogen production, in which the key technique is developing efficient and stable catalysts. The challenge for catalysts development is how to improve catalyst stability, because those catalysts for SRE are readily deactivated by carbon deposition or sintering of catalyst particles. Generally, carbon deposition can be depressed or even eliminated by decreasing particle sizes of active component or/and elevating activation ability of catalyst for active oxygen species. Perovskite type oxides with special structure characteristics are inclined to form oxygen vacancies that are effective active center for activation of oxygen species. On the other hand, interaction between cobalt (nickel) oxides and perovskite type oxides should be readily generated, because those cobalt (nickel) ions can be coordinated as the metal ions in perovskite structure. This interaction is favorable for decreasing particle size of active component of metal cobalt (nickel). Another important property of perovskite type oxides is its good stability for anti-sintering.Based on the ideas stated above, in this work, perovskite type oxide supported cobalt (nickel) catalysts Co(Ni)/LaMnO₃ were prepared and used for steam reforming of ethanol. The influences of preparation method, preparation conditions and content of cobalt (nickel) in catalysts and reaction conditions for SRE have been investigated.The main results are as follows:1. These catalysts show high activity and selectivity towards hydrogen for SRE. Conversion of ethanol was close to 100% over Co-based catalysts at 500℃and over Ni-based catalysts at 400℃;2. The single perovskite structure was formed with critic-complexing and impregnation method, and this catalyst showed high activity. The content of hydrogen in reacted gas was in the range of 67⁷5%, meanwhile, the content of methane kept at a low level of 1.5% over Co-based catalysts. The content of hydrogen in reacted gas was in the range of 64⁷4%, the content of methane kept at a low level of 1.1% over Ni-based catalysts;3. The effect of calcination temperature and content of cobalt(nickel) on catalytic performance was distinct and 15%Co/LaMnO₃-800 and 15%Ni/LaMnO₃-700 catalyst showed best catalytic performance among the catalysts tested respectively;4. The results of stability and TG-DTA indicates that 15%Co/LaMnO₃ and 15%Ni/LaMnO₃ catalyst has no carbon deposition under reaction temperature at 700℃and shows good stability for 7 hours'running, which should be due to its special structure and oxygen-storage ability.5. The result of TPR and XRD indicates that the catalyst was composed of LaCoO₃(NiO, LaNiO_2.7), LaMnO₃+δand LaMnxCo1-xO₃(LaMnxNi1-xO₃). The active component is Co0 or Ni0 reduced from LaCoO₃ or high dispersed NiO and LaNiO_2.7.