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首页> 外文会议>International conference on fuel cell science, engineering, and technology;FuelCell2010 >NI-CO-ZN-AL CATALYSTS FROM HYDROTALCITE-LIKE PRECURSORS FOR HYDROGEN PRODUCTION BY ETHANOL STEAM REFORMING
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NI-CO-ZN-AL CATALYSTS FROM HYDROTALCITE-LIKE PRECURSORS FOR HYDROGEN PRODUCTION BY ETHANOL STEAM REFORMING

机译：类似于水滑石前体的Ni-CO-ZN-AL催化剂，用于通过乙醇蒸汽重整制氢

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A series of well crystallized Ni-Co-Zn-Al LDHs materials has been prepared by the urea hydrolysis method as precursors of mixed oxide catalysts for the Ethanol Steam Reforming (ESR) reaction. The calcination of the layered precursors gives rise to high surface area mixed oxides, mainly a mixture of rock-salt phase (NiO), wurtzite phase (ZnO) and spinel phase. Both precursors and mixed oxides have been throughtfully characterized and the steam reforming of ethanol has been investigated over the calcined catalysts in flow reactor and in-situ FT-IR experiments. The data here reported provide evidence of the good catalytic activity of Co-Zn-Al and Co-Ni-Zn-Al catalysts prepared from hydrotalcite-like LHD precursors for ethanol steam reforming. At 823 K the most active Co/Ni catalyst containains a predominant spinel phase with composition near Zn_(0.58)Ni_(0.42)[Al_(0.44)Co_(0.56)]_2O_4 and small amounts of NiO and ZnO.On the other side, at 873 K the selectivity to hydrogen increases with cobalt content. In particular, the presence of cobalt increases selectivity to H_2 and CO_2 and decreases selectivity to methane in the low temperature range 720-870 K. The most selective catalyst is the Ni-free Co-Zn-Al mixed oxide essentially constituted by a single spinel type phaseCobalt catalysts appear consequently to behave better than nickel based catalysts in this temperature range. The key feature for high selectivity to hydrogen is proposed to be associated to a stability of a relatively high oxidation state at the catalyst surface, the most relevant selectivity determining step being constituted by the evolution of surface acetate species. In fact, over oxidized catalyst surface the acetate species evolveproducing carbon dioxide and hydrogen while over a more reduced surface they evolve giving rise to methane and CO_X. Water is supposed to have the main role of allowing surface sites to stay in an unreduced state at least in the temperature range 720-870 K.
机译：通过尿素水解法已经制备了一系列结晶良好的Ni-Co-Zn-Al LDHs材料，作为乙醇蒸汽重整（ESR）反应的混合氧化物催化剂的前体。层状前体的煅烧产生高表面积的混合氧化物，主要是岩盐相（NiO），纤锌矿相（ZnO）和尖晶石相的混合物。对前驱物和混合氧化物都进行了全面的表征，并在流动反​​应器和原位FT-IR实验中对煅烧的催化剂进行了乙醇蒸汽重整的研究。此处报道的数据提供了从类似水滑石的LHD前驱体制备的用于乙醇蒸汽重整的Co-Zn-Al和Co-Ni-Zn-Al催化剂良好的催化活性的证据。在823 K时，活性最高的Co / Ni催化剂包含一个主要的尖晶石相，其组成接近Zn_（0.58）Ni_（0.42）[Al_（0.44）Co_（0.56）] _ 2O_4和少量的NiO和ZnO。 另一方面，在873 K时，氢的选择性随钴含量的增加而增加。尤其是，钴的存在会在720-870 K的低温范围内增加对H_2和CO_2的选择性，并降低对甲烷的选择性。最具选择性的催化剂是基本上由单个尖晶石构成的无镍Co-Zn-Al混合氧化物类型阶段 因此，在该温度范围内，钴催化剂表现出比镍基催化剂更好的性能。提出了对氢的高选择性的关键特征与催化剂表面上较高氧化态的稳定性有关，最相关的选择性决定步骤是由表面乙酸盐类的析出构成的。实际上，在氧化的催化剂表面上，乙酸盐会释放出来 会产生二氧化碳和氢气，而在更小的表面上它们会释放出甲烷和CO_X。假定水的主要作用是使表面部位至少在720-870 K的温度范围内保持未还原状态。

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