Methane dry reforming on Ni loaded hydroxyapatite and fluoroapatite
Methane dry reforming on Ni loaded hydroxyapatite and fluoroapatite
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DOI：
10.1016/j.apcata.2006.10.029
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发表时间：
2007-02-07
影响因子：
5.5
通讯作者：
Ziyad, Mahfoud
中科院分区：
文献类型：
--
作者：
Boukha, Zouhair;Kacimi, Mohamed;Ziyad, Mahfoud
合成了不同镍含量的钙-羟基磷灰石和钙-氟磷灰石，并用扫描电子显微镜、程序升温还原(TPR)、紫外-可见-近红外(UV-Vis-NIR)和X射线光电子能谱(XPS)等技术对其进行了表征。在这两个系列催化剂中发现了三种镍物种：(1)Ni2+离子与磷灰石骨架的钙离子交换；这种Ni2+/Ca~(2+)交换似乎仅限于低于1wt%Ni的镍负载量，(Ii)表现出与载体(对于x>；1wt%Ni)强烈相互作用的NiO小颗粒，以及(Iii)在高负载量下出现的大NiO颗粒。镍在这三个容矿地点之间的分布取决于磷灰石的性质。例如，Ni(1)/CaHAp催化剂中Ni2+离子的交换量是Ni(1)/CaFAP催化剂的两倍。在600℃时，甲烷转化率随着镍负载量的增加而增加，当镍负载量达到x=4时，活性接近热力学平衡(78%)，H-2/CO比接近1。催化剂活性随温度变化的研究证实了这一结果。催化剂上的积碳也随着镍负载量的增加而增加，但在4h后没有引起任何明显的活性衰退。所取得的令人鼓舞的结果归功于磷灰石的基本性质、它们对化学吸附二氧化碳的能力和负载镍的催化特性之间的协同作用。(C)2006爱思唯尔B.V.保留所有权利。
Calcium-hydroxyapatite and calcium-fluoroapatite loaded with different amounts of nickel were synthesized and characterized by several techniques including scanning electron microscopy, temperature programmed reduction (TPR), UV-visible-NIR and XPS spectroscopy. Three types of nickel species were detected in the two series of catalysts (i) Ni2+ ions exchanged with Ca2+ ions of the apatite framework. This Ni2+/Ca2+ exchange seems to be restricted to nickel loadings inferior to 1 wt% Ni, (ii) small particles of NiO exhibiting strong interactions with the carriers (for x > 1 wt% Ni) and (iii) large particles of NiO which appear at high loadings. The distribution of the nickel between these three hosting sites depends on the nature of the apatite. For instance the amount of exchanged Ni2+ ions in Ni(1)/CaHAp is twice more important than in Ni(1)/CaFAp.The Ni(x)/CaHAp and Ni(x)/CaFAp catalysts were tested in methane dry reforming with CO2. Methane conversion at 600 degrees C, increases with the nickel loading up to x = 4 where the activity is around the thermodynamic equilibrium (78%) and H-2/CO ratio close to 1. These results were confirmed by the investigation of the catalysts activity versus the temperature. Carbon deposition on the catalysts was found to also increase with nickel loading but without provoking any significant decay of the activity after 4 h on stream. The encouraging results achieved were attributed to the synergy between the basic properties of the apatites, their aptitude to chemisorb CO2 and the catalytic features of the supported nickel. (c) 2006 Elsevier B.V. All rights reserved.