Grafted NiO on natural olivine for dry reforming of methane
Grafted NiO on natural olivine for dry reforming of methane
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DOI：
10.1016/s1468-6996(02)00026-8
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发表时间：
2002-06-01
影响因子：
5.5
通讯作者：
Kiennemann, A.
中科院分区：
文献类型：
--
作者：
Courson, C.;Udron, L.;Kiennemann, A.
天然橄榄石用于在流态化床中气化生物质。X-射线衍射仪和电子显微镜(扫描电子显微镜和电子显微镜)的表征表明，样品中存在(Mg，Fe)(2)SiO4结构(Mg/Fe比为9/1)，元素组成分布较广。程序升温还原同样揭示了这种结构之外的氧化铁的存在。可以通过提高焙烧温度来改变游离氧化铁的性质，也可以通过磁性测量来证实。在天然橄榄石上引入氧化镍是通过硝酸盐浸渍得到的。氧化镍与橄榄石的相互作用类型因制备方法和焙烧温度的不同而不同。对于1100℃焙烧，研究了NiO含量和浸渍次数的影响。在高温焙烧(1400℃)时，NiO被整合到橄榄石结构中，游离铁的数量增加。橄榄石上的NiO是不可还原的，导致催化剂失活。在较低的焙烧温度下，生成了接枝的NiO，这是一种在催化试验条件下被还原而没有粒子聚集的物种。一次浸渍镍(NiO的5.5wt%)可以得到稳定的催化剂，直接在反应条件(CH4+CO2)下活化，生成96%的CO和76%的H-2。NiO含量较低或镍盐二次浸渍的催化剂稳定性较差。分析表明，在测试条件下，橄榄石结构和镍沉积物的大小没有变化。同样，这些催化剂上也没有形成碳沉积。提出了不同制备方法下各催化体系的演化模型。观察到的催化剂失活归因于游离铁含量的增加，这有利于催化体系的氧化性能。(C)2002爱思唯尔科学有限公司。保留所有权利。
Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)(2)SiO4 structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism. The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 degrees C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 degrees C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH4 + CO2) yielding 96% CO and 76% H-2. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system.Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system. (C) 2002 Elsevier Science Ltd. All rights reserved.