Grafted NiO on natural olivine for dry reforming of methane
| Autor: | C. Courson, L. Udron, C. Petit, A. Kiennemann, Lin Liu |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Science and Technology of Advanced Materials. 3:271-282 |
| ISSN: | 1878-5514 1468-6996 |
| DOI: | 10.1016/s1468-6996(02)00026-8 |
| Popis: | 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)2SiO4 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 °C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 °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% H2. 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. |
| Databáze: | OpenAIRE |
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