Ni-olivine

Crystal field parameters derived from the polarized absorption spectra of Mg-Ni olivines were expressed by the empirical equations (Hu et ah, 1990)... 

The interelectronic repulsion Racah B parameters were also derived from the crystal field spectra of Mg-Ni olivines. (Hu et al., 1990). The compositional variations given by... 

Variations of extinction coefficients and spectrum profiles with changes in chemical composition of a mineral provide information on cation ordering in the structure. Examples involving Al3+-Mn3+ ordering in epidotes and andalusites are discussed in 4.4.2 and 4.5, and Mn2+-Fe2+ ordering in olivine is illustrated in fig. 4.8. Compositional variations of intensities of absorption bands in polarized spectra of orthopyroxenes described in 5.5.4. (fig. 5.15) have yielded Fe2+/M2 site populations (Goldman and Rossman, 1979), while similar trends in the crystal field spectra of synthetic Mg-Ni olivines described in 5.4.2.4 (fig. 5.12) have yielded site occupancy ratios of Ni2+ ions in the olivineMl and M2 sites (Hu etal., 1990). 

Nord, A. G., Annersten, H. Filippidis, A. (1982) The cation distribution in synthetic Mg-Fe-Ni olivines. Amer. Mineral., 67,1206-11. 

SYNTHESIS OF OLIVINE (LiFeP04> and Ni/OLIVINE (LiFeP04) CATALYSTS FOR UPGRADING SYN-GAS PRODUCTION... 

Synthesis of Olivine (LiFeP04) and Ni/Olivine (LiFeP04) Catalysts... 

The Ni/olivine catalysts were prepared by wet impregnation of Phosphor olivine (LiFeP04) with an excess of nickel salt solution. The samples were calcined under air at 800°C for 2 hours and then reduced at 900°C. These different ways of preparation a series of Ni/olivine eatalysts were described in Table 1. 

Table II. Particle size, BET surface area, and element of olivine and Ni/olivine catalysts...

Swierczyhski, D., Libs, S., Courson, C. and Kiennemann, A. (2007) Steam reforming of tar from a biomass gasification process over Ni/olivine catalyst using toluene as a model compound. App/ierf Catalysis B, 27, 211-222. 

Influence of the preparation conditions of Ca doped Ni/olivine catalysts on the improvement of gas quality produced by biomass gasification... 

The Ni/olivine and Ni-CaO/olivine catalysts loaded with 4 wt.% nickel and calcium content between 0.0 and 3.7 wt.% Ca, were prepared by successive wet impregnations of olivine (at 20 or 60°C) using Ca(N03)2 4H20 and Ni(N03)2 6H20 precursors, dried over-night at 110°C and calcined for 4h after each impregnation. The calcination after... 

Table 1 summarised the gas phase distribution of reaction products obtained for Ni/olivine and Ni-CaO/ohvine (1.68 wt.%) catalysts using the CH4 C02 H2 C0 model feeding-mixture. It is observed that the calcium presence on Ni/olivine catalysts promotes the CH4 conversion and H2 production, but not affect the CO2 conversion significantly, reducing significantly the amount of gaseous impurities of the syngas. 

Table l.Gas phase distribution of reactor effluent for Ni/olivine and Ni-CaO/olivine catalysts. 

The impregnation method conditions of Ni and Ni-CaO supported olivine catalyst have great influence in the system and catalytic behaviour. The temperature of impregnation affects the interaction between the metal and the support, whereas the calcination temperature allows obtaining catalytic stable species. The parameters selection on physicochemical basis allow obtaining an active catalyst. The presence of small amounts of calcium in Ni/olivine catalysts improves the conversion of CH4 and the selectivity of H2 in the reaction, independently of die presence or absence of H2 and CO. 

A general feature is the fact that the insertion or deinsertion process for the 1aJ 4P04 (M = Fe, Co, Ni) olivine materials is a two-phase process at temperature... 

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