Magnetite syntheses

Schwertmann, U. Murad, E. (1990) The influence of aluminum on iron oxides. XIV. Al-substituted magnetite synthesized at ambient temperatures. Clays Clay Min. 38 196-202... 

Flc 9. Two-step reaction sequence for magnetite synthesis from the reaction of aqueous iron(II) with ferrihydrite. 

Fig. 11-1. Equipment for magnetite synthesis. 1 Drop funnel, 2 Thermometer, 3 Water bath, 4 Magnet, 5 Stirring and heating instrument, 6 Support for reaction vessel, 7 External beaker used as water bath, 8 Reaction vessel, 9 Plastic lid with inlet holes, 10 Pm-ge gas inlet.

Code sample Shell type Fe VFeS " Average diameter (nm) (DLS/AFM/SEM) Magnetite synthesis method Reference... 

HTS catalyst consists mainly of magnetite crystals stabilized using chromium oxide. Phosphoms, arsenic, and sulfur are poisons to the catalyst. Low reformer steam to carbon ratios give rise to conditions favoring the formation of iron carbides which catalyze the synthesis of hydrocarbons by the Fisher-Tropsch reaction. Modified iron and iron-free HTS catalysts have been developed to avoid these problems (49,50) and allow operation at steam to carbon ratios as low as 2.7. Kinetic and equiUbrium data for the water gas shift reaction are available in reference 51. 

Alkali-promoted Ru-based catalysts are expected to become the second generation NHs synthesis catalysts [1]. In 1992 the 600 ton/day Ocelot Ammonia Plant started to produce NH3 with promoted Ru catalysts supported on carbon based on the Kellogg Advanced Ammonia Process (KAAP) [2]. The Ru-based catalysts permit milder operating conditions compared with the magnetite-based systems, such as low synthesis pressure (70 -105 bars compared with 150 - 300 bars) and lower synthesis temperatures, while maintaining higher conversion than a conventional system [3]. 

Sun, S.H. and Zeng, H. (2002) Size-controlled synthesis of magnetite nanoparticles. Journal of the American Chemical Society, 124 (28), 8204—8205. 

Cai, W. and Wan, J.Q. (2007) Facile synthesis of superparamagnetic magnetite nanoparticles in liquid polyols. Journal of Colloid and Interface Science, 305 (2), 366-370. 

Zhao, S. and Asuha, S. (2010) One-pot synthesis of magnetite nanopowders and their magnetic properties. Powder Technology, 197 (3), 295-297. 

Lee, Y Lee, J., Bae, C.J., Park, J.G., Noh, H.J., Park, J.H. and Hyeon, T. (2005) Large-scale synthesis of uniform and crystalline magnetite nanoparticles using reverse micelles as nanoreactors under reflux conditions. Advanced Functional Materials, 15 (3), 503-509. 

Dang, F., Kamada, K., Enomoto, N., Hojo, J. and Enpuku, K. (2007) Sonochemical synthesis of the magnetite nanopartides in aqueous solution. Journal of the Ceramic Society of Japan, 115 (1348), 867-872. 

The retentive power of graphite towards adipic acid and the catalytic effect of the magnetite, especially present in A, are obvious. TEM examinations of a graphite A sample before and after reaction showed that crystallites of Fe304 appeared to be smaller after the reaction. However, the same graphite sample was reused for three successive reactions without significant loss in yield. When applied to the synthesis of other cyclic ketones (Scheme 7.14), less volatile than 74, it was observed that pressure had an effect on the recovery of product (Tab. 7.9, entries 3 and 4). A slightly reduced pressure (300 mm Hg) was necessary to obtain 3-methylcyclopentanone (75) or cyclohexanone (76) in convenient yield (Tab. 7.9, entries 4 and 5). For the cycliza-tion of suberic acid (73), a less favorable structure, the yield in cycloheptanone (77) remained low (Tab. 7.9, entry 6). 

Huff, G. A., Jr., and Satterfield, C. N. 1984. Intrinsic kinetics of the Fischer-Tropsch synthesis on a reduced fused-magnetite catalyst. Ind. Eng. Chem. Process Des. Dev. 23 696-705. 

The magnetite is considered to form from a ferrihydrite precursor by interaction of this phase with dissolved Fe" ions (Kirschvink Lowenstam, 1979 Lowenstam, 1981 Nesson Lowenstam, 1985). The same mechanism operates for inorganic synthesis at around pH 7 (see chap. 13). Most probably the other iron oxides in the teeth form by a similar mechanism, but under conditions of slightly lower pH and/ or higher redox potential. The separation of these minerals in time and space suggests local variations in growth conditions. 

Synthesis of microcrystalline hematite and magnetite in organic solvents and effect of a small amount of water in the solvents. 

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